Читать книгу Farm Animal Anesthesia - Группа авторов - Страница 33

At 0.02 mg/kg IV, detomidine produced sedation which is comparable to that of 0.04 mg/kg of xylazine [88]. Increasing the dose to 0.03 mg/kg, detomidine induced recumbency in sheep with sedation that was equivalent to 0.15 mg/kg of xylazine and 0.01 mg/kg of medetomidine [89]. Effective sedation and significant but transient hypotension and bradycardia followed by tachycardia and hypoxemia were reported during sedation with 0.091 ± 0.004 mg/kg of IV detomidine. Cardiac arrhythmias (e.g. atrioventricular block, ST elevation, and premature ventricular contraction) were also observed in this study [90]. Deep sedation with hypotension of 108 ± 9.1 minutes occurred when detomidine (0.092 ± 0.006 mg/kg IV) was combined with diazepam (0.7 ± 0.2 mg/kg IV). Cardiac arrhythmias, but not hypoxemia or hypercapnia, were observed when diazepam was administered with detomidine [91]. Obviously, hypoxemia and pulmonary edema can occur with any of the α₂ agonists, but the severity of hypoxemia was reported to be less with detomidine [85]. IV administration of α₂ agonists normally induces a characteristic biphasic blood pressure response characterized by transient hypertension followed by longer‐lasting hypotension. The initial hypertension is the result of vasoconstriction from stimulation of peripheral (postsynaptic) α₂ adrenoceptors, and the subsequent hypotension is due to activation of central (presynaptic) α₂ adrenoceptors resulting in decreased sympathetic outflow and catecholamine release [33]. Celly et al. [82] reported a longer‐lasting hypertension was observed following IV administration of detomidine (0.03 mg/kg). Interestingly, in that study, mean arterial blood pressure showed the characteristic biphasic patterns for all four α₂ agonists (xylazine, detomidine, medetomidine, and romifidine), but all the values were within or above normal values. In other words, hypotension, defined as below‐normal arterial blood pressure values, was not observed with any of the α₂ agonists in this study [82]. Unlike xylazine, detomidine at IV doses less than 0.04 mg/kg did not produce an oxytocin‐like effect on the uterus in gravid cattle. Doses higher than 0.04 mg/kg may increase the electrical activity of the uterine muscles, but it did not induce the synchronization of the bursts of potentials that is characteristic of parturition. Therefore, detomidine at the therapeutic dose is unlikely to induce premature parturition in pregnant ruminants [56, 57].

The sedative effects of detomidine gel applied intravaginally (0.2 mg/kg) has been studied in alpacas. The onset, the time to maximal sedation, and the duration of sedation were 13.0 ± 2.5, 25 ± 4, and 65 ± 12 minutes, respectively. Four of six alpacas assumed sternal recumbency position during sedation. The result of this study showed that intravaginal detomidine produced moderate sedation which was not as profound as that of IV detomidine [92].