Hypervigilance as Predictor of Postoperative Acute Pain: Its Predictive Potency Compared With Experimental Pain Sensitivity, Cortisol Reactivity, and Affective State

Hydrocortisone Differentially Affects Reinstatement of Pain-related Responses in Patients With Chronic Back Pain and Healthy Volunteers

Despite the crucial role of effective and sustained extinction of conditioned pain-related fear in cognitive-behavioral treatment approaches for chronic pain, experimental research on extinction memory retrieval in chronic pain remains scarce. In healthy populations, extinction efficacy of fear memory is affected by stress. Therefore, we investigated the effects of oral hydrocortisone administration on the reinstatement of pain-related associations in 57 patients with non-specific chronic back pain (CBP) and 59 healthy control (HC) participants in a differential pain-related conditioning paradigm within a placebo-controlled, randomized, and double-blind design. Participants' skin conductance responses indicate hydrocortisone-induced reinstatement effects in HCs but no observable reinstatement in HCs receiving placebo treatment. Interestingly, these effects were reversed in patients with CBP, that is, reinstatement responses were only observed in the placebo and not in the hydrocortisone group. Our findings corroborate previous evidence of stress-induced effects on extinction efficacy and reinstatement of fear memory in HCs, extending them into the pain context, and call for more research to clarify the role of stress in fear extinction and return of fear phenomena possibly contributing to treatment failure in chronic pain treatment. PERSPECTIVE: Opposing effects in HCs and patients with non-specific CBP may be associated with changes in the patients' stress systems. These findings could be of relevance to optimizing psychological, extinction-based treatment approaches.

The overgeneralization of pain-related fear in individuals with higher pain sensitivity: A behavioral and event-related potential study

Fear generalization contributes to the development and maintenance of pain. Pain sensitivity has been proposed to predict the strength of fear responses to aversive stimuli. However, whether individual variation in pain sensitivity affects pain-related fear generalization and its underlying cognitive processing remains unclear. To address this gap, we recorded behavioral and event-related potential (ERP) data among 22 high pain sensitivity (HPS) and 22 low pain sensitivity (LPS) healthy adults when exposed to a fear generalization paradigm. The behavioral results indicate that the HPS group displayed higher unconditioned stimulus expectancy and greater fear, arousal, and anxiety ratings to conditioned stimulus and generalization stimulus than the LPS group (all p values < 0.05). The ERP results showed that the HPS group exhibited a larger late positive potential evoked by GS2, GS3 and CS- (all p < 0.005) but a smaller N1 evoked by all CS and GSs (all p values < 0.05) relative to the LPS group. These findings suggest that individuals with a high level of pain sensitivity allocate more attention resources to pain-related threatening stimuli, which contributes to an overgeneralization of pain-related fear.

Pain-free default mode network connectivity contributes to tonic experimental pain intensity beyond the role of negative mood and other pain-related factors

BACKGROUND

Alterations in the default mode network (DMN) connectivity across pain stages suggest a possible DMN involvement in the transition to persistent pain.

AIM

This study examined whether pain-free DMN connectivity at lower alpha oscillations (8-10 Hz) accounts for a unique variation in experimental peak pain intensity beyond the contribution of factors known to influence pain intensity.

METHODS

Pain-free DMN connectivity was measured with electroencephalography prior to 1 h of capsaicin-evoked pain using a topical capsaicin patch on the right forearm. Pain intensity was assessed on a (0-10) numerical rating scale and the association between peak pain intensity and baseline measurements was examined using hierarchical multiple regression in 52 healthy volunteers (26 women). The baseline measurements consisted of catastrophizing (helplessness, rumination, magnification), vigilance, depression, negative and positive affect, sex, age, sleep, fatigue, thermal and mechanical pain thresholds and DMN connectivity (medial prefrontal cortex [mPFC]-posterior cingulate cortex [PCC], mPFC-right angular gyrus [rAG], mPFC-left Angular gyrus [lAG], rAG-mPFC and rAG-PCC).

RESULTS

Pain-free DMN connectivity increased the explained variance in peak pain intensity beyond the contribution of other factors (ΔR2  = 0.10, p = 0.003), with the final model explaining 66% of the variation (R2  = 0.66, ANOVA: p < 0.001). In this model, negative affect (β = 0.51, p < 0.001), helplessness (β = 0.49, p = 0.007), pain-free mPFC-lAG connectivity (β = 0.36, p = 0.003) and depression (β = -0.39, p = 0.009) correlated significantly with peak pain intensity. Interestingly, negative affect and depression, albeit both being negative mood indices, showed opposing relationships with peak pain intensity.

CONCLUSIONS

This work suggests that pain-free mPFC-lAG connectivity (at lower alpha) may contribute to individual variations in pain-related vulnerability.

SIGNIFICANCE

These findings could potentially lead the way for investigations in which DMN connectivity is used in identifying individuals more likely to develop chronic pain.

Neural underpinnings of preferential pain learning and the modulatory role of fear

Due to its unique biological relevance, pain-related learning might differ from learning from other aversive experiences. This functional magnetic resonance imaging study compared neural mechanisms underlying the acquisition and extinction of different threats in healthy humans. We investigated whether cue-pain associations are acquired faster and extinguished slower than cue associations with an equally unpleasant tone. Additionally, we studied the modulatory role of stimulus-related fear. Therefore, we used a differential conditioning paradigm, in which somatic heat pain stimuli and unpleasantness-matched auditory stimuli served as US. Our results show stronger acquisition learning for pain- than tone-predicting cues, which was augmented in participants with relatively higher levels of fear of pain. These behavioral findings were paralleled by activation of brain regions implicated in threat processing (insula, amygdala) and personal significance (ventromedial prefrontal cortex). By contrast, extinction learning seemed to be less dependent on the threat value of the US, both on the behavioral and neural levels. Amygdala activity, however, scaled with pain-related fear during extinction learning. Our findings on faster and stronger (i.e. "preferential") pain learning and the role of fear of pain are consistent with the biological relevance of pain and may be relevant to the development or maintenance of chronic pain.

Exploring Associations between Healthcare Use and Demographics, Pain and Pain Cognitions in People Scheduled for Surgery for Lumbar Radiculopathy: A Cross-Sectional Study

This cross-sectional study explored associations between demographics, pain intensity and cognitions on the one hand and healthcare use (HCU) on the other hand in people undergoing surgery for lumbar radiculopathy. HCU during the 2 months preceding surgery was evaluated using a retrospective questionnaire. Demographics included sex, age and level of education and equivalent income. Back and leg pain intensity were evaluated using a visual analogue scale. Pain cognitions were assessed with the Tampa scale of kinesiophobia, the pain catastrophizing scale and the pain vigilance and awareness questionnaire. The sample comprised 120 participants (52% males; 49 years (Quartile (Q)1-Q3: 37.3-57.43)). The number of visits to the general practitioner was associated with sex (incidence rate ratio (IRR) for males = 0.811; p = 0.050), pain catastrophizing (IRR = 1.010; p = 0.041), pain magnification (IRR = 1.058; p = 0.004) and leg pain intensity (IRR = 1.004; p = 0.038). The number of neurosurgeon visits was associated with level of education (IRR moderate education = 1.518; p = 0.016 (reference: low education)). Receiving zero physiotherapy visits was associated with higher back pain intensity (Beta = 0.018; p = 0.028). Highest level of analgesics used was associated with sex (IRR for males = 0.502; p = 0.047) and leg pain (IRR = 1.014; p = 0.034). Only the association between general practitioner visits and pain magnification remained significant in multivariable analyses (IRR = 1.061; p = 0.033). The results suggest a rather indirect relationship between HCU and demographics, pain intensity and cognitions, involving a potential interplay between several patient- and healthcare system-related factors.

