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USE OF MEDETOMIDINE AS A PREANAESTHETIC IN BIRDS
Proceedings of the 4th International Congress of Veterinary Anaesthesia
USE OF MEDETOMIDINE AS A PREANAESTHETIC IN BIRDS M. Kalpravidh. Department of Surgery, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand. Summary Medetomidine, an a,-adrenoceptor agonist, was used to balance ketamine anaesthesia in birds. Twenty zebra doves weighing 40 to 60 g were equally divided into 2 groups. Group 1 was used to evaluate the effects of 100 mg/kg of 5% ketamine and of 0.1 mg/kg of 0.005% medetomidine in combination with 100 mg/kg of 5% ketamine. Group 2 was used to study the effects of 200 mg/kg of 5% ketamine and of 30 mg/kg of 1% pentobarbital. AU injections were made intramuscularly. Medetomidine-ketamine combination provided better analgesia, deeper anaesthesia, and smoother recovery with less wing
Materials and Methods Twenty zebra doves weighing 40 to 60 g were allowed to have free access to seed and water. Four evaluated drug regimens were 100 mg/kg of 5% ketamine (A), 0.1 mg/kg of .005% medetomidine in combination with 100 mg/kg of 5%
ketamine (B), 200 mg/kg of 5% ketamine (C), and 30 mg/kg of 1% pentobarbital (D). All injections were made intramuscularly into pectoral muscles on either side of the cariniform sterni. The animals were equally divided into 2 groups of ten birds each. Group 1 was used to evaluate the effects of regimens A and B while the effects of regimens C and D were investigated in group 2. Each group was subdivided into 2 sets of five birds each. Drug evaluation scheduled for the first set of group 1 was started with regimen A followed by regimen B 2 weeks later. For the second set of birds, regimen B was first evaluated 2 weeks prior to regimen A investigation. As in group 1, regimens C and D were investigated in the 2 sets of group 2 at 2week interval and the order of drug evaluation within each set was reversed to each other.
flapping than with ketamine alone. The anaesthetic effect of the combination was comparable to that of pentobarbital but recovery was smoother. The selection of preanaesthetic and anaesthetic medications is one of the problems associated with avian surgery. Medetomidine is a new sedative compound whose effect is mediated via the stimulation of the central a,-adrenoceptors. It provides analgesic and sedative or anaesthetic effects in dogs and cats (Vihii, 1989) and sedative effect in zebra doves (Cherdchanpipat et al., 1989). This study was designed to evaluate the effect of medetomidine in combination with ketamine, the anaesthetic of choice for a number of avian species.The combination effect was compared with the effect of ketamine given alone, and with the effect of pentobarbital, the anaesthetic used successfully for decades by a number of practitioners.
Consciousness, behaviour, and recumbency duration were observed. Toe squeezing was used to stimulate the leg withdrawal reflex in response to pain which reflected stages of anaesthesia. The reflex was noted as follows: + 3 leg immediately withdrawn and animal struggled briefly when the toe pinched (narcosis), +2 brisk reflex (light anaesthesia), +1 delayed sluggish response (medium anaesthesia), and 0 absent reflex (deep anaesthesia). The reflex was evaluated at 5, 10, 20, and 30 min post-admini245
Proceedinas of the 4th International Conmess of Veterinalv Anaesthesia
stration, and then every 15 min thereafter until the +3 reflex response resumed. Results Induction Incoordination was observed in 1 to 2, 1 to 5, 1 to 5, and 2 to 9 min following administration of 100 mg/kg of ketamine (A), me-
detomidine-ketamine combination (B), ux) mg/kg of ketamine (C) and pentobarbital (D), respectively. Opisthotonos and excitement with wing flapping were found in all birds receiving regimen A and in a few receiving regimen C. Most birds given regimen A exhibited signs of head drop and t d raise.
..
Recumbencv After drue admlrustrabons Some birds lay down on their sides while others slept on their backs. The recumbency duration was started after a bird was placed on its back, if not initially in that position, and ended when the animal could turn over by itself to stay in sternal recumbency. Means + SEM of recumbency durations after administering regimens A, B, C, and D were 67t 12, 275+63, 177+20, and 273t37 min, respectively. Both paired t-test and analysis of variance showed significantly (Pc0.05) that the recumbency duration after regimen B administration was longer
than that after giving regimen A, and regimen D provided longer recumbency duration as compared with the duration after giving regimen C. Analysis of variance also indicated the recumbency duration following regimen A administration was significantly (Pc0.05) shorter than that observed after injecting either regimen C or D. Regimen B provided the recumbency duration comparable to the durations after giving regimens C and D. Anaesthesia Mean durations t SEM of fight, medium, and deep anaesthesia and the number of birds developing various stages of anaesthesia following drug administrations are shown in table 1. Medium anaesthesia was the deepest stage of anaesthesia induced by either dose rate of ketamine while the medetomidine-ketamine combination could provide deep anaesthesia. The eyes of most birds receiving regimen A remained open, while a few birds closed their eyes but opened in response to sound as seen in all birds receiving regimen C. By chi square test of the number of birds developing deep anaesthesia, the anaesthetic effects of pentobarbital and medetomidine combined with ketamine were not significantly (P>.O5) different but they were better than that of either dose rate of ketamine.
