Anesthesia for the Obese Patient

14/1/2016

Anesthesi a for the obese pati ent

Official Official repr reprint int from from UpToDate UpToDate ® www.uptodate.com ©2016 UpToDate ®

Anesthesia for the obese patient Author Author Rom Ro man Schumann, MD

Section Editor Stephanie B Jones, MD

Deputy Editor Marianna Crowley, MD Crowley, MD

All topics are are upd updated ated as new new ev evidence becomes available and our peer review process is process is complete. Literature review current through: Dec 2015. 2015. | | This topic last updated: Jan 08, 2016. INTRODUCTION — INTRODUCTION — As the prevalence of obesity increases worldwide, an increasing number of obese surgical patients will require anesthesia. Obesity is typically d efi efined by body mass index (BMI), the ratio of weight (in kilograms) to the square of height (in meters) ( calculator 1). 1). In adu adullts, the World Health Organization and the 2 National Institute of He Health defin define e obesity obesity as a BMI ≥30 ≥30 kg/m . This topic reviews the changes in anatomy and phys iology in obese patients that affect anesthetic management, anesthetic drug dosing in obesity, and planning the anesthetic (type of anesthesia, equipment, appropriate monitoring, and analgesic pl an) as it differs from patients with normal BMI. Preoperative medical evaluation of obese patients, the impact of obstructive sleep apnea on anesthetic management, and general principles and techniques in anesthesia are discussed separately. ● (See "Preanesthesia medical evaluation of the obese patient" .) ● (See "Surgical risk and the preoperative evaluation and management of adults with obstructive sleep apnea".) apnea" .) ● (See "Intraopera "Intraoperative tive management management of adults with obstruct obstructiv ive e sleep s leep apnea" apnea" .) ● (See "P "Postoperative ostoperative management management of adults wit h obstructive sleep apnea" .) ● (See "O "Overview verview of anesthesia and anesthetic choices" .) PHYSIOLOGIC PHYSIOLOGIC CHANGES — CHANGES — Increasing obesity leads to respiratory and cardiovascular changes that impact the delivery of of anesthesia and perioperative analgesia. Alterations Alterations in airw airway ay anato anatomy my caused caused by by obesity obesity are are discussed discussed separ separate ately. ly. (See "Preanesthesia medical evaluation of the obese patient", section on 'Airway assessment' .) Respiratory physiology — physiology — Obesity-related respiratory changes occur as a consequence of physical impingement of lung volumes and chest movement as well as the increased metabolic requirements of excess tissue; these in turn lead to increased work of breathing [ 1], increased oxygen (O2) consumption consumption [ 2], and disordered ventilation to perfusion matchin g [3 [3]. As a consequ consequen ence, ce, respira respiratory tory rates rates are are increa increased sed,, and function functional al residua residuall capacity capacity (FRC) (FRC) and and expira expiratory tory reserve volume (ERV) are decreased, even in mild obesity [ 4]. FRC may be sufficiently reduced such that small airways and alveoli remain closed during spontaneous vent ilation, leading t o ventilation-perfusion mismatch and right to right to left shunting [ 5]. Lung ]. Lung volumes volumes and intrapulmonary intrapulmonary shunt shunt worsen with the induction i nduction of general anesthesia anesthesia in in all patients, but to a much a much greater greater degree in obes e patients [6 [ 6,7 ,7]. ]. Supine position and obstructive sleep apnea (OSA) increase the magnitude of these effects [ 8,9 8,9]. ]. Consequences of these changes of co ncern to anesthesiolo anest hesiologists gists include: ● Decreased time to desaturation during apnea [ 10 10]] ● Increased Increased O2 requirem requirements ents [2 [ 2] ● Hypoventilation with supine spontaneous ventilation [ 9] A gene genera rall discussion of respira respiratory tory chang changes es in obe obesity sity is foun found d separ separately. ately. (See (See "Diseases of the chest wall", section secti on on 'Obe 'Obesit sity' y'.) .) Cardiovascular physiology — physiology — Cardiovascular physiologic changes in obesity include: ● Increased circulating blood volume, although it is a lower proportion of total weight (50 mL/kg as compared http://w http://www ww.up .uptod todate ate.com .com/cont /content ents/ane s/anesthesia-for-the-obe sthesia-for-the-obese-patien se-patient?to t?topicKey picKey=ANEST%2F1493 =ANEST%2F14932&e 2&elapsed lapsedTimeMs=1&source=search_result&searchTerm… TimeMs=1&source=search_result&searchTerm…

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with 75 mL/kg) compared with patients with normal BMI [ 11 11]. ]. ● Decreased Decreased systemic syst emic vascular vascular resistance resis tance [ 12 12]. ]. ● Increased cardiac output by 20 to 30 mL per kilogram of excess body fat. Stroke index, cardiac index, and heart rate remain normal; the increased cardiac output occurs by means of expanded stroke volume [ 13 13]. ]. ● Left ventricular hypertrophy, related to the duration of obesity [ 14 14]. ]. The increased cardiac output can lead to either left ventricular failure (especially when associated with hypertension), or right heart failure (especially when associated with the hypoxia and hypercapnia of OSA) ( algorithm 1). 1). Hypertension and cardiovascular disease are also more prevalent in obese patients and when present may produce additional changes (table ( table 1). 1). (See "Obesity, weight reduction, and cardiovascular disease", section on 'Obesity and cardiovascular disease' and disease' and "Preanesthesia medical evaluation of the obese patient", section on 'Screening for comorbidities'.) comorbidities' .) DOSING ANESTHETIC DRUGS — DRUGS — Drug dosing in obese patients may be based on total body weight (TBW), lean body weight (LBW) (calculator ( calculator 2) 2) for females and (calculator ( calculator 3) 3) for males, or ideal body weight (IBW) (calculator 4), 4), depending upon the agent chosen [ 15,16 15,16]. ]. Dosing methods for commonly used drugs are presented in the table (table ( table 2). 2). When recommended dosing method for a specific drug is unknown, it is reasonable to base doses on LBW, except for highly lipophilic drugs for which TBW should be used [ 17 17]. ]. Modified drug dosing is required because of obesity-related increases in LBW, cardiac output, and blood volume, as well as changes in regional blood flow; these can affect peak plasma concentration, clearance, and elimination half-life of many drugs [ 17 17]. ]. ● The The volume volume of distribution dist ribution (V d) is the principal determinant of loading dose of drugs. The The V d of relatively relatively lipophilic lipophilic drugs drugs is increased increased by obesity obesity;; less lipophilic lipophilic drugs drugs have have little littl e to no change change in V d in obese obese patients, as blood flow to fat tissue is lower than that to vessel-rich or lean tissue [ 18 18]. ]. Vd is larg large ely dependent on the physiochemical attributes of a drug and varies with plasma protein binding and tissue blood flow, but changes are not consistent for all drugs within a category, and in many cases have not been determined [ 17 17]. ]. ● Drug clearance is generally higher in obese individuals than non-obese individuals [ 17 17]. ]. This is largely controlled by hepatic and renal physiology. Obesity affects hepatic metabolic pathways in different ways, with some only slightly sl ightly and and others others signif s ignificantly icantly enhanced enhanced in obesity obesity [ 18 18]. ]. Renal elimination includes glomerular filtration, tubular secretion, and tubular reabsorption; changes are observed in obesity, but vary by drug and are not completely understood. ● The eliminatio elimination n half half-lif -life e (t (t 1/2) impacts impacts dosing dosing inter interv val and and dosing dosing of of continu continuou ous s infusion infusions. s. The The t 1/2 of a dru drug g varies directly directl y with V d, and inversely inversely on the clearance, both of of which which are altered altered in obesit obesity. y. While somewhat difficult to predict, pharmacodynamic changes also occur in severely obese individuals; for example, therapeutic windows may be narrowed or side-effects exaggerated in some drugs. PLANNING THE ANESTHETIC — ANESTHETIC — General anesthesia, regional anesthetic and sedation techniques have all been employed safely in obese patients, and no technique has been found to be superior to another with respect respect to impor i mportant tant patient outcomes (eg, (eg, mortality, cardiopulmo cardiopulmonar nary y complications). Due to the high prevalence of sleep apnea in obese patients, and consequent sensitivity to sedatives, the use of long-acting respiratory depressants should be minimized in obese patients regardless of technique chosen. Choice of anesthetic — anesthetic — Avoidance of general anesthesia is often considered in obese patients (particularly those with obstructive sleep apnea [OSA]) to avoid the potential for airway and respiratory problems, when other anesthetic techniques are feasible [ 19-21 19-21]. ]. Neuroaxial anesthesia and peripheral nerve blocks offer the advantages of improved postoperative pain control, limited use of opioids for postoperative analgesia, and decreased potential for drug-induced respiratory depression. Postoperative pain management with epidural infusions mitigates respiratory dysfunction in obese individuals, compared with systemic opioids, although it has not been shown to result in clinically improved http://w http://www ww.up .uptod todate ate.com .com/cont /content ents/ane s/anesthesia-for-the-obe sthesia-for-the-obese-patien se-patient?to t?topicKey picKey=ANEST%2F1493 =ANEST%2F14932&e 2&elapsed lapsedTimeMs=1&source=search_result&searchTerm… TimeMs=1&source=search_result&searchTerm…

