Canine coronary blood flow responses to hypoxaemia: the influence of halothane

Electromagnetic flow meters were used to measure blood flow in the coronary and pulmonary arteries of six anaesthetized dogs following thoracotomy. Halothane 1% (v/v) caused a reduction in arterial pressure, coronary artery flow, cardiac output and myocardial and total body oxygen consumption and an increase in coronary vascular resistance. Hypoxaemia caused large increases in coronary artery flow during both cardiac systole and diastole, but not until PaO2 was less than 5.3 kPa. This response was not influenced by the presence of halothane. Although myocardial oxygen availability and consumption were maintained during hypoxaemia, total body oxygen availability and consumption were markedly reduced.