HYPERBARIC-OXYGEN LIMITS INFARCT SIZE IN ISCHEMIC RABBIT MYOCARDIUM IN-VIVO

Background. We explored the ability of increased oxygen pressure to mo dify necrosis in an open-chest rabbit model of myocardial ischemia and reperfusion. Methods and Results. A branch of the left coronary arter y was occluded for 30 minutes followed by 3 hours of reperfusion. Infa rction was measured by triphenyl tetrazolium staining and expressed as a percentage of the ischemic zone. Untreated rabbits were ventilated with 100% oxygen at 1 atm absolute. Treatment animals were exposed to hyperbaric oxygen at 2.5 atm absolute. The 1.0-atm control hearts deve loped 41.5+/-4.6% infarction of the ischemic zone. Animals exposed to hyperbaric oxygen during ischemia only, reperfusion only, or ischemia and reperfusion had significantly smaller infarcts with respect to con trol animals (15.2+/-2.9%, 14.5+/-3.7%, and 9.8%+/-2.7%, respectively; P less-than-or-equal-to .01), indicating that they had been protected by the procedure. When hyperbaric oxygen was begun 30 minutes after t he onset of reperfusion, no protection was seen (35.8+/-3.8%). Conclus ions. We conclude that hyperbaric oxygen limits infarct size in the re perfused rabbit heart and that the effect can be achieved when hyperba ric oxygen is begun at reperfusion.