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PubMed2006

The influence of discordance in pain assessment on the functional status of patients with chronic nonmalignant pain.

BACKGROUND: Chronic pain is a frequent cause of suffering and disability that seriously affects patients' quality of life and imposes a staggering socioeconomic toll on society. Little is known about the impact of patient-physician disagreement (discordance) regarding the assessment of chronic pain on patients' quality of life in primary care settings. This study evaluates the role of discordance and other potentially modifiable factors that affect the quality of life and functional status of chronic pain patients. METHODS: We evaluated 436 patient-physician encounters at 12 academic medical centers in the United States. We surveyed chronic nonmalignant pain patients to understand their pain perceptions. We concurrently surveyed their physicians about their perceptions of their patient's pain in primary care settings. RESULTS: More than 50% of physicians disagreed with their patient's pain. Thirty-nine percent of primary care physicians underestimated their patient's pain. In the multivariate analysis, this discordance was associated with poor physical functioning and worse bodily pain (P < 0.018 and P < 0.001 respectively). Patients with chronic, nonmalignant pain have reductions in physical function and bodily pain domains of the SF-36 compared to age-matched populations. Depression and obesity represented other associations. CONCLUSION: Patients with chronic nonmalignant pain have poor physical functioning and worse bodily pain. Discordance, obesity, and depression are other modifiable factors. Prospective studies are needed to design interventions. However, a multifaceted approach appears to represent the best opportunity to reduce the pain and suffering of this challenging population.

Chronic Disease↗
PubMed1997

Experimental pain in the stomach: a model based on electrical stimulation guided by gastroscopy.

BACKGROUND: Abdominal pain is often variable in intensity and difficult to characterise due to its referred pain pattern. Clinical pain is furthermore confounded by various emotional and cognitive factors. AIMS: To develop and apply an experimental model to induce localised gastric pain. SUBJECTS: Twelve healthy male volunteers. METHODS: Stimulating electrodes were mounted on a biopsy forceps and electric stimuli were delivered during gastroscopy. Single, five repeated, and continuous stimuli were given at four locations in the stomach. Pain detection thresholds and pain intensities were assessed together with localisation of the referred pain area. RESULTS: Pain detection thresholds were higher in the prepyloric region compared with those obtained at the lesser and greater curvature. Increasing stimulus intensity resulted in augmented pain perception and repeated stimuli elicited pain at a lower stimulus intensity than single stimuli. Continuous stimuli evoked constant (33%), increasing (33%), or decreasing (33%) pain. The localisation of referred pain varied considerably in the subjects. CONCLUSIONS: The model seems relevant to study basic pain mechanisms elicited by localised stimuli in the stomach. The experimental data support the premise that a gastric focus should always be suspected in patients referred with different kinds of abdominal pain.

Abdominal Pain↗
PubMed1997

Blood pressure and metabolic factors in relation to chronic pain.

Physical pain is a major trigger for changes in many homeostatic systems of the body physiology. Our aim was to study the relationship between blood pressure, metabolism and pain perception in subjects with chronic pain symptoms. This was undertaken in a population-based study in primary health care, including subjects with widespread pain (n = 16), or localized pain (n = 15), and pain-free controls (n = 14). The main outcome measures were office and ambulatory blood pressure, glucose, insulin, lipids, and beta-endorphin. Subjects with widespread pain were more obese and showed higher levels than controls (p < 0.05) of fasting glucose (4.9 vs 4.5 mmol/l), cholesterol (6.9 vs 5.8 mmol/l) and office systolic blood pressure (133 vs 120 mmHg), while the subjects reporting localized pain had values in-between. Ambulatory blood pressure, insulin and beta-endorphin levels did not differ between the groups. In conclusion, subjects with widespread and/or intense chronic pain have higher BMI, more pronounced metabolic disturbances and higher (office) systolic blood pressure, but not ambulatory blood pressure, than subjects without chronic pain. Future epidemiological studies are needed to test whether this is compatible with increased cardiovascular risk.

Adult↗
PubMed1990

Argon laser induced cutaneous sensory and pain thresholds in post-herpetic neuralgia. Quantitative modulation by topical capsaicin.

Sensory and pain thresholds to cutaneous argon laser stimulation were determined in patients with post-herpetic neuralgia before and during treatment with topical capsaicin. Before treatment both thresholds were significantly elevated on the affected side compared to the contralateral normal area. After one week of capsaicin treatment both thresholds were significantly increased compared to the pre-treatment values, and the subjective pain relief, measured on a visual analogue scale (VAS) was 24%. More than 10% decrease in VAS pain score was obtained by 62.5% of the patients. Laser stimulations at levels at which the sensory and pain thresholds are reached were initially described as burning or stinging with pain projecting outside the stimulated area. This allodynia to laser stimulations changed during capsaicin treatment towards normal sensory and pain perception qualities. Both sensory and pain thresholds and the subjective pain score evaluated on a visual analogue scale were attenuated during the capsaicin treatment, suggesting a significant role of the cutaneous sensory and pain receptors in postherpetic neuralgia.

