Joel Katz

Pain ‘memories’ in phantom limbs: review and clinical observations

&NA; This paper reviews reports of phantom limb sensations which resemble somatosensory events experienced in the limb before amputation. It also presents descriptions of this phenomenon in 68 amputees who took part in a series of clinical studies. These somatosensory memories are predominantly replicas of distressing pre‐amputation lesions and pains which were experienced at or near the time of amputation, and are described as having the same qualities of sensation as the pre‐amputation pain. The patients who experience these pains emphasize that they are suffering real pain which they can describe in vivid detail, and insist that the experience is not merely a cognitive recollection of an earlier pain. Reports of somatosensory memories are less common when there has been a discontinuity, or a pain‐free interval, between the experience of pain and amputation. Among the somatosensory memories reported are cutaneous lesions, deep tissue injuries, bone and joint pain and painful pre‐amputation postures. The experience of somatosensory memories does not appear to be related to the duration of pre‐amputation pain, time since amputation, age, gender, prosthetic use, level of amputation, number of limbs amputated, or whether the amputation followed an accident or illness. The results suggest that somatosensory inputs of sufficient intensity and duration can produce lasting changes in central neural structures which combine with cognitive‐evaluative memories of the pre‐amputation pain to give rise to the unified experience of a past pain referred to the phantom limb. Implications for pre‐ and post‐operative pain control are discussed.

Central Neuroplasticity and Pathological Pain

Abstract: 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.

The role of compensation in chronic pain: Analysis using a new method of scoring the McGill pain questionnaire

&NA; Patients who receive workers compensation or are awaiting litigation after an accident have long been regarded as neurotics or malingerers who are exaggerating their pain for financial gain. However, there is a growing body of evidence that patients who receive workers compensation are no different from patients who do not. In particular, a recent study found no differences between compensation and non‐compensation patients based on pain scores obtained with the McGill Pain Questionnaire (MPQ). Since the MPQ is usually scored by using rank values rather than more complex scale values, the negative finding might be attributable to the loss of information by using rank values. Consequently, a simple technique was developed to convert rank values to weighted‐rank values which are equivalent to scale values. A study of 145 patients suffering low‐back and musculoskeletal pain revealed that compensation and non‐compensation patients had virtually identical pain scores and pain descriptor patterns. They were also similar on the MMPI pain triad (depression, hysteria, hypochondriasis) and on several other personal variables that were examined. The only differences were significantly lower affective or evaluative MPQ scores and fewer visits to health professionals by compensation patients compared to non‐compensation patients. These results suggest that the financial security provided by compensation decreases anxiety, which is reflected in the lower affective or evaluative ratings but not the sensory or total MPQ scores. Compensation patients, contrary to traditional opinion, appear not to differ from people who do not receive compensation. Accidents which produce injury and pain should be considered as potentially psychologically traumatic as well as conducive to the development of subtle physiological changes such as trigger points. Patients on compensation or awaiting litigation deserve the same concern and compassion as all other patients who suffer chronic pain.

Referred sensations in chronic pain patients

This clinical note describes an unusual phenomenon of referred sensation reported in a sample of 98 chronic pain patients during electrical stimulation. Thirty-nine percent reported a variety of sensations referred to different parts of the body. Of these, 74% reported the sensations referred to the painful region. Among the sensations were paresthesias, pain, temperature changes, and pressure or constriction. The patients who had referred sensations had lower ratings of depression and had undergone more surgical operations than those who did not report referred sensations. Three case reports of patients with phantom limb pain are presented to illustrate the vividness with which these sensations are experienced. These data suggest that deafferentation due to disease, injury or other lesions of the CNS lead to a hypersensitivity and an increased likelihood of referred pain of long duration.

Intravenous meperidine for control of shivering during Caesarean section under epidural anaesthesia

To determine the efficacy of meperidine in controlling shivering during epidural anaesthesia for Caesarean section, forty-six parturients were studied. After delivery of the infant, shivering patients received either a single dose of intravenous meperidine 50 mg, or saline in a randomized double-blind fashion. Shivering was classified on a scale of 0 to 3 (grade 0 = none, grade 3 = severe shivering that was distressing to the patient and interfered with monitoring). Shivering and other variables were recorded at epidural placement, skin incision, delivery, and 2,5,15,30 and 60 minutes following injection. Administration of meperidine resulted in a significant decrease in both the overall incidence of shivering (87 to 35 per cent, p < 0.0 J) and severity of shivering (grade 3: 57 to 0 per cent, p < 0.01), compared with saline (incidence: 87 to 83 per cent, grade 3:57 per cent, no change). This effect was apparent within two minutes of drug injection and persisted throughout the study period. There were no differences in vital signs, oxygen saturation or temperature between groups. The incidence of nausea was similar, although patients receiving meperidine were more drowsy at two and five minutes following injection (p < 0.01) compared with patients in the saline group. There were no differences in level of consciousness at the later intervals. The mechanism of action of meperidine on shivering remains to be elucidated.RésuméAfin de déterminer ľefficacité de la mépéridine dans le contrôle des frissons lors ďune anesthésia épidurale pour césarienne, 46 parturientes ont été étudiées. Après ľccouchement de ľenfant, les patientes avant frissonné ont reçu à double insu soit une dose unique intraveineuse de mépéridine 50 mg ou du salin après randomisation. Les frissons ont été classifiés selon une échelle de 0 à 3 (grade 0 = aucun, grade 3 = frisson sévère qui était inconfortable pour la patiente et interférant avec la surveillance). Les frissons ainsi que ďautres variables ont été enregistrés lors de la mise en place de ľépidurale, ľincision, ľaccouchement, età 2, 5, 15, 30 et 60 minutes après ľinjection, ľadministration de mépéridine provoqua une diminution significative de ľincidence totale des frissons (87 à 35 pour cent, p < 0.01) ainsi que de la sévérité des frissons (grade 3: 57 à Opourcent,p <0.01), comparativement au salin (incidence: 87 â 83 pour cent, grade 3:57 pour cent, aucun changement). Cet effet était apparent en dedans de deux minutes après ľinjection du médicament et persista tout le long de ľétude. II n’y avait aucune différence dans les signes vitaux, la saturation ďoxygène ou la température entre les groupes. Ľincidence des nausées était identique même si les patientes avant reçu la mépéridine étaient plus somnolentes à 2 et 5 minutes après ľinjection (p < 0.01) comparativement au groupe salin. II n’y avait aucune différence dans le niveau de conscience aux autres phases de ľétude. Le mécanisme ďaction de la mépéridine sur les frissons demeure à être élucidé.

