INTRATHECAL INFUSION OF BUPIVACAINE WITH OR WITHOUT MORPHINE FOR POSTOPERATIVE ANALGESIA AFTER HIP AND KNEE ARTHROPLASTY

Postoperative pain after major orthopaedic operations can be controlle d by continuous intrathecal administration of opioids or local anaesth etics. Effective intrathecal analgesia can be achieved through synergi sm of low doses of the two analgesic drugs and, possibly, less drug-re lated adverse effects. Therefore, we have evaluated the usefulness of a combined low-dose bupivacaine and morphine infusion in patients unde rgoing hip and knee arthroplasty. Spinal anaesthesia was induced in 55 ASA I-III patients with 0.5% bupivacaine 2 ml via a 28-gauge spinal c atheter (L3-4 interspace) and 0.5-ml increments were given if needed. Intrathecal 24-h infusions consisted of bupivacaine 2 mg h(-1) alone ( n = 18), bupivacaine 1 mg h(-1) alone (n = 18) or bupivacaine 1 mg h(- 1) combined with morphine 8 mu g h(-1) (n = 19). The interview after 3 , 6, 12 and 24 h included assessment of pain at rest and on movement ( VAS scale), occurrence of sensory and motor block and nausea/vomiting. Bupivacaine 1 mg h(-1) combined with an infusion of morphine provided as good postoperative analgesia as bupivacaine 2 mg h(-1), but motor block disappeared earlier (P = 0.01). Patients in the bupivacaine 1-mg h(-1) group required more supplementary doses of oxycodone i.m. than the other groups (P = 0.04). Time to first oxycodone dose from the sta rt of intrathecal Infusion did not differ between groups. The frequenc y of nausea and vomiting was similar in all groups. In spite of this, antiemetic medication was required more often in the bupivacaine 1-mg h(-1) group (possible because of opioid rescue medication). On the war d, one patient in the bupivacaine 2-mg h(-1) group experienced a new i ncrease in sensory black with concomitant hypotension. One patient in the same group had minor decubitus on the heel of the operated leg, pr obably because of prolonged motor block. We conclude that intrathecal infusion of a combination of bupivacaine 1 mg h(-1) and morphine 8 mu g h(-1) produced adequate postoperative analgesia. Unfortunately, post operative nausea and vomiting was a frequent disturbing adverse effect .