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outcomes [22,23]. However, the following factors may lead to a choice of general anesthesia with assisted or controlled ventilation: ● Surgical procedure – Many surgical procedures can only be performed under general anesthesia (eg, thoracotomy, laparoscopy, spine surgery). ● Positioning – Obese patients have decreased respiratory tolerance for supine or head-down positioning, and may require ventilatory assistance or airway control in these positions. Obese patients may also be uncomfortable in the prone position due to pressure on the abdomen, and may require more sedation to tolerate this discomfort. ● Relaxation – Spontaneous breathing in patients with prominent abdominal obesity may interfere with an immobile abdominal or pelvic surgical field; these patients may require controlled ventilation under general anesthesia, with either an endotracheal tube (ETT) or supraglottic airway designed for controlled ventilation (eg, Proseal LMA). ● Anticipated difficult mask ventilation or intubation – If airway difficulty is anticipated, it may be prudent to intubate in a controlled manner at the beginning of the case, rather than after problems develop. (See 'Intubation' below and "Preanesthesia medical evaluation of the obese patient", section on 'Airway assessment'.) ● Increased risk of hypoventilation/hypercapnia – Hypercapnia may be especially problematic in patients with pulmonary hypertension due to OSA or obesity hypoventilation syndrome. ● Anxiety – Anxious obese patients may not be good candidates to remain awake during procedures, as anxiolytics and sedatives can lead to hypoventilation and/or airway compromise. ● Redundant tissue – This may lead to technical difficulty with placement of local, regional, or neuraxial anesthesia, although this can usually be overcome with appropriate equipment (eg, long needles) and ultrasound guidance [24-26]. Patient positioning — The improperly positioned obese surgical patient can experience physiologic impairment such as decreased ventilation, and even physical injury, including nerve injury and rhabdomyolysis. Risks of developing rhabdomyolysis after bariatric surgery include male gender, elevated BMI, and prolonged operating time [27]. Advantages and disadvantages of different positions include: ● Supine or head-down (Trendelenburg) positions – Decreased lung volumes and increased work of breathing (caused by the weight of the intra-abdominal contents on the diaphragm), and increased venous blood return (leading to increased cardiac output) occur when compared with the head-up (reverse Trendelenburg) or sitting positions; this leads to more rapid oxygen desaturation during apneic periods, increased pulmonary shunt, hypoventilation with spontaneous breathing, and edema of the head and neck after lengthy periods [ 28]. ● Head-up position (reverse Trendelenburg, or semi-sitting/”semi-Fowler ”) – Patients with their heads elevated are easier to mask ventilate, and there is a better view of the airway during direct laryngoscopy compared with those in the supine position ( figure 1). (See "Emergency airway management in the morbidly obese patient", section on 'Positioning' .) When supports are added to the bed to raise the upper trunk, it is important to provide sufficient support to the arms in order to maintain the shoulders in a neutral position. When the entire bed is tilted, care must be taken to prevent the patient sliding down the bed, especially if arms are secured to fixed arm supports; use of a foot plate may be helpful. ● Prone – Obese patients who are properly positioned prone for procedures may have improved respiratory function, with increased FRC, lung compliance, and oxygenation in anesthetized patients compared to supine position [29]. (See "Prone ventilation".) Patient supports should be placed under the chest and pelvis rather than the abdomen (which should be http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTerm…

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compression-free) to avoid increasing intra-abdominal pressure [ 30]. In selected cases, patients have been intubated awake, and then allowed to comfortably position themselves prone, prior to the induction of anesthesia; this eliminates the need for operating room personnel to turn and position the patient, and allows identification of pressure points by the patient before injury occurs [ 31,32]. ● Lateral decubitus – The lateral position removes the weight of the abdomen from the diaphragm, and increases the diameter of the pharyngeal airway [ 33]. The lateral decubitus position combined with head and upper body elevation may be helpful during recovery from general anesthesia, unless contraindicated due to the nature of the surgery. Axillary rolls used during lateral positioning may need to be larger than is standard. It can be challenging to support the head in a neutral position, as the neck is often short and wide; extra pieces of foam and rolled towels can be helpful. Standard bean-bags may be too narrow to support obese patients, so alternatives should be sought to maintain the patient in lateral position. Use of gel-pads may prevent injury to pressure points such as the hip. ● Lithotomy position – Lithotomy position decreases lung volumes by shifting abdominal contents towards the diaphragm, which may contribute to hypoxia and hypoventilation. Correct positioning and adequate padding of the legs is critical; neurologic injury or compartment syndrome may result from prolonged pressure [34,35]. Specially designed leg holders may be necessary to accommodate the size and weight of the legs. Beds and equipment used to support obese patients must be constructed to support the additional weight and must provide sufficient space to avoid pressure from side-rails. Carefully padding pressure points will help to prevent pressure-related peripheral nerve injuries. Positioning of the obese patient should be checked regularly during the maintenance phase of general anesthesia, as large patients are prone to shift position when the operating table is tilted, and may need to be repositioned. The use of Velcro to attach the mattress to the bed can help prevent slipping. Special equipment needs — The ability to safely anesthetize severely obese patients may require additional equipment that is not typically available. These include: ● Special equipment for positioning, as discussed above. ● Large beds and operating tables – Designated weight limits may not remain valid if the patient is shifted on the table, or the table is unlocked [ 36]. Additional arm supports to widen the table, or the use of two operating tables, may be necessary. ● Mechanical transfer mechanisms – Various means of mechanically assisting the transfer of severely obese patients between stretchers and beds have been developed. These may improve patient safety and prevent injury to care personnel. ● Additional personnel – Assistance may be needed to transfer and position patients safely. ● Extra-long needles – Normal length epidural, spinal, and nerve block needles may be insufficient to access structures in severely obese patients. ● Ultrasound – Ultrasound may be used to assist in vascular access, nerve block, and neuraxial procedures [37,38]. (See "Overview of peripheral nerve blocks", section on 'Ultrasound guidance' .) ● Blood pressure cuffs – Appropriately-sized blood pressure cuffs for noninvasive blood pressure (NIBP) result in accurate readings. The conical shape of the upper arm in many obese patients makes it difficult to place a standard NIBP cuff, so alternative NIBP cuff locations (eg, forearm or lower leg) are commonly used, although no studies confirm accuracy [ 16]. (See "Blood pressure measurement in the diagnosis and management of hypertension in adults", section on 'Cuff size' and "Blood pressure measurement in the diagnosis and management of hypertension in adults", section on 'Alternative sites for measurement' .) MANAGEMENT OF PAIN AND ANXIETY — A multimodal approach to analgesia to minimize the use of opioids is reasonable to decrease the risk of respiratory complications. One approach is to use potent nonsteroidal http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTerm…

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antiinflammatory analgesics (NSAIDs) such as ketorolac, along with local anesthetic wound infiltration [ 16,3941]. The addition of acetaminophen to this regimen can be considered (an intravenous formulation is available in many countries including the United States). This medication reduces postoperative opioid use and may have an intrinsic antiemetic effect [ 42,43], but it has not been specifically investigated in the obese population. Other agents that may be used to augment analgesia include ketamine, alpha-2 agonists (eg, clonidine and dexmedetomidine), and antiepileptic drugs (pregabalin and gabapentin); these may reduce the need for intraoperative and postoperative opioids, although the optimal regimen has not been determined in obese patients [44,45]. In a few small trials, obese patients who received alpha-2 agonists (preoperative oral clonidine, or intraoperative intravenous dexmedetomidine infusion) had lower opioid use than patients who did not, and in some cases had decreased need for antiemetic drugs and shorter post-anesthesia care unit stays [ 46-49]. Perioperative pregabalin and gabapentin have been associated with decreased use of postoperative opioids and decreased opioid-related side effects, but increased side effects related to the study drug [ 50-52]; however, these have not been studied specifically in obese patients. General considerations for the management of postoperative pain and aspects of analgesic management specific to patients with OSA are discussed separately. (See "Management of acute perioperative pain" and "Postoperative management of adults with obstructive sleep apnea", section on 'Pain control' .) The increased risk and consequences of respiratory depression in obese patients indicate caution in the use of opioids, sedatives (eg, propofol), and anxiolytic medications (eg, benzodiazepines). Incremental boluses, at lower doses than typically used, allow titration to desired effect without excessive side-effects. When sedation is offered to obese patients, they should understand that the sedation level may be light. MANAGEMENT OF NEURAXIAL ANESTHESIA — In general, neuraxial anesthetic techniques with local anesthetic (ie, without opioids) minimally affect respiratory drive, and are safe and appropriate choices for obese patients. Spinal and epidural anesthesia at higher dermatomal levels (ie, thoracic levels) may lead to respiratory difficulty; in one study, the onset of spinal anesthesia decreased spirometric lung volumes, to a greater extent in more severely obese patients [ 53]. Neuraxial medication should be given incrementally whenever possible, to avoid excessively high blockade; the same dose of spinal and epidural local anesthetics can spread to higher levels in obese compared with normal weight patients [ 54-56]. When planning a neuraxial technique at higher levels, it is prudent to use a technique that allows control of the amount and interval of dosing, such as an epidural or spinal catheter, rather than a “single shot” block. Although landmarks tend to be more difficult to identify in obese patients and a greater number of attempts are required to place spinal and epidural anesthetics, the success rate of placement in obese individuals is equivalent to that in normal weight patients [ 24-26]. MANAGEMENT OF GENERAL ANESTHESIA — Modifications of the approach to general anesthesia in obese patients center largely on respiratory issues. Obese patients have a higher incidence of hypoxia and respiratory events than patients with normal BMI [ 57,58]. Because these patients desaturate more quickly during apneic periods, the anticipation and management of respiratory problems is critical. Premedication of the obese patient should ideally allow anxiolysis without abolishing airway reflexes or preventing patient cooperation prior to induction of general anesthesia. We agree with the practice guidelines of the American Society of Anesthesiologists that do not recommend routine use of pharmacologic medication to decrease aspiration risk in patients without an increased risk of aspiration [ 59]. Morbid obesity did not correlate with gastroesophageal reflux in a study of 250 patients [ 60], and there is no evidence that aspiration risk is increased in obesity. Obese patients who are at increased risk of aspiration are managed in the same manner as non-obese patients. Airway management — Obese patients are more likely to require intubation rather than a supraglottic airway (eg, laryngeal mask airway [LMA]). One reason is that obese patients are more likely to require controlled ventilation to prevent hypoventilation during spontaneous respiration, and during positive-pressure ventilation, an LMA may not maintain a seal at the higher airway pressures needed in obese patients. Obesity-specific criteria for the use of a supraglottic airway have not been established. However, we consider factors including extent and distribution of obesity, type of surgery, length of surgery, and patient position to determine when its use is appropriate; in patients with BMI over 40, primarily abdominal obesity, abdominal/thoracic surgery, duration over http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTerm…

