Preoperative scar hyperalgesia is associated with post-operative pain in women undergoing a repeat Caesarean delivery

Chronic pain and local pain in usually painless conditions including neuroma may be due to compressive proximal neural lesion

It has been unexplained why chronic pain does not invariably accompany chronic pain-prone disorders. This question-driven, hypothesis-based article suggests that the reason may be varying occurrence of concomitant peripheral compressive proximal neural lesion (cPNL), e.g., radiculopathy and entrapment plexopathies. Transition of acute to chronic pain may involve development or aggravation of cPNL. Nociceptive hypersensitivity induced and/or maintained by cPNL may be responsible for all types of general chronic pain as well as for pain in isolated tissue conditions that are usually painless, e.g., neuroma, scar, and Dupuytren's fibromatosis. Compressive PNL induces focal neuroinflammation, which can maintain dorsal root ganglion neuron (DRGn) hyperexcitability (i.e., peripheral sensitization) and thus fuel central sensitization (i.e., hyperexcitability of central nociceptive pathways) and a vicious cycle of chronic pain. DRGn hyperexcitability and cPNL may reciprocally maintain each other, because cPNL can result from reflexive myospasm-induced myofascial tension, muscle weakness, and consequent muscle imbalance- and/or pain-provoked compensatory overuse. Because of pain and motor fiber damage, cPNL can worsen the causative musculoskeletal dysfunction, which further accounts for the reciprocity between the latter two factors. Sensitization increases nerve vulnerability and thus catalyzes this cycle. Because of these mechanisms and relatively greater number of neurons involved, cPNL is more likely to maintain DRGn hyperexcitability in comparison to distal neural and non-neural lesions. Compressive PNL is associated with restricted neural mobility. Intermittent (dynamic) nature of cPNL may be essential in chronic pain, because healed (i.e., fibrotic) lesions are physiologically silent and, consequently, cannot provide nociceptive input. Not all patients may be equally susceptible to develop cPNL, because occurrence of cPNL may vary as vary patients' predisposition to musculoskeletal impairment. Sensitization is accompanied by pressure pain threshold decrease and consequent mechanical allodynia and hyperalgesia, which can cause unusual local pain via natural pressure exerted by space occupying lesions or by their examination. Worsening of local pain is similarly explainable. Neuroma pain may be due to cPNL-induced axonal mechanical sensitivity and hypersensitivity of the nociceptive nervi nervorum of the nerve trunk and its stump. Intermittence and symptomatic complexity of cPNL may be the cause of frequent misdiagnosis of chronic pain.

Analgesic outcomes of tramadol alone and in combination with Butorphanol or Flurbiprofen Axetil after cesarean section: a retrospective study with propensity score matching analysis

BACKGROUND

The Society for Obstetric Anesthesia and Perinatology recommends a multimodal analgesia regimen for cesarean delivery analgesia. This study aimed to compare the analgesic effects of tramadol alone and combined with butorphanol or flurbiprofen axetil after a cesarean section.

METHODS

We performed a retrospective analysis based on the electronic medical records of a teaching hospital in China from January 2018 to January 2020. We collected data on demographic characteristics, anesthesia, analgesia strategy, and pain intensity postoperatively during the first 48 hours. Inadequate postoperative analgesia during this period was defined as an NRS score ≥ 4. We also collected data regarding off-bed activity and intestinal function recovery. Participants were classified into three groups according to analgesia regimens. Groups T, TF, and TB received tramadol, a mixture of tramadol and flurbiprofen axetil, and a combination of tramadol and butorphanol, respectively. Analgesic outcomes were compared using propensity score matching analysis.

RESULTS

Data from 2323 cases of caesarean section were included in the analysis, and 521 pairs were matched in each group according to their propensity score. Compared with group T, The inadequate analgesia on pain at rest and pain at movement was lower in group TF (RR: 0.42, 95% CI: 0.36-0.49, P = 0.001 and RR: 0.58, 95% CI: 0.48-0.69, P < 0.001, respectively),and the incidence of inadequate control of pain at movement was higher in group TB (RR: 1.38, 95% CI: 1.22-1.55, P < 0.001). Additionally, the percentage of off-bed activity at 2 days postoperatively was higher in group TB than in groups TF and T (78.7% vs. 68.5 and 78.7% vs. 64.9%, respectively, P < 0.001). The incidence of intestinal function recovery 2 days after cesarean delivery in group TB was higher than that in group TF (73.3% vs. 66.2%, P = 0.013).

CONCLUSIONS

Combining tramadol and flurbiprofen axetil could enhance the analgesic effect and be safely used for analgesia after a cesarean section. However, combining tramadol and butorphanol may produce an antagonistic effect.

Assessment and determinants of acute post-caesarean section pain in a tertiary facility in Ghana

Introduction

Caesarean sections (CS) feature prominently in obstetric care and have impacted positively on maternal / neonatal outcomes globally including Ghana. However, in spite of documented increasing CS rates in the country, there are no studies assessing the adequacy of post-CS pain control. This study assessed the adequacy of post-CS pain management as well as factors influencing this outcome. Additionally, post-CS analgesia prescription and serving habits of doctors and nurses were also described to help fill existing knowledge gaps.

Methods

Pain scores of 400 randomly selected and consenting post-CS women at a tertiary facility in Ghana were assessed at 6–12 hours post-CS at rest and with movement and at 24–36 hours post-CS with movement using a validated visual analog scale (VAS) from February 1, 2015 to April 8, 2015. Participant characteristics including age, marital status and duration of CS were obtained using pretested questionnaires and patient records review. Descriptive statistics were presented as frequencies and proportions. Associations between background characteristics and the outcome variables of adequacy of pain control at 6–12 hours post-CS at rest and with movement and at 24–36 hours post-CS with movement were analysed using Chi-square and Fisher’s exact tests and logistic regression methods. Adequate pain control was defined as VAS scores ≤5.