Autobiographical memory predicts postsurgical pain up to 12 months after major surgery

ABSTRACT

Recent cross-sectional studies have identified differences in autobiographical memory (AM) among individuals with chronic pain, but the temporal relationship between the 2 is unknown. Moreover, AM has yet to be studied in patients undergoing major surgery. This study addressed these gaps by conducting a prospective, longitudinal study of memory performance, postsurgical pain, and psychosocial factors in 97 adult participants scheduled for major surgery. Memories were evaluated using the Autobiographical Memory Test before and one month after surgery when participants were asked to recall personal events related to positive and pain-related word cues. Responses were coded for level of specificity, emotional valence, and surgery-related content. Questionnaires assessing presence/absence of pain and psychological functioning were administered before and at 1-, 3-, 6-, and 12-month follow-ups. Generalized estimating equations modelled pain at each postsurgical time point with memory variables as predictors. As hypothesized, higher numbers of specific pain memories recalled before surgery predicted lower odds of pain across all time points (OR = 0.58, 95% CI [0.37-0.91]). Participants who took longer to recall pain memories before surgery (OR = 2.65, 95% CI [1.31-5.37]) and those who produced more surgery-related content at the one-month assessment (OR = 1.31, 95% CI [1.02-1.68]) had greater odds of reporting postsurgical pain up to 12 months later. These findings indicate that presurgical AM biases are risk factors for development and maintenance of postsurgical pain. To the extent that these biases are causal, presurgical interventions that modify the quality and content of patients' memories may prove to be promising strategies in the prevention of chronic postsurgical pain.

Autonomic Nervous System Function and Central Pain Processing in People With Frozen Shoulder: A Case-control Study

OBJECTIVES

The pathophysiology of a frozen shoulder (FS) is thought to be related to chronic inflammation. Chronic inflammation may disturb the immune system and consequently the nervous system as part of an overarching system. The aim of this study was to determine the presence of disturbed autonomic nervous system function and altered central pain processing (CPP) in patients with FS. Secondarily, the presence of psychological variables (catastrophizing and hypervigilance) and self-reported associated symptoms of altered CPP in patients with FS were investigated.

METHODS

Patients with FS and healthy controls completed the Composite Autonomic Symptom Score (autonomic function) and underwent quantitative sensory testing to assess tactile sensitivity (ie, allodynia), pressure pain thresholds (PPTs, ie, hyperalgesia), temporal summation of pain, and Conditioned Pain Modulation (CPM). Psychological issues were explored with the Pain Catastrophizing Scale and the Pain Vigilance and Awareness Questionnaire, and self-reported symptoms associated with altered CPP were determined with the Central Sensitization Inventory.

RESULTS

Thirty-two patients with FS and 35 healthy controls were analyzed in the study. Patients with FS showed more self-reported autonomic symptoms and symptoms of altered CPP, higher levels of pain catastrophizing and hypervigilance, and are more sensitive to tactile touches and mechanical pressure compared with controls.

DISCUSSION

On the basis of the effect sizes, between-group differences in allodynia, hyperalgesia, catastrophizing, and hypervigilance were clinically relevant, but only local allodynia, hyperalgesia, catastrophizing, and hypervigilance were statistically different. Therefore, obvious altered CPP was not present at the group level in patients with FS compared with controls.

Impaired pain-related threat and safety learning in patients with chronic back pain

ABSTRACT

Pain-related learning mechanisms likely play a key role in the development and maintenance of chronic pain. Previous smaller-scale studies have suggested impaired pain-related learning in patients with chronic pain, but results are mixed, and chronic back pain (CBP) particularly has been poorly studied. In a differential conditioning paradigm with painful heat as unconditioned stimuli, we examined pain-related acquisition and extinction learning in 62 patients with CBP and 61 pain-free healthy male and female volunteers using valence and contingency ratings and skin conductance responses. Valence ratings indicate significantly reduced threat and safety learning in patients with CBP, whereas no significant differences were observed in contingency awareness and physiological responding. Moreover, threat learning in this group was more impaired the longer patients had been in pain. State anxiety was linked to increased safety learning in healthy volunteers but enhanced threat learning in the patient group. Our findings corroborate previous evidence of altered pain-related threat and safety learning in patients with chronic pain. Longitudinal studies exploring pain-related learning in (sub)acute and chronic pain are needed to further unravel the role of aberrant pain-related learning in the development and maintenance of chronic pain.

Acquisition learning is stronger for aversive than appetitive events

Appetitive and aversive learning are both key building blocks of adaptive behavior, yet knowledge regarding their differences is sparse. Using a capsaicin heat pain model in 36 healthy participants, this study directly compared the acquisition and extinction of conditioned stimuli (CS) predicting pain exacerbation and relief. Valence ratings show stronger acquisition during aversive compared to appetitive learning, but no differences in extinction. Skin conductance responses and contingency ratings confirmed these results. Findings were unrelated to individual differences in pain sensitivity or psychological factors. Our results support the notion of an evolutionarily hardwired preponderance to acquire aversive rather than appetitive cues as is protective for acute aversive states such as pain but may contribute to the development and maintenance of clinical conditions such as chronic pain, depression or anxiety disorders.

In this study, acquisition and extinction of conditioned stimuli are compared in a capsaicin heat pain paradigm in healthy human participants. The results demonstrate a preponderance to acquire aversive rather than appetitive cues, which could initially have a protective function but eventually contribute to the maintenance of chronic pain.

Does pain modality play a role in the interruptive function of acute visceral compared with somatic pain?

ABSTRACT

Acute pain captures attentional resources and interferes with ongoing cognitive processes, including memory encoding. Despite broad clinical implications of this interruptive function of pain for the pathophysiology and treatment of chronic pain conditions, existing knowledge exclusively relies on studies using somatic pain models. Visceral pain is highly prevalent and seems to be more salient and threatening, suggesting that the interruptive function of pain may be higher in acute visceral compared with somatic pain. Implementing rectal distensions as a clinically relevant experimental model of visceral pain along with thermal cutaneous pain for the somatic modality, we herein examined the impact of pain modality on visual processing and memory performance in a visual encoding and recognition task and explored the modulatory role of pain-related fear and expectation in 30 healthy participants. Despite careful and dynamically adjusted matching of stimulus intensities to perceived pain unpleasantness over the course of trials, we observed greater impairment of cognition performance for the visceral modality with a medium effect size. Task performance was not modulated by expectations or by pain-related fear. Hence, even at matched unpleasantness levels, acute visceral pain is capable of interfering with memory encoding, and this impact seems to be relatively independent of pain-related cognitions or emotions, at least in healthy individuals. These results likely underestimate the detrimental effect of chronic pain on cognitive performance, which may be particularly pronounced in acute and chronic visceral pain.

