There has been an increase in the number of bariatric procedures performed in the USA over the past 10 years. With improvement in surgical techniques and surgical experience, the 30-day inpatient mortality rate has declined to about 0.09–0.3 % [21, 66, 67]. The major complication rates following bariatric surgery are approximately 5–10 % and most common are venous thromboembolism and respiratory complications [68]. Patients who are at high risk for postoperative myocardial infarction should be monitored in an intensive care setting. High-risk features include age > 50, history of congestive heart failure, myocardial infarction, OSA, venous thromboembolism, metabolic syndrome, chronic respiratory failure, and pulmonary hypertension [69, 70].

Pulmonary embolism is by far the most common cause of mortality after bariatric surgery. Increased risk is seen in patients with a BMI > 60, severe venous stasis disease, and obesity hypoventilation syndrome [71]. Prophylaxis against deep venous thrombosis is recommended for all patients. Most physicians employ intermittent compression stockings or subcutaneous unfractionated heparin or low molecular weight heparin as mentioned in the previous section. Post hospital discharge, extended thromboprophylaxis may be considered depending on patient’s risk factors, activity level and risk of bleeding [72], and may help in reducing the incidence of venous thromboembolism after hospital discharge [73].

Pneumonia or aspiration can occur in 0.14–2.6 % of patients [68, 74]. Pulmonary complications can be prevented by use of incentive spirometry, early ambulation, and adequate pain control [75]. Studies have shown that CPAP can be used safely and does not cause an increased anastomotic leak rate [76]. CPAP can be used if clinically indicated and can improve oxygenation and reduce the rate of intubation [77].

Another serious postoperative complication is anastomotic or staple line leak . Leaks are the second most common cause of death following bariatric surgery, and account for 38 % of deaths after laparoscopic gastric bypass, and 12.5 % of deaths after open bypass [74]. Anastomotic leaks can lead to sepsis, organ failure, and death, and may be difficult to diagnose. The presence of tachycardia of > 120 beats/min, tachypnea, fever, or abdominal pain should prompt an evaluation [78, 79]. In the clinically stable patient, upper GI study or computed tomography may be considered for initial evaluation. Less severe cases can be managed with antibiotics and drainage; however, reoperation is necessary in some cases [80].

Rhabdomyolysis is a potential complication of surgical procedures in morbidly obese patients. Risks include BMI > 55 kg/m², prolonged operative time, and diabetic status [81–83]. Prevention can be implemented by adequate padding at pressure points and screening CK levels in high-risk patients [84].

Surgical site infections are another concern after bariatric surgery. They are more common after open procedures than those done laparoscopically (an incidence of 7 % vs. 3 %) [74, 85]. Patients should be managed with prophylactic antibiotics and drainage as needed. While wound infections rarely cause death, they cause significant morbidity and increase the length of hospital stay. Hyperglycemia is one of the risk factors for surgical site infection [86] and attempt should be made to control postoperative hyperglycemia.

Nutritional support after bariatric surgery is designed to ensure adequate hydration, promote wound healing, preserve lean body mass, and minimize GI distress. Careful counseling by a dietitian is critical for success. Usually, a protocol-derived nutritional program can be started within 24 h after surgery but the diet progression should be discussed with the surgeon and guided by the dietitian. The general progression of a patient’s diet after surgery includes five stages over two months after surgery. Patients will advance through stages 1 and 2 to stage 3 while in the hospital and will continue on stage 3 at home before being advanced to stages 4 and 5 after post op evaluation by their physician. The diet is advanced from only liquids to high-protein soft solids and then eventually to low-fat high-protein solid foods over the course of 2 months. Details of postoperative diet stages are in Table 10.2. Protein intake should be assessed and guided by the dietitian. Minimum protein intake of 60–90 g per day should be achieved to avoid loss of lean body mass [87, 88]. Protein intake is usually inadequate in the first 2 months after surgery; therefore, protein supplements such as protein powder are often advised to achieve optimal protein intake.

