Hemodynamic Effects of Small Amounts of Endotoxin in the Bovine

Summary

The effects of 1–10 μg/kg Escherichia coli endotoxin on the pulmonary and systemic circulations were studied in unanesthetized calves. Typically, no change in hemodynamic variables occurred until 8 min had elapsed, after which there was a significant increase in PA pressure and heart rate, a decrease in FA pressure and CO, with no change in LV diastolic or PAW pressures. Arterial pO₂ decreased and pH increased slightly. In calves pretreated with either ASA or IM, endotoxin produced no significant change in PA, PAW, FA, or LV diastolic pressures, CO or HR. Continuous inhalation of 100% O₂ did not modify the effect of endotoxin. Thus, this study indicates that the bovine pulmonary circulation is exceedingly sensitive to minute amounts of endotoxin. The mechanism whereby this response occurs is not clear.