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two hours, and planned head-down positioning, we prefer to control ventilation with an endotracheal tube. Obese patients are seldom managed with mask ventilation alone; face mask ventilation can be technically challenging in the obese patient, and thus is generally restricted to extremely brief anesthetics (eg, an exam under anesthesia, or knee manipulation). Intubation may be more challenging in obese patients. Airway assessment is discussed in detail separately. (See "Preanesthesia medical evaluation of the obese patient", section on 'Predictors of airway difficulty' and "Airway management for induction of general anesthesia", section on 'Prediction of the difficult airway' .) Awake intubation is prudent when there is concern for both difficult intubation (previous difficult intubation, BMI >40, male gender [61]) and difficult mask ventilation (obesity, age >55 years, history of snoring, lack of teeth, presence of a beard, BMI >40, abnormal mandibular protrusion test [ 62]). (See "Management of the difficult airway for general anesthesia", section on 'Airway Approach Algorithm' and "Management of the difficult airway for general anesthesia", section on 'Awake intubation' .) There is less time to rescue the obese patient in a failed airway situation (cannot ventilate, cannot intubate) due to rapid apneic desaturation, so devices for difficult intubation (a “difficult intubation cart”) ( table 3), medications, equipment to topically anesthetize the airway, and expert assistance should be readily available for any patient having general anesthesia. (See "Management of the difficult airway for general anesthesia", section on 'Preparation for difficult airway management'.) Preparation for induction — Pre-oxygenation is ideally performed in the sitting or head-up (reverse Trendelenburg) position to maintain oxygenation, as both the supine position and the induction of anesthesia decrease lung volumes in the obese patient [ 63,64]. A head-up or ramped position also improves laryngoscopic view [65,66]. The bed can be tilted (or a stack of blankets or pre-formed ramp can be used) to elevate the patient’s upper body and head with the goal of horizontal alignment between the external auditory meatus and the sternal notch (figure 1). Preoxygenation should be performed via a tight-fitting facemask using 100 percent oxygen (O 2) at a flow rate high enough to prevent rebreathing (10 to 12 L/min), aiming for an end-tidal concentration of O 2greater than 90 percent in order to maximize safe apnea time. Patients should be preoxygenated with either three minutes of tidal volume breathing or eight vital-capacity breaths over 60 seconds. These two techniques have been shown to be equally effective at preventing desaturation and are more effective than four vital-capacity breaths over 30 seconds [67-69] Pre-oxygenation with manually-applied positive end-expiratory pressure (PEEP), or the use of noninvasive ventilation (NIV), will improve oxygenation in obese patients who will tolerate it. For example, in a trial of 30 patients with BMI >35 kg/m 2, pre-oxygenation with PEEP of 10 cm H 2O during induction increased the nonhypoxic apneic period by 50 percent (from 127 to 188 seconds) [ 70]. In other trials, application of NIV with PEEP prior to induction resulted in higher oxygen levels than spontaneous breathing of 100 percent oxygen [71,72]. The use of nasal cannula for passive apneic oxygenation during laryngoscopy can prolong the time to desaturation in high-risk patients during airway management [ 73-75] We suggest the administration of oxygen by nasal cannula at 10 L in addition to facemask oxygen in those patients who are at high risk for difficult laryngoscopy and intubation. When high concentration oxygen is used during induction of anesthesia, resorption atelectasis may occur, particularly in obese patients [ 76-78]. Use of a recruitment maneuver and prompt application of positive end expiratory pressure after intubation may prevent or reverse resorption atelectasis. (See 'Ventilation management' below.) Induction — When using a neuromuscular blocking agent (NMB) for airway placement, it is reasonable to choose a rapid acting one (eg, succinylcholine or rocuronium) to decrease the interval between induction and intubation, during which the patient must either be mask ventilated or be apneic. Obesity increases difficulty with mask ventilation and decreases the apneic period until desaturation occurs. (See "Preanesthesia medical evaluation of the obese patient", section on 'Airway assessment' and 'Respiratory physiology' above.) http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTerm…

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LMA use — The use and safety of supraglottic airway devices in this population has remained a matter of debate. When chosen, however, second-generation devices designed for controlled ventilation, which allow for higher seal pressures and provide a gastric vent, are frequently employed [ 79]. There are no specific technical considerations due to obesity for the placement of these devices. Intubation — Unless rapid sequence intubation is being performed, patients should be mask ventilated between induction and intubation. An LMA may be used to ventilate the patient prior to intubation, if mask ventilation is difficult. Mask ventilation should be carried out expertly with optimal positioning, early use of an oral airway, and a double-handed approach when needed. Intubation technique in obese patients is discussed separately. (See "Management of the difficult airway for general anesthesia".) Extubation — The head-up position is ideal at emergence, to improve oxygenation and decrease work of breathing. The obese patient should only be extubated in the operating room when fully awake and after any neuromuscular blockade has been completely reversed, in addition to standard extubation criteria. Neuromuscular blockade may be reversed using either sugammadex or neostigmine. Sugammadex is a slightly lipophilic reversal agent for steroidal non-depolarizing neuromuscular blockers, used particularly with rocuronium. In a trial of obese patients receiving sugammadex 2 mg/kg versus neostigmine 0.05 mg/kg, (both given according to IBW + 40 percent), the sugammadex group had a significantly faster recovery from NMB (2.7 versus 9.6 minutes) and a significantly better train-of-four (TOF) ratio in the recovery room (110 versus 85 percent) [80]. Anecdotal evidence suggests that sugammadex may offer additional benefits over neostigmine in certain clinical circumstances including fatty liver disease and recurarization of the obese [ 81,82]. There is limited information regarding dose adjustments of neostigmine for the obese. Although some authors advocate sugammadex dosing based on TBW in the obese, in a dose finding study (100 obese patients at a train-of-four [TOF] recovery between 1 and 2) sugammadex 2 mg/kg IBW resulted in adequate reversal, with no residual neuromuscular blockade. However, reversal was achieved more quickly at a dose adjusted to IBW + 40 percent, slightly above LBW [ 83]. Ventilation management — When patients are managed with spontaneous respiration (either with an LMA or an endotracheal tube), minute ventilation and end-tidal CO 2 should be closely monitored to assure adequate ventilation. We use continuous positive airway pressure (CPAP) during spontaneous respiration to improve oxygenation. When patients are unable to maintain sufficient volumes, ventilation should be assisted or controlled. The addition of pressure support assistance to PEEP may result in adequate ventilation; otherwise, ventilation should be controlled with either pressure or volume control. When obese patients are managed with controlled ventilation, a protective ventilation strategy is reasonable to maintain oxygenation and normocapnia, and to avoid lung damage, based on the available evidence and expert opinion, including this author [ 84,85]. This consists of low tidal volumes (TV), low levels of oxygen (as tolerated), positive end-expiratory pressure (PEEP), and recruitment maneuvers (RM) (see "Overview of mechanical ventilation", section on 'Settings' and "Mechanical ventilation of adults in acute respiratory distress syndrome", section on 'Recruitment maneuvers'): ● Set tidal volume of 6 to 8 mL/kg IBW ( calculator 4) ● Adjust respiratory rate to maintain normocapnia (permissive hypercapnia is acceptable in patients without pulmonary hypertension) ● Keep FIO2 below 0.5 to 0.8, to prevent resorption atelectasis and oxygen toxicity ● Use RMs repeatedly during anesthesia (6 to 20 seconds duration; plateau pressure 40 to 55 cm H 2O) ● Institute PEEP 10 to 15 cm H 2O following RMs ● Maintain head-up (reverse Trendelenburg) position, whenever feasible Although there are no trials which include all the elements of this protective ventilation strategy in obese patients, we recommend protective ventilation based on evidence in non-obese patients, and the effectiveness of elements of this strategy in obese patients: http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTerm…

