Glucose intolerance in critically ill surgical patients: relationship to total parenteral nutrition and severity of illness

Abstract

The authors evaluated the relative influence of severity of illness and total parenteral nutrition (TPN) on glucose intolerance in critically ill surgical patients. Records of TPN administration, serum glucose measurements, and the simplified acute physiology score (SAPS) were extracted from the surgical intensive care unit (SICU) and hospital clinical information systems (CIS) for all patients admitted to the SICU from October 1, 1989 through March 31, 1990. Critical hyperglycemia was defined as glucose > 400 mg/dL and critical hypoglycemia as < 40 mg/dL. During the study period, 1,129 patients received 3,054 days of care, including 88 patients who received 705 days of TPN. Of 4,985 glucose determinations performed during the study period, 48 (0.96%) were critically abnormal. Critical hyperglycemia occurred in 1.7 per cent of blood samples from TPN patients, compared to 0.7 per cent in non-TPN patients (P < 0.005). However, the mean admission and daily and maximum severity of illness scores were significantly higher in TPN patients compared to non-TPN patients (all P < 0.0005). Mean glucose levels rose with increasing SAPS in both TPN and non-TPN patients. When stratified by severity of illness, TPN patients did not have significantly higher glucose levels than non-TPN patients except for the SAPS = 15 category. The authors conclude that the glucose intolerance noted in critically ill TPN patients reflects their underlying severity of illness rather than TPN administration per se.