IV Acetaminophen Does Not Reduce Post-op Hypoxemia In Randomized Trial

In patients who underwent abdominal surgery, IV acetaminophen did not reduce the duration of postoperative hypoxemia compared with placebo in a randomized, double-blind trial.

In the trial, IV acetaminophen did not significantly reduce postoperative pain, and it reduced opioid consumption by 14%, or 4 mg per day, an amount that was neither statistically significant nor clinically important.

“The study findings do not support the use of intravenous acetaminophen for this purpose,” concluded the authors from Cleveland Clinic, led by Alparslan Turan, MD, a professor of anesthesiology and the vice chair of outcomes research at the anesthesiology institute of Cleveland Clinic, in Ohio.

“This study has changed our clinical practice,” Dr. Turan said. Cleveland Clinic has eliminated IV acetaminophen from its formulary, he said.

Introduced in the United States in 2011, IV acetaminophen does not promote bleeding or delay bone healing and, although expensive, is used to complement or reduce the use of opioids as postoperative analgesics. However, its efficacy as an analgesic is unclear. Small studies have shown mixed results.

The FACTOR clinical trial is the largest randomized trial to examine the use of IV acetaminophen in patients undergoing abdominal surgery.

Between February 2015 and October 2018, 580 patients at two Cleveland Clinic institutions were randomized to receive IV acetaminophen at 1 g, or normal saline placebo starting at the beginning of surgery and repeated every six hours until 48 hours postoperatively or hospital discharge.

There was no significant reduction in the study’s primary outcome of median duration of hypoxemia (hemoglobin oxygen saturation of <90%) per hour: 0.7 minutes among patients in the acetaminophen group and 1.1 minutes among patients in the placebo group (P=0.29). Analysis revealed no significant difference in secondary outcomes, including nausea and vomiting, sedation, fatigue, active time and respiratory function.

Patients had a mean age of 49 years and 48% were women. All of them had an ASA physical status class of I to III, were scheduled for elective open or laparoscopic abdominal or pelvic surgery, and were expected to be hospitalized for at least two nights. They were randomized in a 1:1 ratio, and stratified based on long-term opioid use and trial site.

The study had several limitations. Enrollment was limited to two hospitals belonging to Cleveland Clinic; about 15% of patients in each group used current analgesics; and 10 patients had missing data due to unexpected technical problems. Only abdominal procedures were included because they typically require considerable opioid use.

Intravenous acetaminophen may be more effective for less painful procedures, the authors noted.

The study results should persuade clinicians to curtail their use of IV acetaminophen for surgical patients, said Elizabeth Wick, MD, a professor of surgery at the University of California, San Francisco School of Medicine. She added that evidence supports the use of nonopioid analgesia, particularly nonsteroidal anti-inflammatory drugs, for abdominal surgery patients as long as they do not have a contraindication.

“We need to hold ourselves accountable to practice evidence-based perioperative care, and if the data isn’t there to use IV acetaminophen, we shouldn’t use it,” Dr. Wick said.