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● In a trial of 400 non-obese adults having major abdominal surgery, patients were randomized to lung protective ventilation (TV 6 to 8 mL/kg IBW, PEEP 6 to 8 cm H 2O, RM after intubation and every 30 min) or traditional ventilator settings (TV 10 to 12 mL/kg IBW, no PEEP, no RM); both groups had oxygen level <50 percent, as tolerated [ 86]. Protective ventilation led to: • Decreased incidence of major pulmonary and extrapulmonary complications in the first week (10.5 versus 27.5 percent, relative risk [RR] 0.40 [95% CI 0.24-0.68]) • Lower incidence of acute respiratory failure requiring noninvasive ventilation or intubation (5.0 versus 17.0 percent, RR 0.29 [95% CI 0.14-0.61]) • Shorter median hospital stay (11 versus 13 days, between-group difference 2.45 days [95% CI 0.724.17 days]) ● In a 2012 meta-analysis of studies of ventilation strategies (pressure- or volume-controlled ventilation, tidal volumes, PEEP or RMs) in obese patients (BMI >30 kg/m 2), RMs added to PEEP improved intraoperative oxygenation and compliance, compared with PEEP alone; there was no increase in adverse effects and no difference between pressure-controlled and volume-controlled ventilation [ 87]. ● PEEP of 15 cm H2O is effective in maintaining functional residual capacity and improving oxygenation during laparoscopic surgery in morbidly obese patients [ 88,89]. Higher levels of PEEP can induce hypotension due to decreased venous return; increased fluid administration or vasopressors may be needed to maintain blood pressure [ 88,90,91]. Recruitment maneuvers should not be performed unless patients are hemodynamically stable and euvolemic, as they may lead to a transient decrease in preload. Anesthetic agents — The choice of anesthetic agent in obesity should be based on patient-specific clinical factors, rather than the presence of obesity. Induction agents — Choice of induction agent is not different in obesity. However, it is reasonable to use a neuromuscular blocking agent (NMB) with a rapid onset (eg, succinylcholine or rocuronium) to decrease the interval between induction and intubation, during which the patient must either be mask ventilated or be apneic and at risk for hypoxia. (See "Preanesthesia medical evaluation of the obese patient", section on 'Airway assessment' and 'Respiratory physiology' above.) Dosing of these agents may require modification in obese patients ( table 2). (See 'Dosing anesthetic drugs' above.) Maintenance agents — Anesthesia can be maintained with either an inhaled anesthetic agent (eg, isoflurane, sevoflurane, desflurane, with or without nitrous oxide) or with an intravenous agent (most often propofol). A limited number of studies have compared these agents in severely obese patients with inconsistent results, and no clear clinical superiority of one over the other. Slightly more rapid emergence and recovery occurred in patients with desflurane compared with sevoflurane, isoflurane or propofol in some trials [ 92-94], but in other trials there were no differences in recovery or other outcomes [ 95-98]. In a study of morbidly obese adult patients, the end-tidal sevoflurane concentration required to maintain 50 percent of patients at a bispectral index (BIS) of <50 was 1.6 percent [ 99], higher than that reported in a separate study of non-obese adults (0.97 percent) [100]. While nitrous oxide (N2O) may be used to supplement a volatile agent or propofol, some obese patients with underlying respiratory problems may not tolerate the decreased inspired oxygen concentration that accompanies the use of N2O. Concern that rapid diffusion of N 2O into the bowel obscures the view of the surgical field was not confirmed in a study of obese patients undergoing laparoscopic bariatric surgery; surgeons were unable to determine which patients had received N 2O and which had not [ 101]. Fluid management — There is very little evidence addressing perioperative fluid management specifically in obese patients, and euvolemia in this population is poorly defined; consequently clinical judgment based upon available measures of volume status and tissue perfusion remains the most important factor. (See "Intraoperative fluid management" .) http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTerm…

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The use of dynamic indices to guide intravascular fluid administration has not been studied in obese patients; however, in a prospective study of 50 bariatric surgery patients with mean BMI over 50 kg/cm 2, fluid therapy guided by stroke volume variation (derived from arterial pressure waveform analysis) maintained all hemodynamic parameters within 10 percent of baseline values [ 102]. (See "Intraoperative fluid management", section on 'Monitoring volume status' .) POST-ANESTHESIA CARE UNIT MANAGEMENT — Issues specific to the obese patient in the postanesthesia care unit (PACU) are largely respiratory and ventilatory. General care in the PACU, issues specific to patients with obstructive sleep apnea (OSA), and postoperative care of the critically ill obese patient are discussed elsewhere. (See "Overview of complications occurring in the post-anesthesia care unit" and "Postoperative management of adults with obstructive sleep apnea" and "Bariatric surgery: Intensive care unit management of the complicated postoperative patient" .) Extubation — Some obese patients may be slow to emerge from anesthesia and should remain intubated until they are awake and meet standard extubation criteria. Avoiding premature extubation is particularly important in the obese patient, as swelling and edema can further complicate an already challenging intubation. Emergency airway equipment (table 3) and personnel to assist in airway management must be available to manage potential difficulties. (See "Management of the difficult airway for general anesthesia", section on 'Extubation' .) Monitoring — Patients should have continuous pulse oximetry in the PACU until they have demonstrated that they can maintain adequate oxygenation when left unstimulated. If patients do not meet this standard when otherwise ready to be discharged from the PACU, pulse oximetry monitoring should continue when transferred to the hospital ward. Patients who cannot maintain adequate oxygenation when left undisturbed should not be discharged from the hospital. An arterial blood gas measurement is the best assessment for suspected hypoventilation, such as in patients who are unable to maintain acceptable oxygen saturation despite supplementation, possibly with a sustained decrease in level of consciousness. (See "Arterial blood gases".) Oxygenation — Postoperative obese patients have relative hypoxia compared with non-obese patients due to changes in physiology. (See 'Respiratory physiology' above.) Following extubation the following measures are used to maintain adequate oxygenation: ● Administration of oxygen, titrated to keep O 2 at >90 percent (by face mask or nasal cannula) ● Positioning patient in head-up (sitting or semi-sitting) or lateral position (if surgically acceptable) ● Use of incentive spirometry or chest physiotherapy The postoperative use of incentive spirometry or chest physiotherapy improves pulmonary function and decreases complications. For example, in a trial of obese patients (BMI 30 to 40 kg/cm 2) having minor surgery under general anesthesia, decreased postoperative complications resulted from either incentive spirometry (OR 0.44 [95% CI 0.18-0.99]) or coughing every 10 to 15 minutes for the first two hours after extubation (OR 0.43 [95% CI 0.27-0.63]), compared with no breathing exercises [ 103]. ● Administration of continuous positive airway pressure (CPAP) or noninvasive ventilation (NIV) in patients with preoperative use, or with hypoxia unresponsive to incentive spirometry The use of NIV following abdominal surgery in normal weight patients, compared with standard oxygen therapy, reduces the incidence of reintubation and severe complications [ 104]; it is reasonable to think that obese patients benefit as well. In a trial of morbidly obese patients with OSA, immediate application of NIV after extubation, compared with CPAP 30 minutes later, significantly improved forced vital capacity at the first postoperative day [ 105]. The use of NIV is feasible in patients with no previous experience with NIV, when applied by a trained respiratory therapist [ 106]. Despite concern that aspiration of air during CPAP treatment might cause disruption of fresh anastomotic suture lines following intestinal surgery, studies of gastric bypass patients receiving CPAP in the postanesthesia care unit have not shown an increased risk for anastomotic leak [ 107,108]. Following gastrointestinal surgery such as gastric bypass, we prefer early joint decision between anesthesiologist, http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTerm…

