RESUMO
Epidural administration of bupivacaine and meperidine produces analgesia in several animal species and in humans. A prospective randomized study was conducted in 18 healthy horses to compare the effect of these 2 drugs administered by the epidural route. Animals were divided into 3 treatment groups of 6 animals each. All drugs were injected by the epidural route in all animals between the 1st and 2nd coccygeal vertebrae. Treatment 1 (BUP)--0.06 mg/kg of body weight of 0.5% hyperbaric bupivacaine; treatment 2 (MEP)--0.6 mg/kg of body weight of 5% meperidine; treatment 3 (SS)--0.9% saline solution (control group). Heart rate, arterial pressure, respiratory rate, rectal temperature, analgesia, sedation, and motor-blocking were determined before drug administration (baseline values); at 5, 10, 15, and 30 minutes after drug administration, and then at 30-minute intervals thereafter. Both hyperbaric bupivacaine and meperidine administered epidurally produced complete bilateral perineal analgesia in all horses. The onset of analgesia was 6, s = 2.6 minutes after injection of bupivacaine, as opposed to 9, s = 2 minutes after meperidine. The duration of analgesia was 240, s = 57 minutes for meperidine and 320, s = 30 minutes for bupivacaine. Heart and respiratory rates, arterial pressure, and rectal temperature did not change (P < 0.05) significantly from basal values after the epidural administration of bupivacaine, meperidine, or saline solution. To conclude, both bupivacaine and meperidine induced long-lasting perineal analgesia, with minimal cardiovascular effects. Analgesia was induced faster and lasted longer with bupivacaine.
Assuntos
Analgesia Epidural/veterinária , Analgésicos Opioides/farmacologia , Anestésicos Locais/farmacologia , Bupivacaína/farmacologia , Cavalos/fisiologia , Meperidina/farmacologia , Analgesia Epidural/métodos , Analgésicos Opioides/administração & dosagem , Anestésicos Locais/administração & dosagem , Animais , Pressão Sanguínea/efeitos dos fármacos , Bupivacaína/administração & dosagem , Relação Dose-Resposta a Droga , Frequência Cardíaca/efeitos dos fármacos , Injeções Epidurais/veterinária , Cinética , Meperidina/administração & dosagem , Medição da Dor/veterinária , Distribuição Aleatória , Respiração/efeitos dos fármacosRESUMO
OBJECTIVE: To determine the analgesic, sedative, motor, cardiac and respiratory effects of epidural clonidine in cattle. STUDY DESIGN: Prospective randomized study. ANIMAL POPULATION: Six healthy male cattle weighing between 236 and 365 kg. METHODS: To investigate the effect of epidural clonidine, the animals received 2 and 3 micro g kg(-1) of clonidine diluted to 8 mL with 0.9% saline. Two treatments were utilized as controls. The animals from the first control treatment received 2% lidocaine (0.4 mg kg(-1)) and those from the second received an equal volume of 0.9% saline. Each animal received each treatment in random order. Evaluations of analgesia, sedation, muscle relaxation, heart rate, respiratory rate and rectal temperature were obtained at 0 (basal), 2, 5, 10, 15 and 30 minutes after epidural injection, and then at 30-minute intervals until loss of analgesia occurred. All the animals received a standard noxious stimulus consisting of needle insertion into the skin and deep muscle; a 4-point scale was used to score the response. A second scale was used to score sedation and a third for muscle relaxation. RESULTS: Both doses of clonidine were effective in producing analgesia of the tail, perineum, and upper hindlimb. Complete analgesia was present before (mean +/- SE = 9 +/- 4 vs. 19 +/- 9 minutes) and lasted longer (311 +/- 33 vs. 192 +/- 27 minutes) for the 3 microg kg(-1) versus the 2 microg kg(-1) dose, respectively. A dose-dependent sedative effect of clonidine was also observed, with a peak effect between 60 and 180 minutes. No effects on heart or respiratory rates were observed with either dose of clonidine. CONCLUSIONS: Epidural administration of 2 and 3 micro g kg(-1) of clonidine in cattle in this study provided bilateral perineal analgesia/anesthesia with a dose-dependent onset and duration of action. CLINICAL RELEVANCE: Further studies are required to determine whether the analgesia is sufficient for surgery.