10 Anesthesia for Minimally Invasive Bariatric Surgery

Abstract

Studies have shown significant positive outcomes of bariatric surgery, including resolution of commonly associated comorbidities such as diabetes and dyslipidemia. Bariatric surgeons should be aware of the significant challenges anesthesiologists face when caring for the obese patient, particularly during minimally invasive laparoscopic bariatric surgery. This chapter reviews the anesthetic concerns regarding and perioperative adaptations for the bariatric patient.

Review Questions and Answers

• 1. List four reasons why airway and ventilation are significant concerns for the anesthesiologist in minimally invasive bariatric surgery.

  • Bariatric patients have limited pulmonary reserve and will desaturate very quickly following induction of anesthesia.

  • Mask ventilation and intubation can be difficult in many bariatric patients due to alterations in body habitus.

  • Obese patients have impaired respiratory mechanics which can be worsened when under general anesthesia.

  • Many obese patients have obstructive sleep apnea (OSA), which can complicate the administration of anesthetic agents and postoperative pain management.

• 2. Your institution has purchased disposable foam positioning ramps for the operating room, one of which has been placed on the operating table. After the anesthesiologist intubates the patient with a video laryngoscope, you ask her and other operating room personnel to remove the ramp in order to position the patient supine for the procedure. The anesthesiologist asks that the ramp be kept nearby and be inserted underneath the patient at the end of the case. Explain her rationale.

  • Video laryngoscopes and other advanced airway equipment are often used when a difficult intubation is expected or when a rapid intubation is desired so that the patient is apneic for the least amount of time, both common in bariatric patients. One of the keys to optimize intubating conditions is positioning. A ramp can provide a head-up position that can be helpful for both preoxygenation/denitrogenation and positioning the patient’s head and neck into a hyperextended “sniffing” position for laryngoscopy. It would be helpful to replace the ramp underneath the patient at the end of the case and prior to extubation in the event that the patient fails to maintain adequate spontaneous ventilation after extubation and has to be reintubated urgently.

• 3. You are about to place the gastric band when the pneumoperitoneum appears to be inadequate. While the circulator checks the insufflation pressure, you ask your anesthesiologist to administer additional muscle relaxant. Your anesthesiologist replies that there is no twitch on the peripheral nerve monitor, and he wants to know approximate duration of the remainder of the case. Why does the anesthesiologist want to know this information?

  • “No twitch” implies greater than 95 % neuromuscular blockade. Administering additional muscle relaxant without a detected twitch on the train-of-four monitor is unlikely to detectably increase the depth of neuromuscular blockade. Administering neuromuscular reversal agents at this point will not result in adequate muscle strength for extubation. At least one twitch (85–90 % blockade) in train-of-four monitoring is needed for successful reversal of neuromuscular blockade. Your anesthesiologist would like to provide as much muscle relaxation as possible so that pneumoperitoneum can be maintained without losing the ability to successfully reverse the blockade when needed. Therefore depending on the type of muscle relaxant used, the known pharmacodynamics of the drug, the effects demonstrated thus far in this patient, and the duration of the case, your anesthesiologist may tell you that additional relaxant is not needed and that he would like to plan ahead for relaxant reversal later in the case.

• 4. Your bariatric patient has a diagnosis of OSA for which he uses a CPAP (continuous positive airway pressure) device, and has undergone a laparoscopic gastric bypass procedure about 2 h ago. Your assistant had written the patient’s admission orders. You are now informed by the recovery room nurse that the patient has significant pain not well controlled by the PCA (patient-controlled analgesia). His spouse had also forgotten to bring in his home CPAP device. He is on 2 L of oxygen by nasal cannula with an oxygen saturation of 95 %, and has had two episodes of apnea, both of which occurred when the he dozed off after receiving some intravenous hydromorphone bolus per the anesthesiologist’s order. You have reviewed your assistant’s order and note the PCA order to be intravenous hydromorphone 0.12 mg per bolus with a lockout interval of 6 min and a maximum dose of 1.2 mg/h. The nurse is wary of giving additional hydromorphone boluses because of the apneic episodes. What can be done to improve the patient’s analgesia?

  • The patient suffers from OSA and should resume CPAP therapy in the immediate postoperative period. You should order CPAP from the hospital’s respiratory service and try to obtain home CPAP settings for quicker titration. Patients with OSA are sensitive to opioids, and therefore intravenous opioid boluses may contribute to the apneic episodes. Once the CPAP therapy is initiated, one can increase dosage of the hydromorphone PCA bolus while the patient is continuously monitored in the recovery room. Once recovery room discharge criteria are met then the patient should be discharged to the ward with continuous pulse oximetry monitoring. The need for continuous pulse oximetry monitoring can be reassessed the following day. Non-opioid analgesics such as acetaminophen should be included in the pain regimen as well.