Mira Ziolo (OVC, Canada), Mads Bertelsen.

Objective
To characterise the effects of propofol administered at 10 and 20 mg/kg via the supravertebral venous sinus.

Design
Prospective, blinded randomized cross-over study.

Sample Population
10 red-eared sliders (Trachemys scripta spp.).

Procedures
Propofol was administered at 10 and 20 mg/kg via the supravertebral sinus.  Physiological parameters measured were the skeletal muscle tone of neck, forelimbs, hindlimbs, and tail, the palpebral, corneal, and ‘tap’ reflexes, the response to deep pain, and spontaneous movement. Time measurements were total anaesthetic duration, induction time, duration of the nplateau phase, time to recovery and time to loss and recovery of each physiological parameter.  Heart rate was measured regularly throughout each trial.  A minimum period of 7 days washout was allowed between each trial.  Data was analyzed to determine statistical significance using Wilcoxson-Rank Sum tests for scored data, paired t-tests for time measurements, and Signed Rank 2-tail tests for comparing population proportions.

Results
Mean induction times were 1.7 minutes with 10 mg/kg doses and 0.9 minutes with 20 mg/kg doses. Significant differences between the two doses were found in anaesthetic duration, in duration of the plateau phase, in times to recovery from anaesthesia and of skeletal muscle tone. Additionally, a greater proportion of subjects in 20 mg/kg trials experienced loss of palpebral reflexes and sensation of deep pain, while corneal and spinal reflexes remained highly conserved at both doses. No significant differences were seen in the time to maximal loss of skeletal muscle tone nor in the loss or recovery of reflexes. Total anaesthetic time was 63 and 91 min, for 10 and 20 mg/kg trials respectively.

Conclusion and Clinical Relevance
Propofol administration via the supravertebral sinus is a rapid and reliable means of achieving anaesthesia in healthy red-eared sliders. Dosages of 10-20mg/kg should be adequate for procedures of shorter and longer duration or for induction and transfer to inhalation anaesthesia, depending on the requirements of the clinician.