Background: Intravenous lidocaine is an emerging analgesic for use in the emergency department. ED studies have shown it to be superior to morphine for renal colic and acute limb ischemia, equivalent to ketorolac for back pain, and effective for treating general severe pain. No study has compared it to hydromorphone in patients with abdominal pain. The goal of this study was to compare intravenous lidocaine against hydromorphone for acute non-specific abdominal pain.
Methods: This was a prospective, randomized, double-blind clinical trial comparing intravenous lidocaine to hydromorphone for patients between the ages of 18-65 who had pain severe enough to warrant the use of an intravenous opioid. Patients were excluded if they weighed less than 60 kg or more than 120 kg, this was done to approximate a 1.5mg/kg dose. Patients were also stratified according to suspicion for renal colic. Patients in the lidocaine arm received 120 mg over 10 minutes and patients in the hydromorphone arm received 1 mg over 10 minutes. Patients were eligible for a repeat dose at 30 minutes. The primary outcome was difference in numerical pain score between 0 and 90 minutes. Secondary outcomes were need for off-label pain medications, numerical pain scores at 30, 45, 60, 120 and 180 minutes as well as side effects, serious adverse events, and patient preference for treatment medication.
Results: 154 patients were enrolled. That mean numerical pain difference for lidocaine was 3.8 and 5.0 for hydromorphone at 90 minutes (1.2, 95%CI: 0.3, 2.2). There was no difference between side effects and serious adverse events. More patients preferred hydromorphone over lidocaine. Patients with renal colic had a change in numerical pain score of 3.4 with lidocaine compared to 6.4 with hydromorphone (3.0, 95%CI: 0.5, 5.5). In a subset of patients who received approximately a 2 mg/kg dose of lidocaine, improvement in pain score was 5 (95%CI: 3.8, 6.2).
Conclusion: Intravenous lidocaine at a dose of 120mg is not superior to 1mg of hydromorphone for treating acute non-specific abdominal pain. This effect was more pronounced for patients with renal colic, a significant difference compared to previous research on lidocaine for renal colic. Future studies should use a dose of 2mg/kg as it appeared to be equally efficacious to hydromorphone and without any adverse effects.