Perioperative Care of Patients Undergoing Bariatric Surgery

SUPPLEMENT ARTICLE

PERIOPERATIVE CARE FOR BARIATRIC SURGERY

Perioperative Care of Patients Undergoing Bariatric Surgery BRIAN P. MCGLINCH, MD; FLORENCIA G. QUE, MD; JOYCE L. NELSON, RN; DIANE M. WROBLESKI, RN, PHD; JEANNE E. GRANT, RD; AND MARIA L. COLLAZO-CLAVELL, MD

The epidemic of obesity in developed countries has resulted in patients with extreme (class III) obesity undergoing the full breadth of medical and surgical procedures. The popularity of bariatric surgery in the treatment of extreme obesity has raised awareness of the unique considerations in the care of this patient population. Minimizing the risk of perioperative complications that contribute to morbidity and mortality requires input from several clinical disciplines and begins with the preoperative assessment of the patient. Airway management, intravenous fluid administration, physiologic responses to pneumoperitoneum during laparoscopic procedures, and the risk of thrombotic complications and peripheral nerve injuries in extremely obese patients are among the factors that present special intraoperative challenges that affect postoperative recovery of the bariatric patient. Early recognition of perioperative complications and education of the patient regarding postoperative issues, including nutrition and vitamin supplementation therapy, can improve patient outcomes. A suitable physical environment and appropriate nursing and dietetic support provide a safe and dignified hospital experience. This article reviews the multidisciplinary management of extremely obese patients who undergo bariatric surgery at the Mayo Clinic.

Mayo Clin Proc. 2006;81(10, suppl):S25-S33 BMI = body mass index; CPAP = continuous positive airway pressure; OSA = obstructive sleep apnea; RYGB = Roux-en-Y gastric bypass

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he vast majority of patients with extreme (class III) obesity who undergo surgical procedures do not undergo bariatric procedures. The epidemic of obesity in developed countries has resulted in patients with extreme obesity undergoing the full breadth of medical and surgical procedures, from childbirth to cardiopulmonary bypass– assisted heart surgery to emergent repairs of ruptured abdominal aortic aneurysms. Bariatric surgery, however, should always be viewed as an elective procedure. As such, preoperative planning must take into account the unique needs of this patient population and all aspects of their care. PREOPERATIVE MEDICAL EVALUATION In another article in this supplement, Collazo-Clavell et al1 detail the assessment of patients to determine their candidacy for bariatric surgery. Preoperative risk is reviewed in that article. This article reviews preoperative evaluation and focuses in depth on perioperative risks and management. The purpose of a preoperative clinical evaluation is to identify unrecognized disease that may increase the risk of Mayo Clin Proc.

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surgery above that expected. Most patients undergoing bariatric surgery have completed a comprehensive medical evaluation conducted by a primary care physician. Underlying pulmonary, cardiovascular, and endocrine disorders have usually been identified, and therapies have been initiated to stabilize existing conditions. Before surgery, a health questionnaire should be completed by the patient to ensure that underlying medical conditions are stable and that no symptoms of new disease have developed. The questionnaire should also document anesthetic and surgical histories. Several versions of preoperative health questionnaires are available (Appendix).2 The patient seeking bariatric surgery rarely has a “negative” health questionnaire. Ramaswamy et al3 prospectively studied 193 patients, with a mean ± SD age of 42±10 years, who had undergone bariatric surgery. More than half of the patients had hypertension, a third had obstructive sleep apnea (OSA), and a quarter had diabetes, all of which had been identified previously and treated by primary care physicians. The authors concluded that further preoperative evaluations were unnecessary because of the participation of a primary care physician in the patient’s medical management before referral for bariatric surgery. Despite relatively higher prevalence in bariatric surgical candidates, weight-related comorbidities, when identified and managed preoperatively, do not appear to increase major surgical risk.4,5 Although performing routine studies in the absence of physical findings is controversial, a list of commonly recommended tests is detailed in Table 1.6 Many obese patients contemplating bariatric surgery do not perform adequate daily physical activity. Assessment of their exercise tolerance provides important information. Patients with low exercise capacity have twice the risk of serious postoperative complications compared to those with unlimited exercise tolerance. The inability to walk 4 blocks on level ground or climb 2 flights of stairs without

