Evaluation of the effects of Epidural Lidocaine, Xylazine, Ketamine and their combinations in Dogs
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Epidural anaesthesia is one of the method of administering drugs in close proximity to their site of action either at the receptors in the dorsal horn of the spinal cord or at the nerves as they leave the spinal cord. The technique is part of the emerging trends in pain management in small animals, especially for surgical conditions caudal to the umbilicus. Different drug protocols have been used to provide epidural anaesthesia in dogs. The objectives of this study were: to carry out a survey of surgical procedures carried out caudal to the umbilicus in dogs, the anesthetic and analgesic drugs and techniques employed for these procedures in small animal veterinary practices in Nairobi County, Kenya; to evaluate the hematological, cardiopulmonary, rectal temperature changes, and anaesthesia and analgesia produced following lumbosacral epidural administration of lidocaine, xylazine, ketamine and their combinations in dogs. A questionnaire was used to carry out the survey on anaesthesia practices in phase one of the study. Phase two constituted the experimental study, where fifteen dogs were randomly divided into three groups (A, B and C) of five dogs each. Every animal in each group received two treatments one week apart. Each dog was premedicated with acepromazine (0.1mg/kg) intramuscularly prior to injection of the experimental drugs. Dogs in group A were injected with lidocaine epidurally (4 mg/kg) and after one week, the drug combination lidocaine-xylazine (2 mg/kg and 0.3 mg/kg, respectively). Dogs in group B were injected with xylazine epidurally (0.6 mg/kg) and one week later, with xylazine-ketamine (0.3 mg/kg and 1 mg/kg, respectively). Dogs in group C were injected with ketamine epidurally (2 mg/kg) followed one week later with the combination of lidocaine-ketamine (2 mg/kg and 1 mg/kg, respectively). Blood samples were collected at 0, 15, 30, 60, 120, 180 and 240 minutes after drug injection and the following blood parameters analyzed: hemoglobin concentration, packed cell volume, total xiii leukocyte count, total erythrocyte count, and total platelet count. Heart rate, respiratory rate and rectal temperature were assessed at 0, 5, 10, 15, 30, 45, 60, 75, 90, 120, 150, 180, 210 and 240 minutes after drug injection. Analgesia was evaluated in a 4-point rating scale at five body parts namely the last rib, mid-flank, perineum, mid-thigh and the toe and the onset and duration of analgesia calculated. Motor response was also evaluated in a 4-point rating scale at regular intervals and motor blockade indices (time to recumbency and duration of recumbency) computed. The response rate for the survey was 74.3%. The number of dogs and cats anaesthetized per week by veterinarians in Nairobi County were 5±3.53 and 2±1.39 respectively. Castration, orthopedic procedures and ovariohysterectomy were the most common surgeries carried out caudal to the umbilicus. Xylazine, ketamine and lidocaine were the most popular premedication, induction/maintenance and local anaesthetic agents respectively. Only 17.40% of the respondents reported to have used lumbosacral epidural anaesthesia in dogs. NSAIDs were the most preferred analgesic agents in dogs at 50% followed by corticosteroids 25%, opioids, anxiolytics and local anaesthetic agents each at 8.3%. Unavailability and high cost of anaesthetic and analgesic agents as well as lack of knowledge on some drugs and anaesthesia techniques were mentioned as the major constraints to the practice of optimal anaesthesia and analgesia in small animal practices. Significant (P< 0.05) decrease in total erythrocyte count, total leucocyte count, packed cell volume and hemoglobin concentration were observed following epidural injection of the six drug regimes. Xylazine, lidocaine-xylazine, lidocaine-ketamine and xylazine-ketamine significantly (P< 0.05) lowered heart rate in dogs. Lidocaine, xylazine, lidocaine-xylazine, lidocaineketamine and xylazine-ketamine significantly (P< 0.05) depressed respiratory rate in dogs.