MK-801, an Excitatory Amino Acid Antagonist, Does Not Improve Neurologic Outcome following Cardiac Arrest in Cats

The excitatory amino antagonist MK-801 was administered to cats following resuscitation from cardiac arrest to evaluate its effect on neurologic and neuropathologic outcome in a clinically relevant model of complete cerebral ischemia. In 29 cats studied, cardiac arrest (ventricular fibrillation) was maintained for 18 min and resuscitation was successfully performed in 21 cats. Four animals underwent a sham arrest. MK-801 or placebo was administered in a blinded, randomized manner. Beginning at 5 min post resuscitation (PR), MK-801 330 micrograms/kg over 2 min followed by 73 micrograms/kg/h for 10 h or the same volume of placebo was administered. Resuscitated animals remained paralyzed and sedated in an intensive care setting for 24-30 h PR. Neurologic examinations were performed at 2, 4, and 7 days PR by observers blinded to the treatment groups. Seventeen cats were entered into data analysis (nine MK-801-treated and eight placebo-treated). MK-801-treated animals had a significantly greater neurologic deficit score (NDS) rank (0 = normal, 100 = brain death) 2 days PR (mean rank 12.1 vs. 5.6; p = 0.008). This difference is most likely due to ongoing sedative actions of MK-801. There were no significant differences in NDS rank at 4 (10.3, MK-801 vs. 7.5, placebo) and 7 (9.6, MK-801 vs. 8.3, placebo) days PR. There were no significant differences in frontal cortex, hippocampus, occipital cortex, or cerebellar neuropathology between groups. Sham-arrested cats had normal neurologic and neuropathologic evaluations. In the circumstance of complete cerebral ischemia as employed in the current study, MK-801 had no beneficial effect upon neurologic or neuropathologic outcome.