A new Technique for long time catheterization of sacral epidural canal in rabbits

Abstracts

JUSTIFICATIVA E OBJETIVOS: O objetivo deste estudo foi desenvolver uma técnica simples e prática para a cateterização crônica em canal peridural sacral de coelhos. MÉTODOS: O estudo incluiu dez coelhos com peso entre 2 e 2,5 kg. Após a anestesia e a analgesia, colocamos um cateter peridural através de uma incisão longitudinal de 2 cm na cauda acima da região do hiato sacral. Confirmamos a localização com a administração de lidocaína a 1% (nivelamento da perda sensorial e da função motora dos membros inferiores). O cateter foi introduzido através de um túnel subcutâneo até o pescoço, onde foi fixado. RESULTADOS: A implantação de cateter crônico peridural caudal foi bem-sucedida em todos os coelhos. Os cateteres permaneceram eficazmente no lugar por dez dias, sem intercorrências durante esse período. A localização do cateter foi reconfirmada por lidocaína a 1% no último dia. Após matar os animais, procedeu-se laminectomia para localização do cateter no espaço peridural. CONCLUSÕES: Há vários métodos de cateterização do espaço peridural em modelos animais na literatura. A cateterização do espaço peridural em coelhos pode ser feita através das vias atlanto-occipital, lombar ou caudal por amputação da cauda. As técnicas de cateterização intratecal e peridural descritas na literatura exigem perícia cirúrgica e conhecimento de procedimentos cirúrgicos, como laminectomia e amputação da cauda. A nossa técnica não requer grande habilidade cirúrgica, a integridade anatômica foi preservada e não houve mau posicionamento de cateter. Em conclusão, podemos sugerir que a nova técnica de cateterização peridural é simples, facilmente aplicável e pode ser usada em estudos experimentais de modelos animais.

ANATOMIA; ANESTÉSICOS, Local, lidocaína; ANIMAL, Coelho; EQUIPAMENTOS, Cateter Peridural; Espaço Epidural; TÉCNICAS ANESTÉSICAS, Regional, peridural, sacral

JUSTIFICATIVA Y OBJETIVOS: El objetivo de este estudio fue desarrollar una técnica sencilla y práctica para la cateterización crónica en canal epidural sacral de conejos. MÉTODOS: El estudio incluyó diez conejos con peso entre 2 y 2,5 kg. Después de la anestesia y la analgesia, pusimos un catéter epidural por medio de una incisión longitudinal de 2 cm en la cola por encima de la región del hiato sacral. Confirmamos la localización con la administración de lidocaína al 1% (nivelación de la pérdida sensorial y de la función motora de los miembros inferiores). El catéter se introdujo por medio de un túnel subcutáneo hasta el cuello, en dónde finalmente se fijó. RESULTADOS: La implantación de catéter crónico epidural de cola fue exitosa en todos los conejos. Los catéteres permanecieron eficazmente en el lugar por diez días, sin intercurrencias durante ese período. La ubicación del catéter fue reconfirmada por la lidocaína al 1% en el último día. Después de sacrificar a los animales, se procedió a la laminectomía y se verificó la ubicación del catéter en el espacio epidural. CONCLUSIONES: En la literatura existen varios métodos de cateterización del espacio epidural en modelos animales. La cateterización del espacio epidural en conejos puede ser hecha por medio de las vías atlanto-occipital, lumbar o de cola por amputación de la cola. Las técnicas de cateterización intratecal y epidural descritas en la literatura exigen una pericia quirúrgica y el conocimiento de procedimientos quirúrgicos, como la laminectomía y la amputación de la cola. Nuestra técnica no requiere gran habilidad quirúrgica, la integridad anatómica se preservó y no hubo un mal posicionamiento del catéter. Como conclusión, podemos sugerir que la nueva técnica de cateterización epidural es sencilla, fácilmente aplicable y que puede ser usada en estudios experimentales de modelos animales.