The Influence of Preoperative Mood and Treatment Expectations on Early Postsurgical Acute Pain After a Total Knee Replacement

BACKGROUND

Reducing postoperative pain immediately after surgery is crucial because severe postoperative pain reduces quality of life and increases the likelihood that patients develop chronic pain. Even though postoperative pain has been widely studied and there are national guidelines for pain management, the postoperative course is differently from one patient to the next. Different postoperative courses could be explained by factors related to the treatment context and the patients. Preoperative emotional states and treatment expectations are significant predictors of postoperative pain. However, the interaction between emotional states and preoperative treatment expectations and their effect on postoperative pain have not yet been studied. The aim of our study was to identify the interaction between emotional states, treatment expectation and early postsurgical acute pain.

METHODS

In this prospective clinical trial, we enrolled patients who had received a TKR at a German hospital between October 2015 and March 2019. Patients rated their preoperative pain on a numeric rating scale (NRS) 0-10 (0 = no pain and 10 = worst pain imaginable), their emotional states preoperatively on the Pain and State of Health Inventory (PHI), their preoperative treatment expectations on the Stanford Expectation of Treatment Scale (SETS), and their postoperative level of pain on a NRS 0-10.

FINDINGS

The questionnaires were completed by 122 patients (57% female). Emotional states predict negative treatment expectation F(6, 108) = 8.32, p < 0.001, with an excellent goodness-of-fit, R² = 0.31. Furthermore, a mediator analysis revealed that the indirect effects and therefore relationship between the emotional states sad (ab = 0.06, 95% CI[0.01, 0.14]), anxious (ab = 0.13, 95% CI[0.04, 0.22]), and irritable (ab = 0.09, 95% CI[0.03, 0.17]) and postoperative pain is fully mediated by negative treatment expectations. Whereas the emotional states tired (ab = 0.09, 95% CI[0.03, 0.17]), dizzy/numb (ab = 0.07, 95% CI[0.01, 0.20]), weak (ab = 0.08, 95% CI[0.03, 0.16] are partially mediated by negative treatment expectations.

CONCLUSION

The relationship between emotional states and postoperative pain is mediated by negative treatment expectations. Therefore, innovative treatment strategies to reduce postoperative pain should focus on eliminating negative treatment expectation through establishing a differentiated preoperative expectation management program that also focuses on emotional states.

Autonomic, endocrine, and psychological stress responses to different forms of blood draw

Background

Although fingerstick is often favorably compared to venipuncture as a less invasive method of drawing blood for clinical labs, there is little empirical research that compares physical and psychological stress responses to fingerstick vs. venipuncture (blood draw using a needle in the arm) within the same person.

Methods and findings

We assessed changes in cortisol (a stress hormone), heart rate variability (a marker of autonomic stress), and psychological stress in 40 healthy women who completed both venipuncture and fingerstick. Contrary to our predictions, there was a significant decline in cortisol across conditions, with greater decline from pre- to post-draw in response to venipuncture than fingerstick. There were similar patterns of rise and fall in heart rate variability in both types of blood draw, suggestive of mild vasovagal responses. Psychological measures of stress (such as negative emotion and perceived stress) were generally stronger predictors of participant’s reported pain and blood draw preferences than physical stress measures.

Conclusions

These findings challenge the characterization of fingerstick as necessarily “less invasive” than venipuncture, as participant’s stress responses to fingerstick were equivalent to (and for some measures greater than) their response to venipuncture. Heart rate variability response to fingerstick significantly predicted that individual’s vasovagal-like responses to venipuncture, suggesting that measuring heart rate variability during pre-donation hemoglobin testing may identify donors at risk for adverse events during venipuncture.

The effects of attentional and interpretation biases on later pain outcomes among younger and older adults: A prospective study

BACKGROUND

Studies examining the effect of biased cognitions on later pain outcomes have primarily focused on attentional biases, leaving the role of interpretation biases largely unexplored. Also, few studies have examined pain-related cognitive biases in elderly persons. The current study aims to fill these research gaps.

METHODS

Younger and older adults with and without chronic pain (N = 126) completed an interpretation bias task and a free-viewing task of injury and neutral scenes at baseline. Participants' pain intensity and disability were assessed at baseline and at a 6-month follow-up. A machine-learning data-driven approach to analysing eye movement data was adopted.

RESULTS

Eye movement analyses revealed two common attentional pattern subgroups for scene-viewing: an "explorative" group and a "focused" group. At baseline, participants with chronic pain endorsed more injury-/illness-related interpretations compared to pain-free controls, but they did not differ in eye movements on scene images. Older adults interpreted illness-related scenarios more negatively compared to younger adults, but there was also no difference in eye movements between age groups. Moreover, negative interpretation biases were associated with baseline but not follow-up pain disability, whereas a focused gaze tendency for injury scenes was associated with follow-up but not baseline pain disability. Additionally, there was an indirect effect of interpretation biases on pain disability 6 months later through attentional bias for pain-related images.

CONCLUSIONS

The present study provided evidence for pain status and age group differences in injury-/illness-related interpretation biases. Results also revealed distinct roles of interpretation and attentional biases in pain chronicity.

SIGNIFICANCE

Adults with chronic pain endorsed more injury-/illness-related interpretations than pain-free controls. Older adults endorsed more illness interpretations than younger adults. A more negative interpretation bias indirectly predicted pain disability 6 months later through hypervigilance towards pain.

Psychophysical predictors of experimental muscle pain intensity following fatiguing calf exercise

Musculoskeletal pain affects approximately 20% of the population worldwide and represents one of the leading causes of global disability. As yet, precise mechanisms underlying the development of musculoskeletal pain and transition to chronicity remain unclear, though individual factors such as sleep quality, physical activity, affective state, pain catastrophizing and psychophysical pain sensitivity have all been suggested to be involved. This study aimed to investigate whether factors at baseline could predict musculoskeletal pain intensity to an experimental delayed onset of muscle soreness (DOMS) pain model. Demographics, physical activity, pain catastrophizing, affective state, sleep quality, isometric force production, temporal summation of pain, and psychophysical pain sensitivity using handheld and cuff algometry were assessed at baseline (Day-0) and two days after (Day-2) in 28 healthy participants. DOMS was induced on Day-0 by completing eccentric calf raises on the non-dominant leg to fatigue. On Day-2, participants rated pain on muscle contraction (visual analogue scale, VAS, 0-10cm) and function (Likert scale, 0–6). DOMS resulted in non-dominant calf pain at Day-2 (3.0±2.3cm), with significantly reduced isometric force production (P<0.043) and handheld pressure pain thresholds (P<0.010) at Day-2 compared to Day-0. Linear regression models using backward selection predicted from 39.3% (P<0.003) of VAS to 57.7% (P<0.001) of Likert score variation in DOMS pain intensity and consistently included cuff pressure pain tolerance threshold (P<0.01), temporal summation of pain (P<0.04), and age (P<0.02) as independent predictive factors. The findings indicate that age, psychological and central pain mechanistic factors are consistently associated with pain following acute muscle injury.

