Cognitive development and children's perception of pain.
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Age Factors↗
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Effects of exposure on perception of pain expression.
The present study evaluated the effects of exposure to facial expression of pain, on observers' perceptions of pain expression. Thirty-one male and 49 female observers judged 1-s video excerpts in a signal detection paradigm. The excerpts showed facial expressions of shoulder-pain patients displaying no pain or moderate pain. Participants were randomly allocated to one of four groups, which varied in the number of prior exposures of a 1 s display of strong pain. On each test trial, participants indicated whether the test stimulus showed no pain or pain. Data were analyzed using signal detection theory methods. There was a linear relationship between the density of exposure to strong pain and observers' response criteria: greater exposure was associated with more conservative decisions. On average, participants showed very high levels of sensitivity to pain expression, with women significantly outperforming men. Results are discussed in terms of their implications for pain judgments of health care professionals, adaptation-level theory, and the psychophysical method of selective adaptation.
Adaptation, Physiological↗
The effect of exposure to odor on the perception of pain.
OBJECTIVE: To investigate the effect of a pleasant and unpleasant ambient odor on the perception of human pain and to test two hypotheses of the role of distraction and attention in pain perception. METHOD: Sixty healthy men and women experienced experimentally induced pain (cold-pressor test) during exposure to an ambient pleasant odor (lemon), an ambient unpleasant odor (machine oil), or no odor. Participants reported the degree of pain they experienced at 5-minute intervals for 15 minutes. RESULTS: Individuals exposed to both odors reported significantly greater pain than did those in the control condition at 5 minutes. At 15 minutes, individuals exposed to the unpleasant odor experienced greater pain than did the control group. CONCLUSION: The results suggest that exposure to odors judged to be pleasant and unpleasant may not lead to pain relief. Rather, their perception is associated with greater pain than is no odor. The implications for attentional theories of pain are discussed, as are avenues for future research.
Adult↗
Analgesic effectiveness of subcutaneous carbon-dioxide insufflations as an adjunct treatment in patients with non-specific neck or low back pain.
OBJECTIVES: To evaluate the analgesic effectiveness of subcutaneous carbon-dioxide insufflations in addition to standard physical treatment in patients with non-specific neck or low back pain. DESIGN: A pragmatic, randomized controlled trial. SETTING: Rehabilitation hospital inpatients. INTERVENTIONS: Patients received either subcutaneous carbon-dioxide insufflations (10 treatments) and standard physical treatment or standard physical treatment only. OUTCOME MEASURES: Affective pain perception (42-point scale), sensory pain perception (30-point scale), pain intensity (100 mm visual analogue scale). RESULTS: Between-groups differences were -2.2 [95% CI -5.2; +0.9] (affective pain perception), -1.2 [-3, 0; + 0.7] (sensory pain perception), and -6.5 [-14; +1.0] (pain intensity) respectively in favour of subcutaneous carbon-dioxide insufflations. CONCLUSIONS: Subcutaneous carbon-dioxide insufflations do not seem to be a worthwhile adjunct in the given setting of inpatient rehabilitation. Trials in a monotherapeutic setting, which aim more at the efficacy of subcutaneous carbon-dioxide insufflations, might help to solve this issue.
Aged↗
Pathophysiological mechanisms of central neuropathic pain after spinal cord injury.
After spinal cord injury (SCI), between 10% and 20% of the patients may develop central neuropathic pain. This type of chronic pain usually is a very bothersome sequel and represents a major therapeutic challenge since conventional medical and surgical pain therapies generally are ineffective. This review focuses on recent advances in the understanding of the pathophysiology of this pain syndrome. Important clinical features of central neuropathic pain after SCI include loss of sensations mediated by spinothalamic pathways combined with development of abnormal pain perception (spontaneous continuous pain and abnormally evoked pain). Up-regulation of neuronal activity leading to spontaneous and evoked neuronal hyperactivity/hyperexcitability, may be the neurophysiological substrate for development of abnormal pain perception. This paper describes some neurochemical changes that may be important for the induction and maintenance of neuronal hyperactivity and abnormal pain perception: Increased excitatory glutaminergic activity involving N-methyl-D-aspartate (NMDA) receptor activation, may trigger the intracellular cascade reaction leading to upregulation of neuronal activity/excitability. Changes in voltage-sensitive Na+ channels may contribute to changes in nerve membrane excitability. Other important mechanisms may be loss of endogenous inhibition, including reduced gamma-amino-butyric acid (GABA)ergic, opioid and monoaminergic inhibition. These various mechanisms may provide new targets for treatment of a pain syndrome that traditionally has been so difficult to handle.
