Perioperative management - Mini gastric bypass / omega loop gastric bypass

Like all other therapeutic approaches for the treatment of obesity, surgical measures do not address the root cause, as the actual cause aetiology of obesity is complex and still largely unknown. According to the guidelines in developed countries, a surgical procedure is indicated in the following cases:

BMI ≥40 kg/m², conservative therapeutic management (nutritional, exercise, behavioural, and pharmacological therapy alone or in combination) has proved to be unsuccessful.

BMI ≥ 35 kg/m² with one or more obesity-related concomitant diseases such as type 2 diabetes mellitus, coronary artery disease, heart failure, hyperlipidemia, arterial hypertension, nephropathy, obstructive sleep apnoea syndrome, obesity hypoventilation syndrome, Pickwick syndrome, non-alcoholic fatty liver or non-alcoholic steatohepatitis, gastroesophageal reflux disease, asthma, chronic venous insufficiency, urinary incontinence, immobilizing joint disease, impaired fertility, or polycystic ovarian syndrome.

Primary indication without prior conservative therapeutic trial:

• BMI ≥ 50 kg/m
• The multispecialty team considers a non-surgical therapeutic trial as not promising or futile.
• In patients with especially severe concomitant and secondary diseases that do not permitting any delay in a surgical procedure.

Metabolic surgery may be primarily indicated in patients with BMI ≥ 40 kg/m² and comorbid type 2 diabetes mellitus if improvement of glycemic control is more important than weight loss. In these patients, the indication for bariatric surgery does not require evidence that conservative management has been exhausted [American Diabetes Association, 2017].

The following parameters should be considered when selecting the technique:

• the patient’s baseline weight (BMI)
• the expected weight loss (EWL)
• compliance
• age
• childbearing potential in women
• concomitant diseases (especially diabetes mellitus)
• the surgical risk

Other factors are included:

• gender
• profession
• dietary habits

There is no surgical procedure that can be generally recommended for all patients; instead the selection of the procedure should be selected based individually on the patient’s medical, psychosocial, and personal situation.

All procedures should ideally be performed laparoscopically.

Mini gastric bypass (MGB) is also known as a single anastomosis bypass. Its advantage is a procedure with gastroenterostomy as the only anastomosis. This eliminates all complications related to the enterostomy between the afferent and efferent limbs.

In MGB, a long gastric pouch fashioned from the lesser curvature is anastomosed with a biliary loop of the small intestine, the length of which may vary. Normally, it is the length from the ligament of Treitz to the gastrojejunostomy, equivalent to 200 cm. Depending on the severity of the obesity, longer biliary limbs (250-300  cm) may also be chosen. A length of 250  cm is recommended for patients with severe obesity, a length of 180–200 cm for older patients and vegetarians, and a length of 150 cm for type 2 diabetics without massive obesity.

• Consumptive diseases such as cancer, untreated endocrine causes, chronic diseases that would worsen as a result of a postoperative catabolic metabolic state.
• Pregnancy
• Poor compliance
• Unstable psychopathological conditions, untreated bulimia nervosa, active substance dependence
• Gastric and duodenal disorders

Since bleeding cannot be treated endoscopically in the gastric remnant, the procedure is contraindicated in patients with

• lifelong anticoagulant medications (phenprocoumon or ASA)
• chronic need for analgesics (ulcerogenic)

A preoperative gastroscopy should be performed prior to all bariatric procedures to rule out relevant esophageal or gastric disorders, which have an increased incidence in patients with obesity.

The following diseases should be considered, and treated prior to surgery:

• Reflux
• Erosive gastritis
• Helicobacter pylori infection
• Barret's esophagus
• Eesophageal cancer
• Gastric tumors
• Gastric and duodenal ulcers.

Risk evaluation is of significant importance in bariatric surgery. In addition to the standard diagnostics (ECG, chest radiographs, laboratory test panels), it always includes pulmonary function testing and recording assessment of the nutritional status. 

Polysomnography is part of the routine diagnostic work-up in US hospitals, where between 77 and 88% of patients suffer from sleep apnoea.