Brief preoperative mind-body therapies for total joint arthroplasty patients: a randomized controlled trial

ABSTRACT

Although knee and hip replacements are intended to relieve pain and improve function, up to 44% of knee replacement patients and 27% of hip replacement patients report persistent postoperative joint pain. Improving surgical pain management is essential. We conducted a single-site, 3-arm, parallel-group randomized clinical trial conducted at an orthopedic clinic, among patients undergoing total joint arthroplasty (TJA) of the hip or knee. Mindfulness meditation (MM), hypnotic suggestion (HS), and cognitive-behavioral pain psychoeducation (cognitive-behavioral pain psychoeducation) were each delivered in a single, 15-minute group session as part of a 2-hour, preoperative education program. Preoperative outcomes-pain intensity, pain unpleasantness, pain medication desire, and anxiety-were measured with numeric rating scales. Postoperative physical functioning at 6-week follow-up was assessed with the Patient-Reported Outcomes Measurement Information System Physical Function computer adaptive test. Total joint arthroplasty patients were randomized to preoperative MM, HS, or cognitive-behavioral pain psychoeducation (n = 285). Mindfulness meditation and HS led to significantly less preoperative pain intensity, pain unpleasantness, and anxiety. Mindfulness meditation also decreased preoperative pain medication desire relative to cognitive-behavioral pain psychoeducation and increased postoperative physical functioning at 6-week follow-up relative to HS and cognitive-behavioral pain psychoeducation. Moderation analysis revealed the surgery type did not differentially impact the 3 interventions. Thus, a single session of a simple, scripted MM intervention may be able to immediately decrease TJA patients' preoperative clinical symptomology and improve postoperative physical function. As such, embedding brief MM interventions in surgical care pathways has the potential to improve surgical outcomes for the millions of patients receiving TJA each year.

A virtual reality-based intervention for surgical patients: study protocol of a randomized controlled trial

Background

Pain after surgery is normal, and treatments, including both pharmacological and psychological components, are fundamental for proper postoperative care. While several trials have investigated the analgesic effect of traditional non-pharmacological treatments, such as cognitive behavior therapies, the newer ways of delivering psychological interventions for pain after surgery are scarcely investigated. The aim of this randomized controlled trial (RCT) is to determine if delivering the psychological content through virtual reality (VR) along with the standard pharmacological treatment return better pain relief outcomes than standard care in adult patients following surgery.

Methods

This is a protocol of a parallel RCT conducted in one community hospital. In order to test the efficacy of VR environments for reducing pain intensity, in the following day after surgery, adults (18 to 65 years) will be randomly assigned to either (1) standard treatment after surgery (control group) or (2) VR based intervention along with standard treatment. It is intended that a minimum of 30 patients be recruited in each group. For estimating the intensity of pain, both self-report and physiological measures will be used. Repeated measures of pain outcomes will be taken before and after the intervention. Moreover, for allowing an in-depth investigation of the effect of VR environments, the primary outcome will be complemented with measures of the adverse effects, level of immersion, and level of presence in the VR environment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13063-021-05196-7.

Preoperative Pressure Pain Threshold Is Associated With Postoperative Pain in Short-Stay Anorectal Surgery: A Prospective Observational Study

BACKGROUND:

Postoperative pain management is key for patient satisfaction. Pressure pain threshold (PPT) has been studied in some surgical cohorts but has not been studied in relationship to acute postoperative pain in short-stay patients undergoing anorectal surgery. We hypothesized that preoperative finger PPT measurements can identify respective patients with higher postoperative pain. Aiming to understand the relationship with subjective postoperative pain perception, we tested the hypotheses that preoperative PPT is associated with postoperative Visual Analog Scale (VAS) pain scores and correlates with postoperative analgesic consumption in short-stay patients undergoing anorectal surgery.

METHODS:

We prospectively assessed preoperative PPT in a cohort undergoing anorectal surgery, known as a moderately to severely painful procedure. Linear mixed-effects models were used to assess the relationship with postoperative VAS pain scores at 1 and 3 days as well as 4 weeks postoperatively. Logistic regression was used to study the relationship with additional postoperative analgesic consumption.

RESULTS:

We studied 128 patients and found that preoperative PPT is significantly associated with postoperative pain (P value for interaction = .025). Logistic regression modeling additionally revealed an association between the preoperative PPT and the need for additional postoperative analgesics, with odds of requiring additional analgesia decreasing by about 10% for each 1-point increase in PPT (odds ratio [OR] = 0.90; 95% confidence interval [CI], 00.81–0.98; P = .012).

CONCLUSIONS:

Preoperative finger PPT is associated with postoperative pain and might help identify patients who are at risk of developing more severe postoperative pain on anorectal surgery. Especially in ambulatory and short-stay settings, this approach can help to address patients’ high variability in pain sensitivity to facilitate appropriate postoperative analgesia, timely discharge, and prevent readmission.

Predicted Versus Non-Predicted Opioid Administration Using Preoperative Pain Sensitivity in Patients Undergoing Gynecological Surgery: A Randomized-Controlled Trial

Individualized administration of opioids based on preoperative pain sensitivity may improve postoperative pain profiles. This study aimed to examine whether a predicted administration of opioids could reduce opioid-related adverse effects after gynecological surgery. Patients were randomized to the predicted group or control group. Participants received a preoperative sensory test to measure pressure pain thresholds. Patients were treated with a higher or lower (15 or 10 μg/mL) dose of fentanyl via intravenous patient-controlled analgesia. The opioid dose was determined according to pain sensitivity in the predicted group, while it was determined regardless of pain sensitivity in the control group. The primary outcome was the incidence of nausea over the first 48 h postoperative period. Secondary outcomes included postoperative pain scores and opioid requirements. There was no difference in the incidence of nausea (40.0% vs. 52.5% in predicted and control groups, respectively; p = 0.191) and postoperative pain scores (3.3 vs. 3.5 in predicted and control groups, respectively; p = 0.691). However, opioid consumptions were lower in the predicted group compared to the control group (median 406.0 vs. 526.5 μg; p = 0.042). This study showed that offering a predicted dose of opioids according to pain sensitivity did not affect the incidence of nausea and pain scores.

Quantitative Sensory Testing to Predict Postoperative Pain

Purpose of Review

We review the relevance of quantitative sensory testing (QST) in light of acute and chronic postoperative pain and associated challenges.

Recent Findings

Predicting the occurrence of acute and chronic postoperative pain with QST can help identify patients at risk and allows proactive preventive management. Generally, central QST testing, such as temporal summation of pain (TSP) and conditioned pain modulation (CPM), appear to be the most promising modalities for reliable prediction of postoperative pain by QST. Overall, QST testing has the best predictive value in patients undergoing orthopedic procedures.

Summary

Current evidence underlines the potential of preoperative QST to predict postoperative pain in patients undergoing elective surgery. Implementing QST in routine preoperative screening can help advancing traditional pain therapy toward personalized perioperative pain medicine.

Sleep Disturbances After General Anesthesia: Current Perspectives

The purpose of this article is to review (1) sleep mechanism under general anesthesia, harmful effects of postoperative sleep disturbances; (2) risk factors associated with postoperative sleep disturbances; (3) measures to prevent and improve postoperative sleep disturbances. General anesthesia changes the postoperative sleep structure especially in elderly patients after major surgery and results in a high incidence rate of sleep disturbances. Sleep disturbances produce harmful effects on postoperative patients and lead to a higher risk of delirium, more cardiovascular events, and poorer recovery. Some researchers do propose non-pharmacological treatments such as attention to environmental and psychological factors, application of electroacupuncture (EA) technology and pharmacological treatments are helpful, but larger high-quality clinical trials with longer following-up are needed to further investigate the efficacy and safety.

