Is continuous insulin treatment safe in aneurysmal subarachnoid hemorrhage?

OBJECTIVES: To investigate the long-term effect of continuous insulin infusion for glucose control on cerebral metabolism in aneurysmal subarachnoid hemorrhage (SAH) patients. METHODS: Prospective, nonrandomized study of 31 SAH patients in the ICU (52 ± 10 years, WFNS Grade 2.9 ± 1.6). A microdialysis catheter was inserted into the vascular territory of the aneurysm. Metabolic changes during 4 days after onset of insulin infusion were analyzed. Blood glucose levels >140 mg/dL after clinical stabilization were treated with intravenous insulin. RESULTS: 24 patients were treated with intravenous insulin. Though no insulin-induced hypoglycemia occurred, cerebral glucose decreased on days 1–4 after insulin onset without reaching critical levels. Glycerol, a marker of membrane degradation, showed a reversible increase on day 1 while the lactate/pyruvate ratio remained stable and glutamate even decreased indicating absence of severe cerebral crisis following insulin infusion and excluding ischemia as a cause for cerebral glucose depletion. CONCLUSIONS: Concerning cerebral metabolism, long-term continuous insulin infusion appears to be safe as long as cerebral glucose levels do not fall below the physiological range. In view of the high incidence of hyperglycemia and need for insulin treatment, future studies on the effect of insulin on cerebral metabolism in SAH patients are desirable.