Fentanyl 50 and 100 mcg is useful in accelerating the onset of labour analgesia without compromising safety, according to a study presented here at the 2015 Annual Meeting of the Canadian Anesthesiologists’ Society (CAS).
“We have been decreasing our concentrations of our local anaesthetics, and we find that one of the impacts of that is that our [obstetric] patients are not getting comfortable quickly,” said Don Nguyen, MD, University of Western Ontario, London, Ontario. “We wanted to find out if adding a bolus of fentanyl at the initiation of their labour epidural analgesia would speed the onset of our patients getting comfortable.”
The study enrolled 105 women with similar age, weight, height and ASA classification, and saw equal numbers of women receive 1 of 3 doses of epidural fentanyl (20, 50, or 100 mcg) in addition to 10 ml of 0.08% bupivacaine.
The investigators used the Maternal Numeric Rating Scale (NRS) pain scores, which were monitored for each contraction, until pain scores were ≤3 or for 30 minutes. Duration of analgesia, maternal adverse events, patient satisfaction, type of obstetric delivery, and fetal outcomes were also assessed.
Patients who received 50 and 100 mcg doses of fentanyl experienced more rapid pain relief, with NRS measuring ≤3, compared with patients who received the lowest dose of fentanyl.
Patients at the lowest dose of fentanyl had a greater incidence of failure to reach NRS of ≤3 within a half-hour compared with women who received either the 50 or 100 mcg doses.
There were no differences in side effects with the exception of fetal bradycardia in the 2 arms that received higher doses of fentanyl.
“We found bradycardia was higher in the 50 mcg and 100 mcg groups, but the increase did not result in any emergency caesarean sections,” said Dr. Nguyen.