Hyperglycemia is normally defined by the blood glucose level (≥180 or 200 mg/dL) or the hyperglycemic index (≥1.76), a measure of overall glucose control1-3. Hyperglycemia is a significant risk factor for infection, polyneuropathy, an increased hospital length of stay, and mortality1,4,5. It has been studied extensively in diabetic patients but much less so in nondiabetic patients. Only recently has it been reported in nondiabetic trauma patients. Studies show that the stress of trauma causes the release of hormones (epinephrine and cortisol) that counter-regulate the normal action of insulin, thereby predisposing patients to hyperglycemia and ketoacidosis6. Hyperglycemia in nondiabetic orthopaedic trauma patients has received little attention. Richards et al. have now reported the relationship of hyperglycemia with thirty-day surgical-site infection in a population of orthopaedic trauma patients who did not have a history of diabetes. The authors are to be congratulated for bringing this valuable information to the orthopaedic community. The highlighting of this finding is a major strength of this study. The exclusion criteria used by the authors, which include a history of diabetes mellitus, an Abbreviated Injury Scale (AIS) score in any body region other than the extremity, the use of corticosteroids, or admission to the intensive care unit, strengthen their findings. The prospective collection of blood glucose values for the cohort is an additional strength. Finally, the hyperglycemic index used as a potential marker for hyperglycemia is an important and reliable measure.
The study does have limitations, including the fact that it is a retrospective investigation with inherent bias. This is readily apparent with regard to the use of the hyperglycemic index. The hyperglycemic index could be calculated for only 790 (47%) of the 1681 patients because the calculation of the hyperglycemic index requires two or more blood glucose levels and these were not available for all of the patients. The second limitation of this study is that the authors could not confirm that many of the patients did not have diabetes. Kopelman et al. noted that nearly 5% of general trauma patients were diagnosed with occult diabetes mellitus on the basis of hemoglobin A1C blood values7. If the current study had been prospective, the authors would have identified this group of patients and excluded their participation. The potential effect of including undiagnosed diabetic patients in the current study is not known.
The relatively small number of events—namely, only twenty-one surgical-site infections—is also a limitation of this study. However, I believe that this study will have a substantial impact on the orthopaedic community and act as a springboard for larger, prospective investigations. If future studies corroborate the findings, then one of the next steps will be to determine if tight glycemic control can help lessen the risk of infection for our diabetic and nondiabetic patients as well.