Reactive Hyperaemia in the Human Calf after Long-Lasting Ischaemia

Abstract

To study reactive hyperaemia in the lower human limb after extended circulatory arrest, blood flow in the calf of 20 patients was measured by strain gauge plethysmography after operations performed in a'bloodless field'. Mean time of ischaemia was 65 min. In 10 patients (group A) the limbs were exsanguinated by a rubber Esmarch bandage before the tourniquet was applied. In another 10 patients (group B) ischaemia was induced after only leg elevation. Epidural anaesthesia caused a significant increase in basal calf flow but did not change maximal flow significantly. This indicates that ischaemia induces a maximal flow of a certain magnitude, which is not related to the level of basal flow. Reactive hyperaemia after 1 h of occlusion compared with 3 min of ischaemia increased mainly by extending recovery time and repayment, which may be attributed to accumulated metabolites maintaining vasodilation. The increase in maximal flow was moderate, which supports the view that the time-response curve for maximal flow shows an exponential-like pattern. The delay of maximal flow observed in most limbs after 1 h of ischaemia may be due to a no-reflow phenomenon. Recovery time (21.4 min) and repayment (184 ml/100 ml) in group A were significantly greater than in group B, whereas maximal flow in groups A and B was 29.4 and 27.8 ml/min/100 ml, respectively, an insignificant difference. Thus, the amount of blood present in the limb during ischaemia may influence reactive hyperaemia, although the maximal postischaemic vasodilation of arterioles is not affected. After 3 min of ischaemia a standard pattern of reactive hyperaemia was recorded, whereas after extended circulatory arrest mainly a biphasic and plateau type of hyperaemic curve was observed.

Key Words:

• Blood pressure
• calf flow
• epidural anaesthesia
• postischaemic vasodilation
• tourniquet