There are some general principles to help patients adjust to digestion with their new anatomy. Patients should chew food very thoroughly to facilitate swallowing and prevent vomiting. During the progression through early food stages, patients should not drink liquids at the same time as they are eating their regular small meals. It is common for patients to have difficulty tolerating several types of food during the first several months after surgery, most commonly dry meats, breads, pasta, milk, and nuts. Patients should keep a food log to help identify food intolerances and monitor compliance. Protein should be consumed at the onset of the meal and carbohydrate should come from nutrient-dense complex carbohydrates to avoid Dumping syndrome [89]. Dumping syndrome can occur after the Roux-en-Y gastric bypass due to the loss of the physiologic sphincter at the stomach outlet. If the patient consumes a bolus of high sugar or high fat food, its arrival into the small intestine will cause a release of gut hormones and an influx of intraluminal fluid. The patient may experience nausea, diarrhea, flushing, and palpitations. This syndrome can usually be managed with nutritional counseling.

Routine vitamin supplementation will vary from patient to patient, with the most important determinant being the type of surgery performed. Though the laparoscopic adjustable gastric banding does not generally cause vitamin or mineral malabsorption, the variety and amount of food intake are restricted. It is recommended to take a multivitamin to meet daily requirements for both vitamins and minerals. Those undergoing Roux-en-Y gastric bypass, biliopancreatic diversion or biliopancreatic with duodenal switch are at greater risk for nutritional deficiencies [90]. Routine nutrient supplementation is shown in Table 10.3.

All patients should be encouraged to consume 1–2 multivitamins per day after surgery depending on the type of procedure performed. Patients may initially tolerate two chewable children’s tablet more easily during the first 1–2 months after surgery. Most clinicians recommend routine supplementation with 1200–1500 mg of calcium per day. Calcium citrate tablets may be better absorbed than calcium carbonate tablets due to decrease in stomach acid. Most calcium tablets also contain vitamin D but this may not provide adequate supplementation. At least 3000 IU of vitamin D is required to get 25-vitamin D levels > 30 ng/ml. Some patients may require a much higher dose of vitamin D to achieve this level. It is estimated that 30–50 % of patients might develop B12 deficiency after gastric bypass if not supplemented beyond a multivitamin [91, 92]. Treatment with oral crystalline B12 at doses of at least 350 mcg per day has been shown to maintain normal plasma B12 levels [93]. Subcutaneous or intramuscular injections may be used in patients not responding to oral therapy. A multivitamin containing folate will generally provide sufficient folic acid after surgery [94]. Iron deficiency after gastric bypass is quite common especially in premenopausal women. Additional ferrous fumarate supplementation with 325 mg twice per day may be needed in menstruating women [95]. Vitamin C may also be used to facilitate absorption.

During the immediate postoperative period, obesity-related comorbidities may change dramatically and it is important to monitor closely. In addition, patients undergoing Roux-en-Y gastric bypass or other malabsorptive procedures may have a change in the bioavailability of a particular drug depending on its site of absorption. For example, extended release formulations should be changed to immediate release and given in the crushed form.

After bariatric surgery, patients demonstrate a dramatic change in insulin sensitivity and glucose tolerance. In the immediate postoperative period, the patient’s medications may need to undergo significant adjustment. Insulin secretagogues (sulfonylureas and meglitinides) should be discontinued and insulin dosage should be reduced due to risk of hypoglycemia. Insulin therapy can be used in hospitalized patients to obtain a premeal blood glucose target of less than 140 mg/dl and random blood glucose of less than 180 mg/dl [96]. Metformin may be used postoperatively once patient is able to tolerate fluids and diet but caution should be made in patients with reduced glomerular filtration rate (GFR) [97, 98]. Patients who are on insulin therapy are encouraged to monitor their blood sugar at home at least 3–4 times a day. The dosage of insulin should be titrated depending on patients’ blood sugar level. Recently, a simple scoring system (DiaRem score) has been developed as a tool to help predict the likelihood of diabetes remission after Roux-en-Y gastric bypass surgery by using four clinical parameters: insulin use, age, HbA1c concentration, and type of antidiabetic drugs [99].

