Alterations in serum osmolality, sodium, and potassium levels after repeated mannitol administration

This study was undertaken to evaluate whether significant alterations in serum osmolality, [Na+], and [K+] occur after the repeated dosing of mannitol and whether these imbalances increased accordingly with the progress of mannitol application. This study was conducted by performing a retrospective medical record review of brain injury patients who were admitted to the neurological intensive care units of a university hospital located in Incheon, South Korea. Data on intracranial pressure and serum [Na+], [K+], and osmolality levels were collected from the first to the seventh day of mannitol administration. Our results showed that the highest rate of hyperosmolality occurred on the first day of mannitol administration and that subsequently its rate reduced, although it still maintained high (70-77%). Regarding the serum [Na+], hypernatremia was observed in 10% of the subjects on the first day of mannitol administration and in 10-21% throughout the 7-day mannitol administration period. In this study, hyponatremia was observed in 12.2% of our subjects on the first day of mannitol administration and in 9-24% throughout the 7-day period. In addition, no statistical differences were found between changes in the rates of hypernatremia and hyponatremia throughout the 7-day administration period. The most notable finding was the high rates of hypokalemia observed during mannitol administration. Hypokalemia was observed in 22% of subjects on the first day and continuously increased to 52.3%, and this increase was significant. On the other hand, the rate of hyperkalemia was almost negligible. Our findings appear to provide clear evidence of electrolyte imbalances after repeated mannitol administration. Accordingly, careful monitoring of electrolyte status is essential when repeated doses of mannitol are given. We recommend that the practice of administering repeated dose of mannitol for prophylactic purposes be reevaluated.