A passion of the soul: an introduction to pain for consciousness researchers

Association of low-dose naltrexone and transcranial direct current stimulation in fibromyalgia: a randomized, double-blinded, parallel clinical trial

INTRODUCTION

Fibromyalgia is a complex, generalized, and diffuse chronic musculoskeletal pain. Pharmacological approaches are widely used to relieve pain and increase quality of life. Low-Dose Naltrexone (LDN) was shown to increase the nociceptive threshold in patients with fibromyalgia. Transcranial Direct Current Stimulation (tDCS) is effective for pain management.

OBJECTIVE

The purpose of this study was to evaluate the analgesic and neuromodulatory effects of a combination of LDN and tDCS in patients with fibromyalgia.

METHODS

This was a randomized, double-blinded, parallel, placebo/sham-controlled trial (NCT04502251; RBR-7HK8N) in which 86 women with fibromyalgia were included, and written informed consent was obtained from them. The patients were allocated into four groups: LDN + tDCS (n = 21), LDN + tDCS Sham (n = 22), placebo + tDCS (n = 22), and placebo+tDCS Sham (n = 21). The LDN or placebo (p.o.) intervention lasted 26 days; in the last five sessions, tDCS was applied (sham or active, 20 min, 2 mA). The following categories were assessed: sociodemographic, Visual Analog Pain Scale (VAS), Pain Catastrophizing Scale (PCS), State-Trait Anxiety Inventory (STAI), Fibromyalgia Impact Questionnaire (FIQ), Beck Depression Inventory (BDI-II), Profile of Chronic Pain Scale (PCP:S), Pain Pressure Threshold (PPT), and Conditioned Pain Modulation (CPM). Blood samples were collected to analyze BDNF serum levels.

RESULTS

At baseline, no significant difference was found regarding all measurements. VAS pain was significantly reduced in the LDN + tDCS (p = 0.010), LDN + tDCS Sham (p = 0.001), and placebo+tDCS Sham (p = 0.009) groups. In the PCP:S, the LDN+tDCS group showed reduced pain frequency and intensity (p = 0.001), effect of pain on activities (p = 0.014) and emotions (p = 0.008). Depressive symptoms reduced after all active interventions (p > 0.001).

CONCLUSION

Combined LDN+tDCS has possible benefits in reducing pain frequency and intensity; however, a placebo effect was observed in pain using VAS, and further studies should be performed to analyze the possible association.

A digital intervention using virtual reality helmets to reduce dental anxiety of children under local anesthesia and primary teeth extraction: A randomized clinical trial

INTRODUCTION

Behavior management of children during dental treatment is an important but challenging issue. As a new technique, VR has been applied in pediatric dental anxiety. But there is no final conclusion whether VR reduces children's dental anxiety.

METHODS

The aim of the study is to assess the effectiveness of a digital intervention using virtual reality (VR) helmets on dental anxiety, pain perception, and behavior triggered for children, as well as occurrence of simulator sickness in local anesthesia and primary teeth extraction. A total of 128 children, who needed primary teeth extraction under local anesthesia, were randomly allocated into two groups: use VR helmets and traditional behavior guidance procedures (control). Modified Child Fear Survey Schedule Dental Subscale (CFSS-DS), Wong-Baker FACES Pain Scale, Houpt Scale, and Simulator sickness questionnaire (SSQ) were used to assess children's dental anxiety, pain perception, and behavior triggered and occurrence of simulator sickness.

RESULTS

CFSS-DS score in the VR group was significantly decreased after dental treatment (34.58±6.90 before operation and 32.32±15.58 after operation, p = .02). The score of Wong Baker Scale in the VR group (3.47±0.76) was significantly lower than that in the control group (5.56±1.13, p = .015). There was no significant difference in the Houpt Behavior Scale score and the SSQ score between the VR group and the control group (p = .35, p = .305).

CONCLUSION

The use of VR helmets in primary teeth extraction can significantly reduce dental anxiety and pain perception in children without occurrence of simulator sickness.