Antihypertensive medications should be adjusted during perioperative period. Diuretics and angiotensin converting enzyme inhibitors should be withheld 24 h before surgery due to the risk of hypovolemia and electrolyte imbalance. They can be slowly restarted if clinically indicated. Beta-blockers should be continued throughout, if possible. Stopping beta-blockers abruptly may lead to withdrawal syndrome with tachycardia and rebound hypertension [100]. Beta-blockers have potential adverse metabolic effects on lipids and insulin sensitivity and can cause weight gain in some patients [101]. If a beta-blocker is no longer indicated, practitioner should consider tapering it off and switching to other antihypertensive agents.

The timing of visits with the medical practitioner depends upon the type of surgery, as well as the patient’s comorbidities and overall health. Initial follow-up would be at 2–6 weeks after surgery and then every 3–6 months interval [19, 102]. Patients with serious comorbidities or complications should be seen more frequently. After the first year, visits may be spaced out to every 6–12 months. All patients should be reminded that they must visit a medical practitioner at least annually to monitor for complications and nutritional deficiencies.

Generally, patients are able to start a walking exercise program within 1 week. Most patients should not do more vigorous exercise than walking until 6–12 weeks. Patients are encouraged to gradually increase their physical activity to a minimum of 150 min per week and to a goal of 300 min per week for aerobic physical activity , plus strength training 2–3 times per week [103].

It is recommended that patients be routinely screened for micronutrient deficiencies at 3, 6, and 12 months after surgery, and annually thereafter [19]. Suggested laboratory monitoring is shown in Table 10.4. Patients consuming a multivitamin after bariatric surgery generally maintain adequate levels of fat-soluble vitamins. There is currently insufficient evidence to support routine screening for essential fatty acid, vitamin E, or K deficiencies. Screening for vitamin A deficiency may be indicated in patients who have undergone a malabsorptive procedure and presenting with ocular symptoms.

Anemia should prompt an evaluation for nutritional deficiencies. Iron deficiency is common after bariatric surgery. Contributing factors include low intake of red meat, bypass of the duodenum and proximal jejunum where most of the absorption occurs, and a decrease in gastric acid needed for adequate iron absorption. Patients who remain iron deficient despite oral supplementation should undergo a work-up for gastrointestinal (GI) blood loss (including marginal ulceration), and be considered for intravenous (IV) iron therapy. Serum ferritin is the most sensitive marker of early iron deficiency [104] and should be included in routine screening.

Vitamin B12 deficiencies can occur after bariatric surgery procedures that bypass the lower stomach. The initiation of vitamin B12 supplementation within 6 months postoperatively is important. Signs and symptoms of vitamin B12 deficiency are pernicious anemia, neuropathy, depression, and dementia. When assessing B12 deficiency, levels of homocysteine and methylmalonic acid should also be obtained as these are more sensitive markers of B12 deficiency [105]. Treatment with oral crystalline B12 at 1000 mcg daily or B12 500 mcg intranasal weekly is recommended. If B12 sufficiency cannot be maintained by oral or intranasal routes, intramuscular or subcutaneous B12 1000 mcg every month to 1000–3000 mcg every 6–12 months is indicated.

Multivitamin supplements providing 400 mcg/day folate can effectively prevent the development of folate deficiency after bariatric surgery. Routine supplementation is recommended especially in women of childbearing age to reduce the risk of fetal neural tube defects.

