Abstract: Five RCTs met the pre-specified inclusion criteria for this review. No trials evaluated strict glycaemic control in the immediate pre-operative period or outside the intensive care unit. Due to heterogeneity in patient populations, peri-operative period, glycaemic target, route of insulin administration, and definitions of outcome measures, combination of the results of the five included trials into a meta-analysis was not appropriate. The methodological quality of the trials was variable. In terms of outcomes, only one trial demonstrated a significant reduction in SSIs with strict glycaemic control, but the quality of this trial was difficult to assess as a result of poor reporting; furthermore the baseline rate of SSIs was high (30%). The other trials were either underpowered to detect a difference in SSIs, due to a low baseline rate (less than or equal to 5%), or did not report SSIs as a single outcome but as part of a composite. Of the three trials reporting hypoglycaemia (which was not consistently defined) all had a higher rate in the strict glycaemic control group but none attributed significant morbidity to the hypoglycaemia. Adequacy of glucose control between groups was measured differently among studies. Studies could not be compared due to differences in target ranges, and were susceptible to measurement bias due to differences in frequency of measurement and lack of blinding by the providers following the glycaemic protocols. Infection-related mortality was not reported in any of the trials, and no trials demonstrated a significant difference in all-cause mortality. Length of hospital stay was significantly reduced in the strict glycaemic control groups in only one trial. There is insufficient evidence to support strict glycaemic control versus conventional management (maintenance of glucose < 200 mg/dL) for the prevention of SSIs. No trials were found that evaluated strict glycaemic control in the immediate pre-operative period or outside the setting of an intensive care unit. The trials were limited by small sample size, inconsistencies in the definitions of the outcome measures and methodological quality. Further large randomised trials are required to address this question and may be most appropriately performed in patients at high risk for SSIs.

Plain-language summary: Previous studies have suggested that decreasing blood glucose levels to within a low, narrow range (strict control) around the time of surgery may decrease infections and improve outcome. However, concerns about side effects from low glucose levels, such as seizures and increased risk of death, have prevented widespread use of this strategy. There are only five trials comparing strict control strategies with the conventional strategy of treating blood glucose levels only when they become high. These trials differ significantly in patient characteristics, glucose targets, medications and methods used to lower glucose levels, as well as the outcomes measured. Furthermore, the individual studies, which are small and/or flawed, do not demonstrate a significant decrease in surgical site infections. There are insufficient data to support the routine adoption of strict blood glucose control around the time of operation to prevent surgical site infections.