Oximetry-Guided Reoxygenation Improves Neurological Outcome After Experimental Cardiac Arrest

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Abstract
Background and Purpose— Current guidelines suggest that cardiac arrest (CA) survivors should be ventilated with 100% O 2 after resuscitation. Breathing 100% O 2 may worsen neurological outcome after experimental CA. This study tested the hypothesis that graded reoxygenation, with oximetry guidance, can safely reduce FiO 2 after resuscitation, avoiding hypoxia while promoting neurological recovery. Methods— Mature dogs underwent 10 minutes of CA and restoration of spontaneous circulation with100% O 2. Animals were randomized to 1-hour additional ventilation on 100% FiO 2 or to rapid lowering of arterial O 2 saturation to 94% with pulse oximeter guidance. Animals were awakened at hour 23, and the neurological deficit score (0=normal; 100=brain-dead) was measured. Reanesthetized animals were perfusion-fixed and the brains removed for histopathology. Results— The neurological deficit score was significantly better in oximetry (O) dogs. O dogs appeared aware of their surroundings, whereas most hyperoxic (H) animals were stuporous (neurological deficit score=43.0±5.9 [O] versus 61.0±4.2 [H]; n=8, P P 3 ; P Conclusions— A clinically applicable protocol designed to reduce postresuscitative hyperoxia after CA results in significant neuroprotection. Clinical trials of controlled normoxia after CA/restoration of spontaneous circulation should strongly be considered.