Relationship between hemodynamic parameters and cerebral blood flow during cardiopulmonary resuscitation

Introduction: Cerebral blood flow during cardiopulmonary resuscitation (CPR) is a major neuroprognostic factor although not clinically feasible for routine assessment and monitoring. In this context, a surrogate marker for cerebral perfusion during CPR is highly desirable. Yet, cerebral blood flow hemodynamic determinants remain poorly understood and their significance might be altered by changes in head positioning such as flat, head up, and head down during CPR. Hypothesis: We hypothesized that routinely measured hemodynamic parameters would correlate with cerebral brain flow during CPR, independently of the head position. Methods: Associations between cerebral blood flow, measured using microsphere techniques, and hemodynamic parameters were studied from two prior publications. Eight pigs receiving CPR with an automated device and an impedance threshold device in the flat or supine, whole body head down and whole body head up tilt positions were analysed for the derivation sample. Relevant associations were examined for consistency in an external validation sample consisting of 18 pigs randomized to supine position versus head and torso elevation. Results: After adjusting for position, arterial blood pressure and cerebral perfusion pressure during decompression were significantly associated with cerebral blood flow, in the derivation and the external validation samples. No significant associations were found between cerebral blood flow during CPR and right atrial pressure, intracranial pressure, end tidal CO₂, carotid blood flow, and coronary perfusion pressure in the derivation sample. Conclusion: Decompression arterial blood pressure and cerebral perfusion pressure are relevant candidate surrogate markers for cerebral blood flow during CPR, independently of head position.