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surgeon, respiratory technician, and nurse to determine CPAP use in selected patients, emphasizing the team concept for the perioperative care of these patients [ 16]. Ventilation — Although adequacy of ventilation is not routinely measured in the PACU, a high level of suspicion for hypoventilation should be maintained in patients who remain sedated or become hypoxic despite administration of oxygen. Hypoventilation due to sedative medication should be ruled out; pharmacologic reversal of benzodiazepines or opioids may be used as clinically indicated. Often simply arousing a drowsy patient with a reminder to breath deeply is sufficient; but this may need to be repeated frequently. When upper airway obstruction is present, an oropharyngeal airway (if the patient is sedated), a nasopharyngeal airway, or both, may open the airway and permit adequate ventilation. When these maneuvers are insufficient, it is reasonable to assist these patients with NIV, which may keep them from requiring re-intubation. (See "Noninvasive positive pressure ventilation in acute respiratory failure in adults" .) Discharge criteria — There is very little objective evidence in the literature to guide clinical decision-making regarding duration of postoperative monitoring in morbidly obese patients. We agree with following standard considerations for the discharge of surgical patients, such as those published by the American Society of Anesthesiologists (ASA) [109]. Prior to transfer of the patient to an unmonitored setting, oxygen saturation on room air should return to preoperative baseline, and when left undisturbed the patient should not develop clinical hypoxemia or airway obstruction [ 110]. We extend use of these recommendations to all severely obese patients, with a low threshold for prolonged recovery room monitoring based upon the individual patient’s course. The decision to discharge obese patients with diagnosed or likely OSA should take into account the ability to use CPAP, the need for opioid medication, and comorbid medical conditions [ 111]. Postoperative management of OSA is discussed elsewhere. (See "Postoperative management of adults with obstructive sleep apnea" .) SUMMARY AND RECOMMENDATIONS ● Respiratory physiologic changes in obese patients include an increase in oxygen consumption and a decreased functional residual capacity, leading to a rapid decrease in oxygen saturation during apneic periods. Increased blood volume, decreased systemic vascular resistance, and increased cardiac output may lead to either left or right heart failure or both. (See 'Physiologic changes' above.) ● Drug doses in obese patients depend on the pharmacokinetic and pharmacodynamic parameters of the specific drug (table 2); when specific recommendations are not available, it is reasonable to base drug doses on lean body weight, ( calculator 2) for females and (calculator 3) for males. (See 'Dosing anesthetic drugs' above.) ● Although no anesthetic technique has been found to be superior to another with respect to important patient outcomes (eg, mortality, cardiopulmonary complications), when suitable to the clinical setting, general anesthesia is often avoided to minimize airway and drug-related respiratory problems. However, general anesthesia may be necessary for certain surgical procedures, when relaxation is required or when hypoventilation is a concern. No specific induction or maintenance agent has been shown to result in improved clinical outcomes when compared with others. (See 'Choice of anesthetic' above and 'Anesthetic agents' above.) ● Regardless of anesthetic technique, opioid administration should be minimized to decrease the risk of respiratory depression, particularly in patients with obstructive sleep apnea. In severely obese patients, pain control with opioid-sparing multimodal analgesia may reduce the risk of respiratory depression and other opioid-related side effects. This may include the use of local or regional anesthesia, nonsteroidal antiinflammatory drugs, alpha-2 agonists, and other medications. (See 'Management of pain and anxiety' above.) ● When general anesthesia is used in obese patients, we recommend adequate pre-oxygenation (with continuous positive airway pressure [CPAP] if tolerated) and induction in a head-up (reversed Trendelenburg) position to improve oxygenation and tolerance for apneic periods without desaturation (Grade 1B). Mask ventilation is more difficult and intubation may be more challenging in obese patients. http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTer…

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When difficulty with both is anticipated, it may be prudent to perform awake intubation. Equipment and skilled personnel to assist with a difficult or failed airway should be readily available. (See 'Airway management' above.) ● When obese patients are managed with controlled ventilation, we suggest using a protective ventilation strategy to maintain oxygenation and normocapnia ( Grade 2C) (see 'Ventilation management' above): • Set tidal volume of 6 to 8 mL/kg ideal body weight ( calculator 4) • Adjust respiratory rate to maintain normocapnia (permissive hypercapnia is acceptable in patients without pulmonary hypertension) • Keep FIO2 below 0.5 to 0.8, to prevent resorption atelectasis and oxygen toxicity • Use recruitment maneuvers repeatedly during anesthesia (6 to 20 second duration; plateau pressure 40 to 55 cm H2O) • Institute positive end-expiratory pressure (PEEP) 10 to 15 cm H 2O following recruitment maneuvers (RMs) • Maintain head-up (reverse Trendelenburg) position, whenever feasible ● Postoperative oxygenation should be monitored until patients can maintain adequate oxygenation when left unstimulated. A reasonable approach to hypoxia and hypoventilation is to maintain a head-up position with oxygen by face mask and encouragement to breathe deeply, followed by a trial of CPAP or noninvasive ventilation (NIV), with reintubation for the refractory patient. ● Prior to transfer to an unmonitored setting, oxygen saturation on room air should return to preoperative baseline, and when left undisturbed, the patient should not develop clinical hypoxemia or airway obstruction. (See 'Discharge criteria' above.) Use of UpToDate is subject to the Subscription and License Agreement . REFERENCES 1. Ladosky W, Botelho MA, Albuquerque JP Jr. Chest mechanics in morbidly obese non-hypoventilated patients. Respir Med 2001; 95:281. 2. Kabon B, Nagele A, Reddy D, et al. Obesity decreases perioperative tissue oxygenation. Anesthesiology 2004; 100:274. 3. Littleton SW. Impact of obesity on respiratory function. Respirology 2012; 17:43. 4. Jones RL, Nzekwu MM. The effects of body mass index on lung volumes. Chest 2006; 130:827. 5. Adams JP, Murphy PG. Obesity in anaesthesia and intensive care. Br J Anaesth 2000; 85:91. 6. Damia G, Mascheroni D, Croci M, Tarenzi L. Perioperative changes in functional residual capacity in morbidly obese patients. Br J Anaesth 1988; 60:574. 7. Söderberg M, Thomson D, White T. Respiration, circulation and anaesthetic management in obesity. Investigation before and after jejunoileal bypass. Acta Anaesthesiol Scand 1977; 21:55. 8. Lin CC, Wu KM, Chou CS, Liaw SF. Oral airway resistance during wakefulness in eucapnic and hypercapnic sleep apnea syndrome. Respir Physiol Neurobiol 2004; 139:215. 9. Lee MY, Lin CC, Shen SY, et al. Work of breathing in eucapnic and hypercapnic sleep apnea syndrome. Respiration 2009; 77:146. 10. Jense HG, Dubin SA, Silverstein PI, O'Leary-Escolas U. Effect of obesity on safe duration of apnea in anesthetized humans. Anesth Analg 1991; 72:89. 11. Backman L, Freyschuss U, Hallberg D, Melcher A. Cardiovascular function in extreme obesity. Acta Med Scand 1973; 193:437. 12. Alpert MA, Hashimi MW. Obesity and the heart. Am J Med Sci 1993; 306:117. http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTer…

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13. Lavie CJ, Messerli FH. Cardiovascular adaptation to obesity and hypertension. Chest 1986; 90:275. 14. Nakajima T, Fujioka S, Tokunaga K, et al. Noninvasive study of left ventricular performance in obese patients: influence of duration of obesity. Circulation 1985; 71:481. 15. Schumann R, Jones SB, Ortiz VE, et al. Best practice recommendations for anesthetic perioperative care and pain management in weight loss surgery. Obes Res 2005; 13:254. 16. Schumann R, Jones SB, Cooper B, et al. Update on best practice recommendations for anesthetic perioperative care and pain management in weight loss surgery, 2004-2007. Obesity (Silver Spring) 2009; 17:889. 17. Hanley MJ, Abernethy DR, Greenblatt DJ. Effect of obesity on the pharmacokinetics of drugs in humans. Clin Pharmacokinet 2010; 49:71. 18. Blouin RA, Warren GW. Pharmacokinetic considerations in obesity. J Pharm Sci 1999; 88:1. 19. Hall JC, Tarala RA, Hall JL, Mander J. A multivariate analysis of the risk of pulmonary complications after laparotomy. Chest 1991; 99:923. 20. Healy LA, Ryan AM, Gopinath B, et al. Impact of obesity on outcomes in the management of localized adenocarcinoma of the esophagus and esophagogastric junction. J Thorac Cardiovasc Surg 2007; 134:1284. 21. Wigfield CH, Lindsey JD, Muñoz A, et al. Is extreme obesity a risk factor for cardiac surgery? An analysis of patients with a BMI > or = 40. Eur J Cardiothorac Surg 2006; 29:434. 22. von Ungern-Sternberg BS, Regli A, Reber A, Schneider MC. Effect of obesity and thoracic epidural analgesia on perioperative spirometry. Br J Anaesth 2005; 94:121. 23. Sharma M, Mehta Y, Sawhney R, et al. Thoracic epidural analgesia in obese patients with body mass index of more than 30 kg/m2 for off pump coronary artery bypass surgery. Ann Card Anaesth 2010; 13:28. 24. Bamgbade OA, Khalaf WM, Ajai O, et al. Obstetric anaesthesia outcome in obese and non-obese parturients undergoing caesarean delivery: an observational study. Int J Obstet Anesth 2009; 18:221. 25. Sprung J, Bourke DL, Grass J, et al. Predicting the difficult neuraxial block: a prospective study. Anesth Analg 1999; 89:384. 26. de Filho GR, Gomes HP, da Fonseca MH, et al. Predictors of successful neuraxial block: a prospective study. Eur J Anaesthesiol 2002; 19:447. 27. Chakravartty S, Sarma DR, Patel AG. Rhabdomyolysis in bariatric surgery: a systematic review. Obes Surg 2013; 23:1333. 28. Vaughan RW, Wise L. Intraoperative arterial oxygenation in obese patients. Ann Surg 1976; 184:35. 29. Pelosi P, Croci M, Calappi E, et al. Prone positioning improves pulmonary function in obese patients during general anesthesia. Anesth Analg 1996; 83:578. 30. Palmon SC, Kirsch JR, Depper JA, Toung TJ. The effect of the prone position on pulmonary mechanics is frame-dependent. Anesth Analg 1998; 87:1175. 31. Wu SD, Yilmaz M, Tamul PC, et al. Awake endotracheal intubation and prone patient self-positioning: anesthetic and positioning considerations during percutaneous nephrolithotomy in obese patients. J Endourol 2009; 23:1599. 32. Douglass J, Fraser J, Andrzejowski J. Awake intubation and awake prone positioning of a morbidly obese patient for lumbar spine surgery. Anaesthesia 2014; 69:166. 33. Isono S, Tanaka A, Nishino T. Lateral position decreases collapsibility of the passive pharynx in patients with obstructive sleep apnea. Anesthesiology 2002; 97:780. 34. Ikeya E, Taguchi J, Ohta K, et al. Compartment syndrome of bilateral lower extremities following laparoscopic surgery of rectal cancer in lithotomy position: report of a case. Surg Today 2006; 36:1122. 35. Mathews PV, Perry JJ, Murray PC. Compartment syndrome of the well leg as a result of the hemilithotomy position: a report of two cases and review of literature. J Orthop Trauma 2001; 15:580. 36. http://www.apsf.org/newsletters/html/2013/spring/07_tabletipdanger.htm (Accessed on August 21, 2013). 37. Nielsen KC, Guller U, Steele SM, et al. Influence of obesity on surgical regional anesthesia in the ambulatory setting: an analysis of 9,038 blocks. Anesthesiology 2005; 102:181. 38. Schwemmer U, Papenfuss T, Greim C, et al. Ultrasound-guided interscalene brachial plexus anaesthesia: differences in success between patients of normal and excessive weight. Ultraschall Med 2006; 27:245. http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTer…

