Determination of Minimum Infusion Rate and Cardiorespiratory Effects of Total Intravenous Anesthesia of Ketofol With or Without Lidocaine, Fentanyl or Dexmedetomidine in Dogs

Abstract Background: Ketofol is a 1:1 mixture of ketamine and propofol that has been proposed for induction and maintenance of anesthesia aiming to provide more cardiovascular stability and less undesirable impacts compared to the use of propofol and ketamine alone. However, it has been associated with exacerbated respiratory depression in dogs. Diminishing the dose of ketofol may improve cardiovascular effects and attenuate respiratory depression. The present study was designed to evaluate the effect of adding lidocaine, fentanyl or dexmedetomidine at the required dose and cardiorespiratory variables in dogs undergoing total intravenous anesthesia (TIVA) with ketofol. In phase I, twelve dogs were induced and maintained with two out of four anesthetic regimens of KET: ketofol (4 mg/kg and 0.3 mg/kg/min, respectively), KLD; ketofol and lidocaine (1.5 mg/kg and 0.25 mg/kg/min, respectively), KFN: ketofol and fentanyl (LD: 5 µg/kg and 0.1 µg/kg/min, respectively) and KDX: ketofol and dexmedetomidine (2 µg/kg and 2 mg/kg/h, respectively). Minimum infusion rate (MIR) of ketofol was determined in this phase. Subsequently, in phase II, other twelve dogs were given the same anesthetic regimens for 60 min similar to the previous phase, except the infusion rate of ketofol. Cardiorespiratory variables were recorded in predetermined interval. Results: In phase I, mean MIR of ketofol for KET, KLD, KFN and KDX were determined to have decreasing manner as 0.35, 0.23, 0.15, and 0.08 mg/kg/min, respectively. In phase II, the times of recovery events were shorter in KFN and KDX than KET and KLD. Notably, HR was significantly higher than baseline during anesthesia in KET and KLD, which also was significantly lower than baseline in KFN and KDX at several time points. Significant higher values of MAP were observed over time in KDX. In all treatments, there was a decrease in respiratory rate and pH as well as an increase in PCO2 during the anesthesia session. Conclusions: It was concluded that despite decreasing the dose of ketofol, none of the added drugs attenuated respiratory depression caused by ketofol.