Incidence and risk factors for chronic pain after caesarean section under spinal anaesthesia

A randomised controlled trial of parecoxib, celecoxib and paracetamol as adjuncts to patient-controlled epidural analgesia after caesarean delivery

The benefit of combining non-opioid analgesics with neuraxial opioids for analgesia after caesarean delivery has not been clearly established. Larger doses of paracetamol or cyclooxygenase-2 inhibitors have not been evaluated. A randomised, double blind, double-dummy, parallel group placebo-controlled clinical trial was conducted among women having elective caesarean delivery under spinal anaesthesia, followed by pethidine patient-controlled epidural analgesia. Patients received placebos (group C); intravenous parecoxib 40 mg then oral celecoxib 400 mg at 12 hours (group PC); intravenous paracetamol 2 g then oral 1 g six-hourly (group PA); or these regimens combined (group PCPA). The primary outcome was 24-hour postoperative patient-controlled epidural pethidine use and the main secondary outcome was postoperative pain. One hundred and thirty-eight women were recruited but 27 subsequently met exclusion criteria, leaving 111 who were randomised, allocated and analysed by intention-to-treat (n=23, 30, 32 and 26 in groups C, PC, PA and PCPA respectively). There were no differences between groups for pethidine consumption, based on either intention-to-treat (median 365, 365, 405 and 360 mg in groups C, PC, PA and PCPA respectively, P=0.84) or per protocol analysis (17 major violations). Dynamic pain scores did not differ between groups but requirement for, and dose of, supplementary oral tramadol was least in group PCPA (incidence 23% versus 48%, 70% and 58% in groups C, PC and PA respectively, P=0.004). The addition of regular paracetamol, cyclooxygenase-2 inhibitors or both to pethidine patient-controlled epidural post-caesarean analgesia did not provide a pethidine dose-sparing effect during the first 24 hours.

Chronic pain after caesarean delivery: an Australian cohort

We investigated the incidence of and risk factors for persistent pain after caesarean delivery. Over a 12-month period, women having caesarean delivery were recruited prospectively at an Australian tertiary referral centre. Demographic, anaesthetic and surgical data were collected and at 24 hour follow-up, women were assessed for immediate postoperative pain and preoperative expectations of pain. Long-term telephone follow-up was conducted at two and 12 months postoperatively. Complete data were obtained from 426 of 469 women initially recruited (90.6%). The incidence of persistent pain at the abdominal wound at two months was 14.6% (n=62) but subsequently reduced to 4.2% (n=18) at 12 months. At two months, 33 patients (7.8%) experienced constant or daily pain. At 12 months, five patients (1.1%) continued to have constant or daily pain which was mild. There was no apparent increase in incidence of persistent pain associated with general versus regional anaesthesia (relative risk [RR] 0.89, 95% confidence interval [CI] 0.49 to 1.6); emergency vs elective procedure (RR 0.65, 95% CI 0.39 to 1.07); higher acute pain scores (RR 1.1, 95% CI 0.69 to 1.75); or history of previous caesarean delivery (RR 0.81, 95% CI 0.50 to 1.33). Persistent pain, usually of a mild nature, is reported by some women two months after their caesarean delivery, but by 12 months less than 1% of women had pain requiring analgesia or affecting mood or sleep. All declined a pain clinic review. Clinicians and patients can be reassured that caesarean delivery is unlikely to lead to severe persistent pain in the long-term.

Regional anaesthesia to prevent chronic pain after surgery: a Cochrane systematic review and meta-analysis

BACKGROUND

Regional anaesthesia may reduce the risk of persistent (chronic) pain after surgery, a frequent and debilitating condition. We compared regional anaesthesia vs conventional analgesia for the prevention of persistent postoperative pain (PPP).

METHODS

We searched the Cochrane Central Register of Controlled Trials, PubMed, EMBASE, and CINAHL from their inception to May 2012, limiting the results to randomized, controlled, clinical trials (RCTs), supplemented by a hand search in conference proceedings. We included RCTs comparing regional vs conventional analgesia with a pain outcome at 6 or 12 months. The two authors independently assessed methodological quality and extracted data. We report odds ratios (ORs) with 95% confidence intervals (CIs) as our summary statistic based on random-effects models. We grouped studies according to surgical interventions.

RESULTS

We identified 23 RCTs. We pooled data from 250 participants in three trials after thoracotomy with outcomes at 6 months. Data favoured epidural anaesthesia for the prevention of PPP with an OR of 0.33 (95% CI 0.20-0.56). We pooled two studies investigating paravertebral block for breast cancer surgery; pooled data of 89 participants with outcomes ≈ 6 months favoured paravertebral block with an OR of 0.37 (95% CI 0.14-0.94). Adverse effects were reported sparsely.