Enhanced pain-related conditioning for face compared to hand pain

Pain is evolutionarily hardwired to signal potential danger and threat. It has been proposed that altered pain-related associative learning processes, i.e., emotional or fear conditioning, might contribute to the development and maintenance of chronic pain. Pain in or near the face plays a special role in pain perception and processing, especially with regard to increased pain-related fear and unpleasantness. However, differences in pain-related learning mechanisms between the face and other body parts have not yet been investigated. Here, we examined body-site specific differences in associative emotional conditioning using electrical stimuli applied to the face and the hand. Acquisition, extinction, and reinstatement of cue-pain associations were assessed in a 2-day emotional conditioning paradigm using a within-subject design. Data of 34 healthy subjects revealed higher fear of face pain as compared to hand pain. During acquisition, face pain (as compared to hand pain) led to a steeper increase in pain-related negative emotions in response to conditioned stimuli (CS) as assessed using valence ratings. While no significant differences between both conditions were observed during the extinction phase, a reinstatement effect for face but not for hand pain was revealed on the descriptive level and contingency awareness was higher for face pain compared to hand pain. Our results indicate a stronger propensity to acquire cue-pain-associations for face compared to hand pain, which might also be reinstated more easily. These differences in learning and resultant pain-related emotions might play an important role in the chronification and high prevalence of chronic facial pain and stress the evolutionary significance of pain in the head and face.

Missed targets, reaction times, and arousal are related to trait anxiety and attention to pain during an experimental vigilance task with a painful target

Although hypervigilance may play a role in some clinical pain syndromes, experimental vigilance toward painful stimuli has been studied infrequently. We evaluated vigilance toward pain by using a continuous performance task (CPT), in which subjects responded to moderately intense painful target stimuli, occurring in a train of mildly painful nontargets. We assessed nondetected targets (misses), reaction times (RTs), and psychological activation (tense arousal). During time on task in CPTs of other sensory modalities, there is an increase in misses and RTs (vigilance decrement). We hypothesized that our CPT would influence vigilance performance related to pain, anxiety, and limitation of attentional resources. The results showed a decrement in vigilance over time as misses increased, although RTs were unchanged. While mind-wandering did not influence vigilance performance, intrinsic attention to pain drove both hit RTs and number of misses. This resulted in pain-focused subjects performing worse on the CPT pain task with slower RTs and more misses per block. During the CPT, the change in stimulus salience was related to the change in pain intensity, while pain unpleasantness correlated with tense arousal. CPT performance during experimental vigilance to pain and psychological activation were related to trait anxiety, as measured by the Spielberger State-Trait Anxiety Inventory and neuroticism, as measured by the NEO five factor inventory. Trait anxiety and neuroticism may play important roles in an individual's predisposition to dwell on pain and interpret pain as threatening.NEW & NOTEWORTHY Subjects detected moderately painful target stimuli in a train of mildly painful nontarget stimuli, which resulted in vigilance performance metrics including missed targets, reaction times, and psychological activation. These performance metrics were related to intrinsic attention to pain and trait anxiety. Subjects with high trait anxiety and neuroticism scores, with a predisposition to attend to pain, had greater tense arousal and poorer vigilance performance, which may be important psychological aspects of vigilance to pain.

Time course of attentional bias to painful facial expressions and the moderating role of attentional control: an eye-tracking study

Introduction

This study investigated the time course of attention to pain and examined the moderating effect of attentional control in the relationship between pain catastrophizing and attentional bias in chronic pain patients.

Methods

A total of 28 patients with chronic pain and 29 pain-free individuals observed pictures of pain, happy and neutral facial expressions while their gaze behaviour was recorded. Pain intensity and duration, anxiety, depression, stress, attentional control and pain catastrophizing were assessed by questionnaires.

Results

In all subjects, the pattern of attention for pain faces was characterized by initial vigilance, followed by avoidance. No significant difference was found between the two groups in terms of orientation towards the stimuli, the duration of first fixation, the average duration of fixation or number of fixations on the pain stimuli. Attentional control moderated the relationship between catastrophizing and overall dwell time for happy faces in pain patients, indicating that those with high attentional control and high catastrophizing focused more on happy faces, whereas the reverse was true for those with low attentional control.

Conclusion

This study supported the vigilance-avoidance pattern of attention to painful facial expressions and a moderation effect of attentional control in the association between pain catastrophizing and attentional bias to happy faces among pain patients.

Differential effects of experimentally induced anxiety and fear on pain: the role of anxiety sensitivity

Background: Anxiety has been associated with both increased and decreased pain perception. Rhudy and Meagher (2000) showed that pain sensitivity is enhanced by anxiety (anticipation of shocks), but diminished by fear (confrontation with shocks). A problem of this approach is the confounding of emotional and attentional effects: Administered shocks (fear induction) divert attention away from pain, which might account for lower pain in this condition. Moreover, heterogeneous findings in the past might be due to inter-individual differences in the proneness to react to anxiety and fear such as ones anxiety sensitivity (AS) level.

Objectives: Our aim was to clarify the association between anxiety, fear and pain. We used the NPU paradigm for inducing these emotions and recording pain sensitivity at once with one stimulus to prevent interference by distraction. We assumed that anxiety and fear affect pain differently. Moreover, we hypothesized that subjects with clinically relevant (high) AS (H-AS group) show enhanced pain perception in contrast to low AS subjects (L-AS group).

Method: Forty healthy subjects (female: N=20; age M=23.53 years) participated and H-AS or L-AS status was determined by clinically discriminating cut-off scores of the Anxiety Sensitivity Index-3 (ASI-III). Emotions were induced by the application of unpredictable (anxiety) and predictable (fear) electric stimuli. Pain ratings of electric stimuli were compared between the conditions. Startle reflex and anxiety ratings were recorded.

Results: Results showed no general effects of anxiety and fear on pain perception. However, anxiety enhanced pain sensitivity in H-AS subjects, whereas fear did not affect pain sensitivity. In L-AS subjects no effects on pain perception were found.

Conclusion: Results revealed that anxiety, not fear, enhanced pain perception but only in subjects with clinically relevant AS levels. This indicates that subclinical AS levels are sufficient to increase pain sensitivity, in uncertain situations.

Eye-movement behaviours when viewing real-world pain-related images

BACKGROUND

Pain-related cues are evolutionarily primed to capture attention, although evidence of attentional biases towards pain-related information is mixed in healthy individuals. The present study explores whether healthy individuals show significantly different eye-movement behaviours when viewing real-world pain-related scenes compared to neutral scenes. The effect of manipulating via written information the threat value of the pain-related scenes on eye-movement behaviours was also assessed.

METHODS

Participants were randomized to threatening (n = 28) and non-threatening (n = 27) information conditions. All completed a free-viewing task with real-world pain-related and neutral images while their eye movements were recorded.

RESULTS

Participants made significantly fewer fixations of significantly longer duration when viewing pain-related images compared to neutral images. No significant differences were found between threatening and non-threatening information groups in their pattern of eye movements.

CONCLUSIONS

This study shows that healthy individuals demonstrate attentional biases to pain-related real-world complex images compared to neutral images. Future research is needed to establish the implications of these biases, particularly in the context of acute pain, on the onset and/or subsequent maintenance of chronic pain conditions.