Thiamine deficiency can occur as a result of bypass of the jejunum, where thiamine is primarily absorbed. Thiamine deficiency after gastric bypass is rare but should be considered in patients who have persistent vomiting or inadequate nutrient intake and it can occur around 6 weeks to 3 months after surgery. Empiric treatment should be considered in patients with rapid weight loss , intractable vomiting, alcohol use, neuropathy, encephalopathy or congestive heart failure. Early recognition and treatment is important to prevent devastating complications such as Wernicke–Korsakoff syndrome. Parenteral supplementation with thiamine 100 mg per day should be initiated in the patient with active neurological symptoms. Severe cases should be treated with IV thiamine 500 mg per day for 3–5 days, followed by 250 mg per day until resolution of symptoms [106–108]. After 7–14 days, one can switch to an oral supplement of 10 mg per day.

Oral calcium and vitamin D supplements are important for bone health and to prevent secondary hyperparathyroidism. Vitamin D malabsorption occurs after bariatric surgery and in some patients the doses of vitamin D supplement may need to be as high as 50,000 units 1–3 times weekly. Following bariatric surgery, there is a significant increase in markers of bone turnover associated with a decrease in bone mass and the degree of loss of bone mineral density is associated with the amount of weight loss [109]. Possible mechanisms are skeletal unloading and secondary hyperparathyroidism [35]. Because of the complexity of calcium and vitamin D regulation, it is recommended that several parameters of bone health be monitored, including parathyroid hormone, total calcium, albumin, 25-OH vitamin D, 24-h urine calcium and bone-specific alkaline phosphatase levels. Dual-energy X-ray absorptiometry (DXA) is indicated to monitor for osteoporosis at 2-year intervals especially in high risk groups such as postmenopausal women.

Some bariatric patients have been documented to have low levels of selenium, zinc, and copper. Of these, zinc deficiency may be the most common, particularly after malabsorptive procedure. Symptoms of zinc deficiency include impaired immune function, hair loss, pica, and rash. Unfortunately, zinc deficiency is difficult to diagnose as serum levels represent < 0.1 % of total zinc stores, and during periods of inflammation this level will be artificially low due to increased zinc uptake in the liver [110]. Practitioners should rely on the clinical picture and laboratory data to assess the need for supplemental zinc. Oral Zinc supplement of 15–20 mg per day or up to 60 mg per day in the setting of malabsorption is advised [111].

Clinically relevant deficiencies of selenium and copper are poorly studied and seem to be rare. Symptoms of copper deficiency such as peripheral neuropathy and myelopathy are often indistinguishable from those occurring with vitamin B₁₂deficiency. Low plasma copper concentration and ceruloplasmin activity can be helpful to make the diagnosis. Treatment with IV copper of 2.4 mg daily for 6 days, followed by weekly intravenous copper of 2.4 mg combined with oral supplementation of 8 mg copper/daily until normal copper levels in blood are achieved was suggested [50].

Despite routine multivitamins and minerals supplementation, nutritional deficiencies can still occur. This could be due to baseline nutritional status, adherence to supplementation, adequacy of dietary intake, and type of bariatric surgery [112]. Thiamine deficiency can occur as early as 2–3 months postoperative in patients with frequent vomiting. Iron deficiency and vitamin B12 deficiency can be seen at 6 and 12 months, respectively. Copper deficiency can be seen at 24 months following gastric bypass surgery [113]. A small study has shown reduced Zinc concentration at 12–18 months after gastric bypass surgery [114].

During routine follow-up visits, the practitioner should assess for resolution or improvement of patients’ comorbidities. Bariatric surgery has been shown to dramatically improve diabetes [115, 116] and more than 70 % of patients will be normoglycemic off medication 2 years after surgery [117]. Patients who were taking insulin prior to surgery should have their basal insulin dosage decreased by half and discontinued for low sugars. Patients taking prandial insulin should not resume this practice until postprandial glucose values rise above 150 mg/dl. The most important factor in assuring safety is frequent monitoring, and patients should check their blood sugar 3–4 times daily and if needed discuss these values several times per week with their clinician. Because of the risk of future diabetes, patients who have been weaned off all of their medications should be checked at regular intervals for recurrent hyperglycemia. It is unclear if patients who have had resolution of their diabetes should continue other aspects of preventative diabetic care.

