Comparison of intrathecal versus intra-articular dexmedetomidine as an adjuvant to bupivacaine on postoperative pain following knee arthroscopy: a randomized clinical trial

Abstract

Background: Postoperative pain is a common, distressing symptom following arthroscopic knee surgery. The aim of this study was to compare the potential analgesic effect of dexmedetomidine after intrathecal versus intra-articular administration following arthroscopic knee surgery.

Methods: Ninety patients undergoing unilateral elective arthroscopic knee surgery were randomly assigned into three groups in a double-blind placebo controlled study. The intrathecal dexmedetomidine group (IT) received an intrathecal block with intrathecal dexmedetomidine, the intra-articular group (IA) received an intrathecal block and intra-articular dexmedetomidine, and the control group received an intrathecal block and intra-articular saline. The primary outcome of our study was postoperative pain as assessed by the visual analogue scale of pain (VAS). Secondary outcomes included the effect of dexmedetomidine on total postoperative analgesic use and time to the first analgesic request, hemodynamics, sedation, postoperative nausea and vomiting, patient satisfaction, and postoperative C-reactive protein (CRP) levels.

Results: Dexmedetomidine administration decreased pain scores for 4 h in both the intrathecal and intra-articular groups, compared to only 2 h in the control patient group. Furthermore, there was a significant reduction in pain scores for 6 h in the intra-articular group. The time to the first postoperative analgesia request was longer in the intra-articular group compared to the intrathecal and control groups. The total meperidine requirement was significantly lower in the intra-articular and intrathecal groups than in the control group.

Conclusions: Both intrathecal and intra-articular dexmedetomidine enhanced postoperative analgesia after arthroscopic knee surgery. Less total meperidine was required with intra-articular administration to extend postoperative analgesia to 6 h with hemodynamic stability.

Keywords: Arthroscopic knee surgery; Bupivacaine; Dexmedetomidine; Intra-articular; Intrathecal; Postoperative analgesia.

Fig. 1. CONSORT flow diagram.

Fig. 2. Comparison of visual analogue scale (VAS) of pain in patients' groups. IT: Dexmed intrathecal group, IA: Dexmed intra-articular group, Ctrl: Control group. The mean VAS at 2 h post-intrathecal block was not significant among the three groups. At 4 h post-intrathecal block, control group showed a significantly higher value compared to other 2 groups with no significant differences between IT group and IA group. At 6 h post-intrathecal block, IA group had significant lower VAS compared to other 2 groups. After 8 h, no significant differences among the three groups.

Fig. 3. Hemodynamic changes over 24 hours following intra-thecal injection: (A) Mean Arterial Pressure and (B) heart rate in the three groups. ^*Indicates P < 0.05, ^**Indicates P < 0.01. The mean arterial blood pressure showed a significant reduction from 5 to 30 min post-intrathecal in IT group compared to IA and control groups (A). The heart rate showed significant reduction in IT group from 5 to 15 min post-intrathecal compared to IA and control groups (B). After that and during the postoperative period, no significant differences among the three groups in mean heart rate or mean arterial blood pressure.

Fig. 4. Comparison of serum C-reactive protein (CRP) in patients' groups before and after knee surgery. IT: dexmedetomidine intrathecal group, IA: dexmedetomidine intra-articular group, Ctrl: Control group. No significant differences among the three groups in the preoperative CRP levels. At 24 h, postoperative CRP levels significantly increased in control group compared to IT and IA groups with no significant differences between IT and IA groups.