Anesthesia for Bariatric Surgery

Introduction

• Bariatric and metabolic surgery refers to surgical procedures performed to achieve weight loss and reduce or resolve associated metabolic diseases.^1,2
• They are often performed via a minimally invasive approach, either laparoscopically or robot-assisted.
• Currently, the three most common weight-loss operations performed are sleeve gastrectomy, Roux-en-Y gastric bypass, and duodenal switch with biliopancreatic diversion^1-3 (Figure 1).
  • Each procedure entails its own risks, potential complications, and efficacy in promoting weight loss.
• Sleeve gastrectomy:
  • Performed by excluding the greater curvature of the stomach to reduce the gastric volume by about 80%.
  • Weight loss results from a combination of reduced food intake and hormonal changes, by removing the portion of the stomach that produces most of the “hunger hormone.”
  • Advantages: Effective weight loss and improvement in obesity-related conditions; shorter, simpler surgery; and suitability for patients with certain high-risk medical conditions.
  • Disadvantages: It can increase reflux symptoms and is often recommended for patients without reflux. It is a nonreversible procedure.
  • Potential complications: bleeding, perforation, or damage to surrounding structures.
• Roux-en-y gastric bypass
  • Performed by creating a gastric pouch and excluding the remainder of the stomach, which is not typically removed.²
  • Two limbs of the small intestine are created: an alimentary limb and a biliopancreatic limb, which is typically anastomosed approximately 130 cm distally to create a bowel connection resembling the letter Y.
  • The newly created stomach pouch is smaller and able to hold less food. Additionally, food does not come into contact with the first portion of the small intestine, resulting in decreased absorption. This has a profound effect on decreasing hunger and increasing fullness.
  • Advantages: Weight loss is typically more substantial, and this procedure is associated with a higher rate of resolution of diabetes mellitus (DM). The surgical technique has been revised and standardized.
  • Disadvantages: There is a higher risk of vitamin and micronutrient deficiencies. The excluded stomach is often not accessible for endoscopic intervention (gastroscopy), surveillance, or percutaneous endoscopic access.
    Avoiding nonsteroidal anti-inflammatory medications is recommended due to the risk of anastomotic marginal ulcers.
  • Potential complications: bleeding, gastric perforation, internal hernia, anastomotic stricture, anastomotic leak, and afferent limb syndrome.
• Duodenal switch with biliopancreatic diversion
  • Performed by creating a gastric pouch similar to sleeve gastrectomy, dividing the first portion of the duodenum, and creating an alimentary limb and a biliopancreatic limb.
  • The degree of malabsorption depends on the length of the common channel, which is typically 100 cm.
  • Results in the greatest degree of weight loss, but is associated with the highest risk of malnutrition.
  • Complications are similar to those of gastric bypass, including bleeding, perforation, and anastomotic leak, but with an increased risk of worsened acid reflux.^1-3
• Adjustable gastric band (Lap band)
  • Widely used previously but now performed less frequently due to less durable results and complications such as band migration and erosion.
  • In this procedure, the proximal stomach is mobilized, and a prosthetic band is secured around the top part of the stomach to limit the amount of food a person can eat. A subcutaneous pocket is used to accommodate the injection port. The band is then filled via the subcutaneous port.

Indications and Contraindications

• Current indications for weight loss surgery include
  • Body mass index (BMI) ≥35 with or without comorbidities such as hypertension, DM
  • BMI≥30 with significant obesity-related comorbidities.
  • Weight loss surgery is considered in carefully selected children and adolescents if BMI>120% of the 95th percentile with associated obesity-related comorbidities or BMI>140% of the 95th percentile without major comorbidities.
• Contraindications:
  • Absolute contraindications include inability to tolerate general anesthesia and unresolvable coagulopathy, limited life expectancy due to malignancy or irreversible end-organ failure such as cardiopulmonary disease, pregnancy, or anticipated pregnancy in 12 months.
  • Relative contraindications: active illicit substance or alcohol use, untreated severe psychiatric illness, and active, untreated peptic ulcer disease.⁵

Complications

• Complications of gastric banding procedures include erosion, migration, and less durable weight loss
• Sleeve gastrectomy:
  • Stable line leak, bleeding, worsened reflux, gastrogastric fistula
• Roux-en-Y gastric bypass and duodenal switch with biliopancreatic diversion:
  • Anastomotic leak, marginal ulcer, afferent limb syndrome
• Nutritional deficiencies and bariatric surgery:⁶
  • Iron deficiency results from decreased hydrochloric acid secretion and bypass of the duodenum and proximal jejunum, which are the predominant sites of iron absorption.
  • B12 deficiency occurs due to inadequate secretion of intrinsic factor, decreased acidity, and bypass of the duodenum, where pancreatic enzymes are needed for intrinsic factor binding of B12.
  • Folate deficiency can result from decreased dietary intake and B12 deficiency.
  • Calcium deficiency occurs due to bypass of the duodenum and proximal jejunum, primary sites of gastrointestinal absorption.
  • Fat-soluble vitamin deficiencies (vitamins A, D, E, and K) due to impaired intestinal absorption and enterohepatic circulation
  • Thiamine deficiency due to decreased absorption in the proximal jejunum
  • Vitamin C deficiency
  • Magnesium, zinc, copper, and selenium deficiency.

