Methods of postoperative pain control.
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Bupivacaine↗
Biomedical subjects
R Melzack
Publications and source records attributed to R Melzack.
Central neural mediators of secondary hyperalgesia following heat injury in rats: neuropeptides and excitatory amino acids.
The contribution of C-fiber neuropeptides and excitatory amino acids (EAAs) as central mediators of secondary hyperalgesia was assessed by examining the effects of intrathecal (i.t.) administration of receptor-selective agonists and antagonists on foot-withdrawal latencies (from 48 degrees C water), both before and after heat injury of the contralateral hindpaw. The hyperalgesia which develops in the hindpaw contralateral to a heat injury, could be reproduced in uninjured rats following i.t. injection of substance P, neurokinin A and N-methyl-D-aspartate (NMDA) but not following calcitonin gene related peptide (CGRP), neurokinin B, kainate or (R,S)-alpha-amino-3-hydroxy-5-methylisozazole-4-propionic acid hydrobromide (AMPA). Contralateral hyperalgesia was reversed by the substance P antagonist Arg1,D-Pro2,D-Phe2-D-His9-substance P, and the NMDA receptor antagonist D-2-amino-5-phosphonovalerate (APV), but not by the non-NMDA EAA antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX). When the limb of the injured hindpaw was pretreated with the C-fiber neurotoxin capsaicin, hyperalgesia in the contralateral hindpaw was unaffected. Furthermore, prior to injury, the capsaicin pretreatment itself produced hyperalgesia in the contralateral hindpaw. The results give support for a contribution of both C-fiber neuropeptides and EAAs to central nervous system plasticity and secondary hyperalgesia following heat injury.
2-Amino-5-phosphonovalerate↗
The role of the cingulum bundle in self-mutilation following peripheral neurectomy in the rat.
Peripheral neurectomy in rats is followed by self-mutilation of the denervated zone (autotomy), which is assumed to represent an index of pain or dysesthesia associated with deafferentation. This study examines the role of the cingulum bundle in mediating autotomy behavior. Rats were given bilateral injections of 1 microliter of 0.5% bupivicaine (a local anesthetic) or saline into the cingulum bundle immediately prior to, and on Days 1, 7, 14, and 21 after, sectioning the sciatic and saphenous nerves. Bupivicaine injections into the cingulum produced a significant delay in the onset of self-mutilation and reduced the overall degree of autotomy. Furthermore, the delayed onset of autotomy exceeded the duration of the anesthetic block produced by bupivicaine.
Afferent Pathways↗
Labor pain: effect of maternal position on front and back pain.
The purpose of this study was to determine whether women in labor report less pain when they are in a vertical (sitting or standing) position than in a horizontal (side-lying or supine) position. Pain scores were obtained from 60 women in early labor (dilation 2-5 cm) who alternated between the two positions. The results show that about 35% of women feel less front pain and 50% feel less back pain when they are in a vertical position than in a horizontal position. The decrease in continuous back pain (83%) was particularly impressive, but the front and back pains associated with contractions were significantly diminished as well. These results, taken together with those of earlier studies, indicate that many women in early labor have less pain and are generally more comfortable in a vertical than in a horizontal position. Since early labor comprises a substantial proportion of the entire process of labor and delivery, any simple procedure which alleviates pain without danger to mother or child, such as shifting from a horizontal to a vertical position, should be promoted and employed.
Adolescent↗
Pain and paresthesia in patients with healed burns: an exploratory study.
The present study was designed to examine the prevalence and characteristics of painful and paresthetic sensations in a group of patients with healed burns. Adult patients who had been hospitalized for burn injuries during a 7-yr period were contacted and given a structured interview that included a series of questions about their present condition. Patients' medical charts were reviewed to obtain relevant demographic and medical information. The results show that abnormal sensations in healed burns are frequently reported as long as several years after the injury. Of 104 patients interviewed 1 yr or more after a burn injury, 82% reported paresthetic sensations such as tingling, stiffness, cold sensations, and numbness; and 35% complained of pain in the scarred tissue. The prevalence of these sensations was not related to age, sex, or etiology of the burns, but was associated with burn size and skin grafting. The theoretical and clinical implications of these results are discussed with particular emphasis on the need to pursue research on the long-term adverse effects of burn injuries.
Adult↗
Auricular transcutaneous electrical nerve stimulation (TENS) reduces phantom limb pain.