Hypertension improves variably after bariatric surgery, but approximately 30 % of patients with prior hypertension will not require medication at 2 years postoperative [117]. The reduction in blood pressure can be seen as early as 1 week postoperative [118]. Antihypertensive medications should be adjusted and patients’ blood pressure should be monitored periodically. Use of diuretics should be cautious due to risk for dehydration and electrolyte abnormalities.

After bariatric surgery, patients can anticipate an improvement in total cholesterol, triglycerides, and HDL as early as 3 months postoperatively [119]. In the 6 months following surgery, a reduction of more than 15 % of total cholesterol and a triglyceride reduction of more than 50 % can be observed [120]. Patients should then have their cholesterol levels measured 3 months postoperatively and rechecked periodically. Statin use may be continued depending on patient’s cardiovascular risk factors and lipid level goals [121].

Patients with NAFLD generally see improvement following bariatric surgery. Weight loss after bariatric surgery in obese patients will decrease the grade of steatosis, hepatic inflammation, and even the fibrosis [122–124]. Patients with history of transaminitis should be followed with liver function tests periodically to ensure that the levels fall into normal range.

Over 75 % of patients with OSA can expect resolution or improvement of their disease following bariatric surgery [125]. At this time, there are no standing recommendations for discontinuation of CPAP therapy after bariatric surgery. However, it may be reasonable to seek repeat polysomnography after the patient has achieved 30 % loss of excess body weight [126].

Psychiatric medications may need to be continued postoperatively and the need for medications reassessed in conjunction with a psychiatrist. Weight loss after bariatric surgery increases fertility. Hormonal methods such as oral contraceptive pills may be less effective due to malabsorption and changes in sex hormone binding globulins [127]. Alternative methods should be discussed with a gynecologist. Weight-based dosing medications should be adjusted according to rapid changes in patient’s body weight postoperatively. In patients with hypothyroidism, dosage of levothyroxine replacement is related to the amount of lean body mass [128]. As the patient is losing weight after gastric bypass surgery, levothyroxine dosage should be decreased and TSH should be monitored every 2–3 months.

During the first 30 days after surgery, complications are usually related to the operative procedure. Patients experiencing severe vomiting, wound infections, and blood clots should be referred back to the surgical team. Complications beyond the first month will be discussed in more detail below.

Vomiting after bariatric surgery is multifactorial and occurs in most patients for the first several months. Patients will have to adjust to new eating habits with their new smaller stomach pouch. In our center, patients presenting to the emergency room with vomiting after bariatric surgery receive 100 mg of thiamine, 1 mg of folate, and 10 cc of liquid multivitamin in normal saline to prevent Wernicke–Korsakoff syndrome. Patients who continue to have severe vomiting, or persistent vomiting for longer than 6 months should undergo further work-up for obstruction, ulceration, stenosis, or dysmotility. Patients with bloating, abdominal pain and bleeding should be evaluated for marginal ulceration. If uncomplicated, marginal ulceration can usually be managed medically. Nonsteroidal anti-inflammatory drugs should not be used after bariatric surgery due to risk of ulcers. Gastric dumping occurs initially in patients who have had a Roux-en-Y gastric bypass from bypassing the gastric pylorus so food and nutrients will enter small intestine rapidly [129]. Abdominal pain and cramping, nausea, diarrhea, light-headedness, flushing, tachycardia, and syncope are symptoms indicative of dumping. Postprandial or reactive hypoglycemia can be part of “late dumping symptoms” due to rapid glucose absorption stimulating incretins and insulin secretion. Symptoms usually will be less prominent over time and patients are advised to eating small frequent meals, avoiding simple sugars, and increasing fiber and protein intake [130]. Postgastric bypass noninsulinoma pancreatogenous hypoglycemia syndrome (NIPHS) is very rare but several cases have been reported [131, 132]. If hypoglycemia persists despite dietary modification, patient should be referred to an endocrinologist for further evaluation.