The Influence of the Locus of Control Construct on the Efficacy of Physiotherapy Treatments in Patients with Chronic Pain: A Systematic Review

The biopsychosocial paradigm contemplates the patient's personality traits in physiotherapy treatments for chronic pain. Among these traits, the locus of control has a direct relationship with the person's coping strategies in the face of their health problems. The objective of this systematic review was to assess the influence of locus of control on the efficacy of physiotherapy treatments in patients with chronic pain. A systematic review of the publications of the last ten years in Pubmed, Scopus, Science Direct and Web of Science databases was conducting with the terms physical therapy modalities, chronic pain, internal-external control, self-management, physical therapy and physiotherapy. The inclusion criteria were participants with chronic pain lasting at least three months who have received at least one session of physical therapy; the studies should have collected the patient's locus of control as a prognostic factor at the beginning of physiotherapy treatment; the variables studied should include the pain intensity or clinical variables related to pain. A total of 13 articles were found, of which three were experimental studies and ten were observational studies. The included samples had chronic knee pain, nonspecific back pain, low back pain or neck pain; were people over 65 years of age or patients who had undergone hand surgery. In patients with chronic pain for more than three months, the locus of control construct participates as a predictor of the results of physiotherapy treatment. The presence of an internal locus of control favors better results. The personality traits of the subjects represent an important factor to take into account when planning physiotherapy treatments.

The effects of transcutaneous electrical nerve stimulation during the first stage of labor: a randomized controlled trial

BACKGROUND

Labor pain during childbirth can have devastating effects on the progress of labor, mother, and fetus. Consequently, the management of labor pain is crucial for the well-being of the mother and fetus. Transcutaneous electrical nerve stimulation (TENS) is a non -pharmacological analgesic technique. It uses a low-voltage electrical current to activate descending inhibitory systems in the central nervous system to relieve pain. This study aimed to determine the effects of TENS therapy in the first stage of labor.

METHODS

In this single-blind randomized controlled trial, we screened low-risk pregnant women who anticipated spontaneous vaginal delivery. Women were assigned (1:1) to either the experimental group (received TENS therapy in the first stage of labor) or the control group (received routine obstetric care). The women, midwives, and researchers working in the gynecology and obstetric department were aware of the treatment group, but statisticians analysis the data were blinded. The primary outcome was labor pain intensity, assessed by visual analog scale (VAS) immediately after the randomization, at 30, 60, and 120 min after TENS therapy, and 2-24 h post-delivery. We used SPSS 21.0 software in data analysis. An independent sample t-test compared the mean VAS scores and labor duration between groups. A Chi-square test was employed to compare categorical variables between the groups. A significant level of ≤0.05 was statistically significant.

RESULTS

A total of 326 pregnant women were eligible: experimental group (n = 161) and control group (n = 165). The experimental group had statistically significantly lower mean VAS scores at a different time (30, 60, and 120 min post-intervention and 2-24 h post-delivery) than the control group (p < 0.001). The experimental group demonstrated a statistically significant shorter duration of the active labor phase than the control group (p < 0.001).

CONCLUSION

This study indicates that TENS can be used as a non-pharmacological therapy to reduce pain and shorten the active labor phase.

TRIAL REGISTRATION

ISRCTN registry, ISRCTN23857995 . Registered on 11/12/2020, 'retrospectively registered.

Functional human brain connectivity during labor and its alteration under epidural analgesia

This study used functional magnetic resonance imaging to explore the neural networks of pain during labor and its relief. It was hypothesized that epidural analgesia would affect the neural activities and the underlying network connectivity. Analysis using dynamic causal modelling and functional connectivity was performed to investigate the spatial activity and network connection of labor pain with and without epidural analgesia. This Institutional Review Board approved study acquired Magnetic Resonance Imaging from 15 healthy women of spontaneous normal delivery (with/without epidural analgesia = 7/8, aged 29.6 ± 2.3 and 29.3 ± 4.8 years old respectively) using a 1.5 Tesla scanner. Numerical rating score of pain was evaluated by a research nurse in the beginning of the first stage of labor and approximately 30 min after imaging examination. Six regions of interested from the activated clusters and literature were selected for dynamic causal modelling, which included primary and secondary somatosensory cortex, middle frontal gyrus, anterior cingulate cortex, insula and lentiform. Functional connectivity was calculated from selected sensory and affective regions. All analyses were performed by using software of statistical parametric mapping version 8 and CONN functional connectivity toolbox. The result showed that the experience of labor pain can lead to activations within a distributed brain network. The pain relief from epidural analgesia can be accompanied with altered functional connectivity, which was most evident in the cingulo-frontal system. The present study, therefore, provides an overview of a pain-related neural network that occur during labor and upon epidural analgesia.