Results

At 6–12 hours post-CS (at rest), equal proportions of participants had adequate and inadequate pain control (50.1% vrs 49.9%). Over the same time period but with movement, pain control was deemed inadequate in 93% of respondents (369/396). Women who had one previous surgery [OR 0.47 95%CI 0.27, 0.82; p = 0.008] and those whose CS lasted longer than 45 mins [OR 0.39 95% CI 0.24, 0.62; p<0.001] had lower odds of reporting adequate pain control. Women prescribed 12-hourly and 8-hourly doses of pethidine had only 23.5% (12/51) and 10.3% (3/29) served as prescribed respectively. At 24–36 hours post CS, adequate pain control was reported by 85.3% (326/382) of participants.

Conclusions

Pain management was deemed inadequate within the first 12 hours post-CS with potential implications for early mother-child interaction. Appreciable numbers of participants did not have their analgesics served as prescribed. Adjunct pain control measures should be explored and healthcare workers must be encouraged to pay more attention to patients’ pain relief needs.

In-Hospital Opioid Consumption After the Previous Cesarean Delivery Weakly Predicts Opioid Consumption After Index Delivery: A Retrospective Cohort Study

BACKGROUND

To predict opioid consumption and pain intensity after the index cesarean delivery, we tested a hypothesis that opioid consumption after the previous cesarean delivery of the same patient can predict the opioid consumption after the index cesarean delivery. We further tested a secondary hypothesis that the pain scores after the previous cesarean delivery can predict the pain scores after the index cesarean delivery.

METHODS

This is a retrospective cohort study of 470 women who underwent both previous and index cesarean deliveries at a single institution from January 2011 to June 2019. To predict the opioid consumption (primary outcome) and average pain scores (on 11-point numeric rating scale) after their index cesarean delivery, we used a linear regression model incorporating only the opioid consumption and average pain scores after the previous cesarean delivery, respectively (unadjusted models). Demographic and obstetric variables were then added as predictors (adjusted models). The bootstrap was used to compare these models with respect to proportion of variance of the outcome accounted for (R2).

RESULTS

Unadjusted models were weakly predictive of opioid consumption (R2 = 0.268; 95% confidence interval [CI], 0.146-0.368) and average pain scores (R2 = 0.176; 95% CI, 0.057-0.250). An adjusted model for opioid consumption was weakly predictive (R2 = 0.363; 95% CI, 0.208-0.478), but an adjusted model for average pain scores was not predictive of the outcomes (R2 = 0.070; 95% CI, -0.143 to 0.219). Adjusted models failed to explain variances of opioid consumption and average pain scores significantly better than unadjusted models (P = .099 and P = .141, respectively).

CONCLUSIONS

Opioid consumption and pain scores after women's previous cesarean delivery only explain 27% of variance of opioid consumption and 18% of variance of their pain after their index cesarean delivery. Therefore, previous cesarean delivery analgesic metrics are not robust enough to be used as clinically applicable predictors for index delivery.

Wound Infusion of 0.35% Levobupivacaine Reduces Mechanical Secondary Hyperalgesia and Opioid Consumption After Cesarean Delivery. A Prospective, Randomized, Triple-Blind, Placebo-Controlled Trial

BACKGROUND

Some patients still report moderate-to-severe postoperative pain after cesarean delivery. Local anesthetic wound infusion improves acute pain and might act on peripheral and central sensitization mechanisms; however, no studies have proved this hypothesis. We evaluated the potential benefits of continuous wound infusion of levobupivacaine after cesarean delivery on secondary hyperalgesia (primary end point) and primary hyperalgesia, pain relief, persistent pain, and inflammatory and metabolic stress response.

METHODS

Healthy women scheduled for elective cesarean delivery participated in this prospective, randomized, triple-blind, placebo-controlled trial (NCT01458431). All patients received spinal anesthesia with 0.5% hyperbaric bupivacaine with fentanyl and a multiholed wound catheter placed under the fascia. Women were randomized to receive continuous wound infusion (0.35% levobupivacaine 7 mL/h for 48 hours; group L) or an equal volume of saline (group S). Secondary hyperalgesia to punctate mechanical stimuli was evaluated using dynamic tests, and primary hyperalgesia was evaluated using an electronic von Frey anesthesiometer; both were assessed at 24, 48, and 72 hours. The following variables were collected: intensity of postoperative parietal and visceral pain at rest and on movement rated on a visual analog scale >72 hours, time to first bolus of patient-controlled analgesia (PCA), cumulative dose of rescue morphine (PCA) and acetaminophen, ability to sleep and sleep quality, and patient satisfaction. Persistent postoperative pain was evaluated during a telephone interview at 1, 3, 6, and 12 months after surgery. C-reactive protein, acid glycoprotein, preprandial glucose, insulin, cortisol, prolactin, growth hormone, and interleukin-6 were measured before cesarean delivery and at 8, 24, and 48 hours. Adverse events and patient outcomes were recorded.

RESULTS

Seventy women were included. In group L, the area of secondary hyperalgesia was significantly reduced (43.4 [18.5-80] vs 68.4 [39.0-136] cm2 and 45.1 [0.9-89.8] vs 67.3 [31.3-175] cm2 at 24 and 48 hours, respectively; group:time interaction P value < .001), the mechanical pain threshold was significantly higher at 24 hours (633 [441-802] vs 417 [300-572] g.mm-2; P = .001), and morphine consumption was significantly lower at 24 hours (4 [2-11] vs 11[6-23]; P = .003) compared with group S. Levobupivacaine had no effect on persistent postoperative pain at 1, 3, 6, and 12 months. Plasma insulin levels in the immediate postoperative period and at 8, 24, and 48 hours were significantly lower in group L (P < .001). There were no significant differences in other biochemical parameters of inflammatory and endocrine-metabolic response.

CONCLUSIONS

Levobupivacaine wound infusion provides adequate analgesia and might be an effective antihyperalgesic adjunct.

