Survival but not severity of hypoxic-ischemic encephalopathy is associated with higher mean arterial blood pressure after cardiac arrest: a retrospective cohort study

Abstract Background: To study the association between mean arterial blood pressure (MAP), vasopressor requirement, and severity of hypoxic-ischemic encephalopathy (HIE) after cardiac arrest (CA). Methods: Between 2008 and 2017, we retrospectively analyzed the MAP 200 hours after CA and quantified vasopressor requirements using the cumulative vasopressor index (CVI). Using postmortem brain autopsy in non-survivors, the severity of HIE was histopathologically dichotomized into no/mild and severe HIE. In survivors, we dichotomized the HIE severity into no/mild - Cerebral Performance Category (CPC) 1 – and severe HIE (CPC 4). Regain of consciousness, death causes and five-day survival were investigated as hemodynamic confounders. Results: Among 350 non-survivors, 117 had histopathologically severe HIE and 233 no/mild HIE without differences in MAP (73.1 vs 72.0 mmHg, p group =0.639). Compared to non-survivors, 211 CPC 1 and 57 CPC 4 patients had higher MAPs that showed significant, but clinically non-relevant MAP differences (81.2 vs 82.3 mmHg, p group <0.001). No/mild HIE non-survivors (n=54) regaining consciousness before death had higher MAPs compared to no/mild HIE non-survivors (n=179) who remained persistently comatose (74.7 vs 69.3 mmHg, p group <0.001). No/mild HIE non-survivors regaining consciousness required less vasopressors (CVI 2.1 vs 3.6, p group <0.001). Independently of HIE severity, survivors were faster weaned from vasopressors (CVI 1.0). Conclusions: Higher MAP was associated with survival but not HIE severity in CA patients treated with a vasopressor-supported MAP target above 65 mmHg. Awakening from coma was associated with less vasopressor requirements. Our results provide no evidence for a MAP target above current guideline recommendations to decrease the severity of HIE.