Total intravenous anaesthesia by boluses or by continuous rate infusion of propofol in mute swans (Cygnus olor)

Objective To investigate intravenous (IV) propofol given by intermittent boluses or by continuous rate infusion (CRI) for anaesthesia in swans. Study design Prospective randomized clinical study. Animals Twenty mute swans (Cygnus olor) (eight immature and 12 adults) of unknown sex undergoing painless diagnostic or therapeutic procedures. Methods Induction of anaesthesia was with 8 mg kg⁻¹ propofol IV. To maintain anaesthesia, ten birds (group BOLI) received propofol as boluses, whilst 10 (group CRI) received propofol as a CRI. Some physiological parameters were measured. Anaesthetic duration was 35 minutes. Groups were compared using Mann-Whitney U-test. Results are median (range). Results Anaesthetic induction was smooth and tracheal intubation was achieved easily in all birds. Bolus dose in group BOLI was 2.9 (1.3-4.3) mg kg⁻¹; interval between and number of boluses required were 4 (1-8) minutes and 6 (4-11) boluses respectively. Total dose of propofol was 19 (12.3-37.1) mg kg⁻¹. Awakening between boluses was very abrupt. In group CRI, propofol infusion rate was 0.85 (0.8-0.9) mg kg⁻¹ minute⁻¹, and anaesthesia was stable. Body temperature, heart and respiratory rates, oxygen saturation (by pulse oximeter) and reflexes did not differ between groups. Oxygen saturations (from pulse oximeter readings) were low in some birds. Following anaesthesia, all birds recovered within 40 minutes. In 55 % of all, transient signs of central nervous system excitement occurred during recovery. Conclusions and clinical relevance 8 mg kg⁻¹ propofol appears an adequate induction dose for mute swans. For maintenance, a CRI of 0.85 mg kg⁻¹ minute⁻¹ produced stable anaesthesia suitable for painless clinical procedures. In contrast bolus administration, was unsatisfactory as birds awoke very suddenly, and the short intervals between bolus requirements hampered clinical procedures. Administration of additional oxygen throughout anaesthesia might reduce the incidence of low arterial haemoglobin saturation.