The development of hyponatremia following combination chemotherapy for metastatic germ cell tumors

The combination of high dose vinblastine, cisplatin, and bleomycin is an extremely effective, but potentially quite toxic, program for the treatment of metastatic germ cell tumors. In addition to the well-described toxicities, we have noted moderate to severe hyponatremia associated with these drugs. Twelve patients who were receiving this combination chemotherapy program had serum electrolyte levels, plasma osmolality, and creatinine clearance performed prior to and again 5 to 9 days after chemotherapy. Nine of the patients had standard water load tests prior to and again 6 to 15 days after chemotherapy. All 12 patients developed a fall in serum sodium concentrations following chemotherapy, and four patients had severe symptoms attributable to the hyponatremia. Eight patients also developed hypoosmolality suggesting that the hyponatremia was secondary to impaired water handling. In five patients further evidence of impaired water handling was documented by the development of an abnormal standard water load test following chemotherapy. The hyponatremia and impaired water handling may be due primarily to the high doses of vinblastine in the chemotherapeutic program. Patients who are receiving this combination chemotherapy program should be observed for the development of hyponatremia. The presence of severe, symptomatic hyponatremia and impaired water handling may require appropriate treatment including water restriction and hypertonic saline administration.