Hemodynamic Effects of Hyperbaric Oxygenation in Experimental Acute Myocardial Infarction
The hemodynamic effects of hyperbaric oxygenation were investigated in anesthetized dogs with acute myocardial embolism and infarction produced by injecting plastic spheres 325 micra in diameter. In 50 "control" animals with acute myocardial infarction induced while breathing either air at one atmosphere, 100% oxygen at one atmosphere or 7% oxygen at three atmospheres, 24-hour mortality was 85 to 90%. In 23 animals that received the same dose of microspheres and breathed 95 to 100% oxygen at three atmospheres for two hours following embolization, there was significantly less 24-hour mortality (30%), less ventricular fibrillation, and less advanced atrioventricular block. Hyperbaric oxygenation afforded protection against immediate mortality from ventricular fibrillation and also against later death, in shock, occurring within 24 hours of coronary embolization but after the immediate postembolization period had passed. In the animals exposed to hyperbaric oxygenation, declines of cardiac output and of central aortic pressure occurring 60 and 90 minutes after coronary embolization were significantly less than in the other animals.
In normal animals, hyperbaric oxygenation reduced cardiac output moderately, increased systemic vascular resistance, and elevated aortic pressure slightly.
The anatomic extent of the infarction did not differ detectably between the "control" animals and those treated with hyperbaric oxygenation.
It is concluded that hyperbaric oxygenation provides protection against mortality in the early period after coronary embolization by preventing ventricular fibrillation. In addition, prevention of major declines in aortic pressure and cardiac output during the later postembolization period in the group with hyperbaric oxygenation was associated with diminished rates of late mortality.
- Accepted November 16, 1964.
- © 1965 American Heart Association, Inc.