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Results for “Pain Perception”

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PubMed1985

Mechanisms of ischemic cardiac pain and silent myocardial ischemia.

The mechanisms of cardiac ischemic pain remain obscure. It is unknown whether ischemia causes cardiac pain by the release of chemical substances or by mechanical stretching. It is also unknown whether ischemia activates specific nociceptors and pain fibers or mechanoreceptors and chemoreceptors. In patients who have both painful and painless ischemic episodes, a certain minimal duration and severity of ischemia are necessary but insufficient to explain the presence of pain, since very severe ischemia of long duration can be silent. Thus, central transmission of painful stimuli and the pain perception threshold appear to play major roles in determining the presence or absence of pain. The emotional state and psychologic expectations of patients may affect their perception and threshold of pain considerably.

Angina Pectoris↗

PubMed1997

A longitudinal study of somesthetic perceptual disorders in an individual with a unilateral thalamic lesion.

Several aspects of tactile, thermal and pain perception were evaluated in an individual (R.S.) with a hemorrhagic lesion centered in her left lateral thalamus. Over a 4-year period, psychophysical evaluations were undertaken every 6-8 months, and five magnetic resonance (MR) studies were conducted. Early tests (1991-1992) revealed large contralateral deficits in R.S.'s perception of touch, innocuous temperature, and mechanically evoked cutaneous pain--more so for the upper versus the lower extremity. R.S. showed a similar pattern for heat pain sensitivity, but a more modest deficit than for mechanically evoked pain. She showed a deficit for cold pain sensitivity on her foot, but not for her hand. Thresholds for all types of stimuli ipsilateral to the lesion were within a normative range. Late in 1993, R.S. demonstrated improvements in sensory capacity for touch and mechanically evoked pain contralaterally, although deficits were still evident. During the same period, heat pain sensitivity improved contralaterally, and strikingly, a permanent, ipsilateral hypersensitivity to heat pain developed in her hand. Throughout the entire testing period, R.S.'s ratings of perceived unpleasantness matched the patterns of perceived pain intensity. Thus, the discriminative and the affective dimensions of her pain would change in tandem. However, perceptible innocuous thermal stimuli evoked no affective response when applied contralaterally, despite being described as pleasant when presented ipsilaterally. Throughout the testing period, R.S. reported a persistent numbness on her right hemi-body. Only during a 3-month period in 1995 did she experience spontaneous pain, which was referred to her right foot. The only change in psychophysical performance related to her right foot was a transient but intense thermal allodynia several months prior to her spontaneous pain. The MR studies over this 4-year period showed changes in the extent of edema, gliosis and/or ischemia that could be related to perceptual changes. Thus, the conspicuous observations in this thalamic lesion case were: (i) differential effects upon the various pain modalities (mechanical, heat and cold); (ii) development of thermal allodynia without mechanical allodynia, including an ipsilateral effect; (iii) a deficit in positive affective responses to temperature; and (iv) the different time courses for changes in evoked somesthetic capacity versus spontaneous paresthesias and pathological pain.

Cerebral Hemorrhage↗

PubMed1978

[Opiate receptors and endorphines (author's transl)].

Recent progress in narcotic drug research is briefly reviewed. Several investigators were able, independently to identify stereospecific opiate receptors, which mediate the specific effects of narcotic analgesics. A possible physiological importance of opiate receptors is likely, since endogenous ligands could be detected. Especially from brain and from pituitary glands of several species, quite a number of peptides with morphine-like effects could be isolated. The chemical structure of some of these endorphines could be analyzed. Endorphines are suggested to be involved in pain perception, electroanalgesia, acupuncture analgesia, psychiatric disorders, synthesis and release of pituitary hormones.

Acupuncture Therapy↗

PubMed1974

Responses in human A and C fibres to repeated electrical intradermal stimulation.

The responses of A and C fibres to electrical intradermal stimulation were recorded with microelectrodes inserted percutaneously into intact human skin nerves. Unitary discharges deriving from A fibres were often encountered and sometimes even single C unit deflections were identified. When several C fibres responded to the stimulation, a compact time presentation of the filtered and dot-converted spikes improved the discrimination of individual spikes time-locked to the stimulation, so that unitary C elements could often be identified in the treated records even if the signal-to-noise ratio of the original signals was low. Increases in latency or blockings were traced in both A and C unit responses to repeated excitation, but the influence of repeated activation was more pronounced in thin nerve fibres even at low stimulation frequencies. The decreased excitability of thin nerve endings on repetitive stimulation suggests that not only central factors but also excitation failure in peripheral thin nerve fibres might be responsible for the decrease in pain perception experienced during local intense electrical intradermal stimulation at high frequencies.

