Abstract 209: The Incidence and Determinants of Brain Tissue Hypoxia in Cardiac Arrest Survivors with Severe Neurological Injury
Introduction: After cardiac arrest (CA), the American Heart Association recommends weaning inspired oxygen (FiO2) “to achieve an arterial oxygen saturation [SaO2]≥94%...to avoid potential oxygen toxicity.” This risks inadequate cerebral oxygen delivery. We hypothesized that brain tissue hypoxia (BTH) would occur commonly in severely brain injured post-CA patients and be more frequent when SaO2 was <98%. We further hypothesized that arterial oxygen tension (PaO2) and mean arterial pressure (MAP) would be determinants of brain tissue oxygen (PbtO2).
Methods: We monitor intracranial pressure (ICP), temperature, PbtO2 and jugular venous oxygen saturation in patients with severe neurological injury (extensor posturing or worse) after CA. We collected data hourly and defined BTH as PbtO298% vs 94-98%. We used generalized estimating equations to test the correlation of ICP, temperature, time from arrest, PaO2, MAP, arterial oxygen content and PaCO2 with PbtO2, then constructed an adjusted model using predictors with an unadjusted P98% (P<0.001). Predictors of PbtO2 that persisted after adjustment (P <0.01) were time, PaO2 and MAP. The median a-B gradient was 119mmHg (IQR 83-162mmHg) but fell rapidly over the first 24h.
Conclusion: In severely injured post-CA patients, BTH occurs frequently, appears to be delivery responsive, and occurs more commonly when SaO2 is 94-98%. The risk-benefit ratio between limiting BTH vs. limiting hyperoxia must be carefully considered in light of existing guidelines in these severely injured patients.
Author Disclosures: J. Elmer: None. L. Shutter: None. D. Okonkwo: None. J.C. Rittenberger: None. C.W. Callaway: None. C. Dezfulian: None.
- © 2014 by American Heart Association, Inc.