Description and Comparison of Acute Pain Characteristics After Laparoscope-Assisted Vaginal Hysterectomy, Laparoscopic Myomectomy and Laparoscopic Adnexectomy

Purpose

To determine the characteristics of the acute pain after laparoscopic-assisted vaginal hysterectomy (LAVH), laparoscopic myomectomy (LM), and laparoscopic adnexectomy (LA) and compare them with each other.

Patients and Methods

Patients undergoing LAVH, LM, and LA under general anaesthesia at the First Affiliated Hospital of Wenzhou Medical University between December 2017 and December 2019 were selected. Their data were collected before, during, and after the surgery. We evaluated the degrees of pain in each group of patients and compared them.

Results

There were differences in the baseline characteristics of the patients in the LAVH, LM, and LA groups. The severity and incidence of postoperative pain were higher in the LAVH group than in the LM and LA groups, followed by the LM and LA groups. Compared with the LA group, the postoperative pain in the LAVH and LM groups was more complicated. The LA group had the lowest incidence of two or more types of moderate to severe pain. The LAVH and LM groups mainly had visceral pain and low back pain, and the LA group mainly had incisional pain. Shoulder pain had the lowest incidence in the three groups.

Conclusion

There were different postoperative pain characteristics after the LAVH, LM, and LA, and we should clinically adjust analgesia programs for different gynaecological laparoscopic surgeries.

Prediction of Persistent Pain Severity and Impact 12 Months After Breast Surgery Using Comprehensive Preoperative Assessment of Biopsychosocial Pain Modulators

BACKGROUND

Persistent post-mastectomy pain (PPMP) is a significant negative outcome occurring after breast surgery, and understanding which individual women are most at risk is essential to targeting of preventive efforts. The biopsychosocial model of pain suggests that factors from many domains may importantly modulate pain processing and predict the progression to pain persistence.

METHODS

This prospective longitudinal observational cohort study used detailed and comprehensive psychosocial and psychophysical assessment to characterize individual pain-processing phenotypes in 259 women preoperatively. Pain severity and functional impact then were longitudinally assessed using both validated surgery-specific and general pain questionnaires to survey patients who underwent lumpectomy, mastectomy, or mastectomy with reconstruction in the first postsurgical year. An agnostic, multivariable modeling strategy identified consistent predictors of several pain outcomes at 12 months.

RESULTS

The preoperative characteristics most consistently associated with PPMP outcomes were preexisting surgical area pain, less education, increased somatization, and baseline sleep disturbance, with axillary dissection emerging as the only consistent surgical variable to predict worse pain. Greater pain catastrophizing, negative affect, younger age, higher body mass index (BMI), and chemotherapy also were independently predictive of pain impact, but not severity. Sensory disturbance in the surgical area was predicted by a slightly different subset of factors, including higher preoperative temporal summation of pain.

CONCLUSIONS

This comprehensive approach assessing consistent predictors of pain severity, functional impact, and sensory disturbance may inform personalized prevention of PPMP and also may allow stratification and enrichment in future preventive studies of women at higher risk of this outcome, including pharmacologic and behavioral interventions and regional anesthesia.

Opioid Use and Misuse in Pregnancy

The rate of pregnant women with an opioid use disorder has risen drastically in the past 20 years, paralleling that in the general population. Pregnancies associated with opioid use, abuse, or dependence have significantly higher rates of complications, such as neonatal opioid withdrawal syndrome, intrauterine growth restriction, neural tube defects, stillbirth, increased maternal mortality, greater postpartum pain, and longer inpatient stays. Patient education about the risks and benefits of multimodal analgesia and empowering shared decision making may help curb the opioid epidemic. Tailoring pain management to individual needs might be the solution to the problem.

Analgesic Effect Comparison Between Nalbuphine and Sufentanil for Patient-Controlled Intravenous Analgesia After Cesarean Section

Background: Efficient maternal pain relief after cesarean delivery remains challenging, but it is important to improve outcomes for the mother and the newborn during the puerperium. We compared the analgesic effect of nalbuphine (a κ receptor agonist/μ receptor antagonistic) with that of sufentanil (a µ-receptor agonist) in patient-controlled intravenous analgesia (PCIA) after cesarean section.

Methods: We enrolled 84 patients scheduled for elective cesarean sections with spinal anesthesia and randomized them into either nalbuphine or sufentanil groups (42 patients each). Pain scores, PCIA drug consumptions, degree of satisfaction, and adverse events were recorded as outcome measures.

Results: The pain scores at rest and uterine cramping pain scores in the nalbuphine group were lower than those in the sufentanil group at 6, 12, and 24 h after the operation. Also, the pain scores while switching to a seated position were lower in the nalbuphine group than in the sufentanil group at 6 and 12 h after the operation (p < 0.05). We found no significant differences in the PCIA drug consumption between the two groups. The degree of satisfaction in patients in the nalbuphine group was higher than that of patients in the sufentanil group (p = 0.01). Adverse events did not differ in the two groups.

Conclusion: PCIA with nalbuphine provides better analgesia and higher patient satisfaction than sufentanil after cesarean section.

The Impact of Music on Nociceptive Processing

OBJECTIVE

Music has been shown to modulate pain, although the impact of music on specific aspects of nociceptive processing is less well understood. Using quantitative sensory testing (QST), we assessed the impact of a novel music app on specific aspects of nociceptive processing.

DESIGN

Within-subjects paired comparison of pain processing in control vs music condition.

SETTING

Human psychophysical laboratory.

SUBJECTS

Sixty healthy adult volunteers.

METHODS

Subjects were assessed for baseline anxiety, depression, and catastrophizing using validated questionnaires. QSTs measured included 1) pain threshold and tolerance to deep muscle pressure, 2) pain with mechanical pinprick, 3) temporal summation of pain (TSP) with a repeated pain stimulus, and 4) conditioned pain modulation (CPM) with a second painful stimulus. QSTs were performed in the absence and presence of music delivered through a music app.

