EFFECTS OF VARYING LEVELS OF POSITIVE END-EXPIRATORY PRESSURE ON INTRACRANIAL-PRESSURE AND CEREBRAL PERFUSION-PRESSURE

Objective: To determine the influence of positive end expiratory press ure (PEEP) on intracranial pressure and cerebral perfusion pressure. D esign: Neurosurgical intensive care patients requiring intracranial pr essure monitoring and mechanical ventilation were studied in a randomi zed, controlled study. Setting: Tertiary care, neurosurgical intensive care unit. Patients: Eighteen patients were enrolled in the study. Pa tients had posttraumatic head injuries (n = 9), subarachnoid hemorrhag e (n = 7), obstructive hydrocephalus (n = 1), and intracerebral hemorr hage of unknown cause (n = 1). Interventions: Patients had PEEP levels of 5, 10, and 15 cm H2O applied to their lungs. Measurements and Main Results: Changes in intracranial pressure, mean arterial pressure, an d cerebral perfusion pressure were measured. The results were analyzed separately for patients with normal and increased intracranial pressu re (>15 mm Hg). PEEP at 5 cm H2O had no effect on intracranial pressur e in the group with normal intracranial pressure. However, PEEP at 10 and 15 cm H2O produced a significant (p < .05) increase in intracrania l pressure (1.9 and 1.5 mm Hg, respectively). In the group with increa sed intracranial pressure, no significant change in intracranial press ure occurred at any of the PEEP levels used. In both groups, cerebral perfusion pressure was unchanged throughout. Conclusions: In patients with normal intracranial pressure, PEEP at 5 cm H2O did not significan tly alter intracranial pressure. The clinical relevance of the intracr anial pressure increase at PEEP levels of 10 and 15 cm H2O is question able because cerebral perfusion pressure did not change and remained > 60 mm Hg. In patients with increased intracranial pressure, higher lev els of PEEP did not significantly change intracranial pressure or cere bral perfusion pressure.