Does lidocaine as an adjuvant to morphine improve pain relief in patients presenting to the ED with acute renal colic? A double-blind, randomized controlled trial.

OBJECTIVE: Renal colic (RC) is a common clinical presentation in the emergency department (ED). Prompt and effective pain control is one of the first responsibilities of emergency physicians. The aim of this study was to evaluate the analgesic effect of adding lidocaine to morphine compared to morphine alone in patients presenting to the ED with RC.

METHODS: In a double-blind, randomized controlled trial, a total of 110 adult patients of both sexes, aged 18 to 50 years, who presented to the ED with signs and symptoms suggestive of RC were randomly assigned into 1 of 2 groups. Patients in group A received morphine (0.1 mg/kg) plus lidocaine (1.5 mg/kg), whereas those in group B received morphine (0.1 mg/kg) plus normal saline 0.9% as placebo. All patients were asked to rate the intensity of their pain and nausea on a 0- to 10-point visual analog scale before and at 5, 10, 30, 60, and 120 minutes after intervention.

RESULTS: There was a statistically significant time trend decline in both groups for both pain and nausea scores (P < .01). Repeated-measures analysis showed a significant effect for the interaction between group and time of persistent pain (P = .034), but there was no significant group effect in this regard (P = .146). Median times to being pain free in the group receiving morphine plus lidocaine and in the group taking morphine alone were 87.02 minutes (95% confidence interval [CI], 74.23-94.82) and 100.12 minutes (95% CI, 89.95-110.23), respectively (P = .071). Repeated-measures analysis also showed a significant group effect for nausea (P = .038), but there was no interaction between group and time in this regard (P = .243). The median nausea-free times in the group receiving morphine plus lidocaine and the group receiving morphine alone were 26.6 minutes (95% CI, 14.16-39.03) and 58.33 minutes (95% CI, 41.85-74.82), respectively. This time difference was statistically significant (P < .001).

CONCLUSIONS: Using lidocaine may be recommended as an effective, safe, and inexpensive adjuvant to morphine in improving nausea and reducing the time needed to achieve pain and nausea relief in patients visiting the ED with acute RC.