Sensory-affective relationships among different types of clinical and experimental pain

Different types of pain patients used visual analogue scales (VAS) to rate their level of pain sensation intensity (VAS sensory) and degree of unpleasantness (VAS affective) associated with pain experienced at its maximum, usual, and minimum intensity. Women used the same VAS to rate their labor pain during early, active, and transition phases of stage I and in pushing (stage II). Consistent with the hypothesis that the affective dimension of clinical pain can be selectively augmented by perceived degree of threat to health or life, cancer pain patients and chronic pain patients gave higher VAS affective ratings as compared to VAS sensory ratings of their clinical pain, whereas labor patients and patients exposed to experimental pain gave lower VAS affective ratings compared to their VAS sensory ratings of pain. Affective VAS but not sensory VAS ratings of pain were considerably reduced when women in labor focused on the birth of the child as compared to when they focused on their pain. The results underscore the importance of utilizing separate measures of the sensory intensity versus the affective dimension of clinical pain and provide evidence that the affective dimension of different types of clinical pain is powerfully and differentially influenced by psychological contextual factors.     

骨科慢性疼痛患者疼痛灾难化与疼痛强度、情绪状态的关系

目的 了解骨科慢性疼痛患者疼痛灾难化现状,探索疼痛强度、情绪状态与疼痛灾难化的关系。方法 采用方便抽样的方法选择某三甲医院骨科慢性疼痛患者262例作为研究对象,采用一般资料调查表、疼痛数字评分表(number rating scale,NRS)、疼痛灾难化量表(pain catastrophizing scale,PCS)、正性负性情绪量表(positive and negative affect schedule,PANAS)对其进行调查。结果 骨科慢性疼痛患者NRS、PANAS和PCS评分分别为(6.59±2.31)、(64.94±11.45)和(34.51±9.63)分。不同居住方式、是否有配偶的患者间PCS得分比较,差异均有统计学意义(t=2.021,P=0.042; t=2.724,P=0.012),PCS和NRS、PANAS-PA、PANAS-NA间的相关系数(r)分别为0.397、-0.325和0.388(均P<0.01),多元线性回归结果显示疼痛强度和情绪状态对疼痛灾难化具有预测作用。结论 骨科慢性疼痛患者疼痛强度、情绪状态和疼痛灾难化呈中等程度相关,疼痛干预、增强社会支持和负性情绪与积极心理干预是减低疼痛灾难化的可能措施。     

Effects of extraversion and neuroticism on experimental pain, clinical pain, and illness behavior

The effects of 2 personality traits, extraversion and neuroticism, on experimental and clinical pain were characterized in a group of myofascial pain dysfunction (MPD) patients. Extraverts did not differ from introverts in visual analogue scale (VAS) sensory or VAS affective ratings of graded 5-sec nociceptive temperature stimuli (43-51 degrees C) nor in VAS sensory-VAS affective relationships related to their clinical pain. However, high extravert patients scored lower on affective inhibition (Pilowsky Illness Behavior Questionnaire; IBQ) compared to low extravert patients. This result is consistent with previous suggestions that extraverts inhibit overt expressions of suffering less than do introverts. High neurotic patients did not differ from low neurotic patients in their VAS sensory ratings of either experimental or clinical pain. Their VAS affective ratings of both types of pain were marginally higher as compared to low neurotic patients. As hypothesized, high neurotic score patients gave higher VAS ratings of emotions related to suffering and scored higher on items related to affective disturbance on the IBQ as compared to low neurotic score patients. Overall, the results indicate that the personality traits of neither extraversion nor neuroticism affect sensory mechanisms of nociceptive processing but appear to exert their influence by means of cognitive processes related to the ways in which people constitute the meanings and implications of pain.     

Health related quality of life and quantitative pain measurement in females with chronic non-malignant pain.

