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PubMed1999

Evaluation of prilocaine for the reduction of pain associated with transmucosal anesthetic administration.

This investigation evaluated the use and efficacy of prilocaine HCl (4% plain Citanest) for minimizing pain associated with the intraoral administration of local anesthesia. Clinical anecdotes support the hypothesis that prilocaine without a vasoconstrictor reduces pain during injection. To determine relative injection discomfort, use of 4% plain prilocaine was compared with use of 2% lidocaine with 1:100,000 epinephrine and 2% mepivacaine with 1:20,000 levonordefrin. Prior to routine endodontic procedures, 150 adult patients received 0.3 to 1.8 mL of local anesthetic via the same gauge needle without the use of a topical local anesthetic. Injection methods included buccal infiltration, labial infiltration, palatal infiltration, and inferior alveolar nerve block. Following each injection, patients were asked to describe the level of discomfort by scoring on a visual analog scale of 1 to 10, where 1 = painless and 10 = severe pain. Analyses via 2-way analysis of variance revealed no interaction between anesthetic and site of injection. However, there were statistically significant differences among the injection sites. Post hoc analysis revealed that prilocaine was associated with significantly less pain perception when compared to mepivacaine and lidocaine. These results suggest that differences in initial pain perception during transmucosal injection may be a function of the local anesthetic use, and prilocaine can produce less discomfort than the others tested.

Adult↗

PubMed2001

Local and remote effects of hypnotic suggestions of analgesia.

The present study was designed to further characterize hypnotic analgesia and particularly to examine whether the effects are due to a selective alteration of pain perception and are organized somatotopically. Thirty-two healthy volunteers participated in this study. Thermal detection thresholds for warmth and cool stimuli and heat pain thresholds were measured at both the upper and lower left limbs by means of a thermotest. Measurements were performed before, during and after a hypnotic session during which the subjects were administered a French adaptation of the Stanford Hypnotic Susceptibility Scale and then standardized suggestions of analgesia limited to the left foot. Heat pain thresholds were significantly increased at both the lower and upper limbs. Changes at the foot were positively correlated with the hypnotic susceptibility score, while, unexpectedly, changes at the hand were negatively correlated with the susceptibility score. Mean detection thresholds for warmth and cool stimuli were also altered at both the lower and upper limbs during hypnosis, but these modifications were correlated neither with susceptibility nor with the changes in heat pain threshold. These results indicate that hypnotic suggestions can selectively and somatotopically alter pain sensation in highly susceptible subjects. It is also suggested, however, that suggestions of analgesia can induce selective alterations of pain perception in poorly susceptible subjects, although these effects did not appear to be localized 'appropriately'.

Adult↗

PubMed1999

[Respiratory and circulatory parameters as indicators of the postoperative analgesic demand in newborns and infants].