SIGNIFICANCE

Healthy individuals show different eye-movement behaviours when viewing pain-related scenes than neutral scenes, supporting evolutionary accounts of pain. Implications for the onset and/or maintenance of chronic pain need to be explored.

Does pain hypervigilance further impact the lack of habituation to pain in individuals with chronic pain? A cross-sectional pain ERP study

AIM

In chronic pain, habituation is believed to be impaired, and pain hypervigilance can enhance the pain experience. The goal of this study was to determine whether pain hypervigilance further worsens habituation of event-related potentials, measured in a pain-rating protocol of 25 painful somatosensory electrical stimuli, in patients with chronic pain.

METHODS

Pain hypervigilance was assessed with the Pain Vigilance Awareness Questionnaire and analyzed using the event-related fixed interval areas multilevel technique, which enables one to study within-session habituation. In a cohort of 111 participants, 33 reported chronic pain. This chronic pain group was compared with 33 pain-free individuals, matched for age and sex.

RESULTS

The relationship between pain status and habituation was not moderated by pain hypervigilance. Chronic pain status affected linear habituation and dishabituation (quadratic function) from 220 to 260 ms for nearly all electrodes, and from 580 to 640 ms for frontal electrodes. The effect of pain hypervigilance on habituation was observed primarily from 480 to 820 ms poststimulus for right-sided and central electrodes.

CONCLUSION

Pain hypervigilance and chronic pain independently influence habituation to painful stimuli - although not synergistically. To confirm that these effects are mediated by separate pathways, further research is required, in which electroencephalography is combined with other modalities with adequate spatial resolution, such as functional magnetic resonance imaging.

Vigilance behaviors and EEG activity in sustained attention may affect acute pain

During Sustained Attention to stimuli across many modalities neural activity often decreases over time on task, while Errors in task performance increase (Vigilance Decrement). Sustained Attention to pain has rarely been investigated experimentally despite its clinical significance. We have employed a Sustained Attention protocol (Continuous Performance Task, CPT) in which the subject counts painful laser stimuli (targets) when they occur randomly in a prolonged train of nonpainful nontargets. We hypothesize that the magnitude of the poststimulus oscillatory power divided by baseline power (Event-Related Spectral Perturbation, ERSP - scalp EEG) over Frontoparietal structures will decrease at all frequencies with time on task, while Beta ERSP (14-30Hz) will be correlated with Error Rates in performance of the CPT. During the CPT with a painful target ERSP was found in four separate Windows, as defined by both their frequency band and the time after the stimulus. A Vigilance Decrement was found which confirms that Sustained Attention to pain was produced by this CPT. In addition, Error Rates was correlated inversely with laser energy, and with ratings of pain unpleasantness and salience. Error Rates also were related directly to the Beta ERSP Window at scalp EEG electrodes over the central sulcus. Over time on task, the ERSP magnitude decreased in Alpha (8-14Hz) Window, was unchanged in early and late Delta/Theta Windows (0-8Hz), and increased in the Beta Window. The increase in Beta ERSP and a decrease in the Alpha ERSP occurred at the same EEG electrode over the parietal lobe to a significant degree across subjects. Overall, Beta activity increases with time on task, and with higher Error Rates as in the case of other modalities. In the case of pain increased Errors correspond to misidentification of painful and nonpainful stimuli and so modulate the sensation of pain under the influence of Sustained Attention.

Psychometric Properties of the German Version of the Pain Vigilance and Awareness Questionnaire (PVAQ) in Pain-Free Samples and Samples with Acute and Chronic Pain

Purpose

The way individuals attend to pain is known to have a considerable impact on the experience and chronification of pain. One method to assess the habitual “attention to pain” is the Pain Vigilance and Awareness Questionnaire (PVAQ). With the present study, we aimed to test the psychometric properties of the German version of the PVAQ across pain-free samples and across patients with acute and chronic pain.

Method

Two samples of pain-free individuals (student sample (N = 255)/non-student sample (N = 362)) and two clinical pain samples (acute pain patients (N = 105)/chronic pain patients (N = 36)) were included in this cross-sectional evaluation of the German PVAQ. Factor structure was assessed using exploratory and confirmatory factor analyses. Reliability was assessed using internal consistency (Cronbach’s alpha). Construct validity was tested by assessing correlations between PVAQ and theoretically related constructs.

Results

Exploratory factor analysis (non-student sample) and confirmatory factor analysis (student sample, acute pain patient sample) suggested that a two-factor solution best fitted our data (“attention to pain,” “attention to changes in pain”). Internal consistency ranged from acceptable to good in all four samples. As hypothesized, the PVAQ correlated significantly with theoretically related constructs in all four samples, suggesting good construct validity in pain-free individuals and in pain patients.

Conclusion

The German PVAQ shows good psychometric properties across samples of pain-free individuals and patients suffering from pain that are comparable to PVAQ versions of other languages. Thus, the German PVAQ seems to be a measure of pain vigilance equally valid as found in other countries.

Prediction of persistent post-operative pain: Pain-specific psychological variables compared with acute post-operative pain and general psychological variables

BACKGROUND

Psychological variables and acute post-operative pain are of proven relevance for the prediction of persistent post-operative pain. We aimed at investigating whether pain-specific psychological variables like pain catastrophizing add to the predictive power of acute pain and more general psychological variables like depression.

METHODS

In all, 104 young male patients undergoing thoracic surgery for pectus excavatum correction were studied on the pre-operative day (T0) and 1 week (T1) and 3 months (T2) after surgery. They provided self-report ratings (pain-related: Pain Catastrophizing Scale, Pain Anxiety Symptoms Scale = PASS, Pain Vigilance and Awareness Questionnaire = PVAQ; general psychological: Screening for Somatoform Symptoms, State-Anxiety Inventory-X1, Center for Epidemiologic Studies Depression Scale = CES-D). Additional predictors (T1) as well as criterion variables (T2) were pain intensity (Numerical Rating Scale) and pain disability (Pain Disability Index).

RESULTS

Three months after surgery, 25% of the patients still reported clinically relevant pain (pain intensity ≥3) and over 50% still reported pain-related disability. Acute post-operative pain as well as general psychological variables did not allow for a significant prediction of persistent post-operative pain; in contrast, pain-related psychological variables did. The best single predictors were PASS for pain intensity and PVAQ for pain disability.

CONCLUSIONS

Pain-related psychological variables derived from the fear-avoidance model contributed significantly to the prediction of persistent post-operative pain. The best possible compilation of these measures requires further research. More general psychological variables may become relevant predictors later in the medical history.

SIGNIFICANCE

Our results suggest that pain-specific psychological variables such as pain anxiety and pain hypervigilance add significantly to the prediction of persistent post-operative pain and might even outperform established predictors such as acute pain and general psychological variables. Clinicians might benefit from the development of time-economic screening tools based on these variables.

Quantitative sensory testing measures individual pain responses in emergency department patients

Background

Refining and individualizing treatment of acute pain in the emergency department (ED) is a high priority, given that painful complaints are the most common reasons for ED visits. Few tools exist to objectively measure pain perception in the ED setting. We speculated that variation in perception of fixed painful stimuli would explain individual variation in reported pain and response to treatment among ED patients.

