Prospective study of intravenous lidocaine in Trachemys scripta

Abstract

Introduction, The intravenous administration of a 2 mg/kg bolus of lidocaine has been shown to have analgesic effects without adverse effects in humans and mammals. In reptiles, there are no  published studies on Trachemys scripta, which is one of the most common reptile species in exotic  veterinary clinics. Thus, this study proposes to investigate lidocaine’s analgesic effect, which could be  beneficial for good analgesia, decreasing the use of doses of opioids such as morphine.

Objective. To study the analgesic effect of a 2 mg/kg intravenous bolus of lidocaine in Trachemys  scripta.

Settings and Design. This is a prospective double-blind study with a sample of seven turtles (n=7)  divided in two groups: one group with three males and one female (n=4) and another group with three  females (n=3). This is a crossover 2x2 design with a wash-out period of 14 days between  lidocaine and normal  saline NaCl 0.9% administration, where the turtles that received normal saline  were the Control Group and the turtles that received the drug were the Lidocaine Group.

Methods and Material. In order to test the analgesic effects, the pain response in buttocks and limbs  was measured after causing pain with an automatic puncturing device. Furthermore, blood samples  were taken to study possible side effects in blood parameters. Consciousness level was graded by  monitoring the palpebral reflex and neck and limb retraction. Finally, the heart rate was measured  using a doppler device and the respiratory rate by counting the number of serrato muscle contractions  in the cervical pit, considering apneas and/or possible arrhythmias.

Statistical Analysis Used. Since heart rate, respiratory rate, body temperature at the inguinal and cervical pit, average temperature and blood parameters do not follow a normal distribution, the  Wilcoxon test was used. A Chi-square test was used for apnea and arrhythmia incidence, consciousness  level and pain response in buttocks and limbs. The McNemar test was also used for  apnea and arrhythmia incidence and the Cochran-Arritage test was also used for pain response in limbs  and buttocks. In all cases, the confidence interval was 95%, with values being considered  statically significant when p<0.05.

Results. Both pain response in limbs and consciousness level were significantly decreased in the Lidocaine Group. Vital signs didn’t change between groups. Both groups, the Lidocaine Group and  the Control Group, show changes between the blood samples taken before and after injecting the  substance, possibly due to the data collection technique used in this study.

Conclusions. Lidocaine has analgesic and soothing effects without affecting vital signs or blood parameters. However, this was not the result for the buttocks, possibly due to failure detecting  pain, the technique used to cause pain or lower sensitivity in the buttocks.