Mannitol, osmolality and steroids during renal transplantation. Real and theoretical influences on plasma potassium

Mannitol did not have an exaggerated effect on plasma potassium when administered to twelve patients undergoing renal transplantation. Unexpected rises in plasma osmolality, greater than those recorded after mannitol, were observed in two of the patients. In these two patients the osmolality changes were due to sudden hyperglycaemia and followed methylprednisolone therapy (given for immunosuppression). It is suggested that under certain circumstances, such changes in osmolality may lead to a rise in plasma potassium comparable to the effect of mannitol. One of the two patients with the rise in glucose and osmolality did have a rise in plasma potassium.