Administration, Topical↗
PubMed1987

[Pathophysiology of painful and silent myocardial ischemia].

Regardless of the factor assumed responsible for precipitation of myocardial ischemia - varying from coronary occlusion in acute myocardial infarction to increased oxygen demand in exertional angina pectoris and reduced myocardial oxygen supply due to plaque rupture or changes in vasomotor tone in unstable angina - its incurrence may or may not be associated with pain. In the vast majority of cases, silent myocardial ischemia is observed in patients with established symptomatic coronary artery disease. Interindividual comparisons have not enabled reliable differentiation between those with painful and those with silent ischemia based on the anatomic extent of coronary artery disease, left ventricular function or previous myocardial infarction. Similarly, functional parameters such as exercise capacity, exercise duration, time to onset of ST-segment depression during exercise as well as heart rate and blood pressure both at rest and during exercise have failed to reveal differences between the symptomatic and the asymptomatic patients. Intraindividual differences have also been noted, but not consistently corroborated, and postulated as responsible for the fact that ischemia in a given patient alternates in its presence with and without pain. Since most patients with silent ischemia either have, or at some time in the past have experienced, painful ischemia, the integrity of the appropriate nervous system function can be assumed to be intact and neurocardiologic factors seem most likely to account for apparent discrepancies in pain perception. Prior to precipitation of pain, myocardial ischemia must elicit an adequate stimulus. According to some investigators, the adequate stimulus is that associated with a duration of the ischemic episode of at least three minutes and with increase in left ventricular filling pressure of more than 7 mm Hg. This threshold, consequently, represents a prerequisite but not invariably sufficient criteria for the occurrence of pain. The next step in the sequence of pain is generation of an action potential, that is, transduction by means of chemical or mechanical stimuli. During this process, a latency of 20 to 40 seconds is incurred such that the appearance of pain usually has its onset after derangement of relaxation and contraction, increased filling pressure and the observation of ECG changes. Through conduction, the information is forwarded to the central nervous system after coding of the details with regard to intensity. The intensity, in turn, is determined by the number of receptors (free nerve endings) in the field activated by the ischemic event.(ABSTRACT TRUNCATED AT 400 WORDS)

Angina Pectoris↗
PubMed1997

Bacterial lipopolysaccharides induce peripheral nerve disturbances in rats that mimic human immune-mediated polyneuropathies.

A single injection of Escherichia coli lipopolysaccharide (LPS; i.v. and i.p.) reliably induced peripheral nerve disturbances in male Australian albino Wistar (AaW) rats. Signs developed 6 to 24 h after LPS inoculation and persisted only transiently. Most AaW rats had variable degrees of bilateral hind limb impairment, and rarely had forelimb, tail, or central impairment. Signs included gait abnormalities, proprioceptive loss, and to a lesser extent hind limb weakness and sensory deficits. Signs were more severe in male than female AaW rats and were induced in a number of genetically related rat strains (e.g., AaW and outbred Wistar and inbred Lewis rats, but not Sprague Dawley or inbred Fischer 344 rats). Development and severity of these signs were found not be related to animal body weight, but were dependent on LPS dose. Signs were not associated with LPS-induced alterations in pain perception, or occurrence of spontaneous pain, as indexed by tail-flick and hot-plate tests. Taken together, these data indicate that LPS induced transient peripheral nerve disturbances in rats, the severity of which was influenced by genetic, sex-related, and dose-related factors.

Animals↗
PubMed1987

Tricyclic antidepressants in the treatment of cancer pain: a review.

The role of tricyclic antidepressants (TCAs) in the treatment of cancer pain is of growing interest. Various studies, all but one of them open, have suggested that TCAs are effective and safe in the treatment of pain caused by different types of cancer. The mechanisms of action by which TCAs decrease the pain perception are not fully clear. However, there are two main hypotheses. The first suggests that the drugs act primarily on the emotional component of pain, thus breaking the vicious circle of the perception of pain; the second suggests that the TCAs themselves have a specific analgesic action linked to a direct activity on the structures of the CNS. Further clinical studies, and in particular double-blind studies, are clearly necessary to provide more convincing and definitive results.

Analgesics↗
PubMed2000

The role of anticipation and fear of pain in the persistence of avoidance behavior in patients with chronic low back pain.

