Intravenous lidocaine infusion reduces intrathecal opioid-induced pruritus after cesarean delivery: a randomized controlled trial and proof-of-concept.

BACKGROUND

Pruritus is a common adverse effect of neuraxial morphine after cesarean delivery. We tested whether intravenous lidocaine infusion reduces the incidence and severity of neuraxial morphine-induced pruritus.

METHODS

In this double-blind randomized trial at a single center, 160 women undergoing elective cesarean delivery under spinal anesthesia with intrathecal morphine 150 μg and were randomized to either intravenous lidocaine (bolus 1.5 mg/kg followed by infusion 1.5 mg/kg/h for 6 h) or saline placebo. The primary outcome was the incidence of pruritus within 24 h. Secondary outcomes included pruritus severity over time, rescue nalbuphine use, and adverse events. Analyses used modified intention-to-treat.

RESULTS

Data on 136 patients were analyzed (n = 69 lidocaine vs. n = 67 controls). Pruritus occurred in 36.2% receiving lidocaine vs 73.1% in the control group (absolute risk reduction 36.9%, 95% CI 21.4, 52.4), resulting in a number needed to treat of 3 (95% CI 2, 5). Rescue nalbuphine was given in 23.2% of patients in the lidocaine group vs. 56.7% in the control group (absolute risk reduction 33.5%, 95% CI 18.0, 49.0), with a number needed to treat of 3 (95% CI 2, 6). Pruritus severity was lower in the lidocaine group during the first 12 h postoperatively; differences were not significant at 16 and 24 h. No symptoms of lidocaine toxicity or increased adverse events were observed.

CONCLUSIONS

Intravenous lidocaine infusion reduced the incidence and early severity of neuraxial morphine-induced pruritus after cesarean delivery without increased adverse events. Further work should define lower effective doses and shorter infusion durations compatible with enhanced recovery pathways.