Articles: hyperalgesia.
-
Traumatic nerve injury in man can often result in the development of neuropathy. An animal model of neuropathic hyperalgesia is produced by loose ligation of the sciatic nerve in the rat. We have examined the effect of pre-emptive treatment with a number of drugs on the development of hyperalgesia in this model. ⋯ In vehicle-treated animals the ipsilateral paw withdrawal threshold (118 +/- 7 g) was significantly lower (P < 0.0001, paired t-test) than the contralateral (195 +/- 7 g). In contrast, in animals pre-treated with clonidine no significant difference between ipsilateral (200 +/- 9 g) and contralateral (191 +/- 7 g) paw withdrawal thresholds was detected. Morphine pre-treatment was less effective in preventing development of hyperalgesia; however, whilst the ipsilateral (146 +/- 18 g) paw withdrawal threshold tended to be lower than the contralateral (183 +/- 8 g), this was not significant.(ABSTRACT TRUNCATED AT 250 WORDS)
-
Thermal hyperalgesia was induced by UV irradiation of the glabrous skin of the hindpaw of adult female Sprague-Dawley rats. We have recorded single cell activity and studied excitability changes in wide dynamic range neurons in the lumbar spinal segments during the early phase (days 1-3) and late phase (days 5-7) of thermal hyperalgesia in animals under urethane anaesthesia. The proportion of spontaneously active wide dynamic range cells was increased following UV irradiation and the degree of spontaneous activity was enhanced during the course of hyperalgesia. ⋯ Cutting the dorsal roots (L2-5) evoked a significantly larger and more prolonged discharge in wide dynamic range cells in both UV-treated groups in comparison to control. Spontaneous activity in spinal wide dynamic range neurons was reduced after rhizotomy in each group. However, the decrease was only significant at days 1-3 (P < 0.05) but not at days 5-7.(ABSTRACT TRUNCATED AT 250 WORDS)
-
Randomized Controlled Trial Clinical Trial
Secondary hyperalgesia is not affected by wound infiltration with bupivacaine.
The purpose of this study was to determine the effects of wound infiltration with bupivacaine on incisional pain and the zone of secondary hyperalgesia. Twenty-eight healthy parturients were studied in a double-blind randomized trial. At the time of Caesarean section one wound edge was infiltrated with saline 0.9% and the other with bupivacaine 0.25%. ⋯ The zone of secondary pain was similar overall for both sides of the wound. It is concluded that the bupivacaine-infiltrated side of the wound was less painful than the saline-injected side 24 hr postoperatively. The zone of pain measured around the wound edges was unaffected by bupivacaine or saline.
-
Case Reports
Hyperalgesia and myoclonus in terminal cancer patients treated with continuous intravenous morphine.
Eight cancer patients in the terminal stages of the disease treated with high doses of intravenous morphine developed hyperalgesia. All cases were retrospectively sampled from three different hospitals in Copenhagen. ⋯ Although only few clinical descriptions of the relationship between hyperalgesia/myoclonus and high doses of morphine are available, experimental support from animal studies indicates that morphine, or its metabolites, plays a causative role for the observed behavioural syndrome. The possible mechanisms are discussed and treatment proposals given suggesting the use of more efficacious opioids with less excitatory potency in these situations.
-
The spectrum of perioperative pain treatment is discussed in the present review. The analgesic efficacy of various drugs and the dosage methods of administration and side effects reported for them in such reference works as the practical guide on the management of acute pain recently published by the International Association for the Study of Pain (IASP) are described. Effective postoperative analgesia can diminish stress reactions following surgery. ⋯ Investigations performed by the author of this review have shown that epidural infusion of highly diluted mixtures of bupivacaine/fentanyl is highly effective in the analgesic treatment of patients undergoing prostatectomy, providing excellent physical mobilization. The potential dangers of drug combinations and contraindications are also discussed. The concept of using balanced analgesia to induce additive or synergistic effects following the administration of analgesic drugs requires further clinical studies.