Anesthesia is a reversible process and derived from Greek word “anaisthaesia” meaning “insensibility” and used to desensitize the whole or any part of the body. Anesthesia is classified by method of administration i.e. intramuscular, inhalational and intravenous. Injectable anesthesia includes Propofol, Diazepam, Acepromazine, Medetomidine, Xylazine and Ketamine. Anesthetic agent can be used alone or in combinations (Gonzalez et al. 2003).
The purpose of Anesthesia is to produce a convenient, safe, effective, and economical means of facilitating surgical procedures while minimizing stress, pain and discomfort and adverse side effects. There are many routes of administration of anesthesia; in intravenous route, the onset of action is immediate. Peak effect is rapidly obtained, duration of action is short, and effects are more intense/ profound than other routes.Many combinations of anesthesia are in use in dogs for different surgery xylazine (0.4 mg/kg IV) combination with butorpjanol (0.2 mg/kg IV), xylazine (0.4 mg/kg IV) combination with oxymorphone (0.05mg/kg IV) , xylazine (0.4 mg/kb IV) combine with morphine (0.25mg/kg) , Medetomidine (5 to 15 ug/kg combine with butophanol (0.2 mg/kg IV), Medetomidine (5 to 15 ug/kg IV) combine with oxymorphone (o.05 mg/kg) Xylazine (0.4mg/kg) combine with Ketamine (5 to 10 mg/kg IV) acepromazine (0.05 to 0.2mg/kg IV or SQ) in combination with morphine (0.4 to 0.8mg/kg IV) and diazepam or midazolam(0.2 mg/kg IV) with hydromorphone or oxymorphone( 0.1 to 0.2 mg/kg IV) use in dog and cat (Greene 1999).
Detomidine is a selective α2-adrenoceptor agonist with useful sedative, analgesic and muscle relaxation properties and is widely used as a tranquilizing or pre-anaesthetic medication in veterinary medicine But it induces cardiovascular side-effects such as hypertension, hypotension, bradycardia and dysrhythmia.detomidine. It produces prolonged and intense analgesia. Nature of the analgesic effect appears to be wide, producing a reduced response to be a secondary result of the central nervous system experimental stimulation and exhibiting a clinical effect in the horse with colic. Detomidine can be used as a safe and effective pre anaesthetic resulting in smooth induction and recovery (EL-Kammar et al. 2014).
Xylazine Hcl has been widely used as a preanesthetic drug and for immobilizing dogs for diagnostic procedures (Short 1987).Xylazine is the shortest acting alpha2-adrenergic agonist..A problem with alpha2-adrenergic agonists is that they may respond suddenly to stimulation, especially to touch. The combination of opioid drugs with the alpha2-adrenergic agonists appears to reduce such sudden reactions and a synergistic effect regarding sedation and antinociception has been suggested. Additionally, all alpha2-adrenergic agonists have a dose-dependent effect on cardiovascular function. By adding an opioid drug, dose requirements of alpha2-adrenergic agonists may be reduced and cardiopulmonary function improved. The addition of opioids does not further impair cardiovascular function.The combination of xylazine and butorphanol at the doses generally used in clinical practice produces minimal and transient haemodynamic effects and no significant respiratory depression. There is no ‘blinded’ randomized crossover study regarding the xylazine sparing effects of butorphanol on sedation of horses. There are limited reports on the respiratory effects of butorphanol alone or in combination with the α2-agonist xylazine in horses, but the effects of the combination on pulmonary gas exchange have not been clarified (Ringer et al. 2012).
Butorphanol is an opioid agonist-antagonist with good analgesic effects. Butorphanol is used in veterinary medicine as pain reliever and cough suppressant. It induces only mild sedation and has minimum adverse effects to the cardiovascular system. It may cause mild lowering of the heart rate and arterial pressure or slight respiratory depression. It exerts a depressive action on the respiratory system. It should not use in patient with liver disease because it cannot be eliminated and may accumulated to toxic level (Raušer and Lexmaulova, 2002).It is believed to be more effective against visceral rather than somatic pain. The antagonist property towards μ-receptors results in a ceiling analgesic effect with increasing doses. However in dogs doses between 0•2 and 0•8 mg/kg have been reported to provide visceral analgesia in vivo .Butorphanol is a dose-related respiratory depressant and causes small decreases in arterial blood pressure and heart rate (Vettorato and Bacco 2011).
Castration is indicated for reproductive neutering, modification of behavior patterns, testicular neoplasia, severe testicular or scrotal trauma or injury, refractory orchitis, benign prostatic hyperplasia, perianal gland adenoma, perineal hernia, and scrotal urethrostomy in dogs. There is no specific anesthetic method for castration. Routinely castration surgery can be performed under general anesthesia or local anesthesia (Kim et al. 2004).
Unlike other laboratory animals that are commonly used forresearch purpose, non-human primates and dogs are also used for research work. Their use in the biological researchrequires special considerations, regarding their care and housing, and more specifically their handling and restraining. Since non-human primates and dogs present special hazards to handlers, particularlybecause of the danger of bites and zoonotic infections (Fortman et al. 2001).
Deaths due to anesthesia are lesser in dogs (1 in 601) than rabbits (1 in 72) that are the third most commonly anaesthetized pet animal in the United Kingdom (Brodbelt et al. 2005).