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39. Govindarajan R, Ghosh B, Sathyamoorthy MK, et al. Efficacy of ketorolac in lieu of narcotics in the operative management of laparoscopic surgery for morbid obesity. Surg Obes Relat Dis 2005; 1:530. 40. Kamelgard JI, Kim KA, Atlas G. Combined preemptive and preventive analgesia in morbidly obese patients undergoing open gastric bypass: A pilot study. Surg Obes Relat Dis 2005; 1:12. 41. Schumann R, Shikora S, Weiss JM, et al. A comparison of multimodal perioperative analgesia to epidural pain management after gastric bypass surgery. Anesth Analg 2003; 96:469. 42. McNicol ED, Tzortzopoulou A, Cepeda MS, et al. Single-dose intravenous paracetamol or propacetamol for prevention or treatment of postoperative pain: a systematic review and meta-analysis. Br J Anaesth 2011; 106:764. 43. Apfel CC, Turan A, Souza K, et al. Intravenous acetaminophen reduces postoperative nausea and vomiting: a systematic review and meta-analysis. Pain 2013; 154:677. 44. Feld JM, Laurito CE, Beckerman M, et al. Non-opioid analgesia improves pain relief and decreases sedation after gastric bypass surgery. Can J Anaesth 2003; 50:336. 45. Sollazzi L, Modesti C, Vitale F, et al. Preinductive use of clonidine and ketamine improves recovery and reduces postoperative pain after bariatric surgery. Surg Obes Relat Dis 2009; 5:67. 46. Pawlik MT, Hansen E, Waldhauser D, et al. Clonidine premedication in patients with sleep apnea syndrome: a randomized, double-blind, placebo-controlled study. Anesth Analg 2005; 101:1374. 47. Feld JM, Hoffman WE, Stechert MM, et al. Fentanyl or dexmedetomidine combined with desflurane for bariatric surgery. J Clin Anesth 2006; 18:24. 48. Tufanogullari B, White PF, Peixoto MP, et al. Dexmedetomidine infusion during laparoscopic bariatric surgery: the effect on recovery outcome variables. Anesth Analg 2008; 106:1741. 49. Bakhamees HS, El-Halafawy YM, El-Kerdawy HM, et al. Effects of dexmedetomidine in morbidly obese patients undergoing laparoscopic gastric bypass. Middle East J Anaesthesiol 2007; 19:537. 50. Tiippana EM, Hamunen K, Kontinen VK, Kalso E. Do surgical patients benefit from perioperative gabapentin/pregabalin? A systematic review of efficacy and safety. Anesth Analg 2007; 104:1545. 51. Straube S, Derry S, Moore RA, et al. Single dose oral gabapentin for established acute postoperative pain in adults. Cochrane Database Syst Rev 2010; :CD008183. 52. Engelman E, Cateloy F. Efficacy and safety of perioperative pregabalin for post-operative pain: a metaanalysis of randomized-controlled trials. Acta Anaesthesiol Scand 2011; 55:927. 53. Regli A, von Ungern-Sternberg BS, Reber A, Schneider MC. Impact of spinal anaesthesia on perioperative lung volumes in obese and morbidly obese female patients. Anaesthesia 2006; 61:215. 54. Taivainen T, Tuominen M, Rosenberg PH. Influence of obesity on the spread of spinal analgesia after injection of plain 0.5% bupivacaine at the L3-4 or L4-5 interspace. Br J Anaesth 1990; 64:542. 55. McCulloch WJ, Littlewood DG. Influence of obesity on spinal analgesia with isobaric 0.5% bupivacaine. Br J Anaesth 1986; 58:610. 56. Hodgkinson R, Husain FJ. Obesity and the cephalad spread of analgesia following epidural administration of bupivacaine for Cesarean section. Anesth Analg 1980; 59:89. 57. Qadeer MA, Rocio Lopez A, Dumot JA, Vargo JJ. Risk factors for hypoxemia during ambulatory gastrointestinal endoscopy in ASA I-II patients. Dig Dis Sci 2009; 54:1035. 58. Chung F, Mezei G, Tong D. Pre-existing medical conditions as predictors of adverse events in day-case surgery. Br J Anaesth 1999; 83:262. 59. American Society of Anesthesiologists Committee. Practice guidelines for preoperative fasting and the use of pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: an updated report by the American Society of Anesthesiologists Committee on Standards and Practice Parameters. Anesthesiology 2011; 114:495. 60. Zalar A, Haddouche B, Antonietti M, et al. Lack of correlation between morbid obesity and severe gastroesophageal reflux disease in candidates for bariatric surgery: results of a large prospective study. Obes Surg 2013; 23:1939. 61. Lundstrøm LH, Møller AM, Rosenstock C, et al. High body mass index is a weak predictor for difficult and failed tracheal intubation: a cohort study of 91,332 consecutive patients scheduled for direct laryngoscopy registered in the Danish Anesthesia Database. Anesthesiology 2009; 110:266. 62. El-Orbany M, Woehlck HJ. Difficult mask ventilation. Anesth Analg 2009; 109:1870. http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTer…

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63. Dixon BJ, Dixon JB, Carden JR, et al. Preoxygenation is more effective in the 25 degrees head-up position than in the supine position in severely obese patients: a randomized controlled study. Anesthesiology 2005; 102:1110. 64. Altermatt FR, Muñoz HR, Delfino AE, Cortínez LI. Pre-oxygenation in the obese patient: effects of position on tolerance to apnoea. Br J Anaesth 2005; 95:706. 65. Collins JS, Lemmens HJ, Brodsky JB, et al. Laryngoscopy and morbid obesity: a comparison of the "sniff" and "ramped" positions. Obes Surg 2004; 14:1171. 66. El-Orbany M, Woehlck H, Salem MR. Head and neck position for direct laryngoscopy. Anesth Analg 2011; 113:103. 67. Baraka AS, Taha SK, Aouad MT, et al. Preoxygenation: comparison of maximal breathing and tidal volume breathing techniques. Anesthesiology 1999; 91:612. 68. Gagnon C, Fortier LP, Donati F. When a leak is unavoidable, preoxygenation is equally ineffective with vital capacity or tidal volume breathing. Can J Anaesth 2006; 53:86. 69. Gambee AM, Hertzka RE, Fisher DM. Preoxygenation techniques: comparison of three minutes and four breaths. Anesth Analg 1987; 66:468. 70. Gander S, Frascarolo P, Suter M, et al. Positive end-expiratory pressure during induction of general anesthesia increases duration of nonhypoxic apnea in morbidly obese patients. Anesth Analg 2005; 100:580. 71. Futier E, Constantin JM, Pelosi P, et al. Noninvasive ventilation and alveolar recruitment maneuver improve respiratory function during and after intubation of morbidly obese patients: a randomized controlled study. Anesthesiology 2011; 114:1354. 72. Delay JM, Sebbane M, Jung B, et al. The effectiveness of noninvasive positive pressure ventilation to enhance preoxygenation in morbidly obese patients: a randomized controlled study. Anesth Analg 2008; 107:1707. 73. Weingart SD, Levitan RM. Preoxygenation and prevention of desaturation during emergency airway management. Ann Emerg Med 2012; 59:165. 74. Ramachandran SK, Cosnowski A, Shanks A, Turner CR. Apneic oxygenation during prolonged laryngoscopy in obese patients: a randomized, controlled trial of nasal oxygen administration. J Clin Anesth 2010; 22:164. 75. Taha SK, Siddik-Sayyid SM, El-Khatib MF, et al. Nasopharyngeal oxygen insufflation following preoxygenation using the four deep breath technique. Anaesthesia 2006; 61:427. 76. Rothen HU, Sporre B, Engberg G, et al. Prevention of atelectasis during general anaesthesia. Lancet 1995; 345:1387. 77. Edmark L, Kostova-Aherdan K, Enlund M, Hedenstierna G. Optimal oxygen concentration during induction of general anesthesia. Anesthesiology 2003; 98:28. 78. Hedenstierna G, Rothen HU. Respiratory function during anesthesia: effects on gas exchange. Compr Physiol 2012; 2:69. 79. Carron M, Veronese S, Gomiero W, et al. Hemodynamic and hormonal stress responses to endotracheal tube and ProSeal Laryngeal Mask Airway™ for laparoscopic gastric banding. Anesthesiology 2012; 117:309. 80. Gaszynski T, Szewczyk T, Gaszynski W. Randomized comparison of sugammadex and neostigmine for reversal of rocuronium-induced muscle relaxation in morbidly obese undergoing general anaesthesia. Br J Anaesth 2012; 108:236. 81. Carron M, Parotto E, Ori C. Prolonged neuromuscular block associated to non-alcoholic steatohepatitis in morbidly obese patient: neostigmine versus sugammadex. Minerva Anestesiol 2012; 78:112. 82. Carron M, Freo U, Ori C. Sugammadex for treatment of postoperative residual curarization in a morbidly obese patient. Can J Anaesth 2012; 59:813. 83. Van Lancker P, Dillemans B, Bogaert T, et al. Ideal versus corrected body weight for dosage of sugammadex in morbidly obese patients. Anaesthesia 2011; 66:721. 84. Schumann R. Pulmonary physiology of the morbidly obese and the effects of anesthesia. Int Anesthesiol Clin 2013; 51:41. 85. Pelosi P, Brusasco C, Reinius h. Is protective lung ventilation safe in morbidly obese patients?. In: http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTer…

