Positive end-expiratory pressure alters intracranial and cerebral perfusion pressure in severe traumatic brain injury

Background: Optimizing intracranial pressure (ICP) and cerebral perfusion pressure (CPP) is important in the management of severe traumatic brain injury (TBI). In trauma patients with TBI and respiratory dysfunction, positive end-expiratory pressure (PEEP) is often required to support oxygenation. Increases in PEEP may lead to reduced CPP. We hypothesized that increases in PEEP are associated with compromised hemodynamics and altered cerebral perfusion. Methods: Twenty patients (mean Injury Severity Score of 28) with TBI (Glasgow Coma Scale score < 8) were examined. All required simultaneous ICP and hemodynamic monitoring. Data were categorized on the basis of PEEP levels. Variables included central venous pressure, pulmonary artery occlusion pressure, cardiac index, oxygen delivery, and oxygen consumption indices. Differences were assessed using Kruskal-Wallis analysis of variance. Results: Data were expressed as mean ± SE. As PEEP increased from 0 to 5, to 6 to 10 and 11 to 15 cm H₂O, ICP decreased from 14.7 ± 0.2 to 13.6 ± 0.2 and 13.1 ± 0.3 mm Hg, respectively. Concurrently, CPP improved from 77.5 ± 0.3 to 80.1 ± 0.5 and 78.9 ± 0.7 mm Hg. As central venous pressure (5.9 ± 0.1, 8.3 ± 0.2, and 12.0 ± 0.3 mm Hg) and pulmonary artery occlusion pressure (8.3 ± 0.2, 11.6 ± 0.4, and 15.6 ± 0.4 mm Hg) increased with rising levels of PEEP, cardiac index, oxygen delivery, and oxygen consumption indices remained unaffected. Overall mortality was 30%. Conclusion: In trauma patients with severe TBI, the strategy of increasing PEEP to optimize oxygenation is not associated with reduced cerebral perfusion or compromised oxygen transport.