imageSan Francisco—Women who receive higher doses of oxytocin during labor require greater amounts of epidural analgesics, suggesting augmented labor is more painful, new research indicates.

Although previous studies support a correlation between augmented labor and pain using pain scores, the new study is the first to assess epidural consumption in this situation, said Andrew W. Geller, MD, an obstetric anesthesiologist at Cedars-Sinai Medical Center, in Los Angeles. Dr. Geller presented his team’s findings at the 2013 annual meeting of the American Society of Anesthesiologists (abstract 3140).

That higher oxytocin dosing results in increased pain during labor is important for two reasons, Dr. Geller said. Increasing cases of augmented labor will boost the use of anesthesia services for these women. And the need for more epidural pain medication may be perceived by the patient as a failed epidural, which could negatively affect patient satisfaction—and, as insurers increasingly turn to such ratings to determine payments, ultimately the hospital’s bottom line.

The use of oxytocin for induction or augmentation of labor is increasing, with the overall rate of induction more than doubling between 1990 and 2006, according to recent literature. The investigators aimed to compare administration of oxytocin before delivery as calculated by area under the curve (AUC) with epidural drug consumption, also calculated as AUC.

The retrospective review included 216 charts of first-time laboring women who received oxytocin for labor augmentation in 2008. The total AUC of oxytocin administered before delivery was calculated from the dosage rate and time interval of administration. The researchers also calculated an AUC for epidural medications from bolus and infusion dosing.

For this study, epidural analgesia consisted of a 0.2% ropivacaine infusion without narcotic in addition to boluses of ropivacaine, bupivacaine, lidocaine or chloroprocaine (with or without fentanyl). The researchers converted epidural boluses to ropivacaine-equivalent doses in milligrams by minimal local anesthetic concentration equivalency. To account for differences in the length of epidural use and to obtain an hourly ropivacaine equivalency rate, the epidural AUC was divided by the duration. The researchers compared oxytocin AUC in quartiles of exposure with the hourly ropivacaine-equivalent rate.

Increasing quartile oxytocin AUC was associated with increasing total (infusion and bolus) and bolus ropivacaine use in the augmented patients (P<0.0001). The increase in ropivacaine also was seen when the researchers compared mean hourly ropivacaine dosage with quartile oxytocin AUC (P=0.035).

Joy Hawkins, MD, professor of anesthesia and director of obstetric anesthesia at the University of Colorado School of Medicine, in Aurora, said she was not surprised by the results. “We know that needing higher doses of oxytocin and increased pain in labor are markers for dystocia,” Dr. Hawkins said. “And we know that the need for higher doses of epidural medications—more top-ups—is a marker for dystocia leading to cesarean delivery. So this study goes along with all those associations.”

Interestingly, the rate of cesarean delivery nearly doubled between oxytocin exposure quartile 1 (16%) and quartile 4 (30%), although the interquartile rates were not statistically significant, Dr. Geller said. He hypothesized that dysfunctional labor could be leading to cesarean delivery and therefore higher doses of oxytocin, or that higher doses lead to cesarean delivery. “It’s most likely the former, though,” he said.

Dr. Hawkins noted that higher rates of cesarean delivery would increase the use of anesthesia services.

Dr. Geller said he and his colleagues would like to compare epidural use and pain management requirements of women who do not receive oxytocin before delivery with those of patients who have augmented delivery.