Cerebral blood flow autoregulation during prehospital post-resuscitation care

BACKGROUND: Successfully resuscitated out-of-hospital cardiac arrest (OHCA) patients often experience cerebral malperfusion, possibly due to impaired autoregulation. Understanding the link between arterial pressure and cerebral blood flow (CBF) is essential for optimising cerebral oxygenation. This study examined early post-resuscitation CBF autoregulation and assessed the feasibility of identifying patient-specific optimal mean arterial pressure (MAPopt) from data obtained during prehospital care. METHODS: We performed a post hoc analysis of 12 OHCA patients treated by a physician-staffed helicopter emergency services unit. Frontal lobe regional oxygen saturation (rSO 2 ) and invasive arterial pressure were recorded during prehospital post-resuscitation care. The cerebral oximetry index (COx), defined as the correlation coefficient between rSO 2 and MAP, was calculated as a time series for each patient. COx values were plotted in 5 mmHg MAP increments and reviewed by two independent experts to determine patient specific MAPopt. RESULTS: The mean duration of near-infrared spectroscopy monitoring was 47 minutes. MAPopt was identifiable in eight of 12 patients (66%). Seven patients (58%) showed impaired autoregulation, as mean COx > 0.3. Map and rSO 2 demonstrated a nonlinear relationship, with lower MAP associated with reduced cerebral oxygenation. MAPopt for the cohort was approximately 80 mmHg. CONCLUSIONS: Cerebral autoregulation assessment after OHCA is feasible with physiological data recorded in prehospital setting. Low blood pressure was associated with reduced cerebral oxygenation. Impaired autoregulation was found in most patients. Large inter-individual variation in optimal blood pressure precluded the determination of a common target pressure and emphasises the need for personalised haemodynamic management in the ultra-acute post-resuscitation phase.