Comparison between bupivacaine–dexmedetomidine mixture and bupivacaine–magnesium mixture when used for wound infiltration before skin incision in surgeries for hernia repair regarding their intraoperative and postoperative analgesic effects

Background
Wound infiltration with local anesthetics was developed to provide intraoperative and postoperative analgesia and to reduce opioid consumption and its side effects.
Methods
This is a prospective randomized, double-blinded study. A total of 45 patients, American Society of Anesthesiologists physical status I–II, aged from 18 to 60 years scheduled for open abdominal surgeries were randomly assigned to one of the following groups to receive wound infiltration 2 min prior to skin incision: group I: bupivacaine 0.25% alone (20 ml) ( = 15), group II: bupivacaine 0.25% + magnesium sulfate (1 g) (20 ml) ( = 15), and group III: bupivacaine 0.25% + dexmedetomidine (70 μg) (20 ml) ( = 15). Induction and maintenance were done according to our hospital protocol. Heart rate (HR) and systolic blood pressure (SBP) at baseline and every 15 min till the end of surgery, the need for supplemental fentanyl, and the concentration of inhalational anesthetic were assessed. Postoperatively, Ramsay sedation scale was assessed 10 min post extubation and every 30 min for 6 h; visual analog scale was assessed at rest and every 30 min for 6 h postoperatively; time to the first request of analgesia and the cumulative analgesic consumption were recorded; HR and SBP were recorded for 6 h.
Results
The concentration of inhalational isoflurane and the need for supplemental fentanyl intraoperatively were significantly lower in group III than in groups I and II. Postoperatively in group III, HR and SBP and visual analog scale scores were significantly lower compared with groups I and II. Ramsay sedation score was significantly higher in group III up to 2 h after recovery in comparison to groups I and II. Group III showed longer time for the first request of analgesia and a lower need for postoperative opioids in comparison to groups I and II.
Conclusions
Wound infiltration with dexmedetomidine–bupivacaine mixture before skin incision decreases the anesthetic requirements, provides prolonged analgesia, and decreases the need for rescue analgesics in patients undergoing open abdominal surgeries.