Animals↗
Central neuroplasticity and pathological pain.
The traditional specificity theory of pain perception holds that pain involves a direct transmission system from somatic receptors to the brain. The amount of pain perceived, moreover, is assumed to be directly proportional to the extent of injury. Recent research, however, indicates far more complex mechanisms. Clinical and experimental evidence shows that noxious stimuli may sensitize central neural structures involved in pain perception. Salient clinical examples of these effects include amputees with pains in a phantom limb that are similar or identical to those felt in the limb before it was amputated, and patients after surgery who have benefited from preemptive analgesia which blocks the surgery-induced afferent barrage and/or its central consequences. Experimental evidence of these changes is illustrated by the development of sensitization, wind-up, or expansion of receptive fields of CNS neurons, as well as by the enhancement of flexion reflexes and the persistence of pain or hyperalgesia after inputs from injured tissues are blocked. It is clear from the material presented that the perception of pain does not simply involve a moment-to-moment analysis of afferent noxious input, but rather involves a dynamic process that is influenced by the effects of past experiences. Sensory stimuli act on neural systems that have been modified by past inputs, and the behavioral output is significantly influenced by the "memory" of these prior events. An increased understanding of the central changes induced by peripheral injury or noxious stimulation should lead to new and improved clinical treatment for the relief and prevention of pathological pain.
Afferent Pathways↗
Importance of generalized defective perception of painful stimuli as a cause of silent myocardial ischemia in chronic stable angina pectoris.
Growing evidence indicates that most patients with coronary artery disease frequently have episodes of painless myocardial ischemia. Previous studies from our institution show that the severity and duration of myocardial ischemia are necessary but not sufficient factors to explain the occurrence of anginal pain. The responses to a battery of painful stimuli were studied in 12 patients with predominantly painless (group A) and in 15 patients with predominantly painful (group B) ischemic episodes. The severity of myocardial ischemia as assessed by the measurement of ST-segment depression during exercise stress testing and during ambulatory electrocardiographic monitoring was comparable in the 2 groups. Patients in group A had a significantly higher threshold and tolerance for forearm ischemia (+32%, p less than 0.05; +120%, p less than 0.001), cold (+100%, p less than 0.05; +180%, p less than 0.01) and electrical skin stimulation (+145%, p less than 0.01; +109%, p less than 0.01), but the overlap between the 2 groups was often appreciable. In the 6 patients with the longest tolerance times for forearm ischemic pain (all in group A) and in the 5 having the shortest tolerance times (all in group B), plasma levels of beta endorphin, met-enkephalin, noradrenaline and adrenaline were similar during both the basal state and the induction of forearm ischemic pain. Thus, a generalized defective perception of painful stimuli plays an important role in many patients with predominantly painless myocardial ischemia. Other mechanisms, however, may also be important, particularly in patients whose threshold and tolerance values overlap with those of patients who have predominantly painful myocardial ischemia.
Angina Pectoris↗
Use of transcutaneous electrical stimulation in the control of postoperative pain.
Perception and relief of pain were studied in a varied group of fifty patients who had undergone laparotomy with upper abdominal midline incisions. Twenty-six patients were supplied with functioning transcutaneous electrical stimulators. Twenty-four received nonfunctioning machines. The controls were randomized by a nurse not otherwise involved in this study. Only seventeen of the total study group were judged failures and six of the patients had been receiving preoperative narcotics. Patient response was very favorable and pain relief was good to excellent, especially in one group with working stimulators (p is less than 0.008). Patients with known malignant disease did not respond as well as those with benign disease although anxiety may have been an important factor here. Use of the transcutaneous electrical stimulator would seem particularly worthwhile for patients undergoing elective abdominal operations for benign disease with no history of narcotic usage. Briefing the patient preoperatively on the potential value of transcutaneous electrical stimulation as a method of pain relief may improve end-results.
