EFFECT OF POSTOPERATIVE EXTRADURAL MORPHINE ON ADH SECRETION

The effect of extradural morphine on antidiuretic hormone (ADH)secretion was assessed for the first 6 h after surgery in threegroups of patients. Surgery was conducted under extradural bupivacaine:thereafter patients in group I (n = 6) received further injectionsof bupivacaine, patients in group II (n = 6) received an extraduralinjection of morphine and in patients in group III (n = 5) bothbupivacaine and morphine, were administered extradurally. Ingroup I, plasma ADH values remained unchanged throughout thestudy. In contrast, in the two groups of patients receivingextradural morphine a delayed and stepwise increase in plasmaADH concentration was documented. These results indicate thatextradural morphine induces ADH secretion and suggest that thiseffect is the consequence of the migration of morphine to thebrainstem.