Postoperative Assessment and Management of Obesity Surgery

Technique or Treatment

When it comes to weight loss, therapy can be divided into either surgical or conservative treatments. The latter refers to behavioral modification in the form of increased physical activity and alterations in diet. While this usually leads to an average of 10% short-term weight loss, it is difficult for patients to maintain. Surgical weight loss has been defined as the most effective and long-lasting form of weight reduction.[2] According to the National Institutes of Health, candidates for bariatric surgery include those with a body mass index (BMI) greater than or equal to 40 or a BMI greater than or equal to 35 in the setting of comorbidities.[1] 

Surgical Obesity Treatment

There are different types of surgical obesity treatment: malabsorptive and restrictive procedures and a combination of both. Malabsorptive surgeries prevent the absorption of food and restrict work by reducing the volume of food intake due to early satiety.[3] The 4 most commonly performed bariatric surgeries include the adjustable gastric band (AGB), sleeve gastrectomy (SG), Roux-en-y gastric bypass (RYGB), and the biliopancreatic diversion (BPD), also known as the duodenal switch (DS).

AGB

The adjustable gastric band is typically performed laparoscopically. It is a restrictive procedure, meaning weight loss is induced by reducing the food taken at once.[4] While losing popularity, it is still appealing to some patients because it is reversible, and the band is easy to adjust for more (or less) weight loss. Patients request this surgery because there is no rearrangement of bowel anatomy nor cutting or dividing of the intestine. It has a low complication rate but is also found to have less successful long-term weight loss than other types of bariatric surgery. The surgery involves placing a band around the proximal stomach, approximately 2 cm below the esophagogastric junction, to create a small, approximately 15mL pouch.[3] The band is attached to a subcutaneous port placed on the anterior rectus sheath, inflating it like a balloon.[3][5] The goal is for patients to feel full sooner and longer due to decreased space for food and slower emptying. The desired weight loss is 1 to 2 pounds (0.5-1 kg) per week, and it can be titrated by filling (or emptying) the lap band around the proximal stomach.[4][5]

SG

Another bariatric surgery that falls into the restrictive category is sleeve gastrectomy.[4] It is performed laparoscopically, and due to its low rate of complications and reoperations, it is the most common bariatric surgery performed worldwide.[6] It is often the procedure of choice for high-risk patients with a BMI greater than 60 and may be done as a prequel to a DS or RYGB.[2] The surgical technique involves the removal of 80% of the stomach, starting at 4 to 6 cm from the pylorus and extending along the greater curvature to the angle of his.[5][6] The result is an approximately 100mL gastric tube allowing limitation of food intake with preservation of the pylorus—no anastomosis is required.[2][5][6]

RYGB

Combining both restrictive and malabsorptive aspects of weight loss surgery, RYGB is another common bariatric surgery. It involves the (laparoscopic) creation of a 20-30mL gastric pouch using the cardia of the stomach, separating it from the remaining stomach, pylorus, and proximal small bowel.[7] Measuring 40 cm from the ligament of Trietz, the jejunum is divided and brought up in an antecolic or retrocolic fashion and anastomosed to the stomach pouch. This alimentary or "roux" limb is then traced distally, 75 to 100 cm, where an entero-enterotomy is created between it and the biliopancreatic or "Y" limb that drains the proximal small bowel and accessory organs. After this, potential spaces within the mesentery are closed to prevent internal hernia.[8] 

BPD and DS

BPD and DS are less commonly performed bariatric surgeries that are a combination of restrictive and malabsorptive. These result in the greatest weight loss but also have the greatest postop mortality rate of 1.1%.[9][10] They are technically more challenging for the surgeon and may be performed open or laparoscopically. BPD begins with a distal gastrectomy and closure of the duodenal stump. The ileum is transected, brought up, and anastomosed to the stomach pouch as an alimentary/roux limb. An ileo-ileostomy is then formed between the alimentary ileal limb (approximately 250cm distal to the stomach) and the proximal ileum (continuous with biliary/pancreatic drainage), resulting in a 50- to 100-cm common channel before emptying into the colon. The duodenal switch begins similarly to a sleeve gastrectomy, forming a gastric pouch based on the lesser curvature. The duodenum is transected approximately 4 cm distal to the pylorus, and this is anastomosed to the ileal alimentary limb. Allowing approximately 250 cm of alimentary limb, an ileo-ileostomy is performed roughly 100 cm from the ileocecal valve, creating a common channel similar to BPD.

