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.