Table 1. Mean durations + SEM (min of light, medium, and deep anaesthesia, and the number(n) of birds showing various stages of anaesthesia following various IM drug administrations.
Medetomidine (0.1 mg/kg)
Proceedings of the 4th International Congress of Veterinary Anaesthesia
Recovery Recovery from either dose rate of ketamine was violent. The animals were excited with vigorous incoordination and wing flapping. Slight incoordination and less wing flapping were seen in birds receiving medetomidine - ketamine combination. Incoordination and feather preening were evident in most of birds receiving pentobarbital.
mulation of various reflexes shows considerable variation. Assessment of the depth of general anaesthesia in buds is therefore difficult. Pinching the interdigital web or the undersurface of the foot produces unreliable or less reliable response (Coles, 1985). The scaled parts of the legs and digits of birds are two body areas where painful sensations are readily provoked (Sanford, 1971). Therefore, to assess the depth of anaesthesia in this study, toe squeezing was used for testing the reflex response.
Discussion Medetomidine has been proved by this study to be an effective preanaesthetic agent for avian
To avoid the effect of repeating the same order of drug administrations within each group, sequence of drug evaluation in each set was reversed to each other. A two-week lapse between administrations was allowed for the drugs to be metabolized and eliminated before the animal was used for the next observation. AU birds had free access to seed and water before receiving each drug regimen. Because of the high basal metabolic rate of avian species, there is increased risk of fatal hypoglycaemia from food deprivation (Lumb and Jones, 1984).
anaesthesia. It provided an additive effect to ketamine to produce a satisfactory anaesthesia with an adequate degree of analgesia and smooth induction and recovery. The combination of medetomidine and ketamine induced deep anaesthesia which was not seen after giving either dose rate of ketamine alone. The anaesthetic effect of this combmation was comparable to that of pentobarbital. Both dose rates of ketamine used in this study has been recommended for birds weighing less than 100 g (Boever, 1%5).Possibly due to the hallucinatory properties of ketamine, excitement with wing flapping during induction and recovery were observed in all buds receiving the lower dose rate. On the contrary, smooth induction and recovery were seen when medetomidine was used with ketamine. Pentobarbital possesses sufficient anaesthetic effect and it can be given intramuscularly in rates of 30 to 40 mg/kg to anaestheth most small cage birds (Jones, 1965). However, due to its narrow margin of safety (Sanford, 1971), a high mortality rate in zebra doves was reported when a dose rate of 40 mg/kg was a d m i t e r e d intramuscularly (Cherdchanpipat et al., 1989).
References Boever WJ. and Wright W. (1975) Use of Ketamine for Restraint and Anaesthesia of Birds. V.M.SA.C. 70,86-88.
Cherdchanpipat S., Shupchukum K., Pongpichayasiri K., and Kalpravidh M. (1989) Dose Response Study of Medetomidine in Birds. Thai J. Vet. Med.19(2), 65-73. Coles B.H. (1985) Anaesthesia. In Avian Medicine and Surgery. Blackwell Scientific Publications, London, pp. 102-122. Jones O.G. (1%5)Restraint and Anaesthesia of Small Cage Birds. J. Small Anim. Pract. 6,3139.
The response of the individual birds to the sti-
247
Praxedines of the 4th International Con-
Lumb W.V. and Jones E.W. (1984) Anaesthesia of Laboratory and Zoo Animals. In Veterinary Anaesthesia. Lea & Febiger, Philadelphia, pp. 413-491. Sanford J. (1971) Avian Anaesthesia. In Textbook of Veterinary Anaesthesia. Ed. by L.R. Soma, Williams & Wilkins Co.,Baltimore, pp. 359-368. Viha-Vahe T. (1989) Clinical Evaluation of Medetomidine, a Novel Sedative and Analgesic Drug for Dogs and Cats. Ada. Vet. S a d . 30(3), 267-273.
