Colon blood flow in the dog: effects of changes in arterial carbon dioxide tension

A new method for measuring blood flow in the colon using a 133Xenon clearance technique has been developed in the greyhound. Values for 133Xe tissue blood partition coefficient for colon have been established. The mean basal colon blood flow in 35 animals was 39.8 cm3.min-1.100g-1 with a coefficient of variation for repeat measurements of 8.7%. Hypercapnia produced a significant rise in colon blood flow to a mean maximum level of 62.2 cm3.min-1.100g-1 and hypocapnia a significant fall to a mean level of 27.9 cm3.min-1.100g-1. For arterial carbon dioxide tension (PCO2) values between 2 and 12 kPa (15 and 90 mmHg) there was a straight line relationship between colon blood flow and arterial PCO2. When hypercapnia was prolonged for 75 min, the initial rise in colon blood flow was only partially sustained, while prolonged hypocapnia for a similar period resulted in sustained reduction in flow. Mean resting colon oxygen consumption in 35 animals was 1.17 cm3.min-1.100g-1 and this was not significantly affected by hypocapnia. Hypercapnia to arterial PCO2 levels between 8 and 14 kPa (60 and 105 mmHg), however, produced a significant rise in colon oxygen consumption. Since changes in colon blood flow during and after surgery may affect healing of colonic anastomoses, these results may be relevant when considering anaesthetic techniques for patients undergoing colon resection.