The aim of the present study was to assess, compare, and correlate the pain response to an experimental pain stimulus (hyperalgesia to pressure pain threshold (PPT) measured from different body sites), the pain intensity (VAS) of the habitual pain, and quality of life parameters (SF-36) in groups of females with chronic non-malignant pain syndromes. Forty female pain patients with fibromyalgia/whiplash (n = 10), endometriosis (n = 10), low back pain (n = 10), or rheumatoid arthritis (n = 10), as well as 41 age-matched healthy female controls participated in the study. The fibromyalgia/whiplash patients scored significantly higher (p < 0.04) VAS ratings (median rating = 7.0) than the endometriosis (6.0), low back pain (6.0), and rheumatoid arthritis (3.5) patients. All fours patient groups had significantly lower PPTs at all sites as compared with controls. The fibromyalgia/whiplash patients experienced the highest influence of pain on their overall health status, particularly vitality, social function, emotional problems, and mental health. A significant negative correlation was found between VAS rating and quality of life (p < 0.04). Significant correlation (p < 0.05) was found between pressure hyperalgesia measured at lowest PPT sites and the impairment of SF-36 physical function as well as mental health parameters. This study demonstrates significant generalised pressure hyperalgesia in four groups of chronic pain patients, correlations between degree of pressure hyperalgesia and impairment of some quality of life parameters, and increased pain intensity of the ongoing pain is associated with decreased quality of life.     

Three new datasets supporting use of the Numerical Rating Scale (NRS-11) for children’s self-reports of pain intensity

Despite wide usage of the Numerical Rating Scale (NRS) for self-report of pain intensity in clinical practice with children and adolescents, validation data are lacking. We present here three datasets from studies in which the NRS was used together with another self-report scale. Study A compared post-operative pain ratings on the NRS with scores on the Faces Pain Scale-Revised (FPS-R) in 69 children age 7–17 years who had undergone a variety of surgical procedures. Study B compared post-operative pain ratings on the NRS with scores on the Visual Analogue Scale (VAS) in 29 children age 9–17 years who had undergone pectus excavatum repair. Study C compared ratings of remembered immunization pain in 236 children who comprised an NRS group and a sex- and age-matched VAS group. Correlations of the NRS with the FPS-R and VAS were r = 0.87 and 0.89 in Studies A and B, respectively. In Study C, the distributions of scores on the NRS and VAS were very similar except that scores closest to the no pain anchor were more likely to be selected on the VAS than the NRS. The NRS can be considered functionally equivalent to the VAS and FPS-R except for very mild pain (<1/10). We conclude that use of the NRS is tentatively supported for clinical practice with children of 8 years and older, and we recommend further research on the lower age limit and on standardized age-appropriate anchors and instructions for this scale.     

老年人疼痛强度评估量表的选择

目的:调查老年人使用4种常用疼痛强度评估量表的情况,为选择合适的老年疼痛评估工具提供依据.方法:广州市两家老人院的61例65岁以上老年人参加了研究.用随机顺序排列的直观模拟量表(VAS)、数字评定量表(NRS)、词语描述量表(VDS)和修订版面部表情疼痛量表(FPS-R),对老年人的回忆性疼痛进行评估.结果:受试对象中男性17例,女性44例,平均年龄81.7岁,54例(88.5%) 认知正常,7例(11.5%)有一定程度的认知受损.4种量表疼痛评分间的Spearman相关系数为0.84～0.94.老年人能够用至少一种量表来主诉疼痛强度.FPS-R是错误率最低而首选率最高的量表.结论:4种量表均可用于评估老年人的疼痛,但FPS-R是最佳量表.将FPS-R、VDS和NRS 3种量表合并,制成简易疼痛评估尺,适合老年人认知功能且实用的疼痛评估方法.     

