Transient heat hyperalgesia during resolution of ropivacaine sciatic nerve block in the rat.
Reg Anesth Pain Med
; 36(3): 220-4, 2011.
Article
em En
| MEDLINE
| ID: mdl-21451438
ABSTRACT
BACKGROUND:
Preliminary studies using perineural sciatic ropivacaine in rat demonstrated unexpected heat hyperalgesia after block resolution. To better characterize the time course relative to mechanical anesthesia-analgesia, we tested the hypothesis that ropivacaine 0.5% leads to transient heat hyperalgesia in rats independent of mechanical nociception. We also evaluated functional toxicity (eg, long-term hyperalgesia and/or tactile allodynia 2 weeks after injection).METHODS:
Under surgical exposure, left sciatic nerve block was performed in 2 groups of adult male rats-ropivacaine (200 µL, 5 mg/mL; n = 14) versus vehicle (n = 11). The efficacy and duration of block were assessed with serial heat, mechanical (Randall-Selitto testing), and tactile (von Frey-like monofilaments) tests; motor-proprioceptive (rotating rod) and sedation tests were used at 1 and 7 hrs after injection. The presence of nerve injury was assessed by repeating the heat, tactile, and motor tests 12 to 14 days after injection.RESULTS:
Ropivacaine-induced anesthesia was fully manifest at 1 hr after injection. At 3 hrs after injection, heat hypersensitivity was present in the setting of resolved mechanical analgesia. All behavioral measures returned to baseline by 2 weeks after injection. There was no evidence of (i) behavioral sedation, (ii) persistent changes in heat or mechanical sensitivity, or (iii) persistent changes in proprioceptive-motor function at 12 to 14 days after injection.CONCLUSIONS:
Ropivacaine 0.5% induces transient heat hyperalgesia in the setting of resolved mechanical analgesia, further suggestive of modality and/or nociceptive fiber specificity. Whether this finding partially translates to "rebound pain" after patients' nerve blocks wear off requires further study.
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Base de dados:
MEDLINE
Assunto principal:
Nervo Isquiático
/
Bloqueio Nervoso Autônomo
/
Tato
/
Amidas
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Temperatura Alta
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Hiperalgesia
Idioma:
En
Ano de publicação:
2011
Tipo de documento:
Article