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Query: UMLS:C0030193 (pain)
 261,466 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Neuropathic cancer pain may be less responsive to opioids than other pain. Several studies suggest that N-methyl-D-aspartate (NMDA)-receptor antagonists could play a role in the treatment of neuropathic pain. Ketamine is an NMDA-receptor antagonist that is used as an anesthetic and has been suggested as a useful drug for neuropathic pain. Subanesthetic doses of ketamine can yield analgesia without hypnosis. We describe a patient who developed neuropathic cancer pain unresponsive to opioid escalation and spinal administration of a combination of bupivacaine-morphine and was subsequently treated by subcutaneous continuous ketamine infusion. A starting dose of 150 mg/day provided good pain relief and a dramatic reduction of the oral morphine dose (from 5 g to 200 mg). A slow and progressive increase of ketamine and morphine dosage (400 mg and 200 mg by the subcutaneous route, respectively) continued to provide adequate pain relief after 13 months of therapy despite signs of progressive disease.
J Pain Symptom Manage 1995 Oct
PMID:Long-term ketamine subcutaneous continuous infusion in neuropathic cancer pain. 853 99

Pre-emptive analgesia is based on the idea that analgesia initiated before a nociceptive event will be more effective than analgesia commenced afterwards, and that its effects will outlast the pharmacological duration of action of the analgesic used. The idea of pre-emptive analgesia is based upon experimental neurophysiological work demonstrating that afferent nociceptive impulses result in alterations of central nervous system function. These changes, most easily elicited by C-fibre afferents, particularly affect the spinal dorsal horn. Termed central sensitisation, they are reflected by reduced pain thresholds (allodynia), increased responses to pain (hyperalgesia), after-discharging or spontaneous activity of dorsal horn neurons (wind-up), and extension of hypersensitivity to unaffected tissues (secondary hyperalgesia). Their biochemical basis is now being unravelled, with excitatory amino acid (e.g. NMDA) and neuropeptide (e.g. substance P) neurotransmitters playing prominent roles. Blockade of these receptors has recently been shown to depress the central sensitisation associated with nociception. Ketamine, a non-competitive NMDA receptor blocker, for example, has been shown modulate postoperative pain in a positive way. Although the existence of central sensitisation is now being clinically demonstrated, studies of pre-emptive analgesia in the surgical context have not revealed clinically significant effects. This is probably because surgical nociception is much longer-lasting, multimodal and intense than its experimental counterparts. Clinical studies have so far only used short-term analgesia. To permit extrapolation from the experimental to the clinical situation, pre-emption in the surgical context must correspond adequately to the duration and extent of the nociception involved. Studies of pre-emptive analgesia in a clinically relevant form, i.e. where nociception and analgesia are correctly matched, are called for.
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PMID:[Pre-emptive analgesia]. 859 63

Pharmacological praemedication. In patients receiving regional anaesthetics induction of deep sedation prior to the performance of the block should be avoided because during the installation of the nerve block it is an advantage to have a cooperative patient. Adequate anxiolytic effects are achieved by oral administration of chloracepate (0.3-0.5 mg/kg body weight). Intraoperative sedation. Once regional anaesthesia is established deep sedation or even a light sleep might be appropriate to improve the patient's comfort. Short acting i.v. substances are the agents of choice. Propofol (1.5-5 mg/kg per h) and midazolam (0.03-0.09 mg/kg per h) are recommended. Both substances should be titrated as needed. Since respiratory depression or loss of airway patency may occur, close observation and pulse oxymetric monitoring are mandatory. Intraoperative analgesia. Restlessness due to pain is not an indication for sedatives and/or hypnotics. Pain can be caused not only by incomplete regional anaesthesia, but also by a tourniquet or uncomfortable body positions, for example, and it should be treated in different ways according to its cause. In the case of an incomplete block, a catheter technique makes a top-up dose for augmentation possible; additional peripheral nerve blocks can also be used to complete the analgesia. If these attempts are unsuccessful, systemic analgesics (preferable narcotics) or even anaesthetics must be given. Opioids are recommended only in mild to moderate pain or discomfort. The risk of respiratory depression should be considered. The administration of oxygen by mask and pulse oxymetric monitoring are useful. Ketamine is a common drug with a potent analgesic effect, which possesses the advantages of good support for the cardiovascular system, because of its sympathomimetic action, and minimal depression of the ventilatory drive. However, with the exception of a few specific indications, Ketamine is not a drug that is initially an integral part of planned regional anaesthetic procedures. In case of incomplete regional blocks administration of ketamine is more frequently the "ultima ratio" following a number of previous, unsuccessful attempts-primarily with sedatives and/or opioids-to achieve a condition that will permit surgical procedures; as a result, the hypnotic and respiratory depressant effects of subsequently administered drugs are enhanced and potentiated. An important consequence of this complex pharmacodynamic interaction scenario is a potential loss of the advantages that would otherwise be gained by using "subanaesthetic" ketamine doses (< 0.5 mg/kg), namely: a cooperative patient who is breathing spontaneously and has an intact laryngopharyngeal reflex response and, therefore, an uncompromised airway competence. Pulse oxymetric monitoring of the potentially endangered respiratory function is obligatory. The individual transition to general anaesthesia is not easy to determine. Therefore, it is essential that, whenever the need arises, intubation and mechanical ventilation intervention procedures be carried out immediately.
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PMID:[Analgesia and sedation to supplement incomplete regional anesthesia]. 859 70

