Comparison of Intraoperative Sedation With Dexmedetomidine Versus Propofol on Acute Postoperative Pain in Total Knee Arthroplasty Under Spinal Anesthesia: A Randomized Trial

BACKGROUND: In patients undergoing total knee arthroplasty under spinal anesthesia, we compared the postoperative analgesic effect of intraoperative sedation with dexmedetomidine versus propofol. We hypothesized that sedation with dexmedetomidine would result in lower postoperative opioid analgesic consumption than with propofol. METHODS: Forty-eight patients were enrolled and randomly assigned to either a dexmedetomidine group (n = 24), which received a loading dose of 1 μg/kg dexmedetomidine over 10 minutes, followed by a continuous infusion of 0.1–0.5 μg·kg −1 ·hour −1 , or a propofol group (n = 24), which received a continuous infusion of propofol via a target-controlled infusion to maintain the effect-site concentration within a range of 0.5–2.0 μg/mL. The drug infusion rate was determined according to the sedation level, targeting a modified observer’s assessment of alertness/sedation score of 3 or 4. The cumulative amounts of fentanyl administered via intravenous patient-controlled analgesia were recorded at 24 and 48 hours postoperatively (primary outcome). The postoperative numerical rating scale for pain was assessed at 6, 12, 24, and 48 hours (secondary outcome). The postoperative use of additional rescue analgesic (ketoprofen) and antiemetic drugs was also compared between the 2 groups at 24 and 48 hours. RESULTS: Dexmedetomidine significantly reduced postoperative fentanyl consumption (median [interquartile range]) during 0–24 hours (45 [30–71] vs 150 [49–248] μg, P = .004; median difference = −105 μg [99.98% CI, 210–7.5]), 24–48 hours (90 [45–143] vs 188 [75–266] μg, P = .005; median difference = −98 μg [99.98% CI, 195–45]), and 0–48 hours (135 [68–195] vs 360 [146–480] μg, P = .003; median difference = −225 μg [99.98% CI, 405–7.5]). The numerical rating scale (median [interquartile range]) was lower at 6 hours (1 [0–2] vs 2 [1–3], P = .003), 12 hours (1 [1–2] vs 3 [2–3], P < .001), 24 hours (1 [1–2] vs 3 [2–3], P < .001), and 48 hours (2 [2–3] vs 3 [3–4], P < .001) after surgery in the dexmedetomidine group compared to the propofol group. No significant intergroup differences were observed in the amount of rescue analgesics and antiemetics at 24 hours ( P = .155 and P = .482) and 48 hours ( P = .082 and P = .153) after surgery. CONCLUSIONS: Intraoperative dexmedetomidine sedation was associated with a small but clinically important reduction in postoperative opioid use after total knee arthroplasty.