248
of Vcterinaw Anaesthesia
USE OF MEDETOMIDINE AS A PREANAESTHETIC IN BIRDS M. Kalpravidh. Department of Surgery, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand. Summary Medetomidine, an a,-adrenoceptor agonist, was used to balance ketamine anaesthesia in birds. Twenty zebra doves weighing 40 to 60 g were equally divided into 2 groups. Group 1 was used to evaluate the effects of 100 mg/kg of 5% ketamine and of 0.1 mg/kg of 0.005% medetomidine in combination with 100 mg/kg of 5% ketamine. Group 2 was used to study the effects of 200 mg/kg of 5% ketamine and of 30 mg/kg of 1% pentobarbital. AU injections were made intramuscularly. Medetomidine-ketamine combination provided better analgesia, deeper anaesthesia, and smoother recovery with less wing
Materials and Methods Twenty zebra doves weighing 40 to 60 g were allowed to have free access to seed and water. Four evaluated drug regimens were 100 mg/kg of 5% ketamine (A), 0.1 mg/kg of .005% medetomidine in combination with 100 mg/kg of 5%
ketamine (B), 200 mg/kg of 5% ketamine (C), and 30 mg/kg of 1% pentobarbital (D). All injections were made intramuscularly into pectoral muscles on either side of the cariniform sterni. The animals were equally divided into 2 groups of ten birds each. Group 1 was used to evaluate the effects of regimens A and B while the effects of regimens C and D were investigated in group 2. Each group was subdivided into 2 sets of five birds each. Drug evaluation scheduled for the first set of group 1 was started with regimen A followed by regimen B 2 weeks later. For the second set of birds, regimen B was first evaluated 2 weeks prior to regimen A investigation. As in group 1, regimens C and D were investigated in the 2 sets of group 2 at 2week interval and the order of drug evaluation within each set was reversed to each other.
flapping than with ketamine alone. The anaesthetic effect of the combination was comparable to that of pentobarbital but recovery was smoother. The selection of preanaesthetic and anaesthetic medications is one of the problems associated with avian surgery. Medetomidine is a new sedative compound whose effect is mediated via the stimulation of the central a,-adrenoceptors. It provides analgesic and sedative or anaesthetic effects in dogs and cats (Vihii, 1989) and sedative effect in zebra doves (Cherdchanpipat et al., 1989). This study was designed to evaluate the effect of medetomidine in combination with ketamine, the anaesthetic of choice for a number of avian species.The combination effect was compared with the effect of ketamine given alone, and with the effect of pentobarbital, the anaesthetic used successfully for decades by a number of practitioners.
Consciousness, behaviour, and recumbency duration were observed. Toe squeezing was used to stimulate the leg withdrawal reflex in response to pain which reflected stages of anaesthesia. The reflex was noted as follows: + 3 leg immediately withdrawn and animal struggled briefly when the toe pinched (narcosis), +2 brisk reflex (light anaesthesia), +1 delayed sluggish response (medium anaesthesia), and 0 absent reflex (deep anaesthesia). The reflex was evaluated at 5, 10, 20, and 30 min post-admini245
Proceedinas of the 4th International Conmess of Veterinalv Anaesthesia
stration, and then every 15 min thereafter until the +3 reflex response resumed. Results Induction Incoordination was observed in 1 to 2, 1 to 5, 1 to 5, and 2 to 9 min following administration of 100 mg/kg of ketamine (A), me-
detomidine-ketamine combination (B), ux) mg/kg of ketamine (C) and pentobarbital (D), respectively. Opisthotonos and excitement with wing flapping were found in all birds receiving regimen A and in a few receiving regimen C. Most birds given regimen A exhibited signs of head drop and t d raise.
..
Recumbencv After drue admlrustrabons Some birds lay down on their sides while others slept on their backs. The recumbency duration was started after a bird was placed on its back, if not initially in that position, and ended when the animal could turn over by itself to stay in sternal recumbency. Means + SEM of recumbency durations after administering regimens A, B, C, and D were 67t 12, 275+63, 177+20, and 273t37 min, respectively. Both paired t-test and analysis of variance showed significantly (Pc0.05) that the recumbency duration after regimen B administration was longer
than that after giving regimen A, and regimen D provided longer recumbency duration as compared with the duration after giving regimen C. Analysis of variance also indicated the recumbency duration following regimen A administration was significantly (Pc0.05) shorter than that observed after injecting either regimen C or D. Regimen B provided the recumbency duration comparable to the durations after giving regimens C and D. Anaesthesia Mean durations t SEM of fight, medium, and deep anaesthesia and the number of birds developing various stages of anaesthesia following drug administrations are shown in table 1. Medium anaesthesia was the deepest stage of anaesthesia induced by either dose rate of ketamine while the medetomidine-ketamine combination could provide deep anaesthesia. The eyes of most birds receiving regimen A remained open, while a few birds closed their eyes but opened in response to sound as seen in all birds receiving regimen C. By chi square test of the number of birds developing deep anaesthesia, the anaesthetic effects of pentobarbital and medetomidine combined with ketamine were not significantly (P>.O5) different but they were better than that of either dose rate of ketamine.
