Biomedical subjects
Publications and source records attributed to Crawford W Clark.
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The purpose of this study was to validate the content and structure of the Multidimensional Affect and Pain Survey (MAPS) by means of factor analysis. The 101-MAPS is based on a dendrogram obtained by cluster analysis and contains 30 clusters subsumed within three superclusters. If the MAPS is a valid questionnaire for the quantification of emotion and pain in patients, then factor analysis of patients' intensity ratings should produce factors which correspond to the cluster structure of the dendrogram. To confirm the structure of the dendrogram and hence, MAPS, factor analysis was applied to the responses by 100 outpatients diagnosed with early stage cancer. Principal components analysis of responses to the MAPS yielded six factors. In accordance with the hypothesis, 13 of the 17 clusters within the MAPS somatosensory pain supercluster loaded on three sensory factors: factor 1, severe sensory pain; factor 3, moderate sensory pain; and factor 6, numb/cold. Five of the eight clusters within the emotional pain supercluster loaded on factor 2, negative emotions. Four of the five clusters in the well-being supercluster loaded on factor 4, good health. Factor 5, manageable illness was loaded on by clusters from the well-being supercluster and the somatosensory pain supercluster. The homogeneity of the six factors found demonstrate the validity of the MAPS and the cluster structure of the dendrogram. MAPS proved sensitive to sex differences; women endorsed the negative emotions factor more strongly than did men. The MAPS factors were much more homogeneous than those reported in the literature for the McGill Pain Questionnaire.
Pain is now regarded as 'the fifth vital sign' and patients are frequently asked to score the intensity of their pain on a numerical pain rating scale (NPRS). However, the use of a unidimensional scale is questionable in view of the belief, overwhelmingly supported by clinical experience as well as by empirical evidence from multidimensional scaling and other sources, that pain has at least two dimensions: somatosensory qualities and affect. We used a Chinese translation of the 101 descriptor multidimensional affect and pain survey (MAPS) questionnaire to determine the relative contributions of various dimensions of postoperative pain to a patient's score on a unidimensional NPRS. MAPS and NPRS were administered postoperatively to 69 patients with descending colon carcinoma who were recovering from left hemi-colectomy. Multiple linear regression revealed that the emotional pain qualities supercluster (P=0.0005) and four of its eight subclusters, anxiety, depressed mood, fear and anger, significantly (P=0.001-0.007) predicted a patient's score on the unidimensional NPRS. Notably, none of the 17 subclusters in the somatosensory pain qualities supercluster predicted NPRS scores. It may be concluded that patient scores on unidimensional pain intensity scales reflect the emotional qualities of pain much more than its sensory intensity or other qualities. Accordingly such scales are poor indicators of analgesic requirement. The results also suggest that patients' postoperative anxiety and depression are inadequately treated. Based on our findings we present six unidimensional scales that should yield a more accurate assessment of the sources of a patient's pain.
Although the cause of silent myocardial ischemia (SMI) is unknown, several theories have been advanced to explain the disorder. Most prominent among these are the suggestions that attribute the condition to generalized impaired pain sensitivity and/or enhanced endorphin activity. The present study examined both hypotheses. It was carried out in 33 patients with myocardial ischemia: 13 with silent myocardial ischemia (silents) and 20 with symptomatic ischemia (symptomatics). Pain sensitivity was determined with thermal, electrical, and ischemic pain tests using signal detection theory (SDT) and conventional threshold procedures. To evaluate the significance of endorphin mechanisms naloxone (6 mg i.v.) and placebo were administered on alternate days in a double-blind, cross-over procedure before the pain tests and again before a treadmill exercise test (TET). Somatic pain sensitivity was found not to be impaired in patients with SMI, and no evidence was found to support a causal role for endorphins in the disorder.
Anecdotal and clinical reports suggest that athletes are stoical. However, there are few studies comparing persons who exercise regularly with those who do not. This study compared two independent samples of regular runners and normally active controls, both without recent exercise, on cold pressor, cutaneous heat, and tourniquet ischemic pain tests. Results demonstrated that the runners' threshold for noxious cold was significantly higher than that of controls. The heart rate and blood pressure responses to cold were similar in the 2 groups, suggesting that differences in cold pain report did not result from differences in autonomic reactivity to cold. Signal detection theory measures demonstrated that runners discriminated among noxious thermal stimuli significantly better than controls, but neither noxious nor innocuous thermal report criteria differed between groups. The cohorts also did not differ in their report of ischemic pain sensations. Thus, these data do not generally support the hypothesis of pain insensitivity or stoicism in habitual runners. Rather, insensitivity occurs only in their response to noxious cold, which is suggested to be an adaptation to regular training.
This paper presents a new approach to the measurement and understanding of clinical pain. A multidimensional scaling (MDS) procedure was used to analyze pairwise similarity judgments made to 9 pain descriptors by 24 cancer pain patients and 24 healthy volunteers. The question was whether the dimensions of the global pain space differed between the 2 groups. The Pain Intensity dimension was found to be primary for the patients, but much less important for the volunteers. Otherwise, the group stimulus space revealed broadly similar 3-dimensional solutions. The Pain Intensity dimension placed Mild Pain and Annoying at one pole and Intense and Unbearable Pain at the other. The Emotional Quality dimension grouped the descriptors Sickening and Miserable (and, in part, Intense Pain and Unbearable Pain) at the strong negative affect pole for both groups; they differed, however, with respect to the moderate affect pole. The Somatosensory dimension ranged from Burning to Cramping. The subject weight space revealed that the Pain Intensity dimension was the most important dimension for the patients, while Emotional Quality was more salient for the volunteers. Wide differences were found in the salience of the various dimensions to different individuals; this information may prove useful for tailoring patient treatment. The study demonstrates that MDS procedures such as INDSCAL, in which the subjects (rather than the researcher) determine the number and characteristics of the global pain dimensions, will improve our understanding and treatment of pain.
The effects of intense exercise on pain perception, mood, and plasma endocrine levels in man were studied under naloxone and saline conditions. Twelve long-distance runners (mean weekly mileage = 41.5) were evaluated on thermal, ischemic, and cold pressor pain tests and on mood visual analogue scales (VAS). Blood was drawn for determination of plasma levels of beta-endorphin-like immunoreactivity (BEir), growth hormone (GH), adrenocorticotrophic hormone (ACTH), and prolactin (PRL). These procedures were undertaken before and after a 6.3 mile run at 85% of maximal aerobic capacity. Subjects participated on two occasions in a double-blind procedure counterbalanced for drug order: on one day they received 2 i.v. injections of naloxone (0.8 mg in 2 ml vehicle each) at 20 min intervals following the run; on the other day, 2 equal volume injections of normal saline (2 ml). Sensory decision theory analysis of the responses to thermal stimulation showed that discriminability, P(A), was significantly reduced post-run under the saline condition, a hypoalgesic effect; response bias, B, was unaffected. Ischemic pain reports were significantly reduced post-run on the saline day, also a hypoalgesic effect. Naloxone reversed the post-run ischemic but not thermal hypoalgesic effects. Joy, euphoria, cooperation, and conscientiousness VAS ratings were elevated post-run; naloxone attenuated the elevation of joy and euphoria ratings only. Plasma levels of BEir, ACTH, GH, and PRL were significantly increased post-run. The results show that long-distance running produces hypoalgesia and mood elevation in man. The effects of naloxone implicate endogenous opioid neural systems as mechanisms of some but not all of the run-induced alterations in mood and pain perception.