QUANTITATIVE SENSORY EXAMINATION OF EPIDURAL-ANESTHESIA AND ANALGESIAIN MAN - DOSE-RESPONSE EFFECT OF BUPIVACAINE

Time and dose-response functions of 4 concentrations of epidural bupiv acaine (0.075, 0.125, 0.25, and 0.5%; 20 ml) on somatosensory and moto r functions were examined in 10 healthy volunteers. Every hour for 8 h the effect of epidural bupivacaine on perception of painful and non-p ainful stimuli was quantified with 12 psychophysical measures. In addi tion knee extension strength, reaction time and skin temperature were examined. The two lowest concentrations of bupivacaine induced hypoalg esia without impairment of motor function. Epidural bupivacaine produc ed differential blockade of non-painful somatosensory functions in the following order: warmth perception > cold perception > perception of electrical stimuli. Epidural bupivacaine induced more pronounced hypoa lgesia for short-lasting than for prolonged stimuli. A modality-relate d blocking order was observed for prolonged painful stimuli: heat > me chanical > electrical. It is suggested that differential blockade of s omatosensory functions is caused by differences both in conduction blo ckade of nerve fibres and in central integration of afferent nerve imp ulses.