Protective effect of hyperbaric oxygen for the temporary ischaemic myocardium. Macroscopic and histological data.

A protective effect of hyperbaric oxygen immediately after reopening of occluded coronary blood flow for the temporary ischaemic myocardial muscle was studied. Thirty dogs were used in this study, and 20 dogs were sacrificed after 4 h and 10 dogs were sacrificed after 5 d. Temporary occlusion of coronary artery (from 30 min to 2 h) was produced by ligation. One group were controls and the other group were a hyperbaric group in which dogs breathed 100% oxygen at an absolute pressure of 2 atmospheres before and after release of coronary ligation. The macroscopic extent of ischaemic area was studied by using nitroblue tetrazolium and microscopic and ECG findings were examined. By breathing oxygen at high pressure immediately after reopening of occluded coronary blood flow, the ischaemic area was markedly reduced. In such cases, some myocardial muscles around the arterioles and sinusoids, even when these vessels existed in the ischaemic area, were kept in a viable state. The repair of necrotic myocardial muscles was promoted histologically. Serious arrhythmia, especially ventricular fibrillation, was also well suppressed, and the stable haemodynamic conditions were obtained during operative procedures. No harmful side effects of hyperbaric oxygen were observed. One of the most effective treatments of acute myocardial infarction involves reconstruction of the occluded coronary artery as soon as possible after the onset of myocardial infarction by using these advantages of hyperbaric oxygen.