STUDY DESIGN: A correlative design using stepwise regression analysis. OBJECTIVE: To explore the variation in spinal isometric strength that can be accounted for by anticipation of pain, sensory perception of pain, functional disability belief, and the fear-avoidance belief in chronic low back pain patients. SUMMARY OF THE BACKGROUND DATA: Several biobehavioral factors contribute to the persistence of pain behavior in chronic patients. Recent studies suggest a need to explore the relation between reduced physical performance and the sensory and cognitive perception of pain. METHODS: Sixty-three patients with chronic low back pain 20 to 56 years of age participated in this study. Visual Analogs Scales, the Fear-Avoidance Belief questionnaire, and the Disability Belief questionnaire were used to measure the sensory and cognitive dimensions of pain. Spinal isometric strength was measured by the Medx lumbar extension machine. RESULTS: Analysis of variance and the stepwise regression analysis demonstrated that anticipation of pain and the fear-avoidance belief about physical activity significantly predicted variation in the spinal isometric strength deficit P < 0. 001. True pain experienced during the testing and answers to the Disability Belief questionnaire were not related. CONCLUSION: The results of this study strongly support the hypothesis that spinal physical capacity in chronicity is not explained solely by the sensory perception of pain. The anticipation of pain and the fear-avoidance belief about physical activities were the strongest predictors of the variation in physical performance.

Acute Disease↗
PubMed2000

Complete Freund's adjuvant-induced hyperalgesia: a human perception.

Much of our current understanding about chronic pain and the mechanisms of nociception has been derived from animal models (Bennett GJ. Animal models of neuropathic pain. In: Gebhart, GF, Hammond DL, Jensen TS, editors. Progress in pain research and management, vol. 2, Proceedings of the 7th World Congress of Pain. Seattle, WA: IASP Press, 1994. pp. 495-510; Dubner R, Methods of assessing pain in animals. In: Wall PD, Melzack R, editors. Textbook of pain, vol. 3. Edinburgh: Churchill Livingstone, 1994. pp. 293-302). It has been argued in some cases that animals do not perceive 'pain' as humans do, and thus extrapolation of the results of studies in animals is invalid. Clearly, the animal models used in the laboratory do not approach the complexity of chronic pain encountered in the clinical setting. Human pain perception is more complex since it encompasses lesion variability, as well as psychosocial, cultural, developmental, and environmental variables. Where parallels exist, it is possible to gain insight into certain aspects of human pain syndromes that are likely to lead to improved therapeutic opportunities for individual patients. One such model that is frequently used in animals to study pain associated with inflammation is the subcutaneous injection of complete Freund's adjuvant (CFA). For ethical reasons, however, little information is available from humans concerning pain associated with this form of inflammation. Due to an inadvertent subcutaneous injection of CFA into the terminal phalanx of this investigator, a study with an N of 1, was conducted to compare the subjective effects of CFA-induced inflammation with objective measurements.

Freund's Adjuvant↗
PubMed2006

Improved pain management in pediatric postoperative liver transplant patients using parental education and non-pharmacologic interventions.

A pain management intervention, consisting of pretransplant parental education and support, pre- and postoperative behavioral pediatrics consultation, postoperative physical and occupational therapy consultation, and implementation of non-pharmacologic pain management strategies, was introduced to all pediatrics patients receiving liver transplants at Lucile Packard Children's Hospital beginning August 2001. Children receiving transplants pre-intervention (May, 2000 to February, 2001) and post-intervention (August, 2001 to March, 2002) were compared using pain scores, parent perception of pain ratings, length of stay, ventilator days, total cost, and opioid use. A total of 27 children were evaluated (13 historical control, 14 intervention). The two populations did not differ on age at transplant (mean age 53.8 vs. 63.6 months), sex (46.1% vs. 50% male), ethnicity (53.8% vs. 57.1% white, non-Hispanic) weight at transplant (17.5 vs. 24.7 kg), percent with biliary atresia as the primary reason for transplant (42.9% vs. 69.2%), percent with status 1 transplant listing score (38.5% vs. 50.0%), or public insurance status (30.8 vs. 57.2% with Medicaid). No differences were found in mean pediatric intensive care unit (PICU) postoperative length of stay (6.7 vs. 5.3 days), total postoperative length of stay (17.5 vs. 17.5 days), total inpatient length of stay (27.0 vs. 24.4 days), time to extubation (30 vs. 24.3 h), total cost (dollar 147,983 vs. dollar 157,882) or opioid use through postoperative day (POD) 6 (0.24 vs. 0.25 mg/kg/day morphine equivalent). A decrease in mean pain score between POD 0 and 6 (2.82 vs. 2.12; p = 0.047), a decrease in mean parental pain perception score (3.1 vs. 2.1; p = 0.001), and an increase in number of pain assessments per 12 h shift (3.43 vs. 6.79; p < 0.005) were seen. A comprehensive non-pharmacologic postoperative pain management program in children receiving a liver transplant was associated with decreased pain scores, improved parent perception of pain, and an increased number of pain assessments per 12 h shift. No increases in lengths of stay (PICU, postoperative, total), time to extubation, or total cost were found.

