Intravenous Lidocaine Decreases Pain Scores 24 Hours Post Cardiac Surgery: Substudy of a Randomized Controlled Trial

Post cardiac surgery pain remains a problem for a significant number of patients. While opioids have long been used for cardiac surgery pain control and hemodynamic stability, methods to improve pain control while also reducing reliance on opioids are desired. Intravenous lidocaine has shown promise for pain and opioid reduction in multiple operative settings, yet its role in cardiac surgery lacks conclusive data.

To determine the effect of intravenous lidocaine on pain scores and opioid consumption in the first 48 hours post cardiac surgery.

Preplanned substudy of a single-center, double-blind, placebo-controlled, randomized controlled trial.

This study was conducted in a tertiary/quaternary care academic hospital in the United States.

Following institutional review board approval and informed consent, a total of 449 patients who met the inclusion criteria were enrolled and randomized to receive either a bolus of one mg/kg of lidocaine administered after anesthesia induction followed immediately by a continuous infusion at 48 mu-g/kg/min for the first hour, 24 mu-g/kg/min for the second hour, and 10 mu-g/kg/min for the next 46 hours (lidocaine group) or normal saline (placebo group). Primary outcomes were Visual Analog Scale (VAS) scores and opioid consumption in of morphine milligram equivalents at 24 and 48 hours post surgery. Secondary endpoints included the administration of other nonopiod analgesic medications, postoperative antiemetic medication use, intensive care unit length of stay, hospital length of stay, and time to return of bowel function. Univariable and multivariable regression analyses were performed.

A total of 215 patients who received a placebo and 218 patients who received lidocaine were evaluated. We observed a statistically significant difference in VAS pain score at postoperative 24 hours (adjusted mean difference -0.68; 95%CI, -1.23 to 0.13; P = 0.016) between patients treated with lidocaine vs placebo; however, no difference was observed at postoperative 48 hours. The cumulative opioid use in morphine milligram equivalents was not significant, both in univariable and multivariable analysis, at all timepoints between patients receiving lidocaine vs placebo. Among secondary outcomes, the only significant effect was a decrease in odds of acetaminophen use in the first postoperative 48 hours (adj. odds ratio 0.54; 95% CI 0.32 to 0.90, P = 0.018).

Although pain scores were a preplanned outcome of the parent study, opioid consumption was not. Furthermore, postoperative pain management was not specifically standardized for this study.

We found that intravenous lidocaine resulted in a statistically significant decrease in VAS pain scores at 24 hours post cardiac surgery, with no difference in opioid consumption. While this pain benefit has been noted in other surgical patient populations, our findings are important since patients undergoing cardiac surgery are unique given the physiologic changes associated with cardiopulmonary bypass graft.