- Email: [email protected]
Use of Infrared Thermography to Detect Intrasynovial Injections in Horses
Journal of Equine Veterinary Science 33 (2013) 257-260
Journal of Equine Veterinary Science journal homepage: www.j-evs.com
Original Research
Use of Infrared Thermography to Detect Intrasynovial Injections in Horses Tatiana Figueiredo DVM, MSc, Bruna Dzyekanski DVM, Cláudia T. Pimpão DVM, MSc, PhD, Andressa B. Silveira DVM, PhD, Luiz G. Capriglione DVM, MSc, Pedro Vicente Michelotto Jr. DVM, MSc, PhD Animal Science, School of Agricultural Sciences and Veterinary Medicine, Pontifícia Universidade Católica do Parana (PUCPR), Curitiba, Paraná, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Received 26 March 2012 Received in revised form 8 June 2012 Accepted 11 July 2012 Available online 14 September 2012
Athletic horses often experience painful conditions of the musculoskeletal system, but their ability to compete can be prolonged using certain anesthetic agents. The present study investigated the ability of thermography to detect fetlock and middle carpal intrasynovial injections of bupivacaine hydrochloride in five mares. Saline injections were performed in the contralateral limbs. Thermographic evaluation was conducted at the dorsal and palmar aspects before (basal) and 15, 30, 60, 90, 120, and 1440 minutes after injection. The intrasynovial treatments resulted in increased limb temperature, with fetlock temperatures higher on the dorsal aspect at 15, 30, and 60 minutes and on the palmar aspect from 15 to 1440 minutes (P < .05) after the bupivacaine and saline injections. Increased carpal temperature was detected on the dorsal aspect at 60 and 90 minutes (P < .05). The present study demonstrates that thermography can be used to detect intrasynovial injections in horses. Ó 2013 Elsevier Inc. All rights reserved.
Keywords: Horse Thermography Bupivacaine Horse welfare Joint
1. Introduction Sport horses are predisposed to a variety of orthopedic conditions that can cause lameness and poor performance, resulting in significant economic losses and immense frustration to the owners. Over the past few years, many drugs have been used to control musculoskeletal pain and allow unsound horses to perform without lameness [1], although the treatment of horses during a competition is ethically prohibited. With advancements of antidoping screening techniques, the use of systemic analgesics has been restricted, and injectable local medications can be an option. Anesthetic blocks using bupivacaine hydrochloride and mepivacaine hydrochloride, usually used for local anesthesia during surgical procedures and lameness evaluations, have been performed [2]. However, injecting intra-articular Corresponding author at: Pedro Vicente Michelotto Jr., DVM, MSc, PhD, Rua Luiz Alberti, 169 Campo Comprido, Curitiba, Paraná 81220050, Brazil. E-mail address: [email protected] (P.V. Michelotto). 0737-0806/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jevs.2012.07.003
blocks before exercise is prohibited by some associations because it represents a risky procedure for the athletic horse if performed before competitions, shows, or prepurchase examinations. Recently, among other mechanisms, the Fédération Equestre Internationale (http://www.feicleansport.org/) has included thermography as a detection method for procedures used to either hypersensitize or desensitize horses’ limbs. Additionally, thermography has previously been described as a reliable technique for detection of anesthetic procedures used on horses [3,4]. Infrared thermography (IT) is a noninvasive method currently used as a complementary tool to diagnose lameness in horses [5,6]. The basic principle of IT involves the transformation of surface heat from an object into a pictorial representation. The color gradients generated reflect differences in the emitted heat. Variations from pictures of a normal horse’s surface heat can be used to detect lameness or regions of inflammation. Thermography has been used to evaluate several different clinical syndromes, not only for the diagnosis of inflammation [7] but also as a way to monitor the progression of healing [5].
