單獨使用 Tiletamine-Zolazepam 和與 Medetomidine 或 Xylazine 併用於斑龜之麻醉作用和 Atipamezole 對 Medetomidine-Tiletamine-Zolazepam 麻醉之翻轉效果

The objective of this study was to evaluate the anesthetic effect of Zoletil 50 (ZOL) alone and combined with medetomidine (MED) or xylazine (XYL) in Chinese stripe-necked turtles (Ocadia sinensis). ZOL, a non-opioid, non-barbiturate injectable anesthetic, is composed of two ingredients, tiletamine and zolazepam, in equal amounts by weight (1:1). In fact, zolazepzm can improve the anesthetic effects of tiletamine and results in better muscle relaxation. However, ZOL can cause different anesthetic effects in reptiles, and it could not induce enough analgesia to reach surgical aneathetic in turtles. Alpha-2 adrenergic agonist has potent effect to reduce the required volume of ZOL and enhance the depth of anesthesia. Among these alpha-2 agonists, only MED and XYL are currently used in reptile anesthesia. Atipamezole（ATZ）is the specific antagonist of MED. In this study, we tested various regimens, including ZOL (20 mg/kg), ZOL-MED (20-0.025, 20-0.05 and 20-0.1 mg/kg) and ZOL-XYL (20-2 and 20-4 mg/kg). The experiments also assessed the ability of ATZ (0.125 mg/kg) to reverse the effect of ZOL-MED (20-0.05 mg/kg). Six turtles were used in each regimen, and drugs were injected into the muscle of forelimbs. The depth of anesthetic was evaluated by withdrawal reflexes of the limbs and neck when touched or pinched the limbs and neck. The induction time was defined as the time of loss all withdrawal reflexes of limbs and neck responding to touch. Surgical anesthesia was defined as loss of withdrawal reflexes of all limbs responding to pinch. Significant individual variability and no reliable anesthesia were noted while ZOL was used alone. Two out of six turtles reached anesthesia for a very short duration (3 to 7 min). In contrast, except for one turtle of the ZOL-MED 20-0.025 mg/kg group did not lose withdrawal reflexes of hind limbs responding to pinch, other 17 turtles in ZOL-MED experiments could reach surgical anesthesia, but there was no significant difference statistically among 3 groups (P>0.05). Moreover, the turtles of the least and the largest dosages had greater variability in anesthetic duration (97±26 min and 151 ± 29 min), compared to the medium dosage (121 ± 7 min). In ZOL-XYL experiments, both regimens (20-2 and 20-4 mg/kg) could reach to the induction of anesthesia and maintain for the duration of 51±10 min and 62±10 min, respectively. However, neither group attained surgical anesthesia in which the turtles lost withdrawal reflex to pinch for all four limbs. Significant heart rates depression after all of regimens administration was observed (p 0.05). All regimens of turtles could voluntarily increased respiratory rates and returned to the baseline nearby before completely recovery. ATZ (0.125 mg/kg, IM) effectively reverse the effect of ZOL-MED (20-0.05 mg/kg) anesthesia in 1 to 3 min. The recovery time was much shorter than that of the control group (33 ± 5 min vs. 131 ± 39 min, p<0.05). Heart and respiratory rates returned to the baseline within 18 min. The results indicated that ZOL-MED at 20-0.05 mg/kg could induce most stable surgical anesthesia (121.3 ± 7.1 min) among these regimens. The anesthetic effect of ZOL-MED could be effectively and safely antagonized by 0.125 mg/kg atipamazole in Chinese stripe-necked turtles. ZOL (20 mg/kg) combined with XYL (2-4 mg/kg) could enhance anesthetic effect stably, but all of these combinations could not reach surgical anesthesia in Chinese stripe-necked turtles. All turtles in this study no side effects been recorded and survived after anesthesia demonstrating the safety of these anesthetic regimens in Chinese stripe-necked turtles.