Abstract:
A suitable long-term anaesthetic technique was required for implantation of physiological
sensors and telemetric devices in sub-adult Nile crocodiles (Crocodylus niloticus) to allow the
collection of physiological data. Five Nile crocodiles with a median body mass of 24 kg were
used. After manual capture, they were blindfolded and 0.2 mL (1 mg/mL) medetomidine was
administered intramuscularly in four of the animals which had an estimated body mass
between 20 kg and 30 kg. One crocodile with an estimated body mass of 50 kg received 0.5 mL.
For induction, 5 mL propofol (10 mg/mL) was injected intravenously into the occipital sinus.
Additional doses were given when required to ensure adequate anaesthesia. Anaesthesia
was maintained with 1.5% isoflurane. Ventilation was controlled. Local anaesthesia was
administered for surgical incision and external placement of the radio transmitter. Medetomidine
was antagonised with atipamezole at the end of surgery. Median heart rate during surgery
was 22 beats/min, at extubation 32 beats per min and 30 beats per min the following day at
the same body temperature as under anaesthesia. Median body temperature of the animals
increased from 27.3 °C to 27.9 °C during anaesthesia, as room temperature increased from
24.5 °C to 29.0 °C during surgery. Anaesthesia was successfully induced with intramuscular
medetomidine and intravenous propofol and was maintained with isoflurane for the placement
of telemetric implants. Intraoperative analgesia was supplemented with lidocaine infiltration.
Perioperative physiological parameters remained stable and within acceptable clinical limits.
Multiple factors appear to influence these variables during the recovery period, including
residual anaesthetic effects, environmental temperature and physical activity.