Adult↗

PubMed2002

Compliance, tone and sensitivity of the rectum in different subtypes of irritable bowel syndrome.

Irritable bowel syndrome (IBS) consists of various subtypes. It is not known whether these subtypes share a common pathophysiology. Evaluation of motor and sensory function of the rectum using a barostat may help to explore a common pathophysiological background or differences in pathophysiology in subtypes of IBS. We have evaluated compliance, tone and sensitivity of the rectum, in both fasting state and postprandially, using a computerized barostat in 15 patients with diarrhoea-predominant IBS (IBS-D), 14 patients with constipation-predominant IBS (IBS-C) and compared the results with those obtained in 12 healthy controls. Rectal compliance as calculated over the steep part of the pressure-volume curve (17-23 mmHg) was decreased in both IBS groups (IBS-D 8.0 +/- 1.4 mL mmHg-1; IBS-C 5.6 +/- 1.1 mL mmHg-1) compared with controls (24.7 +/- 3.5 mL mmHg-1). The perception of urge was increased only in IBS-D patients, whereas pain perception was significantly increased in both IBS groups. Spontaneous adaptive relaxation was decreased in IBS-D patients. Postprandially, rectal volume decreased significantly in the controls and in IBS-D patients, but not in IBS-C patients. In conclusion, both rectal motor and sensory characteristics are different between IBS-D and IBS-C patients. Therefore, testing of rectal visceroperception, adaptive relaxation and the rectal response to a meal may help distinguish groups of patients with different subtypes of irritable bowel syndrome.

Adult↗

PubMed2006

Interactions of pain intensity and cognitive load: the brain stays on task.

Pain naturally draws one's attention. However, humans are capable of engaging in cognitive tasks while in pain, although it is not known how the brain represents these processes concurrently. There is some evidence for a cortical interaction between pain- and cognitive-related brain activity, but the outcome of this interaction may depend on the relative load imposed by the pain versus the task. Therefore, we used 3 levels of cognitive load (multisource interference task) and 2 levels of pain intensity (median nerve stimulation) to examine how functional magnetic resonance imaging activity in regions identified as pain-related or cognitive-related responds to different combinations of pain intensity and cognitive load. Overall, most pain-related or cognitive-related brain areas showed robust responses with little modulation. However, during the more intense pain, activity in primary sensorimotor cortex, secondary somatosensory cortex/posterior insula, anterior insula, paracentral lobule, caudal anterior cingulate cortex, cerebellum, and supplementary motor area was modestly attenuated by the easy task and in some cases the difficult task. Conversely, cognitive-related activity was not modulated by pain, except when cognitive load was minimal during the control task. These findings support the notion that brain networks supporting pain perception and cognition can be simultaneously active.

Adult↗

PubMed1995

Evaluation of topical viscous 2% lidocaine jelly as an adjunct during the management of alveolar osteitis.

PURPOSE: This study evaluated the efficacy of topical viscous 2% lidocaine jelly for the alleviation of pain experienced during the instrumentation of mandibular third molar extraction sites diagnosed with alveolar osteitis and for pain relief during the postinstrumentation period. PATIENTS AND METHODS: Thirty adult patients with a diagnosis of alveolar osteitis in a mandibular third molar extraction site were included in this prospective, double-blind study. Each patient had their sutures removed, the socket irrigated, and 2% lidocaine jelly placed on the tip and side of the tongue to blind the patient against the test substances. The subjects were then randomly distributed into two groups. Group 1 had a nonactive jelly base placed into the socket 2 minutes prior to the placement of a standard obtundant dressing. Group 2 had viscous 2% lidocaine jelly placed into the socket in the same manner. Patients subjectively quantified their pain intensity pretreatment, during instrumentation, immediately postmanipulation, at 5-minute intervals to 30 minutes, and at 45 and 60 minutes. They also subjectively quantified their pain relief at each of the time intervals following instrumentation. RESULTS: There was no statistical difference between the pretreatment pain experienced by both groups. The use of 2% lidocaine jelly had a measurable (P = .056), but not statistically significant, effect on pain due to instrumentation. At every time interval thereafter, the use of 2% lidocaine jelly elicited a statistically significant (P < .05) decrease in pain perception, and a statistically significant increase in pain relief when compared with the inactive jelly. CONCLUSION: Topical viscous 2% lidocaine jelly is a useful adjunct during the treatment of alveolar osteitis, especially in the early (< or = 60 minutes) postinstrumentation period.

