Effect of glycerol and hyperosmolality on intracranial pressure

Glycerol has been used in cerebral edema for hyperosmolar dehydration of brain tissue, but only empirical relationships govern this use. Since the efficacy of treatment with glycerol would likely increase with data on the relationship between drug blood levels and intracranial pressure (ICP), we examined the clinical pharmacology of the drug. Plasma samples were assayed for glycerol by a new method using gas chromatography with a flame ionization detector. Data were collected from 12 children who were in Children's Hospital of Pittsburgh (CHP) and who had cerebral edema of differing etiology that was treated with glycerol; they were monitored by intraventricular catheter. Glycerol was infused according to CHP guidelines. ICP reduction correlated with glycerol concentration and plasma concentrations of 1 to 3 mg/ml (10 to 30 mOsm/ml) were necessary to maintain an ICP below 20 torr. The relationship between osmolality and plasma glycerol level was also examined; there was good correlation between the idiogenic osmolality and drug concentration. Our studies support the clinical observations that relatively high doses of glycerol (0.2 to 1.0 gm/kg/hr), leading to plasma concentrations of 10 to 30 mOsm/l, are necessary to control ICP in patients with cerebral edema. Glycerol blood levels may be estimated from serum osmolality.