An association between phantom limb sensations and stump skin conductance during transcutaneous electrical nerve stimulation (TENS) applied to the contralateral leg: a case study

This report describes a placebo-controlled study of transcutaneous electrical nerve stimulation (TENS) applied to the contralateral lower leg and outer ears of an amputee with non-painful phantom sensations. The subject received TENS or placebo stimulation on separate sessions in which baseline periods of no stimulation alternated with periods of TENS (or placebo). Throughout the two sessions, continuous measures of stump skin conductance, surface skin temperature and phantom intensity were obtained. The results showed that TENS applied to the contralateral leg was significantly more effective than a placebo in decreasing the intensity of phantom sensations, whereas stimulation of the outer ears led to a non-significant increase. The pattern of electrodermal activity on the TENS session was consistently linear during baseline periods, indicating a progressive increase in sympathetic sudomotor activity. In contrast, during periods of electrical stimulation the pattern of electrodermal activity was consistently curvilinear indicating an initial decrease followed by an increase in sudomotor responses. Changes in stump skin conductance correlated significantly with changes in phantom sensations both in TENS and placebo sessions suggesting a relationship between sympathetic activity at the stump and paresthesias referred to the phantom. Two hypotheses are presented to account for these findings.

The role of intrathecal morphine in the anesthetic management of patients undergoing coronary artery bypass surgery

The study was undertaken to assess the effects of intrathecal morphine (ITM) on perioperative hemodynamics, and anesthetic and postoperative analgesic requirements in patients anesthetized with fentanyl/enflurane undergoing coronary artery bypass surgery. Forty patients were randomized in a double-blind fashion to receive either intrathecal morphine or saline. Nineteen patients received ITM, 0.02 mg/ kg, and 21 intrathecal saline (ITS) after induction of anesthesia. Anesthesia included fentanyl, 40 microg/kg, and pancuronium, 0.15 mg/kg, and was supplemented with enflurane when systolic blood pressure was 20% higher than ward pressure. Intrathecal morphine did not improve hemodynamic stability or reduce enflurane requirements perioperatively. No significant difference was found between ITM and ITS groups for postoperative requirements of morphine (3.5 +/- 0.5 v 4.5 +/- 0.6 mg), diazepam (5.6 +/-1.25 v 3.9 +/- 1.26 mg), and vasodilators (6 v 13 patients), respectively. Comparable and significant reductions of peak expiratory flow rates (PEFR), forced vital capacity (FVC), and forced expiratory volume (FEV1) occurred in both groups postextubation when compared with preoperative values. Intrathecal morphine at the dose of 0.02 mg/kg does not offer any clear benefit to patients anesthetized with fentanyl, 40 microg/kg, for coronary artery bypass surgery.

Symptom prescription: A review of the clinical outcome literature

Abstract The concept of symptom prescription is introduced and defined with examples. The clinical outcome literature on the use of symptom prescription as a therapeutic technique designed to facilitate symptom reduction is reviewed. It is concluded that prescribing the symptom is an effective technique for individuals complaining of sleep onset insomnia. In especially resistant cases, symptom prescription may prove to be the treatment of choice. Generally positive results have also been demonstrated for other disorders that are also characterized by high levels of anxiety, including functional urinary and bowel disorders, agoraphobia, and obsessive thoughts. Two hypotheses are presented, which attempt to explain how symptom prescription facilitates therapeutic change. Finally, some implications of symptom prescription for psychotherapy research and practice are briefly examined.

Pain and Neuroplasticity

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 pre-emptive 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 behavioural 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.

Evaluación del dolor en pacientes adultos

El dolor es una experiencia personal y subjetiva que comprende una serie de dimensiones, como la sensitiva-discriminativa, la afectiva-emocional y la cognitiva-evaluativa. Existen diferentes procedimientos para la medicion y la evaluacion del dolor: escalas de puntuacion verbales y numericas, escalas visuales analogicas, escalas de observacion conductual y evaluacion de la respuesta fisiologica. La naturaleza compleja de la experiencia del dolor hace que el grado de concordancia de las mediciones que se realizan en los diferentes dominios no sea siempre elevada.