Capsaicin-induced pain and sensitisation in the postpartum period

The association between adverse childhood experiences and peripartal pain experience

ABSTRACT

Adverse childhood experiences (ACEs) are associated with altered ongoing and evoked pain experiences, which have scarcely been studied for the peripartum period. We aimed to investigate how ACEs affect pain experience in pregnancy and labor. For this noninterventional trial with a short-term follow-up, pregnant women were divided into a trauma group (TG) with ACEs (n = 84) and a control group (CG) without ACEs (n = 107) according to the Childhood Trauma Questionnaire. Pain experience in pregnancy and labor was recorded by self-report and the German Pain Perception Scale. Pain sensitivity prepartum and postpartum was assessed by Quantitative Sensory Testing and a paradigm of conditioned pain modulation (CPM), using pressure pain thresholds (PPTs) and a cold pressor test. The TG showed higher affective and sensory scores for back pain and a more than doubled prevalence of preexisting back pain. Pelvic pain differences were nonsignificant. The TG also exhibited increased affective scores (1.71 ± 0.15 vs 1.33 ± 0.11), but not sensory scores for labor pain during spontaneous delivery. There were no group differences in prepartum pain sensitivity. While PPTs increased through delivery in the CG (clinical CPM), and this PPT change was positively correlated with the experimental CPM (r = 0.55), this was not the case in the TG. The association of ACEs with increased peripartal pain affect and heightened risk for preexisting back pain suggest that such women deserve special care. The dissociation of impaired clinical CPM in women with ACEs and normal prepartum experimental CPM implies at least partly different mechanisms of these 2 manifestations of endogenous pain controls.

Analgesia during Parturition in Domestic Animals: Perspectives and Controversies on Its Use

This article analyzes the physiological role of pain during parturition in domestic animals, discusses the controversies surrounding the use of opioids, non-steroidal anti-inflammatory drugs (NSAIDs), and local analgesics as treatments during labor, and presents the advantages and disadvantages for mother and offspring. Labor is a potentially stressful and painful event, due to the contractions that promote expulsion of the fetus. During labor, neurotransmitters such as the prostaglandins contribute to the sensitization of oxytocin receptors in the myometrium and the activation of nociceptive fibers, thus supporting the physiological role of pain. Endogenously, the body secretes opioid peptides that modulate harmful stimuli and, at the same time, can inhibit oxytocin's action in the myometrium. Treating pain during the different stages of parturition is an option that can help prevent such consequences as tachycardia, changes in breathing patterns, and respiratory acidosis, all of which can harm the wellbeing of offspring. However, studies have found that some analgesics can promote myometrial contractility, increase expulsion time, affect fetal circulation, and alter mother-offspring recognition due to hypnotic effects. Other data, however, indicate that reducing the number of uterine contractions with analgesics increases their potency, thus improving maternal performance. Managing pain during labor requires understanding the tocolytic properties of analgesics and their advantages in preventing the consequences of pain.

Mechanisms Underlying Lumbopelvic Pain During Pregnancy: A Proposed Model

Up to 86% of pregnant women will have lumbopelvic pain during the 3rd trimester of pregnancy and women with lumbopelvic pain experience lower health-related quality of life during pregnancy than women without lumbopelvic pain. Several risk factors for pregnancy-related lumbopelvic pain have been identified and include history of low back pain, previous trauma to the back or pelvis and previous pregnancy-related pelvic girdle pain. During pregnancy, women go through several hormonal and biomechanical changes as well as neuromuscular adaptations which could explain the development of lumbopelvic pain, but this remains unclear. The aim of this article is to review the potential pregnancy-related changes and adaptations (hormonal, biomechanical and neuromuscular) that may play a role in the development of lumbopelvic pain during pregnancy. This narrative review presents different mechanisms that may explain the development of lumbopelvic pain in pregnant women. A hypotheses-driven model on how these various physiological changes potentially interact in the development of lumbopelvic pain in pregnant women is also presented. Pregnancy-related hormonal changes, characterized by an increase in relaxin, estrogen and progesterone levels, are potentially linked to ligament hyperlaxity and joint instability, thus contributing to lumbopelvic pain. In addition, biomechanical changes induced by the growing fetus, can modify posture, load sharing and mechanical stress in the lumbar and pelvic structures. Finally, neuromuscular adaptations during pregnancy include an increase in the activation of lumbopelvic muscles and a decrease in endurance of the pelvic floor muscles. Whether or not a causal link between these changes and lumbopelvic pain exists remains to be determined. This model provides a better understanding of the mechanisms behind the development of lumbopelvic pain during pregnancy to guide future research. It should allow clinicians and researchers to consider the multifactorial nature of lumbopelvic pain while taking into account the various changes and adaptations during pregnancy.

