Epidural analgesia is very old technique used for many regional surgeries in humans as well as in animals. It is very wonderful technique used for regional surgeries and is helpful for intraoperative management of high risk patients, perioperative analgesia, cesarean section, and forelimb amputation and have certain advantages over general anesthesia, include safety and low cost, reduces the use amount for anesthetics drug, and long-acting drugs, are helpful in residual analgesia for up to 24 hours.
Bupivacaine Hydrochloride is amino-amine long acting local anesthetic. As compared to the lidocaine, it is four times more potent, and can show anesthetic effects up to 3-8 hours. It has high potency, prolong duration, and less degree of motor blockade effects with minimal neuro and cardio toxicity effects.
Medetomidine hydrochloride is the most potent alpha-2 adrenoceptor selective agonist. It is a racemic mixture of two optical enantiomers which are, dexmedetomidine and levomedetomidine. When alpha-2 agonists administered epidurally they produce analgesia by stimulating alpha-2 adrenergic receptors present in dorsal horn of the spinal cord, and show antinociceptive properties due to their interaction with noradrenergic receptors of the spinal cord.
The current project is designed to compare the analgesic and hematological efficacy of the Bupivacaine, Medetomidine alone and in combination as epidural analgesia in dogs. For this purpose 18 clinically healthy mongrel dogs weighing 12-15kg were selected. They were divided into three groups with each group contained six dogs (n=6). The groups were named as A, B and C respectively.
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In group A Bupivacaine HCl, at dose rate of 0.5mg/kg body weight Injected Epidurally, in group B Medetomidine HCl, at dose rate of 0.015mg/kg body weight while in group C combination of Bupivacaine Hydrochloride + Medetomidine Hydrochloride Injected Epidurally.
Time to the onset, duration, ataxia, and the anatomic extent of the analgesia were recorded. Time from injection to loss of sensation was considered as onset of the analgesia. The presence of the analgesia was taken as lack of responses to “pin pricking” and by applying hemostat pressure. Positive responses to needle prick or hemostat pressure shows the presence and anatomic extent of analgesia. The tests were repeated after every 20 minutes until animals regain sensation. Ataxia was graded as 0=none, 1= mild, 2= moderate or 3= severe.
Blood sample were collected directly from the Cephalic vein before and after administration of anesthetic drug. A total of 3 mL blood was collected each time in test tubes containing blood coagulating gel. First sample were taken before anesthetic drug administration and second sample were collected after 60 minutes for evaluation of Liver Function Test.
Results of the present study proved that, minimum time to analgesic onset were shown by group C dogs, followed by group A and group B dogs. Maximum analgesic time duration was shown by group C dogs, followed by group B and group A dogs. After 20 minutes of drug administration ataxic response were same in group A and group C dogs, as 5 out of 6 dogs had sever ataxia. At 20 and 40 minutes after administration of drug, dogs of group A and group C showed maximum spread of analgesia as compare to group B dogs, at 60 minutes post drug administration, dogs of group, A, B and C showed maximum spread of analgesia.
Liver function test were evaluated by three enzymes, Alanine Aminotransferase (ALT), Aspartate Amino Transferase (AST) and Alkaline Phosphatase (ALP). Blood samples were collected before and after 60 minutes of drug administration. First these tests were evaluated within
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each group. ALP, AST and ALP values were non-significant in alone administration of Bupivacaine HCl and Medetomidine HCl, while significant rise in ALP value were observed in group C dogs, treated with Bupivacaine HCl in combination with Medetomidine HCl. When ALT, AST, and ALP were compared among all three treatments, their results were non-significant as with minor change in P-value in post 60 minutes of anesthetic drug administration, which showed that all three treatments are independent and did not effect these parameters.
Elective and emergency surgeries of hind limbs are very common in dogs, which demand appropriate, best, and safest regional anesthesia, with minimum and prolong duration of analgesic time. Maximum, uniform, and rapid spread of analgesia and having least effects on serological parameters of the animal. Present study suggested that epidural administration of Bupivacaine HCl in combination with Medetomidine HCl proved to be the safest anesthesia by showing rapid onset, prolong duration of analgesia time, early recumbency of animal, with maximum anatomic extent of analgesia in short duration time. Combination of Bupivacaine HCl and Medetomidine HCl showed least effects on serological parameters of dogs.