• Preoperative treatment of Helicobacter pylori infection to prevent gastric/anastomotic ulcers
• Patient preparation begins even before hospitalization with physical conditioning: No smoking cessation, liquid diet for at least 2 days prior to admission (ideally 2 weeks), and adjustment of medications that might increase the risk (metformin, oral anticoagulants, etc.).
• Bowel preparation is also recommended when gastric bypass is performed. 
• General hygiene requirements in the preparation do not differ significantly from those for other procedures. Intertriginous skin fold lesions and acute inflammatory crural ulcers or diabetic changes of the legs require special attention. 
• Pharmacological thrombosis prophylaxis starts on the day of surgery and is dosed according to the patient body weight.

Informed consent must be particularly thorough because this is an elective procedure. In addition to explaining the general surgical risks during laparoscopy and conversion to laparotomy, this includes pointing out the special risks. The intraoperative risks as well as short- and long-term outcome, including transfusion and mortality risk, should be explained. 

Even though the approach is minimally invasive (laparoscopy), it generally is a major surgery with numerous potential complications.

General complications: 

• Infection (including hepatitis), especially blood transfusions of blood and transfusions of blood components
• Thrombosis and embolisms,
• Hemorrhage requiring blood transfusions
• Secondary healing
• Nerve damage
• Skin and tissue injuries caused by electrical current, heat, and/or disinfectants. These injuries are rare and usually resolve on their own. 
• Allergies and hypersensitivities (e.g., to medications, disinfectants, latex) 
• Injuries to the pharynx and/or esophagus during insertion of the gastric tube 
• Injuries to the urethra and bladder during insertion of a urinary catheter 
• Positional injuries to nerves or soft tissues with sensitivity disorders or impairment and, very rarely, paralysis of the arms and legs. The risk is significantly higher in extremely overweight patients than in normal-weight individuals. 
• As a result of gas insufflation during laparoscopic surgery a sensation of pressure and shoulder pain can occur. These symptoms, as well as crackling of the skin, resolve rapidly. If the gas enters the pleural space (pneumothorax), it might be necessary to place a chest drain tube.
• Permanent numbness of the skin may persist in the region around the surgical incisions.
• In some patients with secondary healing or genetic predisposition, the skin reacts with excessive scar formation (keloid); such scars can be painful and disfiguring.

Special complications:

• Later conversion of the operation (reconnection of the stomach) is in fact no longer or only possible with a high operative risk.
• The gastric remnant can no longer be accessed endoscopically, and conventional endoscopic treatment of gallstones management (ERCP) in the conventional manner is no longer possible.
• Injury to the stomach, esophagus, and other organs such as the spleen and pancreas are possible.
• Splenic injury may also necessitate splenectomy, which can subsequently result in susceptibility to infection. 
• In case of suture leaks (leakages), peritonitis can occur with the need for another surgery.
• A switch in procedure (from laparoscopic surgery to open surgery) is possible if complications occur or continuation of the video endoscopic surgery is associated with excessive risk; the decision will be made by the surgeon. 
• Previous intra-abdominal surgeries increase the surgical risk and the level of difficulty. In particular, previous surgery in the left upper abdomen quadrant (stomach, diaphragm, …) complicates the procedure.
• After surgery, strangulated internal hernias, adhesions, bowel obstructions, abscesses, stenosis of the gastroenterostomy, and ulcers may develop in the immediate postoperative phase as well as later after months and years.
• Sometimes, laparotomy will result in incisional hernia, which usually requires surgical repair. This may also occur at the trocar sites during laparoscopic surgery. 
• If the abdominal sutures dehisce over their entire length after open surgery (burst abdomen), another surgery is unavoidable. 
• Long-term sequelae may include symptoms of vitamin and iron deficiency, short bowel symptoms, and impaired calcium metabolism leading to osteoporosis.
• In planned pregnancy increased vitamin supplementation is required because otherwise malformations may develop. Contraception is no longer ensured with malabsorptive procedures. 
• Treatment success and avoidance of complications depend on the patient’s cooperation. It is necessary to comply with eating habits and follow-up examinations. Failure to comply with the prescribed rules (number of meals, small portions, food selection) can lead to problems and less weight loss. 