Association of Postpartum Pain Sensitivity and Postpartum Depression: A Prospective Observational Study

INTRODUCTION

Postpartum depression (PPD) is a severe psychiatric disorder that negatively affects postnatal mothers worldwide. The aim of the study is to investigate the association between postpartum pain sensitivity and PPD as well as to identify the other potential risk factors for PPD and their interconnections.

METHODS

The current study was a prospective observational clinical study that enrolled 210 singleton pregnant women in a tertiary referral hospital from January to December 2020. Postpartum pain sensitivity was assessed by the Mandarin Chinese version of the Pain Sensitivity Questionnaire (PSQ), and PSQ-C-total and PSQ-C-minor scores were collected. PPD was screened by self-reporting Edinburgh Postnatal Depression Scale (EPDS), and EPDS total score was recorded. The association between postpartum pain sensitivity and PPD, as well as the risk factors and their interconnections, was analyzed by using a combination of stratified, bivariate, correlation, receiver-operating characteristic (ROC) curve, multivariate logistic regression, and path analysis.

RESULTS

Overall, 87 of 210 mothers (41.4%) screened positive for PPD. A positive correlation between PSQ-C-total (r = 0.67) or PSQ-C-minor (r = 0.62) and EPDS scores was identified. PSQ-C-total [area under curve (AUC) 0.89, 95% CI 0.84-0.93; P < 0.0001] showed significantly higher diagnostic accuracy compared with PSQ-C-minor (AUC 0.85, 95% CI 0.80-0.90; P < 0.0001) in predicting EPDS scores ≥ 10 points. Multivariate logistic regression indicated that a high PSQ-C-total score [adjusted odds ratio (OR) 1.12, 95% CI 1.08-1.51; P < 0.001] and gestational diabetes (adjusted OR 2.68, 95% CI 0.96-7.47; P = 0.045) were independent risk factors, while breastfeeding (adjusted OR: 0.34, 95% CI 0.15-0.78; P = 0.007) and normal birth weight (adjusted OR 0.17, 95% CI 0.05-0.61; P = 0.0047) were independently associated with decreasing adjusted ORs for EPDS scores ≥ 10 points. The path analysis model indicated that PSQ-C-total scores and gestational diabetes showed bidirectional effects, while birth weight and breastfeeding only had a direct impact on EPDS scores ≥ 10 points.

CONCLUSION

Increased postpartum pain sensitivity was closely associated with EPDS scores ≥ 10 points, and PSQ-C scores could be a reliable predictor. Moreover, gestational diabetes, low occurrence of breastfeeding, and low birth weight were the risk factors for EPDS scores ≥ 10 points.

TRIAL REGISTRATION

ChiCTR.org.cn identifier, ChiCTR-2000033091.

Effects of Spicy Stimulation and Spicy-Food Consumption on Human Pain Sensitivity: A Healthy Volunteer Study

Spicy-food intake has been shown to affect various human physiological systems and diseases. This study tested the analgesia effect caused by stimulation of a spicy sensation (spicy stimulation) and explored the effect of spicy-food consumption on human basal pain sensitivity. A total of 60 healthy undergraduates were included in the primary study. Placebo and sweet stimulation were used as reference interventions. Pressure and cold-pain thresholds were measured before and after taste stimulation. The frequency of spicy-food intake was also evaluated. An additional 100 subjects were recruited to validate the results. Compared to placebo stimulation, both pressure and cold-pain thresholds increased during spicy stimulation (P < .05). The increased thresholds remained, even when the taste stimulation residue was nearly eliminated (P < .05). The pressure (10.0 [2.1] vs 12.7 [3.0] kg/cm2, P < .001) and cold-pain (4.4 [1.6] vs 6.2 [2.7] seconds, P = .003) thresholds in subjects who consume spicy food ≥3 days/week were significantly lower than in those who consume it <3 days/week. In the validation population, the frequency of spicy-food intake was negatively associated with subjects' pressure (β = -.218, P = .013) and cold-pain (β = -.205, P = .035) thresholds. Spicy stimulation has an analgesia effect on adults that persists even after the taste stimulation stops. Conversely, a long-term spicy diet can reduce the human basal pain threshold. TRIAL REGISTRATION: The study protocol was approved by the Medical Ethics Committee of the Second Affiliated Hospital of Army Medical University, People's Liberation Army (identification No., 2017-023-01), and it was registered on the Chinese Clinical Trial Registry at www.chictr.org.cn (No. ChiCTR1800015053). PERSPECTIVE: This study directly examined the effects of stimulation of a spicy sensation on adult pain sensitivity and was the first to explore the relationship between long-term spicy-food intake and human pain sensitivity. The results provide evidence for future clinical pain intervention and individualized pain treatment.