An 8-year-old 527-kg (1,159-lb) castrated male Appaloosa was evaluated by a referring veterinarian because of colic, of which the horse had a history of repeat episodes. During an episode of colic 6 months previously, the horse responded to treatment with flunixin meglumine. The referring veterinarian evaluated the horse at the farm; because the horse did not respond to treatment with flunixin at this time, it was transported to the veterinarian's clinic for further examination. During transrectal palpation, the referring veterinarian palpated a taut ventral cecal band. A sample of peritoneal fluid was collected via abdominal paracentesis; the protein content (0.4 g/dL; reference range, < 2.5 g/dL) of the fluid sample was considered normal. The results of the abdominal ultrasonography by the referring veterinarian were suggestive of a mass lesion adjacent to the spleen (at the level of the seventh intercostal space). The horse was referred to the Cornell University Hospital for Animals for further evaluation.
On initial evaluation, the horse assumed an abnormal stance with a pronounced forward extension of the forelimbs and rearward extension of the hind limbs with respect to the body. Auscultation revealed tachycardia (heart rate, 60 beats/min) with a normal cardiac rhythm; borborygmi were diminished in all 4 abdominal quadrants. The horse was administered a dose each of xylazine hydrochloride (0.3 mg/kg [0.14 mg/lb], IV) and butorphanol tartrate (0.01 mg/kg [0.005 mg/lb], IV). Transrectal palpation revealed mild gas distention of the large intestine and a taut large colon tenia that was oriented transversely in the abdomen. Abdominal ultrasonography revealed that the small intestine was hypomotile and nondistended. In the area of the left seventh intercostal space, an accumulation of peritoneal fluid surrounded a portion of omentum or small intestine, but the overall amount of peritoneal fluid was not considered abnormal, and no mass lesion was detected. The horse received a bolus of isotonic crystalloid fluids (5 L) IV and then was administered isotonic crystalloid fluids with potassium chloride (20 mEq/L) IV at a rate approximately 1.5 times maintenance requirements. Approximately 1 hour after administration of xylazine and butorphanol, lidocaine hydrochloride (1.3 mg/kg [0.59 mg/lb]) was administered IV over a period of 10 minutes, which was followed by commencement of a constant rate infusion (CRI) of lidocaine (0.05 mg/kg/min [0.023 mg/lb/min], IV) to promote intestinal motility.
Approximately 1.5 hours after the CRI of lidocaine was started, the horse developed generalized skeletal muscle fasciculations and an arrhythmia was detected via cardiac auscultation. An ECG rhythm strip was recorded (Figure 1), and the lidocaine administration was then discontinued.
Cook VL, Jones Shults J, McDowell M, et al.Attenuation of ischaemic injury in the equine jejunum by administration of systemic lidocaine. Equine Vet J 2008;40:353–357.
Malone E, Ensink J, Turner T, et al.Intravenous continuous infusion of lidocaine for treatment of equine ileus. Vet Surg 2006;35:60–66.
Meyer GA, Lin HC, Hanson RR, et al.Effects of intravenous lidocaine overdose on cardiac electrical activity and blood pressure in the horse. Equine Vet J 2001;33:434–437.
Lieberman NA, Harris RS, Katz RI, et al.The effects of lidocaine on the electrical and mechanical activity of the heart. Am J Cardiol 1968;22:375–380.
Abutarbush SM. Use of ultrasonography to diagnose large colon volvulus in horses. J Am Vet Med Assoc 2006;228:409–413.
Pariaut R, Moïse NS, Koetje BD, et al.Evaluation of atrial fibrillation induced during anesthesia with fentanyl and pentobarbital in German Shepherd Dogs with inherited arrhythmias. Am J Vet Res 2008;69:1434–1445.
Sellon DC, Monroe VL, Roberts MC, et al.Pharmacokinetics and adverse effects of butorphanol administered by single intravenous injection or continuous intravenous infusion in horses. Am J Vet Res 2001;62:183–189.
Garcia-Villar R, Toutain PL, Alvinerie M, et al.The pharmacokinetics of xylazine hydrochloride: an interspecific study. J Vet Pharmacol Ther 1981;4:87–92.