Adult↗

PubMed2005

Placebo in emotional processing--induced expectations of anxiety relief activate a generalized modulatory network.

Placebo analgesia and reward processing share several features. For instance, expectations have a strong influence on the subsequent emotional experience of both. Recent imaging data indicate similarities in the underlying neuronal network. We hypothesized that placebo analgesia is a special case of reward processing and that placebo treatment could modulate emotional perception in the same way as does pain perception. The behavioral part of this study indicates that placebo treatment has an effect on how subjects perceive unpleasant pictures. Furthermore, event-related fMRI demonstrated that the same modulatory network, including the rostral anterior cingulate cortex and the lateral orbitofrontal cortex, is involved in both emotional placebo and placebo analgesia. These effects were correlated with the reported placebo effect and were predicted by the amount of treatment expectation induced on a previous day. Thus, the placebo effect may be considered to be a general process of modulation induced by the subjects' expectations.

Adult↗

PubMed2006

Catechol-O-methyltransferase inhibition increases pain sensitivity through activation of both beta2- and beta3-adrenergic receptors.

Catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines, has recently been implicated in the modulation of pain. Our group demonstrated that human genetic variants of COMT are predictive for the development of Temporomandibular Joint Disorder (TMJD) and are associated with heightened experimental pain sensitivity [Diatchenko, L, Slade, GD, Nackley, AG, Bhalang, K, Sigurdsson, A, Belfer, I, et al., Genetic basis for individual variations in pain perception and the development of a chronic pain condition, Hum Mol Genet 2005;14:135-43.]. Variants associated with heightened pain sensitivity produce lower COMT activity. Here we report the mechanisms underlying COMT-dependent pain sensitivity. To characterize the means whereby elevated catecholamine levels, resulting from reduced COMT activity, modulate heightened pain sensitivity, we administered a COMT inhibitor to rats and measured behavioral responsiveness to mechanical and thermal stimuli. We show that depressed COMT activity results in enhanced mechanical and thermal pain sensitivity. This phenomenon is completely blocked by the nonselective beta-adrenergic antagonist propranolol or by the combined administration of selective beta(2)- and beta(3)-adrenergic antagonists, while administration of beta(1)-adrenergic, alpha-adrenergic, or dopaminergic receptor antagonists fail to alter COMT-dependent pain sensitivity. These data provide the first direct evidence that low COMT activity leads to increased pain sensitivity via a beta(2/3)-adrenergic mechanism. These findings are of considerable clinical importance, suggesting that pain conditions resulting from low COMT activity and/or elevated catecholamine levels can be treated with pharmacological agents that block both beta(2)- and beta(3)-adrenergic receptors.

Animals↗

PubMed1997

Postoperative pain relief following laparoscopic tubal sterilization with silastic bands.

OBJECTIVE: To evaluate postoperative pain relief of intramuscular ketorolac, topical bupivacaine, and placebo in patients undergoing laparoscopic tubal sterilization with silastic bands. METHODS: One hundred five women undergoing laparoscopic tubal sterilization with silastic bands were randomized to one of three groups: one received intramuscular ketorolac and topical placebo applied to the fallopian tubes, the second received intramuscular placebo and topical bupivacaine, and the third received intramuscular placebo and topical placebo. Surgical procedures, anesthesia, and recovery were conducted with standardized protocols. Postoperative pain perception was graded using the modified McGill pain intensity scale at 30 minutes postoperatively, at discharge from the recovery room, and the next morning by telephone interview. Other measured variables included postoperative vomiting, additional analgesia requirement, and length of time spent in the recovery room. RESULTS: Only topical bupivacaine was found to decrease postoperative pain scores significantly over those with placebo, at 30 minutes postoperatively (median score 2 compared with 4, P = .002) and at discharge from the recovery room (median score 2 compared with 3, P = .03). There was no significant decrease in pain scores with intramuscular ketorolac compared with placebo. No differences in pain scores were found between the three groups at the next morning phone call. There were no significant differences between the three groups with respect to requirements for supplemental pain medications in the recovery room, incidence of postoperative vomiting, or length of time spent in the recovery room. CONCLUSION: Topical bupivacaine decreases postoperative pain scores significantly compared with placebo in women undergoing laparoscopic tubal sterilization with silastic bands.

Adult↗

PubMed1985

Transcutaneous electrical nerve stimulation. Practical aspects and applications.