Ketamine reduces nociception by binding noncompetitively to the N-methyl-D-aspartate (NMDA) receptor, activation of which increases spinal hypersensitivity. We studied 19 healthy, unmedicated male volunteers, aged 20-31 yr. Burn injuries were produced on the medial surface of the dominant calf with a 25 x 50 mm rectangular thermode. On 3 separate days, at least 1 week apart, subjects received a bolus of either ketamine 0.15 mg kg-1, ketamine 0.30 mg kg-1 or placebo, delivered by a mechanical infusion pump over 15 min. The bolus was followed by continuous infusion of ketamine 0.15 mg kg-1 h-1, ketamine 0.30 mg kg-1 h-1 or placebo, respectively, for 135 min. Ketamine reduced the magnitude of both primary and secondary hyperalgesia, and also pain evoked by prolonged noxious heat stimulation, in a dose-dependent manner. In contrast, ketamine did not alter phasic heat pain perception (perception of transient, painful, thermal stimuli) in undamaged skin. The analgesic effects of ketamine in the burn injury model are in agreement with results from experimental studies, and can be distinguished from those of local anaesthetics and opioids. Side effects caused by continuous infusion of ketamine 0.15 and 0.30 mg kg-1 h-1 were frequent but clinically acceptable.
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PMID:Effect of systemic N-methyl-D-aspartate receptor antagonist (ketamine) on primary and secondary hyperalgesia in humans. 867 58

Ten patients (4 female, 6 male) aged 34-67 years suffering from peripheral neuropathic pain participated in a double-blind placebo-controlled study where ketamine or magnesium chloride were administered by a 10 min bolus infusion (ketamine: 0.84 mumol/kg = 0.2 mg/kg, magnesium: 0.16 mmol/kg) followed by a continuous infusion (ketamine: 1.3 mumol/kg/h = 0.3 mg/kg/h, magnesium: 0.16 mmol/kg/h). Ongoing pain determined by VAS score, area of touch-evoked allodynia, detection and pain thresholds to mechanical and thermal stimuli were measured before and during drug infusion. Ketamine produced a significant reduction of spontaneous pain (57%) and of the area of allodynia (33%). Magnesium chloride reduced pain (29%) and area of allodynia (18%) insignificantly. Following ketamine there was a significant correlation between the reduction in ongoing pain and reduction in area of touch-evoked allodynia. Detection and pain thresholds to mechanical and thermal stimuli were not significantly changed by the drugs. These findings suggest that both ongoing pain and touch-evoked pain (allodynia) in neuropathic pain are inter-related phenomena, which may be mediated by the same mechanism and involving a N-methyl-D-aspartate receptor.
Pain 1996 Feb
PMID:NMDA receptor blockade in chronic neuropathic pain: a comparison of ketamine and magnesium chloride. 874 Jun 6

Ketamine has been shown to have potent analgesic properties at low dosages. Bioavailability is high when it is given parenterally, but low after oral or rectal administration. Active metabolites should account for part of the analgesic effect of ketamine during long-term oral administration. NMDA receptor inhibition by ketamine may reflect a wind-down phenomenon, and should alleviate NMDA-related neuropathic pain, reversing the rightward shift of the opioid-response curve. A synergistic effect between ketamine and opioids has been observed in cancer pain patients who have lost an analgesic response to high doses of morphine. Further studies need to be carried out to confirm the benefits of ketamine in cancer pain, and to determine the best route of administration, dosages and the incidence of side effects.
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PMID:Ketamine in cancer pain: an update. 881 93