RESULTS

We found an increase in pressure pain thresholds in both the forearm (P = 0.007) and trapezius (P = 0.002) with music, as well as a decrease in the amount of pinprick pain (P < 0.001) and TSP (P = 0.01) with music. Interestingly, CPM was also significantly diminished (P < 0.001) in the music condition. No significant difference in cold pain, anxiety, or situational catastrophizing was observed with music. Higher baseline pain catastrophizing scores were associated with less music-induced pressure pain reduction.

CONCLUSIONS

Several measures of mechanical pain sensitivity were reduced with music. TSP, a measure of central sensitization, also decreased with music, but CPM, a measure of descending modulation of pain, was not further augmented by music.

The analgesic effect of tramadol combined with butorphanol on uterine cramping pain after repeat caesarean section: a randomized, controlled, double-blind study

PURPOSE

This study aimed to explore the effect of patient-controlled intravenous analgesia (PCIA) using tramadol combined with butorphanol on uterine cramping pain in women undergoing repeat caesarean section.

METHODS

A total of 126 patients, who were scheduled to undergo repeat caesarean section under spinal anesthesia, were included. PCIA using tramadol combined with butorphanol or sufentanil was randomly performed for postoperative pain control. Postoperative uterine cramping pain and wound pain within 48 h after surgery were evaluated. Postoperative analgesic consumption, early activity time, and length of hospital stay were also recorded and analyzed.

RESULTS

Uterine cramping pain intensity in women undergoing repeat caesarean section was significantly higher compared with their wound pain (P < 0.05). The mean visual analog scale (VAS) score for uterine cramping pain in the tramadol-butorphanol group was significantly lower than that in the sufentanil group at rest, and at 6 h and 12 h after surgery. VAS scores for uterine cramping pain during movement at 6 h, 12 h, and 24 h after surgery in the tramadol-butorphanol group were also significantly lower than that in sufentanil group (P < 0.05). There was no significant difference in VAS score for wound pain at the different time points between the tramadol-butorphanol and sufentanil groups (P > 0.05). Patient-controlled intravenous analgesia with tramadol accelerated early rehabilitation and decreased the length of hospital stay (P < 0.05).

CONCLUSION

PCIA using tramadol combined with butorphanol provided a better analgesic effect and accelerated postoperative rehabilitation compared with sufentanil, and may be an optimal analgesic strategy for women undergoing repeat caesarean section.

CLINICAL TRIAL REGISTRATION

The trial was registered at Chinese Clinical Trial Registry ( www.chictr.org.cn ) with ID: ChiCTR-1800014986.

Ropivacaine and Ketorolac Wound Infusion for Post-Cesarean Delivery Analgesia: A Randomized Controlled Trial

OBJECTIVE

To evaluate the efficacy of wound infusion with ropivacaine plus ketorolac compared with placebo for post-cesarean delivery analgesia in women who received a multimodal analgesic regimen including intrathecal morphine.

METHODS

In a randomized double-blind study, women undergoing scheduled cesarean delivery under spinal or combined spinal epidural anesthesia were randomized to wound infusion with ropivacaine 0.2% plus ketorolac, or saline placebo using an elastometric pump for 48 hours. The primary outcome was pain score with movement at 24 hours after surgery (0-10 scale, 0=no pain and 10=worst possible pain). Secondary outcomes included pain scores at rest at 24 hours, pain scores at rest and with movement at 2 and 48 hours, opioid consumption, and time to first rescue analgesic. A sample size of 35 per group (n=70) was planned.

RESULTS

From November 8, 2016, to May 17, 2019, 247 women were screened, and 71 completed the study per protocol: 38 in the placebo group and 33 in the ropivacaine plus ketorolac group. Patient demographics and intraoperative characteristics were comparable between the groups. There was no significant difference between the groups in the primary outcome of pain score with movement at 24 hours (difference in median score 0, 95% CI -1 to 2, P=.94). There were also no significant differences between the placebo and ropivacaine plus ketorolac groups in pain scores at other time points, in total opioid consumption (difference in median consumption -12.5 mg, 95% CI -30 to 5, P=.11), or in time to rescue analgesics (median [interquartile range] 660 [9-1,496] vs 954 [244-1,710] minutes, hazard ratio 0.69, 95% CI 0.41 to 1.17, P=.16).

CONCLUSION

There was no benefit of wound infusion with ropivacaine and ketorolac in women who received intrathecal morphine and a multimodal analgesic regimen.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, NCT02829944.

FUNDING SOURCE

The study was supported in part by Avanos Medical Inc.

Acute postoperative pain is correlated with the early onset of postpartum depression after cesarean section: a retrospective cohort study

The primary purpose of this study was to evaluate the correlation between the intensity of acute postoperative pain and development of postpartum depression (PPD) after cesarean section (CS). The secondary purpose was to investigate perioperative risk factors for PPD detected in the postoperative period after CS. We retrospectively reviewed 615 women who had undergone CS between January 2017 and October 2019 in our hospital. The incidence of PPD was 22.7% on postoperative day (POD) 5 in the 247 women whose numerical rating scale (NRS) scores on POD3 were available. The severity of acute postoperative pain evaluated by NRS was higher in women with than in those without PPD on POD3 (P < 0.02). The independent risk factors for the onset of PPD on POD5 were being a primipara [adjusted odds ratio (aOR), 2.08; 95% confidence interval (CI), 1.03-4.20, P < 0.05], preoperative presence of chronic pain (OR, 4.44; 95% CI 1.82-10.81, P < 0.001), and NRS ≥ 2 on POD3 (aOR, 4.90; 95% CI 1.06-22.61, P < 0.05). Our findings suggest that assessing both acute postoperative pain and presence of PPD can inform the introduction of interventions in the early phase to prevent development of PPD after CS.

