[Change of intracranial pressure in neurosurgical patients by hyperventilation, positive negative pressure ventilation and PEEP (author's transl)].

The effects of a hyperventilation, positive negative pressure ventilation (PNPV) and ventilation using positive endexpiratory pressure (PEEP), on intracranial pressure (ICP) was measured in 24 patients suffering from different neurosurgical disorders. The patients were given a basic anaesthesia including muscle relaxation. The investigations showed, that hyperventilation, followed by a PCO2 of 26 and 30 torr, clearly lowered the intracranial pressure. The pressure drop was much more pronounced when the preexisting ICP was high than when it was low, due to the form of the compliance curve of the brain. PNPV also lowered intracranial pressure, but a harmful effect of this technique on lung function and structure is known. Its use is justified only for short periods and in addition to other measures for lowering ICP. The results also demonstrated that PNPV possesses limited beneficial properties with regard to the subject discussed here. Ventilation by PEEP significantly increased ICP. This technique is to be employed with caution in neurosurgery. Arterial pressure (radial artery) and central venous pressure (subclavian vein) were also recorded.