Question 29

You are tasked with developing a guideline for the post-operative ICU / HDU care of patients following bariatric surgery.
a)    How would you identify high risk patients who will require post-operative ICU / HDU admission? (30% marks)
b)    Discuss the important post-operative issues in these patients and their management.
(70% marks)

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College answer

Pre-op risk assessment 

  • Respiratory system evaluation            
  • Pulmonary hypertension
  • Sleep apnoea
  • Cardio-vascular evaluation and optimisation                    
  • Functional capacity 
  • Other considerations of relevance          
    • Diabetes, renal insufficiency, hiatus hernia, chronic pain and opioid tolerance issues, extreme weight


Post-operative ICU Management 

  • Monitored environment     
    • HDU, preferably in ICU with 1:1 nursing supervision 
    • Multi-specialty involvement with a shared mental model
  • Respiratory management      
    • Head end elevation and guard against aspiration
    • High risk of post-operative atelectasis
    • Extubation to NIPPV if appropriate
  • Fluid management       
    • Maintain intravascular volume fluid status while not causing edema of the anastomotic site due to excessive infusion, need for accurate monitoring of fluid status (invasive monitoring)
  • Renal issues     
    • Prone to rhabdomyolysis (prolonged surgery, steep trendelenberg position, high BMI)
    • High index of clinical suspicion (particularly if complaining of pain in the buttocks, hips or shoulders)
  • Hyper-coagulopathy and increased risk of venous thromboembolism    
  • Close monitoring of glycaemic status and variability (insulin resistance); thyroid profile     
  • Regular (rather than prn) anti emetics
  • analgesia – avoid opioids if possible
  • Early mobilisation and physiotherapy, close attention to ICU housekeeping issues (FASTHUGS etc.)     

Altered pharmacokinetic profile in morbidly obese patients needs careful consideration


The phrase "multi-specialty involvement with a shared mental model" sounds like something the candidates should memorise and deploy alongside phrases like "therapeutic alliance" and "client-centered healthcare". It almost belongs on the glossy brochure of a private obesity clinic. Looking beyond nauseating corporate slogans, there is wisdom here: the involvement of multiple teams is required for these high-risk patients to thrive. The best single guideline statement to read for this answer was probably Mechanick et al (2013).


Features of high-risk bariatric patients:  In discussing this, everybody seems to quote the 2010 study by Birkmeyer et al, who assessed the features associated with hospital complications of bariatric surgery among 15,275 Michigan residents. Another highly referenced publication is the LABS consortium paper in NEJM (2009). The following factors were found to be associated with an increased risk of serious complications:

  • Patient factors:
    • Cardiovascular disease (eg. ischaemic herat disease)
    • Smoking
    • Sleep apnoea
    • Age over 70 (though LABS did not find this was the case)
    • BMI over 70
    • Cirrhosis
    • End-stage renal failure
    • Immunosuppression
    • Impaired functional status
    • History of DVT or PE
  • Surgical factors:
    • Laparoscopic band patients are lower risk
    • Gastric bypass or sleeve gastrectomy patients were higher risk
      (all this may be because the laparoscopic surgery candidates had a lower BMI on average)

Pre-operative risk assessment for bariatric surgical patients should therefore consist of investigations which detect and (hopefully) modify some of these risks pre-operatively. Mechanick et al (2013) have an excellent preoperative checklist for this population (their Table 5), which is reproduced here with minimal modification:

  • Bloods: BSL, lipids, kidney function, liver profile, urine analysis, FBC, coags
  • Nutrient screening: iron studies, B12 and folic acid (RBC folate, homocysteine, methylmalonic acid optional), and 25‐vitamin D (vitamins A and E optional)
  • Cardiac evaluation: ECG, CXR, echocardiography, lower limb Dopplers 
  • GI evaluation: H.pylori screening, gallbladder evaluation, upper endoscopy if indicated
  • Endocrine evaluation: HBA1c, TSH, androgens with PCOS suspicion, cortisol levels (for Cushing disease)
  • Psychosocial‐behavioral evaluation: encourage patient to continue efforts for preoperative weight loss
  • Diabetes educator: optimize glycemic control
  • Smoking: cessation counseling

Post-operative management of bariatric surgery patients

An excellent article by Thornton et al (2017) is available for the paying customers of UpToDate. 