Espacio Epidural; ANATOMIA; EQUIPOS, Cateter Eepidural; TÉCNICAS ANESTÉSICAS, Regional, epidural, sacral; ANESTÉSICOS, Local, lidocaína; ANIMAL, Conejo

SCIENTIFIC ARTICLE

^IDepartment of Anesthesiology, School of Medicine, Dokuz Eylül University, İzmir, Turkey

^IIDepartment of Anesthesiology, Alsancak State Hospital, İzmir, Turkey

Corresponding author

ABSTRACT

INTRODUCTION: In this study we aimed to develop a simple and practical technique for chronic sacral epidural catheterization of rabbits.

METHODS: We included ten rabbits weighing 2-2.5 kg in the study. After anesthesia and analgesia, we placed an epidural catheter by a 2cm longitudinal skin incision in the tail above the sacral hiatus region. We confirmed localization by giving 1% lidocaine (leveling sensory loss and motor function loss of the lower extremity). The catheter was carried forward through a subcutaneous tunnel and fixed at the neck.

RESULTS: Chronic caudal epidural catheter placement was succesful in all rabbits. The catheters stayed in place effectively for ten days. We encountered no catheter complications during this period. The localization of the catheter was reconfirmed by 1% lidocaine on the last day. After animals killing, we performed a laminectomy and verified localization of the catheter in the epidural space.

CONCLUSIONS: Various methods for catheterization of the epidural space in animal models exist in the literature. Epidural catheterization of rabbits can be accomplished by atlanto-occipital, lumbar or caudal routes by amputation of the tail. Intrathecal and epidural catheterization techniques defined in the literature necessitate surgical skill and knowledge of surgical procedures like laminectomy and tail amputation. Our technique does not require substantial surgical skill, anatomical integrity is preserved and malposition of the catheter is not encountered. In conclusion, we suggest that our simple and easily applicable new epidural catheterization technique can be used as a model in experimental animal studies.

Keywords: Anesthesia, Caudal; Catheters, Indwelling; Epidural Space; Lidocaine; Rabbits

Introduction

Epidural catheterization is among the frequently used procedures for anethesia and analgesia in humans. Local anesthetics, morphine and other opioid agents, agents like clonidine and somatostatine can be given via this route.^1-8 Many new agents are being tested for obtaining analgesia by epidural and spinal routes. Before using any agent by epidural or spinal routes in humans its effects have to be tested in experimental animals.^1,2,5,8-11 Different catheterization techniques have been developed in animals like cats, dogs and monkeys. However, maintenance and preparation of these animals are expensive and require special laboratory conditions. Rabbits are comparatively easily supplied, maintained and moniterized experimental animals used for this prupose.^1-4,7,9-12 Various techniques for chronic epidural catherization of the rabbit epidural canal have been defined in the literature. Most of these techniques require special surgical skill and experience, requiring an operating microscope in most instances.^{1,2,4,7-9,11-13} In this study we aimed to develop a simple, applicable and efficient technique for chronic sacral epidural catheterization of rabbits.