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Controversies in the Management of the Obese Surgical Patinet, Leykin Y, Brodsky JB. (Eds), SpringerVerlag Italia, Milan, Heidelberg, New York, Dordrecht, London 2013. p.179. 86. Futier E, Constantin JM, Paugam-Burtz C, et al. A trial of intraoperative low-tidal-volume ventilation in abdominal surgery. N Engl J Med 2013; 369:428. 87. Aldenkortt M, Lysakowski C, Elia N, et al. Ventilation strategies in obese patients undergoing surgery: a quantitative systematic review and meta-analysis. Br J Anaesth 2012; 109:493. 88. Erlandsson K, Odenstedt H, Lundin S, Stenqvist O. Positive end-expiratory pressure optimization using electric impedance tomography in morbidly obese patients during laparoscopic gastric bypass surgery. Acta Anaesthesiol Scand 2006; 50:833. 89. Talab HF, Zabani IA, Abdelrahman HS, et al. Intraoperative ventilatory strategies for prevention of pulmonary atelectasis in obese patients undergoing laparoscopic bariatric surgery. Anesth Analg 2009; 109:1511. 90. Whalen FX, Gajic O, Thompson GB, et al. The effects of the alveolar recruitment maneuver and positive end-expiratory pressure on arterial oxygenation during laparoscopic bariatric surgery. Anesth Analg 2006; 102:298. 91. Bohm SH, Thamm OC, von Sandersleben A, et al. Alveolar recruitment strategy and high positive endexpiratory pressure levels do not affect hemodynamics in morbidly obese intravascular volume-loaded patients. Anesth Analg 2009; 109:160. 92. Strum EM, Szenohradszki J, Kaufman WA, et al. Emergence and recovery characteristics of desflurane versus sevoflurane in morbidly obese adult surgical patients: a prospective, randomized study. Anesth Analg 2004; 99:1848. 93. Juvin P, Vadam C, Malek L, et al. Postoperative recovery after desflurane, propofol, or isoflurane anesthesia among morbidly obese patients: a prospective, randomized study. Anesth Analg 2000; 91:714. 94. Bilotta F, Doronzio A, Cuzzone V, et al. Early postoperative cognitive recovery and gas exchange patterns after balanced anesthesia with sevoflurane or desflurane in overweight and obese patients undergoing craniotomy: a prospective randomized trial. J Neurosurg Anesthesiol 2009; 21:207. 95. Leykin Y, Pellis T, Del Mestro E, et al. Anesthetic management of morbidly obese and super-morbidly obese patients undergoing bariatric operations: hospital course and outcomes. Obes Surg 2006; 16:1563. 96. De Baerdemaeker LE, Jacobs S, Den Blauwen NM, et al. Postoperative results after desflurane or sevoflurane combined with remifentanil in morbidly obese patients. Obes Surg 2006; 16:728. 97. Arain SR, Barth CD, Shankar H, Ebert TJ. Choice of volatile anesthetic for the morbidly obese patient: sevoflurane or desflurane. J Clin Anesth 2005; 17:413. 98. Vallejo MC, Sah N, Phelps AL, et al. Desflurane versus sevoflurane for laparoscopic gastroplasty in morbidly obese patients. J Clin Anesth 2007; 19:3. 99. Zeidan A, Mazoit JX. Minimal alveolar concentration of sevoflurane for maintaining bispectral index below 50 in morbidly obese patients. Acta Anaesthesiol Scand 2013; 57:474. 100. Matsuura T, Oda Y, Tanaka K, et al. Advance of age decreases the minimum alveolar concentrations of isoflurane and sevoflurane for maintaining bispectral index below 50. Br J Anaesth 2009; 102:331. 101. Brodsky JB, Lemmens HJ, Collins JS, et al. Nitrous oxide and laparoscopic bariatric surgery. Obes Surg 2005; 15:494. 102. Jain AK, Dutta A. Stroke volume variation as a guide to fluid administration in morbidly obese patients undergoing laparoscopic bariatric surgery. Obes Surg 2010; 20:709. 103. Thomas JA, McIntosh JM. Are incentive spirometry, intermittent positive pressure breathing, and deep breathing exercises effective in the prevention of postoperative pulmonary complications after upper abdominal surgery? A systematic overview and meta-analysis. Phys Ther 1994; 74:3. 104. Squadrone V, Coha M, Cerutti E, et al. Continuous positive airway pressure for treatment of postoperative hypoxemia: a randomized controlled trial. JAMA 2005; 293:589. 105. Neligan PJ, Malhotra G, Fraser M, et al. Noninvasive ventilation immediately after extubation improves lung function in morbidly obese patients with obstructive sleep apnea undergoing laparoscopic bariatric surgery. Anesth Analg 2010; 110:1360. 106. Battisti A, Michotte JB, Tassaux D, et al. Non-invasive ventilation in the recovery room for postoperative respiratory failure: a feasibility study. Swiss Med Wkly 2005; 135:339. http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTer…

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107. Huerta S, DeShields S, Shpiner R, et al. Safety and efficacy of postoperative continuous positive airway pressure to prevent pulmonary complications after Roux-en-Y gastric bypass. J Gastrointest Surg 2002; 6:354. 108. Ramirez A, Lalor PF, Szomstein S, Rosenthal RJ. Continuous positive airway pressure in immediate postoperative period after laparoscopic Roux-en-Y gastric bypass: is it safe? Surg Obes Relat Dis 2009; 5:544. 109. www.asahq.org (Accessed on December 08, 2010). 110. Gross JB, Bachenberg KL, Benumof JL, et al. Practice guidelines for the perioperative management of patients with obstructive sleep apnea: a report by the American Society of Anesthesiologists Task Force on Perioperative Management of patients with obstructive sleep apnea. Anesthesiology 2006; 104:1081. 111. Joshi GP, Ankichetty SP, Gan TJ, Chung F. Society for Ambulatory Anesthesia consensus statement on preoperative selection of adult patients with obstructive sleep apnea scheduled for ambulatory surgery. Anesth Analg 2012; 115:1060. Topic 14932 Version 24.0

http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTer…

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GRAPHICS

Cardiovascular physiologic changes in obesity

Pathogenesis of congestive heart failure in morbidly obese individuals with and without sleep apnea/obesity hypoventilation syndrome. LV: left ventricle; RV: right ventricle. Reproduced with permission from: Alpert MA, Hashimi MW. Obesity and the heart. Am J Med Sci 1993 ; 306:11 7. www.lww.com. Copyright © 19 93 Southern Society for Clinical Investigation. Unauthorized reproduction of this material is prohibited. Graphic 90114 Version 1.0


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Comparison of cardiac structural and hemodynamic alterations in patients with morbid obesity and hypertension Obesity alone

Hypertension alone

Obesity and hypertension

Variable Heart rate

Normal

Normal

Normal

Blood pressure

Normal

Increased

Increased

Stroke volume

Increased

Normal

Increased

Cardiac output

Increased

Normal

Increased

Systemic vas cular

Decreased

Increased

Normal or increased

LV volume

Increased

Normal

Increased

LV wall stress

Normal or

Normal or

Increased

increased

increased

LV hypertrophy

Eccentric

Concentric

Hybrid

LV diastolic

Us ua lly p re se nt



LV systolic

Occasionally

Usually abs ent

Occa sionally pres ent

dysfunction

present

LV failure

Occasionally

Occasionally

Commonly pres ent

present

present

Occasionally

Usually abs ent


Usually abs ent


Usually abs ent


resistance

dysfunction

RV hypertrophy

present RV enlargement

Occasionally present

RV failure

Occasionally present

LV: left ventricular; RV: right ventricular. Adapted from: Alpert MA, Hashimi MW. Obesity and the heart. Am J Med Sci 1993; 306:117. Graphic 74883 Version 3.0


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Anesthetic drug dosing in obesity Drug

Weight for dosing

Notes

Sedative/hypnotics Propo fol bolus

LBW

obese patients (BMI >40 kg/m 2) [1].

doses Propofol

The dos e required for lo ss of co nsciousnes s in

LBW

Du e to sub sta ntia l inte rind ivid ua l va ria bility,

maintenance

continuous infusions s hould be titrated to a

infusions

clinical endpoint. A reasonable initial dose is based on LBW a nd titrated to achieve the de sired clinical res ult. Seve ral differen t dose calculation mode ls have bee n used for target controlled infusion s ystems (not available in the United States) [2].

