Increased insulin requirements are associated with pneumonia after severe injury

Hyperglycemia after severe injury has been associated with an increased risk of infection and death. Strict glycemic control has been found to be valuable in select surgical populations. Varying amounts of insulin by infusion are required to maintain blood glucose levels within normal limits. Little is known about how insulin requirements are affected by the presence of infection, and therefore, the purpose of this study was to characterize this relationship.

Medical records of all intubated, injured patients admitted to the intensive care unit during a 16-month period were reviewed. Patients were included if they were managed with an insulin infusion, and they had a single bronchoalveolar lavage (BAL) culture performed for presumed pneumonia between 48 hours and 8 days. Mean hourly and 24-hour insulin requirements were analyzed before BAL was performed and then compared with values after cultures were obtained. This difference was then compared between patients with and without pneumonia.

Eighty-two patients met inclusion criteria during the 16-month study period. The hourly and 24-hour insulin requirements significantly increased from before to after BAL was performed in patients with pneumonia (n = 54) and not in those without (n = 28) (p = 0.008). The 24-hour insulin requirement increased by 26.2 units from before to after BAL in the pneumonia group versus 7.6 units in the nonpneumonia group (p = 0.029). A mean hourly insulin requirement increase of 1.2 units more than the pre-BAL level demonstrated an 86% positive predictive value and 89% specificity for pneumonia.

An increase in insulin requirements at the time of obtaining pulmonary cultures is associated with the presence of pneumonia and may represent a valuable tool for earlier recognition.