The present paper evaluates the efficacy of low frequency, high intensity auricular transcutaneous electrical nerve stimulation (TENS) for the relief of phantom limb pain. Auricular TENS was compared with a no-stimulation placebo condition using a controlled crossover design in a group of amputees with (1) phantom limb pain (Group PLP), (2) nonpainful phantom limb sensations (Group PLS), and (3) no phantom limb at all (Group No PL). Small, but significant, reductions in the intensity of nonpainful phantom limb sensations were found for Group PLS during the TENS but not the placebo condition. In addition, 10 min after receiving auricular TENS, Group PLP demonstrated a modest, yet statistically significant decrease in pain as measured by the McGill Pain Questionnaire. Ratings of mood, sleepiness, and anxiety remained virtually unchanged across test occasions and sessions, indicating that the decrease in pain was not mediated by emotional factors. Further placebo-controlled trials of auricular TENS in patients with phantom limb pain are recommended in order to evaluate the importance of electrical stimulation parameters such as pulse width and rate, and to establish the duration of pain relief.
Adult↗
The Charles Bonnet syndrome: 'phantom visual images'.
The Charles Bonnet syndrome is a condition in which individuals experience complex visual hallucinations without demonstrable psychopathology or disturbance of normal consciousness. An analysis of the sixty-four cases described in the literature reveals that the syndrome can occur at any age though it is more common in elderly people. Reduction in vision, due to peripheral eye pathology as well as pathology within the brain, is associated with the syndrome. Individual hallucinatory episodes can last from a few seconds to most of the day. Episodes can occur for periods of time ranging from days to years, with the hallucinations changing both in frequency and in complexity during this time. The hallucinations may be triggered or stopped by a number of factors which may exert their effect through a general arousal mechanism. People, animals, buildings, and scenery are reported most often. These images may appear static, moving in the visual field, or animated. Emotional reaction to the hallucinations may be positive or negative. Several theories have been proposed to account for the hallucinations. This paper highlights the sensory deprivation framework, with particular emphasis on the activity in the visual system after sensory loss that produces patterns of nerve impulses that, in turn, give rise to visual experience.
Brain Damage, Chronic↗
Injury prior to neurectomy alters the pattern of autotomy in rats. Behavioral evidence of central neural plasticity.
A common property of phantom limb pain is that a preamputation lesion continues to be felt in the same location of the phantom limb after amputation. A model of the phantom limb in the rat is provided by sectioning the sciatic and saphenous nerves. This procedure leads to self-mutilation of the denervated hindpaw, a behavior known as autotomy. There is strong evidence that autotomy is a response to painful or dysesthetic sensations referred to the anesthetic limb. The present study examined the hypothesis that the site of autotomy behavior can be altered by an injury given prior to denervation. Experiment 1 evaluated the effects of a thermal injury applied (under sodium pentobarbital anesthesia) to the medial or lateral hindpaw and digits before or after sciatic and saphenous nerve transections in order to determine whether autotomy is directed specifically to a previously injured site. The results revealed that autotomy onset occurred in the injured region of the paw in a significantly greater proportion of rats, compared to an uninjured control group, if the thermal injury had been induced before denervation: 100% of the rats with medial paw injury induced prior to neurectomy initiated autotomy in the medial digits, and 55.6% of rats with lateral paw injury initiated autotomy in the lateral digits. Rats injured after autotomy showed no such preference (medial, 33.3% and lateral, 37.5%) relative to the uninjured controls (medial, 33.3% and lateral, 17%). These results suggest that central cells, sensitized by the thermal injury, contribute to enhanced autotomy in the absence of further inputs from the injured paw.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Sensory and pharmacological modulation of pain.
Traditional neurosurgical methods to control pain have been replaced by a variety of modulation techniques. The major types of modulation are pharmacological, physical, and psychological. Important advances are occurring in the development of all three modulation approaches.
Humans↗
Central nervous system plasticity in the tonic pain response to subcutaneous formalin injection.
Evidence is presented which suggests that central neural changes occur during the brief early phase after subcutaneous formalin injection that are essential for the expression of pain during the long-lasting (tonic) later phase. First, tonic pain responses to subcutaneous formalin injections are abolished only if the injected hindpaw is locally anesthetized at the time of injection as well as the time of testing (30-60 min later). Second, tonic formalin pain is substantially reduced by brief spinal anesthesia given 5 min before, but not 5 min after the formalin injection.
Animals↗
Phantom limbs and the concept of a neuromatrix.
The phenomenon of a phantom limb is a common experience after a limb has been amputated or its sensory roots have been destroyed. A complete break of the spinal cord also often leads to a phantom body below the level of the break. Furthermore, a phantom of the breast, the penis, or of other innervated body parts is reported after surgical removal of the structure. A substantial number of children who are born without a limb feel a phantom of the missing part, suggesting that the neural network, or 'neuromatrix', that subserves body sensation has a genetically determined substrate that is modified by sensory experience.
Humans↗
The tragedy of needless pain.
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Administration, Oral↗
Different alpha-receptor subtypes are involved in clonidine-produced analgesia in different pain tests.