The validation of visual analogue scales as ratio scale measures for chronic and experimental pain

Visual analogue scales (VAS) of sensory intensity and affective magnitude were validated as ratio scale measures for both chronic and experimental pain. Chronic pain patients and healthy volunteers made VAS sensory and affective responses to 6 noxious thermal stimuli (43, 45, 47, 48, 49 and 51 degrees C) applied for 5 sec to the forearm by a contact thermode. Sensory VAS and affective VAS responses to these temperatures yielded power functions with exponents 2.1 and 3.8, respectively; these functions were similar for pain patients and for volunteers. The power functions were predictive of estimated ratios of sensation or affect produced by pairs of standard temperatures (e.g. 47 and 49 degrees C), thereby providing direct evidence for ratio scaling properties of VAS. Vas sensory intensity responses to experimental pain, VAS sensory intensity responses to different levels of chronic pain, and direct temperature (experimental pain) matches to 3 levels of chronic pain were all internally consistent, thereby demonstrating the valid use of VAS for the measurement of and comparison between chronic pain and experimental heat pain.     

Validity of four pain intensity rating scales

The Visual Analogue Scale (VAS), Numerical Rating Scale (NRS), Verbal Rating Scale (VRS), and the Faces Pain Scale-Revised (FPS-R) are among the most commonly used measures of pain intensity in clinical and research settings. Although evidence supports their validity as measures of pain intensity, few studies have compared them with respect to the critical validity criteria of responsivity, and no experiment has directly compared all 4 measures in the same study. The current study compared the relative validity of VAS, NRS, VRS, and FPS-R for detecting differences in painful stimulus intensity and differences between men and women in response to experimentally induced pain. One hundred twenty-seven subjects underwent four 20-second cold pressor trials with temperature order counterbalanced across 1°C, 3°C, 5°C, and 7°C and rated pain intensity using all 4 scales. Results showed statistically significant differences in pain intensity between temperatures for each scale, with lower temperatures resulting in higher pain intensity. The order of responsivity was as follows: NRS, VAS, VRS, and FPS-R. However, there were relatively small differences in the responsivity between scales. A statistically significant sex main effect was also found for the NRS, VRS, and FPS-R. The findings are consistent with previous studies supporting the validity of each scale. The most support emerged for the NRS as being both (1) most responsive and (2) able to detect sex differences in pain intensity. The results also provide support for the validity of the scales for use in Portuguese samples.     

Electrical low‐frequency stimulation induces long‐term depression of sensory and affective components of pain in healthy man

Electrical low‐frequency stimulation (LFS) of nociceptive skin afferents reliably induces long‐term depression (LTD) of pain. Recent experiments have assessed the effects of LTD on pain perception by using a simple one‐dimensional rating scale. The psychophysical study investigated the impact of noxious LFS on the sensory and affective aspects of pain perception by multidimensional rating scales. In 20 healthy volunteers, nociceptive fibers of the left hand dorsum were electrically stimulated by a concentric electrode. Test stimulation series (15 stimuli each, 0.125Hz) were performed before (Pre) and after (Post) a conditioning LFS (1Hz, 20min) or no stimulation period (Control). Pain ratings concerning test stimulation and LFS were obtained by multidimensional assessment including Verbal rating scale of perceived stimulus intensity (VRS‐I) and unpleasantness (VRS‐U) and pain perception scale with sensory (SES‐S) and affective items (SES‐A). After the conditioning LFS, VRS‐I, VRS‐U, SES‐S, and SES‐A decreased as compared to Pre series and Control. During conditioning LFS, ratings decreased. Factor analysis of SES‐S revealed sole reduction of superficial sharp pain perception after conditioning LFS in contrast to Control experiment. Perception of deep rhythmic pain decreased over time. Deep constant pain and superficial heat pain were not affected. Electrical test stimulation via concentric electrode evokes sensory as well as affective pain perception. Both components decrease during noxious, conditioning LFS and remain depressed for at least one hour. Reduction of sharp pain points to Aδ fiber mediated LTD. These results stress the analgesic potency of LTD and its possible impact on future therapy in chronic pain.     