Repeated Cesarean Delivery Predicted a Higher Risk of Inadequate Analgesia Than Primary Cesarean Delivery: A Retrospective Study with Propensity Score Match Analysis

Purpose

This study aimed to compare the analgesic outcomes between primary and repeated cesarean delivery.

Patients and Methods

We performed a retrospective analysis based on the medical records of a teaching hospital in China from January 2018 to March 2019. We collected data on demographic characteristics, perioperative complications, anesthesia, and surgical factors for cesarean delivery patients. We also recorded the postoperative analgesic strategy, pain intensity (assessed by the number rating scale) during the first 48 hrs after surgery, hospital cost, and hospital stay. Postoperative inadequate analgesia was defined by a score of ≥ 4 in the number rating scale. Analgesic outcomes after cesarean delivery between primiparas and multiparas were compared using propensity score matching analysis. Moreover, subgroup logistic analysis for different age groups (≥ 35 and < 35 years) was performed to investigate the effect of the maternal category on postoperative inadequate analgesia.

Results

A total of 1543 patients were included in the analysis and 571 pairs (1142 patients) were matched in the primiparas and multiparaparas group according to their propensity score. In both the non-matched and matched cohort, the incidence of inadequate analgesia in the primiparas group was lower than that in the multiparas group (16.7% vs. 24.0%, P < 0.001 and 16.1% vs. 23.5%, P = 0.002; respectively). The multiparas group was identified as being at risk of inadequate analgesia after cesarean delivery in both age groups (age ≥ 35 years, odds ratio: 2.18, 95% confidence interval: 1.20–3.95; age < 35 years, odds ratio: 1.43, 95% confidence interval 1.08–1.89).

Conclusion

Multiparas that undergo a repeat cesarean delivery had a significantly higher risk of inadequate postoperative pain treatment than primiparas. The maternal category should be considered when formulating the postoperative analgesia strategy after cesarean delivery.

The effect of gestational diabetes mellitus on sufentanil consumption after cesarean section: a prospective cohort study

Background

Previous studies have shown that patients with long-term diabetes require more opioids after surgery than patients without diabetes. Gestational diabetes mellitus (GDM) normally only lasts for a brief period; nevertheless, its effect on sufentanil consumption after cesarean section is unknown.

Methods

This prospective cohort study included two groups: a GDM group (n = 32) and a matched non-GDM (NGDM) group (n = 32). All patients underwent routine combined spinal-epidural anesthesia for cesarean delivery. Sufentanil consumption through an intravenous patient-controlled analgesia (PCA) pump, the frequency of PCA requests, and visual analog scale (VAS) scores 6 and 24 h after surgery were compared between groups.

Results

Sufentanil consumption (μg) 6 h after surgery was higher in the GDM group than in the NGDM group (24.0 ± 6.6 vs 20.1 ± 5.7, P = 0.023). PCA was used more frequently 6 and 24 h after surgery by the GDM group than by the NGDM group (1[0–2] vs 0[0–1], P = 0.001; 6 [1–5] vs 3 [1, 2, 6–8], P = 0.001, respectively). The VAS score during activity 24 h after surgery was higher in the GDM group than in the NGDM group (5 [2, 3] vs 5 [1, 2], respectively, P = 0.03).

Conclusion

Pregnant women with GDM require more opioids during the immediate postoperative period after cesarean section than those without GDM.

Clinical trials registration

No. ChiCTR1800016014, ChenYang, May 6th 2018.

Comparison of Postoperative Opioid Consumption and Pain Scores in Primary Versus Repeat Cesarean Delivery in Opioid Naïve Patients

Background: Cesarean deliveries represent a large percentage of deliveries worldwide. Patients undergoing repeat cesarean deliveries are known to have increased risks for surgical complications. However, little is known regarding potential differences in pain. We sought to compare postoperative opioid consumption and pain scores in opioid naïve patients undergoing primary versus repeat non-emergent cesarean delivery. Methods: This was a retrospective cohort study. Patient inclusion criteria included: having a non-emergent cesarean delivery, receiving a spinal procedure for surgical anesthesia without general anesthesia, and following the same postoperative pain management protocols. Exclusion criteria included: history of opioid tolerance, illicit drug use, or prior, non-obstetric, major abdominal surgery. The primary outcome marker was total morphine equivalents consumed 0–72 h post-procedure compared between the primary versus repeat cesarean delivery groups. Secondary outcome markers were opioid consumption and pain scores in 24-h period increments for the first 72 h postoperatively. Results: 1617 patients were screened. 217 primary and 377 repeat cesarean deliveries met criteria for comparison. Reduced opioid consumption was demonstrated for the total opioid consumption 0–72 h for the repeat cesarean delivery group (median = 35) compared to the primary cesarean delivery group (median = 58), p = 0.0005. When divided into 24-h periods, differences were demonstrated for the 24–48 and 48–72 h periods but not the 0–24 h period. Pain scores did not differ statistically. Conclusion: Opioid naïve obstetric patients who undergo non-emergent repeat cesarean delivery demonstrate lower opioid consumption in the postoperative period. Providers should be aware of this potential difference in order to better educate patients and provide adequate pain management. Highlights: The study reviewed differences in opioid consumption between primary and repeat cesarean deliveries. All patients received the same protocol for spinal dosage and pain management. Repeat cesarean deliveries were associated with lower opioid consumption.

Comparison of postoperative pain between patients who underwent primary and repeated cesarean section: a prospective cohort study

BACKGROUND

The differences in post-operative pain are unclear between the primiparas who underwent a primary cesarean section and multiparas who underwent their first repeat cesarean section. The study aimed to explore the possible differences in postoperative pain between primiparas and multiparas.