Postoperative Care Following Bariatric Surgery

The trend for bariatric surgeries has been to perform them laparoscopically as it is associated with decreased hospital length of stay, wound complications, post-op pain, and improved surgical cosmesis. Furthermore, laparoscopic surgery reduces the risk of post-op venous thromboembolism (VTE), which has been identified as a frequent cause of postoperative morbidity and mortality. With that being said, all patients are placed on an aggressive VTE prevention regimen following surgical intervention. Early ambulation (within 4-6 hours post-surgery), sequential compression devices (SCDs), and pre- and post-op low molecular weight or unfractionated heparin are essential.[11]

As far as oral intake is concerned, patients are typically started on a bariatric clear liquid diet within the first 24 hours post-op as long as they tolerate water and there are no clinical signs of staple line or anastomotic leak.[12] Once tolerating a low-fat, full-liquid diet and ambulatory, patients are discharged home with protein supplements, a vitamin regimen, and gradual progression in food consistency over the next several months. Outpatient follow-up typically involves post-op visits between 2 and 6 weeks and check-ups at 3 and 6 months. Subsequently, patients are examined bi-annually for 2 years and annually thereafter.[7] Patients are encouraged to increase physical activity once they have recovered from surgery, as this limits the loss of lean tissue, decreases the risk of regaining weight, and encourages cardiovascular health. Strength training and aerobic exercise are encouraged for at least 30 minutes daily, and increased activity is incorporated into daily behaviors.[4]

Nutritional Consequences of Bariatric Surgery

As patients continue to thrive at home following surgery, their diet is advanced to solids with a goal of approximately 1200 calories and 60-120 grams of protein per day. While protein malnutrition is rare following bariatric surgery (except BPD/DS), many patients experience intolerance to protein-dense foods and should be monitored for such. Vitamin supplementation is also recommended upon discharge, and patients are often provided multivitamin regimens, including additional iron, calcium, vitamin D, and vitamin B, with routine monitoring and further customization of supplements based on the patient’s labs and clinical status.[6] It is important to note that patients may also experience dietary complications such as dehydration, steatorrhea, dumping syndrome, and chronic nausea and vomiting as a consequence of the anatomic alterations seen with bariatric surgery.[5][12]

As mentioned previously, the vitamin deficiencies seen after weight loss surgery include iron (33% to 55% of patients), calcium and vitamin D (24% to 60%), vitamin B12 (24% to 70%), and thiamine (less than 5%). Following RYGB, the most frequent nutritional deficiency is iron and B12 depletion, seen in up to 60% and 70% of patients, respectively. Iron deficiency is due to the duodenum and proximal jejunum being bypassed, as they both serve as iron absorption sites. As for B12, it is typically absorbed within the terminal ileum after binding with intrinsic factor, a substance secreted by the parietal cells of the gastric antrum. Resecting the gastric antrum during RYGB delays mixing intrinsic factor and B12, resulting in poor absorption at the terminal ileum and deficiency.[7] Treatment of iron and B12 deficiencies includes oral supplementation, which may be escalated to the injectable or intravenous route if needed.[4][7]