Minimal clinically important changes in chronic musculoskeletal pain intensity measured on a numerical rating scale.

OBJECTIVES: To determine the minimal clinically important difference (MCID) of changes in chronic musculoskeletal pain intensity that is most closely associated with improvement on the commonly used and validated measure of the patient's global impression of change (PGIC), and to estimate the dependency of the MCID on the baseline pain scores. METHODS: This was a prospective cohort study assessing patient's pain intensity by the numerical rating scale (NRS) at baseline and at the 3 month follow-up, and by a PGIC questionnaire. A one unit difference at the lowest end of the PGIC ("slightly better") was used to define MCID as it reflects the minimum and lowest degree of improvement that could be detected. In addition we also calculated the NRS changes best associated with "much better" (two units). In order to characterize the association between specific NRS change scores (raw or percent) and clinically important improvement, the sensitivity and specificity were calculated by the receiver operating characteristic (ROC) method. PGIC was used as an external criterion to distinguish between improved or non-improved patients. RESULTS: 825 patients with chronic musculoskeletal pain (233 with osteoarthritis of the knee, 86 with osteoarthritis of the hip, 133 with osteoarthritis of the hand, 290 with rheumatoid arthritis and 83 with ankylosing spondylitis) were followed up. A consistent relationship between the change in NRS and the PGIC was observed. On average, a reduction of one point or a reduction of 15.0% in the NRS represented a MCID for the patient. A NRS change score of -2.0 and a percent change score of -33.0% were best associated with the concept of "much better" improvement. For this reason these values can be considered as appropriate cut-off points for this measure. The clinically significant changes in pain are non-uniform along the entire NRS. Patients with a high baseline level of pain on the NRS (score of >7 cm), who experienced either a slight improvement or a higher level of response, had absolute raw and percent changes greater that did patients in the lower cohort (score of less than 4 cm). CONCLUSIONS: These results are consistent with the recently published findings generated by different methods and support the use of a "much better" improvement on the pain relief as a clinically important outcome. A further confirmation in other patient populations and different chronic pain syndromes will be needed.     

Intravenous dexketoprofen versus paracetamol in non-traumatic musculoskeletal pain in the emergency department: A randomized clinical trial

IntroductionAlthough acute musculoskeletal pain has a wide range of causes from tendinitis, muscle spasm, to bone and joint injuries, it is a frequent occurrence in emergency services. Paracetamol and non-steroidal anti-inflammatory analgesics (NSAID) are common used in the treatment of musculoskeletal pain. This study sets out to compare the effectiveness of intravenous dexketoprofen and paracetamol in musculoskeletal pain relief.MethodsThis prospective, randomized, double blind, controlled study was carried out in a university emergency room. The participating patients were randomized into two groups to receive either 50 mg of dexketoprofen or 1000 mg of paracetamol intravenously by rapid infusion in 150 ml of normal saline. Visual analogue scale (VAS), Numeric Rating Scala (NRS) was employed for pain measurement at baseline, after 15, after 30 and after 60 mins.Results200 patients were included in the study, excluding 7342 of them. The mean age of the patients was calculated as 32,6. Paracetamol and dexketoprofen intervention decreases NRS pain scores over time. When compared to all pain locations, the NRS pain score of the patients was found to be statistically more effective in dexketoprofen than in paracetamol (p = 0.001). Paracetamol and dexketoprofen intervention reduces pain VAS scores over time. When the VAS pain score of the patients was compared to all pain locations, dexketoprofen was found to be statistically more effective than paracetamol (p = 0.001).ConclusionIntravenous dexketoprofen seemed to achieve superior analgesia to intravenous paracetamol when compared with all pain locations in patients with non-traumatic musculoskeletal pain.     

Children's ratings of the intensity and unpleasantness of post-operative pain using facial expression scales.