METHODS

A prospective cohort study was performed only including women who underwent cesarean deliveries under spinal anesthesia. Postoperative patient-controlled intravenous analgesia (PCIA) was administered to all subjects with 0.2 mg/kg hydromorphone and 4 mg/kg flurbiprofen; the pump was programmed as 2.0 mL/h background infusion with a loading dose of 1 mL and a lockout period of 15 min. Postoperative incision and visceral pain intensity were evaluated using the visual analogue scale, and inadequate analgesia was defined as a visual analogue scale score ≥ 40 during 48 h post-operation. Additionally, the patients' pain statuses in postoperative week 1 and week 4 were also assessed during follow-up via telephone.

RESULTS

From January to May 2017, a total of 168 patients (67 primiparas and 101 multiparas) were included. The relative risk for multiparas to experience inadequate analgesia on incision pain was 0.42 (95% CI: 0.25 to 0.74) compared to primiparas. In patients aged < 30 years, inadequate analgesia on visceral pain was higher in multiparas than in primiparas (RR, 3.56 [1.05 to 12.04], P = 0.025). There was no significant difference in the combined incidence of inadequate analgesia in both types of pain between the multiparas and primiparas (33.7% vs. 40.2%, P = 0.381). No difference was found in PCIA use between the two groups (111.1 ± 36.0 mL vs. 110.9 ± 37.3 mL, P = 0.979). In addition, a significantly higher incidence of pain was noted 4 weeks post-surgery in primiparas than that in multiparas (62.2% vs. 37.7%, P = 0.011).

CONCLUSION

Multiparas who underwent their first repeat cesarean section have a lower for inadequate analgesia on incision pain during the first 48 h after surgery than primiparas. Multiparas aged under 30 years may be more prone to experiencing postoperative inadequate analgesia on visceral pain.

TRAIL REGISTRATION

ClinicalTrial.gov: NCT03009955 , Date registered: December 30, 2016.

AAAPT Diagnostic Criteria for Acute Pain Following Breast Surgery

Acute pain after breast surgery decreases the quality of life of cancer survivors. Previous studies using a variety of definitions and methods report prevalence rates between 10% and 80%, which suggests the need for a comprehensive framework that can be used to guide assessment of acute pain and pain-related outcomes after breast surgery. A multidisciplinary task force with clinical and research expertise performed a focused review and synthesis and applied the 5 dimensional framework of the AAAPT (Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks [ACTTION], American Academy of Pain Medicine [AAPM], American Pain Society [APS] Pain Taxonomy) to acute pain after breast surgery. Application of the AAAPT taxonomy yielded the following: 1) Core Criteria: Location, timing, severity, and impact of breast surgery pain were defined; 2) Common Features: Character and expected trajectories were established in relevant surgical subgroups, and common pain assessment tools for acute breast surgery pain identified; 3) Modulating Factors: Biological, psychological, and social factors that modulate interindividual variability were delineated; 4) Impact/Functional Consequences: Domains of impact were outlined and defined; 5) Neurobiologic Mechanisms: Putative mechanisms were specified ranging from nerve injury, inflammation, peripheral and central sensitization, to affective and social processing of pain. PERSPECTIVE: The AAAPT provides a framework to define and guide improved assessment of acute pain after breast surgery, which will enhance generalizability of results across studies and facilitate meta-analyses and studies of interindividual variation, and underlying mechanism. It will allow researchers and clinicians to better compare between treatments, across institutions, and with other types of acute pain.

Predicting Severity of Acute Pain After Cesarean Delivery: A Narrative Review

Cesarean delivery is one of the most common surgical procedures in the United States, with over 1.3 million performed annually. One-fifth of women who undergo cesarean delivery will experience severe pain in the acute postoperative period, increasing their risk of developing chronic pain and postpartum depression, and negatively impacting breastfeeding and newborn care. A growing body of research has investigated tools to predict which patients will experience more severe pain and have increased analgesic consumption after cesarean delivery. These include quantitative sensory testing, assessment of wound hyperalgesia, response to local anesthetic infiltration, and preoperative psychometric evaluations such as validated psychological questionnaires and simple screening tools. For this review, we searched MEDLINE, the Cochrane database, and Google Scholar to identify articles that evaluated the utility of various tools to predict severe pain and/or opioid consumption in the first 48 hours after cesarean delivery. Thirteen articles were included in the final review: 5 utilizing quantitative sensory testing, including patient responses to pressure, electrical, and thermal stimuli; 1 utilizing hyperalgesia testing; 1 using response to local anesthetic wound infiltration; 4 utilizing preoperative psychometric evaluations including the State-Trait Anxiety Inventory, the Pain Catastrophizing Scale, the Pittsburgh Sleep Quality Index, the Hospital Anxiety and Depression Scale, and simple questionnaires; and 2 utilizing a combination of quantitative sensory tests and psychometric evaluations. A number of modalities demonstrated statistically significant correlations with pain outcomes after cesarean delivery, but most correlations were weak to modest, and many modalities might not be clinically feasible. Response to local anesthetic infiltration and a tool using 3 simple questions enquiring about anxiety and anticipated pain and analgesic needs show potential for clinical use, but further studies are needed to evaluate the utility of these predictive tests in clinical practice.

Pressure algometry for assessment of abdominal wall sensitivity in horses after ventral midline coeliotomy

OBJECTIVE

To assess the clinical course of abdominal wall sensitivity after ventral midline coeliotomy in horses by determining mechanical nociceptive thresholds (MNTs) during hospitalization, and to determine the inter-observer reliability of pressure algometry on the abdominal wall.

STUDY DESIGN

Observational, cohort study.

SAMPLE POPULATION

A total of 13 horses presenting with signs of abdominal pain/colic undergoing ventral midline coeliotomy and 10 healthy horses without an abdominal incision.

METHODS

Measurements were performed on days 1, 3, 5, 7 and 9 postoperatively using a pressure algometer. Measurement sites were marked left and right, abaxial to the abdominal incision. Cranial to the incision, two control points were marked. Measurements were made by one observer, blinded to the recorded MNT values. To determine inter-observer reliability, five horses (surgical group n = 2; nonsurgical group n = 3) were measured by two observers in a randomized order.

