A randomised controlled trial of intravenous dexmedetomidine added to dexamethasone for arthroscopic rotator cuff repair and duration of interscalene block

Abstract

Prolongation of peripheral nerve blockade by intravenous dexamethasone may be extended by intravenous dexmedetomidine. We randomly allocated 122 participants who had intravenous dexamethasone 0.15 mg.kg^-1 before interscalene brachial plexus block for day-case arthroscopic rotator cuff repair to intravenous saline (62 participants) or intravenous dexmedetomidine 1 μg.kg^-1 (60 participants). The primary outcome was time from block to first oral morphine intake during the first 48 postoperative hours. Fifty-nine participants reported taking oral morphine, 25/62 after placebo and 34/60 after dexmedetomidine, p = 0.10. The time to morphine intake was shorter after dexmedetomidine, hazard ratio (95%CI) 1.68 (1.00-2.82), p = 0.049. Median (IQR [range]) morphine doses were 0 (0-12.5 [0-50]) mg after control vs. 10 (0-30 [0-50]) after dexmedetomidine, a difference (95%CI) of 7 (0-10) mg, p = 0.056. There was no effect of dexmedetomidine on pain at rest or on movement. Intra-operative hypotension was recorded for 27/62 and 50/60 participants after placebo vs. dexmedetomidine, respectively, p < 0.001. Other outcomes were similar, including durations of sensory and motor block. In conclusion, dexmedetomidine shortened the time to oral morphine consumption after interscalene block combined with dexamethasone and caused intra-operative hypotension.

Keywords: local anaesthetic adjuncts; peripheral nerve block; postoperative analgesia; regional anaesthesia.

Figure 1

Study flow diagram.

Figure 2

Kaplan–Meier estimates of time from interscalene block to first oral morphine intake in the first 48 h after day‐case arthroscopic rotator cuff repair, after pre‐operative intravenous saline (blue line) vs. intravenous dexmedetomidine (red line). Line lengths outside the grey shaded area differ at the 95%CI level.

Figure 3

Postoperative pain scores (a) at rest and (b) on movement. Values are mean (95%CI). There were no significant effects of dexmedetomidine on pain at rest, p = 0.68, or on movement, p = 0.40.