A 9-year-old spayed female domestic shorthair cat was evaluated at a veterinary teaching hospital for right carpal arthrodesis following a traumatic hyperextension injury. At the time of the evaluation, the cat was receiving buprenorphine hydrochloride (0.06 mg) transmucosally twice daily and robenacoxib (6.0 mg) orally once daily for pain associated with the injury as prescribed by the referring veterinarian. The cat had idiopathic epilepsy, which had been diagnosed 3 years prior and controlled with twice-daily oral administration of levetiracetam (62.5 mg). A diagnosis of mild hypertrophic cardiomyopathy had also been made 5 years prior, but the cat was not receiving any cardiac medications. Findings of the pre-anesthesia physical examination were unremarkable aside from right carpal swelling and intercarpal joint instability (rectal temperature, 37.8°C [100.1°F]; pulse rate, 168 beats/min; and respiratory rate, 32 breaths/min). The cat weighed 7.1 kg (15.6 lb) but was markedly overconditioned, and medication doses were calculated on the basis of an approximate lean body weight of 5.5 kg (12.1 lb).
Prior to anesthesia, cardiology consultation was undertaken. Echocardiography revealed a moderate increase in left ventricular free wall thickness and normal chamber sizes consistent with the previous diagnosis of mild hypertrophic cardiomyopathy. The timing lead ECG during echocardiography revealed sinus rhythm with a heart rate of 180 beats/min and low-voltage R waves, which were considered to be a result of either the patient's obesity or an axis deviation; however, a 6-lead ECG examination was not performed because of the cat's fractious nature. The cat was deemed a suitable candidate for general anesthesia.
The cat was premedicated with midazolam hydrochloride (0.18 mg/kg [0.08 mg/lb]), methadone hydrochloride (0.27 mg/kg [0.12 mg/lb]), and alfaxalone (0.47 mg/kg [0.21 mg/lb]) IM, followed by additional doses of alfaxalone (0.5 mg/kg [0.23 mg/lb]) and methadone (0.2 mg/kg [0.09 mg/lb]) 20 minutes later, which resulted in adequate sedation. A 22-gauge IV cephalic catheter was placed, and an infusion of lactated Ringer solution (2 mL/kg/h [0.9 mL/lb/h]) was started and maintained throughout anesthesia. Anesthesia was induced with alfaxalone (1 mg/kg [0.45 mg/lb]) administered IV. The cat was intubated, and anesthesia was maintained via inhalation of isoflurane and oxygen. Preoperative radiography was performed. During this procedure, the cat was stable except for hypothermia (35° to 35.8°C [95° to 96.4°F]). A baseline rhythm strip was printed (Figure 1).
The authors declare that there were no conflicts of interest.
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