The effects of a minor degree of hypovolaemia on colonic blood flow and on systemic haemodynamics have been studied in nine greyhound dogs. A loss in blood volume of 10 per cent over 20 min produced no change in blood pressure and only a 7 per cent rise in heart rate. Cardiac output, however, fell by 26 per cent and central venous pressure also fell significantly. Colonic blood flow fell by 28 per cent and oxygen availability by 29 per cent. All these changes were statistically highly significant. Retransfusion of shed blood resulted in a slow and incomplete return to pre-bleed status. Since colonic blood flow and oxygen availability during and after surgery may be important for colonic healing, it is suggested that even the slightest degree of hypovolaemia should be avoided in cases involving colonic anastomosis. Systemic blood pressure may be an inadequate index of the need for transfusion in these cases.

No abstract

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.

A merhod of protwine rirrarion, with rhe use of rhe 'Haemochron 400' system for reversal of heparmisarion ajler cardiopuhonary bypass is described. Twenty-three patients. average age 4 7 years. &going this procedure for either valve replacement or coronary artery bypass grafring were studied. Accurare reversal of heparinisation was achieved using comparative& small doses of protamine. A linear relationship between the dose ratio of protamine and heparin and rhe time interval between their respective ahinistrations was akjined where only a single dose of heparin had been administered. Key wonkBlood; anticoagulation, heparin. Measurement technques; protarnine requirements.Rotamine sulphate was introduced as an antagonist to heparin in 1937' and has become widely used for this purpose since the advent of cardiopulmonary bypass techniques. This drug, however, also has an anticoagulant property which was described 36 years prior to its introduction as a heparin antagonist.* Rotamine titration methods, originally des- who described only minimal short term effects on the coagulation system after protamine ovcrdoses of up to 800 mg per 70 kg subject. It has, however, been the experience of the authors that the anticoagulant property of protamine can be produced after considerably smaller doses have been administered for the reversal of heparinisation. MetbodHeparin was administered intra-operatively as a bolus intravenous dose of 3.0 mg/kg body weight prior to the insertion of the aortic, superior vena caval, and inferior vcna caval cannulae. An additional 80 mg heparin was added to the pump priming volume of two litres of Ringers lactate solution. Monitoring of the degree of anti--

No abstract