Absence of a Direct Toxic Action of Endotoxin on Myocardial Tissue
OKLAHOMA UNIV MEDICAL CENTER OKLAHOMA CITY
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The effect of endotoxin on the heart is obscure and results have been controversial. The purpose of the present study was to determine if there was a direct detrimental action of endotoxin on cardiac tissue. An isolated heart and ventilated lungs removed from a donor dog were perfused with venous blood from an intect heparinized animal. Pulmonary blood flow, aortic pressure, respiration, and blood temperature were maintained constant in the isolated preparation. Cardiac output was directly measured from aortic and coronary venous outflows. Left ventricular myocardial contractile force, intraventricular and aortic pressure and oxygen uptake were determined. An LD90 injection of E. coli endotoxin was intravenously administered to the dog. Results indicate that endotoxin has no detrimental effect on the isolated heart under the conditions of these experiments. Oxygen uptake and left ventricular contractile force were maintained at pre-endotoxin values or increased above control in the presence of severe systemic hypotension in the dog. Left ventricular end diastolic pressure was not elevated in any experiment but ordinarily decreased after endotoxin. Coronary blood flow progressively increased and vascular resistance significantly fell. No regular relationship between heart rate and coronary resistance was observed. In conclusion, there was no evidence to support a direct toxic action of endotoxin on myocardial tissue.
- Anatomy and Physiology
- Medicine and Medical Research