Fluid responsiveness and brain tissue oxygen augmentation after subarachnoid hemorrhage

Background: The objective of this study was to investigate the relationship between cardiac index (CI) response to a fluid challenge and changes in brain tissue oxygen pressure (PbtO₂) in patients with subarachnoid hemorrhage (SAH). Methods: Prospective observational study was conducted in a neurological intensive care unit of a university hospital. Fifty-seven fluid challenges were administered to ten consecutive comatose SAH patients that underwent multimodality monitoring of CI, intracranial pressure (ICP), and PbtO₂, according to a standardized fluid management protocol. Results: The relationship between CI and PbtO₂ was analyzed with logistic regression utilizing generalized estimating equations. Of the 57 fluid boluses analyzed, 27 (47 %) resulted in a ≥ 10 % increase in CI. Median absolute (+5.8 vs. +1.3 mmHg) and percent (20.7 vs. 3.5 %) changes in PbtO ₂ were greater in CI responders than in non-responders within 30 min after the end of the fluid bolus infusion. In a multivariable model, a CI response was independently associated with PbtO₂ response (adjusted odds ratio 21.5, 95 % CI 1.4-324, P = 0.03) after adjusting for mean arterial pressure change and end-tidal CO₂. Stroke volume variation showed a good ability to predict CI and PbtO₂ response with areas under the ROC curve of 0.86 and 0.81 with the best cut-off values of 9 % for both responses. Conclusion: Bolus fluid resuscitation resulting in augmentation of CI can improve cerebral oxygenation after SAH.