Hyponatremia in malaria

Abstract

Twenty-four Thai patients with Plasmodium falciparum malaria and 1 with vivax malaria were studied for abnormalities of salt and water metabolism. Hyponatremia, hypo-osmolality, and hypochloremia were found in 16 patients. The hyponatraemia was mild (127-134 mEq/1.) in all except 2 patients (119 and 124 mEq/1.) and its duration varied between 1 and 8 days. In comparison to the patients with a normal serum Na, the hyponatraemic patients were usually seen during their 1st attack of malaria, they had a more severe attack, and they showed more marked laboratory abnormalities. The hyponatremia was due to a mixture of salt depletion and water retention. Two of the patients had a low glomerular-filtration rate and renal-plasma flow, low blood pressure, low urinary Na, low urine volume, an abnormal water-load test, and were felt to have significant salt depletion. The other hyponatraemic patients had concentrated urine in the face of hypo-osmolality, normal renal clearances, and normal blood pressure. Although inappropriate secretion of antidiuretic hormone may have been present in some of the patients, the variable response to a water-load test and Na conservation raised the possibility of some other mechanism to explain the hyponatraemia. These findings are discussed in the light of present-day knowledge of hyponatraemia in pathological states.