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T. Figueiredo et al. / Journal of Equine Veterinary Science 33 (2013) 257-260
Interestingly, Hoogmoed and Snyder [3] found that IT can be used to detect the injection of analgesic and neurolytic agents and surgical palmar digital neurectomy in horses. Their study concluded that local injection of the lumbar region as well as suspensory and tibial nerve infiltration with a neurolytic agent produced detectable thermal patterns for 2 days. Similarly, Holmes et al. [4] concluded that the changes in the superficial temperature of a perineural anesthetic injection lasted 45 minutes. Thermography may also be used to detect other types of injections used to eliminate pain before competitions, such as intra-articular blocks; however, there are no specific studies or data to confirm this possibility. The objective of this study was to evaluate the ability of IT to detect intraarticular injections of local anesthetic into the fetlock and middle carpal joints of horses. We hypothesized that intraarticular anesthesia would result in temporary changes in surface temperature over injection sites that are detectable by thermography. 2. Material and Methods
A week after the evaluation of the fetlock joint, the same procedure was repeated for the investigation of the bupivacaine hydrochloride and saline injections in the middle carpal joint. Joint preparation was the same as described for fetlock evaluation. This study was approved by the Committee on Animal Experimentation of the Pontifical Catholic University of Paraná, Curitiba, Brazil, registered as number 523, and is in accordance with the guidelines in the Care and Use of Animals. 2.3. Statistical Analysis The thermographic images were blindly analyzed by one of the authors using QuickReport (Flir Systems, São Paulo, Brazil). The mean temperature for each time and aspect was compared with the mean basal temperature obtained for the group on that specific aspect, using a paired t test in GraphPad Prism version 5.0 for Windows (San Diego, CA). A value of P < .05 was considered significant, and all values are represented as mean standard deviation.
2.1. Chemicals 3. Results Bupivacaine hydrochloride (Marcaína; Astra Zeneca Laboratory, São Paulo, Brazil) and 0.9% sodium chloride (Sanobiol Laboratory, São Paulo, Brazil) were obtained from sources in Brazil. 2.2. Animals and Study Design Five adult mixed-bred mares (body weight range, 390-470 kg) from the Pontifical Catholic University of Paraná herd were used in this study. Five hours before each procedure, the horses were cleaned and placed in stalls without bedding and with no access to natural sunlight. A ThermaCAM i40 (Flir Systems, São Paulo, Brazil) was used to obtain the images of the front fetlocks and middle carpal joints from a distance of 1 m from the dorsal and palmar aspects and was always operated by the same professional (B.D.). Every experiment began at the end of the day to avoid daily temperature variation, and the basal temperatures of the examined areas (fetlock and middle carpal joints) were obtained in each view aspect immediately before horse preparation. Sedation was not applied, and, if necessary, a twitch was used for restraint during joint injection. Initially, the fetlock joints were aseptically prepared using a 5-minute povidoneeiodine scrub followed by alcohol, and then randomly chosen for bupivacaine (Bupi group) or 0.9% sodium chloride (saline; Sal group) injection. The limb was suspended in a non-weight-bearing position with the fetlock flexed, and a 1.5-inch 21-G needle was used to inject 5.0 mL of bupivacaine hydrochloride into the lateral palmar aspect of the articular surface of the third metacarpal bone and the articular surface of the lateral sesamoid bone [8]. The contralateral joint received 5.0 mL of saline. The thermographic images were obtained 15, 30, 60, 90, 120, and 1440 minutes after the injections, on each aspect of evaluation. The same protocol was repeated after 7 days, inverting the limbs, resulting in n ¼ 10 for each group.
