Predicting Acute Pain After Cesarean Delivery to Reduce Risk for Persistent Pain

In the United States, cesarean delivery (CD) is performed in approximately 32% of live births, for a total of 1.3 million procedures annually.¹ An estimated 1 in 5 women experience severe acute pain after a cesarean procedure, and up to 18% of women develop chronic pain.² Severe acute pain after CD has been found to predict the development of chronic pain, increase the risk for postpartum depression, and interfere with infant care and breastfeeding.^3,4

Such findings underscore the importance of providing sufficient pain management for these patients during the acute postoperative period. However, the blanket approach that is currently applied is not suitable for all women, given individual differences in pain perception and other factors that influence CD-related pain.³

“If we can identify those women with high pain needs before surgery, we might be able to treat them differently and hopefully improve the control of their pain, rather than using the same pain regimen for all patients,” Ashraf S Habib, MBBCh, MSc, MHSc, FRCA, chief of the division of Women’s Anesthesia, and professor of Anesthesiology and Obstetrics and Gynecology at Duke University Medical Center, told Clinical Pain Advisor.

To that end, he and a colleague conducted a review of studies investigating the effectiveness of available tools to predict severe pain and opioid use in the 48 hours following CD.⁵ The review included 13 studies involving a variety of testing modalities, including quantitative sensory testing (QST) using pressure, electric, or thermal stimulation.

Although studies using a mechanical stimulus (ie, pressure) to assess pain threshold and pain tolerance indicated correlations with certain measures of post-CD pain, these were inconsistent and their strength was weak to moderate. One study using electric QST found an inverse correlation between sensation threshold and levels of postoperative pain and with analgesic intake, with moderate to high strength of evidence. In a study that used thermal QST to determine pain thresholds, “pain and unpleasantness ratings in response to suprathreshold heat stimulus and thermal pain threshold were both significantly correlated (with similar strengths of correlation) with resting pain at 24 hours, evoked pain at 24 hours, and recovery room analgesic consumption,” the authors reported.⁵

Although these findings suggest the potential utility of QST in predicting post-CD acute pain, these techniques are not often practical in the clinical setting because of the time and special equipment required, as well as because of the discomfort these techniques can cause.

A 2015 study found a correlation between level of pain experienced during local anesthetic skin infiltration prior to the administration of spinal anesthesia and post-CD pain scores and analgesia requests.⁶ Pain scores during this procedure were found to predict severe acute postoperative pain (ie, with a score ≥70 on a 0 to 100 scale) with a sensitivity of 91.6% and a specificity of 93.3%, making this an ideal method to assess risk for CD-associated pain, and it is already part of the standard cesarean care.

Several studies have examined the use of various preoperative questionnaires to predict post-CD pain based on psychological factors:

• Preoperative scores assessed with the State-Trait Anxiety Inventory were found to correlate with post-CD analgesic consumption.⁷
• A moderate correlation was observed between preoperative scores evaluated with the Pain Catastrophizing Scale and pain ratings on day 1 and 2 after CD.⁸
• Patients with “poor sleep,” as indicated by a score >5 of 21 on the Pittsburgh Sleep Quality Index were shown to have higher pain scores at 24 hours post-CD compared with those who scored in the “good sleep” (≤5 of 21) category (odds ratio [OR], 2.64; P =.006).⁹
• Preoperative scores using the Hospital Anxiety and Depression Scale were shown to predict moderate to severe post-CD pain (OR, 1.60; 95% CI, 1.16-2.20; P =.001).¹⁰
• Patients’ responses to simple screening questions about anticipated pain ratings and medication needs after CD were moderately correlated with their post-CD pain scores (Spearman correlation coefficient, ρ = 0.41; P <.05).¹¹ Another study indicated that responses to such questions were correlated with opioid consumption and pain scores (r², 0.212 and r², 0.447, respectively).¹²

“Surprisingly, simply asking a woman’s expected postoperative pain and perceived analgesic needs on a 0 to 10 scale appear to be very useful to preoperatively determine her postoperative pain and analgesic usage after surgery,” said study co-author Brendan Carvalho, MBBCh, FRCA, MDCH, president of the Society for Obstetric Anesthesia and Perinatology, chief of the Division of Obstetric Anesthesia, and Professor in the Department of Anesthesiology, Perioperative and Pain Medicine at Stanford University School of Medicine in California.

It is important to incorporate these questions into the preoperative interview and “use this information to either anticipate higher postoperative pain and analgesic usage after surgery or adjust her postoperative analgesic protocol to mitigate the expected higher pain and opioid requirements,” he told Clinical Pain Advisor.

The questions used in his study were:

• How much pain do you expect to experience after your surgery on a pain scale of 0 to 10? (0 = no pain, 10 = worst pain imaginable)
• What do you expect your analgesic requirements will be after surgery? (0 = no analgesia, 10 = highest amount)
• At what point on a pain scale of 0 to 10 would you likely request postoperative pain relief? (0 = no pain, 10 = worst pain imaginable)

Overall, the results of the review suggest that, “the clinical utility of most of those tools might be limited by the time needed to perform those tests in a busy clinical environment, and by the inconsistent findings in different studies or the presence of only weak to moderate correlations with postoperative pain outcomes,” remarked Dr Habib. Further research in this area will “allow individualized management of pain and hopefully improved pain management for all patients, by identifying women who might need more or less pain medications before surgery and treating them according to their anticipated needs,” he added.

The tools that demonstrated the most promise were local anesthetic infiltration and simple screening questions. Additional studies are needed to confirm their correlation with postoperative pain outcomes, and to ‘’confirm that using those methods to predict pain, and treating patients according to the results of those predictive tests, will actually result in better pain control for all patients,” concluded the review authors.

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References

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