Adolescent↗
PubMed2006

Perceptual wind-up in the human oesophagus is enhanced by central sensitisation.

BACKGROUND: Oesophageal acid infusion induces enhanced pain hypersensitivity in non-acid exposed upper oesophagus (secondary hyperalgesia) in patients with non-cardiac chest pain, thus suggesting central sensitisation contributes to visceral pain hypersensitivity in functional gut disorders (FGD). Perceptual wind-up (increased pain perception to constant intensity sensory stimuli at frequencies>or=0.3 Hz) is used as a proxy for central sensitisation to investigate pain syndromes where pain hypersensitivity is important (for example, fibromyalgia). AIMS: Wind-up in central sensitisation induced human visceral pain hypersensitivity has not been explored. We hypothesised that if wind-up is a proxy for central sensitisation induced human visceral pain hypersensitivity, then oesophageal wind-up should be enhanced by secondary hyperalgesia. METHODS: In eight healthy volunteers (seven males; mean age 32 years), perception at pain threshold to a train of 20 electrical stimuli applied to the hand and upper oesophagus (UO) at either 0.1 Hz (control) or 2 Hz was determined before and one hour after a 30 minute lower oesophageal acid infusion. RESULTS: Wind-up occurred only with the 2 Hz train in the UO and hand (both p=0.01). Following acid infusion, pain threshold decreased (17 (4)%; p=0.01) in the UO, suggesting the presence of secondary hyperalgesia. Wind-up to the 2 Hz train increased in the UO (wind-up ratio 1.4 (0.1) to 1.6 (0.1); p=0.03) but not in the hand (wind-up ratio 1.3 (0.1) and 1.3 (0.1); p=0.3) CONCLUSION: Enhanced wind-up after secondary oesophageal hyperalgesia suggests that visceral pain hypersensitivity induced by central sensitisation results from increased central neuronal excitability. Wind-up may offer new opportunities to investigate the contribution of central neuronal changes to symptoms in FGD.

Adult↗
PubMedDate not supplied

[Depression and pain: novel clinical, neurobiological and psychopharmacological data].

Epidemiological studies confirm frequent appearance of pain symptoms in depressive patients and a marked prevalence of depression in pain conditions. These observations seem to point at a close intertwining between mood regulation and pain perception. In the pathogenesis of both depression and pain symptoms, an important role has been attributed to disturbances of serotonergic and noradrenergic neurotransmission as well as to neuropeptides such as opioids and substance P. In mood regulation as well as in the perception and emotional dimension of pain stimuli, such brain structures as the amygdala, anterior cingulate cortex and prefrontal cortex are of main significance. The action of antidepressant drugs results in a normalization of the activity of those neurotransmitter systems and brain structures. It was found that dual action antidepressants (i.e. influencing both serotonergic and noradrenergic system) such as tricyclic antidepressants and new generation drugs (venlafaxine, milnacipram, duloxetine, mirtazapine) exert a stronger antidepressant effect and possess a broader therapeutic spectrum, including also an effect on pain symptoms. These drugs have been also increasingly used for the treatment of pain symptoms in somatic illnesses (e.g. diabetic neuropathy, fibromyalgia).

Adrenergic Uptake Inhibitors↗
PubMed2005

Decreased sensitivity to experimental pain in adjustment disorder.

An altered perception of pain has been described for several psychiatric disorders. To date the influence of adjustment disorders (AD) on pain perception has not been described. Here, we investigated perception of experimentally induced pain in 15 patients suffering from AD (subtype with depressive symptoms) and controls matched for age and sex. Thresholds and tolerances were assessed for thermal and electrical pain on both sides of the body. We found an overall increase of pain thresholds and tolerances in AD patients as compared to controls, predominately on the right side of the body. Analogue findings have been reported for pain perception in major depressive disorder (MDD). Of the data obtained, only thermal pain threshold on the right arm correlated with the severity of depressive symptoms. Although the underlying pathology is elusive it is likely that the mechanisms for reduced pain sensitivity are comparable in MDD and AD.