From the Department of Anesthesiology (B.P.M.), Division of Gastroenterologic and General Surgery (F.G.Q.), Department of Nursing (J.L.N., D.M.W.), and Division of Endocrinology, Diabetes, Metabolism, and Nutrition (J..E.G., M.L.C.-C.), Mayo Clinic College of Medicine, Rochester, Minn. Address correspondence to Brian P. McGlinch, MD, Department of Anesthesiology, Mayo Clinic College of Medicine, 200 First St SW, Rochester, MN 55905 (e-mail: [email protected]). © 2006 Mayo Foundation for Medical Education and Research

October 2006;81(10, suppl):S25-S33

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www.mayoclinicproceedings.com

For personal use. Mass reproduce only with permission from Mayo Clinic Proceedings.

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TABLE 1. Suggested Preoperative Testing6 Laboratory Hemoglobin/hematocrit Serum creatinine Patients >50 y Serum electrolytes Diuretic use Electrocardiography Men >45 y Women >55 y Patients with known heart disease Patients with suspected heart disease Patients at high risk for heart disease (diabetes mellitus, hypertension) Patients at risk for electrolyte abnormalities (diuretic use) Chest radiography Patients with suspected heart or lung disease Patients >60 y

pulmonary, cardiac, or vascular symptoms correlates with poor exercise tolerance.7,8 Bariatric surgical candidates with poor exercise tolerance and symptoms or clinical evidence of heart disease should be examined by a cardiologist and possibly undergo functional cardiac assessment. Dobutamine stress echocardiography is a useful functional study for bariatric surgical candidates with known or suspected cardiovascular disease because of its ability to induce physiologic stress on the heart in the presence of serious underlying medical conditions that make treadmill evaluations difficult or impossible.9 In obese patients with coronary artery disease, dobutamine stress echocardiography may provide information regarding hemodynamic parameters associated with ischemia, allowing interventions to be made in the perioperative period to avoid these hemodynamic thresholds. Our experience is that patients with known coronary artery disease can safely undergo bariatric surgery without a major increase in perioperative mortality and cardiac complications provided a thorough preoperative cardiovascular evaluation has been completed.10 Many bariatric surgical candidates have OSA. Obesity is the most important cofactor contributing to the severity of this disorder.11 Although OSA is prevalent in patients undergoing bariatric surgery, little evidence exists linking it with bariatric surgical morbidity and mortality.12-14 The American Society of Anesthesiologists endorsed practice parameters for the perioperative assessment and management of patients with OSA15 but recognized the insufficient evidence in the medical literature linking OSA with perioperative complications. Therefore, a reasonable approach for patients with established OSA being treated with continuous positive airway pressure (CPAP) is to continue using CPAP throughout the perioperative period of any surgical procedure, particularly when sleep is likely (eg, in the recovery room or at night). Sleep studies S26

Mayo Clin Proc.