Materials and methods

In three studies, we 1) describe performance characteristics of brief quantitative sensory testing (QST) in 50 healthy volunteers, 2) test effects of 10 mg oxycodone versus placebo on QST measures in 18 healthy volunteers, and 3) measure interindividual differences in nociception and treatment responses in 198 ED patients with a painful complaint during ED treatment. QST measures adapted for use in the ED included pressure sensation threshold, pressure pain threshold (PPT), pressure pain response (PPR), and cold pain tolerance (CPT) tests.

Results

First, all QST measures had high inter-rater reliability and test–retest reproducibility. Second, 10 mg oxycodone reduced PPR, increased PPT, and prolonged CPT. Third, baseline PPT and PPR revealed hyperalgesia in 31 (16%) ED subjects relative to healthy volunteers. In 173 (88%) ED subjects who completed repeat testing 30 minutes after pain treatment, PPT increased and PPR decreased (Cohen’s d_z 0.10–0.19). Verbal pain scores (0–10) for the ED complaint decreased by 2.2 (95% confidence intervals [CI]: 1.9, 2.6) (Cohen’s d_z 0.97) but did not covary with the changes in PPT and PPR (r=0.05–0.13). Treatment effects were greatest in ED subjects with a history of treatment for anxiety or depression (Cohen’s d_z 0.26–0.43) or with baseline hyperalgesia (Cohen’s d_z 0.40–0.88).

Conclusion

QST reveals individual differences in perception of fixed painful stimuli in ED patients, including hyperalgesia. Subgroups of ED patients with hyperalgesia and psychiatric history report larger treatment effects on ED pain and QST measures.

Are preoperative experimental pain assessments correlated with clinical pain outcomes after surgery? A systematic review

BACKGROUND

Pain after surgery is not uncommon with 30% of patients reporting moderate to severe postoperative pain. Early identification of patients prone to postoperative pain may be a step forward towards individualized pain medicine providing a basis for improved clinical management through treatment strategies targeting relevant pain mechanisms in each patient. Assessment of pain processing by quantitative sensory testing (QST) prior to surgery has been proposed as a method to identify patients at risk for postoperative pain, although results have been conflicting. Since the last systematic review, several studies investigating the association between postoperative pain and more dynamic measures of pain processing like temporal summation of pain and conditioned pain modulation have been conducted.

OBJECTIVES

According to the PRISMA guidelines, the aim of this systematic review was to evaluate whether assessment of experimental pain processing including measures of central pain mechanisms prior to surgery was associated with pain intensity after surgery.

METHODS

Systematic database searches in PubMed and EMBASE with the following search components: QST, association, and postoperative pain, for studies that assessed the association between QST and pain after surgery were performed. Two authors independently reviewed all titles and abstracts to assess their relevance for inclusion. Studies were included if (1) QST was performed prior to surgery, (2) pain was assessed after surgery, and (3) the association between QST and pain after surgery was investigated. Forty-four unique studies were identified, with 30 studies on 2738 subjects meeting inclusion criteria. The methodological quality of the include studies was assessed and data extraction included study population, type of surgery, QST variables, clinical pain outcome measure and main result.

RESULTS

Most studies showed moderate to high risk of bias. Type of surgery investigated include 7 studies on total knee replacement, 5 studies on caesarean section, 4 studies on thoracic surgery, 2 studies on herniotomy, 2 studies on hysterectomy/myomectomy, 1 study on tubal ligation, 1 study on gynecologic laparoscopy, 1 study on arthroscopic knee surgery, 1 study on shoulder surgery, 1 study on disc herniation surgery, 1 study on cholecystectomy, 1 study on percutaneous nephrolithotomy, 1 study on molar surgery, 1 study on abdominal surgery, and 1 study on total knee replacement and total hip replacement. The majority of the preoperative QST variables showed no consistent association with pain intensity after surgery. Thermal heat pain above the pain threshold and temporal summation of pressure pain were the QST variables, which showed the most consistent association with acute or chronic pain after surgery.

CONCLUSIONS

QST before surgery does not consistently predict pain after surgery. High quality studies investigating the presence of different QST variables in combination or along with other pain-related psychosocial factors are warranted to confirm the clinical relevance of QST prior to surgery.

IMPLICATIONS

Although preoperative QST does not show consistent results, future studies in this area should include assessment of central pain mechanisms like temporal summation of pressure pain, conditioned pain modulation, and responses to pain above the pain threshold since these variables show promising associations to pain after surgery.

[Psychological prophylaxis training for coping with postoperative pain. Long-term effects]

INTRODUCTION

The present study was performed to investigate the effect of multidimensional psychological prophylaxis training focusing on coping with cognitive-emotional pain on recovery within the first 12 months after surgery. The training included the following three components: (1) education about pain, analgesia and psychological aspects of coping with pain, (2) training for coping with pain and (3) body-centered relaxation.

MATERIAL AND METHODS

In the study 48 young male patients (surgical correction of a chest malformation) were assessed 1 day before surgery, at discharge and 3, 6 and 12 months postoperatively concerning postoperative pain intensity and pain disability as well as pain anxiety, pain catastrophizing and pain hypervigilance. Additionally, 24 of these patients received training on cognitive-emotional coping with pain 1 day before surgery and 1-3 days after surgery (each session 1 h).

RESULTS

The proportion of patients with clinically relevant improvement was significantly higher in the training group compared to the control group. This was the case for acute pain intensity (approximately 1 week after surgery), pain disability 3 months later and pain anxiety 12 months after surgery.

CONCLUSION

The resurgence of pain anxiety after 12 months could only be found in the control group and could be due to the upcoming surgical removal of the transsternal metal implant. The prophylaxis training can therefore be seen as a protective factor for long-term management of surgery-related consequences and future pain experiences.

Preserved Capacity for Placebo Analgesia in the Elderly

The prevalence of chronic pain rises with increasing age. It has been suggested that the mechanisms responsible for the development of chronic pain overlap with mechanisms involved in aging, potentially implicating age-related changes in descending modulatory pathways. This observation raises the question whether other forms of endogenous pain modulation, in particular placebo analgesia, become compromised with age. Because of the known contribution of placebo effects to analgesic treatment outcomes this question is of important clinical relevance. In this study, we compared the response to thermal painful stimuli and the capacity for endogenous pain modulation between younger and older adults using a well established placebo analgesia paradigm involving expectancy and conditioning components. We recruited 30 younger (age 23-40 years, mean = 27.04, standard error of the mean ± .61) and 24 older adults (60-80 years, mean = 69.3, standard error of the mean ± .89). We observed increased heat pain thresholds and higher pain intensity ratings (in response to physically identical heat stimulation) in the older compared with the younger group. However, the placebo analgesic response was comparable between both age groups of healthy participants. The preserved capacity for placebo analgesia in our sample of older participants highlights the potential to use nonpharmacological analgesic treatment strategies in this age group and to exploit placebo mechanisms as an add-on to existing analgesic (pharmacological) treatment strategies.

PERSPECTIVE

In contrast to the commonly shared view that endogenous pain modulation declines with age we found a comparable capacity for placebo analgesia in a group of healthy older and younger adults.