Anatomically, restrictive procedures, such as SG, can put patients at higher risk for dehydration due to early satiety. As such, patients are instructed to take sips of liquids throughout the day. Regarding malabsorptive procedures, patients may have the unpleasant side effects of increased flatulence, bloating, and loose, foul-smelling stools due to fat and starch malabsorption.[12] These patients are also more likely to have fat-soluble vitamin deficiencies (Vitamin A deficiency in 69% of patients and vitamin D deficiency in 63%) and protein-calorie malnutrition—especially after BPD or DS. Overall, 30% of patients experience dumping syndrome, a form of rapid gastric emptying associated with RYGB and BPD that occurs secondary to high-sugar gastric content "dumping" into the small bowel associated with pyloric discontinuity. Blood is shunted to the mesentery as highly concentrated liquid enters the small bowel. Signs of dumping syndrome include nausea, abdominal discomfort, diarrhea, and vasomotor symptoms such as flushing, diaphoresis, and heart palpitations. Treatment involves diet modification with small frequent meals throughout the day, limiting liquids with meals, increasing fiber intake, and avoiding simple sugars. Lastly, roughly 4% of post-bariatric surgery patients experience frequent nausea and vomiting. In addition to being worked up for the possible anatomic cause of symptoms, patients should be monitored closely for signs of Wernicke encephalopathy (neuropathy, myopathy, encephalopathy), which occurs due to thiamine deficiency and can be treated with oral or intravenous replacement.

Anticipated Weight Loss

Following bariatric surgery, patients can expect to see the largest drop in weight within the first year, with the most rapid weight loss occurring within the first 3 months. It is common for patients to regain approximately 1/3 of their initial weight loss over the subsequent 2 to 6 years; however, weight typically stabilizes between 6-15 following surgery.[4]

In general, interventions that involve less GI tract rearrangement (ie, restrictive procedures) tend to result in less weight reduction; however, these patients also suffer fewer long-term and perioperative problems. Most weight is shed after BPD/DS, which boasts 83% of excess weight lost (EWL) at 3 years.[10] RYGB is runner-up with 77% EWL at one year and a 30-35% reduction in total body weight (TBW) at 1 to 3 years. While it is apparent that weight reduction is greater following malabsorptive procedures, SG still maintains an EWL of 57.6% at one year and 73.8% EWL overall.[2][4][6] As for AGB, while it is the least dangerous bariatric procedure, TBW at 3 years clocks in at only 15.9%.[5]

Complications

Despite the optimization of surgical technique and post-operative care, it is still imperative for physicians and surgeons to monitor bariatric patients for both medical and surgical complications and treat them accordingly. Overall 30-day mortality among all bariatric surgery patients is less than one percent, with restrictive procedures being 0.1%, RYGB 0.5%, and 1% for BPD/DS.[5] Serious complications are seen in roughly 4% of patients. They are more pronounced in patients with high BMI, history of VTE, obstructive sleep apnea (OSA), and inability to ambulate at least 200 feet in the pre-operative setting. Also, older patients who use tobacco and suffer from multiple comorbidities are more likely to have problems following surgery.[5] Nutrition complications aside, bariatric surgery has been associated with medical complications such as VTE (0.3%), marginal ulcers, cholelithiasis, nephrolithiasis, urinary tract (0.3%), and wound infections (0.5%). Surgical complications include a staple line or anastomotic leak (0.2%), bleeding (0.7%), intestinal obstruction or internal hernia, and anastomotic stenosis.[5][13]

As VTE is a common cause of morbidity and mortality following bariatric surgery (0.3% at 7 days and 2% at 180 days), it is important to note modifiable and nonmodifiable risk factors.[14] From a patient perspective, increased BMI and age (older than 50), male gender, smoking, or VTE history increases the risk.[11][14] Surgeons can prevent VTE in their patients by maintaining operative time of less than 3 hours, using minimally invasive techniques, and taking all measures possible to avoid staple line and anastomotic leaks and revisional surgery. When deciding on surgery,  it is important to note a higher association of VTE with malabsorptive procedures vs. restrictive.[11] Any patient with a suspected pulmonary embolism (ie, tachycardia or shortness of breath) should have a prompt CT scan and be anticoagulated if a pulmonary embolism is identified.[12]