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and CPAP therapy should be pursued in individuals with clinically important symptoms associated with OSA who might benefit from CPAP therapy independent of any anticipated surgery. THE ROLE OF OBESITY IN PERIOPERATIVE RISKS PULMONARY SYSTEM The greatest perioperative concern in caring for patients with extreme obesity is the respiratory system. Fortunately, thorough preoperative evaluations have resulted in better identification and initiation of therapy for OSA and reactive airway disease, as well as treatment to help patients stop smoking. Preoperative interventions designed to optimize pulmonary function may modify the physiologic effects of obesity on the pulmonary system during the perioperative period. In obese patients, particular concerns are decreased chest wall and lung compliance, increased airway resistance, lower expiratory reserve volumes, and decreased functional residual capacity.4,16-18 Conversely, the negative effect of chest wall and abdominal adipose tissue on lung compliance, functional residual capacity, and blood oxygenation is exacerbated by position changes from upright to supine and further worsened with initiation of general anesthesia and mechanical ventilation. After awake positioning of the obese patient to optimize tracheal intubation, preoxygenation and intubation are performed with the patient in a 25° reverse Trendelenburg position. Dixon et al19 showed that this head-up position was associated with greater lung volumes, a reduced tendency for atelectasis and intrapulmonary shunting, and a 23% increase in mean arterial oxygen tensions. Using this position, a more prolonged apneic period was necessary before oxygen saturations declined to 92% when compared to similar patients anesthetized in the supine position. These authors also noted that once mechanical ventilation was initiated, no advantage for oxygenation in the head-up position could be shown. These findings are consistent with observations in both normal-weight and obese patients reported by Sprung et al20,21 that arterial oxygen tensions during laparoscopy could be improved only with higher inspired oxygen fractions, not with patient position or mechanical ventilation parameters (positive end-expiratory pressures, tidal volumes, or respiratory rates). FLUID MANAGEMENT Perioperative intravenous fluid therapy influences cardiac and pulmonary function postoperatively, but no evidencebased studies have detailed the most prudent method for fluid replacement in patients with extreme obesity undergoing bariatric surgery. Recently, Nisanevich et al22 reported that both restrictive fluid therapy (4 mL/kg per hour)


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and liberal fluid therapy (a bolus of 10 mL/kg followed by 12 mL/kg per hour) were associated with decreased oxygen saturations on the third postoperative day, but this detrimental effect did not differ between the 2 regimens. Our approach to fluid management during bariatric procedures has evolved to more restricted fluid administration based on ideal rather than actual body weight. In our clinical experience, this approach appears to have reduced the incidence of postoperative pulmonary dysfunction, specifically hypoxia, and shortened hospital stays. Invasive monitoring of arterial blood pressure or central venous pressure during laparoscopic Roux-en-Y gastric bypass (RYGB) surgical procedures is uncommon. Patients arrive for bariatric surgery relatively euvolemic because preoperative bowel preparations are not used. Blood loss during bariatric surgery is minimal, particularly in relationship to the obese patient’s blood volume. Invasive arterial monitoring is reserved for patients undergoing open surgical procedures with epidural anesthesia, for those whose arm and forearm morphology prevents proper fit of blood pressure cuffs, in circumstances in which blood glucose samples are required to manage intravenous insulin therapy, or when underlying medical conditions warrant invasive cardiovascular monitoring. PNEUMOPERITONEUM The most clinically important hemodynamic consequence during laparoscopic RYGB occurs during abdominal insufflation. Establishing a pneumoperitoneum increases systemic vascular resistance, decreases cardiac index, and transiently increases mean arterial pressure.23,24 Patients with underlying cardiovascular dysfunction may have limited ability to tolerate these hemodynamic changes. Although infrequent, reflex bradycardia (a vagal response to peritoneal stretching during insufflation of the abdomen) and hypotension (a combined result of decreased venous return from the pneumoperitoneum and relative hypovolemia from steep reverse Trendelenburg positioning) may occur. Prompt release of abdominal pressure and a return to the supine position may be necessary. Intravenous fluid therapy (to improve cardiovascular preload) and administration of an anticholinergic agent (to counter increased vagal tone) usually allow subsequent abdominal insufflation without incident. Pneumoperitoneum may be responsible for transient intraoperative oliguria resulting from pressure compression of the renal cortex and inferior vena cava during laparoscopic procedures.25-28 Nguyen et al29 reported a 64% lower urinary output 1 hour after surgical incision in patients undergoing laparoscopic RYGB compared to similar patients undergoing open RYGB procedures. Urinary output in the laparoscopic group was less than that observed in Mayo Clin Proc.

