The association between fluid management and hemodynamic parameters in patients with acute brain injury

Purpose Higher fluid input (FI) resulting in more positive fluid balance (FB) is associated with worse outcome in aneurysmal subarachnoid hemorrhage (aSAH) and traumatic brain injury (TBI) patients. Although venous congestion could be a possible mechanism behind these associations, hemodynamic studies elucidating these associations are scarce. We aimed to explore the association of FI and FB with cardiac index (CI) and central venous pressure (CVP) in aSAH and TBI patients. Methods We performed a prospective observational study, including aSAH and TBI patients aged ≥18 years admitted to the ICU and with an ICU stay of >48 hours. The association of daily FI and cumulative FB during the first week after admission with mean daily values of CI, CVP, intracranial pressure (ICP) and cerebral perfusion pressure (CPP) were analyzed with linear mixed effects models and adjusted for time since ICU admission. Results We included 55 patients; mean age 51 years (SD 18), 58% female and median GCS 7 (IQR 3-12). CI change with 1L higher cumulative FB was -0.060 L/min/m 2 [95% CI -0.101 to -0.018]. CVP was 0.349 mmHg [95% CI 0.077 to 0.620] higher with 1L higher cumulative FB, CPP 0.365 mmHg [95% CI -0.750 to 0.039] lower with 1L higher cumulative FB, and ICP 0.499 mmHg [95% CI 0.166 to 0.866] higher with 1L higher cumulative FB. Conclusions Higher cumulative FB is associated with lower CI, higher CVP and ICP increase, which might indicate cerebral venous congestion and represent an important causal factor in the association of positive FB with poor outcome.