Pain Management in the Cancer Survivor

OBJECTIVES

To describe assessment and interdisciplinary management of pain in the cancer survivor over the continuum of cancer care.

DATA SOURCES

Review of the literature and treatment standards.

CONCLUSION

Pain remains a primary concern throughout the cancer trajectory across all age groups and diagnoses, emphasizing the need to integrate pain assessment and management across the continuum of cancer survivorship and across care settings. Types of pain, pain patterns, assessment of cancer pain in cancer survivors, current strategies and challenges for management, and effective communication and documentation of the process are described. Communication between and among health care clinicians in a way that effectively articulates the individual patient experience, including documentation in the electronic medical record, requires consistent workflows and terminology. The opioid crisis increases the urgency in effective strategies for interdisciplinary pain assessment and management.

IMPLICATIONS FOR NURSING PRACTICE

Oncology clinicians must be able to adequately assess pain, track pain over time, understand and implement a cadre of strategies to manage pain, and effectively pursue any suspicious pain patterns that may indicate recurrence or progression of cancer or other underlying etiologies. The oncology nurse is at the core of patient-clinician communication, critical to effectively describing pain as experienced by the individual patient and continues to play a key role in maintaining consistency of message that is necessary to manage pain over the continuum of cancer survivorship.

Labour pain perception: experiences of Nigerian mothers

Introduction

Labour pain perception is influenced by a variety of factors; hence women experience and cope with labour pain differently. This study was designed to assess labour pain perception among parturient.

Methods

A cross-sectional study involving 132 pregnant women who had vaginal delivery at two tertiary hospitals in south west Nigeria. A structured questionnaire was administered to women within 24 hours of delivery to record details of labour and delivery. Labour pain perception was assessed using the Visual Analogue Score (VAS). Data analysis were done using IBM-SPSS Statistics for Windows version 21.0 (IBM Corp., Armonk, NY, USA).

Results

The mean age of the parturients was 30.6±4.8 years. The mean pain perception of the parturients as assessed by VAS was 7.0 with range of 1.2-10.0. Sixty-six (50%) parturients rated labour pain to be severe (VAS > 7.1). Majority of the respondents 114(86.4%) desired some form of pain relief. The Body Mass Index (BMI) of respondents and birth weight of their babies had statistically significant association with pain perception (p = 0.010; p = 0.038 respectively). Factors associated with increased odds of having severe pain perception include unbooked status, secondary level education, BMI < 30, and gestational age ≥ 37 weeks.

Conclusion

Women in south west Nigeria perceived labour pain as severe and many desired pain relief during labour. Occupation, BMI, gestational age and baby's birth weight were significant mediating variables in women's experience of labour pain. Modern methods of labour analgesia should be offered to parturients who express desire for it. This will lead to improvements women's childbirth experience.

Modulation of tactile perception by Virtual Reality distraction: The role of individual and VR-related factors

Background

Virtual reality (VR) has shown to be an effective distraction method in health care. However, questions remain regarding individual and VR-related factors that may modulate the effect of VR.

Purpose

To explore the effect of VR distraction on tactile perception thresholds in healthy volunteers, in relation to personal characteristics and interactivity of VR applications.

Methods

A randomized three way cross-over study was conducted to investigate the effects of active and passive VR applications in 50 healthy participants. Main outcome measures were monofilament detection thresholds (MDT) and electrical detection thresholds (EDT). Personal characteristics (e.g. age, gender, susceptibility for immersion) and immersion in the VR conditions were analyzed for their effect on VR induced threshold differences.

Results

The use of VR caused a significant increase in both MDT and EDT compared to the control condition (MDT: F (2, 76) = 20.174, p < 0.001; EDT F (2, 76) = 6.907, p = 0.002). Furthermore, a significant difference in favour of active VR compared to passive VR was found in MDT (p = 0.012), but not in EDT. No significant gender effect was found. There was a significant positive correlation between age and active VR distraction (r = 0.333, p = 0.018). Immersion in the VR world was positively correlated with the effect of VR, whereas visualization and daydreaming were negatively correlated with VR effects.

Conclusion

VR increased tactile perception thresholds, with active VR having the largest effect. Results indicate that the efficacy of VR may increase with increasing age. Gender did not affect VR susceptibility.