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the open RYGB group throughout the procedure. Postoperatively, serum urea nitrogen and creatinine levels were not adversely affected. The reversibility of the relationship among pneumoperitoneum, renal cortex compression, and oliguria must be considered when making intraoperative decisions about fluid management. Additional fluid will not appreciably improve urinary output and may result in postoperative pulmonary complications. Impaired renal function after laparoscopy-induced oliguria during bariatric procedures has not been reported. ANESTHETIC CONSIDERATIONS Obesity may be associated with an increased risk of intraoperative awareness during general anesthesia. Once absorbed into the circulation by the lungs, the uptake of volatile anesthetic by various body tissues is influenced by tissue blood flow and body mass. Although blood flow to adipose tissue is only a small percentage of cardiac output, the capacity of fat for absorbing volatile anesthetics is substantial, particularly with lipid-soluble anesthetic agents in patients with increased stores of adipose tissue. This capacity for absorption of volatile anesthetic may contribute to a delay in reaching equilibrium between anesthetic uptake by the lungs and delivery to the brain.30 The use of less soluble volatile anesthetics (eg, desflurane or sevoflurane) allows faster times to steady state and reduces the influence of adipose volume.31 Patients anticipating bariatric surgery can be reassured that the risk of intraoperative awareness associated with bariatric procedures is not increased above the recognized baseline risk of 0.4% for all patients undergoing general anesthesia.32 PERIPHERAL NERVE INJURIES Peripheral nerve injuries represent the second most frequent cause of professional liability in anesthetic practice.33 Stretch injuries of the brachial plexus and compression of the ulnar nerve can result from excessive arm abduction, inadequate support of the outstretched arms, or prolonged flexion of the elbow.34,35 Warner et al36 assessed a single institution’s 35-year experience with perioperative ulnar neuropathy and found that 29% of patients with such injuries had a body mass index (BMI) (calculated as weight in kilograms divided by the square of height in meters) greater than 38 kg/m2, and 70% were male. Interestingly, ulnar neuropathies also occur in hospitalized nonsurgical patients, suggesting that patient positioning (eg, supine position, hands resting on chest or abdomen, or elbows resting on bed rails) also contributes to this condition.37 The combination of large BMI, male sex, and hospitalization for any reason places the patient at increased risk of ulnar neuropathies. Extended-width beds (to prevent arms from resting on side rails) and education (directed toward pa-


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tients, nurses, and physicians) about arm positions while the patient is in bed appear warranted. If postoperative polyneuropathies are discovered, malnutrition (particularly vitamin B deficiencies), rather than intraoperative positioning, should be thoroughly investigated.38 PERIOPERATIVE MORBIDITY AND MORTALITY Patients with extreme obesity have comorbidities that potentially influence the risks associated with any surgery. Complications unique to bariatric surgical procedures add to their surgical risk. In addition, both surgeon and facility expertise in bariatric procedures are important aspects that must be considered when referring patients for bariatric surgery. Each of these factors may contribute to perioperative morbidity and mortality in patients undergoing bariatric surgery. PATIENT FACTORS Obesity-related comorbidities (eg, diabetes mellitus, hypertension, OSA) increase the perioperative risks of pulmonary, cardiovascular, and thromboembolic complications associated with any surgical procedure. O‘Rourke et al12 and Fernandez et al13 retrospectively studied their individual practices for indicators of morbidity and mortality specifically related to bariatric surgery (both open and laparoscopic procedures). Age, sex, BMI, hypertension, diabetes mellitus, OSA, and obesity-hypoventilation syndrome were among the factors included in the analyses in one or both studies. In both studies, only age (>55 years) was found to be an independent patient-related risk factor for increased morbidity and mortality after bariatric surgery. Age was also cited as a significant risk for increased 30-day mortality in a study by Flum et al,14 who reviewed mortality after bariatric surgery in Medicare patients. These results suggest the importance of primary care interventions in identifying and stabilizing existing medical conditions before surgery, leaving only that which cannot be modified—age—as the greatest patient risk factor for bariatric surgery. CARDIOPULMONARY COMPLICATIONS Death immediately after bariatric surgery is rare, particularly death from myocardial infarction. The low death rate (100 procedures per year) compared to low-volume (