Bariatric Surgery


Bariatric surgery, or weight loss surgery, is any procedure intended to reduce weight in patients with morbid obesity. Bariatric, translated from Greek, literally means “weight medicine.” Bariatric surgery procedures are classified as restrictive (reduced stomach size; limiting the amount a patient may comfortably eat at any given time) or malabsorptive (alterations to the small intestine length to inhibit caloric absorption). Procedures may be restrictive (e.g., adjustable gastric band [or LAP-BAND®] or vertical sleeve gastrectomy [VSG]), malabsorptive (e.g., biliopancreatic diversion/duodenal switch [BPD-DS]), or both (e.g., Roux-en-Y gastric bypass [RYGB]).

Bariatric surgery centers utilize an interdisciplinary team to evaluate patients for suitability and educate them on the lifelong changes that must be implemented to be successful following surgery; patients must comply with strict dietary and exercise recommendations.

How to Use It

It is well established that surgery is often the only definitive treatment for patients with morbid obesity and is particularly effective for those patients who are 100 or more pounds overweight with comorbidities such as obstructive sleep apnea, diabetes mellitus, hypertension, and hyperlipidemia. Bariatric surgery is recommended in the American Diabetes Association guidelines for management of obesity in the treatment of type 2 diabetes mellitus (T2D).

How It Is Done

All bariatric surgeries are performed under general anesthesia using laparoscopic techniques. The VSG uses a linear stapling device along an esophageal dilator to remove and discard approximately 80% of the stomach. The remaining tubular gastric conduit is just slightly wider than the esophagus. The RYGB uses a linear stapler over a sizing balloon to create a small gastric pouch, approximately the size of an egg, that is separated from the remainder of the stomach. The remnant stomach remains in place. The duodenum is bypassed by creating an end-to-side jejunojejunostomy, and a Roux limb is anastomosed to the gastric pouch. This leaves a common channel of small bowel where food mixes with digestive juices and is absorbed into the blood circulation. Following either a VSG or RYGB, a 1- or 2-night stay is expected in the hospital. Fluoroscopic imaging using water-soluble contrast, rather than barium, may be performed during the hospitalization. Fig. 11.1 illustrates the major types of bariatric surgery.

Fig. 11.1

Major types of bariatric surgery. (A) Roux-en-Y gastric bypass. (B) Adjustable gastric band. (C) Sleeve gastrectomy. (D) Biliopancreatic diversion. (Reprinted with permission from Neff KJ, Olbers T, le Roux CW. Bariatric surgery: the challenges with candidate selection, individualizing treatment and clinical outcomes. BMC Med 2013;11:8.)


Patients with morbid obesity are afflicted with high recidivism rates following medical weight loss and diet programs. Bariatric surgery is highly effective at attaining substantial weight loss over the first 1–2 years postoperatively, but many studies have also proven that its effects are sustainable over a decade or longer. The measurement of percentage of excess body weight lost (%EBWL) is a standard metric monitored in multiple randomized controlled trials. RYGB patients average 59% EBWL and VSG patients average 53% EBWL at 10 years. Remission of T2D may occur within days of RYGB, and in both RYGB and VSG patients, a T2D remission rate of approximately 80% is common more than 10 years postoperatively. A substantial body of evidence has shown that surgery achieves superior glycemic control compared with lifestyle or medical interventions.


The VSG and RYGB are the most popular bariatric surgeries performed in the United States. The American Society of Metabolic and Bariatric Surgery estimates the number of procedures performed annually by using quality assurance data. In 2011, 158,000 surgeries were performed (17.8% VSG and 36.7% RYGB). The total number of surgeries continues to grow, with 252,000 performed in 2018 (61.4% VSG, 17.8% RYGB, 15.4% revision). The use of adjustable gastric bands continues to decrease, which has consistently been less than 5% since 2016, and the BPD-DS has been less than 1% since 2014. Some of the undesirable features of adjustable gastric bands are that patients may require surgery for removal in the event of band slip, dysphagia with or without distal esophageal dilation, or esophageal motility disorders.

Medication Implications


  • Patients are often required to follow a liquid diet for approximately 2 weeks to shrink the liver for better intraoperative exposure. This may result in patients being dehydrated the day of surgery.

  • Prophylaxis for venous thromboembolism (VTE) is recommended for all patients and typically consists of unfractionated heparin (UFH) or low-molecular-weight heparin (LMWH). Individual bariatric centers create specific protocols based on provider preferences and surgical training.


  • Patients should refrain from use of tobacco. Cessation of smoking is encouraged at least 6 weeks prior to surgery; however, some insurance companies may require cessation before that point. Cessation is important due to tobacco’s deleterious effects on wound healing, anastomotic ulcer development, and overall poor health.


  • The Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program (MBSAQIP) is the accrediting body for bariatric surgery centers. Each level of accredited centers performs within a certain facility volume, patient age range, and with specific required standards.

  • A multidisciplinary care team is essential to the care of patients receiving bariatric surgery, and this multidisciplinary team works with the program director to guide therapy and monitoring of patients within the center.

  • In addition to surgical teams, these may consist of mental health professionals, exercise physiologists, dietitians, bariatricians, internists, pharmacists, and nurses.