AIM OF THE STUDY: Due to immature cognitive functions, infants are unable to communicate their pain perception verbally. To assess postoperative analgesic demand, the anaesthetist has to rely on observational techniques. Generally, pain expression is considered to be a multidimensional phenomenon consisting of physiological, motor-reflex and behavioural patterns. The majority of observational approaches to pain assessment in infants use the behavioural dimension only, regardless of the fact that pain perception might contribute substantially to the stress response. The aim of this study is to evaluate, whether sensitivity and specificity of a behavioural pain scale (CHIPPS [1]) can be improved by adding physiological measures, especially those representing the stress response. PATIENTS AND METHODS: 30 infants aged 0-12 months and scheduled for unilateral herniorrhaphy were studied prospectively. In addition to 9 behavioural items (crying, facial expression, wrinkling of the forehead, motoric restlessness; posture of fingers, arms, legs, toes and torso) the ratio of actual physiological measurements (heart rate, respiratory rate, blood pressure) and their respective preoperative baseline values were recorded by a single observer in 5 minutes intervals during the first hour after recovery from anaesthesia. Maximal efforts were made to achieve valid measures. Factor analysis was performed to determine the dimensionality of the complete item pool. For additional validity testing, receiver operating characteristic curves (ROC) were calculated using the independent opinion of an experienced clinician as an external criterion. Discriminant analysis was performed to assess the accuracy of a combined behavioural and physiological scale. RESULTS: The factor analysis resulted in two independent dimensions: behaviour and cardiocirculatory measurements. The strong intercorrelations of all behavioural items and the fact, that the affective pain experience is expressed by a specific mimic behaviour, suggest the behavioural dimension to be regarded as pain expression. Because of the strictly orthogonal structure of the factor system, the circulatory and the respiratory dimension lack any relationship to pain experience. In addition to these statistical reasons, considerations on practicability disprove blood pressure and respiratory rate as useful pain indicators: Whereas the observer never failed to obtain a behavioural score, only 60% of the blood pressure measures and 80% of the respiratory rates were valid. In contrast, heart rate counts were obtained in over 99% and thus have to be considered as the only practicable physiological measurement in the early postoperative period. Corresponding to the results of the factor analysis, ROC curves suggest that the ability of the heart rate alone to assess pain is not substantially better than a random process, whereas the behavioural scale performs well. In addition the heart rate failed to improve the accuracy of the behavioural scale as shown by the results of a discriminant analysis. CONCLUSIONS: Despite the multidimensional approach and the corresponding multivariate analyses, a unidimensional scale consisting of behavioural items was found to be a valid indicator of an postoperative analgesic demand. Due to the lack of diagnostic properties and difficulties to obtain sound values even under research conditions, physiological measurements like blood pressure, respiratory rate and heart rate are not suitable for the assessment of a postoperative analgesic demand in infants, neither for clinical nor for research purposes.

Analgesics↗

PubMed1993

Effects of movement-related cortical activities on pain-related somatosensory evoked potentials following CO2 laser stimulation in normal subjects.

We investigated the change in pain perception produced by the application of movement and vibration to areas adjacent to, and remote from, the painful stimulus. Pain-related somatosensory evoked potentials (pain SEPs) and the pain threshold were evaluated following CO2 laser stimulation in 17 normal subjects. The concurrent application of vibratory stimuli and the voluntary movement of the fingers of the hand to which the pain stimulus was applied significantly reduced and prolonged the pain SEPs and increased the pain threshold, consistent with the gate control theory. Pain SEPs were also significantly attenuated by voluntary (P < 0.001) and passive (P < 0.02) movement of the remote areas such as the foot, but the pain threshold was unaffected. This finding was not produced by vibration or movement imagery of the limbs without active movement. Therefore, interactions between pain perception and movement-related cortical activities must take place in some areas of the brain without relieving pain.

Adult↗

PubMed1996

[Exteroceptive suppression of activity of the temporal muscle. Principles and applications].

The exteroceptive suppression period (ES) of the temporalis muscle activity is a trigemino-trigeminal brain stem reflex. It will be elicited most when stimulating trigeminal sensory afferents by painful stimuli and typically leads to a biphasic interruption of voluntary muscle activity. The first phase of decreased voluntary activity is called the early exteroceptive suppression period (ES1), the second, the late exteroceptive suppression period (ES2). Between these two suppression periods a phase of increased muscle activity, the so-called facilitation period (FP), can be seen. This phenomenon can be modulated by different stimulating parameters and usually, in healthy subjects, this normal pattern of the exteroceptive suppression can be elicited regularly. The reflex answer may occur at low non-painful stimulus intensities; typically, however, it appears to be most pronounced with high-intensity stimuli. Because of the obvious relationship between stimulus intensity, pain perception and reflex, the reflex is regarded as an antinociceptive reaction. The absence of an inhibition of motor activity can be visualized, for example, in hemimasticatory spasm or dystonic disorders. However, above all the ES nowadays attracts most attention as a tool to analyse different pain syndromes. One main advantage of this method in man is the ability to evaluate certain antinociceptive brain stem mechanisms functionally by means of a simple noninvasive technique. A large number of results have been obtained showing that chronic pain syndromes such as chronic tension-type headache and migraine cause changes within the normal ES recording pattern. Furthermore, some substances used in pain therapy, such as serotonin agonists or antagonists, acetylsalicylic acid or naloxone, may also alter the general appearance of the ES. This review will summarize different parameters that influence the ES reflex answer. Furthermore, the diagnostic value of changes in the ES for pathophysiological processes regarding pain perception and processing in certain pain syndromes will be discussed.

