Abstract
Effects of mannitol infusion on serum and red-cell electrolyte concentrations were studied in patients undergoing elective neurosurgical operations. Patients in group A (n=8) received 600ml of 20per cent mannitol and in group B (n=7), 300ml of 20per cent mannitol in 30 to 40 minutes. Serum Na and Cl concentrations decreased during the mannitol infusions and showed the tendency to return to the baseline values after the infusion is both groups. These changes are closely related to the increase of serum osmolality. Though serum potassium concentration in group B was not altered by the mannitol infusion, in group A serum potassium concentration increased significantly from the baseline value 3.8±0.1 to 4.2±0.2mEq/1 at one hour after mannitol infusion. The increase of serum potassium is probably induced by the shift of water and intracellular ions to the exracellular space which occurs in hyperosmolar state in response to the loss of plasma volume during osmotic diuresis. Our results indicate the possibility of hyperkalemia after a large dose (more than 2g/kg) of mannitol infusion, especially in patients with good urinary response to mannitol.
