Short term volume effects of a hypertonic saline bolus during neurosurgery

Intracranial hypertension which does not respond to customary hyperosmotic agents may successfully be treated with hypertonic saline. The absence of diuresis and the maintainance of intravascular volume are supposed to be the main advantages of hypertonic sodium chloride. Volume overload and toxic hyperosmolality from frequent application of such solutions are possible disadvantages. The presented experiments checked the time course of intravascular volume shifts after a 100 ml 1-molar saline bolus in 14 patients during neurosurgery using plasma protein concentration changes. An initial intravascular volume expansion of about 270 ml remained quite unchanged for the first 8 minutes, followed by a nearly linear decrease. Extrapolation of the curves demonstrated that the preinfusion state would have been reached after about 20 minutes. Osmolality remained increased by about 4 mosmol/kg 15 min after the bolus. Thus it appears that repetitive infusion of these amounts of hypertonic saline will cause no serious volume overload if 30 minutes intervals are kept, but osmolality should be checked before each bolus.