Afferent Pathways↗

PubMed2006

Frequency of headache is related to sensitization: a population study.

Central sensitization is thought to play an important role in the chronification of tension-type headache and in the maintenance and exacerbation of the migraine attack. It has, however, almost exclusively been studied in highly selected patients from headache clinics. The aim of the present study was to evaluate pain perception in primary headaches in the general population. Stimulus-response functions for pressure versus pain, tenderness and pressure pain thresholds were studied in a random sample of 523 adults from the general population. All results were controlled for the effects of age and gender. The area under the stimulus-response function was increased in chronic- and frequent episodic tension-type headache compared with subjects without headache (p<0.001, p<0.001) and in chronic tension-type headache compared with migraine (p=0.01). Increasing slope (p<0.0001) and displacement towards lower pressures was found in the following order: no headache, migraine, frequent episodic tension-type headache, chronic tension-type headache. The displacement of the stimulus-response function was closely associated with frequency of headache. Finally, the stimulus-response function tended to be qualitatively altered in patients with frequent headache. The findings demonstrate, for the first time in a population-based study, a close relation between altered pain perception and chronification of headache, which most likely can be explained by central sensitization.

Adult↗

PubMed2002

Patients' behavior at the time of injury: effect on nurses' perception of pain level and subsequent treatment.

This study examined whether nurses who currently provide direct patient care would perceive and treat pain differently in patients whose pain resulted from activities involving different levels of socially acceptable behavior. Clinical vignettes (differing only with respect to information provided about the patient's behavior at the time of injury) were randomly distributed to all medical/surgical, critical care, and emergency room nurses at this institution. Nurses were asked to record their perception of the patient's pain level and to indicate how much morphine should be given. Nurses (n = 167) did not differ significantly in their mean pain ratings (p =.86) or in the average amount of morphine (p =.80) given to the 2 patients. However, medical/surgical nurses indicated that they would give significantly less morphine to the patient who was presented as engaging in less socially acceptable behavior at the time of injury (p =.03). Overall, significantly more nurses correctly increased the next dose of morphine for the patient who was presented as having injured him or herself while participating in more socially acceptable behavior (p =.003). Thus, although the level of social acceptability of the patient's behavior at the time of injury did not significantly affect the average pain rating or morphine dose that the nurse would have reportedly given, there is evidence that the nurses would have been less aggressive in ensuring adequate pain treatment in the patient exhibiting less socially acceptable behavior.

Attitude to Health↗

PubMed2006

Cortical involvement during the description of head pain.

Pain perception involves several cortical areas. Our purpose was to examine cortical activity in patients describing their cephalic pain with the MacGill Pain Questionnaire (MPQ). Two SPECT analyses were performed in pain-free periods in 10 patients with migraine (n=8) or myogenous facial pain (n=2). The MPQ was administered in the first session, while no task was to be performed during the second session. Differences were calculated using statistical parametric mapping (SPM99), also taking the MPQ pain rating index (PRI) as covariance. During the MPQ session, clusters of activation were observed in the orbitofrontal cortex, the insula and the anterior cingulate cortex (ACC) of the left brain, but not significantly so. Using the MPQ PRI as covariate, significant areas of activation were found in the left frontal lobe, the Brodmann area 32 and in the ACC. The description of pain seems to activate cortical areas similar to those involved in actual pain perception.

Adult↗

PubMedDate not supplied

[Psychological stress of inpatients with acute and chronic lumbar syndrome].

PURPOSE: As a result of its increasing incidence and social medical implications, low back pain with either chronic or acute symptoms presents a major challenge for our society. The psychological background of pain perception and valuation has been explored in various studies; frequently, no positive correlation was found between subjective pain perception and structural orthopedic findings. METHOD: A symptoms checklist (SCL-90-R) was used to compare a group of patients hospitalized because of low back pain with a group of asymptomatic controls. Additionally, the pain-specific questionnaire (ERSS) was employed to verify the validity of the depressive mood scale by means of the corresponding scale in the SCL-90-R. RESULTS: When the SCL-90-R was given to both groups, significant differences could be observed between the patients and the controls on the scales for somatisation, depressive mood, anxiety, phobias and psychoticism. Moreover, patients with chronic pain had higher scores on the scales for phobias and the global marker of "positive symptom total" (PST) than patients with acute back pain. On the scales for somatisation and insecurity during social contacts, women reported higher levels of psychological distress than men. Age-related differences were not observed. The depressive mood scale of the ERSS appears to be valid. With the SCL-90-R we could demonstrate significant differences between patients with acute and chronic pain, and between the sexes. No differences were found in the age-group comparison. CONCLUSION: In patients with low back pain, psychological parameters have to be taken into account in any comprehensive concept of conservative treatment.

