Experimental study on the indications for barbiturate therapy. Change in haemodynamics and the influence of dopamine

The effect of barbiturates on the cerebral haemodynamics and the influence of dopamine on barbiturates were investigated using 20 cats, and clinical indication of barbiturate therapy is discussed. Cerebral blood flow, oxygen extraction fraction, and cerebro-vascular resistance as well as physiological variables were evaluated at various concentrations of barbiturates in the blood. Thiamylal caused simultaneous reduction of mean arterial blood pressure and cerebral blood flow. As the disruption of autoregulation proceeded, cerebro-vascular resistance and oxygen extraction fraction increased till the barbiturate-induced coma stage. Furthermore, cerebro-vascular resistance increased much more markedly by the combined use of dopamine. Clinically, our results indicate barbiturates would increase cerebral circulatory disturbances caused by vasospasm following subarachnoid haemorrhage because barbiturates further increase cerebro-vascular resistance. Then again, the combined use of dopamine is not preferable because of deterioration in vasospasm.