The fetlock joint injection of bupivacaine hydrochloride resulted in higher temperatures at 15-1140 minutes at the palmar aspect, being highest from 15 to 90 minutes (P < .01, n ¼ 10) (Fig. 1). The increased temperature was also detected at the dorsal aspect of evaluation from 15 to 120 minutes (P < .05, n ¼ 10) (Fig. 2). Additionally, fetlock temperatures were higher after saline injection and were observed at the dorsal aspect from 15 to 120 minutes and at the palmar aspect from 15 to 1440 minutes (P < .05, n ¼ 10). There were no differences between the temperatures after bupivacaine hydrochloride or saline injections at each evaluation time. The middle carpal joint injection of bupivacaine hydrochloride resulted in higher temperatures from 60 to 90 minutes at the dorsal aspect (Fig. 3) and at 60 minutes at the palmar aspect (Fig. 4) (P < .05, n ¼ 10) compared with
Fig. 1. Mean and standard error of skin temperature ( C) at the palmar aspect of the fetlock joint after intrasynovial injection of bupivacaine hydrochloride (Bupi) and 0.9% sodium chloride.(Sal). a, P < .05 versus basal temperature for both Bupi and Sal groups.
T. Figueiredo et al. / Journal of Equine Veterinary Science 33 (2013) 257-260
259
Fig. 2. Mean and standard error of skin temperature ( C) at the dorsal aspect of the fetlock joint after intrasynovial injection of bupivacaine hydrochloride (Bupi) and 0.9% sodium chloride (Sal). a, P < .05 versus basal temperature of the Bupi group; b, P < .05 versus basal temperature of the Sal group.
Fig. 4. Mean and standard error of skin temperature ( C) at the palmar aspect of the middle carpal joint after intrasynovial injection of bupivacaine hydrochloride (Bupi) and 0.9% sodium chloride (Sal). a, P < .05 versus basal temperature of the Bupi group.
basal temperatures. There was a difference between the Bupi and Sal groups detected at the dorsal aspect at 30 minutes (23.7 1.2 vs. 22.2 1.4, P < .05) because temperature showed a decrease at 15 and 30 minutes in the Sal group.
hydrochloride, saline, or the injection itself. Although the amount of blood flow has not been routinely measured, IT is considered a reliable noninvasive technique for evaluation of the blood flow in equine limbs [9]. Therefore, in the present study, thermographic detection of increased limb temperatures after the injection procedures was interpreted as an increase in blood flow. Turner [9] emphasized the importance of a temperature-controlled and sunlight-protected environment for a thermographic evaluation to obtain accurate results. To control for this in the present study, horses were evaluated at the same time at the end of the day, at temperatures between 20 C and 30 C, as recommended by Simon et al. [10]. Moreover, a control group was not included, as limb temperatures were obtained for each region before injection, which were then used as the basal values for comparison with the postinjection values. Interestingly, the postinjection limb temperatures increased in both treatment groups compared with the basal temperatures. Although the bupivacaine seemed to result in higher temperatures than did the saline injection, a significant difference between Bupi and Sal groups was only detected in the dorsal middle carpal joint at 30 minutes. This suggests that the injection itself initiates an inflammatory response responsible for the increased limb temperatures detected by IT, a hypothesis supported by the study by Guinard et al. [11], who demonstrated that tissue trauma caused by the needle passage resulted in an increase in blood flow. Nevertheless, bupivacaine hydrochloride is a local anesthetic agent with an effective period of 180-480 minutes. Local injection causes vasodilatation and increased capillary blood flow in humans [11]. It should be noted that the anesthetic and the circulatory effects most likely have different lengths of duration. In the present study, the increased limb temperature of the Bupi group was detected until 1440 minutes. In a study by Kay et al. [12], which used a lipopolysaccharide-induced lameness model for the fetlock joint, intrasynovial mepivacaine effectively abolished lameness within 45 minutes, whereas edema was reduced by the inclusion of triamcinolone. However, mepivacaine
4. Discussion The novelty of the present study is that IT evaluation is a suitable method to detect intrasynovial anesthetic procedures that can be performed in athletic horses, specifically the intrasynovial injection of bupivacaine hydrochloride in the fetlock and middle carpal joints. Moreover, results of the present study corroborate with the efforts of the Fédération Equestre Internationale Clean Sport Program for horses’ welfare in equestrian competitions. Intrasynovial injection into the fetlock and middle carpal joints resulted in higher limb temperatures, possibly due to increased regional blood flow caused by bupivacaine
Fig. 3. Mean and standard error of skin temperature ( C) at the dorsal aspect of the middle carpal joint after intrasynovial injection of bupivacaine hydrochloride (Bupi) and 0.9% sodium chloride (Sal). a, P < .05 versus basal temperature of the Bupi group.
