We performed prospective and retrospective studies of 96 consecutive patients with
acquired immune deficiency syndrome (
AIDS) or
AIDS-related complex (
ARC) to determine the incidence, pathogenesis, and clinical significance of
hyponatremia, defined as serum
sodium levels less than or equal to 130 mmol/L on more than one occasion. Thirty (31.3%), six with
ARC and 24 with
AIDS, had
hyponatremia, and it developed in 20 as outpatients. Age, gender, duration of illness, and
weight loss did not differ between groups. The hyponatremic patient had more opportunistic illnesses, including
Pneumocystis carinii pneumonia and
cytomegalovirus infections, and had a mortality of 70% as compared to 36.4% of the patients without
hyponatremia. The probability of 50% survival after diagnosis of human immunodeficiency virus (
HIV) infection in the hyponatremic group was 11.5 months, as compared to 39 months for those without
hyponatremia, p less than 0.001. The probability of 50% survival after development of
hyponatremia was 4.5 months and the median length of time to development of
hyponatremia was 12.5 months after diagnosis of
HIV infection. Eighty-eight percent had
hypovolemia and 12% normovolemia. Seventeen of 21 with
hypovolemia had no evident source of fluid loss. Two had
Addison's disease, and 15 had unexpectedly high urine
sodium concentration without evidence of renal or
adrenal insufficiency.
Hyponatremia occurs commonly in ambulatory patients with
ARC or
AIDS, appears in patients with higher mortality and morbidity, and does not represent a terminal event. Most patients had
hypovolemia and unexpectedly high urine
sodium concentration, suggesting defective renal
sodium conservation.