This study explored whether global unidimensional self-report pain scales based on facial expression help children separately estimate the sensory and affective magnitude of post-operative pain. Ninety paediatric elective surgery patients (in two age groups: 5-9 and 10-15 years) used each of four scales to estimate pain intensity and pain affect during the first 2 days after surgery. The four scales were: Faces Pain Scale (FPS), Facial Affective Scale (FAS), and the Coloured Analogue Scale (CAS) (one for intensity and one for unpleasantness). As hypothesised, ratings on the FPS correlated more highly with analogue scale ratings for intensity than for unpleasantness, whereas ratings on the FAS correlated more highly with those on the analogue scale for unpleasantness than for intensity. Factor analysis indicated that although all measures loaded on a single dimension of distress, there was an additional weaker factor corresponding to a unique contribution of the FAS. No systematic age effects were observed. It was concluded that the FPS and the FAS may partly measure different aspects of the postoperative pain experience in children, although shared instrument variance may obscure true estimates of covariation in ratings of intensity and affective magnitude. The clinical relevance of the present results remains to be determined.     

Psychosocial predictors of labor pain

The relationship between labor pain and concomitant psychological state, in terms of prenatal anxiety levels and post-partum mood, has been studied. A consecutive series of primiparae (n = 129) was assessed at intervals over the course of their pregnancy and after delivery. State anxiety was measured at recruitment (10-14 weeks of pregnancy), 10 weeks, 32 weeks and at labor. Labor pain was assessed on the McGill Pain Questionnaire (MPQ) and visual analog rating scales. Pain ratings on the MPQ were found to be high when compared to other clinical pain groups. Drug use in labor emerged as the strongest predictor of pain ratings on the MPQ total, sensory and affective scales, accounting for 11, 9 and 7% of the variance respectively. Anxiety scores at 32 weeks accounted for a further 5% of the variance and emerged as the best predictor of MPQ evaluative scores and visual analog ratings. A significant association was found between pain ratings and ratings of post-partum mood. Neither attendance at preparatory classes nor initial attitudes towards the neonate were related to pain scores.     

Increased sensitivity to physical activity among individuals with knee osteoarthritis: Relation to pain outcomes,psychological factors,and responses to quantitative sensory testing

Recent findings suggest that certain individuals with musculoskeletal pain conditions have increased sensitivity to physical activity (SPA) and respond to activities of stable intensity with increasingly severe pain. This study aimed to determine the degree to which individuals with knee osteoarthritis (OA) show heightened SPA in response to a standardized walking task and whether SPA cross-sectionally predicts psychological factors, responses to quantitative sensory testing (QST), and different OA-related outcomes. One hundred seven adults with chronic knee OA completed self-report measures of pain, function, and psychological factors, underwent QST, and performed a 6-min walk test. Participants rated their discomfort levels throughout the walking task; an index of SPA was created by subtracting first ratings from peak ratings. Repeated-measure analysis of variance revealed that levels of discomfort significantly increased throughout the walking task. A series of hierarchical regression analyses determined that after controlling for significant covariates, psychological factors, and measures of mechanical pain sensitivity, individual variance in SPA predicted self-report pain and function and performance on the walking task. Analyses also revealed that both pain catastrophizing and the temporal summation of mechanical pain were significant predictors of SPA and that SPA mediated the relationship between catastrophizing and self-reported pain and physical function. The discussion addresses the potential processes contributing to SPA and the role it may play in predicting responses to different interventions for musculoskeletal pain conditions.     