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T. Figueiredo et al. / Journal of Equine Veterinary Science 33 (2013) 257-260
affected the horses’ gait for 120 minutes after a palmar digital nerve block [13]. The intrasynovial injection of 0.9% sodium chloride resulted in increased limb temperatures similar to the Bupi group. It is possible that this was a result of the needle trauma during injection [11] or due to the saline injection itself. Recently, an increase in white blood cell count and total protein levels was reported, within 24 hours after needle insertion alone as well as after the injection of 2.5 mL into the middle carpal joints of horses [14]. In this study [14], it was concluded that the procedures elicited an inflammatory response, detected by IT in the present study. Other pharmacological agents, such as corticosteroids, sodium hyaluronate, and polysulfated glycosaminoglycan, are commonly injected in horses’ joints to reduce pain and inflammation [15]. Because these drugs have antiinflammatory properties, it is possible that they can attenuate the anesthetic circulatory effects and interfere with thermographic evaluation results. As no studies are available regarding this possibility, future research will be necessary to investigate it further. It should be noted that in cases in which intrasynovial anesthetic injection is suggested by thermographic examination, urine detection of anesthetic agents can confirm their use, as has been demonstrated in both humans [16] and horses [17]. In conclusion, the present study demonstrated that IT evaluation is a suitable method for the detection of intrasynovial injections of bupivacaine. The detection of saline injections suggests that the injection of other agents can also be detected, a topic for future investigation.
[2]
[3]
[4]
[5] [6]
[7]
[8]
[9] [10]
[11]
[12]
[13]
[14]
Acknowledgments [15]
The authors are grateful to the Pontifical Catholic University for the support provided for this research.
[16]
References
[17]
[1] Taddei L, Benoit M, Sukta A, Peterson J, Gaensslen RE, Negrusz A. Detection of various performance enhancing substances in specimens
collected from race horses in Illinois: A five-year experience. J Anal Toxicol 2011;35:438-43. Kwok WH, Leung DK, Leung GN, Wan TS, Wong CH, Wong JK. Screening of drugs in equine plasma using automated on-line solidphase extraction coupled with liquid chromatography-tandem mass spectrometry. J Chromatogr A 2010;1217:3289-96. Hoogmoed LM, Snyder JR. Use of infrared thermography to detect injections and palmar digital neurectomy in horses. Vet J 2002;164:129-41. Holmes LC, Gaughan EM, Gorondy DA, Hogge S, Spire MF. The effect of perineural anesthesia on infrared thermographic images of the forelimb digits of normal horses. Can Vet J 2003;44:392-6. Eddy AL, Hoogmoed LM, Snyder JR. The role of thermography in the management of equine lameness. Vet J 2001;162:172-81. Tunley BV, Henson FM. Reliability and repeatability of thermographic examination and the normal thermographic image of the thoracolumbar region in the horse. Equine Vet J 2004;36:306-12. Levet T, Martens A, Devisscher L, Duchateau L, Bogaert L, Vlaminck L. Distal limb cast sores in horses: Risk factors and early detection using thermography. Equine Vet J 2009;41:18-23. Moyer W, Schumacher J, Schumacher J. Fetlock: Collateral sesamoidean. In: Moyer W, Schumacher J, Schumacher J, editors. A guide to equine joint injection and regional anesthesia. Yardley, PA: Veterinary