Subliminal (latent) processing of pain and its evolution to conscious awareness

By unconscious or covert processing of pain we refer to nascent interactions that affect the eventual deliverance of pain awareness. Thus, internal processes (viz., repeated nociceptive events, inflammatory kindling, reorganization of brain networks, genetic) or external processes (viz., environment, socioeconomic levels, modulation of epigenetic status) contribute to enhancing or inhibiting the presentation of pain awareness. Here we put forward the notion that for many patients, ongoing sub-conscious changes in brain function are significant players in the eventual manifestation of chronic pain. In this review, we provide clinical examples of nascent or what we term pre-pain processes and the neurobiological mechanisms of how these changes may contribute to pain, but also potential opportunities to define the process for early therapeutic interventions.

2017 update on pain management in patients with chronic kidney disease

The prevalence of pain has been reported to be >60-70% among patients with advanced and end-stage kidney disease. Although the underlying etiologies of pain may vary, pain per se has been linked to lower quality of life and depression. The latter is of great concern given its known association with reduced survival among patients with end-stage kidney disease. We herein discuss and update the management of pain in patients with chronic kidney disease with and without requirement for renal replacement therapy with the focus on optimizing pain control while minimizing therapy-induced complications.

Norepinephrine and dopamine transmission in 2 limbic regions differentially respond to acute noxious stimulation

Central dopamine and norepinephrine regulate behavioral and physiological responses during rewarding and aversive stimuli. Here, we investigated and compared norepinephrine and dopamine transmission in 2 limbic structures, the ventral bed nucleus of the stria terminalis and the nucleus accumbens shell of anesthetized rats, respectively, in response to acute tail pinch, a noxious stimulus. Norepinephrine release in the ventral bed nucleus of the stria terminalis responded monophasically, increasing at the time of the tail pinch and remaining elevated for a period after its cessation. In contrast, dopamine transmission in the nucleus accumbens shell displayed a heterogeneous and time-locked response to tail pinch. For most trials, there was a suppression of extracellular dopamine concentration throughout the duration of the stimuli. At the termination of the stimuli, however, extracellular dopamine either recovered back to or spiked above the initial baseline concentration. These signaling patterns were more clearly observed after administration of selective catecholamine autoreceptor and transporter inhibitors. The results suggest that the opposing responses of these catecholamines can provide integration of noxious inputs to influence behavioral outputs appropriate for survival such as escape or fighting.

Symptoms of PTSD Associated With Painful and Nonpainful Vicarious Reactivity Following Amputation

Although the experience of vicarious sensations when observing another in pain have been described postamputation, the underlying mechanisms are unknown. We investigated whether vicarious sensations are related to posttraumatic stress disorder (PTSD) symptoms and chronic pain. In Study 1, 236 amputees completed questionnaires about phantom limb phenomena and vicarious sensations to both innocuous and painful sensory experiences of others. There was a 10.2% incidence of vicarious sensations, which was significantly more prevalent in amputees reporting PTSD-like experiences, particularly increased arousal and reexperiencing the event that led to amputation (φ = .16). In Study 2, 63 amputees completed the Empathy for Pain Scale and PTSD Checklist-Civilian Version. Cluster analyses revealed 3 groups: 1 group did not experience vicarious pain or PTSD symptoms, and 2 groups were vicarious pain responders, but only 1 had increased PTSD symptoms. Only the latter group showed increased chronic pain severity compared with the nonresponder group (p = .025) with a moderate effect size (r = .35). The findings from both studies implicated an overlap, but also divergence, between PTSD symptoms and vicarious pain reactivity postamputation. Maladaptive mechanisms implicated in severe chronic pain and physical reactivity posttrauma may increase the incidence of vicarious reactivity to the pain of others.

The biological function of consciousness

This research is an investigation of whether consciousness-one's ongoing experience-influences one's behavior and, if so, how. Analysis of the components, structure, properties, and temporal sequences of consciousness has established that, (1) contrary to one's intuitive understanding, consciousness does not have an active, executive role in determining behavior; (2) consciousness does have a biological function; and (3) consciousness is solely information in various forms. Consciousness is associated with a flexible response mechanism (FRM) for decision-making, planning, and generally responding in nonautomatic ways. The FRM generates responses by manipulating information and, to function effectively, its data input must be restricted to task-relevant information. The properties of consciousness correspond to the various input requirements of the FRM; and when important information is missing from consciousness, functions of the FRM are adversely affected; both of which indicate that consciousness is the input data to the FRM. Qualitative and quantitative information (shape, size, location, etc.) are incorporated into the input data by a qualia array of colors, sounds, and so on, which makes the input conscious. This view of the biological function of consciousness provides an explanation why we have experiences; why we have emotional and other feelings, and why their loss is associated with poor decision-making; why blindsight patients do not spontaneously initiate responses to events in their blind field; why counter-habitual actions are only possible when the intended action is in mind; and the reason for inattentional blindness.