CONCLUSIONS

Epidural anaesthesia and paravertebral block, respectively, may prevent PPP after thoracotomy and breast cancer surgery in about one out of every four to five patients treated. Small numbers, performance bias, attrition, and incomplete outcome data especially at 12 months weaken our conclusions.

Effect of transversus abdominis plane block with and without clonidine on post-cesarean delivery wound hyperalgesia and pain

BACKGROUND AND OBJECTIVES

The transversus abdominis plane (TAP) block is an established technique to manage post-cesarean delivery pain. Transversus abdominis plane blocks with a local anesthetic only offer no analgesic benefits compared with intrathecal morphine. Adjuvants to extend TAP block duration and possibly reduce wound hyperalgesia, known to be a risk factor for chronic pain, have not been studied. We hypothesized that a TAP block with clonidine will affect postsurgical wound hyperalgesia and improve pain outcomes.

METHODS

Ninety women were randomly assigned to receive 1 of 3 TAP blocks after cesarean delivery: saline (placebo), bupivacaine (BupTAP), or bupivacaine + clonidine (CloTAP). The primary outcome was wound hyperalgesia index at 48 hours. Secondary outcomes included pain scores, analgesic consumption, and pain descriptors up to 12 months.

RESULTS

Wound hyperalgesia index at 48 hours (median [25th-75th percentiles]) was 1.07 (0.48-3.26) in the placebo group, 1.27 (0.59-2.95) in the BupTAP group, and 0.74 (0.09-2.25) in the CloTAP group (P = 0.48). Morphine request in the postanesthesia care unit was significantly higher in the placebo group compared with the other TAP groups (P = 0.01). Postoperative pain scores and requests for breakthrough medication at 48 hours (30% in the placebo group, 24% in the BupTAP group, and 12% in the CloTAP group, P = 0.25) or chronic pain descriptors reported up to 12 months did not differ significantly among groups.

CONCLUSIONS

Adding clonidine to a TAP block with bupivacaine did not affect wound hyperalgesia index and it did not improve short-term or long-term pain scores in women undergoing elective cesarean delivery. Further studies are warranted to determine the benefits of antihyperalgesic adjuvants in TAP solutions for specific individuals at risk for chronic pain.

Local anaesthetics and regional anaesthesia for preventing chronic pain after surgery

BACKGROUND

Regional anaesthesia may reduce the rate of persistent (chronic) pain after surgery, a frequent and debilitating condition.

OBJECTIVES

To compare local anaesthetics and regional anaesthesia versus conventional analgesia for the prevention of persistent pain six or 12 months after surgery.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2012, Issue 4), PubMed (1966 to April 2012), EMBASE (1966 to May 2012) and CINAHL (1966 to May 2012) without any language restriction. We used a combination of free text search and controlled vocabulary search. The results were limited to randomized controlled clinical trials (RCTs). We conducted a handsearch in reference lists of included trials, review articles and conference abstracts.

SELECTION CRITERIA

We included RCTs comparing local anaesthetics or regional anaesthesia versus conventional analgesia with a pain outcome at six or 12 months after surgery.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed trial quality and extracted data, including information on adverse events. We contacted study authors for additional information. Results are presented as pooled odds ratios (OR) with 95% confidence intervals (CI), based on random-effects models (inverse variance method). We grouped studies according to surgical interventions. We employed the Chi(2) test and calculated the I(2) statistic to investigate study heterogeneity.

MAIN RESULTS

We identified 23 RCTs studying local anaesthetics or regional anaesthesia for the prevention of persistent (chronic) pain after surgery. Data from a total of 1090 patients with outcomes at six months and of 441 patients with outcomes at 12 months were presented. No study included children. We pooled data from 250 participants after thoracotomy, with outcomes at six months. Data favoured regional anaesthesia for the prevention of chronic pain at six months after thoracotomy with an OR of 0.33 (95% CI 0.20 to 0.56). We pooled two studies on paravertebral block for breast cancer surgery; the pooled data of 89 participants with outcomes at five to six months favoured paravertebral block with an OR of 0.37 (95% CI 0.14 to 0.94).The methodological quality of the included studies was intermediate. Adverse effects were not studied systematically and were reported sparsely. Clinical heterogeneity, attrition and sparse outcome data hampered the assessment of effects, especially at 12 months.

