Interact CardioVasc Thorac Surg 2007;6:705-707. doi:10.1510/icvts.2007.157867
© 2007 European Association of Cardio-Thoracic Surgery
Work in progress report - Experimental |
Chronic lymphatico-venous bypass: surgical technique and aftercare in a porcine model
Guillaume Chanoit*,
Pierre J. Ferré and
Hervé P. Lefebvre
UMR181 Experimental Pathophysiology and Toxicology, INRA, ENVT, National Veterinary School, 23 chemin des Capelles, 31076 Toulouse Cedex 03, France
Received 16 April 2007;
received in revised form 8 August 2007;
accepted 10 August 2007
 Part of this study was presented at the European College of Veterinary Surgeons Meeting, Verlbert, Germany, 2001.
*Corresponding author. North Carolina State University, College of Veterinary Medicine, 4700 Hillsborough Street, Raleigh NC 27606, USA.
E-mail address: guillaume_chanoit{at}ncsu.edu (G. Chanoit).
 |
Abstract
|
|---|
We describe a chronic model of lymphatico-venous bypass in pigs with emphasis to surgical considerations, major per- and postoperative complications. A catheter (silicone or heparin coated polyurethane) was inserted in the thoracic duct of nine pigs via a right intercostal thoracotomy. A second catheter was surgically inserted in the jugular vein and the bypass was secured on the back of the animals. Pigs were monitored for capnography, end-tidal carbon dioxide, systolic, diastolic and mean blood pressure, heart rate, and rectal temperature. Apnea was recorded in every pig in the recovery period leading to one death. During the postoperative period, ventricular tachycardia in 2/9 pigs and hypothermia in 5/9 pigs were recorded. Bypass was effective in 5/9 pigs. Clotting occurred only with silicone catheters (1/2) but not with heparin-coated catheters. In the heparin-coated catheters group, bypass was patent up to 15 days with no major complication recorded. Sampling of lymph was allowed from 2 to 15 days. The immediate postoperative period is critical and should be carefully monitored. Although complications were present, the surgical technique was efficient. Chronic catheterization of thoracic duct is useful in biomedical research in the fields of intensive care, gastro-enterology, pharmacokinetic and hematology studies.
Key Words: Lymphatic; Pig; Chronic; Catheter
|
1. Introduction
|
|---|
Repeated lymph sampling is challenging because of the size and fragility of lymphatic vessels. As lymphatic pathway is preferential for several compounds, it is interesting to develop a model of chronic catheterization of lymph vessel. A pig model is widely used in cardiovascular studies [1] and the preferential implantation site for lymph collection is the thoracic duct (TD) through a thoracic approach [2].
In 1973, one study described the anatomy and method of acute (maximum time recorded: 8 h) cannulation of the TD in pigs [2]. More recently, the surgical technique for chronic (up to eight days) TD catheterization in pigs was developed [3]. However, in this study, the surgical technique is briefly explained and the per- and postoperative periods are not documented.
We describe here the detailed technique for chronic catheterization of TD in pigs, and document complications encountered in the per- and postoperative period.
|
2. Materials and methods
|
|---|
2.1. Animals
Nine large-white pigs weighing 25±3.5 kg at the time of surgery, aging from 3 to 4 months were used in this study. They were housed individually in pens (80/80/120 cm). They were fed with commercial food (MAXIPIG, UAC, L'Isle-en-Dodon, France, 500 g/j) and water ad libitum. The pigs were acclimated with daily handling for 10–30 days prior to surgery. During this period their behavior was recorded.
2.2. Catheters
The first two pigs were catheterized with silicone catheters (Silastic, Dow Corning, Michigan, inner diameter (i.d.): 1.5 mm and outer diameter (o.d.): 3 mm). For the other pigs, polyurethane, no luer, heparin-coated catheters were used (CBAS-C70 or C50 Solo-Cat, UNO Roestvaststaal B.V., The Netherlands). Two sizes (7 or 5 French) were used depending on the size of the TD (i.d.: 1.3 or 1.0 mm, o.d.: 2.5 or 1.7 mm, respectively, and length: 60 cm). Each catheter came with two movable beads that could be moved to the desired location on the catheter.
2.3. Surgical procedure
The protocol of this study was approved by the Animal Care Committee of our institution and was in accordance with the Guidelines of the Guide for Care and Use of Laboratory Animals.
Pigs were fasted for 12 h and premedicated with acepromazine (CALMIVET, Vetoquinol, 0.2 mg/kg, IM) 1h prior to induction of anesthesia. An indwelling venous catheter was placed in an auricular vein and thiopental (NESDONAL, Merial, 20 mg/kg, IV) was injected. The intubation was performed after instillation of lidocaine on the epiglottis and rima glotidis area to avoid laryngospasm. A cuffed endotracheal tube was systematically used. The animal was then placed under isoflurane (FORENE, Abbott, 2–3%). Heart rate, mean, diastolic and systolic arterial blood pressure, end tidal CO2, SpO2, and rectal temperature were monitored during surgery and in the postoperative period (Hewlett Packard M1165/66 A, 84 S model). The animal was placed on a left lateral recumbency. The area of the right hemi-thorax, sternum and neck was clipped and prepared for aseptic surgery (iodine polyvidone: Vétédine savon and Vétédine solution and alcohol, Vetoquinol, France). A right intercostal thoracotomy at the 7th intercostal space was performed. The animal was placed under respiratory assistance (positive pressure respiration) when the thorax was opened. An autostatic retractor was used to maintain the thoracotomy site open. The aorta was visualized on the upper surgical field after ventral retraction of the caudal pulmonary lobe. The TD was systematically identified (even if none of the pigs were fed with oil or fresh cream prior to surgery) on the lateral side of the aorta after incision of the mediastinum, strongly linked to the lymph nodes located on the cranio-dorsal part of the mediastinum. It was then carefully dissected over a 3-cm length. A silk ligature of the TD was performed cranial to the insertion site of the catheter. Two ligatures were preplaced 1–2 cm caudal to the insertion site and were used to manipulate the TD without attempts to grasp it with forceps. Microscissors were used to open the TD and complete opening was assessed by lymph extravasation. The catheter was then inserted in a retrograde manner for 2–3 cm. The two preplaced silk ligatures were then tied at the level of the internal beads to secure the catheter to the TD (Fig. 1). The catheter was then tunneled to the interscapular area and secured to the skin. A percutaneous thoracic drain (Pleurocath®, Plastimed, St-Leu-la-Forêt, France) was placed in the pleural space just before closure of the thoracotomy. It was secured to the skin. The surgical site was closed in a routine manner using 2 USP vicryl® to close the thoracotomy and 3-0 USP vicryl® for the superficial muscles.