Table 1. Mean durations + SEM (min of light, medium, and deep anaesthesia, and the number(n) of birds showing various stages of anaesthesia following various IM drug administrations.
Medetomidine (0.1 mg/kg)
Proceedings of the 4th International Congress of Veterinary Anaesthesia
Recovery Recovery from either dose rate of ketamine was violent. The animals were excited with vigorous incoordination and wing flapping. Slight incoordination and less wing flapping were seen in birds receiving medetomidine - ketamine combination. Incoordination and feather preening were evident in most of birds receiving pentobarbital.
mulation of various reflexes shows considerable variation. Assessment of the depth of general anaesthesia in buds is therefore difficult. Pinching the interdigital web or the undersurface of the foot produces unreliable or less reliable response (Coles, 1985). The scaled parts of the legs and digits of birds are two body areas where painful sensations are readily provoked (Sanford, 1971). Therefore, to assess the depth of anaesthesia in this study, toe squeezing was used for testing the reflex response.
Discussion Medetomidine has been proved by this study to be an effective preanaesthetic agent for avian
To avoid the effect of repeating the same order of drug administrations within each group, sequence of drug evaluation in each set was reversed to each other. A two-week lapse between administrations was allowed for the drugs to be metabolized and eliminated before the animal was used for the next observation. AU birds had free access to seed and water before receiving each drug regimen. Because of the high basal metabolic rate of avian species, there is increased risk of fatal hypoglycaemia from food deprivation (Lumb and Jones, 1984).
anaesthesia. It provided an additive effect to ketamine to produce a satisfactory anaesthesia with an adequate degree of analgesia and smooth induction and recovery. The combination of medetomidine and ketamine induced deep anaesthesia which was not seen after giving either dose rate of ketamine alone. The anaesthetic effect of this combmation was comparable to that of pentobarbital. Both dose rates of ketamine used in this study has been recommended for birds weighing less than 100 g (Boever, 1%5).Possibly due to the hallucinatory properties of ketamine, excitement with wing flapping during induction and recovery were observed in all buds receiving the lower dose rate. On the contrary, smooth induction and recovery were seen when medetomidine was used with ketamine. Pentobarbital possesses sufficient anaesthetic effect and it can be given intramuscularly in rates of 30 to 40 mg/kg to anaestheth most small cage birds (Jones, 1965). However, due to its narrow margin of safety (Sanford, 1971), a high mortality rate in zebra doves was reported when a dose rate of 40 mg/kg was a d m i t e r e d intramuscularly (Cherdchanpipat et al., 1989).
References Boever WJ. and Wright W. (1975) Use of Ketamine for Restraint and Anaesthesia of Birds. V.M.SA.C. 70,86-88.
Cherdchanpipat S., Shupchukum K., Pongpichayasiri K., and Kalpravidh M. (1989) Dose Response Study of Medetomidine in Birds. Thai J. Vet. Med.19(2), 65-73. Coles B.H. (1985) Anaesthesia. In Avian Medicine and Surgery. Blackwell Scientific Publications, London, pp. 102-122. Jones O.G. (1%5)Restraint and Anaesthesia of Small Cage Birds. J. Small Anim. Pract. 6,3139.
The response of the individual birds to the sti-
247
Praxedines of the 4th International Con-
Lumb W.V. and Jones E.W. (1984) Anaesthesia of Laboratory and Zoo Animals. In Veterinary Anaesthesia. Lea & Febiger, Philadelphia, pp. 413-491. Sanford J. (1971) Avian Anaesthesia. In Textbook of Veterinary Anaesthesia. Ed. by L.R. Soma, Williams & Wilkins Co.,Baltimore, pp. 359-368. Viha-Vahe T. (1989) Clinical Evaluation of Medetomidine, a Novel Sedative and Analgesic Drug for Dogs and Cats. Ada. Vet. S a d . 30(3), 267-273.
248
of Vcterinaw Anaesthesia