The impact of intravenous acetaminophen on pain after abdominal surgery: a meta-analysis

Pain after surgery is commonly controlled with opioid pain medications. A multi-modal pain strategy that involves acetaminophen may help minimize the negative consequences of opioids, such as ileus, respiratory depression, and addictive potential. There are limited data on the effectiveness of intravenous (IV) acetaminophen in comparison with other nonopioid pain medications.

Four databases were queried for the keywords "acetaminophen," "intravenous," and "postoperative". Prospective studies of adult patients receiving at least 24 h of IV acetaminophen after intraabdominal surgery were analyzed for 12- and 24-h pain scores and 24-h narcotic consumption. A random effects model was performed using mean differences and 95% confidence intervals to assess the effect of IV acetaminophen on outcomes. Heterogeneity was assessed using χ² and the I² statistics.

Seventeen articles were identified that complied with inclusion and exclusion criteria. There was no significant difference in 24-h pain scores between IV acetaminophen and any other comparator, or in secondary endpoints of 12-h pain scores and 24-h narcotic consumption. Subgroup analysis demonstrated significant benefit for IV acetaminophen in open surgeries for decreased 24-h narcotic consumption. When analyzing individual medications, non-steroidal anti-inflammatory drugs demonstrated the largest reduction in 24-h narcotic consumption. Data were of moderate quality and demonstrated significant heterogeneity between studies.

The lack of significant differences in primary endpoints may be explained by the heterogeneous, moderate-quality data. However, subgroup analyses suggested IV acetaminophen may be advantageous in open surgeries, and non-steroidal anti-inflammatory drugs may lower the 24-h narcotic requirement.