Learning Systems; 2007. p. 26-7. Turner TA. Thermography as an aid to the clinical lameness evaluation. Vet Clin N Am Equine Pract 1991;7:311-38. Simon EL, Gaughan EM, Epp T, Spire M. Influence of exercise on thermographically determined surface temperatures of thoracic and pelvic limbs in horses. J Am Vet Med Assoc 2006;229:1940-4. Guinard JP, Carpenter RL, Morell RC. Effect of local anesthetic concentration on capillary blood flow in human skin. Reg Anesth 1992;17:317-21. Kay AT, Bolt DM, Ishihara A, Rajala-Schultz PJ, Bertone AL. Antiinflammatory and analgesic effects of intra-articular injection of triamcinolone acetonide, mepivacaine hydrochloride, or both on lipopolysaccharide-induced lameness in horses. Am J Vet Res 2008;69:1646-54. Bidwell LA, Brown KE, Cordier A, Mullineaux DR, Clayton HM. Mepivacaine local anesthetic duration in equine palmar digital nerve blocks. Equine Vet J 2004;36:723-6. Kawcak CE, McIlwraith CW. Comparison of synovial fluid in middle carpal joints undergoing needle aspiration, infusion with saline, and infusion with a combination of N-acetyl-D-glucosamine, hyaluronic acid, and sodium chondroitin sulfate. J Equine Vet Sci 2011;31:155-9. Caron JP. Intra-articular injections for joint disease in horses. Vet Clin N Am Equine Pract 2005;21:559-73. Lombardo-Agüí M, Cruces-Blanco C, García-Campaña AM. Capillary zone electrophoresis with diode-array detection for analysis of local anaesthetics and opium alkaloids in urine samples. J Chromatogr B Analyt Technol Biomed Life Sci 2009;877:833-6. Nelis SA, Sievers C, Jarrett M, Nissen LM, Kirkpatrick CM, Shaw PN. Quantitative analysis of lignocaine and metabolites in equine urine and plasma by liquid chromatography-tandem mass spectrometry. J Chromatogr B Analyt Technol Biomed Life Sci 2010;878:2018-22.
Journal of Equine Veterinary Science journal homepage: www.j-evs.com
Original Research
Use of Infrared Thermography to Detect Intrasynovial Injections in Horses Tatiana Figueiredo DVM, MSc, Bruna Dzyekanski DVM, Cláudia T. Pimpão DVM, MSc, PhD, Andressa B. Silveira DVM, PhD, Luiz G. Capriglione DVM, MSc, Pedro Vicente Michelotto Jr. DVM, MSc, PhD Animal Science, School of Agricultural Sciences and Veterinary Medicine, Pontifícia Universidade Católica do Parana (PUCPR), Curitiba, Paraná, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history: Received 26 March 2012 Received in revised form 8 June 2012 Accepted 11 July 2012 Available online 14 September 2012
Athletic horses often experience painful conditions of the musculoskeletal system, but their ability to compete can be prolonged using certain anesthetic agents. The present study investigated the ability of thermography to detect fetlock and middle carpal intrasynovial injections of bupivacaine hydrochloride in five mares. Saline injections were performed in the contralateral limbs. Thermographic evaluation was conducted at the dorsal and palmar aspects before (basal) and 15, 30, 60, 90, 120, and 1440 minutes after injection. The intrasynovial treatments resulted in increased limb temperature, with fetlock temperatures higher on the dorsal aspect at 15, 30, and 60 minutes and on the palmar aspect from 15 to 1440 minutes (P < .05) after the bupivacaine and saline injections. Increased carpal temperature was detected on the dorsal aspect at 60 and 90 minutes (P < .05). The present study demonstrates that thermography can be used to detect intrasynovial injections in horses. Ó 2013 Elsevier Inc. All rights reserved.