Ketamine has been used parenterally for pain unresponsive to opioids, including neuropathic pain, and has also been used as an alternative analgesic agent after surgery. Although oral administration of ketamine has been used for some time as a single dose, it has not been given by this route on a regular basis. The use of ketamine administered orally is described for two patients with severe neuropathic pain who were intolerant of, or whose pain was unrelieved by, more commonly used agents. Pain relief was achieved without significant side effects.
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PMID:Ketamine injection used orally. 881 96

Pain intensity was observed before and after the subcutaneous (s.c.) administration of ketamine hydrochloride (80 micrograms/kg/s.c.) or saline (0.9% NaCl given by the same route) in 17 migraine (M) sufferers as an acute treatment of their M attacks. The same parameter was observed in another group of 17 M-sufferers complaining of very severe and frequent M attacks; these subjects were completely refractory to the prophylactic treatments currently used in M. In this second group, ketamine 80 micrograms/kg/s.c./three times a day) or saline was randomly assigned in a short (3-week) chronic treatment. A randomized, double-blind, cross-over study design was used both when testing ketamine as an acute administration for relieving M attack and when comparing its effect to that of the placebo in a chronic treatment for preventing M-pain. Ketamine, but not placebo, produced a marked relief of pain both as an acute treatment and as a prophylactic therapy. Mild specific side-effects were observed in the majority of the patients treated with ketamine. Moreover in the placebo group, the majority of these patients also complained of side-effects. The present results support the hypothesis that N-methyl-D-aspartic acid (NMDA) receptors play an important role in the mechanisms of M.
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PMID:Exploration of NMDA receptors in migraine: therapeutic and theoretic implications. 883 16

The non-competitive NMDA-antagonist, Ketamine, was infused (i.v.) in healthy volunteers to study the effect on central excitability with the presence of cutaneous hyperalgesia. Hyperalgesia was established experimentally on the dorsum of the foot by topical application of capsaicin (1%). Different thermal and mechanical conditioning stimuli were applied to the primary and secondary hyperalgesic areas to modulate the central nociceptive excitability monitored by the nociceptive reflex. When the elicited reflex was combined with an activation of the secondary hyperalgesic area by continuous, non-painful, electrical stimulation, a facilitation of the reflex was observed. This indicates that summation of activity in non-nociceptive and nociceptive afferents can occur under mild pathological conditions. Conditioning thermal stimuli of the primary hyperalgesic area were employed to intensify the allodynia prior to testing this interaction between tactile and nociceptive activity. The same reflex facilitation was inhibited by Ketamine. Furthermore, Ketamine decreased the pain intensity associated with the stimuli eliciting the reflex. Psychophysical measures to single and repeated electrical and thermal (laser) stimuli applied within the hyperalgesic areas were also obtained. The intensity of pain sensations produced by single, painful, electrical stimuli applied to the primary hyperalgesic region was reduced after Ketamine infusion. Finally, five repeated, electrical stimuli applied to the secondary hyperalgesic area were used to assess the temporal summation threshold. Ketamine caused an increase in the summation threshold compared to the placebo treatment. In conclusion, these results demonstrate that (1) summation of activity in non-nociceptive and nociceptive afferents occurs under hyperalgesic conditions and, (2) this summation can be inhibited by NMDA-antagonists. Therefore, the study shows an apparent involvement of NMDA-receptors in some of the central mechanisms underlying secondary hyperalgesia.
Pain 1996 Jul
PMID:The effect of Ketamine on stimulation of primary and secondary hyperalgesic areas induced by capsaicin--a double-blind, placebo-controlled, human experimental study. 885 31

Hyperactivity of N-methyl D-aspartate (NMDA) receptors may be one of the factors in the maintenance of persistent stump and phantom limb pain. Ketamine (bolus at 0.1 mg/kg/5 min followed by an infusion of 7 micrograms/kg/min) was administered intravenously to 11 patients with established stump and phantom limb pain in a double-blind saline-controlled study. All 11 patients responded with a decrease in the rating of stump and phantom limb pain assessed by visual analogue scale (VAS) and McGill Pain Questionnaire (MPQ). Ketamine increased pressure-pain thresholds significantly. Wind-up like pain (pain evoked by repeatedly tapping the dysaesthetic skin area) was reduced significantly by ketamine. In contrast, no effect was seen on pain evoked by repeated thermal stimuli. Side effects were observed in nine patients. The results support the notion that stump and phantom pain are generated by activity in afferent fibres activated by mechanical but not by thermal stimuli and that the NMDA receptor is involved in the maintenance of postamputation pain states. NMDA receptor antagonists may have a potential in the treatment of stump and phantom limb pain.
Pain 1996 Sep
PMID:The effect of ketamine on phantom pain: a central neuropathic disorder maintained by peripheral input. 889 33


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