Perioperative management - Mini Gastric Bypass / Omega loop gastric bypass

Surgical interventions, like all other therapeutic approaches for the treatment of obesity, do not address the root cause, as the actual cause of obesity is complex and still largely unknown. According to guidelines in developed countries, the indication for surgical intervention is given in the following cases:

BMI ≥ 40 kg/m², conservative treatment measures (nutritional, exercise, behavioral, and pharmacotherapy alone or in combination) have proven to be unsuccessful.

BMI ≥ 35 kg/m² with one or more obesity-associated comorbidities such as type 2 diabetes mellitus, coronary heart disease, heart failure, hyperlipidemia, arterial hypertension, nephropathy, obstructive sleep apnea 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, fertility restrictions, or polycystic ovary syndrome.

Primary indication without prior conservative therapy attempt:

• BMI ≥ 50 kg/m²
• Conservative therapy attempt is deemed unpromising or futile by the multidisciplinary team.
• In patients with particularly severe comorbidities that do not allow postponement of surgical intervention.

A primary indication in terms of metabolic surgery can be made with a BMI ≥ 40 kg/m² and coexisting type 2 diabetes mellitus, when the treatment goal is more focused on improving glycemic metabolism than on weight reduction. For these patients, proof of exhausted conservative therapy in terms of bariatric surgery is not required [American Diabetes Association 2017].

When choosing the procedure, the following parameters should be considered:

• the patient's initial weight (BMI)
• the expected weight loss (EWL)
• compliance
• the age
• a possible desire for children in women
• comorbidities (especially diabetes mellitus)
• the surgical risk

Other factors to consider are:

• gender
• occupation
• dietary habits

There is no universally recommended surgical procedure for all patients; rather, the choice of procedure should be individually tailored to the medical, psychosocial, and general life circumstances of the patient.

All procedures should ideally be performed laparoscopically.

The Mini Gastric Bypass (MGB) is also known as a single anastomosis bypass. Its advantage is a procedure with gastroenterostomy as the only anastomosis, eliminating all complications related to the foot-point anastomosis.

The Mini Gastric Bypass, abbreviated MGB, is considered a safe and effective procedure in bariatric and metabolic surgery. The principle of MGB is the formation of a long lesser curvature gastric pouch combined with a biliary small intestine loop, the length of which can vary. Typically, it measures 200 cm from the Treitz ligament to the gastrojejunostomy. Depending on the severity of obesity, longer biliary limbs (250-300 cm) are also chosen. For severe obesity, a length of 250 cm is recommended, for older patients and vegetarians a length of 180-200 cm, and for type 2 diabetics without massive obesity a length of 150 cm is recommended.

• Wasting diseases such as malignant neoplasms, untreated endocrine causes, chronic diseases that worsen due to a postoperative catabolic metabolism.
• Pregnancy
• Lack of compliance
• Unstable psychopathological conditions, untreated bulimia nervosa, active substance dependence.
• Diseases of the stomach and duodenum

Since bleeding in the remaining stomach cannot be treated endoscopically, there is a contraindication for patients

• with lifelong medication for blood thinning (Marcumar or ASA)
• with chronic need for pain medication (ulcerogenic)

A preoperative gastroscopy should be performed before all bariatric procedures to exclude relevant diseases of the esophagus or stomach, whose incidence is increased in obesity.

The following conditions should be considered and clarified and treated before surgery:

•         Reflux

•         Erosive gastritis

•         Helicobacter pylori infections

•         Barrett's esophagus

•         Esophageal carcinoma

•         Stomach tumors

•         Gastric and duodenal ulcers.

Risk evaluation is of high importance in obesity surgery. It includes, in addition to standard diagnostics (ECG, chest X-ray, laboratory), always a lung function test and assessment of nutritional status. 

Routine polysomnography is standard in US clinics, as 77 to 88% of patients there have sleep apnea.

