Standardised isoprenaline sensitivity tests--a comparison of existent methods.

1 Six healthy subjects (four male, two female, aged 19-24 years) received intravenous boluses of isoprenaline sulphate by two standardised methods of injection (Cleaveland et al., 1972; George et al., 1972). Heart rate changes were analysed by three different methods. 2 The I25 (dose of isoprenaline required to increase the heart rate by 25 beats/min) was not significantly altered by either the method of injection or the method of heart rate measurement. 3 The slope of the heart rate dose response curve was significantly steeper when isoprenaline was injected in a fixed 2 ml volume through a three-way tap, and when the heart rate was measured from the shortest three R-R intervals. 4 However the differences in method of injection and heart rate measurement between the two techniques do not appear to produce major alterations in the results obtained, particularly the I25.