Etomidate

LBW

Pharmacokinetic studies have not been done in obesity [3].

Thiopental

LBW

Recommendation is based on computer models of plasma concentrations. Dose s sho uld be adjusted for high o r low cardiac output, and rapid redistribution may result in more rapid a wa kening after a single bolus dose than in lean patients [4].

Midazolam (and

TBW

As a s ed ative , u su ally d os ed in s ma ll incre me nts

other

(eg, midazolam 1 mg IV) that are repeated until

benzodiazepines)

the clinical endp oint is reached. Ca ution sho uld

bolus doses

be e xercised as patients w ith OSA may have increase d central sens itivity to the s eda tive a nd respiratory effects of be nzod iazepines . TBW is used for bolus dosing (eg, to induce general anes thesia) due to the significant increase in V d in these highly lipophilic drugs [5] .

Midazolam (and

LBW

Alth ou gh cle ara nce is no t s ub sta ntia lly d iffe re nt

other

from that in non-obese individuals [6] , there is

benzodiazepines)

substantial interindividual variability, so

continuous

continuous infusions s hould be titrated to a

infusions

clinical endpoint. A reasonable initial dose is based on LBW a nd titrated to achieve the de sired clinical result.

De xme de to mid ine

The re a re no s pe cific do sing re co mme nd atio ns available in the obese , but as w ith other infusions, dos es shou ld be titrated to a clinical end point. The d rug is high ly lipoph ilic. Bolus (0.5 to 1 mcg/kg) and infusion d os ing (0.2 to 0.8 mcg/kg) base d o n TBW (without a scalar) have b ee n us ed in s eve ra l s tu die s [7-10]. This is w ithin the manufacturer-sugg este d dos e range. Dose adjustments may be required for other comorbidities or othe r seda tive or an esthe tic


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drugs used concomitantly. Opioids Synthetic opioids

LBW

O n th e b as is of clin ica l p ha rma co kine tic s tu die s in

(fentanyl,

lean pa tients, physiologic change s in ob esity, and

sufentanil,

suprathe rapeutic plasma levels w ith TBW

alfentanil, and

dosing [6] .

remifentanil) Morphine

IBW

Initial dosing should be based on IBW and titrated to e ffect. This is a reaso nable initial dos e, as postoperative opioid consumption was 30 percent less in obe se versus no rmal weight patients (on a morphine equivalent to kg bas is) [11].

Hydromorphone

IBW

As with morphine, initial dosing is based on IBW and titrated to effect.

Neuromuscular blocking agents Non-depolarizing

IBW

Generally polar compounds [12] . The dosing scalar

agents (eg,

will depe nd o n the clinical circumsta nce. In

vecuronium,

general, a higher (ie, closer to TBW) intubating

rocuronium)

dos e w ill resu lt in faster ons et and shorter time to complete NMB, but a longer duration o f action. An IBW-bas ed d osing w ill prolong the time to ideal intubating conditions, but assure a faster recovery from NMB [13].

Succinylcholine

TBW

This is based on superior intubating conditions whe n s uccinylcholine 1 mg/kg TBW w as compared w ith do sing o n the ba sis o f IBW o r LBW [14].

LBW: lean body w eight; TBW: total bod y we ight; IBW: ideal body w eight; BMI: body mass index; OSA: obs tructive s leep ap nea V d : volume of distribution; NMB: neuromuscular blockade. References: 1. Ingrande J, Brodsky JB, Lemmens HJ. Lean body weight s calar for the anesthetic induction dose of propofol in morbidly obese s ubjects. Anesth Analg 201 1; 113:57. 2. Echevarria GC, Elgueta MF, Donos oto MT, et al. The effective effect-site propofol concentration for induction and intubation with two pharmacokinetic models in morbidly obese patients using total body weight. Anesth Analg 2012; 115:823. 3. Ingrande J, Lemmens HJ. Dose adjustment of anaesthetics in the morbidly obese. Br J Anaesth 2 010 ; 105 Suppl 1:i16. 4. Wada DR, Björkman S, Ebling WF, et al. Computer simulation of the effects of alterations in blood flows and body composition on th iopental pharmacokinetics in humans. Anesthesiology 1997; 87:884. 5. Greenblatt DJ, Aberneth y DR, Locnis kar A, et al. Effect of age, gender, and obesity on midazolam kinetics. Anesthesiology 1984; 61:27. 6. Leykin Y, Miotto L, Pellis T. Pharmacokinetic considerations in the obese. Best Pract Res Clin Anaesthesiol 2011; 25:27. 7. Feld J, Hoffman WE . Response entropy is more reactive than bispectral index during laparoscopic gastric banding. J Clin Monit Comput 2006; 2 0:229 . 8. Bakhamees HS, El-Halafawy YM, El-Kerdawy HM, et al. Effects of dexmedetomidine in morbidly obese patients undergoing laparoscopic gastric bypass. Middle East J Anes thes iol 2007 ; 19:537. http://www.uptodate.com/contents/anesthesia-for-the-obese-patient?topicKey=ANEST%2F14932&elapsedTimeMs=1&source=search_result&searchTer…

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9. Tufanogullari B, White PF, Peixoto MP, et al. Dexmedetomidine infusion during laparoscopic bariatric surgery: the effect on recovery outcome variables. Anes th Analg 2008; 106:17 41. 10. Ramsay MA. Bariatric surgery: The role of dexmedetomidine. Seminars in Anesthes ia, Perioperative Medicine and Pain 20 06; 2 5:51. 11. Rand CS, Kuldau JM, Yost RL. Obesity and post-operative pain. J Psychosom Res 1985; 29 :43. 12. Blouin RA, Warren GW. Pharmacokinetic considerations in obesity. J Pharm Sci 1999; 88:1. 13. Leykin Y, Pellis T, Lucca M, et al. The effects of cisatracuriu m on morbidly obese women . Anesth Analg 2004; 99:109 0. 14. Lemmens HJ, Brodsky JB. The dose of succinylcholine in morbid obesity. Anesth Analg 2006 ; 102:438. Graphic 90705 Version 1.0


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Ramp position illustration

In the ramp position, the patient's head and torso are elevated such that the external auditory meatus and the sternal notch are horizontally aligned (black line). This position allows for a better view of the glottis in obese patients and should be used unless there are contraindications (eg, possible cervical spine injury). Graphic 95285 Version 4.0


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Suggested contents of difficult airway cart in the operating room Rigid laryngos cope blade s o f alternate d esign a nd size from those routinely used; this may include a rigid fiberoptic laryngoscope. Videolaryngoscope. Tracheal tubes of asso rted sizes. Tracheal tube guides. Examples include (but are not limited to) semirigid stylets, ventilating tube-changer, light wand s, and forceps des igned to manipulate the distal portion of the tracheal tube. Supraglottic airwa ys (eg, LMAs or ILMAs of ass orted s izes for non invasive airway ventilation/intubation). Flexible fiberoptic intubation equipment. Equipment s uitable for emergency invasive airwa y access. An exhaled carbon dioxide detector.

The items listed in this table represent suggestions. The contents of the portable storage unit should be customized to meet the specific needs, preferences, and skills of the practitioner and healthcare facility. LMA: laryngea l mas k airwa y; ILMA: intuba ting LMA. From: Apfelbaum JL, Hagberg CA, Caplan RA, et al. Practice guidelines for management of the difficult airway: an u pdated report by th e American Society of Anesthes iologists Task Force on Management of the Difficult Airway. Anesthesiology. 201 3; 11 8:251 . DOI: 10.1097/ALN.0b013e31827773b2. Reproduced with permission from Lippincott Williams & Wilkins. Copyright © 20 13 American Society of Anesthesiologists . Unauthorized reproduction of this material is prohibited. Graphic 89959 Version 5.0


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Disclosures Rom an Schumann, M D Nothing to disclose. Stephanie B Jones , MD Consultant/Advisory Boards (Spouse): A llurion Technologies [Obesity (Non-surgical w eight loss device)]. Marianna Crowley, MD Nothing to disclose. Contributor disclosures are review ed for c onflicts of interest by the editorial group. When found, these are addressed by v etting through a multi-level review process , and through requirements for ref erences to be provided to support the content. Appropriately ref erenced c ontent is required of all authors and must conform to UpToDate standards of evidence. Disclosures:

Conflict of intere st policy


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Anesthesia for the Obese Patient

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