  • Many bariatric surgery programs have implemented Enhanced Recovery After Surgery (ERAS) protocols that include oral intake of a high-carbohydrate liquid the night before surgery and 2–4 hours prior to surgery. Antiemetics and multimodal pain medication regimens, including acetaminophen, gabapentin, celecoxib, scopolamine, and aprepitant, among other agents, are used to limit postoperative nausea and vomiting (PONV) and narcotic usage.

  • Use of ERAS has also been associated with decreased length of stay, with no difference in adverse effects.


Patients’ medication regimens may change drastically or very minimally

  • Medications for mental illness, seizures, thyroid conditions, and others where abrupt withdrawal will cause issues (e.g., beta blockers) are continued immediately postoperatively.

  • Medications that impact blood glucose, such as insulin or sulfonylureas, may be held with appropriate monitoring. Short-acting insulin is used commonly in the immediate postoperative period to control blood glucose, though at discharge from the surgical encounter, insulin may only be necessary for patients with insulin-dependent diabetes mellitus.

  • Some blood pressure agents (i.e., diuretics, angiotensin-converting enzyme inhibitors) are typically withheld to avoid dehydration or acute kidney injury immediately following surgery.


  • Patients are at increased risk of VTE following surgery and should receive VTE chemo-prophylaxis for a short period of time following surgery in addition to early ambulation and sequential compression devices. Risk calculators, such as one from the Cleveland Clinic, are available to assess the risk of VTE using patient-specific factors. As with preoperative VTE prophylaxis, dosing strategy following surgery is not universally recognized; provider discretion in collaboration with the patient’s primary care provider is common practice.

  • Patients require acid-suppression therapy, such as proton pump inhibitors, for at least 3 months following surgery to protect the anastomoses and staple line. Continuation of these after the 3-month period is dependent upon patient-specific factors, such as reflux.

  • Use of vitamins is critical to obtaining adequate vitamin and mineral levels following surgery. Vitamin and mineral levels should be monitored every 3, 6, or 12 months to ensure adequate nutrition and vitamin supplementation.


  • Some medications may increase the risk of complications in the postoperative period.

  • As examples, use of medications that decrease blood glucose levels should be avoided or have the dose reduced to avoid hypoglycemia; estrogen-containing medications may increase the risk of VTE and should be avoided, particularly in patients who have additional risk factors.

  • Nonsteroidal anti-inflammatory drugs (NSAIDs) should be completely avoided after bariatric surgery, if possible, because they have been implicated in the development of anastomotic ulcerations/perforations. Use of alternative medication classes, such as corticosteroids, may be substituted for NSAIDs if future diagnoses require, such as pericarditis or arthritis.


  • Vitamin deficiencies occur in bariatric surgery patients due to inherently low-caloric intake, alterations in gastric acid production and gastrointestinal (GI) transit time, bypassed portions of small bowel, and small intestinal bacterial overgrowth.

  • The most commonly deficient nutrients are fat-soluble vitamins or those normally absorbed by the bypassed duodenum. Patients must take supplemental folate, iron, calcium, in addition to vitamins B1 (thiamine), B12 (cyanocobalamin), A, and D.

  • There are commercially available over-the-counter preparations in doses appropriate for bariatric patients, or usual over-the-counter sources may be used in amounts greater than standard recommendations. For example, RYGB patients require a multivitamin with 200% of the recommended daily dose of nutrients.


  • Special attention to dosage forms is required following bariatric surgery. Alterations in gastric pH, time spent within the stomach, and specific location of absorption from the GI tract are critical elements that may alter how much of an oral medication is absorbed.

  • Surgeries that alter the length of the GI tract, such as RYGB, are likely to have a bigger impact upon the dosage forms used to deliver medication compared with restrictive procedures.

  • Patients requiring oral contrast following bariatric surgery require a lower volume with imaging performed more quickly than in nonbariatric surgery patients.


  • Oral birth control pills with estrogens require activation, via glucuronidation, through portal vein uptake before being returned to the GI tract via the bile duct. Nonoral forms, such as patches or intravaginal rings, may provide more consistent effects for patients following RYGB. Patches may not be as effective at weights greater than 90 kg, indicating that selection of an appropriate dosage form requires patient-specific considerations.

  • Extended-release (ER) or controlled-release (CD) diltiazem may not provide adequate rate, rhythm, or blood pressure coverage for patients following bariatric surgery due to the release point in the GI tract. Changes to GI tract length, such as with RYGB, may decrease absorption of ER diltiazem products, whereas an immediate-release (IR) product may provide optimal coverage, although it must be taken multiple times per day.

  • ER venlafaxine is available as a capsule that may be opened up and sprinkled onto a soft food, which is then swallowed whole, to increase the likelihood of absorption of the full dosage. Venlafaxine is also available as an IR tablet, but this must be taken multiple times per day to exert an effect similar to that of the ER tablet.

  • Opioids are available in multiple formulations; however, changing to a liquid may allow for a dose reduction and better pain control for a patient. The change to a liquid allows the medication to be more readily available for absorption, thus providing better pain relief. Caution should be used when changing opioids to a liquid formulation, as an unquantifiable increase in absorption has the risk of unexpected respiratory suppression; dose reductions should occur when changing formulations.


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Nov 21, 2021 | Posted by in PHARMACY | Comments Off on Bariatric Surgery

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