Preoperative Considerations

• Obesity presents both anatomical and physiological challenges concerning anesthesia.
• Associated medical comorbidities:^1,4,7
  • Obstructive sleep apnea
  • Pulmonary hypertension
  • Gastroesophageal reflux disease (GERD)
  • Hiatal hernia
  • DM
  • Gastroparesis
  • Hepatic steatosis/cirrhosis
  • Venous stasis
  • Deep vein thrombosis
  • Hypertension
  • Hyperlipidemia
  • Cerebrovascular disease
  • Coronary artery disease (CAD), congestive heart failure (CHF), arrhythmia, left ventricular hypertrophy (LVH), and diastolic dysfunction.
• Insulin resistance is common and often renders perioperative blood glucose more difficult to control.^1,4,7
• Pulmonary effects:^1,7
  • Decreased functional residual capacity, total lung volume, and increased closing capacity.
  • Leads to a ventilation-perfusion mismatch and a compensatory increase in respiratory rate.
  • Higher risk of respiratory suppression, so care should be taken when premedicating with benzodiazepines or opioids.
• Concomitant use of weight loss medications, such as GLP-1 agonists, is associated with a higher incidence of GERD, hiatal hernia, and gastroparesis.^1,8
  • A careful review of the medical history and medications should be performed. Gastric ultrasound may be useful for evaluating the volume and characteristics of gastric contents and for determining aspiration risk in some patients.
• Obesity and metabolic syndrome are associated with a higher risk of CAD, CHF, LVH, and other cardiac pathologies.
  • Careful preoperative screening for cardiac risk and appropriate diagnostic testing is required.
• Early recovery after surgery protocols are frequently employed.^1,9
  • These aim to reduce opioid induced constipation, nausea and vomiting, and immobility.
  • Careful attention to postoperative nausea and vomiting prophylaxis and multimodal analgesia, including regional anesthesia, is frequently employed.

Intraoperative Considerations

• Vascular access can be difficult in this patient population. Ultrasound is a helpful tool.
• Standard American Society of Anesthesiologists monitors should routinely be employed with invasive monitoring as indicated.
• The method of induction should be based on nil per os status, medical comorbidities, and consideration of medications taken and timing.
• Please see the OA summary on drug dosing in patients with pbesity for more details. Link
• Because of a higher body fat content, medications with higher lipophilicity will require a longer time to be cleared, including volatile agents with a higher oil:gas coefficient, such as isoflurane.^1,4,7
• Dosing medications may be based on total body weight (TBW), ideal body weight (IBW) or adjusted IBW (AIBW) (AIBW = IBW + 0.4(TBW – IBW).
  • Succinylcholine and sugammadex doses are typically based on TBW.
  • Rocuronium is often dosed by IBW.
  • Sedative medications, opioids, and infusions are often dosed by ideal or AIBW body weight and should be titrated up to the desired effect.^1,4,7
• These patients may require deep neuromuscular blockade to improve laparoscopic visualization.
• Frequently, esophageal bougies or orogastric tubes are placed for gastric decompression and to size the stomach during gastrectomy.
  • Communication between the surgical team, nursing, and anesthesia is essential.
  • Care must be taken to retract tubes at the surgeon’s request during stapling to avoid incorporation of a foreign device in the staple line.
  • Intraoperative esophagogastroduodenoscopy may also be used.
  • Paraesophageal hernia repair and dissection around the diaphragmatic crura may be performed. Pneumothorax and injury to the descending aorta or inferior vena cava are possible.
• Extremes of positioning, including lateral tilting and reverse Trendelenburg positioning, may be required.
  • The patent must be secured well.
  • Careful padding of bony prominences should be performed.^1,4,7
• Please see the OA summary on the perioperative care of the patient with obesity for more details. Link
• Obesity is a common risk factor for both difficult endotracheal intubation and difficult mask ventilation.
  • Careful airway examination should be performed, and appropriate measures taken if the patient is a potential difficult airway.
  • Ramping the patient and shoulder roll, video laryngoscopy, oral and nasal airways, and oxygen mask straps are some of the strategies commonly used.
  • Apnea tolerance is often decreased in these patients.
  • Passive oxygenation techniques and preoxygenation with noninvasive ventilation may be utilized to increase the time tolerated for intubation attempts.
• Reduced chest wall compliance due to body habitus may result in higher peak pressure, especially when the patient is flat or in Trendelenburg positioning.^1,4,7,8
• During emergence, good neuromuscular blockade reversal should be performed.
• Care should be taken when using respiratory-suppressing medications in the peri-extubation period.
• The patient should be positioned with the head of the bed elevated when feasible to reduce the risk of obstruction and improve chest wall compliance.
• Nasal and oral airways may be useful in the immediate postanesthesia period.
• Preparations should be made if the patient requires reintubation.^1,4,7

Postoperative Considerations

• These patients should be transported to the post-anesthesia care unit post-operatively and typically require inpatient or observation admission.
• Cautious use of opioids, benzodiazepines, and other respiratory drive-suppressing medications.^1,4,5
• Multimodal analgesia should be continued.
• Patients may be at risk of hypoventilation due to residual neuromuscular blockade or respiratory suppression from medications.
  • Supplemental oxygen may mask these effects.
• Patients are at risk for airway obstruction and atelectasis
  • Position in the head-up position
  • Consider the use of high flow nasal cannula, continuous positive airway pressure, or biphasic positive airway pressure as permitted by the surgeon.^1,4,7,8
• Postoperative nasogastric or orogastric tube manipulation or placement should be avoided unless discussed with and approved by the surgeon.