This is a retrospective analysis of a treatment approach designed to increase enteral protein intake in critically ill surgical patients. The study investigators recently developed guidelines aimed to improve early enteral protein delivery in critically ill patients. The guidelines were tested for 6 months; applying it to 53 patients (April to September, 2016) in order to determine its safety and effectiveness. All subjects were admitted to the surgical intensive care unit and identified by one of the investigators as being appropriate for protein supplementation. The guidelines required that patients were: 1. Deemed ready to start enteral nutritional support by the attending intensivist within 72 hours of admission to the intensive care unit, 2. No contraindications to full enteral support, 3. No history of chronic liver disease, 4. Serum creatinine <2.0 mg/dl.
In order to compare biochemical markers of nutritional support, the investigators used the electronic medical record to identify all patients admitted to the surgical intensive care unit who were in the ICU long enough to undergo testing of 24 hour urine nitrogen excretion from January to December 2016.8 As part of standard clinical practice, measurement of urine nitrogen excretion is performed in patients who are in the ICU and receiving nutritional support for more than one week. In addition to measuring TUN, the investigators also monitor the response to nutritional support and recovery from critical illness using serum transthyretin (also known as prealbumin).
This review resulted in a cohort of 118 patients who underwent at least one TUN measurement. Of these, 27 received early protein supplementation and 91 did not and these provide the basis for the comparisons described below. We wanted to measure the effect of early supplemental protein treatment on nitrogen excretion and on serum transthyretin concentrations as the patients recovered. We therefore, compared nitrogen excretion and serum transthyretin between those who received early supplementation and those who did not.