Oxygen transport, consumption and utilization during barbiturate intoxication.

Factors related to oxygen availability and requirements were measured on 51 occasions in 14 patients intoxicated with short-acting barbiturates. Patients had no clinical signs of circulatory shock. The cardiac index was normal (3.4 +/- 1.1 1/min/m2) but there was a slight decrease of the mean arterial oxygen content (17.2 +/- 3.0 ml/100 ml). Oxygen transport was normal (571 +/- 199 ml/min/m2). However, the arteriovenous oxygen differences were decreased (3.4 +/- 1.0 ml/100 ml). Oxygen consumption was reduced (110 +/- 42 ml/min/m2) and the oxygen extraction ratio (oxygen consumption/oxygen transport) was decreased (0.20 +/- 0.05), thus confirming a decreased oxygen utilization. Arterial concentration of lactate was normal. Accordingly the observed decrease in oxygen consumption was related to a reduction in oxygen requirements during barbiturate intoxication rather than due to an imbalance between availability and metabolic requirements for oxygen.