Detomidine-propofol anesthesia for abdominal surgery in horses

Objective-To evaluate propofol for induction and maintenance of anesthesia, after detomidine premedication, in horses undergoing abdominal surgery for creation of an experimental intestinal adhesion model. Study Design-Prospective study. Animals-Twelve horses (424 +/- 81 kg) from 1 to 20 years of age (5 females, 7 males). Methods-Horses were premedicated with detomidine (0.015 mg/kg IV) 20 to 25 minutes before induction and a propofol bolus (2 mg/kg IV) was administered for induction. Propofol infusion (0.2 mg/kg/min IV) was used to maintain a nesthesia. The infusion rate was adjusted to maintain an acceptable anesthe tic plane as determined by muscle relaxation, occular signs, response to su rgery, and cardiopulmonary responses. Oxygen (15 L/min) was insufflated thr ough an endotracheal tube as necessary to maintain the SpO(2) greater than 90%. Systolic (SAP), mean (MAP), and diastolic (DAP) arterial pressures, he art rate (HR), electrocardiogram (ECG), respiratory rate (RR), SpO(2) (via pulse oximetry), and nasal temperature were recorded at 15 minute intervals , before premedication and after induction of anesthesia. Arterial blood ga s samples were collected at the same times. Objective data are reported as mean (+/-SD); subjective data are reported as medians (range). Results-Propofol (2.0 mg/kg IV) induced anesthesia (mean bolus time, 85 sec ) within 24 sec (+/-22 sec) after the bolus was completed. Induction was go od in 10 horses; 2 horses showed signs of excitement and these two inductio ns were not smooth. Propofol infusion (0.18 mg/kg/min +/- 0.04) was used to maintain anesthesia for 61 +/- 19 minutes with the horses in dorsal recumb ency. Mean SAP, DAP, and MAP increased significantly over time from 131 to 148, 89 to 101, and 105 to 121 mm Hg, respectively. Mean HR varied over tim e from 43 to 45 beats/lnin, whereas mean RR increased significantly over an esthesia time from 4 to 6 breaths/min. Mean arterial pH decreased from a ba seline of 7.41 +/- 0.07 to 7.30 +/- 0.05 at 15 minutes of anesthesia, then increased towards baseline values. Mean Pace, values increased during anest hesia, ranging from 47 to 61 min Hg whereas PaO2 values decreased from base line (97 +/- 20 mm Hg), ranging from 42 to 57 mm Hg. Muscle relaxation was good and no horses moved during surgery: Recovery was good in 9 horses and acceptable in 3; mean recovery time was 67 +/- 39 minutes with 2.3 +/- 2.3 attempts necessary for the horses to stand. Conclusions-Detomidine-propofol anesthesia in horses in dorsal recumbency w as associated with little cardiovascular depression, but hypoxemia and resp iratory depression occurred and some excitement was seen on induction. Clinical Relevance-Detomidine-propofol anesthesia is not recommended for su rgical procedures in horses if dorsal recumbency is necessary and supplemen tal oxygen is not available (eg, field anesthesia). (C) Copyright 1999 by T he American College of Veterinary Surgeons.