  • Disposition
    • 1:1  nursing is reasonable because:
      • the patient may still be ventilated
      • there may be unstable BSL which requires constant adjustment
      • there may be haemodynamic instability which requires constant vigilance
  • Extubation
    • ​​​​​​​One might summarise the extubation criteria for these patients as "crisp".  They need to be wide awake and completely cooperative, with full muscle power.
    • Re-intubation will be difficult due to what can be euphemistically be called "redundant oropharyngeal tissue". Approach to the cricothyroid membrane in an emergency may be impossible because of depth. 
  • Ventilation
    • ​​​​​​​Dose your tidal volumes to ideal body weight
    • Oesophageal manometry would be ideal to help quantify the contributions of the chest wall to total compliance, but it is unlikely to be available, particularly as the upper GI surgeon may be somewhat reluctant to place any devices in the recently instrumented upper GI tract.
    • The guidelines recommend something they describe as "aggressive perioperative pulmonary toilet", which sounds terrible but probably just means "frequent tracheal suctioning".
    • After extubation, a period of NIV may be useful
  • Vascular access and monitoring
    • PICC lines are usually suggested as a means of having convenient long-term IV access
    • Arterial lines are expected as a part of the management package, mainly because it is otherwise difficult to get blood from these people.
  • Sedation
    • ​​​​​​​No specific recommendations are available, but people seem to trend towards the use of dexmedetomidine as a co-analgesic and sedative
  • Analgesia
    • ​​​​​​​Because opiates are obviously bad for these people who are chronically at the brink of hypercapneic respiratory failure, generally regional techniques (such as thoracic epidural) are favoured
  • Electrolytes and endocronology
    • ​​​​​​​One should pay careful attention the the BSL of all ICU patients, and there is really nothing about these diabetics that might discriminate them from other critically ill diabetics.
    • If the patient has hypothyroidism, it is important to negotiate some strategy with the surgeon regarding oral thyroxine replacement (i.e. how long would they want the patient to remain fasted after the anastomosis).
  • Fluid management and renal monitoring
    • ​​​​​​​The college recommends caution with fluid resuscitation, so as to avoid making the anastomosis oedematous. This is of course completely at odds with the need to resuscitate them vigorously when you discover their rhabdomyolysis (Chakravartty et al, 2013). Older patients, those with long operations, high BMI, hypertension and those using statins are at higher risk. Apparently a CK rise over 1,000 IUs is relatively common, and is associated with an acute renal failure rate of 14%. If this develops, hospital mortality from this supposedly elective procedure increases to 25%. 
  • Diet and nutrition
    • ​​​​​​​Mechanick et al (2013) recommend a "low‐sugar clear liquid meal program" to commence after 24 hours, but this is obviously going to depend on the type of surgery and how many inadvertent enterotomies there were.
    • Vitamin supplementation should take place in patients with risky premorbid nutrition (i.e. just because they are obese does not mean they are not suffering from poor nutrition)
  • DVT prophylaxis
    • ​​​​​​​Low molecular weight heparin should probably be dosed to total body weight
  • Antibiotics
    • ​​​​​​​Are not indicated, except to prevent or manage recalcitrant thiamine deficiency (apparently upper GI bacterial overgrowth in these people can result in thiamine deficiency)


Bergeat, Damien, et al. "Postoperative outcomes of laparoscopic bariatric surgery in older obese patients: a matched case-control study." Obesity surgery 27.6 (2017): 1414-1422.

Birkmeyer, Nancy JO, et al. "Hospital complication rates with bariatric surgery in Michigan." Jama 304.4 (2010): 435-442.

Longitudinal Assessment of Bariatric Surgery (LABS) Consortium. "Perioperative safety in the longitudinal assessment of bariatric surgery." New England Journal of Medicine 361.5 (2009): 445-454.

Mechanick, Jeffrey I., et al. "Clinical practice guidelines for the perioperative nutritional, metabolic, and nonsurgical support of the bariatric surgery patient—2013 update: cosponsored by American Association of Clinical Endocrinologists, the Obesity Society, and American Society for Metabolic & Bariatric Surgery." Surgery for Obesity and Related Diseases 9.2 (2013): 159-191.

Thornton, Kevin, et al. "Bariatric surgery: Intensive care unit management of the complicated postoperative patient."

Chakravartty, Saurav, Diwakar R. Sarma, and Ameet G. Patel. "Rhabdomyolysis in bariatric surgery: a systematic review." Obesity surgery 23.8 (2013): 1333-1340.