Correlation between intra-abdominal and intracranial pressure in nontraumatic brain injury

Objective: To examine on the basis of a large number of measurements whether increased IAP is associated with increased ICP and decreased CPP in ventilated patients with nontraumatic brain injury. Design and setting: Observational clinical study in the medical and surgical intensive care unit of a tertiary teaching hospital. Patients: We included 11 patients with nontraumatic brain injury who had an ICP and an IAP-monitoring device because of ischemic (n=4), hemorrhagic (n=5), and metabolic (n=2) encephalopathy. Methods: IAP was continuously measured in the stomach, and ICP was continuously measured through an intraventricular catheter; 214 consecutive measurements were compared. Because of repeated measurements in the patients we used analysis of covariance to control for the variation in ICP and CPP between patients. Measurements and results: Patients' mean IAP was 3.8-11.8 mmHg, ICP 6.7-15 mmHg, and CPP 70.8-123 mmHg. For ICP the regression coefficient associated with IAP was 0.64 +/- 0.05 (95% CI 0.56-0.73, partial correlation 0.70) and for CPP -1.36 +/- 0.3 (95% CI -1.94 to -0.78; partial correlation -0.30). Conclusions: Increases in IAP are associated with increases in ICP and decreases in CPP in ventilated patients with nontraumatic brain injury, even at low levels of IAP.