Ambulatory anesthesia for the obese patient Fre´de´rique Servin

Purpose of review Obese patients are more and more frequently proposed for elective surgery, including acts specifically aimed at curing this condition, i.e. bariatric surgery. Many of these acts present characteristics compatible with ambulatory treatment, but anesthesiologists are reluctant to treat the morbidly obese as outpatients due to lack of data on the safety of this approach. The purpose of this review is to present the information that could be found in the literature on the safety and feasibility of ambulatory procedures in obese patients, and outline the specificity of this population. Recent findings During the last few years, the risks of perioperative complications in this population have been estimated more precisely, specifically respiratory events. A better knowledge of the pharmacology of anesthetic drugs in this population allows optimization of general anesthesia protocols and the interest of regional anesthesia has also been outlined. A first study on gastric banding has demonstrated the suitability of the ambulatory setting for such a procedure. Summary Ambulatory care in the obese patient is both feasible and well suited to this population provided a few specificities are taken into account. Keywords bariatric surgery, obese, outpatient, perioperative risk Curr Opin Anaesthesiol 19:597–599. ß 2006 Lippincott Williams & Wilkins. Service d’Anesthe´sie-Re´animation, Hoˆpital Bichat, Paris, France Correspondence to Dr Fre´de´rique Servin, Service d’Anesthe´sie-Re´animation, Hoˆpital Bichat, 46 rue Henri Huchard, 75877 Paris Cedex 18, France Tel: +33 1 4025 5115; fax: +33 1 4228 9996; e-mail: [email protected] Current Opinion in Anaesthesiology 2006, 19:597–599 Abbreviation BMI

body mass index

ß 2006 Lippincott Williams & Wilkins 0952-7907

Introduction Obesity is a disease characterized by an excess accumulation of body fat. Morbid obesity is defined as a body mass index [BMI ¼ weight (kg)/height (m2)] of more than 31. Obesity is associated with a higher risk of cardiac disease and stroke, and an increased anesthetic morbidity and mortality. In this context, at a time when the prevalence of obesity is increasing, the question arises of the eligibility of this population for ambulatory surgery and anesthesia.

Physiopathological consequences of obesity The consequences of obesity include high blood pressure, coronary artery disease, diabetes mellitus, sleep apnea syndrome and higher risk of deep venous thrombosis. The risk of perioperative adverse events in obese outpatients was described a few years ago when Bryson et al. [1] studied 2799 obese among 17 368 outpatients. The main result was an increased risk of respiratory adverse events – 4 times more frequent in the obese when compared to normal weight patients. Nevertheless, the incidence of these perioperative events remained low (overall risk of adverse event intraoperatively 4.9%, in the post-anesthesia care unit 10.3% and in the ambulatory surgery unit 6.3%) and did not increase the rate of unanticipated admissions, which confirms the eligibility of obese patients for ambulatory procedures, with some caution.

Airway control Obese patients are at risk of rapid desaturation and hypoxemia, and poorly tolerate apneic episodes. Is airway control more difficult in this population? Juvin et al. [2] have assessed the risk of difficult intubation in morbidly obese patients and found that the Mallanpati score was a predictor, albeit with a poor negative predictive value, of difficult intubation in this population, but that no correlation could be found with BMI. The same team had previously described that morbidly obese patients were no more at risk of aspiration of gastric content than normal weight patients [3]. The only parameter predictive of difficult intubation in morbidly obese patients seems to be the circumference of the neck [4], but not the BMI.

Prophylaxis of deep venous thrombosis Obesity is a well-known risk factor for deep venous thrombosis and perioperative management of this risk may reduce the ease of ambulatory care in such patients. In a prospective study involving 380 morbidly obese patients presented for laparoscopic Roux-en-Y gastric 597

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598 Ambulatory anaesthesia

bypass of a mean duration time of 103 min, Gonzales et al. [5] found only one deep venous thrombosis when calflength pneumatic compression stockings were used in the absence of any anticoagulants. Therefore, the initiation of calf-length pneumatic compression hose before the induction of anesthesia may be sufficient in short procedures performed in obese outpatients to prevent deep venous thrombosis without any form of heparin anticoagulation.

General anesthesia in the ambulatory obese patient – which drugs, which doses? The choice of the anesthetic protocol in obese patients must ensure good intraoperative hemodynamic control and adequate depth of anesthesia, but mainly prepare a rapid and clear-headed recovery. Propofol has been proposed for induction and maintenance of anesthesia in obese patients. This lipid-soluble drug has a high clearance which, along with its volume of distribution, is proportional to total body weight. Therefore, the doses should be calculated on a total weight basis in this population. Obese patients do not require specific models for target-controlled propofol infusion. Nevertheless, the hypnotic which has the least potential for accumulation in this population is desflurane – the volatile agent with the lowest solubility in fat tissues. This chemical advantage leads to more rapid immediate recovery in obese patients when compared to sevoflurane [6], which may be a decisive advantage in the ambulatory setting. When considering fentanyl and its congeners, only alfentanil and remifentanil [7] do not accumulate in fat tissues. They are consequently the drugs of choice in obese patients, provided their doses are calculated as a function of ideal body weight and age, and not taking into account the actual weight of the patient. Nevertheless, if fentanyl is chosen, its doses should also be adapted and calculated as a function of what Shibutani et al. [8] call the ‘pharmacokinetic mass’ and correspond to a more appropriate dosing weight to be used to correct patient actual total body weight in this population. Despite its cumulative potential, sufentanil may also be used in this population, but doses should not be increased as a function of BMI [9].