Methods

After approval from the Ethical Commitee on Experimental Animal Testing, we included 10 rabbits weighing 2-2.5 kg in the study. We brought all experimental subjects to the experiment laboratory one day prior and allowed them to adapt to the environment. The next day, we obtained anesthesia with 40 mg.kg^-1 intraperitoneal thiopental. We fixed the rabbits to the study table and draped them with sterile surgical cover; then infiltrated local anesthesia of the region to be incised in the tail with 1 mL of 1% lidocainee. We removed all hair in the incision site. Taking into consideration that the vertebral column of the rabbits is composed of seven cervical, 12 lumbar, four sacral and 15 or 16 caudal vertebrae,¹⁴ we made a 2 cm longitudinal skin incision in the tail approximately 1 cm distal to the anus in the sacral vertebral region, coinciding with the sacral hiatus with strict attention to asepsis. After recognition of the sacral hiatus, a G-18 epidural catheter (Portex; fixed end, three side ports, OD: 0.9 mm) was carried forward 5 cm cranially in the epidural canal (Fig. 1). Ten minutes later, after seeing absence of neuronal mechanical injury and hemorrhage or cerebrospinal fluid leakage by aspiration of the catheter, we confirmed placement of the catheter with an injection of 1 mL of 1% lidocaine. Leveling sensory loss and lower extremity motor function loss (dragging both extremities while walking) were considered clinical findings of sacral anesthesia. There was no motor function loss in the upper extremities, which were easily moving. The part of the catheter exiting from the tail was fixed to the skin for providing continuous placement of the catheter in the caudal canal. Sensory level of rabbits were tested with pin-prick test. Local anesthesia with 1% lidocaine was administered subcutaneously between the level determined and the neck and then the catheter was carried forward in the subcutaneous tunnel towards the neck (Fig. 2). Skin was sutured in the incised regions (Fig. 2). The catheters were kept in the rabbits for 10 days to verify efficiency. One 1ml of saline solution was used every day to inhibit catheter obstruction. On the last day, the position of the catheters were verified by 1 mL of 1% lidocaine. Afterwards, intraperitoneal high dose thiopental was administered and all animals were killed. Finally, laminectomy was performed to reconfirm the placement of the catheters in the epidural space.

Results

We achieved succesful placement of caudal epidural catheter in all rabbits. We did not encounter subarachnoidal catheterization or neurological injury in any rabbit. The catheters remained effective for ten days in all animals. No catheter related infection or any other complications were seen during this period. Laminectomy perfomed after animals killing on the tenth day revealed that the catheters were in the epidural sapce in all rabbits (Fig. 3).

Discussion

Local anesthetics, opioids and many other agents are used by epidural route for providig analgesia or sedation in humans. However before applying any agent into the epiural space, its safety and efficiency has to be proved with animal experiments.

In order to investigate neuraxial anesthesia with different agents, many different methods of chronic catheterization in animal models have been described.^1,3-7,9-13 While performing some procedures in larger animals seems feasible, supplying, maintaining, feeding, and sheltering of larger animals is expensive and demanding. Supplying, manipulating, sheltering, feeding and protection of smaller animals is cheaper and easier during a study. As in many animals, rabbits' vertebral columns are different from humans'. The vertebral column in rabbits is composed of seven cervical, 12 thoracic, seven lumbar, four sacral and 15 or 16 caudal vertebrae.¹⁴ Chronic subarachnoidal catheterization in rabbits have been defined by Langerman et al.,⁷ and Yaksh and Rudy¹³ while chronic epidural catheterization has been defined by Madsen et al.¹¹ and Malinovsky et al.,⁸ Taguchi et al.¹² Epidural catheterization can be done by atlanto-occipital, lumbar routes or by tail amputation of rabbits.^{1,2,7-9,11-13} Histopathological changes are encountered less infrequently by epidural catheterization in comparison to intrathecal catheterization.^5,11 While the atlanto-occipital approach seems practical, neurological deficits may have occured due to the movement of distal catheter end with the animal's head movements or during advancement of catheter distally.¹³ Neurological injury is less often reported with lumbar compared to atlanto-occipital approach. However laminectomy requires surgical skill.^{1,2,5,7-9,11-13} Caudal approach with tail amputation in rabbits damages anatomical integrity.¹ Percutaneous caudal approach is less invasive and recommended by some authors; however it relies on loss of resistance and is eventually a blind procedure. This increases neural damage risk and can decrease success.¹² Since Madsen et al.¹¹ have shown that 1 mL volume is distributed in Thoracic 8-9 level when given into epidural space, we used 1 mL of local anesthetic in our testing procedure. Our caudal technique does not require major surgical manipulation like laminectomy, and anatomical integrity is not distrupted as in tail amputation. In addition, unlike percutaneous approaches, our technique provides easy catheterization with direct observation of hiatus sacralis. Moreover, catheter malposition is prevented since we push the catheter forward through a subcutaneous tunnel until the neck and then fix it. The major drawback of our study is lack of histopathological studies of the spinal cord. If we had performed histopathological examination, we could also comment on the effects of chronic catheterization on the spinal cord, either favorable or unfavorable. Our technique is easily performed, does not disturb anatomical integrity, avoids catheter malposition, and is amenable to improvement. In conclusion, we think that this new technique of epidural catheterization in rabbits can be an appropriate model for investigating epidural agents in animals.