RESULTS

Mean MNT values on days 5 and 7 were 9.61 Ncm^-2 and 10.14 Ncm^-2 in the operated group (p = 0.009 ; p = 0.005) respectively versus 13.00 Ncm^-2 on day 1. Wound-associated points showed lower values than control points (p = 0.002). The nonsurgical group did not show a difference between control points and wound-associated points (p = 0.06). No significant differences were found between the surgical and the nonsurgical groups at the wound-associated points on any days measured. The inter-observer reliability was low (intraclass correlation coefficient of 0.26; Cronbach's alpha of 0.27).

CONCLUSION

Operated animals showed a reduction in MNT values on days 5 and 7 when compared with day 1 and lower values for the wound-associated points when compared with the control points. Inter-observer reliability was low. Pressure algometry could be a useful tool for assessing wound sensitivity after ventral midline coeliotomy in horses, which may improve pain management postoperatively.

Persistent pain after cesarean delivery

The incidence of persistent pain after cesarean deliveries (CD) varies but is much lower than after comparable surgeries. However, with over four million deliveries annually and a rising CD rate, even a low prevalence of persistent pain after CD impacts many otherwise healthy young women. Consideration of the pathophysiology of persistent pain after surgery and the risk factors predisposing women to persistent and chronic pain after CD provides insights into the prevention and treatment of persistent pain; and improves the quality of care and recovery after CD. The findings that the peripartum state and oxytocin confer protection against persistent pain may provide new and interesting perspectives for the prevention and treatment of chronic pain caused by trauma or surgery. Predictive tools available to identify and target patients at high risk of acute and chronic pain have mostly weak to modest predictive correlations and many are either not clinically feasible or too time-consuming to apply. Persistent pain has been linked to the severity of acute postoperative pain and opioid exposure. Modified surgical techniques, neuraxial anesthesia and opioid-sparing analgesia may help limit the development of persistent and chronic pain. The goal of this narrative review is to examine the incidence of persistent pain after CD; review briefly the underlying pathophysiology of persistent pain and the transition from acute to chronic pain (with particular emphasis on the uniqueness after CD); and to review modifiable risk factors and prevention strategies that identify at-risk patients and allow tailored treatment.

A novel approach to neuraxial anesthesia: application of an automated ultrasound spinal landmark identification

Background

Neuraxial procedures are commonly performed for therapeutic and diagnostic indications. Currently, they are typically performed via palpation-guided surface landmark. We devised a novel intelligent image processing system that identifies spinal landmarks using ultrasound images. Our primary aim was to evaluate the first attempt success rate of spinal anesthesia using landmarks obtained from the automated spinal landmark identification technique.

Methods

In this prospective cohort study, we recruited 100 patients who required spinal anesthesia for surgical procedures. The video from ultrasound scan image of the L3/4 interspinous space in the longitudinal view and the posterior complex in the transverse view were recorded. The demographic and clinical characteristics were collected and analyzed based on the success rates of the spinal insertion.

Results

Success rate (95%CI) for dural puncture at first attempt was 92.0% (85.0–95.9%). Median time to detection of posterior complex was 45.0 [IQR: 21.9, 77.3] secs. There is good correlation observed between the program-recorded depth and the clinician-measured depth to the posterior complex (r = 0.94).

Conclusions

The high success rate and short time taken to obtain the surface landmark with this novel automated ultrasound guided technique could be useful to clinicians to utilise ultrasound guided neuraxial techniques with confidence to identify the anatomical landmarks on the ultrasound scans. Future research would be to define the use in more complex patients during the administration of neuraxial blocks.

Trial registration

This study was retrospectively registered on clinicaltrials.gov registry (NCT03535155) on 24 May 2018.

Preoperative Serum Leptin Level Is Associated with Preoperative Pain Threshold and Postoperative Analgesic Consumption in Patients Undergoing Cesarean Section

OBJECTIVE

This study aimed to investigate the preoperative level of serum leptin in cesarean section (C-section) patients with and without acute labor pain and its association with postoperative analgesic consumption and preoperative pain threshold.

MATERIALS AND METHODS

Preoperative leptin levels, preoperative pain threshold, postoperative analgesic consumption in the first 24 h, and postoperative pain severity (visual analog scale (VAS) scores at 1, 2, 4, 6, 12, and 24 h postoperatively) in C-section patients with labor pain (emergency C-section; n = 21) and without labor pain (elective C-section; n = 25) were compared.

RESULTS

There were no significant differences between the groups regarding the demographic characteristics. Leptin levels, postoperative VAS scores, and analgesic consumption were significantly higher in the group with labor pain, while the preoperative pain threshold was lower. Serum leptin levels correlated negatively with pain threshold and positively with postoperative analgesic consumption. Multiple linear regression analyses in our study revealed that the preoperative leptin levels and having an emergency C-section independently affected the postoperative analgesic consumption and preoperative pain threshold, whereas their combined effects on these parameters were statistically not significant.

CONCLUSION

Preoperative levels of serum leptin were higher in C-section patients with labor pain than in those without labor pain, and increased serum leptin levels were associated with decreased preoperative pain threshold and increased postoperative analgesic consumption in our study population. Postoperative analgesic requirements may vary among patients, and their requirements might be predicted using preoperative indicators. Serum levels of leptin might be one such indicator and this warrants further studies with larger sample sizes.