Acute Disease↗

PubMed1992

[Determination of the spread of epidural anesthesia. A comparison between pin-prick and a new method using a metallic roller].

A new method (metal roller) for testing the spread of analgesia in regional anesthesia is introduced. The possible advantages of testing with a metal roller (cold sensation) in comparison to the pinprick method are investigated and discussed to determine whether loss of cold-sensation is comparable to loss of pinprick-sensation and thus reliable in clinical practice. METHOD AND MATERIAL. Spread of analgesia was tested with both the metallic roller and the conventional pinprick method in 40 patients (20 epidural and 20 spinal blocks), and pain perception or cold perception were compared. RESULTS. In epidural as well as in spinal anesthesia, similar levels of loss of pain perception and cold perception were found. DISCUSSION. Testing the spread of analgesia after nerve bock by the pinprick method is sometimes unpleasant for the patient. The metal roller is not unpleasant, and the possible danger of contamination or pinprick pain is virtually impossible because physical integrity is preserved and the feeling of "cold" is not harmful.

Anesthesia, Epidural↗

PubMed1989

Pain response post-chemonucleolysis or disc excision.

Eighty-five patients with proven lumbar disc displacement who had failed at least 3 months of conservative care were enrolled in this prospective study. The patients were self-selected into one of three treatment groups: collagenase, chymopapain, or surgery, based on information provided regarding the nature benefits and risks of each. Pain levels were self-recorded by patients in the post-treatment period, and follow-up physical examinations were performed and data were collected regarding hospital stay and return to activities for 3 months post-treatment. Patient's pain perception post-treatment was statistically lowest in the surgically treated group. The enzyme-injected patients reported higher levels of pain perception throughout the follow-up period, with collagenase-treated patients reporting more pain than chymopapain patients. Surgical patients had the most satisfactory outcome of treatment at 3 months. An explanation regarding the differences in pain response to the two enzymes is offered based on in vitro studies of the effects of the enzymes on the two major structural macromolecules of the connective tissue matrix.

Chymopapain↗

PubMedDate not supplied

Differences and similarities between patient and physician perceptions of patient pain.

A reasonably accurate perception of pain severity by physicians can be a useful tool in effectively managing acute pain. This study measured the similarities and differences between patient and physician ratings of patient pain through the use of a linear analogue scale of pain severity. A total of 401 patients presenting with acute pain of up to seven days' duration were studied. Data were gathered from patients presenting to the seven family practice clinics associated with the Department of Family Practice and Community Health at the University of Minnesota. Whereas the physician mean rating of patient pain was found to be significantly lower than the patient mean rating (3.52 vs. 4.37, P = 0.001), raw ratings by physicians and patients were found to have a relatively strong and significant correlation (R = 0.66, P = 0.001). The difference in mean ratings between patients and physicians remained the same regardless of physician or patient gender, patient age, whether or not a diagnosis was made, organ system category in which the pain was located, or training level of physician. The physician mean ratings were always significantly lower than the patient mean ratings, and there was no significant difference in the mean differences in ratings among the subgroups compared.

Acute Disease↗

PubMed1987

Patients with irritable bowel syndrome have greater pain tolerance than normal subjects.

A low tolerance for pain has been postulated as a factor in the expression of symptoms in patients with irritable bowel syndrome. This has been based on previous work demonstrating reduced intestinal thresholds for rectal pain induced by balloon distention in patients with irritable bowel syndrome. As the disease may alter the rectal response to distention, inferences regarding pain perception and reporting behavior cannot be drawn from these data. In this study, using electrocutaneous stimulation, we found that patients with irritable bowel syndrome had pain reporting behavior comparable to patients with Crohn's disease. Both patient groups were less likely than normals to report a noxious stimulus as painful. This suggests that pain perception and reporting is attenuated in patients with chronic abdominal pain and, accordingly, a generalized reduction in the threshold for reporting pain is not a factor in the expression of symptoms in the irritable bowel syndrome.

