Physiological and cardiopulmonary effects of Tiletamine–Zolazepam-Ketamine-Xylazine (TKX) combination as an induction agent for ovariohysterectomy under isoflurane maintenance anaesthesia in dogs

Introduction

Balanced anaesthesia is an essential approach in veterinary practice that combines different anaesthetic drugs and techniques to provide hypnosis, analgesia, muscle relaxation and physiological stability while minimizing adverse effects (Muir and Hubbell, 2014) [16] . Tiletamine-zolazepam is a combination, consisting of equal proportions of tiletamine hydrochloride and zolazepam hydrochloride (Nam et al., 2013) [17] . The pharmacological actions of these two drugs are complementary, with tiletamine producing dissociative anaesthesia, analgesia, and immobilization, while zolazepam, a benzodiazepine derivative, provides muscle relaxation and tranquilization (Saikumar et al., 2023) [23] . Owing to these combined effects, the tiletamine-zolazepam combination is widely used as a pre-anaesthetic agent, for induction prior to inhalational anaesthesia, and for producing general anaesthesia during diagnostic procedures as well as minor and major surgical interventions (Pawson and Forsyth, 2008; Nam et al., 2013) [19,17] . α₂-agonists are commonly combined with dissociative anaesthetics to improve anaesthetic quality, recovery and counteract undesirable excitatory effects, thereby facilitating balanced anaesthesia in dogs (Gomez Villamandos et al., 2013; Mahantesh et al., 2024) [6,14] . Present study was undertaken to evaluate the physiological and cardio pulmonary effects of tiletamine-zolazepam-ketamine-xylazine anesthetic combination in dogs.

Materials and Methods

Approval for the anaesthetic study was obtained from the Institutional Animal Ethics Committee, College of Veterinary Science, Proddatur (Approval No. 11-CVScPdtr/IAEC/2025 dated 16.09.2025). Six healthy non-oestrous, non-pregnant bitches of varying age group presented for ovariohysterectomy were selected for anaesthetic study and subjected to preanesthetic screening including clinical and haemato-biochemical examination. Food and water were withheld for 12 hours and 6 hours respectively prior to anaesthetic trail. All the animals were pre-medicated with inj. Atropine sulphate at the dose rate of 0.02 mg/kg body weight intramuscularly, 5mins prior to induction of anaesthesia Induction was carried out by administration of Inj. Tiletamine-Zolazepam at a dose rate of 2.5 mg/kg body weight, Inj. Ketamine hydrochloride at a dose rate of 2.5 mg/kg body weight and Inj. Xylazine at a dose rate of 0.5 mg/kg body weight mixture (TKX) in a single syringe intravenously to the effect. Anaesthesia was maintained with isoflurane inhalant anaesthesia. Physiological and cardiopulmonary parameters were recorded throughout the anaesthetic period in all dogs. Heart rate, respiratory rate, and rectal temperature were recorded before and immediately after induction, subsequently at 15-minute time intervals during anaesthetic maintenance and after recovery. Peripheral oxygen saturation (SpO₂) and mean arterial pressure (MAP) were measured at 15-minute time intervals during maintenance anaesthesia and after recovery using a multiparameter vital signs monitor.

Statistical analysis

The data generated during the study were analysed using SPSS software version 22.0. comparison of mean values within each treatment group before and after drug administration were carried out using the paired t-test. The effects of treatment and various time intervals during the anaesthetic period were assessed using repeated measures analysis of variance (ANOVA) under the general linear model. P-value of ≤ 0.05 was considered statistically significant, whereas a P-value of ≤ 0.01 was considered highly significant.

Results and Discussion

Withholding of food and water for 12 hours and 6 hours respectively prior to induction anaesthesia was found effective in preventing vomiting in all the dogs (Tiwari et al. (2024) [25] . In the present study, excessive salivation was not observed in all the animals. Administration of atropine sulphate as pre-anaesthetic (0.02 mg/kg) was effective in controlling excessive salivation. Present findings were in accordance with Alvaides et al. (2008) [1] . Induction with Tiletamine-Zolazepam-Ketamine-Xylazine mixture found to be adequate and facilitated smooth induction, good muscle relaxation with easy endotracheal intubation. This concurred with the reports of Chen et al. (2005) and Koli et al. (2021) [9] . A significant decrease (P≤0.05) in respiratory rate was observed following induction in all the animals. Present findings were in accordance with the observations of Beck et al. (2025) [3] . Tiletamine is well known to produce transient respiratory depression after induction and give rise to apneustic breathing pattern (Pereira et al. 2019) [20] . The decrease in respiratory rate immediately after induction might be attributed to depressant action of anaesthetic agents on pulmonary function, as reported by Kwon et al. (2003) [10] . However, a highly significant(P≤0.01) decrease in respiratory rate observed during isoflurane inhalant anaesthesia at 30 th minute. Similar findings were reported by Galloway et al. (2004) [5] , who observed dose-dependent respiratory depression during maintenance of isoflurane anaesthesia. There was a significant (P≤0.05) increase in heart rate following induction in all the animals. Findings were in accordance with Chen et al. (2005) who reported that increase in heart rate after induction might be attributed to the combined sympathetic stimulating effect of tiletamine and the vagolytic effect of atropine. In the present study, a highly significant (P≤0.01) decrease in heart rate was observed at the 30 th and 45 th minute of maintenance anaesthesia, which might be attributed to the dose-dependent cardiovascular depressant action of isoflurane. Similar findings were reported by Galloway et al. (2004) [5] and Sousa et al. (2008) [24] . Rectal temperature showed a non-significant decrease following induction. Present observations were in accordance with Li et al. (2015) [12] . The decrease in rectal temperature might be attributed to decreased metabolic rate and central nervous system depression caused by the anaesthetic agents, as reported by Lu et al. (2013). A significant (P≤0.05) decrease in rectal temperature was noticed at 30 th minute during the maintenance period compared to pre-induction values. Li et al. (2015) [12] reported that decrease in rectal temperature might be due to the heat loss associated with cold inhaled anaesthetic gas, abdominal lavage and laparotomy procedures. Saturation peripheral oxygen (SpO₂) concentration recorded during maintenance anaesthesia was stable and there was no significant difference SpO₂ within the groups, relatively higher values observed during the isoflurane maintenance anaesthesia. This might be attributed to 100% oxygen supplementation during isoflurane maintenance anaesthesia. This was in accordance with the observation of Patel et al. (2022) [18] and Manjusha et al. (2023) [15] who reported SpO₂ values above 98%. Mean arterial blood pressure values showed a progressive and statistically significant decrease throughout the maintenance period of anaesthesia. Present findings were in line with observations of Galloway et al. (2004) [5] and Lemke (2004) [11] . The reduction in mean arterial pressure might be attributed to the depressant effect of isoflurane on myocardial contractility along with its arterial and venous vasodilatory actions (Bayan et al. 2024) [2] .

Conclusion

In the present study, Tiletamine-Zolazepam-Ketamine-Xylazine anaesthetic protocol resulted in smooth and rapid induction, adequate muscle relaxation. The physiological and cardiopulmonary parameters evaluated throughout the anaesthetic period remained within normal physiological limits in all animals. Although variations in these parameters were observed, they were transient and did not result in any clinically significant adverse effects. The findings of the present investigation indicate that the anaesthetic protocol employed was safe, effective, and well tolerated in dogs.

Acknowledgement

zolazepam-sevoflurane anaesthesia with or without dexmedetomidine and butorphanol premedication in dogs. Indian Journal of Animal Sciences. 2024;94(6):506-512.

References

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