Hematocrit-to-Hemoglobin Ratio as a Novel Independent Predictor for In-Hospital Mortality and Delayed Cerebral Ischemia in Critically Ill Patients with Aneurysmal Subarachnoid Hemorrhage Requiring Neurosurgical or Endovascular Treatment: A Retrospective Analysis

Background: Substantial research has been dedicated to new prognostication tools in aneurysmal subarachnoid hemorrhage (aSAH), with a recent focus on laboratory parameters. Our study investigates the predictive value of a new hematological index, the hematocrit-to-hemoglobin (Ht-to-Hb) ratio, for mortality and delayed cerebral ischemia (DCI). Methods: This is a retrospective, single-center, observational study on 78 adult critically ill patients with aSAH. We collected data from the electronic and written records, including demographic and clinical data, therapeutic measures, and intensive care unit and hospital length of stay. The primary outcome was in-hospital mortality, whereas the secondary outcome was DCI development. After descriptive analysis was performed, the Ht-to-Hb ratio was tested as a predictor for the primary and secondary outcomes. Firstly, we conducted a receiver operating characteristic analysis, and cutoff values were identified using the Youden index. Further, in-hospital mortality and DCI probability were evaluated using the log rank test. Cox proportional hazards regression was conducted to test the independent predictive value of the Ht-to-Hb ratio for the aforementioned outcomes. Results: Mortality during hospitalization was 25.54%, whereas DCI frequency was 42.3%. The Ht-to-Hb ratio had areas under the receiver operating characteristic curve for death prediction and DCI of 0.85 and 0.734, respectively. Values greater than the cutoff value for mortality, 3.069, were independently associated with the primary outcome in the multivariable analysis (hazard ratio [HR] 4.64, 95% confidence interval [CI] 1.08–19.98, p = 0.039). For DCI, the cutoff value identified was 3.007. Ht-to-Hb ratios > 3.007 were an independent risk factor for DCI in the multivariable analysis (HR 3.86, 95% CI 1.43–10.4, p = 0.008). Conclusions: The present study proposes a new prognostic index for mortality and DCI in aSAH: the Ht-to-Hb ratio. This marker could act as a surrogate for blood viscosity, uncovering the importance of blood rheology in aSAH pathogenesis.