Intramural PCO2: a reliable index of the severity of myocardial ischemic injury.

The present study was performed to evaluate the usefulness of changes in intramural oxygen (PmO2) and carbon dioxide (PmCO2) tensions shortly after coronary artery occlusion as indices of the severity of myocardial ischemic injury. In 14 open-chest, anesthetized dogs, a 60-min coronary artery occlusion was performed, during which PmO2 and PMCO2 were measured continuously with a mass spectrometer. Regional myocardial blood flow (RMBF) adjacent to the mass spectrometer probes was measured by the xenon-127 washout technique both before and 30 min after coronary artery occlusion. At the end of 60 min of occlusion, the dogs were killed, and biopsies for histological examination of 1-micron-thick sections were obtained from the tissue surrounding each mass spectometer probe. The decline in PmO2 during the 60-min occlusion bore no relationship either to the severity of ischemic injury as assessed by histological examination, or to the reduction of RMBF. In contrast, the magnitude of rise in PmCO2 during the 60 min of occlusion corresponded closely to both the severity of injury assessed histologically and the reduction of RMBF.