Keywords: Horse Thermography Bupivacaine Horse welfare Joint
1. Introduction Sport horses are predisposed to a variety of orthopedic conditions that can cause lameness and poor performance, resulting in significant economic losses and immense frustration to the owners. Over the past few years, many drugs have been used to control musculoskeletal pain and allow unsound horses to perform without lameness [1], although the treatment of horses during a competition is ethically prohibited. With advancements of antidoping screening techniques, the use of systemic analgesics has been restricted, and injectable local medications can be an option. Anesthetic blocks using bupivacaine hydrochloride and mepivacaine hydrochloride, usually used for local anesthesia during surgical procedures and lameness evaluations, have been performed [2]. However, injecting intra-articular Corresponding author at: Pedro Vicente Michelotto Jr., DVM, MSc, PhD, Rua Luiz Alberti, 169 Campo Comprido, Curitiba, Paraná 81220050, Brazil. E-mail address: [email protected] (P.V. Michelotto). 0737-0806/$ - see front matter Ó 2013 Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jevs.2012.07.003
blocks before exercise is prohibited by some associations because it represents a risky procedure for the athletic horse if performed before competitions, shows, or prepurchase examinations. Recently, among other mechanisms, the Fédération Equestre Internationale (http://www.feicleansport.org/) has included thermography as a detection method for procedures used to either hypersensitize or desensitize horses’ limbs. Additionally, thermography has previously been described as a reliable technique for detection of anesthetic procedures used on horses [3,4]. Infrared thermography (IT) is a noninvasive method currently used as a complementary tool to diagnose lameness in horses [5,6]. The basic principle of IT involves the transformation of surface heat from an object into a pictorial representation. The color gradients generated reflect differences in the emitted heat. Variations from pictures of a normal horse’s surface heat can be used to detect lameness or regions of inflammation. Thermography has been used to evaluate several different clinical syndromes, not only for the diagnosis of inflammation [7] but also as a way to monitor the progression of healing [5].
258
T. Figueiredo et al. / Journal of Equine Veterinary Science 33 (2013) 257-260
Interestingly, Hoogmoed and Snyder [3] found that IT can be used to detect the injection of analgesic and neurolytic agents and surgical palmar digital neurectomy in horses. Their study concluded that local injection of the lumbar region as well as suspensory and tibial nerve infiltration with a neurolytic agent produced detectable thermal patterns for 2 days. Similarly, Holmes et al. [4] concluded that the changes in the superficial temperature of a perineural anesthetic injection lasted 45 minutes. Thermography may also be used to detect other types of injections used to eliminate pain before competitions, such as intra-articular blocks; however, there are no specific studies or data to confirm this possibility. The objective of this study was to evaluate the ability of IT to detect intraarticular injections of local anesthetic into the fetlock and middle carpal joints of horses. We hypothesized that intraarticular anesthesia would result in temporary changes in surface temperature over injection sites that are detectable by thermography. 2. Material and Methods
A week after the evaluation of the fetlock joint, the same procedure was repeated for the investigation of the bupivacaine hydrochloride and saline injections in the middle carpal joint. Joint preparation was the same as described for fetlock evaluation. This study was approved by the Committee on Animal Experimentation of the Pontifical Catholic University of Paraná, Curitiba, Brazil, registered as number 523, and is in accordance with the guidelines in the Care and Use of Animals. 2.3. Statistical Analysis The thermographic images were blindly analyzed by one of the authors using QuickReport (Flir Systems, São Paulo, Brazil). The mean temperature for each time and aspect was compared with the mean basal temperature obtained for the group on that specific aspect, using a paired t test in GraphPad Prism version 5.0 for Windows (San Diego, CA). A value of P < .05 was considered significant, and all values are represented as mean standard deviation.