Abdomen↗

PubMed2005

Somatotopic organisation of the human insula to painful heat studied with high resolution functional imaging.

Pain perception is a multidimensional phenomenon, derived from sensory, affective, cognitive-evaluative and homeostatic information. Neuroimaging studies of pain perception have investigated the role of primary somatosensory cortex (SI); however, they have typically failed to demonstrate the expected somatotopy. An alternative network for the sensory component of pain has been proposed, involving a temperature and pain-specific nucleus of the thalamus (VMpo) and its projections to dorsal posterior insula (dpIns). According to this hypothesis, projections to the insula should be arranged somatotopically. In order to test for the presence of somatotopy in the operculo-insular brain region, we delivered moderately painful thermal stimuli to the right face, hand and foot in 14 healthy subjects and recorded brain responses using high resolution functional magnetic resonance imaging at 3 T. For each subject, the thermode temperature was adjusted to produce pain ratings of 5 to 6 out of 10, which corresponded to average temperatures for the face, hand and foot of 49.6, 48.5 and 48.5 degrees C, respectively. Examination of mixed effects group activation maps suggested a pain-related somatotopy in the contralateral posterior insula and putamen. Construction of frequency maps revealed that face activation within the posterior insula was anterior to both hand and foot, whilst foot activation was located medially in the circular sulcus. Single subject analysis demonstrated that only coordinates for dpIns activation were significantly dependent on stimulus location (Hotelling's Trace, P = 0.012). Coordinates for face (paired t test, P = 0.004) and hand (P < 0.001) activity were more lateral than those for foot, whilst face activation was anterior to the foot (P = 0.037). Based on single subject analyses, the average standard space (MNI) coordinates for face, hand and foot activity were (-40,-16,11), (-40,-19,14) and (-35,-21,11) respectively.

Adult↗

PubMed2003

The unequal burden of pain: confronting racial and ethnic disparities in pain.

CONTEXT: Pain has significant socioeconomic, health, and quality-of-life implications. Racial- and ethnic-based differences in the pain care experience have been described. Racial and ethnic minorities tend to be undertreated for pain when compared with non-Hispanic Whites. OBJECTIVES: To provide health care providers, researchers, health care policy analysts, government officials, patients, and the general public with pertinent evidence regarding differences in pain perception, assessment, and treatment for racial and ethnic minorities. Evidence is provided for racial- and ethnic-based differences in pain care across different types of pain (i.e., experimental pain, acute postoperative pain, cancer pain, chronic non-malignant pain) and settings (i.e., emergency department). Pertinent literature on patient, health care provider, and health care system factors that contribute to racial and ethnic disparities in pain treatment are provided. EVIDENCE: A selective literature review was performed by experts in pain. The experts developed abstracts with relevant citations on racial and ethnic disparities within their specific areas of expertise. Scientific evidence was given precedence over anecdotal experience. The abstracts were compiled for this manuscript. The draft manuscript was made available to the experts for comment and review prior to submission for publication. CONCLUSIONS: Consistent with the Institute of Medicine's report on health care disparities, racial and ethnic disparities in pain perception, assessment, and treatment were found in all settings (i.e., postoperative, emergency room) and across all types of pain (i.e., acute, cancer, chronic nonmalignant, and experimental). The literature suggests that the sources of pain disparities among racial and ethnic minorities are complex, involving patient (e.g., patient/health care provider communication, attitudes), health care provider (e.g., decision making), and health care system (e.g., access to pain medication) factors. There is a need for improved training for health care providers and educational interventions for patients. A comprehensive pain research agenda is necessary to address pain disparities among racial and ethnic minorities.

Attitude of Health Personnel↗

PubMed1998

Somatosensory cortex: a comparison of the response to noxious thermal, mechanical, and electrical stimuli using functional magnetic resonance imaging.

