Intravenous acetaminophen analgesia after cardiac surgery: A randomized, blinded, controlled superiority trial

Pain after cardiac surgery traditionally has been controlled by intravenous opioids and nonsteroidal antiinflammatory drugs. An intravenous analgesic with fewer adverse effects is needed. Therefore, we tested the primary hypothesis that intravenous acetaminophen is more effective than placebo for pain management, which was defined a priori as superior on either pain intensity score and/or opioid consumption and not worse on either.

In this single-center, double-blind trial, 147 patients having cardiac surgery via median sternotomy were randomized to receive either 1 g of intravenous acetaminophen (73 patients) every 6 hours for 24 hours or comparable placebo (74 patients) starting in the operating room after sternal closure. Cumulative opioid consumption (in morphine equivalents) and pain intensity scores (on a 0-10 Numeric Rating Scale) were measured at 4, 6, 8, 12, 16, 20, and 24 hours after surgery. We estimated ratio of mean opioid consumption by using multivariable linear regression (noninferiority delta = 1.15) and pain score difference by using repeated measures regression (noninferiority delta = 1).

Acetaminophen was superior to placebo on mean pain intensity scores and noninferior on opioid consumption, with estimated difference in mean pain (95% confidence interval) of -0.90 (-1.39, -0.42), P < .001 (superior), and estimated ratio of means in opioid consumption (90% confidence interval) of 0.89 (0.73-1.10), P = .28 (noninferior; not superior).

Intravenous acetaminophen reduced pain after cardiac surgery, but not opioid consumption. Intravenous acetaminophen can be an effective analgesic adjunct in patients recovering from median sternotomy.