THE EFFECT OF EPIDURAL-ANESTHESIA WITH 1-PERCENT LIDOCAINE ON THE PRESSOR-RESPONSE TO DYNAMIC EXERCISE IN MAN

1. In order to examine the sensitivity to local anaesthetics of affere nt neural feedback from working muscle during dynamic exercise, sixtee n subjects cycled for 12 min before and after epidural anaesthesia usi ng 1 % lidocaine. The presence of afferent neural blockade was verifie d by elimination of the blood pressure response to a cold pressor test , laser-induced evoked potentials and increases in pain detection and tolerance thresholds of the foot. Conversely, epidural anaesthesia had no effect on these variables in the unblocked skin areas or on electr ically evoked potentials in blocked or unblocked skin. 2. During dynam ic exercise, heart rate increased as did mean arterial pressure and ca rdiac output. Mean arterial pressure remained at the exercise level du ring post-exercise ischaemia, but heart rate and cardiac output decrea sed while total peripheral resistance increased. Epidural anaesthesia did not significantly affect these variables during rest, dynamic exer cise, post-exercise ischaemia or recovery. 3. The results of this stud y show that, in order to affect blood pressure during dynamic exercise , epidural anaesthesia must block the pressor response to post-exercis e ischaemia. The implication of these data is that complete or almost complete block of group III and/or group IV muscle afferents is necess ary to inhibit the pressor response to dynamic exercise in man.