Early versus late parenteral nutrition in the adult ICU: feeding the patient or our conscience?

Background: Critical illness increases the risk of malnutrition, which can increase infections, prolong mechanical ventilation, delay recovery, and increase mortality. While enteral nutrition (EN) is considered optimal, this is not always an option. Furthermore, algorithms for parenteral nutrition (PN) vary significantly, and it is unclear whether early initiation or delay of parenteral feeding is preferable. Objective: This study compares intensive care unit (ICU) duration of stay in adults randomized to early initiation of PN (within 48 hr of ICU admission) vs delayed (at eight days or later after ICU admission), as consistent with European and North American guidelines, respectively. Design and setting: This multicentre parallel-group randomized controlled trial was carried out from August 2007 to November 2010 and involved seven Belgian ICUs. The trial was powered at>80% to detect a one-day between-group change of stay in the ICU and powered at 70% to detect a 3% change in mortality. The study was supported by an unrestricted and unconditional grant from Baxter Healthcare. Patients: Inclusion criteria included patients older than 18 yr who were admitted to the ICU and had a nutritional risk screening (NRS) score of ≤ 3 (scale of 1-7; where ≤ 3 indicates nutritional risk). Exclusion criteria included patients with a do not resuscitate order, short bowel syndrome, absence of central venous access, a body mass index (BMI)<17, the ability to tolerate oral nutrition or a predetermined nutritional regimen, and those with lung ventilation at home; patients in a diabetic coma or enrolled in other studies were also excluded. Intervention: Eight thousand, seven hundred three patients were screened, and 4,640 of those were randomized in blocks of ten via sequentially numbered envelopes. Two thousand three hundred twelve patients were assigned to early PN initiation, and 2,328 patients were assigned to late PN initiation. Patients received enteral feeding by unit protocol, if appropriate. In addition, early PN patients received an intravenous solution of 20% glucose to achieve 400 kCal day -1 on day one, 800 kCal day -1 on day two, and 100% of the caloric goal by day three. Patients were weaned from PN when enteral nutrition met<80% of caloric goals. The late PN initiation group received an intravenous solution of 5% glucose (equal in volume to the early initiation group and adequate to maintain hydration). If EN did not meet caloric goals by day seven, then PN was initiated on day eight. Both groups were maintained semirecumbant (unless contraindicated); they received prokinetic agents, had duodenal feeding tubes, and received early parenteral trace elements, minerals, and vitamins. © 2012 Canadian Anesthesiologists' Society.