Surgical incisions for cesarean delivery vary in length: from nine to 23 cm, with a median of 15 cm, according to a recent study. Shorter incisions were associated with increased acute pain, and longer ones with acute and chronic pain. Severe pain was less likely to occur at medium lengths.
“To our knowledge, this Goldilocks effect—the principle that something must fall within a certain margin and extremes are to be avoided—of surgical incision length on pain outcomes has not been previously reported, and merits further investigation to unravel the effects of short-term tissue stretch and increased tissue trauma on acute and chronic post-cesarean pain,” said principal investigator Ruth Landau, MD.
“Identifying women at risk for severe pain after cesarean delivery is key to providing optimal pain relief,” said Dr. Landau, the associate director of obstetric anesthesia and the director of the Center for Precision Medicine in Anesthesiology at Columbia University Medical Center, in New York City.
Dr. Landau’s study included 690 women undergoing elective cesarean delivery: 100 at the University of Washington Medical Center, in Seattle, and 590 at Santa Joana Hospital, in Sao Paulo. Thirty-seven percent had a repeat cesarean delivery. The researchers evaluated the women preoperatively, with a follow-up of up to 12 months after delivery.
Among 76 women with longer incisions, which the researchers defined as being 17 cm or longer, approximately 19% reported persistent pain at eight weeks (P=0.0001), decreasing to 15% at six months (P=0.0001) and to 9% at 12 months (P=0.006).
Chronic pain, defined in the context of women having even some mild pain one year after delivery, was more common among the subset of women having a repeat cesarean delivery.
The reason that women with a shorter incision—defined here as less than 12 cm—experienced more significant acute pain is likely the stretching of the tissue during delivery, Dr. Landau said. This finding was not expected and has not been reported, she noted. On the other hand, incisions longer than 17 cm are more likely to cause peripheral nerve entrapment and neuromas. Excising a neuroma may eliminate the pain in women experiencing chronic neuropathic pain at the level of the scar, Dr. Landau said.
She said the range in incision length “may in part be due to the surgeons’ practice and the patient’s body characteristics.” Her observations suggest that determining incision length is more art than science. While observing a surgeon about to begin a cesarean delivery, she asked the obstetrician how long the incision would be. The obstetrician replied that the incision would be long enough to get the baby’s head out—“probably 12 cm or so.” The length, measured at the case’s finish: 15 cm.
Based on the current findings, the authors recommend that incisions be between 12 and 17 cm, regardless of the woman’s size. Within the cohort, not all obese women had long incisions, and not all long incisions occurred in obese women, Dr. Landau noted. However, among women who had had previous cesarean delivery, the preexisting scar predicted the current incision length. “Therefore, it is important for obstetricians to avoid unnecessarily lengthy incisions, as it may influence not only the level of pain in the current delivery but also in future ones,” she said.
“For management purposes, I am proposing to identify women who have risk factors for pain, and target enhanced therapies to these women,” Dr. Landau said. She estimated that roughly 15% to 20% would be at risk. Specifically, Dr. Landau suggested that because women with longer incisions are at risk not only for acute but also chronic pain, they should be given antineuropathic medications.
Other Risk Factors
In identifying predictors for postsurgical pain, individual, obstetric, surgical and postoperative factors are important to consider, Dr. Landau noted. Individual factors include a woman’s psychological profile, such as anxiety and catastrophization; prior pain such as back pain, migraines and menstrual pain; endogenous pain modulation; and genetic susceptibility. Obstetric factors that may influence pain levels include being in labor prior to cesarean delivery; having had a previous cesarean delivery; and an urgent cesarean delivery, particularly under general anesthesia, rather than with an epidural or spinal anesthetic, Dr. Landau said.
Previous efforts to prevent acute pain failed to provide evidence of efficacy of the relevant medications, probably because most women—those with incisions longer than 12 cm—aren’t at risk, Dr. Landau said in an interview. “Now that we’ve identified long incisions as risk factors, ketamine, clonidine and gabapentinoids, and all the antineuropathic medications can be used in such cases.”
Further analysis of this cohort, based on analysis of DNA samples Dr. Landau’s team drew, will include efforts to determine whether novel genetic variants that may be found among the outliers—for example, among women with no pain, or conversely, among those with significant severe pain absent of known risk factors—may shed light on observed variability in outcomes, regardless of incision length.
For future studies, “I want to evaluate the significance of surgery-related symptoms that are not pain, such as itching, tingling and numbness, that a significant number of women reported up to 12 months after delivery, to see whether these symptoms may be signals of abnormal healing that may be used as predictors of pain in subsequent cesarean deliveries,” Dr. Landau said.
Jill M. Mhyre, MD, an assistant professor of anesthesiology at the University of Arkansas for Medical Sciences, in Little Rock, said further studies should also consider “neonatal size, because the size of the neonate determines whether delivery will be successful through a very small incision.” Dr. Mhyre was not involved in the research.
About one-third of American women give birth via cesarean delivery. At 1.3 million annually, cesarean delivery is the most common inpatient surgical procedure in the United States.
The study results were presented at the 2017 annual meeting of the American Society of Anesthesiologists (abstract BOC08).
—David C. Holzman