Transcutaneous electrical nerve stimulation (TENS) is a commonly used method of treating patients with pain, both acute and chronic. Although several hypotheses have been proposed, the mechanism by which TENS alters pain perception is still unknown. Symptomatic relief of pain adjunctive to a comprehensive program of pain management is the only justified indication for TENS use.

Acute Disease↗

PubMed2006

Use of BIS monitor in a child with congenital insensitivity to pain with anhidrosis.

We describe a case of a 14-year-old boy with congenital insensitivity to pain and anhidrosis (CIPA) who underwent tarsal tunnel release for tarsal tunnel syndrome. Because of abnormal pain perception, the patient's response to normally painful surgical stimuli is severely impaired and not adequately reflected in a corresponding rise in blood pressure or heart rate. This lack of autonomic feedback to pain stimuli may make it more difficult to assess whether anesthetic depth is adequate to prevent intraoperative awareness and thus to safely conduct anesthesia, especially if muscle paralysis is required for surgical indications. We describe for the first time the use of processed EEG monitoring with a BIS A-2000 monitor to gauge anesthetic depth in a patient with CIPA. Initial forehead bispectral index (BIS) values prior to induction were normal (98) and then ranged between 23 and 79 during the whole surgical procedure. Propofol and lidocaine were used for induction and deep extubation; isoflurane was used as the sole anesthetic for maintenance with concentrations ranging from 0.21% to 0.92% to maintain a target BIS of 40-60. Volatile anesthetic requirements remained low throughout the procedure and no narcotics were necessary during surgery. The BIS monitor served as an adequate tool to help avoid excessive use of volatile anesthetic while assuring a processed EEG consistent with unconsciousness and amnesia. After the patient had recovered and was oriented to place and time in the recovery room, he was asked whether he remembered anything about the surgery and the presence of a breathing tube in his mouth. He denied any recall of such events.

Adolescent↗

PubMed1987

Thermal sensitivity is not changed by acute pain or afferent stimulation.

The effect of conditioning stimulation on thermal sensitivity and clinical pain was studied in 40 patients and six healthy subjects. Thresholds regarding cold, warm and heat pain perception did not differ significantly between the painful and non-painful skin areas in patients or between patients and healthy subjects before stimulation. The patients received either 100 Hz TENS, 2 Hz TENS, 100 Hz vibration, or placebo. No significant changes in thermal sensitivity were observed during and after conditioning stimulation in any of the test groups, although 24/40 (60%) of the patients reported reduction of their clinical pain intensity. The results indicate that (a) thermal sensitivity is not influenced by the presence of clinical pain, (b) the effects of stimulation on thermal sensitivity (thresholds) and clinical pain are not closely related, (c) central inhibitory effects of TENS and vibration are crucial for their pain relieving capacity.

Adult↗

PubMed2001

Clinical evaluation and comparison of 2 topical anesthetics for pain caused by needle sticks and scaling and root planing.

BACKGROUND: Pain generated by needle sticks (Ns) for the delivery of local anesthetic and/or scaling and root planing (SRP) instrumentation is commonly addressed by the use of topical anesthetics, such as a benzocaine-gel preparation (BGP). Pain suppression following such use has been highly variable. Development of medicine-containing patches and adhesives for intraoral use have led to a new approach for topical anesthesia in the form of a transoral lidocaine delivery system (LDS). The purpose of this double-blind study was to evaluate the efficacy of the LDS and also to compare LDS with BGP for pain suppression to Ns and SRP. METHODS: One group of 20 subjects randomly received in both maxillary and mandibular molar-bicuspid areas LDS or BGP on one side and non-anesthetic control on the other side. A second group of 20 subjects compared the effectiveness of LDS directly with BGP in molar-bicuspid areas of both arches. Random order determined the selection for each anesthetic tested between the arches and bilateral. Pain perception was separately scored to a pain-inducing Ns simulation without anesthetic injection at each area and subsequently also to SRP using both a verbal pain scale (VPS) and a visual analog scale (VAS). RESULTS: VPS and VAS results analyzed by Bonferroni-adjusted Wilcoxon matched-pairs signed-rank tests found pain suppression scores significantly (P < 0.005) reduced for Ns by LDS to controls and to BGP. Comparing LDS directly with BGP, LDS was significantly (P < 0.05) more effective in reducing pain to Ns in both arches, to SRP in the maxillary arch, and equally effective as BGP in the mandibular arch. CONCLUSIONS: LDS is more effective than BGP for topical pain suppression to Ns and SRP in both arches.

Administration, Topical↗

PubMedDate not supplied

A prospective randomized clinical trial on pain control after major abdominal surgery.