Tamper-resistant opioid formulations in the treatment of acute pain

INTRODUCTION

Pain-including acute or persistent acute pain-is a common condition that is increasingly being treated with opioids in the United States. The acute pain treatment setting may represent a key target for addressing the growing epidemic of prescription drug abuse occurring hand in hand with the rise in opioid prescribing. Balancing the needs of pain treatment with abuse prevention can be challenging for clinicians.

METHODS

This article identified efforts to balance opioid abuse risks with opioid availability through the extensive experience of the author in this field. In addition, PubMed literature searches using terms such as "prescription opioid abuse", "abuse-deterrent opioids", and "tamper-resistant opioids"; and inspection of the bibliographies of relevant articles were used to identify relevant sources.

RESULTS

These multifaceted efforts have included: improving assessment of patient risk for drug misuse, abuse, or diversion; funding of and encouraging referral to addiction treatment programs; access to and widespread use of prescription monitoring programs (PMPs); public knowledge of prescription opioid abuse; proper storage of opioid medications; and development of new formulations designed to resist tampering and deter abuse. This review discusses the problem of prescription opioid abuse and strategies to minimize risk within the context of acute pain treatment, and explores the potential role of tamper-resistant opioid formulations and other abuse deterrence strategies in the area of acute or persistent acute pain management.

CONCLUSION

In order to stem the tide of prescription opioid abuse and preserve the availability of opioids as a much needed analgesic option, a multifaceted approach that includes tamper-resistant opioid formulations-for chronic or acute pain-along with strategies such as improved patient risk assessment, funding for and referral to addiction treatment programs, greater use of PMPs, and raised awareness of prescription opioid abuse is needed.

Effects of hypnotic analgesia and virtual reality on the reduction of experimental pain among high and low hypnotizables

This research compared a no-treatment control condition and 3 experimentally induced pain treatment conditions: (a) virtual reality distraction (VRD), (b) hypnotic analgesia (HA), and (c) HA + VRD in relieving finger-pressure pain. After receiving baseline pain stimulus, each participant received hypnosis or no hypnosis, followed by VRD or no VRD during another pain stimulus. The data analysis indicated that, overall, all 3 treatments were more effective compared to the control group, irrespective of whether it involved hypnotic analgesia, virtual reality distraction, or both (hypnosis and virtual reality). Nevertheless, the participants responded differently to the pain treatment, depending on the hypnotizability level. High hypnotizables reported hypnotic analgesia, but low hypnotizables did not show hypnotic analgesia. VR distraction reduced pain regardless of hypnotizability.

The impact of language on the expression and assessment of pain in children

This paper focuses on the importance of language in the expression of pain. Variation in definitions of pain is presented, together with a review of the evidence examining the impact language may have on the way pain is expressed linguistically. The implications for conducting research with children who speak different languages are explored. Strategies such as using non-linguistic methods of communication, additional time required for conducting interviews and the inclusion of research team members from the same ethnic or linguistic background are presented.

Interview: Reflections on pain research and management: past, present and future

C Richard Chapman is Professor and Director of the Pain Research Center in the department of Anesthesiology at the University of Utah, Salt Lake City (UT, USA). A psychologist and psychophysiologist, he has worked in the pain research field since 1970. He spent 29 years at the University of Washington before coming to the University of Utah. His interests span acute pain, chronic pain, cancer pain and pain measurement.

Virtual Reality Helmet Display Quality Influences the Magnitude of Virtual Reality Analgesia

