Late-onset preemptive analgesia associated with preincisional large-dose alfentanil.

Abstract

Few studies using systemic opioids have been adequately designed to demonstrate a preemptive effect. We investigated the preemptive effect of intraoperative large-dose intravenous (I.V.) opioids over a 72-h period after lower abdominal surgery. Thirty-eight ASA physical status I or II patients undergoing abdominal hysterectomy were studied in a prospective, randomized, double-blind design. Group PRE received alfentanil 70 microg/kg over 10 min before surgical incision; Group POST received alfentanil 70 microg/kg over 10 min after incision. Patients received no other intraoperative opioid. Pain was treated in the recovery room with 2-mg I.V. boluses of morphine and was subsequently managed via patient-controlled analgesia (PCA) using morphine sulfate. Visual analog scale pain scores at rest (VAS-R) and on movement (VAS-M) and PCA morphine consumption were recorded for 72 hours. VAS-M and VAS-R scores did not differ at any point, and morphine consumption was similar in both groups over the initial 48 h. Group PRE used significantly less morphine from 48 to 72 h postoperatively (P < 0.02). We conclude that presurgical incisional (i.e., compared with postincisional) large-dose opioid exposure results in a modest, late decrease in postoperative morphine consumption, with no clinical impact on early postoperative pain. Timing of the observed reduction coincides with maximal output of substances implicated in experimental hyperalgesia. When given before surgical incision, alfentanil, a short-acting narcotic, was associated with a reduction in morphine requirements 48-72 h after surgery. Brief interventions may have a delayed and sustained impact on pain perception, possibly by reducing mechanisms of sensitization.