Adjustment Disorders↗
PubMed2002

Mechanosensory and thermosensory changes across the border of impaired sensitivity to pinprick after mandibular nerve injury.

PURPOSE: The study goal was to determine how sensory function varies across the border of impaired sensitivity to pinprick in patients with mandibular nerve injuries. PATIENTS AND METHODS: Borders of decreased sensitivity to pinprick were mapped in 15 patients who reported altered sensation. Four mechanoreceptive, 2 thermoreceptive, and 2 thermonociceptive functions were studied at 5 sites separated by 0.6 cm across the border. The tests were repeated to evaluate day-to-day consistency in the pattern of variation for each sensory measure. RESULTS: The estimates of sensory function were not found to vary in a systematic manner from outside to inside the pinprick-impaired area for all patients for any of the 8 tests. However, for every test, some patients exhibited large variations. On average, the magnitudes of loss in contact detection, subjective intensity of light touch, and direction discrimination were greatest; the magnitudes of loss in 2-point perception and in heat and cold pain perception were least. Some patients provided no evidence of impairment on certain tests. For some patients, the estimates suggested increased sensitivity within the pinprick-impaired area (eg, to noxious cold stimuli). CONCLUSIONS: Although certain patients exhibit impairment, there is no obligatory loss in light touch, 2-point perception, direction discrimination, or temperature perception across the border of decreased sensitivity to pinprick. The differences among patients suggest that the data from individual patients should be evaluated in clinical studies and in clinical practice. Researchers should not rely solely on average values and summary statistics.

Adult↗
PubMed2004

Influence of social support and emotional context on pain processing and magnetic brain responses in fibromyalgia.

OBJECTIVE: To examine the effects of social support provided by the presence of patient's significant other on pain ratings, pain thresholds, and brain activity associated with tactile stimulation in 18 fibromyalgia (FM) patients and 18 migraine patients (controls), and to assess the influence of emotional context on thermal pain perception and processing of non-pain-related information. METHODS: Thermal pain thresholds and somatosensory brain magnetic responses elicited by tactile stimulation at the elbow (a painful tender point in the FM group) and at the finger (nonpainful site) were evaluated under 2 experimental conditions of social support: patient alone and patient's significant other present. Brain activity was recorded using a 151-channel whole-head magnetoencephalography system. Additionally, the emotional context during presentation of tactile stimuli was manipulated by presenting aversive, pain-related pictures and neutral pictures and asking the patients to imagine that they were experiencing the situations depicted. RESULTS: Thermal pain thresholds indicated greater sensitivity in FM patients than in migraine patients, as well as enhanced sensitivity at the elbow than at the fingers. Specifically, in FM patients, there were significant reductions in pain sensitivity and subjective pain ratings when patients were stimulated at the painful tender point in the presence of their significant others as compared with the ratings when the patients were alone. Brain activity elicited by elbow stimulation was also significantly reduced in FM patients when a significant other was present as compared with the activity when the patient was alone. These effects were not observed in the migraine patients. CONCLUSION: When the significant other was present, FM patients reported less pain and thermal pain sensitivity and showed diminished brain activity elicited upon tactile stimulation of a tender point compared with these levels when the patients were alone. These findings are consistent with the hypothesis that social support through the presence of a significant other can influence pain processing at the subjective-behavioral level as well as the central nervous system level.

Adult↗
PubMed2001

Blocking NMDA receptors in the hippocampal dentate gyrus with AP5 produces analgesia in the formalin pain test.

The hippocampus is an integral component of the "limbic" system and, as such, may contribute to the negative affect and avoidance motivation experienced during pain. A substantial body of evidence indicates that the hippocampus processes pain-related information, that some hippocampal neurons respond exclusively to painful stimulation, and that long-term anatomical changes occur in dentate gyrus neurons, following noxious physical stimulation. NMDA receptor antagonist drugs administered to the hippocampus interfere with long-term potentiation, learning, and memory; these same drugs, when applied to the spinal cord, prevent the long-term neurophysiological changes caused by noxious physical stimulation. This experiment tested whether blocking NMDA receptors in the hippocampal formation reduces nociceptive behaviors in an animal model of persistent human pain. The competitive NMDA receptor antagonist AP5 was injected into the dentate gyrus of alert, unrestrained rats either 5 min before or 15 min following the administration of a subcutaneous injection of formalin irritant. Pain behaviors in both acute and tonic phases of the formalin test were significantly reduced by AP5 treatments. These results support the hypothesis that the hippocampal formation is involved in pain-related neural processing and that NMDA receptor-sensitive mechanisms in the hippocampus are involved in pain perception and/or the expression of pain-related behaviors.

2-Amino-5-phosphonovalerate↗