QUANTITATIVE SENSORY EXAMINATION OF EPIDURAL-ANESTHESIA AND ANALGESIAIN MAN - COMBINATION OF MORPHINE AND BUPIVACAINE

The effect of epidural administration of a combination of low-dose mor phine (2 mg and bupivacaine (25 mg) on somatosensory and motor functio ns was examined in 13 healthy volunteers. The study design was a doubl e-blind 4-way cross-over in which combined treatment was compared with either drug used alone or placebo. Every 2nd hour for 10 h effects on nociceptive and non-nociceptive somatosensory functions were quantifi ed with 12 psychophysical measures. In addition knee extension strengt h, reaction time and skin temperature were examined. Epidural bupivaca ine had hypoalgesic effect in all nociceptive tests, whereas epidural morphine only demonstrated hypoalgesic properties in nociceptive test with prolonged stimuli. In comparison with bupivacaine alone the combi nation treatment had a lesser peak effect but a more prolonged hypoalg esic action. In comparison with morphine alone the combination treatme nt induced a faster onset and demonstrated a modest increase in hypoal gesic effect in a subset of the test, even beyond the duration of bupi vacaine when administered alone. Motor function was not attenuated by any of the treatments. Mechanisms of interaction between morphine and bupivacaine as well as their possible clinical implications are discus sed.