Neurochemical monitoring of glycerol therapy in patients with ischemic brain edema

Background and Purpose - Osmotic agents such as glycerol are used to treat brain edema in stroke patients. We investigated the pharmacokinetics of glycerol in brain tissue by cerebral microdialysis. Methods - Patients experiencing large middle cerebral artery infarction were included in this prospective study. The following variables were assessed before and every 10 minutes until 80 minutes after intravenous administration of 25 g of glycerol: intracranial pressure (ICP), serum osmolarity, and cerebral microdialysate concentrations of glycerol, glutamate, pyruvate, and lactate. Results - During 16 ICP crises in 7 patients, cerebral glycerol concentrations ( baseline 73.9 +/- 17.0 mumol/L) increased immediately after glycerol administration by up to 350%. Conversely, ICP ( baseline 25 +/- 2.4 mm Hg) rapidly decreased by almost 50%. Both effects lasted for 70 minutes. Serum osmolarity ( baseline 305 +/- 5.6 mOsm/L) was only briefly raised, whereas glutamate, lactate, and pyruvate remained unaffected. Conclusion - Treatment of stroke patients with intravenous glycerol has only a brief effect on plasma osmolarity, but a more sustained effect on ICP, which is, however, accompanied by a rapid glycerol accumulation in brain tissue.