 Since gastric bypass is a procedure that can only be performed by laparoscopy or laparotomy, this procedure mandates general anesthesia with capnoperitoneum.. For obese patients, endoscope assisted intubation must generally be available. 

Ileus positioning:
Maximal relaxation is required throughout the entire operation to assure maximum range of motion in the surgical field, which is already constricted by the abdominal and visceral fat. The anesthetist should also keep in mind that increased ventilatory pressures may be needed because of the anti-Trendelenburg position of the patient, possibly and might necessitate PEEP ventilation.

Central venous catheter (CVC):
In high-volume centers, CVC can usually be omitted, because CVC placement in extremely obese patients has its own morbidity. By contrast, in low-volume centers with longer operating times, a CVC is recommended. CVCs provide safe postoperative access for the critical first 24–28 hours, given the poor peripheral venous situation of most patients. These CVCs may also be placed “peripherally” into the brachial or radial veins to avoid the risk of pneumothorax.

Gastric tube:
The procedure requires an intraoperative gastric tube, which will have to be moved as instructed by the surgeon when fashioning the anastomosis. This requires absolute coordination via the laparoscopy monitor, as the gastric tube must be carefully advanced across the fashioned anastomosis without risking perforation. After fashioning of the anastomosis, a leak test with methylene blue should be performed. In this regard as well here, too, close coordination with the surgeon is needed mandatory. After anastomotic leak testing, inadvertent suture fixation should be ruled out by moving the tube. If necessary, the tube can be left in place through the anastomosis for up to 24 hours. However, in most cases, the gastric tube can generally be carefully removed after the anastomotic leak testing. Overly rapid withdrawal must be avoided, as inadvertent suture fixation of the tube can lead to perforation or rupture of the anastomosis.

The patient is positioned in the anti-Trendelenburg position on a surgical table approved for the patient’s weight. This table should also include side extensions for very wide broad patients. The video monitors are set up over the patient’s shoulders to the left and right side. Both arms are abducted and the legs are spread.

The surgeon is positioned on the right side of the patient. The camera assistant initially stands between the patient’s legs. The instrument handler scrub nurse stands to the left of the patient.

Once the gastric pouch has been fashioned, identifying the ligament of Treitz and measuring the loop of the small intestine requires that the camera assistant also moves to the right of the patient, but to the left of the surgeon, i.e., directly caudal of the right arm, which is abducted at a 90-degree angle.

• Basic laparoscopy set
• One 5- mm trocar
• Four 12 -mm trocars 
• Ultrasonic or electrothermal bipolar sealing hemostasis systems for dissection and tissue division
• An HRF device generator
• Laparoscopic staplers in various strengths sizes (black to gold/yellow)
• Atraumatic intestinal grasping forceps 
• Laparoscopic needle holder
• Calibration tube probe (30 French)
• The use of an angled 30° optic laparoscope is recommended.
• High-volume insufflators
• Fixation arm for the liver retractor is optional

Intravenous standard medications without ulcerogenic potential usually suffice.
Follow this link to Prospect (Procedures Specific Postoperative Pain Management)
Follow this link to the current German guideline Behandlung akuter perioperativer und posttraumatischer Schmerzen [Treatment of acute perioperative and posttraumatic pain].

Postoperative care:

• Postoperative monitoring: Since tachycardia sometimes is the only sign of significant problems in these patients, postoperative monitoring in intermediate or intensive care unit is recommended.
• Bronchopulmonary hygiene: A high incidence of atelectasis and low oxygen saturation necessitates frequent pulmonary hygiene in this group of patients. 
• Upper GI series with Gastrografin swallow: An upper GI series with Gastrografin may be performed on postoperative day 2. Once anastomotic failure or stenosis has been ruled out, the nasoenteric tube can be removed. Some centers do not routinely take radiographs and others do not leave the gastric tube in place postoperatively without any negative effects being observed. 
• Proton pump inhibitors for 1–3 months to lifelong (if there are risk factors or a history of ulcers) and nicotine smoking cessation to avoid anastomotic ulcers.
• Vitamin and mineral substitution: Since certain vitamins might no longer be sufficiently absorbed in adequate amounts, vitamin D, vitamin B12, and iron, in particular, might need to be supplemented lifelong. Vitamin supplementation is started after the 3rd  postoperative week. This consists of a daily dose of multivitamin tablets, 100  mg of vitamin B12, and calcium in the form of a supplement. Iron supplementation is recommended, especially for menstruating women.
• Consistent modification of eating habits to avoid symptomatic dumping symptoms. Eating Meal frequency should be increased, while the size of the meal portions and the percentage of high-energy-dense foods should be reduced. Drinking fluids should be avoided at meals and for up to 2 hours postprandially.
• Exercise: Motivation for prolonged exercise optimizes weight loss and stabilizes it in the long term run. Walking, bicycling, or aerobic exercise should be done for at least 30 minutes 5 times a week. Unless there is no secondary healing, muscle-building weight training for the upper body is recommended after the 6th postoperative week. 
• Follow-up examinations: All patients will undergo follow-up examinations at 3-month intervals during the first year to review appropriate dietary and exercise behaviors. After that, at least once a year for an undetermined period of time so that malnutrition and deficiencies can be recognized early and counteracted. Continuous monitoring by a nutritionist is reasonable to prevent vitamin, mineral, and protein deficiencies and even a fluid deficit. Monitoring of parathyroid hormone, calcium, and vitamin D3 is also important to prevent osteomalacia.
• Cosmetic correctional aesthetic/plastic surgeries.

Deep venous thrombosis prophylaxis: 

Venous thromboembolisms with resulting pulmonary embolisms poses a high postoperative risk, especially obesity paired with a major bariatric surgical procedure.

Although the current guidelines classify the risk of thrombosis as moderate, most centers regard that risk as high.

The 2010 NICE guidelines recommend the following recommendations:

• Each bariatric patient without an increased risk of bleeding should receive pharmacological thrombosis prophylaxis with weight-adapted low-molecular-weight heparin. The reported risk of bleeding is 1.8% higher during thrombosis prophylaxis.
• Mechanical thrombosis prophylaxis with anti-thrombosis-compression stockings should be started at the time of admission. Intraoperative pneumatic compression boots are recommended.
• Thrombosis prophylaxis should be continued until the patient is no longer any relevant immobility bedridden, usually until the postoperative day 5–7.

Note: Renal function, HIT II (history, platelet check). Follow this link to the current German guideline Leitlinie Prophylaxe der venösen Thromboembolie [Guideline on prophylaxis in venous thromboembolism].

Ambulation: 

Starts already on the evening of surgery; increasing ambulation is encouraged but lifting objects weighing heavier than around 3  kg should be avoided until 6 weeks after surgery. 

Physical therapy: 

Prophylactic respiratory therapy for pneumonia, if needed

Diet: 

On the 2second postoperative day, it is possible to gradually return to a normal diet, starting with water (<30 ml/h). Once the patient tolerates sips of water, the amount of fluid consumed is increased to up to 60  ml/h, and he receives 60 ml of a standard enteral nutrient solution with the flavor of the patient's choice 3three times a day. Patients are advised to avoid solid food for the time being.  Drinks rich in carbohydrates are generally outdated. Medications may only be taken in the form of powders or solutions. Four weeks after surgery, a gradual transition can finally be made from soft to solid food. This should be started with cooked chicken or fish. Meat might not be tolerated at all for a certain period of time. Patients should be advised to chew their food for a long time and to pause between each bite. When they feel full, they should stop eating. 

Bowel movement: 

In the immediate postoperative phase, both constipation and diarrhea may occur in patients. This can usually be treated conservatively. In some patients, lactose intolerance can occasionally be unmasked. The deciding factor here is sufficient fluid intake by the patient. Persistent diarrhea with severe bloating may be signs that the oral fat intake is too high. Occasionally, transient abnormal bacterial colonization of the intestine also occurs, which usually normalizes after a return to normal eating behavior. Consistent aftercare follow-up by a trained nutritionist is advisable.

Work disability: 

In principle, the patient can be discharged on the 3rd-5th postoperative day, if a sufficient amount of fluids is consumed.