Effect of Mannitol on Serum and Urine Electrolyte in Neurosurgical Patients

Kim, Jong Hoon; Kim, Kab Su; Nam, Yong Taek; Park, Kwang Won

Abstract

Osmotic diuretics are used in neurosurgical patient to decrease intracranial pressure. Mannitol produces diuresis because it is filtered by the glomeruli and not reabsorbed from the renal tubule, leading to increased osmolarity of renal tubular fluid and associated excretion of water. There are some controversies about the effect of mannitol induced diuresis on the change of serum electrolytes. But these controversies are related to the mannitol dosage and infusion speed. We studied the effect of mannitol on serum and urine e1ectrolyte change in 10 patients undergoing operation of cerebral tumor or aneurysm. Every patient was free from cardiac and renal disease. We started infusion of 20% mannitol of which dosage is 0.6-0.9gm/kg for 5 to 10 min after cranium was opened and then injected furosemide O.l mg/kg for acceleration of diuresis. We measured serum electrolyte, urine volume and urine electrolyte before and after 30, 60 and 120 min of mannitol infusion. The results were as follows. 1) Seurm sodium and chloride level decreased significantly from 133 and 102 to l30 and 100 mEq/1 respectively after 30 min, but there was no statistic significance after 60 and 120 min of mannitol infusion. 2) Serum potassium level increased slightly from 4.2 to 4.5 mEq/1 after mannitol infusion but there was no statistic significance. 3) Urine volume increased abruptly from 57 to 477 ml/hr as soon as infusion of mannitol but the degree decreased slowly following times. 4) Urine electrolytes concentration increased abruptly as soon as infusion of mannitol but the degree decrease slowly following times. With the above results, we can conclude that intraoperative mannitol and furosemide infusion in healthy patient can cause only transient change in serum electrolyte and the magnitude of change was too small to have significant clinical effect.