View larger version (83K):
[in this window]
[in a new window]
|
Fig. 1. Intraoperative view (a) and schematic (b) of the surgical field. Thoracic duct (TD) is gently isolated. One silk ligature (S1) is tied cranial to the desired catheter (c) insertion and two others are pre placed caudally (S2 and S3). The catheter is inserted in a retrograde manner and secured to the TD with the two pre placed sutures.
|
|
Secondly, the jugular vein was approached by a cutaneous incision at the base of the neck. It was then individualized and a Bulldog hemostat was positioned cranial to the implantation site of the catheter. A silk ligature was tied to occlude the vessel cranially. Venotomy was done using microscissors. The catheter was introduced in the jugular vein and secured with a silk ligature. The catheter was then passed through the skin and plugged to the TD catheter with a polyurethane device. It was then secured to the skin.
2.4. Analgesic procedure
An analgesic procedure was set with morphine injection (0.5 mg/kg) performed just after induction of anesthesia and every 6 h if necessary. Pleural anesthesia was performed by injecting lidocaine (5 mg/kg) though the thoracic drain just before recovery and the animal was then placed on a right lateral recumbency. The pleural administration was repeated every six hours during 24 h.
2.5. Postoperative care
A body jacket including thorax and abdomen was used to protect the catheters. An open area in the jacket allowed daily collection of lymph and blood. Venous catheters were flushed with saline after each collection. No particular treatment was done on the lymphatic catheter. The thoracic drain was kept in place for 48 h.
|
3. Results
|
|---|
Outcome of the bypass is summarized in Table 1. The overall success rate of the procedure was 55%.
Apnea was recorded in every case after weaning off the ventilator and resolved in 8/9 pigs. One pig did not survive but was supported for more than 3 h before stopping manual ventilation and patency of the bypass was assessed (Table 1). Ventricular tachycardia was recorded in two pigs in the early stage of awakening at an average of 220 bpm and was successfully treated with IV propranolol injection (50 mg/kg).
|
4. Discussion
|
|---|
Jensen et al. [3] quoted a maximum duration of shunt patency of eight days, and clotting was recorded in 9/12 cases even with systemic use of heparin. Here, heparin was not used, lymphatico-venous shunt was available for up to 15 days and clotting was recorded in only 1/9 cases. None of the heparin-coated catheters clotted; their use seems mandatory for long-term management of lymphatic catheterization. Reasons include low-flow and high content of fibrinogen in lymphatic vessels.
Dissection of the TD should be very gentle. Leakage from the TD in the surrounding connective tissue makes catheterization and dissection time-consuming if not virtually impossible as experienced in one case in this study. Furthermore, any attempt to catheterize the thoracic duct far caudally [3] should be discouraged as the valves apparatus of the TD will impair progression of the catheter and forced maneuvers will increase the likelihood of damage and clotting in the TD. Beads on the catheter help securing sutures to the TD and are therefore recommended. Ventricular tachycardia, probably related to myocardial ischemia, occurred twice, was successfully treated and therefore, should not be considered as a major complication.
As previously proposed [4], mechanical ventilation was performed and led, after weaning, to apnea in all cases. Unlikely reasons include the type of sedative or fixed anesthetic agent used but more probably incorrect setting of the ventilator as assessed by low EtCO2 during surgery for 6/9 cases. Apnea appears to be a frequent and potentially life-threatening complication after mechanical ventilation in pigs.
|
Acknowledgements
|
|---|
The authors thank Jean-Pierre Gau for technical support and Alice Harvey for artwork.
|
References
|
|---|
- Almond GW. Research applications using pigs. Vet Clin North Am Food Anim Pract 1996; 12:707–716.[Medline]
- Hilweg DV, Seeliger K, Klapdor R. Thoracic duct of the mini pig. Topography and method of cannulation [article in German], Z Versuchstierkd 1973; 15:185–188.
- Jensen LT, Risteli J, Nielsen MD, Henriksen JH, Olesen HP, Risteli L, Lorenzen I. External thoracic duct-venous shunt in conscious pigs for long-term studies of connective tissue metabolites in lymph. Lab Anim Sci 1990; 40:620–624.[Medline]
- Moon PF, Smith LJ. General anesthetic techniques in swine. Vet Clin North Am Food Anim Pract 1996; 12:663–691.[Medline]
|
|
Top
Abstract
1. Introduction
