A 10-day-old male infant was brought to the emergency room in shock. He was the product of an uncomplicated gestation and delivery; his birth weight was 2660 g. He had been well until one day before admission, when he became listless and tachypneic. On examination he responded poorly to stimulation, blood pressure was unobtainable, pulse rate was 160 beats per minute and weak, respirations Were 52/min and shallow, and temperature was 36.9°C. His weight had decreased to 1900 g—760 g below his birth Weight. Arterial blood gas values were as follows: pH, 7.07; Po2, 71 mm Hg; and Pco2, 31 mm Hg (breathing 100% oxygen). Leukocyte count was 20.1x109/L (20 100/mm3), with 0.08 (8%) band forms, 0.05 (5%) metamyelocytes, 0.60 (60%) neutrophils, 0.22 (22%) lymphocytes, and 0.04 (4%) monocytes. Laboratory values included the following: serum creatinine, 250 μmol/L (2.8 mg/dL); serum urea nitrogen, 22.8 mmol/L (64