Adult↗
Patients' anticipation of pain and pain-related side effects, and their perception of pain as a result of orthodontic treatment with fixed appliances.
The aim of this study was to investigate the relationship between (i) the pain and its side effects, anticipated by patients before orthodontic therapy, and (ii) the reported pain and its effects after the placement of initial archwires. Before treatment, 50 adolescent patients (median age 13.6 years, range 8.9-39.3 years, 28 female, 22 male) completed a questionnaire concerning their facial and dental appearance, and their expectations regarding pain, its influence on their daily lives, and changes in their facial and dental appearance as a result of orthodontic treatment. In the week following insertion of the initial archwires the patients completed a series of eight questionnaires, where they reported the level of pain experienced and its influence on their daily lives. In the week after archwire insertion, the maximum pain levels reported did not differ statistically from the anticipated pain levels. Patients significantly under-estimated the changes they would have to make in their diet as a response to pain after archwire insertion. Patients who anticipated a greater effect of pain on their leisure activities and those who had a history of frequent headaches reported higher levels of pain and more disruption of their daily lives as a result of pain. This pattern of response is consistent with a medical model where anxious patients and those with a history of chronic pain reported more pain after surgery.
Adolescent↗
Disorders characterised by pain: a methodological review of population surveys.
OBJECTIVE--To review a series of conceptual and methodological problems encountered in surveys primarily devoted to pain disorders. CRITERIA FOR INCLUSION AND EXCLUSION OF ARTICLES--Published reports were systematically collected by electronic database searches (Medline), citations in existing publications, and through personal contacts. Relevant articles from clinical and epidemiological research on pain were included and special attention was given to epidemiological research on back pain. CONCLUSIONS--Surveys of pain disorders should be based on a multidimensional pain model that includes nociceptive input, pain perception, suffering, and pain behaviour as major components. Because of the limited applicability of diagnostic procedures or genuine "non-specificity" of pain states, or both, epidemiological surveys may result in a considerable proportion of cases without an identifiable pathophysiological basis. Staging and grading procedures for pain disorders (as distinguished from classification) may comprise various aspects of pain perception: regional distribution, pain intensity, temporal characteristics, sensory qualities, and dimensions of cognitive-emotional appraisal. Description of temporal development and chronification (staging) should refer to different components of the multidimensional pain model. Explicit a posteriori procedures for grading are preferable to implicit grading based on question wording. Evidence from several sources suggests that localistic concepts of pain may be misleading. Identification of complex pain syndromes should be one primary target for epidemiological pain surveys. Of the many factors that may impair the reliability and validity of data collected in pain surveys, recall biases seem to deserve special attention.
Back Pain↗
Exercise, hypoalgesia and blood pressure.
A number of studies have indicated that exercise is associated with alterations in pain perception. In general, investigators have typically found a hypoalgesic response (i.e. diminished pain perception) to occur during and following exercise. It is currently unclear why exercise alters pain perception but some research indicates that there is an interaction between pain modulatory and cardiovascular systems. Elevated resting blood pressure (BP), such as hypertension, has been associated with reduced sensitivity to noxious stimulation. In addition, acute elevations in BP (pharmacologically) have also been associated with alterations in pain perception. Exercise elevates BP due to the physiological demands of the activity, but only a limited amount of research has been conducted examining the interaction between exercise, hypoalgesia and BP. Results from this research indicate that exercise significantly alters cardiovascular responses, and these alterations appear to be associated with alterations in pain perception. However, the interaction between exercise, pain perception and BP has been primarily examined indirectly. The mechanisms underlying the interaction between BP and pain perception are currently not entirely understood. It has been suggested that endogenous opioids may be involved in the interaction between BP and pain perception; however, results appear to be equivocal in the human research that has been conducted in this area. It has also been suggested that baroreceptor activation may play a role in the interaction between BP and pain perception.
Blood Pressure↗
Effects of nondirective suggestions on pain tolerance, pain threshold and pain intensity perception.
