Bariatric Medicine in the ICU Part 1: Nutrition
Dr. James Bradley
There is currently a worldwide pandemic (besides COVID!) that deserves an equal amount of attention. Obesity has been increasing in prevalence throughout the world for several decades and the care of these patients is becoming increasingly complex. In 2005, it was estimated that obesity costs the US $147-210 billion per year and this likely has only increased.¹
In the PermiT trial, which examined the role of underfeeding vs targeted enteral feeding in critically ill patients admitted to the ICU between 2009-2014 in Saudi Arabia and Canada, the average BMI of patients was 29.² This is just one example that illustrates the prevalence of overweight and obese patients that physicians will be expected to care for in the ICU.
In the ICU, obesity is a well-recognized risk factor for complications, however its effect on mortality is more debatable in the literature. Although the importance of nutrition in the ICU is becoming increasingly recognized, it can be daunting. Several studies have shown that nutritional support in the ICU impacts ICU length of stay, duration of mechanical ventilation, ICU mortality, and hospital mortality. Obesity is a hyperinflammatory state, so when patients become sick, the synergistic effect produces a high catabolic rate which increases the risk of developing sarcopenia (muscle loss).
What is the best route of administration and what is the best way to give it?
The enteral route of nutrition is preferred for a variety of reasons. It is more cost-effective, there is maintenance of gut integrity, reduction of bacterial translocation, reduced stress ulcers, and modulation of the systemic immune response.³ When enteral nutrition is used, the ESPEN 2018 guidelines also strongly recommend using continuous rather than a bolus feeding regimen.⁴
When should it be started?
The 2013 ASPEN guidelines recommend that all critically ill patients who are obese should have a nutritional evaluation and support within 48 hours of admission to the ICU.⁵ In 2016, the ASPEN guidelines were updated and slightly more comprehensive.⁶ The new guidelines suggest using the NUTRIC score to assess all patients (regardless of BMI) admitted to the ICU to help determine which patients would benefit most from enteral nutrition. Additionally, the new guidelines recommend starting enteral nutrition within 24-48 hours of admission to the ICU for obese patients if the patient is unable to consume an adequate number of calories.
What is the best type of nutrition to provide?
A nutritional regimen consisting of a high-protein, hypo-caloric (60-70% of estimated caloric requirements) goal is the recommended strategy in obese patients in the ICU. Some common formulas that contain high protein include Fibersource and Nepro. A more comprehensive list of enteral nutrition formulas can be found through the ASPEN website.
How do I assess caloric requirements?
The most accurate method to evaluate caloric requirements is indirect calorimetry, however this is not always readily available in all medical centers. To circumvent this, there are a variety of equations that have been developed: Penn State, Ireton-Jones, Harris-Benedict, Swinamer, and Mifflin-St Jeor. Frankenfield et al extensively compared the different equations for assessing resting metabolic rate and found that the Penn State formula had the highest prediction accuracy with least bias in patients with BMI > 30. Kg/m2.⁷,⁸ In patients >60 years old, the modified Penn State formula was more accurate than the original Penn State Formula.⁹ The formulas are below for reference.
Penn State Formula
RMR (kcal/d) = MSJ(0.96) + Tmax(167) + VE(31) − 6212
Modified Penn State Formula
RMR (kcal/d) = MSJ(0.71) + Tmax(85) + VE(64) − 3085
MSJ = Mifflin−St Jeor equation
VE = minute ventilation (L/minute)
Tmax = maximum temperature in prior 24 hours in degrees C
Aside from the formulas previously mentioned, an alternative (and simpler) method to calculate the nutritional needs of patients has been provided in the 2018 ESPEN guidelines.
Provide 11-14 kcal/kg of current body weight per day for patient with BMI 30-50, OR
Provide 22-25 kcal/kg of ideal body weight per day for patients with BMI > 50.
Patients with BMI 30-40 should receive 2g/kg of ideal body weight per day as protein
Patients with BMI > 40, up to 2.5 g/kg ideal body weight per day of proteins is recommended.
