CARDIOVASCULAR AND VENTILATORY RESPONSES TO ELECTRICALLY-INDUCED CYCLING WITH COMPLETE EPIDURAL-ANESTHESIA IN HUMANS

Cardiovascular and ventilatory responses to electrically induced dynam ic exercise were investigated in eight healthy young males with affere nt neural influence from the legs blocked by epidurar anaesthesia (25 ml 2% lidocaine) at L3-L4. This caused cutaneous sensory anaesthesia b elow T8-T9 and complete paralysis of the legs. Cycling was performed f or 22.7 +/- 2.7 min (mean, SE) (fatigue) and oxygen uptake (V-o2) incr eased to 1.90 +/- 0.13 l min(-1). Compared with voluntary exercise at the same V-o2, increases in heart rate (HR) (135 +/- 7 vs. 130 +/- 9 b eats min(-1)) and cardiac output (16.9 +/- 1.1 vs. 17.3 +/- 0.91 min(- 1)) were similar, and ventilation (54 +/- 5 vs. 45 +/- 41 min) was hig her (P < 0.05). In contrast, the rise in mean arterial blood pressure during voluntary exercise (93 +/- 4 (rest) to 119 +/- 4 mmHg (exercise )) was not manifest during electrically induced exercise with epidural anaesthesia [93 +/- 3 (rest) to 95 +/- 5 mmHg (exercise)]. As there i s ample evidence for similar cardiovascular and ventilatory responses to electrically induced and voluntary exercise (Strange et al. 1993), the present results support the fact that the neural input from workin g muscle is crucial for the normal blood pressure response to exercise . Other haemodynamic and/or humoral mechanisms must operate in a decis ive manner in the control of HR, CO and VE during dynamic exercise wit h large muscle groups.