Guiding perioperative care for bariatric surgery

Sleep apnea, diabetes among special concerns.


During preoperative assessment for bariatric surgery, you discover that your patient, a 400-pound man, has dyspnea on exertion. Is this caused solely by his extra weight, or does he have an undiagnosed cardiac or lung problem that might affect the surgery's outcome?

Cause-and-effect questions like these pose diagnostic challenges for hospitalists involved in perioperative assessment of bariatric surgery patients. While there's no need to rewrite the guidelines for perioperative care in these cases, hospitalists need special expertise to help detect and prevent complications.

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“The preoperative look that we give to these patients is unique, as we are looking for different things than in the usual preoperative work-up,” said hospitalist Donna Mercado, FACP, director of the medical consultation program for Baystate Medical Center in Springfield, Mass. Obesity-related clinical issues that the hospitalists home in on include obesity hypoventilation syndrome, sleep apnea, cardiomyopathy of obesity and pulmonary hypertension.

Dr. Mercado and the hospitalist group evaluate about 80% of bariatric surgery candidates in a preoperative clinic and care for many of them in the postoperative period, working with surgeons to make sure that gastric bypass or laparoscopic banding is safe.

Pre-op concerns

Hospitalists should pay special attention to sleep apnea. Not only is the condition highly prevalent in bariatric patients, but it can worsen particularly on post-op day two or three, when changes in sleep architecture occur, Dr. Mercado cautioned. As a result, the patient can develop hypoxia or respiratory failure after surgery. Undiagnosed severe apneic spells can also cause cardiac ischemia or ventricular arrhythmias during sleep, she added.

The Baystate team uses the Epworth Sleepiness Scale to screen for obstructive sleep apnea preoperatively. The goal is to get patients with the condition stabilized on CPAP or BiPAP before surgery, Dr. Mercado explained. They also need CPAP or BiPAP masks applied in the recovery room and during both naps and nighttime sleep while in the hospital. These patients don't routinely have continuous oximetry checked unless their regular vital signs show they are developing low oxygen saturation, she said.

If Dr. Mercado suspects patients have undiagnosed sleep apnea but must have surgery, she puts them on continuous pulse oximetry during nighttime sleep to see if they need CPAP overnight. (Optimally, patients with sleep apnea should be diagnosed and treated before surgery.) She also screens patients with sleep apnea for co-existing obesity hypoventilation syndrome. Known to affect obese people, the syndrome can cause daytime hypoventilation and hypoxia—and can translate into higher risks of postoperative respiratory failure, which the hospitalist will have to monitor after surgery.

“We look preoperatively at the serum bicarbonate level,” Dr. Mercado said. A level of 27 or greater in a patient without other metabolic abnormalities implies he or she could be compensating for respiratory acidosis caused by hypoventilation and carbon dioxide retention, she added. If a patient being treated for sleep apnea still has a high serum bicarbonate level, hospitalists should order a CPAP titration study and arterial blood gases to evaluate inadequately controlled sleep apnea or obesity hypoventilation syndrome, as well as pulmonary function tests or a pulmonologist's evaluation to look for evidence of other pulmonary diseases.

Performing cardiac evaluations on bariatric patients also poses challenges. For example, patients may have trouble doing a standard stress test due to their weight. Stress echocardiograms with the use of ultrasound contrast agents don't provide good visualization, said Dr. Mercado, and the physician can also “see a lot of attenuation artifact on nuclear medicine images.” Thus, she said, the physician has to consider sending bariatric patients who have chest pressure, suspicious EKGs, or anginal symptoms on exertion for transesophageal echo (TEE) or straight to cardiac catheterization.

Patients scheduled for bariatric surgery also undergo psychiatric assessment screening to identify those who aren't good candidates psychologically, according to surgeon Peter F. Crookes, MD, director of the bariatric program at University of Southern California University Hospital in Los Angeles. For example, patients may have some psychological instability or unrealistic expectations about what the surgery will do for them, or they may have “no insight about what the operation will do and their responsibility in making lifestyle changes,” he said.

If a patient scheduled for gastric bypass is taking a long-acting antidepressant or other medication, such as an antihypertensive, Dr. Mercado recommended switching the person to a short-acting formulation. Otherwise, the person won't absorb the medication appropriately after the procedure, which is known to result in some intestinal malabsorption.

Post-op dangers

John Romanelli, MD, medical director of the bariatric surgery program at Baystate, notes that 1% of patients undergoing gastric bypass procedures will develop a leak that occurs at the connection between the stomach and intestine or between the intestines.

USC's Dr. Crookes adds that a leak can also occur after the lap band procedure if the surgeon accidentally puts a hole in the stomach, something that happens very rarely.

A fast heart rate can be the first sign of a leak or obstruction, said Mary Jane Reed, MD, a bariatric surgeon who is the surgical director of the Center for Nutrition and Weight Management at Geisinger Medical Center in Danville, Pa. She advises physicians to consider reoperation if a post-op bariatric patient has a persistent pulse of 120 beats/minute or greater without an obvious cause. Bariatric surgery often have little or no signs of intraabdominal catastrophe such as tenderness, guarding or rebound. The layer of subcutaneous adipose tissue is often thick and blunts the effect of the physical exam, Dr. Reed said.

At Baystate, hospitalists who note a change in the patient's clinical condition alert the surgical team “ASAP,” said Dr. Mercado. They also search for the medical cause of symptoms, such as tachycardia, tachypnea, upper abdominal or left shoulder pain, and hypotension, that could indicate anything from a leak to pulmonary embolism to sepsis or other problems.

A blood clot to the lungs is the second most common surgery-related complication, said USC's Dr. Crookes, although it occurs less than 1% of the time in bariatric undergoing the modern laparoscopic procedures. Even so, “it can creep up on you, and the next thing you know, you have a code blue,” he said.

Often, said Geisinger's Dr. Reed, a CT of the chest, abdomen and pelvis with IV contrast and oral contrast can help rule out pulmonary embolism and life-threatening injury. Given that the major anastomoses are more proximal, she added, you don't need to delay the CT scan just to try to make sure the contrast has gone through the entire bowel.

A negative imaging study doesn't completely exclude the possibility of a leak, however. As a routine safeguard, Baystate's Dr. Romanelli sends all patients who received gastric bypass for an upper GI study with contrast. But if a patient becomes sick postoperatively and has a negative upper GI study, he will still take the person back to the OR for a look to rule out a leak.

Baystate's hospitalists also help manage gastric bypass patients with type 2 diabetes who may experience a rapid and dramatic decline in need for oral diabetes medications and insulin after surgery. In fact, due to metabolic changes caused by the surgery, many patients can stop taking diabetes medications before leaving the hospital, according to Dr. Romanelli.

“A very well-known study at the University of Pittsburgh showed that 80% of [type 2] diabetics are off insulin within days or weeks [of gastric bypass],” he said. In contrast, he added, lap band surgery patients' need for diabetic medications diminishes as they lose weight over months or a year or two.

In caring for gastric bypass patients, Dr. Mercado generally reduces their insulin glargine or long-acting insulin dose by half on the day of surgery. She also holds their oral diabetes medications, and titrates their medications based on their blood sugar readings in the hospital. Patients receive instructions about what to do at home if their blood sugar runs over 200 mg/dL or under 100 mg/dL.

Hospitalists' involvement can provide an important partnership with bariatric surgeons for improving outcomes—-and patients' peace of mind, according to Dr. Mercado. “Patients express a high degree of satisfaction and comfort knowing that an internist is working with the surgeons to achieve a smooth post-op transition,” she said.