Validation of the Pain Sensitivity Questionnaire in chronic pain patients

Recently, a self-rating measure for pain perception based on imagined painful daily life situations, the Pain Sensitivity Questionnaire (PSQ), has been developed and shown to correlate with experimentally obtained pain intensity ratings in healthy subjects. Here, we assessed the validity of the PSQ for investigation of general pain perception (ie, pain perception outside the site of clinical pain) in chronic pain patients. PSQ scores were obtained in 134 chronic pain patients and compared to those of 185 healthy control subjects. In a subgroup of 46 chronic pain patients, we performed experimental pain testing outside the clinical pain site, including different modalities (heat, cold, pressure, and pinprick) and different measures (pain thresholds, pain intensity ratings). Results show that PSQ scores were significantly correlated with both experimental pain intensity ratings (Pearson's r=0.71, P<.001) and experimental pain thresholds (r=-0.52, P<.001). In addition, chronic pain patients exhibited significantly elevated PSQ scores as compared to healthy controls, consistent with the generalized increase of experimentally determined pain perception that has repeatedly been reported in chronic pain patients. These results demonstrate that the PSQ constitutes a valid self-rating measure of pain perception outside the clinical pain site in chronic pain patients and might serve as an alternative to experimental assessment of pain perception outside the clinical pain site in situations where experimental pain testing is not feasible.     

Predictors of postoperative movement and resting pain following total knee replacement

This study determined preoperative predictors of movement and resting pain following total knee replacement (TKR). We hypothesized that younger patients with higher preoperative pain intensity, pain sensitivity, trait anxiety, pain catastrophizing, and depression would be more likely to experience higher postoperative movement pain than older patients with lower scores on these variables prior to surgery, and that predictors would be similar for resting pain. Demographics, analgesic intake, anxiety, depression, pain catastrophizing, resting pain, movement pain (ie, during active knee range of motion), and quantitative sensory tests were performed preoperatively on 215 participants scheduled for a unilateral TKR. On postoperative day 2, analgesic intake, resting pain, and movement pain were again assessed. Significant predictors of moderate or severe movement pain were higher preoperative movement pain, von Frey pain intensity, and heat pain threshold. People with severe movement pain preoperatively were 20 times more likely to have severe movement pain postoperatively. When the influence of preoperative movement pain was removed, depression became a predictor. Significant predictors of moderate to severe resting pain were higher preoperative resting pain, depression, and younger age. These results suggest that patients with higher preoperative pain and depression are more likely to have higher pain following TKR, and younger patients may have higher resting pain. Cutaneous pain sensitivity predicted movement pain but not resting pain, suggesting that mechanisms underlying movement pain are different from resting pain. Aggressive management of preoperative pain, pain sensitivity, and depression prior to surgery may facilitate postoperative recovery.     

Attentional modulation fails to attenuate the subjective pain experience in chronic,unexplained pain

Background: Chronic, unexplained pain is a common, ill‐understood clinical problem. Increased sensitivity for pain and other stimuli is often implied as an underlying mechanism. Attentional processes influence central pain processing and might mediate hypersensitivity at a cerebral level. Aims: To study patients with chronic, unexplained pain with respect to (a) subjective pain experience; (b) effects of attentional manipulation; (c) level at which alterations in pain processing occur: locally (symptomatic body region), or generalised. Methods: We compared 16 patients with chronic, unexplained limb pain with 16 matched healthy controls. Pain thresholds to electrical stimuli were recorded. Subjects then received individually thresholded painful and non‐painful stimuli, with manipulation of attention towards or away from pain. The intensity of pain perception was recorded by means of visual analogue scales (VAS). Pain thresholds and effects of Attention and Laterality on VAS scores were compared between groups by means of general linear modelling (restricted to 12 patients with unilateral pain and 12 controls). Results: Distraction increased thresholds for pain in healthy volunteers, but this effect was significantly attenuated in patients. Significant interactions between attention‐effects, stimulus laterality and stimulus intensity indicated that VAS scores for painful stimuli were attenuated during distraction in healthy controls, but not in pain patients. Conclusions: Results support the notion that pain processing is enhanced in chronic, unexplained pain, and that the influence of attentional modulation on pain processing is attenuated. Potential cerebral mechanisms are changes in either attentional allocation or attention‐mediated descending pain modulation. The changes seem to occur at a generalised level.