Hospital Care of the Patient with Super Obesity (Kirchner, 11/11/2020)

Thanks to Dr. Julia Kirchner for a great Grand Rounds presentation this week on Super Obesity. Dr. Kirchner walked us through the myriad of ways in morbid and super obesity add physiological complexities to patient care and can seriously affect patient outcomes. The list of acute and chronic health implications of obesity is long, and the physiology is dense but also very interesting! In addition, don't forget the role that our explicit and implicit biases play into our care of obese patients.

For clarity, definitions of obesity:

Overweight: BMI >25-29.0

Obesity: BMI >30

Morbid or Extreme Obesity:  BMI >40

Super Obesity: BMI >50

• 9.2% of US population is severely obese
• Super obese is the fastest growing subgroup (maybe up to 1% of the population)
• Morbidly obese patients have increased ICU length of stay, with particularly well documented increased morbidity and mortality in obese trauma patients 
• In obese trauma patients: OR 1.4 mortality OR 1.8 in hospital complications (pneumonia, ARDS, UTI)
• Having a pulmonary diagnosis on admission increases with increasing BMI, and there is an increased need for non-invasive mechanical ventilation (NIMV)

Transport and transfer issues:

• stretchers with higher weight limits
• bariatric wheelchairs
• lift team
• adequate O2 for transport
• staff capability and training

Hospital Capacity issues:

• bariatric beds
• room layouts (doorways, hallways)
• bedside commodes, walkers
• lift equipment
• larger BP cuff (see Table 3), gowns, larger NIMV masks, longer needles
• imaging capabilities
• staff training

Physical Exam of obese patients, can be challenging: including heart and lung auscultation, abdominal exam and skin survey

Labs: 

• Obese patient tend to have higher baseline CO2
• We should use a higher BNP cutoff >54 (for BMI >40)
• Be aware of possibly inaccurate SCr (consider using a GFR calculator)

Imaging capabilities are often limited: 500lb weight max on CT scanner (30 inch maximum circumference), also higher rates of uninterpretable CXR (see image), challenges with ultrasound (difficult FAST exam, may need TEE)

Medications may need dosing modifications based on several factors, including weight, type of medication distribution, and renal and hepatic metabolism. Here is a link to a calculator for body weight calculations: idea/actual body weight and this is a really great resource for medication dosing in obesity called ClinCalc.

Okay, now for some serious physiology and pathophysiology

Respiratory issues are a BIG deal in the care of morbidly obese patients. Predisposing factors that make obese patients at risk for respiratory distress include: underlying chronic respiratory failure (that is why that elevated baseline CO2), difficulty with airway maintenance, higher baseline oxygen consumption, impaired central response to hypercapnia and hypoxia, and disordered gas exchange. 

• 42% of morbidly obese patients will require NIMV regardless of reason for admission
• AVOID SUPINE position (exacerbates everything), consider HOB elevated vs. reverse trendelenberg
• high PEEP may be indicated (starting 10, up to 20-25)
• care with fluids

Obesity hypoventilation is super common and important in our care of morbidly obese patients!

• BMI>30
• daytime hypercapnea (pCO2>45)
• disordered breathing during sleep
• all other dx excluded

Cardiac complications and Renal complications are common. Often these are acute on chronic. Take home points:

• Care with IV Fluids
• Consider ADJUSTED weight based dosing of IV fluids
• Have high suspicion for underlying renal and cardiac disease that may be undiagnosed but is very likely present. 
• care with nephrotoxic drugs
• low threshold for telemetry monitoring

lCVD=cardiovascular disease, IAP=intra-abdominal pressure, RV=right ventricle, LV=Left ventricle,

AKI=acute kidney injury, CO=carbon dioxide, AKI=acute kidney injury

And finally, how we treat patients matters!

Bias and Obesity:

"Weight appears to be the last acceptable bias", Rita Rubin writes in JAMA, article available here. The general population AND physicians show very high anti-fat bias and there is clear evidence of bias and discrimination against obese patients. There is an intersectionality with race and racism in this country that we need to be aware of, as there are higher rates of obesity in Hispanic and Black populations.  

T"Weightake home