• Preoperative therapy for Helicobacter pylori infection to prevent gastric/anastomotic ulcers
• Patient preparation begins before hospital admission with physical conditioning: smoking cessation, liquid diet at least 2 days before admission (ideally 2 weeks), and adjustment of medications that may increase risk (Metformin, oral anticoagulants, etc.).
• Bowel preparation is also recommended when performing gastric bypass. 
• General hygienic requirements in preparation do not differ significantly from other procedures. Intertriginous skin fold infections and acute inflammatory leg ulcers or diabetes-related changes in the lower extremity should be particularly noted. 
• Pharmacological thrombosis prophylaxis begins on the day of surgery and is dosed according to body weight.

The information must be particularly comprehensive, as it is an elective procedure. This includes capturing the general surgical risks of laparoscopy and conversion to laparotomy, as well as highlighting the specific risks. The intraoperative risks, short- and long-term consequences, up to transfusion and mortality risk, should be explained.

In general, it is a major procedure with many potential complications, even if the approach is only minimally invasive (laparoscopy).

General Complications:

• Infection (including hepatitis), especially blood transfusions and transfusions of blood components
• Thrombosis and embolism
• Bleeding requiring blood transfusions
• Wound healing disorders
• Nerve injuries
• Skin and tissue damage from electric current, heat, and/or disinfectants. These damages are rare and usually resolve on their own.
• Allergies and hypersensitivities (e.g., to medications, disinfectants, latex)
• Injuries to the throat and esophagus when inserting the gastric tube
• Injuries to the urethra and bladder from inserting a urinary catheter
• Positioning injuries to nerves or soft tissues with sensory disturbances and very rarely paralysis of the arms and legs. The risk is significantly higher in extremely overweight individuals than in those of normal weight.
• Gas insufflation during laparoscopic surgery can cause a feeling of pressure and shoulder pain. These, like skin crepitus, quickly subside. If the gas enters the pleural cavity (pneumothorax), it may be necessary to insert a chest drain.
• Numbness of the skin in the area of the surgical scars may remain.
• In some patients, the skin reacts with excessive scar formation (keloid) due to wound healing disorders or predisposition, which can be painful and aesthetically disturbing.

Specific Complications:

• A later reversal of the operation (reconnection of the stomach) is practically no longer possible or only possible with a high surgical risk.
• The remaining stomach can no longer be examined (endoscopy) and endoscopic treatment of bile duct stones (ERCP) is no longer possible in the conventional way.
• Injury to the stomach, esophagus, and other organs such as the spleen and pancreas is possible.
• If the spleen is injured, the organ may also need to be removed, resulting in increased susceptibility to infection later.
• If there are leaks in the sutures/seams, peritonitis may occur, necessitating reoperation.
• A change in procedure (from laparoscopic to open surgery) is possible if complications arise or if continuing the videoendoscopic operation is associated with too high a risk; the decision rests with the surgeon.
• Previous surgeries in the abdominal cavity increase the surgical risk and difficulty. In particular, previous surgeries in the left upper abdomen (stomach, diaphragmatic hernia, ...) complicate the procedure.
• After the operation, internal hernia incarcerations, adhesions, bowel obstructions, abscesses (pus collections), narrowing of the stomach-intestine connection, and ulcers can occur in the immediate postoperative phase as well as later after months and years.
• Sometimes, after an abdominal incision operation, a scar hernia (hernia) occurs, which usually needs to be surgically closed. This can also occur in the area of a trocar in laparoscopic operations.
• If the abdominal suture breaks open along its entire length after open surgery (burst abdomen), reoperation is unavoidable.
• Long-term consequences can include vitamin and iron deficiencies, short bowel syndrome, and a disturbance in calcium metabolism with consequences of osteoporosis.
• In planned pregnancy, increased vitamin supplementation is required, as otherwise malformations may occur. Contraception is no longer guaranteed in malabsorptive procedures.
• The success of the treatment and the avoidance of complications depend on the patient's cooperation. There is a need to adhere to 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 reduced weight loss.