Cardiac and peripheral arterial responses to isoprenaline challenge

Changes in 1) heart rate, 2) brachial blood pressure, and 3) ankle systolic blood pressure, have been measured together with 4) diameter, 5) mean blood velocity, and 6) mean volume flow in the common femoral and posterior tibial arteries in normal volunteers following intravenous infusions of isoprenaline. A total of 70 studies in 15 normal volunteers were carried out using a sequence of three increasing doses of isoprenaline. Significant increases were observed in 1) heart rate, 2) brachial systolic blood pressure, and 3) femoral artery diameter, mean blood velocity and volume flow (p less than 0.001). Significant decreases were observed in 4) brachial diastolic pressure, and 5) ankle systolic pressure (p less than 0.001). In the posterior tibial artery, the diameter increased significantly at the highest isoprenaline dose but changes in velocity and volume were not significant. This investigation shows reproducible cardiovascular responses to intravenous isoprenaline in normal volunteers. Different responses were observed between the common femoral and posterior tibial arteries. Blood flow volume and velocity increased significantly in the femoral artery, whilst there was a trend towards an increase in volume blood flow with a decrease in velocity blood flow in the posterior tibial artery site. This difference between the two peripheral arteries is presumably due to a difference in the area of supply of the two arteries, the larger vessel predominately supplying muscle and the smaller vessel skin. Thus there may be either a different pattern of reflex outflow activity, and/or differences in the beta-adrenoceptor population of the sites supplied by the femoral and posterior tibial arteries.