Preoperative Psychosocial and Psychophysical Phenotypes as Predictors of Acute Pain Outcomes After Breast Surgery

The severity and impact of acute pain after breast surgery varies markedly among individuals, underlining the importance of comprehensively identifying specific risk factors, including psychosocial and psychophysical traits. In this prospective observational study, women (n = 234) undergoing breast-conserving surgery, mastectomy, or mastectomy with reconstruction completed a brief bedside quantitative sensory testing battery, along with measures of psychosocial characteristics. Postoperative pain severity, impact, and opioid use at 2 weeks were assessed using Brief Pain Inventory and procedure-specific breast cancer pain questionnaires. Moderate-severe average pain (>3/10) was reported by 29% of patients at 2 weeks. Regression analysis of pain outcomes revealed that pain severity was independently predicted by axillary dissection, pre-surgical pain, temporal summation of pain (TSP), (-)positive affect, and behavioral coping style. Pain impact was predicted by age, education, axillary dissection, reconstruction, but also by negative affect and depression scores. Lastly, opioid use was predicted by age, education, axillary dissection, reconstruction, TSP, and reinterpreting coping style. Our findings suggest that, individuals with certain phenotypic characteristics, including high TSP and negative affect, may be at greater risk of significant pain and continued opioid use at 2 weeks after surgery, independent of known surgical risk factors. PERSPECTIVE: We measured differences in the psychosocial and psychophysical processing of pain amongst patients before breast surgery using simple validated questionnaires and brief quantitative sensory testing. Independent of younger age and procedural extent (axillary surgery and reconstruction), affect and greater temporal summation of pain predicted acute postoperative pain and opioid use.

Patient-controlled oral analgesia versus nurse-controlled parenteral analgesia after caesarean section: a randomised controlled trial

We assessed the effectiveness of early patient-controlled oral analgesia compared with parenteral analgesia in a randomised controlled non-inferiority trial of women undergoing elective caesarean section under regional anaesthesia. Seventy-seven women received multimodal paracetamol, ketoprofen and morphine analgesia. The woman having patient-controlled oral analgesia were administered four pillboxes on the postnatal ward containing tablets and instructions for self-medication, the first at 7 h after the spinal injection and then three more at 12-hourly intervals. Pain at rest and on movement was evaluated using an 11-point verbal rating scale at 2 h and then at 6-hourly intervals for 48 h. The pre-defined non-inferiority limit for the difference in mean pain scores (patient-controlled oral analgesia minus parenteral) was one. The one-sided 95% CI of the difference in mean pain scores was significantly lower than one at all time-points at rest and on movement, demonstrating non-inferiority of patient-controlled oral analgesia. More women used morphine in the patient-controlled oral analgesia group (22 (58%)) than in the parenteral group (9 (23%); p = 0.002). The median (IQR [range]) number of morphine doses in the patient-controlled oral analgesia group was 2 (1-3 [1-7]) compared with 1 (1-1 [1-2]); p = 0.006) in the parenteral group. Minor drug errors or omissions were identified in five (13%) women receiving patient-controlled oral analgesia. Pruritus was more frequent in the patient-controlled oral analgesia group (14 (37%) vs 6 (15%) respectively; p = 0.03), but no differences were noted for other adverse events and maternal satisfaction. After elective caesarean section, early patient-controlled oral analgesia is non-inferior to standard parenteral analgesia for pain management, and can be one of the steps of an enhanced recovery process.

Endogenous opiates and behavior: 2014

This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants). This paper is the thirty-seventh consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2014 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (endogenous opioids and receptors), and the roles of these opioid peptides and receptors in pain and analgesia (pain and analgesia); stress and social status (human studies); tolerance and dependence (opioid mediation of other analgesic responses); learning and memory (stress and social status); eating and drinking (stress-induced analgesia); alcohol and drugs of abuse (emotional responses in opioid-mediated behaviors); sexual activity and hormones, pregnancy, development and endocrinology (opioid involvement in stress response regulation); mental illness and mood (tolerance and dependence); seizures and neurologic disorders (learning and memory); electrical-related activity and neurophysiology (opiates and conditioned place preferences (CPP)); general activity and locomotion (eating and drinking); gastrointestinal, renal and hepatic functions (alcohol and drugs of abuse); cardiovascular responses (opiates and ethanol); respiration and thermoregulation (opiates and THC); and immunological responses (opiates and stimulants).

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Spinal protein kinase Mζ contributes to the maintenance of peripheral inflammation-primed persistent nociceptive sensitization after plantar incision

BACKGROUND

Previous studies suggest that persistent post-surgical pain (PPSP) is correlated with preoperative pain status and amplification of central sensitization. Protein kinase Mζ (PKMζ) is an essential substrate of the late long-term potentiation underlying central sensitization, which is one mechanism of pain memory formation. However, the potential contributions of spinal PKMζ to PPSP, a condition in which preoperative pain is prevalent, are not known.

METHODS

Here, a modified 'hyperalgesia priming' model was established to simulate the clinical situation. This model used intraplantar injections of carrageenan (Car) as priming stimuli to elicit persistent nociceptive sensitization after plantar incision in rats. Upon treatment with PKMζ inhibitor ZIP, Scr-ZIP or protein kinase Cs (PKCs) inhibitor NPC-15437, altered behaviour and spinal PKMζ/PKCs expression were observed.

RESULTS

A long-lasting hypersensitivity induced by Car-priming was identified and precipitated by subsequent plantar incision in this 'two-hit' paradigm. Post-treatment with ZIP, but not Scr-ZIP and NPC-15437, after the resolution of Car-priming selectively relieved hypersensitivity. In contrast, pre-priming NPC-15437 treatment only prevented Car-induced initial transient hyperalgesia. Immunoassays showed a significant decrease in spinal PKMζ expression after plantar incision with post-priming ZIP treatment as compared with Scr-ZIP and NPC-15437, but no notable differences in PKCs expression were observed.

CONCLUSIONS

Spinal PKCs solely contribute to the initial induction of persistent pain, whereas PKMζ plays an essential role in spinal plasticity storage. PKMζ is responsible for the maintenance of peripheral inflammation-primed PPSP. Therefore, spinal PKMζ may be a therapeutic target to prevent surgery-induced chronic pain in patients with preoperative pain.