A CLINICAL STUDY ON THE USE OF THIOPENTONE AND PROPOFOL AS INDUCTION AGENTS FOR ISOFLURANE ANAESTHESIA IN DOGS
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Date
2010
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SRI VENKATESWARA VETERINARY UNIVERSITY TIRUPATI - 517 502. (A.P.) INDIA
Abstract
ABSTRACT:
The present clinical study was carried out on 18 dogs between 1 year to 6 years of age presented for ovariohysterectomy. These dogs were randomly divided into three groups comprising of six animals in each group. All the dogs were uniformly premedicated. In the six dogs of group I, anaesthesia was induced by intravenous administration of Thiopental sodium at the rate of 10 mg/kg body weight as a 2.5 percent solution. In dogs of group II, Propofol was used as an intravenous anaesthetic induction agent at the dose of 3 to 4 mg/kg. In the six dogs of group III, Isoflurane was used as induction agent using a face mask at 4 to 5 % concentration in oxygen. Immediately after induction, the dogs of all the three groups were intubated and anaesthesia was maintained with 1.5% to 2% inhalation of Isoflurane during the entire surgical procedure. The anaesthetic effects like induction of anaesthesia, duration of anaesthesia and recovery time and physiological parameters like temperature, heart rate, respiratory rate and Electrocardiograph (ECG) were studied before induction, during anaesthesia and after recovery from anaesthesia. Haematological parameters like TEC, TLC, Hb, DLC and biochemical parameters like AST, ALT, BUN and Serum Creatinine were recorded before induction, during anaesthesia and after recovery. The results of the present study indicated that there was no significant difference between the induction time of thiopentone and propofol, while the two groups differed significantly when compared to the use of isoflurane as the induction agent, where the induction time ranged from 210 seconds to 300 seconds (mean 262 ± 14.42). It was also observed that while thiopentone uniformly induced anaesthesia deep enough to allow intubation in all the six dogs of group I, propofol at 3 mg/kg body weight induced anaesthesia deep enough to allow intubation in only four out of the six dogs. In the other two dogs, an additional dose of 1 mg/kg body weight was necessitated. Induction with Isofluorane was possible with inhalation of 4% to 5% in oxygen in the dogs of group III. Isofluorane induction was possible only in those dogs that had friendly and docile temperament. All the three anaesthetic protocols studied produced satisfactory and safe deep surgical anaesthesia in all the dogs. In all the dogs of the three groups, recovery from anaesthesia was found to be smooth and uneventful. The dogs of group III recovered earliest from anaesthesia when compared to the other groups. Between the dogs of groups I and II, the group II dogs recovered significantly earlier. As far as the physiological parameters were concerned, the results showed that in all the dogs of groups I and II, anaesthesia resulted in a significant drop in the rectal temperature during and after induction In comparison, in the dogs of group III, the drop in the rectal temperature was observed only after anaesthetic recovery. The heart rates did not differ either among the groups or among the intervals. The results however, showed that propofol induction caused a significant reduction of the respiratory rate in the dogs of group II during the maintenance of anaesthesia. The respiratory rate returned to normal as the dogs recovered from anaesthesia. Since these parameters did not result any clinical changes or complications and since they returned to normalcy soon, the changes were considered clinically irrelevant. The recovery from anaesthesia in all the six dogs of group III was considered excellent. In group I recovery was considered as good in all the dogs, while in the dogs of group II, excellent recovery in four dogs and good recovery in two dogs was recorded. Haematological examination revealed that there were no significant differences in the various parameters like TEC, TLC, Hb, DLC etc in any of the three groups or the three intervals. This underscored the fact that all the anaesthetic protocols studied were safe and uneventful as far as these observations were concerned The results of the present clinical study clearly revealed in all the dogs of the three groups that the various biochemical parameters studied, i.e., AST, ALT, BUN and Serum Creatinine remained within normal limits. Hence, this also conclusively proved that the three anaesthetic protocols studied were safe and did not result in any damage to the heart, liver or kidneys during the anaesthetic period. Electrocardiographic studies in the dogs of all the three groups revealed no abnormalities in the sizes of P, QRS or T- waves, no changes in the cardiac axes and no arrhythmias of any kind in any dog of any of the groups. From the results of the present study, it was concluded that all the three anaesthetic protocols produced satisfactory deep surgical anaesthesia in dogs. While 2.5% thiopentone was found to have produced sufficiently deep anaesthetic induction to allow intubation at the uniform dose of 10 mg/kg, propofol was found to be effective at 3 mg/kg in 4 dogs, two dogs required 4mg/kg iv. Induction of anaesthesia with 4 to 5% isoflurane in oxygen and its maintenance with 2% is suitable in friendly dogs and leads to quicker recovery. When anaesthesia is induced with thiopentone sodium @ 10 mg/kg body weight, the dogs can be maintained at 1.5% isoflurane inhalation in oxygen. When anaesthesia is induced either with propofol (3 to 4 mg/kg, i/v) or with 4 to 5% Isofluorane in oxygen, maintenance of anaesthesia is best done with 2% Isofluorane. All the three anaesthetic protocols studied in the present study resulted in minimal, clinically insignificant changes in the various physiological, biochemical and electrocardiographic parameters.
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