HYPONATREMIA IN SICKLE CRISIS — A DEFECT IN RENAL DILUTING CAPACITY

Abstract

Patients with sickle cell disease have a well known defect in renal concentrating ability. When in crisis these patients are usually treated with large volumesof intravenous and/or oral fluids. This study was prompted by the observation of several children in sickle crisis who developed severe hyponatremia with C N S symptoms while having high concentrations of sodium in the urine.Patients with mild to moderate pain and/or infection were studied. On admission to the hospital 10/51 patients had sodium concentrations in serum below 135<mEq/1. The mean osmolality of serum of 28 patients was 278mOsm/1, with 7/28 below 271mOsm/1. The urine osmolality was greater than the serum osmolality in 19/20, with a mean urine osmolality of 436mOsm/1 and a range of 265 to 673mOsm/1. The ratio of sodium concentration in the urine to that in the plasma(U/P) was greater than 0.95 in 10/31 patients with a mean of 0.73. Creatinine clearances were normal or increased free water excretion was reduced, and Na clearances were usually very high despite hyponatremia. These results indicate that the renal defect in sickle cell disease is not hyposthenuria, but rather a narrow range of solute concentration, with limited diluting as well as concentrating capacity. These patients have a tendency to lose excessive amounts of electrolyte in the urine,particularly during crisis, and are unable to handle a water load at these times. These findings have significant implications for supportive therapy.