In this experiment, we followed the issue whether nondirective suggestions have an effect on pain threshold, pain tolerance, and perception of pain intensity. 48 healthy subjects consented to take part. At intake into the study (t1), pain threshold and pain tolerance were assessed in all subjects using a pressure algometer. Perception of maximum pain intensity perception was rated on a scale of 0 to 25. Seven days later, the session was repeated (t2). Subjects were randomly assigned to one of two groups. One group received nondirective suggestions as pretreatment. Subjects listened to a tape of 20 min. which consisted of general information about pain theory. In this context, suggestions for coping with pain were placed. The other group served as a control and received no pretreatment. Analysis showed that pain tolerance was significantly prolonged in the group who received nondirective suggestions, while pain threshold and perception of maximum pain intensity did not differ across groups. This study demonstrates that nondirective suggestions are effective in prolonging pain tolerance. It can be stated that, beside information, cues on coping with pain may be helpful in clinical practice.
Adaptation, Psychological↗
Women's perceptions of pain and discomfort after childbirth in Angola.
Prophylactic treatment against postpartum haemorrhage is a widely investigated area and injection of Oxytocics has been considered as the best choice. The occurrence of postpartum pain and discomfort was studied in a population of birthing women in an overcrowded labour ward in Angola where the oxytocin-filled device Uniject was used. This study indicates that birthing women's perceived postpartum pain increases with parity and during breastfeeding, but does not confirm that injection of oxytocin increases pain and discomfort. This is an important finding, since it might facilitate the introduction of a management practice, likely to reduce haemorrhage-related maternal morbidity and mortality after delivery in underprivileged populations. The birthing women were, by and large, satisfied with the care and treatment provided, but the encounters with midwives seem to vary in quality. Further investigation is needed to elucidate parturient women's experience of postpartum pain and their perceptions of the quality of care and treatment.
Adult↗
A dose-response study of the effects of alcohol on the perceptions of pain and discomfort due to electric shock in men at high familial-genetic risk for alcoholism.
Alcoholics have previously been found to be more sensitive to painful stimulation than controls, and more sensitive to the pain-reducing effects of alcohol. The present study was designed to examine these effects in men at high familial-genetic risk for alcoholism and controls. Subjects were assigned to one of four alcohol doses [0.135 (active placebo), 0.50, 0.75, or 1.00 ml 95% USP alcohol/kg body weight]. Ratings of the amount of discomfort and pain experienced during an aversive shock procedure were taken immediately post-shock, both while subjects were sober and after they had consumed one of the four alcohol doses. High risk men were found to rate the experience of the shock as more uncomfortable and painful overall than the low risk controls. Pharmacologically significant levels of alcohol were found to reduce or eliminate these group differences, suggesting that alcohol has a "normalizing" effect on pain and discomfort perceptions in high risk men. Only the higher doses of alcohol were found significantly to dampen subjects' shock rating scores. High risk males' increased sensitivity to pain and discomfort, combined with the negatively reinforcing effects of reducing these perceptions at moderate to high alcohol doses, may play a role in predisposing high risk males for the development of alcoholism.
Adolescent↗
Intravenous sedation prior to peribulbar anaesthesia for cataract surgery in elderly patients.
PURPOSE: To investigate if pre-block iv sedation using midazolam, alfentanil, or a midazolam-alfentanil combination minimizes pain, reduces pain recall, and attenuates haemodynamic responses to peribulbar block; and to determine other factors influencing oxygen saturation (SpO2) following iv sedation. METHODS: In a randomized, double-blind, placebo-controlled study, 120 patients, mean age 73 yr, having cataract surgery with peribular anaesthesia, were randomized to receive either normal saline, 1 mg midazolam, 500 micrograms alfentanil, or 0.5 mg midazolam plus 250 micrograms alfentanil. Blood pressure (BP), heart rate (HR) and pulse oximetry readings were recorded before injection of the study drugs, immediately after completion of the peribulbar block, and 10 min after the block. Pain from the anaesthetic block was assessed immediately after the block and after surgery using a visual analog scale, and recall of pain was assessed by telephone on the day after surgery. RESULTS: Pain scores were low in all four groups. Midazolam-alfentanil reduced pain perception, and all iv sedation used reduced pain recall. Midazolam reduced systolic BP; alfentanil +/- midazolam reduced HR. All iv sedation reduced SpO2 more than did saline, but not usually to a clinically important level. Nine patients had a SpO2 < or = 90%; all had received alfentanil with or without midazolam. It was not possible to predict oxygen saturation levels by any factors other than iv sedation and baseline SpO2 levels. CONCLUSION: Intravenous sedation with midazolam or alfentanil or in combination reduced pain perception, pain recall, and haemodynamic responses from peribulbar anaesthesia. Fifteen percent of patients given alfentanil developed clinically important oxygen desaturation. The use of fine gauge needles combined with slow injection of anaesthetic solution causes minimal discomfort, and routine iv sedation may be unnecessary.