Dose-response curves for clonidine-produced analgesia in rats were constructed using the tail-flick and formalin tests. Subsequently, the relative role of alpha 1 and alpha 2 receptors in clonidine analgesia in each of these tests was determined using systemic administration of vehicle controls, tolazoline, yohimbine and prazosin prior to injection of an ED50 dose of clonidine. Clonidine was found to be significantly more potent in the formalin test than in the tail-flick test. Furthermore, clonidine analgesia in the tail-flick test was completely antagonized by tolazoline and yohimbine, but not by prazosin, whereas clonidine was antagonized by tolazoline and prazosin, but not by yohimbine in the formalin test. The implications of these findings with regard to the contributions of different alpha-receptor subtypes to clonidine-produced analgesia in different pain tests are discussed.
Analgesics↗
Measurement of nausea.
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Antineoplastic Agents↗
The pain of burns: characteristics and correlates.
This study examined the characteristics of pain experienced by burned patients. Sources of inter-individual variations were also studied and the interrelationships between anxiety, depression, and pain were investigated. Forty-two adult patients hospitalized for burn injuries participated in the study. The McGill Pain Questionnaire and a visual analogue scale were employed to measure the pain experienced at rest and during therapeutic procedures. Anxiety and depression levels were assessed with the Spielberger State Anxiety Inventory, the Beck Depression Inventory, and visual analogue scales. The results showed that the pain varies greatly from patient to patient and undergoes wide fluctuations over time in each patient. The greatest pain is usually experienced during therapeutic procedures, the patients reporting significantly more pain on these occasions than at rest. Variations in pain severity were not related to socio-demographic characteristics of the patients, the length of time elapsed since the injury, or the quantity of analgesics administered. The extent of the burns was a significant predictor of pain but only in the first week after the injury. High levels of anxiety or depression were not necessarily associated with higher pain scores during therapeutic procedures but the patients who were more anxious or depressed tended to report more pain when at rest. These results are discussed in relation to pain management strategies, with particular emphasis on the need for the analgesic therapy to be highly individualized and frequently adjusted.
Adolescent↗
Systemic administration of naloxone produces analgesia in BALB/c mice in the formalin pain test.
Systemic administration of naloxone usually produces either hyperalgesia or no change in nociception depending on the animal species used and/or the pain test employed. This study, however, demonstrates that naloxone produces a dose-dependent analgesia in the formalin pain test using an inbred strain of albino mouse. Female BALB/c, C57BL/6 and CD1 mice were injected subcutaneously with naloxone HCl in saline (0.1 10.0 mg/kg) or saline alone, and tested for analgesia using the formalin test. Naloxone produced a statistically significant dose-dependent analgesia in the BALB/c mice, with an ED50 of 0.24 mg/kg and almost total analgesia at doses of 1 mg/kg or greater. No changes in pain behaviour were observed in the C57BL/6 or CD1 strains of mice. We believe this to be the first report of analgesia following administration of doses of naloxone normally used for opioid antagonism. To determine if this effect was specific to the formalin test, the 3 strains of mice were injected subcutaneously with naloxone HCl and tested in the tail-flick test. Naloxone had no analgesic action in this test in any of the strains.
Analgesia↗
The International Pain Foundation: meeting a need for education in pain management.
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Humans↗
Cutaneous hyperalgesia: contributions of the peripheral and central nervous systems to the increase in pain sensitivity after injury.
This study assesses the contributions of the peripheral and central nervous systems in the development of hyperalgesia (increased pain sensitivity) after an injury. Experiments were carried out to examine the role of C-fiber afferents, the spinal cord and sympathetic efferents on inflammation, primary hyperalgesia and referred hyperalgesia produced in rats by a heat injury. A peripheral mechanism was indicated since both primary hyperalgesia and inflammation after a heat injury were significantly attenuated by blocking C-fiber afferents with local capsaicin. In addition, a central mechanism was indicated since the spread of hyperalgesia to the paw contralateral to a heat injury was prevented by either spinal anesthesia or the blocking of sympathetic efferents by guanethidine. A further role for central mechanisms was indicated since referred hyperalgesia--the enhancement of self-mutilation (autotomy) of a denervated limb which had previously sustained a heat injury--was reduced by spinal anesthesia or a combined blocking of C-fiber afferents and sympathetic efferents with intrathecal capsaicin + guanethidine. The results strongly suggest that referred hyperalgesia after a heat injury is dependent on increased spinal cord activity. However, autotomy in rats that did not undergo a previous injury was unaffected by either spinal anesthesia or intrathecal capsaicin. This suggests that spinal cord hyperactivity, although it plays a role in hyperalgesia following a heat injury, is not a crucial factor in producing pain and hyperalgesia after a nerve injury.
Animals↗