From a surgical perspective, anastomotic or staple line leaks and bleeding have been identified as having the greatest association with sepsis, reoperation, and intensive care unit (ICU) admission.[13] A leak can be difficult to identify clinically as obese patients may not present with peritonitis or even fever, as would be expected of other patients. Sometimes, the only warning sign is tachycardia.[12] If suspected, investigation via CT must proceed immediately, as early intervention can save lives; however, routine imaging is not recommended if patients are free from symptoms.[15][12] Treatment includes operative or image-guided drainage, antibiotics, total parental nutrition (TPN), and endoscopic stenting across the leaking staple line.[2][12]

Internal hernias are identified in 1% to 3% of RYGB or BPD/DS patients and are more commonly seen after patients begin to lose weight.[12] Patients may present with postprandial abdominal discomfort associated with intermittent nausea/vomiting or with outright signs and symptoms of bowel obstruction. Diagnosis via CT or upper GI series demonstrates dilated bowel loops, mispositioning, and engorgement of mesenteric vessels. Internal hernias are noted within the transverse colon mesenteric defect in 69% of patients, between the mesentery of the roux limb and transverse mesocolon (aka Peterson defect) in 18%, at the entero-enterostomy mesenteric defect in 13%, and between raised loops of the small bowel.[1][12] Treatment includes prompt exploration (laparoscopic preferred) with a hernia reduction and closure of the defect. Unfortunately, 4.7% of these patients require bowel resection, and there is a 1.17% mortality associated with the diagnosis of internal hernia.      

Stenosis and marginal ulcers usually manifest at the gastroenteric anastomosis. Stenosis is seen greater than 30 days post-op, and patients present with epigastric pain and regurgitation. Diagnosis and treatment include endoscopy with balloon dilation of the anastomotic site.[12] Marginal ulcers may present with epigastric abdominal pain or hematemesis and are also diagnosed via endoscopy. Treatment includes proton pump inhibitors and avoidance of non-steroidal antiinflammatory drugs (NSAID).[4][12]

Complications Based on Type of Bariatric Surgery

Adjustable gastric band.

Examining the adjustable gastric band, it has the lowest rate of post-op morbidity and mortality of all bariatric surgeries. Its 30-day mortality is between 0% and 0.1%.[5][14] There is approximately a 1% risk of major complications if the procedure is performed laparoscopically, and, in the long term, there is a 2% rate of issues per year.[5] The most commonly seen problems involve erosion of the band into the gastric wall, port-related difficulties such as infection, and band slippage with herniation of the stomach, resulting in obstruction and esophageal dilation.[5] Band erosion is seen in 0.3 to 7% of patients and is diagnosed via upper endoscopy or upper gastrointestinal series. Treatment involves surgical removal of the band and repair of the stomach.[12]

Band slippage and subsequent gastric outlet obstruction are diagnosed in patients who have developed food intolerance or new/worsening reflux.[3] A plain X-ray reveals the band in a horizontal (10 o’clock to 4 o’clock) position or evidence of an obstruction on the upper GI study.[3][12] Treatment involves deflation of the band, insertion of a nasogastric tube with pouch decompression, and surgical removal of the band or replacement/repositioning. The latter method has been found effective in 89% of patients in short-term follow-up.[3] As previously mentioned, AGB has the lowest risk of post-op morbidity and mortality, including the smallest risk of venous thromboembolism (VTE).[11][14] Unfortunately, while AGB has the lowest morbidity and mortality, it also demonstrates the least long-term weight loss among all bariatric surgeries.[5]

Sleeve gastrectomy

As discussed, sleeve gastrectomy complications are rare, with a global rate of 7.7%.[2] The most feared impediments, other than death (30-day mortality is 0.5%), include staple line leak, bleeding, and sleeve narrowing or stenosis. Leaks are most commonly seen in the proximal third of the stomach near his angle at a frequency of roughly 3.3%.[2][12]