2.1. Chemicals 3. Results Bupivacaine hydrochloride (Marcaína; Astra Zeneca Laboratory, São Paulo, Brazil) and 0.9% sodium chloride (Sanobiol Laboratory, São Paulo, Brazil) were obtained from sources in Brazil. 2.2. Animals and Study Design Five adult mixed-bred mares (body weight range, 390-470 kg) from the Pontifical Catholic University of Paraná herd were used in this study. Five hours before each procedure, the horses were cleaned and placed in stalls without bedding and with no access to natural sunlight. A ThermaCAM i40 (Flir Systems, São Paulo, Brazil) was used to obtain the images of the front fetlocks and middle carpal joints from a distance of 1 m from the dorsal and palmar aspects and was always operated by the same professional (B.D.). Every experiment began at the end of the day to avoid daily temperature variation, and the basal temperatures of the examined areas (fetlock and middle carpal joints) were obtained in each view aspect immediately before horse preparation. Sedation was not applied, and, if necessary, a twitch was used for restraint during joint injection. Initially, the fetlock joints were aseptically prepared using a 5-minute povidoneeiodine scrub followed by alcohol, and then randomly chosen for bupivacaine (Bupi group) or 0.9% sodium chloride (saline; Sal group) injection. The limb was suspended in a non-weight-bearing position with the fetlock flexed, and a 1.5-inch 21-G needle was used to inject 5.0 mL of bupivacaine hydrochloride into the lateral palmar aspect of the articular surface of the third metacarpal bone and the articular surface of the lateral sesamoid bone [8]. The contralateral joint received 5.0 mL of saline. The thermographic images were obtained 15, 30, 60, 90, 120, and 1440 minutes after the injections, on each aspect of evaluation. The same protocol was repeated after 7 days, inverting the limbs, resulting in n ¼ 10 for each group.
The fetlock joint injection of bupivacaine hydrochloride resulted in higher temperatures at 15-1140 minutes at the palmar aspect, being highest from 15 to 90 minutes (P < .01, n ¼ 10) (Fig. 1). The increased temperature was also detected at the dorsal aspect of evaluation from 15 to 120 minutes (P < .05, n ¼ 10) (Fig. 2). Additionally, fetlock temperatures were higher after saline injection and were observed at the dorsal aspect from 15 to 120 minutes and at the palmar aspect from 15 to 1440 minutes (P < .05, n ¼ 10). There were no differences between the temperatures after bupivacaine hydrochloride or saline injections at each evaluation time. The middle carpal joint injection of bupivacaine hydrochloride resulted in higher temperatures from 60 to 90 minutes at the dorsal aspect (Fig. 3) and at 60 minutes at the palmar aspect (Fig. 4) (P < .05, n ¼ 10) compared with
Fig. 1. Mean and standard error of skin temperature ( C) at the palmar aspect of the fetlock joint after intrasynovial injection of bupivacaine hydrochloride (Bupi) and 0.9% sodium chloride.(Sal). a, P < .05 versus basal temperature for both Bupi and Sal groups.
T. Figueiredo et al. / Journal of Equine Veterinary Science 33 (2013) 257-260
259
Fig. 2. Mean and standard error of skin temperature ( C) at the dorsal aspect of the fetlock joint after intrasynovial injection of bupivacaine hydrochloride (Bupi) and 0.9% sodium chloride (Sal). a, P < .05 versus basal temperature of the Bupi group; b, P < .05 versus basal temperature of the Sal group.
Fig. 4. Mean and standard error of skin temperature ( C) at the palmar aspect of the middle carpal joint after intrasynovial injection of bupivacaine hydrochloride (Bupi) and 0.9% sodium chloride (Sal). a, P < .05 versus basal temperature of the Bupi group.
basal temperatures. There was a difference between the Bupi and Sal groups detected at the dorsal aspect at 30 minutes (23.7 1.2 vs. 22.2 1.4, P < .05) because temperature showed a decrease at 15 and 30 minutes in the Sal group.
