[Influence of atracurium on cardiovascular parameters in horses undergoing vitrectomy during general anaesthesia, and on recovery duration and quality].

Objective: In most ocular procedures, a central position of the eye is necessary. This can be achieved using a deep plane of anaesthesia, locoregional blocks or with neuromuscular blocking agents. The aim of this study was to evaluate the influence of atracurium on cardiovascular parameters, and on recovery quality and duration in horses.
Material and Methods: Thirty-four warmblood horses undergoing in total 50 vitrectomies were divided into two groups. Premedication, induction and maintenance were identical in all patients. After 20 minutes, horses of group A received atracurium (0.1 mg/kg) while in the control group (group K) the depth of anaesthesia was adapted to keep the bulbus in a central position. Dobutamine and fluids were administered to maintain the mean arterial blood pressure (MAP) above 70 mmHg. Cardiac output (CO), heart rate (HR), MAP, respiratory rate, end-expiratory isoflurane concentration (ETIso) and dobutamine requirements were determined. Position and movement of the globe during the surgical procedure were scored. Time and quality of the recovery period was scored.
Results: Horses of group K required significantly higher concentrations of isoflurane (group A: 1.08 ± 0.1%; group K: 1.34 ± 0.2%) and had an overall lower MAP (group A: 88.4 ± 10.3 mmHg; group K: 76.6 ± 11.6 mmHg) and CO (group A: 36.9 ± 11.7 l/min; group K: 28.5 ± 7.2 l/min) but needed significantly more dobutamine (group A: 0.37 ± 0.17 μg/kg/min; group K: 0.99 ± 0.46 μg/kg/min) compared to group A. Complete relaxation occurred 9.5 ± 2.5 minutes after atracurium bolus and lasted for 25 ± 7.1 minutes. The score of the bulbus position and movement was significantly lower in group A, resulting in a better quality for the surgical procedure. In group A, the recovery time to standing was significantly shorter (group A: 18.1 ± 5.4 min; group K: 31.5 ± 7.1 min), with no difference in quality.
Conclusion and Clinical Relevance: The use of atracurium resulted in a better cardiovascular condition, probably because of the isoflurane-sparing effect. The recovery time was shorter in these horses without negative effects on recovery quality. No signs of residual atracurium effects were detected.