Immersive Virtual Reality (VR) distraction can be used in addition to traditional opioids to reduce procedural pain. The current study explored whether a High-Tech-VR helmet (ie, a 60-degree field-of-view head-mounted display) reduces pain more effectively than a Low-Tech-VR helmet (a 35-degree field-of-view head-mounted display). Using a double-blind between-groups design, 77 healthy volunteers (no patients) aged 18-23 were randomly assigned to 1 of 3 groups. Each subject received a brief baseline thermal pain stimulus, and the same stimulus again minutes later while in SnowWorld using a Low-Tech-VR helmet (Group 1), using a High-Tech-VR helmet (Group 2), or receiving no distraction (Group 3, control group). Each participant provided subjective 0-10 ratings of cognitive, sensory, and affective components of pain, and amount of fun during the pain stimulus. Compared to the Low-Tech-VR helmet group, subjects in the High-Tech-VR helmet group reported 34% more reduction in worst pain (P < .05), 46% more reduction in pain unpleasantness (P = .001), 29% more reduction in "time spent thinking about pain" (P < .05), and 32% more fun during the pain stimulus in VR (P < .05). Only 29% of participants in the Low-Tech helmet group, as opposed to 65% of participants in the High-Tech-VR helmet group, showed a clinically significant reduction in pain intensity during virtual reality. These results highlight the importance of using an appropriately designed VR helmet to achieve effective VR analgesia (see ).

PERSPECTIVE

Pain during medical procedures (eg, burn wound care) is often excessive. Adjunctive virtual reality distraction can substantially reduce procedural pain. The results of the present study show that a higher quality VR helmet was more effective at reducing pain than a lower quality VR helmet.

Evaluating chronic pain impact among patients in primary care: further validation of a brief assessment instrument

OBJECTIVE

To evaluate the psychometric properties of the Profile of Chronic Pain: Screen (PCP:S) in primary care. The PCP:S is a brief assessment device designed to gauge pain severity, interference, and emotional burden.

DESIGN

Questionnaire survey with short-term reliability and validity follow-up.

METHODS

Two hundred and forty-four outpatients (52% female) with chronic pain recruited from five primary care settings completed the 15-item PCP:S at an initial testing session. Approximately 1 week later, two subgroups participated in a retest reliability and validity follow-up. The battery of follow-up questionnaires included a measure of social desirability response bias and several instruments designed to provide convergent validity for the PCP:S.

RESULTS

Retest reliability, internal consistency, factor structure, and social desirability bias were all found to be acceptable. Likewise, preliminary evidence suggests that, by virtue of its correlation with established measures of pain adjustment, the PCP:S is a valid pain assessment device.

CONCLUSIONS

Although the PCP:S was initially developed and validated using a national community sample of adults with chronic pain who provided data via telephone interviews, the present findings support its use as a brief and psychometrically sound paper-and-pencil measure for the assessment of three key components of chronic pain in primary care.

Establishing an emergency department pain management system

Any ED system for the management of pain in the ED should consider the following: assessment of pain including mandatory use of some assessment tool, a guideline for treatment of pain, communication with other members of the health care team, assessment tools, program monitoring, and a continuous quality assurance program. The treatment guideline should consider acute versus chronic pain, potential medication tolerance, concurrent anxiety and psychiatric issues, special populations, and disease-specific conditions.

The development and preliminary validation of a brief measure of chronic pain impact for use in the general population

From a biopsychosocial perspective, assessing chronic pain's psychological impact should involve at minimum the measurement of pain severity, functional interference, and pain-related emotional burden. This article details the development of a brief instrument, the 15-item Profile of Chronic Pain: Screen (PCP:S), designed to address these three key elements in a national (US) sample of over 2400 individuals recruited via random digit dialing. Retest reliability, internal consistency, and preliminary validity were excellent. The scales also demonstrated minimal social desirability response bias. A series of confirmatory factor analyses on several distinct samples revealed a stable, 3-factor solution reflecting pain severity, interference, and emotional burden. Finally, national norms were developed by gender and three age groups. In view of its strong psychometric properties, the PCP:S has the potential to serve as a brief, cost-effective assessment tool for identifying individuals whose chronic pain merits more detailed psychosocial evaluation.

What does pain signify? A hypothesis concerning pain, the immune system and unconscious pain experience under general anesthesia

In this paper, I present a case-study that initiates a discussion about the meaning of pain. The case-study concerns a person who was under deep sedation during colonoscopy. The person did not experience pain from a first-person perspective, although pain was evident to the medical team from a second-person perspective. The divergence of pain perspectives raises an interesting quandary. If the body communicates pain while pain consciousness is blocked by the sedation procedure, our conclusion should be that the intersubjective aspect of pain precedes the "subjective," first-person experience of pain. This conclusion is not consistent with the common representational conception of pain that places the intrasubjective point of view prior to the intersubjective point of view. The solution I offer to this quandary is the quasi-paradoxical idea that pain can be experienced unconsciously through the immune system. Following this suggestion, I hypothesize that post-traumatic stress disorders following general anesthesia may result from this unconscious pain experience. If this idea is scientifically grounded, then physicians should: (1) consider ways of blocking the unconscious pain experience produced by the immune system without interfering with the immune response, and (2) study pain as a complex cognitive and unconscious system by drawing an analogy with the immune system, which follows similar logic.

