Dexamethasone causes less steroid-induced alkalemia than methylprednisolone or hydrocortisone.

Corticosteroid-induced metabolic alkalemia is an important ICU problem because many of these patients may compensate by alveolar hypoventilation. The effects of 3 commonly used steroids on arterial pH, PaCO2, and serum bicarbonate concentrations were studied in 24 healthy male baboons randomly divided into 3 groups. Each group of 8 animals received 7-day dose-equivalent courses of either hydrocortisone (300 mg daily), methylprednisolone (60 mg daily), or dexamethasone (15 mg daily). Treatment with either hydrocortisone or methylprednisolone increased arterial pH (p less than .05) and serum bicarbonate levels (p less than .01) and the animals receiving hydrocortisone showed significant (p less than .05) compensatory alveolar hypoventilation. Dexamethasone therapy did not cause any of these steroid-induced changes.