Aged↗
Melatonin reversal of lipopolysacharides-induced thermal and behavioral hyperalgesia in mice.
The perception of pain sensation (threshold), whether local or central, is altered by inflammatory processes. Anti-inflammatory drugs block this by raising the pain threshold and by reducing the inflammatory process. Melatonin is claimed to have anti-inflammatory activity in animal models of acute and chronic inflammation. However, it is not known whether melatonin can reverse the hyperalgesia that is secondary to the inflammation. The present study aimed to assess the modulatory effect of melatonin on lipopolysaccharides-induced alteration of pain perception in mice. Central perception of pain was assessed with the tail-flick and hot-plate methods and local hyperalgesia was assessed by noting the animal's reactions such as paw licking and rearing after the intraplantar injection of lipopolysaccharides (5 microg/paw). Local administration (intraplantar) of lipopolysacharides induced hyperalgesia when measured by both central effects and behavioral reactions. Melatonin (5 and 10 mg/kg), like dexamethasone (0.5 mg/kg), given 30 min prior to, and 4 and 8 h after lipopolysaccharides (5 microg/paw) challenge attenuated central and behavioural hyperalgesia. The attenuation of lipopolysaccharides-induced hyperalgesia by melatonin was not reversed by naltrexone (4 mg/kg). In vitro studies showed that melatonin, in concentrations ranging from 100 to 1000 nM, suppressed tumor necrosis factor-alpha (TNF-alpha) without affecting the nitric oxide (NO) release in lipopolysaccharides-activated murine peritoneal macrophages. Taken together, the present results demonstrated that melatonin reverses lipopolysaccharides-induced hyperalgesia.
Adjuvants, Immunologic↗
Relationship between a genetic predisposition to hypertension, blood pressure levels and pain sensitivity.
INTRODUCTION: The aim of this study was to determine whether the degree of blood pressure elevation and/or a genetic predisposition to hypertension have a major role in determining a reduced pain perception in hypertensives. The reasons underlying the relationship between blood pressure elevation and pain perception mechanisms are not completely understood. METHODS: One hundred and four untreated hypertensive patients (65 subjects with and 39 without a positive parental history of hypertension) together with a control group of 42 subjects (20 normotensive offspring of normotensive parents, and 22 normotensive offspring of hypertensive parents) were submitted to standard blood pressure evaluation, 24-h blood pressure monitoring and dental pain perception evaluation. RESULTS: Both pain threshold and tolerance were found to be higher in hypertensive than normotensive subjects (P < 0.0001 and P < 0.015, respectively). Positive significant correlations were found between both 24-h systolic and diastolic pressure and the pain perception variables. When a 2 x 2 ANOVA test was performed, factoring for the effects of both blood pressure status and family history of hypertension on pain sensitivity, a significant effect was revealed only for blood pressure status. Moreover, after controlling for blood pressure by a covariate analysis, no significant difference was found between the subjects with or without hypertensive parents as regards pain perception variables. CONCLUSIONS: Pain sensitivity is correlated to blood pressure levels whereas the parental history of hypertension per se does not affect the pain perception pattern. Thus, the degree of blood pressure elevation, more than a genetic predisposition to hypertension may influence the mechanisms leading to hypalgesia in hypertension.
Adult↗