Manipulating presence influences the magnitude of virtual reality analgesia

Excessive pain during medical procedures performed in unanesthetized patients is frequently reported, but can be reduced with virtual reality (VR) distraction. Increasing the person's illusion of going into the virtual world may increase how effectively VR distracts pain. Healthy volunteers aged 18-20 years participated in a double-blind between-groups design. Each subject received a brief baseline thermal pain stimulus, and the same stimulus again minutes later with either a Low Tech or a High Tech VR distraction. Each subject provided subjective 0-10 ratings of cognitive, sensory and affective components of pain, and rated their illusion of going inside the virtual world. Subjects in the High Tech VR group reported a stronger illusion of going into the virtual world (VR presence) than subjects in the Low Tech VR group, (4.2 vs. 2.5, respectively, P = 0.009) and more pain reduction (reduction of worst pain is 3.1 for High Tech VR vs. 0.7 for Low Tech VR, P < 0.001). Across groups, the amount of pain reduction was positively and significantly correlated with VR presence levels reported by subjects ( r = 0.48 for 'worst pain', P < 0.005).

Defining the therapeutic role of local anesthetic sympathetic blockade in complex regional pain syndrome: a narrative and systematic review

OBJECTIVE

There is growing controversy on the value of blocking the sympathetic nervous system for the treatment of complex regional pain syndromes (CRPS). The authors sought to evaluate the efficacy of sympathetic blockade with local anesthetic in these syndromes. In addition, they performed a comprehensive review of the pathophysiology and other treatments for CRPS.

DESIGN

Systematic review of the literature was performed. MEDLINE was searched from 1966 through 1999. The authors identified only three randomized controlled trials (RCTs) that evaluated sympathetic blockade with local anesthetic, but because of differences in study design they were unable to pool the study data. The authors therefore included nonrandomized studies and case series.

INTERVENTIONS

Studies were included if local anesthetic sympathetic blockade was used in at least 10 patients. Studies were excluded if continuous infusion techniques, somatic nerve blocks, or combined sympatholytic therapies were evaluated.

OUTCOME MEASURES

Pain relief was classified as full, partial, or absent. The lack of a comparison group in the studies allowed only the calculation of distribution of the response categories, and the sum of the pooled rates does not equal 100%.

RESULTS

Twenty-nine studies were included that evaluated 1,144 patients. Nineteen studies were retrospective, 5 prospective case series, 3 RCTs, and 2 nonrandomized controlled studies. The quality of the publications was generally poor. Twenty-nine percent of patients had full response, 41% had partial response, and 32% had absent response. It was not possible to estimate the duration of pain relief.

CONCLUSIONS

This review raises questions as to the efficacy of local anesthetic sympathetic blockade as treatment of CRPS. Its efficacy is based mainly on case series. Less than one third of patients obtained full pain relief. The absence of control groups in case series leads to an overestimation of the treatment response that can explain the findings.

A theoretical framework for understanding self-report and observational measures of pain: a communications model

Self-report and observational measures of pain are examined from the perspective of a model of human communication. This model examines the experience of pain as affected by intrapersonal and contextual factors, the process whereby it is encoded into expressive behaviour, and the process of decoding by observers prior to their engaging in action. Self-report measures primarily capture expressive pain behaviour that is under the control of higher mental processes, whereas observational measures capture behaviour that is less subject to voluntary control and more automatic. Automatic expressive behaviours are subject to less purposeful distortion than are behaviours dependent upon higher mental processes. Consequently, observational measures can be used and have clinical utility as indices of pain when self-report is not available, for example, in infants, young children, people with intellectual disabilities or brain damage, and seniors with dementia. These measures are also useful when the credibility of self-report is questioned and even when credible self-report is available. However, automatic behaviours may be more difficult for observers to decode. The model outlined herein takes into account the role of various human developmental stages in pain experience and expression and in understanding the utility of self-report and observational measures. We conclude that both observational and self-report measures are essential in the assessment of pain because of the unique information that each type contributes.