The effect of ketamine on intracranial pressure during haemorrhagic shock under the conditions of both spontaneous breathing and controlled ventilation.

Seventeen piglets of both sexes, seven with O2/air-buprenorphine anaesthesia and controlled ventilation, and ten unanaesthetized animals with normal, spontaneous respiration, were used for the study. The intracranial pressure of both groups of animals was raised by insufflation of an epidural balloon and the arterial blood pressure was reduced to approximately 70% of the original value by controlled haemorrhage. 0.5 mg/kg body weight of ketamine was given intravenously, followed by a further dose of 2.0 mg/kg body weight of ketamine five minutes later. Both ketamine doses led to a significant rise in the intracranial pressure of those animals breathing spontaneously (31.8 mm Hg to 39.1 mm Hg). In contrast, the ventilated animals showed a significant reduction in intracranial pressure. No changes in arterial PCO2 were observed in this group, while those piglets breathing spontaneously had dangerous PCO2 rises. At both ketamine doses a significant correlation could be found between the PCO2 and the intracranial pressure.