Feeding patients in the pediatric ICU (PICU) requires a delicate balance between minimizing protein catabolism and meeting energy requirements, according to presentations at the 2017 annual meeting of the Society of Critical Care Medicine.
“Globally, about a third of patients being admitted to the pediatric intensive care unit have preexisting malnutrition,” said Katri V. Typpo, MD, MPH, an associate professor at the University of Arizona College of Medicine, in Tucson. “And up to 66% or more have acquired malnutrition at the time of PICU discharge.”
There are several causes of this malnutrition. “Our children in the PICU have minimal substrate reserves,” Dr. Typpo said during her presentation. “They have an altered metabolism. They have inadequate nutrient delivery much of the time. And they [may] have chronic diseases that may impact their malnutrition at the time of admission.”
Providing adequate nutrition in this population is critical to outcomes. “Nutrition is a little like Goldilocks—too much or too little and your patient suffers with a negative clinical consequence; but if you get it just right, then maybe our patients will do well,” Dr. Typpo said.
Under- and overfeeding critically ill children have “been associated with poor outcomes in these patients,” said Michael L. Christensen, PharmD, a professor in the Departments of Clinical Pharmacy and Pediatrics at the University of Tennessee Health Science Center, in Memphis, who was asked to comment on the topic but did not present at SCCM. He cited, as an example, a study showing that hyperglycemia led to longer duration of ventilator use in 37 premature infants with sepsis (J Pediatr Surg 2006;41:239-244). The study also found that the maximum serum glucose concentration after a positive blood culture was linked to duration of total parenteral nutrition (PN) (R=0.45; P=0.005), duration of mechanical ventilation use (R=0.45; P=0.006) and length of stay (R=0.36; P=0.005).
Another study (Crit Care Med 2012;40:2204-2211) found that in 500 mechanically ventilated children, patients receiving PN had higher mortality rates than those receiving enteral nutrition (EN) (odds ratio [OR], 2.61; 95% CI, 1.3-5.3; P=0.008).
Predicting Energy Expenditure
Dr. Typpo cited another challenge in optimizing nutrition in the PICU: the standard formulas used to predict energy expenditure, such as the Harris-Benedict equation, the Caldwell-Kennedy and the WHO resting energy expenditure equation, can under- or overestimate calorie needs by as much as 20%. In a study that compared several of these predictive equations, none of them accurately estimated energy needs. In fact, the Harris-Benedict equation underestimated resting energy expenditure by a mean of about 150 kcal per day (J Crit Care 2012;27:321.e5-321.e12), she noted.
Indirect calorimetry may provide a more accurate measurement of energy expenditure. “But a lot of hospitals don’t have that capability or expertise,” Dr. Christensen said. “What we’re often left with is giving our best estimate and then frequently reassessing the patient to see if, in fact, we are meeting their [nutritional] needs,” he said.
Protein is critical to delivering sufficient nutrition and may influence outcomes, specifically reducing the probability of death. “There’s a lot of emerging data to suggest that protein delivery is extremely important in improving patient outcomes,” Dr. Typpo said.
For example, a study found that in mechanically ventilated children, delivery of more than 60% of prescribed protein intake is linked to a 3.2% risk for 60-day mortality compared with a 9.3% risk in patients who received less than 20% of prescribed protein (Am J Clin Nutr 2015;102:199-206).
How, When and Where to Feed
When to initiate EN has been controversial, noted Sharon Y. Irving, PhD, RN, an assistant professor of pediatric nursing at the University of Pennsylvania, in Philadelphia. “We know that early enteral nutrition is a positive in this population,” Dr. Irving said during the SCCM annual meeting. That observation supported by published research. For example, a multicenter, retrospective study of 5,105 patients in 12 PICUs showed that early EN, started within 48 hours of PICU admission, is linked to decreased mortality (J Parenter Enteral Nutr2014;38:459-466). Patients who received early EN had a lower mortality rate than those without early EN (OR, 0.51; 95% CI, 0.34-0.76; P=0.001).
Gastric Feeding Preferred
Enteral feeding can be delivered through gastric or post-pyloric tubes. A study found that feeding via the small bowel achieved 47±22% of the daily caloric goal compared with 30±23% for gastric feeding (P<0.01) (Chest 2004;126:872-878). However, gastric feeding may be more physiologic and better tolerated overall.
Dr. Christensen cited another advantage of gastric tube feeding: “If the tube is placed far enough into the small intestine, you are less likely to get vomiting or aspiration of the contents,” he said.
There is a place for PN, however, such as when the patient has severe gut ischemia, an acute surgical abdomen or intraabdominal hypertension, according to Dr. Irving.
For infants, the question of when to use PN feedings depends on the patient’s nutritional status, gastrointestinal function and tolerance, Dr. Christensen pointed out. A critically ill infant would be started on PN within two to three days of PICU admission if enteral feeding is inadequate or not feasible. For premature infants with an uncertain GI tract, PN would be started as soon after birth as possible to prevent the infant from going into a catabolic state. “We try to get protein into premature infants as quickly as possible,” he said.