Reinstatement of pain-related brain activation during the recognition of neutral images previously paired with nociceptive stimuli

Remembering an event partially reactivates cortical and subcortical brain regions that were engaged during its experience and encoding. Such reinstatement of neuronal activation has been observed in different sensory systems, including the visual, auditory, olfactory, and somatosensory domain. However, so far, this phenomenon of incidental memory has not been explored in the context of pain. In this functional magnetic resonance imaging study, we investigated the neural reinstatement of pain-related and tone-related activations during the recognition of neutral images that had been encoded during (1) painful stimulation, (2) auditory stimulation of comparable unpleasantness, or (3) no additional stimulation. Stimulus-specific reinstatement was tested in 24 healthy male and female participants who performed a visual categorization task (encoding) that was immediately followed by a surprise recognition task. Neural responses were acquired in both sessions. Our data show a partial reinstatement of brain regions frequently associated with pain processing, including the left posterior insula, bilateral putamen, and right operculum, during the presentation of images previously paired with painful heat. This effect was specific to painful stimuli. Moreover, the bilateral ventral striatum showed stronger responses for remembered pain-associated images as compared with tone-associated images, suggesting a higher behavioral relevance of remembering neutral pictures previously paired with pain. Our results support the biological relevance of pain in that only painful but not equally unpleasant auditory stimuli were able to "tag" neutral images during their simultaneous presentation and reactivate pain-related brain regions. Such mechanisms might contribute to the development or maintenance of chronic pain and deserve further investigation in clinical populations.

Joint Mobilization Enhances Mechanisms of Conditioned Pain Modulation in Individuals With Osteoarthritis of the Knee

STUDY DESIGN

An experimental laboratory study with a repeated-measures crossover design.

BACKGROUND

Treatment effects of joint mobilization may occur in part by decreasing excitability of central nociceptive pathways. Impaired conditioned pain modulation (CPM) has been found experimentally in persons with knee and hip osteoarthritis, indicating impaired inhibition of central nociceptive pathways. We hypothesized increased effectiveness of CPM following application of joint mobilization, determined via measures of deep tissue hyperalgesia.

OBJECTIVE

To examine the effect of joint mobilization on impaired CPM.

METHODS

An examination of 40 individuals with moderate/severe knee osteoarthritis identified 29 (73%) with impaired CPM. The subjects were randomized to receive 6 minutes of knee joint mobilization (intervention) or manual cutaneous input only, 1 week apart. Deep tissue hyperalgesia was examined via pressure pain thresholds bilaterally at the knee medial joint line and the hand at baseline, postintervention, and post-CPM testing. Further, vibration perception threshold was measured at the medial knee epicondyle at baseline and post-CPM testing.

RESULTS

Joint mobilization, but not cutaneous input intervention, resulted in a global increase in pressure pain threshold, indicated by diminished hyperalgesic responses to pressure stimulus. Further, CPM was significantly enhanced following joint mobilization. Diminished baseline vibration perception threshold acuity was enhanced following joint mobilization at the knee that received intervention, but not at the contralateral knee. Resting pain was also significantly lower following the joint intervention.

CONCLUSION

Conditioned pain modulation was enhanced following joint mobilization, demonstrated by a global decrease in deep tissue pressure sensitivity. Joint mobilization may act via enhancement of descending pain mechanisms in patients with painful knee osteoarthritis.

Reward devaluation: Dot-probe meta-analytic evidence of avoidance of positive information in depressed persons

Cognitive theories of depression and anxiety have traditionally emphasized the role of attentional biases in the processing of negative information. The dot-probe task has been widely used to study this phenomenon. Recent findings suggest that biased processing of positive information might also be an important aspect of developing psychopathological symptoms. However, despite some evidence suggesting persons with symptoms of depression and anxiety may avoid positive information, many dot-probe studies have produced null findings. The present review used conventional and novel meta-analytic methods to evaluate dot-probe attentional biases away from positive information and, for comparison, toward negative information, in depressed and anxious individuals. Results indicated that avoidance of positive information is a real effect exhibiting substantial evidential value among persons experiencing psychopathology, with individuals evidencing primary symptoms of depression clearly demonstrating this effect. Different theoretical explanations for these findings are evaluated, including those positing threat-processing structures, even-handedness, self-regulation, and reward devaluation, with the novel theory of reward devaluation emphasized and expanded. These novel findings and theory suggest that avoidance of prospective reward helps to explain the cause and sustainability of depressed states. Suggestions for future research and methodological advances are discussed.

Experimental pain impairs recognition memory irrespective of pain predictability

BACKGROUND

Pain is hardwired to signal threat and tissue damage and therefore automatically attracts attention to initiate withdrawal or defensive behaviour. This well-known interruptive function of pain interferes with cognitive functioning and is modulated by bottom-up and top-down variables. Here, we applied predictable or unpredictable painful heat stimuli simultaneously to the presentation of neutral images to investigate (I) whether the predictability of pain modulated its effect on the encoding of images (episodic memory) and (II) whether subjects remember that certain images have been previously presented with pain (source memory).

METHODS

Twenty-four healthy subjects performed a categorization task in which 80 images had to be categorized into living or non-living objects. We compared the processing and encoding of these images during cued and non-cued pain trials as well as cued and non-cued pain-free trials. Effects on recognition performance and source memory for pain were immediately tested using a surprise recognition task.

RESULTS

Painful thermal stimulation impaired recognition accuracy (d', recollection, familiarity). This negative effect of pain was positively correlated with the individual expectation of pain interference and the attentional avoidance of pain-related words. However, the interruptive effect of pain was not modulated by the predictability of pain. Source memory for painful stimulation was at chance level, indicating that subjects did not explicitly remember that images had been paired with pain.

CONCLUSIONS

Targeting negative expectations and a maladaptive attentional bias for pain-related material might help reducing frequently reported pain-induced cognitive impairments.

Association of genetic and psychological factors with persistent pain after cosmetic thoracic surgery

The genetic control of pain has been repeatedly demonstrated in human association studies. In the present study, we assessed the relative contribution of 16 single nucleotide polymorphisms in pain-related genes, such as cathechol-O-methyl transferase gene (COMT), fatty acid amino hydrolase gene (FAAH), transient receptor potential cation channel, subfamily V, member 1 gene (TRPV1), and δ-opioid receptor gene (OPRD1), for postsurgical pain chronification. Ninety preoperatively pain-free male patients were assigned to good or poor outcome groups according to their intensity or disability score assessed at 1 week, 3 months, 6 months, and 1 year after funnel chest correction. The genetic effects were compared with those of two psychological predictors, the attentional bias toward positive words (dot-probe task) and the self-reported pain vigilance (Pain Vigilance and Awareness Questionnaire [PVAQ]), which were already shown to be the best predictors for pain intensity and disability at 6 months after surgery in the same sample, respectively. Cox regression analyses revealed no significant effects of any of the genetic predictors up to the end point of survival time at 1 year after surgery. Adding the genetics to the prediction by the attentional bias to positive words for pain intensity and the PVAQ for pain disability, again no significant additional explanation could be gained by the genetic predictors. In contrast, the preoperative PVAQ score was also, in the present enlarged sample, a meaningful predictor for lasting pain disability after surgery. Effect size measures suggested some genetic variables, for example, the polymorphism rs1800587G>A in the interleukin 1 alpha gene (IL1A) and the COMT haplotype rs4646312T>C/rs165722T>C/rs6269A>G/rs4633T>C/rs4818C>G/rs4680A>G, as possible relevant modulators of long-term postsurgical pain outcome. A comparison between pathophysiologically different predictor groups appears to be helpful in identifying clinically relevant predictors of chronic pain.