Conflicts of interest

The authors declare no conflicts of interest.

References

• 1. Arkan A, Kucukguclu S, Kupelioglu A, Maltepe F, Gokel E - New technique for catheterization of the sacral canal in rabbits. Laboratory Animal Science. 1990;71:529-535.
• 2. Aydın Z, Sayıt E, Erkin Y, Capa G, Ertay Y, Sagıroğlu E, Durak H - Effects of octreotide and morphine on the clearance rate of indium-111-pentetreotide from the epidural space. Nucl Med Commun. 2000;21:835-838.
• 3. Bahar M, Rsen M, Vickers MD - Chronic cannulation of the intradural space in the rat. Br J Anaesth.1984;56:405-410.
• 4. Castro MI, Eisenach JC - Pharmacokinetics and dynamics of intravenous, intrathecal and epidural clonidine in sheep. Anesthesiology. 1989;71:418-425.
• 5. Coombs DW, Fratkin JD - Neurotoxicology of spinal agents. Anesthesiology. 1987;66:724-726.
• 6. Durant PAC, Yaksh TL - Epidural injections of bupivacaine, morphine, fentanyl, lofentanyl and DADL in chronically implanted rats: A pharmacologic and pathologic study. Anesthesiology. 1981;64:43-53.
• 7. Langerman L, Chaimky G, Golomb E - A rabbit model for evaluation of spinal anesthesia. Chronic cannulation of the subarachnoid space. Anesth Analg. 1990;71:529-535.
• 8. Malinovsky JM, Bernard JM, Baudrimont M, Dumand JB, Lepage JY - A chronic model for experimental investigation of epidural anesthesia in the rabbit. Regional Anesthesia. 1997;22:80-85.
• 9. Canduz B, Aktug H, Mavioglu O et al. - Epidural lornoxicam administration-innocent. Journal of Clinical Neurosience. 2007;14:968-974.
• 10. Feldman HS, Covino BG - A chronic model of investigation of experimental spinal anesthesia in the dog. Anesthesiology. 1981;54:148-152.
• 11. Madsen JB, Jensen FM, Faber T, Bille-Hansen V - Chronic catheterization of the epidural space in rabbits: a model for behavioral and histopathological studies. Examination of meptazinol neurotoxicity. Acta Anesthesiol Scand. 1993;37:307-313.
• 12. Taguchi H, Murao K, Nakamura K, Uchida M, Shingu K - Percutaneous chronic catheterization in the rabbit. Acta Anesthesiol Scand. 1996;40:232-236.
• 13. Yaksh TN, Rudy TA - Chronic catheterization of the spinal subaracnoid space. Physiol Behav. 1976;17:1031-1036.
• 14. Whitehouse RH, Grove AJ - The dissection of the rabbit with an appendix on the rat. London: University Tutorial Press, 1958, p. 32-70.

A new technique for long time catheterization of sacral epidural canal in rabbits

Yüksel Erkin^I; Zeynep Aydın^II; Aydın Taşdöğen^I; Ayşe Karcı^I

Publication Dates

• Publication in this collection
  13 Nov 2013
• Date of issue
  Oct 2013

History

• Received
  24 Aug 2012
• Accepted
  31 Oct 2012