[Intracranial pressure and circulatory parameters with positive end-expiratory pressure (PEEP). The possibility of drug modification].

In patients who have head injuries as well as injuries involving other organ systems, especially those of the thorax and upper abdomen, conflict can arise between the need to ensure adequate ventilation and the simultaneous need to protect the brain against further increases in intracranial pressure. Positive end-expiratory pressure (PEEP) ventilation, in particular, is suspected of causing the intracranial pressure to rise. Our study of the effects of a combination of anaesthetics on animals, was designed to investigate whether, the negative effects of PEEP ventilation on both intracranial pressure and on various circulatory parameters could be prevented. In animals with normal intracranial pressure at the outset of the experiment, during PEEP ventilation at pressures of up to 12 cmH2O, neither clinically significant rises in intracranial pressure, nor notable changes in circulatory parameters occurred. In comparison, those animals with artificially raised intracranial pressure showed marked differences with respect to their tolerance of PEEP ventilation. Whereas ventilation with an oxygen/nitrous oxide mixture caused a distinct elevation of the intracranial pressure and the deterioration of circulatory parameters, a combined regimen of etomidate and alfentanil under ventilation with an oxygen/air mixture minimized the negative effects of PEEP. Gradual increases in PEEP were tolerated better than a rapid rise in PEEP. With appropriate drug therapy, it is therefore possible to maintain PEEP ventilation in the presence of raised intracranial pressure without causing deterioration of the circulatory situation, or exacerbating the problems of intracranial pressure or cerebral perfusion pressure.