RYGB

Thirty-day post-op mortality for RYGB is 0.2% to 0.5%.[5][14] Of those deaths, VTE is found to be the cause in 20% to 30%, and it is seen in roughly 0.5% of post-op patients.  Other early complications of RYGB include anastomotic leak (1%) and cardiac event in 0.2% to 1% of patients.[12] Late surgical events are small bowel obstruction due to internal hernia (1% to 3%), stenosis of the gastro-jejunal anastomosis (3%-12% of patients), and marginal ulcers (0.5%=20%).[1][12] Laparoscopic RYGB, while preferred to open due to decreased risk for complications (4.8% in laparoscopic and 7.8% in the open), VTE, and mortality (0.2% for laparoscopic and 2% for open), does have a higher risk of internal hernia (2.5% risk) when compared to open.[1][5][11]

BPD/DS

BPD and DS are accompanied by the most weight loss but also by the highest metabolic morbidity and mortality rates.[5][9][10] The 30-day mortality has been cited at 1.1%, and major complications occur in approximately 3% of cases.[9][14] Depending on the technique, anastomotic leaks and strictures are seen in up to 2.6% and 10% of patients, respectively. Similar to RYGB, marginal ulcers are also associated with BPD but unlikely in DS due to pyloric preservation.[9]

Clinical Significance

After discussing the complications associated with bariatric surgery, the decision to proceed with surgical intervention may seem intimidating to patients. It is important to note that obesity is an independent risk factor for health conditions including stroke (CVA), coronary artery disease (CAD), OSA, hyperlipidemia (HLD), diabetes mellitus (DM), hypertension (HTN), degenerative joint disease, asthma, cancer, and depression.[10] Obesity is a major health concern worldwide and is associated with decreased life expectancy, quality of life, and higher healthcare costs.[6] Bariatric surgery is the most effective approach for weight loss and has been proven to reduce the severity of (or eliminate) many of the co-morbidities and causes of death associated with obesity.[5][6][11]

Improvement in comorbidities is noticed as early as 6 months following weight loss surgery/ Patients have improved longevity with an 80% drop in annual mortality and a 50% reduction in overall mortality.[10][16] Not only has the incidence of CVA and MI decreased, but OSA has also improved or resolved in 85.7% of patients. After BPD and DS, 99.1% of patients had improvement in HLD. All surgical patients demonstrated lower levels of low-density lipoprotein and triglycerides.[5][10] Recovery of Type 2 DM was also observed, and 76.8% of patients had complete resolution—again, more prominent following malabsorptive procedures. Furthermore, all surgical patients demonstrated improved blood pressure, and HTN was cured by 61.7%.[10]

Enhancing Healthcare Team Outcomes

Considering all the behavioral, bodily, and lifestyle changes associated with weight loss procedures, it is no surprise that the psychological care of a bariatric patient plays a major role in both the pre-and postoperative setting. Preop psychological evaluation is advised to ensure patients are prepared for such a dramatic undertaking. Patients suffering from a major depressive disorder, substance abuse, or binge eating disorder may require further psychiatric care or even be disqualified from surgery.[5] Once deemed emotionally prepared for surgery, patients are encouraged to attend support groups throughout the perioperative period.[4] 

Even considering the physical and emotional stress associated with bariatric surgery, most patients experience an improved quality of life by enriching their psychosocial functioning, mood, self-image, and perceived health. In addition, patients have superior mobility and reduced anxiety, which translates into expanded confidence and interaction with others, ultimately resulting in amplified productivity and economic opportunities.[4][10]

While bariatric surgery has known medical, surgical, and nutrition-related complications, it has been proven to positively affect patients' longevity, comorbidities, and quality of life. A team of surgeons, internists, dieticians, psychologists, and a strong emotional support group are essential for optimal outcomes following weight loss surgery. With close monitoring, surgical, medical, and nutritional complications can be identified and remedied with minimal sequelae. With continued psychological support, patients are prepared for lifestyle changes that aid in successful weight loss and improved confidence and productivity. If properly selected preoperatively and properly monitored postoperatively, bariatric patients surely reap the benefits of weight loss surgery.