Cardiovascular assessment in horses sedated with xylazine or amitraz / Avaliação cardiovascular em eqüinos sedados com xilazina ou amitraz

Cardiovascular effects due to intravenous (IV) xylazine (1.0mg/kg) or amitraz (0.1 or 0.4mg/kg) were evaluated in horses. Left ventricular function indexes, heart rate (HR), and cardiac output (CO) were measured by echocardiography. Second degree atrioventricular (AV) block was detected by electrocardiography. Invasive arterial blood pressure (AP) was also evaluated. All parameters were measured immediately before and during 60 minutes after drug injection. HR, CO, and second degree AV block were different between xylazine and amitraz-0.4mg/kg groups. Xylazine induced initial hypertension 10 minutes after injection, and hypotension was observed 30 minutes after amitraz-0.4mg/kg administration. Except for the second degree AV block which occurred only at five minutes, there was no change in the echocardiographic measurements after administration of amitraz-0.1mg/kg. Thus, amitraz-0.4mg/kg and xylazine (1.0mg/kg) induced similar cardiovascular side effects, but long-lasting action of amitraz-0.4mg/kg in the cardiovascular system was observed.

Avaliaram-se efeitos cardiovasculares decorrentes da administração intravenosa (IV) de xilazina (1,0mg/kg) ou amitraz (0,1 ou 0,4mg/kg) em cavalos. Os índices ventriculares, a freqüência cardíaca (FC) e o débito cardíaco (DC) foram mensurados por ecocardiografia, e o bloqueio atrioventricular de segundo grau (BAV2), detectado por eletrocardiografia. A pressão arterial invasiva foi também avaliada. Todos os parâmetros foram mensurados imediatamente antes e durante 60 minutos após a administração dos fármacos. Os valores da FC, do DC e do BAV2 apresentaram alterações significativas nos grupos da xilazina e do amitraz na dose de 0,4mg/kg. A xilazina induziu hipertensão inicial 10 minutos após sua administração e a dose de 0,4mg/kg amitraz induziu hipotensão após 30 minutos. Exceto pela ocorrência de BAV2 aos cinco minutos, não houve alteração nas mensurações ecocardiográficas após a administração de amitraz-0.1mg/kg. Nas doses utilizadas, a xilazina (1,0mg/kg) e o amitraz-0,4mg/kg promoveram alterações semelhantes no sistema cardiovascular, porém os efeitos cardiovasculares provocados pelo amitraz foram mais prolongados.

Relative efficiency of succinylcholine, xylazine, and carfentanil/xylazine mixtures to immobilize free-ranging moose.

We compared the efficiency of succinylcholine chloride, xylazine hydrochloride and carfentanil/xylazine mixtures in immobilizing 364 free-ranging moose (Alces alces) between 1987 and 1997 in Québec (Canada). With succinylcholine chloride (0.070, 0.062, 0.051 mg/kg of estimated body weight for calves, juveniles and adults), 63% of the 252 immobilization attempts led to complete immobilization and marking, whereas 7% of the darted animals died of respiratory paralysis during handling. The moose took an average of 13 min to lay down after darting (down time). Injection of xylazine (3.67-4.22 mg/kg) permitted sedation (the animal laid down but got up again when approached) or complete immobilization in 78% of the 40 darted adult moose, the mean down time being 8.7 min. No mortality was noted with this drug but 58% of the marked animals were only sedated. The use of RX821002A (0.058 mg/kg) as an antagonist, permitted a mean recovery time of 2.8 min after intravenous injection. With the carfentanil/xylazine mixtures (0.0071 and 0.181 mg/kg), 96% of the immobilization trials (n = 72) led to complete (88%) or partial (8%) immobilization, but 6% of the moose died several days after capture. The mean down time was 6.6 min, and injection of naltrexone (0.709 mg/kg) antagonized the effect of the immobilizing agent within 3.7 min. The respiratory rate was higher (P < 0.05) among moose immobilized with xylazine (35/min) than among those immobilized with carfentanil/xylazine mixtures (19/min) but this variation could be related to a longer pursuit time (z = 3.60; P < 0.01) and higher stress levels during handling. Rectal temperature also was higher with xylazine but the difference was small (39.7 vs. 39.3, P = 0.03) and did not differ significantly between the sexes (P > 0.05). Considering loss of materials and helicopter flight time due to non-successful marking trials, carfentanil/xylazine mixtures were the least expensive ($333 Cdn/animal).