We all know that remifentanil is an ultra–short-acting μ-opioid receptor agonist with an onset time of 30 to 60 seconds, that it has a short context-sensitive half-life (3.5 minutes), does not accumulate even when used for long periods, rapidly crosses the placenta, and is metabolized quickly by the fetus. Given all that, is remifentanil useful for patient-controlled intravenous analgesia (PCIA) during labor?
Dr. Tao Duan and colleagues from the Department of Anaesthesiology, Shanghai First Maternity and Infant Hospital, Tongji University School of Medicine, Shanghai, China, and The Fourth Clinical College of Nanjing Medical University, Nanjing, China, performed a meta-analysis of trials using PCIA remifentanil for labor pain relief. Their findings are published in this month’s edition of Anesthesia & Analgesia in the article titled “A Comparison of Remifentanil Parturient-Controlled Intravenous Analgesia with Epidural Analgesia: A Meta-Analysis of Randomized Controlled Trials.”
The authors found five randomized controlled trials that included almost 900 parturients, of which about half were randomized to receive intravenous remifentanil, the other half were given epidural analgesia with local anesthetic / opioid combinations. At 1 and 2 hours, there was a suggestion that epidural analgesia was superior to PCIA with remifentanil. However, because of wide confidence intervals the difference did not reach statistical significance.
There was no difference between the groups in terms of nausea, vomiting, or pruritus, although wide confidence intervals again made interpretation difficult. Umbilical artery pH tended to be higher in those who received remifentanil. They noted that no trial found a difference in Apgar scores at 1 and 5 minutes and neonatal outcomes, but the data were not suitable for inclusion in the meta-analysis. The authors noted that five trials was too small for definitive conclusions of the meta-analysis.
In another randomized but unblinded trial of 40 patients also summarized in this month’s Anesthesia & Analgesia and previously in Aa2day, remifentanil was less effective than epidural analgesia. Additionally, remifentanil increased the incidence of apnea, although oxygenation recorded via pulse oximetry was unaffected.
As Drs. David J. Birnbach, and J. Sudharma Ranasinghe, Department of Anesthesiology, Perioperative Medicine and Pain Management, and Departments of Obstetrics and Gynecology and Public Health Sciences, University of Miami Miller School of Medicine/Jackson Memorial Hospital, Miami, Florida, note in the accompanying editorial published in the current issue of Anesthesia & Analgesia titled “Is Remifentanil a Safe and Effective Alternative to Neuraxial Labor Analgesia? It All Depends:
“…potentially serious side effects, such as maternal oxygen desaturation, sedation, and reduced fetal heart rate beat-to-beat variability that may occur during extended periods of remifentanil analgesia, may ultimately limit the use of remifentanil in obstetrics…remifentanil via conventional PCIA cannot be considered an effective and safe analgesia method to be used routinely for labor analgesia or as an optimal replacement for neuraxial analgesia. Future development of new analgesic agents and improved methods of administration are essential. So what’s the bottom line? No Holy Grail at this time! Women who cannot receive neuraxial analgesia because of preexisting conditions or who have a preference for analgesic options other than neuraxial blockade have to make the best of an imperfect situation, at least for now.”