Intravenous sodium bicarbonate has been used for a long time in the treatment of diabetic ketoacidosis. However, there are no clinical studies showing its effectiveness in improving arterial pH in this condition. We therefore designed this study to investigate if bicarbonate therapy improves the rate of increase of arterial pH and to find out its effects on the recovery rate of the other metabolic abnormalities. Twenty patients with severe diabetic ketoacidosis (pH less than 7.15) entered a double-blind, randomized, placebo controlled trial: nine were included in the bicarbonate group and eleven in the placebo group. All patients were studied during the first 24 hours of treatment. Their management was similar, except for the use of sodium bicarbonate in one group and 0.9% saline solution in the placebo group. Heart rate, respiratory rate, arterial pressure, mental status, blood gases, blood glucose, sodium, potassium, and urea were assessed at the beginning of treatment, and then at 2, 6, 12 and 24 hours. No clinical or metabolic differences were found between groups. Two hours after therapy was begun, the arterial pH rose in the bicarbonate group from 7.05 +/- 0.08 to 7.24 +/- 0.04, while it only rose from 7.04 +/- 0.08 to 7.11 +/- 0.09 in the placebo group (p less than 0.02). Simultaneously, arterial bicarbonate increased from 2.87 +/- 1.2 to 6.1 +/- 1.5 mEq/L in the bicarbonate group and from 2.55 +/- 0.81 to 3.6 +/- 2 mEq/L in the placebo group (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)