Example Case & Calculations
A 78-year-old male with hx of CHF, COPD, and well-controlled type 2 diabetes mellitus presented to the ER due to worsening shortness of breath. His BMI is 47, he is 72 inches tall, and he weighs 158 kg (~350 lbs). He was placed on a non-rebreather and admitted to the ICU for respiratory distress after receiving IV antibiotics and fluids per sepsis protocol in the ER. Overnight, his respiratory status continued to worsen, and he required intubation. Chest x-ray from admission was concerning for bilateral multifocal pneumonia. His SOFA score is 10 and his APACHE II score is 28.
In this patient, his Nutric score is 8, which means he would benefit from aggressive nutrition. Because he is on mechanical ventilation, an NG tube should be placed, and enteral nutrition started within 24-48 hrs. Because his BMI is 42, he would require 14 kcal/kg x 158 kg = 2212 kcal per day. Based on his BMI, he would require between 2-2.5 g/kg ideal body weight per day of protein. His ideal body weight is 171 lbs or 78 kg, so he would need between 156-195 g of protein per day.
He was started on Fibersource HN with a goal rate of _92_
In conclusion, early nutrition is generally better and highly recommended by multiple medical societies. In the ICU, patients are at high risk for malnutrition, including patients with high BMI. Careful attention to nutritional requirements in all critically ill patients is warranted, and it can impact important clinical endpoints such as hospital length of stay, duration of mechanical ventilation, and mortality.
James Bradley, M.D.
Medical School: University of Louisville School of Medicine, Louisville, KY
Residency: University of Louisville Hospital, Louisville, KY
About James: Originally from eastern Kentucky, I moved to Louisville for medical school and married my wife. Since then, I have stayed here for residency and fellowship. My wife and I have three beautiful daughters and we enjoy taking them to the zoo, local farms, parks, and teaching them how to swim.
Research interests: Pneumonia, sepsis, shock, mechanical ventilation
References:
Pompilio CE, Pelosi P, Castro MG. The Bariatric Patient in the Intensive Care Unit: Pitfalls and Management. Curr Atheroscler Rep. 2016;18(9):55.
Arabi YM, Aldawood AS, Haddad SH, et al. Permissive Underfeeding or Standard Enteral Feeding in Critically Ill Adults. N Engl J Med. 2015;372(25):2398-2408.
Secombe P, Harley S, Chapman M, Aromataris E. Feeding the critically ill obese patient: a systematic review protocol. JBI Database System Rev Implement Rep. 2015;13(10):95-109.
Singer P, Blaser AR, Berger MM, et al. ESPEN guideline on clinical nutrition in the intensive care unit. Clin Nutr. 2019;38(1):48-79.
Choban P, Dickerson R, Malone A, Worthington P, Compher C. A.S.P.E.N. Clinical guidelines: nutrition support of hospitalized adult patients with obesity. JPEN J Parenter Enteral Nutr. 2013;37(6):714-744.
McClave SA, Taylor BE, Martindale RG, et al. Guidelines for the Provision and Assessment of Nutrition Support Therapy in the Adult Critically Ill Patient: Society of Critical Care Medicine (SCCM) and American Society for Parenteral and Enteral Nutrition (A.S.P.E.N.). JPEN J Parenter Enteral Nutr. 2016;40(2):159-211.
Frankenfield DC, Ashcraft CM, Galvan DA. Prediction of resting metabolic rate in critically ill patients at the extremes of body mass index. JPEN J Parenter Enteral Nutr. 2013;37(3):361-367.
Frankenfield DC, Coleman A, Alam S, Cooney RN. Analysis of estimation methods for resting metabolic rate in critically ill adults. JPEN J Parenter Enteral Nutr. 2009;33(1):27-36.
Frankenfield D. Validation of an equation for resting metabolic rate in older obese, critically ill patients. JPEN J Parenter Enteral Nutr. 2011;35(2):264-269.
