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Plasma catecholamine concentrations in response to onychectomy were examined in 27 cats receiving different anesthetic regimens. Each cat was anesthetized with a dissociative-tranquilizer combination, and onychectomy was performed on 1 forefoot. One week later, each cat was anesthetized with the same dissociative-tranquilizer combination plus either butorphanol or oxymorphone, and onychectomy was performed on the other forefoot. Four treatment groups were studied: tiletamine-zolazepam and tiletamine-zolazepam-butorphanol combinations were administered to group-1 cats, ketamine-acepromazine and ketamine-acepromazine-butorphanol combinations were administered to group-2 cats, tiletamine-zolazepam and tiletamine-zolazepam-oxymorphone combinations were administered to group-3 cats, and ketamine-acepromazine and ketamine-acepromazine-oxymorphone combinations were administered to group-4 cats. All drug combinations were administered im. Central venous blood samples were drawn for catecholamine analysis after injection of drug(s), after onychectomy, and 1, 2, and 4 hours after injection. Tiletamine-zolazepam alone or tiletamine-zolazepam-butorphanol prevented epinephrine release for 2 hours after injection of drug(s). Norepinephrine concentration increased significantly (P < 0.05) from baseline after onychectomy for tiletamine-zolazepam-butorphanol and at 4 hours for tiletamine-zolazepam and tiletamine-zolazepam-butorphanol. After onychectomy, there was no difference in epinephrine values between tiletamine-zolazepam and tiletamine-zolazepam-oxymorphone. Ketamine-acepromazine prevented increases in norepinephrine and epinephrine concentrations for up to 2 hours after surgery. Addition of butorphanol to ketamine-acepromazine decreased norepinephrine values immediately after onychectomy. Addition of oxymorphone to ketamine-acepromazine resulted in lower epinephrine values 4 hours after surgery.

Free access
in American Journal of Veterinary Research


Six healthy Holstein calves were anesthetized with isoflurane in O2 and instrumented for hemodynamic studies. A saphenous artery was catheterized for measurement of blood pressure and withdrawal of blood for determination of the partial pressure of carbon dioxide (PaCO2 ), oxygen (PaO2 ), and arterial pH (pHa). Respiration was controlled throughout the study. The ecg and eeg were monitored continuously. A thermodilution catheter was passed via the right jugular vein into the pulmonary artery for determination of cardiac output and measurement of central venous pressure, pulmonary arterial pressure, and pulmonary capillary wedge pressure. Baseline values (time 0) were recorded following recovery from isoflurane. Tiletamine-zolazepam (4 mg/kg)-xylazine (0.1 mg/kg) were administered iv immediately after recording baseline values. Values were again recorded at 5, 10, 20, 30, 40, 50, and 60 minutes after injection. Changes in left ventricular stroke work index, Paco2 , and pHa were insignificant. Arterial blood pressure and systemic vascular resistance increased above baseline at 5 minutes and then gradually decreased below baseline at 40 minutes, demonstrating a biphasic response. Values for pulmonary capillary wedge pressure, pulmonary arterial pressure, central venous pressure, and Pao2 were increased above baseline from 5 to 60 minutes. Stroke volume, stroke index, and right ventricular stroke work index were increased from 20 or 30 minutes to 60 minutes. Pulmonary vascular resistance increased at 10 minutes, returned to baseline at 20 minutes, and was increased again at 60 minutes. Heart rate, cardiac output, cardiac index, and rate pressure product were decreased at 5 minutes, and with the exception of cardiac output, remained so for 60 minutes. Cardiac output returned to the baseline value at 30 minutes. All calves recovered without complications. We concluded that tiletamine-zolazepam (4 mg/kg iv)-xylazine (0.1 mg/kg iv) is a safe and useful anesthetic regimen for use in calves.

Free access
in American Journal of Veterinary Research



To evaluate analgesic effects after epidural administration of medetomidine to cows, compared with effects of lidocaine hydrochloride and 0.9% NaCI solution.


6 adult beef cows.


3 treatments were administered to each cow, with a 1-week interval between subsequent treatments. Treatments consisted of 5 ml of physiologic saline (0.9% NaCI) solution; 0.2 mg of lidocaine/kg of body weight, not to exceed 100 mg (5 ml); and 15 μg of medetomidine/kg, diluted with 0.9% NaCI solution to provide a volume of 5 ml. Epidural injections were given in the first or second coccygeal space. Heart rate, respiratory rate, and arterial blood pressure values were recorded before injection, 5 and 10 minutes after injection, and at 10-minute intervals thereafter. Onset and duration of analgesia, sedation, and ataxia were recorded. A repeated-measures ANOVA was used to detect differences between treatments.


Epidural administration of 0.9% NaCI solution did not induce analgesia. Lidocaine induced analgesia within 5 to 20 minutes, which lasted 10 to 115 minutes (mean ± SD, 43.3 ± 37.2 minutes). Heart rate decreased during lidocaine-induced analgesia. Heart and respiratory rates decreased, but blood pressure remained unchanged, after medetomidine administration. Medetomidine induced analgesia within 5 to 10 minutes, which lasted 412 ± 156 minutes. Mild to moderate sedation and moderate ataxia were observed. Two cows became recumbent, but were easily coaxed to stand. Medetomidine-induced salivation and increased frequency of urination were observed in all cows.

Conclusions and Clinical Relevance

Epidural administration of medetomidine induced prolonged analgesia that was suitable for perineal surgery, post-operative analgesia, and relief of continuous straining. (Am J Vet Res 1998;59:162–167)

Free access
in American Journal of Veterinary Research