hydrochloride, saline, or the injection itself. Although the amount of blood flow has not been routinely measured, IT is considered a reliable noninvasive technique for evaluation of the blood flow in equine limbs [9]. Therefore, in the present study, thermographic detection of increased limb temperatures after the injection procedures was interpreted as an increase in blood flow. Turner [9] emphasized the importance of a temperature-controlled and sunlight-protected environment for a thermographic evaluation to obtain accurate results. To control for this in the present study, horses were evaluated at the same time at the end of the day, at temperatures between 20 C and 30 C, as recommended by Simon et al. [10]. Moreover, a control group was not included, as limb temperatures were obtained for each region before injection, which were then used as the basal values for comparison with the postinjection values. Interestingly, the postinjection limb temperatures increased in both treatment groups compared with the basal temperatures. Although the bupivacaine seemed to result in higher temperatures than did the saline injection, a significant difference between Bupi and Sal groups was only detected in the dorsal middle carpal joint at 30 minutes. This suggests that the injection itself initiates an inflammatory response responsible for the increased limb temperatures detected by IT, a hypothesis supported by the study by Guinard et al. [11], who demonstrated that tissue trauma caused by the needle passage resulted in an increase in blood flow. Nevertheless, bupivacaine hydrochloride is a local anesthetic agent with an effective period of 180-480 minutes. Local injection causes vasodilatation and increased capillary blood flow in humans [11]. It should be noted that the anesthetic and the circulatory effects most likely have different lengths of duration. In the present study, the increased limb temperature of the Bupi group was detected until 1440 minutes. In a study by Kay et al. [12], which used a lipopolysaccharide-induced lameness model for the fetlock joint, intrasynovial mepivacaine effectively abolished lameness within 45 minutes, whereas edema was reduced by the inclusion of triamcinolone. However, mepivacaine
4. Discussion The novelty of the present study is that IT evaluation is a suitable method to detect intrasynovial anesthetic procedures that can be performed in athletic horses, specifically the intrasynovial injection of bupivacaine hydrochloride in the fetlock and middle carpal joints. Moreover, results of the present study corroborate with the efforts of the Fédération Equestre Internationale Clean Sport Program for horses’ welfare in equestrian competitions. Intrasynovial injection into the fetlock and middle carpal joints resulted in higher limb temperatures, possibly due to increased regional blood flow caused by bupivacaine
Fig. 3. Mean and standard error of skin temperature ( C) at the dorsal aspect of the middle carpal joint after intrasynovial injection of bupivacaine hydrochloride (Bupi) and 0.9% sodium chloride (Sal). a, P < .05 versus basal temperature of the Bupi group.
260
T. Figueiredo et al. / Journal of Equine Veterinary Science 33 (2013) 257-260
affected the horses’ gait for 120 minutes after a palmar digital nerve block [13]. The intrasynovial injection of 0.9% sodium chloride resulted in increased limb temperatures similar to the Bupi group. It is possible that this was a result of the needle trauma during injection [11] or due to the saline injection itself. Recently, an increase in white blood cell count and total protein levels was reported, within 24 hours after needle insertion alone as well as after the injection of 2.5 mL into the middle carpal joints of horses [14]. In this study [14], it was concluded that the procedures elicited an inflammatory response, detected by IT in the present study. Other pharmacological agents, such as corticosteroids, sodium hyaluronate, and polysulfated glycosaminoglycan, are commonly injected in horses’ joints to reduce pain and inflammation [15]. Because these drugs have antiinflammatory properties, it is possible that they can attenuate the anesthetic circulatory effects and interfere with thermographic evaluation results. As no studies are available regarding this possibility, future research will be necessary to investigate it further. It should be noted that in cases in which intrasynovial anesthetic injection is suggested by thermographic examination, urine detection of anesthetic agents can confirm their use, as has been demonstrated in both humans [16] and horses [17]. In conclusion, the present study demonstrated that IT evaluation is a suitable method for the detection of intrasynovial injections of bupivacaine. The detection of saline injections suggests that the injection of other agents can also be detected, a topic for future investigation.
[2]
[3]
[4]
[5] [6]
[7]
[8]
[9] [10]
[11]
[12]
[13]
[14]
Acknowledgments [15]
The authors are grateful to the Pontifical Catholic University for the support provided for this research.
[16]
References
[17]
[1] Taddei L, Benoit M, Sukta A, Peterson J, Gaensslen RE, Negrusz A. Detection of various performance enhancing substances in specimens
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