Regional anesthesia in the obese patient Delayed recovery from general anesthesia and post-operative hypoxemia eventually related to a sleep apnea syndrome are the most dreaded adverse outcomes in ambulatory obese patients. It therefore sounds interesting to perform regional blocks as often as possible in this population. In a recent study based on prospectively collected data including 9038 blocks performed on

6920 patients in a single ambulatory surgery center [10], the authors demonstrated that the obese patients were 1.62 times more likely to have a failed peripheral block (failure rate 12.7% with a BMI > 30, when compared to 9.5% in normal weight patients, P ¼ 0.04). Conversely when the block was successful, there was no difference in pain scores at rest, post-operative nausea/ vomiting requiring treatment, length of post-anesthesia care unit stay or unanticipated hospital admission. Consequently, the anesthetist must be aware of this greater risk of block failure, but regional anesthesia may be performed in obese patients in the ambulatory setting.

Can bariatric surgery be performed in outpatients? Laparoscopic adjustable gastric banding is a procedure frequently proposed to help weight reduction in obese patients. It is not very invasive since it does not include any opening of the digestive tract. Since laparoscopic cholecystectomies are routinely proposed on an outpatient basis, why nor gastric banding? Recently, a prospective study [11] has included 343 patients [305 females (88.9%) and 38 males (11.1%), age 43.5  9.9 years, with BMI ¼ 44.5  6.1 kg/m2] proposed for adjustable gastric banding in an ambulatory center. The operating room time was 52.9  16.3 min. Ten complications were described in nine patients (2.8%): five stoma occlusions, three port problems requiring port replacement, one superficial wound infection and one colon perforation associated with adhesiolysis requiring band removal (complete recovery for all). Three patients required admission to the hospital: one for nausea, one for observation after bloody nasogastric tube drainage and one for dysphagia due to esophageal spasm. This study is the first to confirm the feasibility of gastric banding in outpatients.

Conclusion All the data currently available demonstrate that ambulatory anesthesia is possible in the fit obese patient, despite an increased risk of perioperative respiratory adverse events. Written guidelines should be readily available in the outpatient facility, which should not be isolated. The devices (from the operating table to the pressure cuffs) should be adapted to those patients needs.

References and recommended reading Papers of particular interest, published within the annual period of review, have been highlighted as:  of special interest  of outstanding interest Additional references related to this topic can also be found in the Current World Literature section in this issue (p. 662). 1

Bryson GL, Chung F, Cox RG, et al. Patient selection in ambulatory anesthesia – an evidence-based review: part II. Can J Anaesth 2004; 51: 782–794.

2

Juvin P, Lavaut E, Dupont H, et al. Difficult tracheal intubation is more common in obese than in lean patients. Anesth Analg 2003; 97:595–600.

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Juvin P, Fevre G, Merouche M, et al. Gastric residue is not more copious in obese patients. Anesth Analg 2001; 93:1621–1622.

4

Brodsky JB, Lemmens HJ, Brock-Utne JG, et al. Morbid obesity and tracheal intubation. Anesth Analg 2002; 94:732–736.

5

Gonzales QH, Tishler DS, Plata-Munoz JJ, et al. Incidence of clinically evident deep venous thrombosis after laparoscopic Roux-en-Y gastric bypass. Surg Endosc 2004; 18:1082–1084.

6

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; 99:1848–1853.

7

Scott LJ, Perry CM. Remifentanil: a review of its use during the induction and maintenance of general anaesthesia. Drugs 2005; 65:1793– 1823.

8

Shibutani K, Inchiosa MA Jr, Sawada K, et al. Accuracy of pharmacokinetic models for predicting plasma fentanyl concentrations in lean and obese surgical patients: derivation of dosing weight (‘pharmacokinetic mass’). Anesthesiology 2004; 101:603–613.

9

Slepchenko G, Simon N, Goubaux B, et al. Performance of target-controlled sufentanil infusion in obese patients. Anesthesiology 2003; 98:65–73.

10 Nielsen KC, Guller U, Steele SM, et al. Influence of obesity on surgical regional  anesthesia in the ambulatory setting: an analysis of 9038 blocks. Anesthesiology 2005; 102:181–187. Regional anesthesia is considered difficult in obese patients. This retrospective analysis demonstrates the real failure rate in this population and its consequences. 11 Watkins BM, Montgomery KF, Ahroni JH, et al. Adjustable gastric banding in  an ambulatory surgery center. Obes Surg 2005; 15:1045–1049. Gastric banding is one of the most frequent surgical procedures proposed for obese patients. This study presents data on its applicability in the ambulatory setting.

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