AUTHORS' CONCLUSIONS

Epidural anaesthesia may reduce the risk of developing chronic pain after thoracotomy in about one patient out of every four patients treated. Paravertebral block may reduce the risk of chronic pain after breast cancer surgery in about one out of every five women treated. Our conclusions are significantly weakened by performance bias, shortcomings in allocation concealment, considerable attrition and incomplete outcome data. We caution that our evidence synthesis is based on only a few, small studies. More studies with high methodological quality, addressing various types of surgery and different age groups, including children, are needed.

Abnormal endogenous pain modulation is a shared characteristic of many chronic pain conditions

The intensity of acute and chronic pain depends on interactions between peripheral impulse input and CNS pain mechanisms, including facilitation and inhibition. Whereas tonic pain inhibition is a characteristic of most pain-free individuals, pain facilitation can be detected in many chronic pain patients. The capability to inhibit pain is normally distributed along a wide continuum in the general population and can be used to predict chronic pain. Accumulating evidence suggests that endogenous pain inhibition depends on activation of the prefrontal cortex, periaqueductal gray and rostral ventral medulla. Quantitative sensory test paradigms have been designed to acquire detailed information regarding each individual's endogenous pain inhibition and facilitation. Such tests include: temporal summation of pain, which is mostly used to assess facilitatory pain modulation by measuring the change in pain perception during a series of identical nociceptive stimuli; and conditioned pain modulation, which tests pain inhibition by utilizing two simultaneously applied painful stimuli (the 'pain inhibits pain' paradigm). Considerable indirect evidence seems to indicate that not only increased pain facilitation but also ineffective pain inhibition represents a predisposition for chronic pain. This view is supported by the fact that many chronic pain syndromes (e.g., fibromyalgia, temporomandibular joint disorder, irritable bowel syndrome, headache and chronic fatigue syndrome) are associated with hypersensitivity to painful stimuli and reduced endogenous pain inhibition. However, future prospective studies will be necessary to provide definitive evidence for this relationship. Such research would not only provide important information about mechanisms relevant to chronic pain but would also permit identification of individuals at high risk for future chronic pain.

[Predictors of chronic pain following surgery. What do we know?]

Chronic postoperative pain is known to be a significant clinical and economic problem. The estimated mean incidence is high and varies between 10 and 50%, with variations mostly related to procedure-specific conditions. High-risk types of surgeries are e.g. thoracotomy, breast or inguinal hernia surgery and amputations. Although there is increasing knowledge about the incidence of chronic postoperative pain after certain types of surgical procedures, there are only limited data related to the mechanisms and pathophysiology leading to chronic pain after surgery. Neuropathic pain components have been discussed, especially following operations with a high incidence of nerve damage (for example axillary lymphadenectomy). Besides surgical factors it seems that there are a number of other factors which likely increase the risk of chronic postoperative pain. These predictors for the development of chronic postoperative pain are multiple and include individual genetic factors, age and sex of the individual patient, preoperative chronic pain, psychosocial factors, neurophysiological factors, intraoperative nerve and muscle damage, postoperative complications and acute pain in the early postoperative period. Quantitative sensory testing including tests of inhibitory circuits like DNIC might help to predict the risk of individual patients even before surgery has started. The perioperative identification of patients who are at high risk for developing chronic pain after surgery is therefore a major goal for the future. This may help to develop preventive treatment strategies and avoid treatments with side effects for patients who are not at risk for developing chronic pain after surgery. Due to a lack of appropriate data for sufficient preventive approaches an effective postoperative acute pain management and a nerve-conserving surgical technique are the major keys in the prophylaxis of chronic postoperative pain.

Prevalence and predictors of chronic pain after labor and delivery

PURPOSE OF REVIEW

Labor pain is a complex phenomenon with sensory, emotional, and perceptive components and can be regarded as one of the most serious kinds of pain. Different strategies to approach acute labor pain have been developed. Chronic pain after labor and delivery has not been studied so extensively. In this review recent findings about chronic pain after labor and delivery will be discussed.

RECENT FINDINGS

Prevalence rates of chronic pain after cesarean section are between 6 and 18% and after vaginal delivery they are between 4 and 10%. Predictors for chronic pain after cesarean section and delivery are previous chronic pain, general anesthesia and higher postdelivery pain. As labor pain is rated as one of the most serious kinds of acute pain one could make a prediction about chronic pain after labor and delivery. We speculate that effective treatment of this pain with epidural analgesia could prevent the development of chronic pain.

SUMMARY

Treatment of acute pain during labor and delivery is necessary to prevent chronic pain. Future studies should focus on the long-term effects of different analgesic regimens on the development of chronic pain after labor and delivery.