Influence of acepromazine on the cardiovascular effects of dobutamine in isoflurane-anaesthetised horses premedicated with romifidine.

OBJECTIVE

To explore the influence of acepromazine on the cardiovascular effects of dobutamine in isoflurane-anaesthetised horses premedicated with romifidine.

STUDY

DESIGN

Prospective randomised clinical trial.

ANIMALS: A total of 18 horses undergoing elective arthroscopy were enrolled, of which 12 horses requiring dobutamine were included.

METHODS

Horses were randomised to receive acepromazine 0.02 mg kg-1 (Group A+) intravenously (IV) or none (Group A-), 35 minutes before anaesthesia. Horses received xylazine 0.2 mg kg-1 concurrently to facilitate IV access. Horses were premedicated with romifidine 0.08 mg kg-1, induced with ketamine 2.2 mg kg-1 and diazepam 0.08 mg kg-1 IV, and maintained with isoflurane in oxygen. Dobutamine infusion was commenced when mean arterial pressure (MAP) was < 60 mmHg. Cardiovascular data were collected prior to dobutamine, and at a target MAP of ≥ 70 mmHg. Dobutamine start time from induction, duration and dose to reach target MAP were compared using Mann-Whitney U test. Cardiovascular variables were compared using repeated measures ANOVA and post-hoc Fisher's least significant difference test.

RESULTS

Cardiac index (CI) and its percentage change from baseline were significantly higher at target MAP in group A+ [62.0 (49.9-74.2) mL minute-1 kg-1; 42.8 (17.0-68.7) %] than in A- [49.5 (39.6-59.5) mL minute-1 kg-1; -4.05 (-21.2-13.0) %] (p = 0.049; p = 0.003). Group A+ required significantly earlier dobutamine [20 (18-25) minutes] than group A- [36 (27-60) minutes] (p = 0.02). Group A+ required significantly higher dobutamine dose [1.5 (1-2.5) μg kg-1 minute-1] to reach target MAP than group A- [0.5 (0.5-1) μg kg-1 minute-1] (p = 0.009).

CONCLUSION AND CLINICAL RELEVANCE: Dobutamine significantly increased MAP and CI following pre-anaesthetic acepromazine sedation, in isoflurane-anaesthetised horses premedicated with romifidine. Without acepromazine, dobutamine increased MAP but not CI. Interactions between acepromazine, romifidine and dobutamine on the cardiovascular system should be considered.