Studies to Evaluate the Safety of Constant Rate Infusions of Dexmedetomidine, Ketamine and Lidocaine Alone or in Combination during Isoflurane Anesthesia in Horses

Abstract

Background: Horses mount a huge stress response to anesthesia when compared to other animals, hence are risky candidates for anesthesia. Inhalant anesthetic agents offer more control to anesthetic depth and facilitate rapid recovery, hence are considered to be safer than intravenous agents for surgical procedures requiring more than an hour, however, newer drug combinations are being explored to minimize the undesired consequences and dose rate of inhalant agents. The present study explored the safety of dexmedetomidine, ketamine and lidocaine constant rate infusion alone or as a combination along with Isoflurane for safer anesthesia in horses.Methods: The study was conducted on 28 horses divided into S, D, DK and DKL groups having 7 animals in each. Xylazine (1 mg/kg) and butorphanol (0.05mg/kg) were given intravenously for premedication. Ketamine (2 mg/kg) and midazolam (0.2 mg/kg) were used for induction and anesthesia was maintained with isoflurane. Normal saline (1000ml/hour), Dexmedetomidine (2µg/kg/hr), Dexmedetomidine and ketamine (2 µg/kg/hr and 2 mg/kg/hr) and Dexmedetomidine, ketamine and lidocaine (2 µg/kg/hr, 2 mg/kg/hr and 2 mg/kg/h) were given as CRI in groups S, D, DK and DKL, respectively. Thiopentone sodium (250mg bolus, 5%) was given as a fast intravenous bolus whenever required. Anesthetic efficacy was evaluated based on clinical, haemato-biochemical, hemodynamic, and endocrine variables.Result: A significant decline in mean arterial pressure was noticed in group DKL but changes in CVP and SpO2 in different groups were non-significant. Higher Blood glucose and low Insulin levels were seen in group DK during 45-60 min. Constant rate infusions of Dexmedetomidine, Ketamine and Lidocaine alone or in combination produced a significant sparing effect on Isoflurane and thiopentone while they improved peri-operative quality of anesthesia in horses.

Clinical and Hematological Effect of Constant Rate Infusion of Ketamine Alone and Ketamine-dexmedetomidine Combination on Isoflurane Anesthesia in Horses

“…The reduction may be caused by the activation of central and pre-synaptic sympathetic neuronal alpha-2 adrenoceptors in group KD by dexmedetomidine use (Moens, 2000). A decrease in heart rate in groups KD might be due to the overiding effect of dexmeditomidine over ketamine (Gopinathan et al, 2021). A decrease in RR might also be attributed to co-administration of thiopental administration which often causes direct depression of the respiratory in the medulla.…”

“…Newer alpha 2 agonists like Dexmedetomidine had been suggested for continuous rate infusions in equine and it had been found to reduce the MAC value of isoflurane significantly (Schauvliege et al, 2011). Balanced anaesthetic combinations were being explored by various authors to find safer combinations that can be used in conjunction with inhalant agents to reduce the side effects of inhalant agents and the drug sparing effects (Gopinathan et al, 2021). Other characters like smooth induction, recovery, cardiovascular and pulmonary profile and stress parameters had to be evaluated for comprehensively assessing the safety of such drugs for application in surgeries.Present study explored 1 safety of balanced anesthetic protocols with ketamine alone or in combination with dexmedetomidine, as constant rate infusion along with isoflurane anesthesia for surgeries in horses.…”

Effect of Constant Rate Infusion of Different Anaesthetic Adjuvants Undergoing Thiopentone Sodium Total Intravenous Anaesthesia in Horses

“…All horses underwent scoring for sedation (0-3), Ataxia (0-3), muscle relaxation (0-3) and quality of analgesia (0-3) (Gopinathan et al, 2021). The palpebral reflex (1-4) and Corneal reflex (1-4) were graded.…”

“…Cardiovascular function is least disturbed in intravenous anesthesia. The delivery of anesthetics can be safer and controlled through constant rate infusions (CRI) (Gopinathan et al, 2021). It is also quite adaptable with protocols of intravenous anesthesia.…”