Con: Tight Perioperative Glycemic Control: Poorly Supported and Risky

A S m AINTAINING A PERIOPERATIVE SERUM GLUCOSE CONCENTRATION of less than 120 mg/dL (6.6 mol/L ) has uncertain benefit and considerable risk. In a large andomized controlled trial (RCT) of 1548 critically ill patients n Belgium, Van den Berghe et al1 demonstrated a 42% relative eduction in mortality with the use of an insulin infusion to aintain tight glycemic control in a mixed medical and surgical opulation. Many cite these and other data to support the pplication of insulin infusions to varied intensive care unit ICU) populations and, by extension, intraoperative care. Such ssertions are overzealous. They outpace available clinical scince, are based on poorly substantiated assertions, and fail to ecognize an ongoing fundamental lack of understanding about he role of insulin in stress metabolism. Given these differnces, attempting to “normalize” glucose values during surgery s at least risky, and perhaps harmful. Enthusiasm for tight glycemic control deserves a more deiberate, perhaps even skeptical, approach. Details from availble clinical data and basic clinical science suggest that inapropriate insulin use may be associated with harm. Any time linical data are extrapolated to new populations there is this isk. The medical community, is committed to providing the aximal help to patients, but must remember to “first, do no arm.” Areas of concern include population selection, mechaism of benefit (and potential harm), appropriate end points, isk for hypoglycemia, and the burden of liability. Incomplete understanding of risks and benefits confounds he further selection of patient populations for whom this herapy might be beneficial. Specific conditions uniquely benfit from the effects of insulin, tightly regulated glucose, or oth. There are studies that support tight glycemic control or nsulin therapy in certain populations. Hyperglycemia is detriental in the setting of cerebral ischemia.2 Insulin may exert enefits to myocardial metabolism independent of the level of lycemic control,3,4 and there may exist specific indications for irected metabolic therapy. However, use for these purposes hould not be confused with therapies that target specific serum lucose concentrations in all surgical patients. In fact, few data xist to support the appropriateness of tight control in intraoprative patients. It is interesting to note that the original Belgian tudy population consisted of medical and postoperative surgial patients, more than 60% of whom were cardiac surgery atients, who may derive unique benefit from insulin. Not only ight this therapy be appropriate only in specific conditions, ut favorable response might depend on the state of recovery. esponse to, and perhaps benefit from, insulin changes over the ourse of illness. Looking at the Van den Berghe data, it might e concluded that the benefits of glycemic control come relaively late during the ICU stay. Most of the benefits seen in the tudy were in patients who spent more than 5 days in the ICU. his is consistent with the current understanding of the stress esponse.5 As the response to tissue injury abates, an anabolic ormone such as insulin has a more important role in the etabolic process. During acute injury such as surgery, treatent with an anabolic hormone might be harmful. Finally, ther factors, such as the provision of nutrition, may have a role n the response to glycemic control strategies. The ICU popuc