Objective To report the cardiovascular variables, anaesthetic effects and recovery quality of an anaesthesia technique using variable rate infusion propofol combined with constant rate infusion fentanyl in dogs undergoing elective surgery.
Study design Prospective clinical trial.
Animals A total of 27 dogs, aged 2.7 ± 2.65 years and weighing 24 ± 11 kg.
Methods Following intramuscular acepromazine (0.03 or 0.05 mg kg−1) and subcutaneous carprofen (4 mg kg−1) pre-medication, anaesthesia was induced with propofol (4.0 ± 0.5 mg kg−1) intravenously (IV). All dogs were ventilated with 100% oxygen to maintain normocapnia. Propofol was infused at 0.4 mg kg−1 minute−1 for 20 minutes and then at 0.3 mg kg−1 minute−1. If mean arterial blood pressure (MAP) decreased below 70 mmHg, propofol infusion was reduced by 0.1 mg kg−1 minute−1. Five minutes after induction of anaesthesia, fentanyl was administered (2 μg kg−1) IV followed by the infusion at 0.5 μg kg−1 minute−1 and atropine (40 μg kg−1) IV. Heart rate, MAP, respiratory rate, tidal volume, end-tidal carbon dioxide, presence of reflexes, movements and recovery times and quality were recorded.
Results Mean anaesthetic duration was 131 ± 38.5 minutes. Mean heart rate peaked 10 minutes after atropine injection and gradually declined, reaching pre-anaesthetic values at 55 minutes. MAP easily was maintained above 70 mmHg. Mean times to return of spontaneous ventilation, extubation, head lift and sternal recumbency were 21 ± 10.1, 33 ± 14.6, 43 ± 19.7 and 65 ± 23.4 minutes, respectively. Recovery was smooth and quiet. The time to sternal recumbency was significantly correlated with the duration of anaesthesia and total dose of propofol; time to extubation was correlated to total dose of propofol.
Conclusion and clinical relevance Propofol and fentanyl infusions provided stable cardiovascular function and satisfactory conditions for surgery. Some modifications of infusion rates are required to improve the long-recovery times.