This study was conducted in order to investigate the advantages and limitations of four analgesic modalities: a) epidural morphine; b) intravenous morphine; c) patient controlled intravenous morphine (patient-controlled analgesia); and d) non-steroidal anti-inflammatory drugs. Eighty patients undergoing major abdominal surgical procedures were prospectively and randomly treated with one of the above-mentioned analgesic methods. Evaluation of pain perception was done using the visual analogue pain score and the simple descriptive scale 4 hours after the procedure, in the early morning on postoperative day 1 and in the afternoon on postoperative days 1, 2 and 3. The need for supplementary analgesia and the onset of complications, if any, were also evaluated for each patient. Patient-controlled intravenous morphine yielded the best analgesic effect over the entire period. Epidural morphine was more effective in the very early postoperative period compared to modalities (b) and (d). Non-steroidal anti-inflammatory drugs, on the other hand, were more effective on the later postoperative days. None of the patients in group C needed supplementary analgesia, as against 20% in group A, 55% in group B and 40% in group D. Patients with hypochondriasis scores > 70 or depression scores > 70 required supplementation of analgesia more often. Morphine proved to be the drug of choice. Drug titration may be modulated in relation to the psychological characteristics of the patient. The best drug titration modality, in fact, is patient-controlled analgesia.

Abdomen↗

PubMed1992

Pain sensitivity range: a useful parameter to measure experimentally induced pain?

Although the Pain Sensitivity Range (PSR) has been presented as a useful parameter to measure pain in the laboratory, it has not received much attention from pain researchers. The goals of the present investigation were to analyze the reliability and stability of the PSR with the cold pressor test method. Results of our study indicate that useful data can be obtained from this parameter. The PSR is a reliable measure which has not shown any variability due to the cyclic changes in pain perception nor due to the supposedly greater pain sensitivity on the left side of the body. The authors postulate that PSR might be a good measure in laboratory research to evaluate the effectiveness of analgesic therapies, for its resemblance to the acute pain experience.

Adult↗

PubMed2002

Differentiating noxious- and innocuous-related activation of human somatosensory cortices using temporal analysis of fMRI.

The role of the somatosensory cortices (SI and SII) in pain perception has long been in dispute. Human imaging studies demonstrate activation of SI and SII associated with painful stimuli, but results have been variable, and the functional relevance of any such activation is uncertain. The present study addresses this issue by testing whether the time course of somatosensory activation, evoked by painful heat and nonpainful tactile stimuli, is sufficient to discriminate temporal differences that characterize the perception of these stimulus modalities. Four normal subjects each participated in three functional magnetic resonance imaging (fMRI) sessions, in which painful (noxious heat 45-46 degrees C) and nonpainful test stimuli (brushing at 2 Hz) were applied repeatedly (9-s stimulus duration) to the left leg in separate experiments. Activation maps were generated comparing painful to neutral heat (35 degrees C) and nonpainful brushing to rest. Directed searches were performed in SI and SII for sites reliably activated by noxious heat and brush stimuli, and stimulus-dependent regions of interest (ROI) were then constructed for each subject. The time course, per stimulus cycle, was extracted from these ROIs and compared across subjects, stimulus modalities, and cortical regions. Both innocuous brushing and noxious heat produced significant activation within contralateral SI and SII. The time course of brush-evoked responses revealed a consistent single peak of activity, approximately 10 s after the onset of the stimulus, which rapidly diminished upon stimulus withdrawal. In contrast, the response to heat pain in both SI and SII was characterized by a double-peaked time course in which the maximum response (the 2nd peak) was consistently observed approximately 17 s after the onset of the stimulus (8 s following termination of the stimulus). This prolonged period of activation paralleled the perception of increasing pain intensity that persists even after stimulus offset. On the other hand, the temporal profile of the initial minor peak in pain-related activation closely matched that of the brush-evoked activity, suggesting a possible relationship to tactile components of the thermal stimulation procedure. These data indicate that both SI and SII cortices are involved in the processing of nociceptive information and are consistent with a role for these structures in the perception of temporal aspects of pain intensity.

Adult↗

PubMed1966

Control of pain motivation by cognitive dissonance.

Responses by humans to painful electric shocks are significantly modified at subjective, behavioral, and physiological levels by verbal manipulations of degree of choice and justification for further exposure to the aversive stimuli. Pain perception, learning, and galvanic skin resistance are altered under these conditions of "cognitive dissonance," as they are by reductions in voltage intensity.

Adult↗