In the present study, functional magnetic resonance imaging (fMRI) was used to examine pain perception in humans. Three types of noxious stimuli were presented: electric shock (20.8 mA, 2 Hz), heat (48 degrees C), and mechanical, as well as a control tactile stimulus. The significance of activation at the level of the voxel was determined using correlation analysis. Significant region of interest (ROI) activation was determined by comparing the percentage of active voxels in each ROI to activation in a control ROI in the visual cortex. In response to tactile and shock stimuli, consistent activation was seen in the postcentral gyrus, parietal operculum, and ipsilateral cerebellar cortex. No significant cortical activation was detected in response to noxious heat or mechanical stimulation when compared to nonpainful intensity levels. The data did not indicate adaptation, although further study in this area is necessary. Stationary noxious thermal and mechanical stimulation are "pure" noxious stimuli, while electrical stimulation influenced nociceptive and nonnociceptive receptors. Lack of detectable activation in response to pure noxious stimuli supports the idea that nociceptive and nonnociceptive fibers are interspersed in the somatosensory cortex. Conflicting results from recent functional imaging studies of pain perception regarding cortical activation indicate that it is essential to consider both the tactile and nociceptive components of the stimuli used, the spatial extent of stimulation, and the possibility of adaptation to the response. Furthermore, these results suggest that subtractive or correlative methods may not be sufficiently sensitive to image the activity of nociceptive cells, which are sparsely distributed throughout the somatosensory cortex.

Adolescent↗

PubMed1996

Generalized hypervigilance in fibromyalgia: evidence of perceptual amplification.

The hypervigilance model of pain perception states that chronic pain patients have a heightened sensitivity to pain (e.g. low threshold and tolerance) because of increased attention to external stimulation and a preoccupation with pain sensations. This study tested the hypothesis that individuals with fibromyalgia, a chronic pain disorder of undetermined origin, have a generalized hypervigilant pattern of responding that extends beyond the pain domain. Twenty fibromyalgia out-patients, 20 rheumatoid arthritis (RA) patients, and 20 normal controls served as subjects. The RA and normal control subjects were age and sex matched to the fibromyalgia patients. Subjects were tested for pain tolerance, pain threshold, and noise tolerance and were asked to complete a number of questionnaires that assessed hypervigilance. As predicted, the responses of the fibromyalgia patients to both the pain and auditory stimuli were consistent with the generalized hypervigilance hypothesis. These patients had significantly lower threshold and tolerance values than the RA patients, who in turn, had lower values than the normal control subjects. The results of the psychological questionnaires revealed that the fibromyalgia and RA patients preferred lower levels of external stimulation than the control subjects. The outcome of this study supports the generalized hypervigilance hypothesis, suggesting that fibromyalgia patients have a perceptual style of amplification. The implications of these findings for understanding the role of biological, cognitive, and perceptual factors in pain disorders are discussed.

Adult↗

PubMed2004

Facilitation of A[delta]-fiber-mediated acute pain by repetitive transcranial magnetic stimulation.

BACKGROUND: Repetitive transcranial magnetic stimulation (rTMS) of the motor cortex modulates acute and chronic pain perception. The authors previously showed that rTMS over the primary motor cortex (M1) inhibited capsaicin-induced acute pain ascending through C-fibers. OBJECTIVE: To investigate the effects of 1-Hz rTMS over M1 on acute experimentally induced pain mediated by Adelta-fibers (i.e., another type of acute pain). METHODS: The authors examined whether rTMS over M1 affected laser evoked potentials (LEPs) in 13 normal subjects using thulium: yttrium-aluminum-garnet laser stimulation. Subjective pain-rating scores and LEPs obtained under three different conditions--rTMS, realistic sham stimulation, and a control condition with no stimulation--were compared. RESULTS: The authors found that 1-Hz rTMS over M1 significantly aggravated the subjective pain and enhanced the N2-P2 amplitudes compared with the sham or control sessions. Because the pain-rating scores and the N2-P2 amplitudes correlated positively, the N2-P2 amplitudes in the present study can be regarded as the cortical correlate of subjective pain. CONCLUSIONS: Together with the authors' previous study on C-fiber pain, this facilitatory effect of repetitive transcranial magnetic stimulation on Adelta-fiber-mediated further strengthens the notion of a relationship between repetitive transcranial magnetic stimulation over M1 and pain perception.

Acute Disease↗