Bariatrics rationale

Bariatric surgery is the only durable method to achieve sustained weight loss.

• Swedish Obesity Study showed an 18% weight loss over 15 years for surgical patients, compared to 1% weight loss for matched non-surgical patients (pre-semaglutide era)
• Surgical reduces appetite and hunger, whereas non-surgical weight loss leads to increased hunger and reduced energy expenditure and the weight goes back on.
• Once severely obese, the likelihood of reducing weight by dietary control alone is <3%. Most lifestyle interventions are completely ineffective.
• Improved mortality with surgery compared to controls

Mechanism of action

• Enteroencephalic endocrine axis
  • Interplay between GIT and brain to regulate food intake
  • Hypothalamus is the key area
  • NPY is the main hormonal signal regulating energy intake, which is modulated by hormones secreted by GIT cells, such as ghrelin and peptide YY
  • Ghrelin is secreted by fundus cells. It increases significantly before a meal and quickly diminishes post-prandially. Ghrelin stimulates synthesis of NPY, creating an orexigenic signal.
  • Most studies show that ghrelin levels fall significantly after LSG, but unclear after RYGB
• Enteroinsular endocrine axis
  • Action of gut hormones to induce insulin secretion and reduce glucagon secretion in response to food
  • Theoretically altered after bariatric surgery, as earlier arrival of carbohydrate loads in ileum stimulates peptides including GLP-1 and GIP
  • Incompletely understood

Improvements in comorbidities with weight loss

• >5% weight loss can improve morbidities, but need 10-15% to cure many disease processes
• Liver steatosis improved in 85% of patients by 6 months
• Lipid profile improved in 80% by 2 years, with a 50% 5-year remission rate
• HTN remission in 50%
• 10-year cardiac risk improved by 40%
• Incidence of PCOS decreased from 45% to 7% at 12 month follow-up, with improvements in fertility
  • Should be advised to use contraception post-op if premenopausal
• T2DM is better-controlled by surgery than medical therapy, with diabetes remission rate of around 40-60% at 2 years, although depends on procedure

Patient selection (NIH consensus statement 1991)

• Either
  • BMI > 40
  • BMI 35-40 + obesity-related complication
  • It has been suggested that BMI 30-35 + poorly-controlled T2DM (BMI as low as 27 in Asian ethnicity) should be considered, and outcomes are good
• Should demonstrate prior attempts at nonsurgical weight loss
• Realistic expectations and motivated attitude
• Austin criteria
  • Edmonton stage 1, 2 or 3
  • Attendance at group surgical information session, and pre-conditioning program/booklet
  • Previous clear and significant attempts at non-surgical weight loss
  • Age 18-65
  • BMI 35-40 with either EOSS 2 or 3 smaller comorbidities from EOSS stage 1
  • BMI 40-45 with EOSS 1 or greater (BMI 40-45 with no EOSS criteria should be referred to medical weight loss clinic)
  • BMI >45 with or without comorbidity
• TSC criteria:
  • BMI <48 for men and <52 for women
    • Women BMI >52 can sometimes be allowed after review by anaesthetist and ABG, 6 minute walk test, RFTs
  • Weight <160kg
  • No major cardiac/resp/renal comorbidities, or complex pain management
  • 1st revision surgeries are allowed, but should be done at start of week, and predicted uncomplicated

Contraindications

• Inability to comply
• Active alcohol or substance abuse
• Uncontrolled psychiatric disease including Prader-Willi syndrome
• End-stage organ dysfunction of the heart or lungs
• Inability to ambulate (won't recover during the rapid weight loss phase)
• Sabiston suggests that the upper limit of weight should be around 225kg
• Don't operate on teens until after major growth spurt (mid to late teens)
• Rough cut-off of 70yo for LSG and 65yo for RYGB

Operation selection:

• RYGB
  • GORD (mild GORD is ok for sleeve, technically reflux oesophagitis means RYGB is better)
  • Severe T2DM
  • BMI 40-55
• SG
  • Multiple and severe comorbidities
  • Multiple surgeries (mesh)
  • Prior EtOH abuse - increased risk of etoh abuse post-bypass
  • Risk of loss to F/U
  • BMI <40
  • BMI >55 (as part of a planned staged procedure with RYGB)
• Duodenal switch
  • Inadequate weight loss after a technically sound RYGB

Pre-op workup

• Endoscopy
  • Done in most patients - especially those with GORD
  • Should especially be done to look for signs of GORD, where there is suspicion
• Bloods
  • FBE, UEC, LFT, CMP, B12, folate, zinc, vitamin D, TFT, PTH, iron studies, lipids, HbA1c, CRP

Complications

• Early
  • Bleeding
  • Leak
  • DVT
• Long-term
  • Vitamins - B12, calcium, iron, vitamin D, protein deficiencies
  • B1 deficiency can occur with vomiting - extremity paraesthesias, confusion
  • Anastomotic stenosis - endoscopic dilatation
  • Internal hernias - often post-prandial cramping pain

SBO in LAGB patients can lead to a closed-loop obstruction, and they may not have vomiting - need to manage as per normal SBO but also deflate band. Not every band needs to come out.