Increased rates of obesity in patients in the intensive care unit (ICU) reflect increased rates of obesity in the US population: recent estimates suggest that > 30% of patients in the ICU are obese [Hogue CW et al. Intensive Care Med. 2009], with that number likely to rise as the obesity prevalence grows in the general population. Patients in the ICU who are obese are more likely to require mechanical ventilation and to have a longer ICU stay [Akinnusi ME et al. Crit Care Med. 2008; Oliveros H, Villamor E. Obesity (Silver Spring). 2008].

According to Stephen McClave, MD, University of Louisville, Louisville, Kentucky, USA, critically ill patients who are obese have different metabolic patterns than do their nonobese counterparts in that they mobilize more protein and less fat. This process can make it difficult for these patients to meet their protein needs unless they consume excess calories and carbohydrates, which can lead to hyperglycemia.

Dr McClave described the development of an industry-funded prospective observational study designed to evaluate the tolerance and safety of a liquid enteral formula developed especially for critically ill patients who are obese. The formula included 1.0 kcal/mL—37% calories from protein (as 100% whey hydrolysate) and 31% calories from carbohydrate—with the addition of medium-chain triglycerides, fish oil, and prebiotic fiber (Table 1). It was designed to meet previously established protein requirements for critically ill patients who are obese [McClave SA et al. JPEN J Parenter Enteral Nutr. 2009].

Twenty-nine patients from ICUs at 2 Kentucky hospitals were recruited for the study. Inclusion criteria were a body mass index (BMI) ≥ 30 and a need for enteral nutrition over at least 3 days. Because 13 patients were deemed ineligible, the analysis was completed on 16 patients. These 16 patients were split evenly between men and women, with a mean age of 50.9 years, a mean BMI of 38.8, and a mean Acute Physiology and Chronic Health Evaluation II score of 17.3. Of the 16 patients included in the analysis, 15 were ventilator dependent at the inception of the trial.

The patients received study formula for up to 10 days; by day 3, all patients had received 80% of their goal calories and 86% of their protein needs. Daily intake, tolerance, and safety data were collected and analyzed. Mean laboratory values were as follows: blood glucose, 142.8 mg/dL, with no episodes of hypoglycemia; blood urea nitrogen, 29.07 mg/dL; creatinine, 0.96 mg/dL; and ketones, 0.0 mg/dL.

Four patients experienced ≥ 3 liquid stools per day for partial duration of the study. No subjects had a gastric residual volume > 400 mL, and there were no episodes of vomiting. Only nitrogen balance results were conflicting and therefore discouraging, said Dr McClave; results could not be obtained for all patients, but positive nitrogen balance was recorded in 7 of the 16 patients and negative nitrogen balance in 3 of them.

Dr McClave presented data comparing this new formula with other enteral products currently available (Table 2) based on the nutrient needs for a female patient with a BMI of 60 and an ideal body weight of 136 lb. He concluded that this unique enteral formula was safe and well tolerated in critically ill patients with obesity. The design of this formula may facilitate improved glucose control and allow patients to achieve nitrogen balance without receiving excess calories.