We thank Eugen Hofmann and Philine Zumstein for their excellent technical assistance and for sharing their expertise in stent application procedures. We thank Majlinda Kalanderi for the anatomical drawing.

Male Wistar rats with a mean weight of 592 g (&#177;50 SD) and mean age of 20 weeks were housed in animal facilities at a room temperature of 22-24 &#176;C and twelve hour light/dark cycle, with free access to tap water and a pellet diet. The animals received care from humans in accordance with institutional guidelines. The experiments were approved by the Committee for Animal Care of the Canton Bern, Switzerland (BE 102/13). We strictly followed the recommendations for Animal Research: Reporting of In Vivo Expe...

<ol>
	<li>Molyneux, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=International+Subarachnoid+Aneurysm+Trial+(ISAT)+of+neurosurgical+clipping+versus+endovascular+coiling+in+2143+patients+with+ruptured+intracranial+aneurysms:+a+randomised+trial.">International Subarachnoid Aneurysm Trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised trial.</a> Lancet. 360 (9342), 1267-1274 (2002).</li><li>Molyneux, A. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=International+subarachnoid+aneurysm+trial+(ISAT)+of+neurosurgical+clipping+versus+endovascular+coiling+in+2143+patients+with+ruptured+intracranial+aneurysms:+a+randomised+comparison+of+effects+on+survival,+dependency,+seizures,+rebleeding,+subgroups,+and+aneurysm+occlusion.">International subarachnoid aneurysm trial (ISAT) of neurosurgical clipping versus endovascular coiling in 2143 patients with ruptured intracranial aneurysms: a randomised comparison of effects on survival, dependency, seizures, rebleeding, subgroups, and aneurysm occlusion.</a> Lancet. 366 (9488), 809-817 (2005).</li><li>Marbacher, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraluminal+cell+transplantation+prevents+growth+and+rupture+in+a+model+of+rupture-prone+saccular+aneurysms.">Intraluminal cell transplantation prevents growth and rupture in a model of rupture-prone saccular aneurysms.</a> Stroke. 45 (12), 3684-3690 (2014).</li><li>Marbacher, S., Marjamaa, J., Abdelhameed, E., Hernesniemi, J., Niemela, M., Frosen, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Helsinki+rat+microsurgical+sidewall+aneurysm+model.">The Helsinki rat microsurgical sidewall aneurysm model.</a> J Vis Exp. (92), e51071 (2014).</li><li>Marbacher, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+mural+cells+leads+to+wall+degeneration,+aneurysm+growth,+and+eventual+rupture+in+a+rat+aneurysm+model.">Loss of mural cells leads to wall degeneration, aneurysm growth, and eventual rupture in a rat aneurysm model.</a> Stroke. 45 (1), 248-254 (2014).</li><li>Pritchett-Corning, K. R., Luo, Y., Mulder, G. B., White, W. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Principles+of+rodent+surgery+for+the+new+surgeon.">Principles of rodent surgery for the new surgeon.</a> J Vis Exp. (47), (2011).</li><li>Bernal, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Guidelines+for+rodent+survival+surgery.">Guidelines for rodent survival surgery.</a> J Invest Surg. 22 (6), 445-451 (2009).</li><li>Flege, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Development+and+characterization+of+a+coronary+polylactic+acid+stent+prototype+generated+by+selective+laser+melting.">Development and characterization of a coronary polylactic acid stent prototype generated by selective laser melting.</a> J Mater Sci Mater Med. 24 (1), 241-255 (2013).</li><li>Zartner, P., Cesnjevar, R., Singer, H., Weyand, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=First+successful+implantation+of+a+biodegradable+metal+stent+into+the+left+pulmonary+artery+of+a+preterm+baby.">First successful implantation of a biodegradable metal stent into the left pulmonary artery of a preterm baby.</a> Catheter Cardiovasc Interv. 66 (4), 590-594 (2005).</li><li>Hakamata, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Green+fluorescent+protein-transgenic+rat:+a+tool+for+organ+transplantation+research.">Green fluorescent protein-transgenic rat: a tool for organ transplantation research.</a> Biochem Biophys Res Commun. 286 (4), 779-785 (2001).</li><li>Bouzeghrane, F., Naggara, O., Kallmes, D. F., Berenstein, A., Raymond, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=International+Consortium+of+Neuroendovascular+C.+In+vivo+experimental+intracranial+aneurysm+models:+a+systematic+review.">International Consortium of Neuroendovascular C. In vivo experimental intracranial aneurysm models: a systematic review.</a> AJNR Am J Neuroradiol. 31 (3), 418-423 (2010).</li><li>Aquarius, R., Smits, D., Gounis, M. J., Leenders, W. P., De Vries, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flow+diverter+implantation+in+a+rat+model+of+sidewall+aneurysm:+a+feasibility+study.">Flow diverter implantation in a rat model of sidewall aneurysm: a feasibility study.</a> J Neurointerv Surg. , (2017).</li><li>Indolfi, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+rat+model+of+small+vessel+stenting.">A new rat model of small vessel stenting.</a> Basic Res Cardiol. 95 (3), 179-185 (2000).</li><li>Oyamada, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Trans-iliac+rat+aorta+stenting:+a+novel+high+throughput+preclinical+stent+model+for+restenosis+and+thrombosis.">Trans-iliac rat aorta stenting: a novel high throughput preclinical stent model for restenosis and thrombosis.</a> J Surg Res. 166 (1), e91-e95 (2011).</li><li>Kwon, J. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+bare+metal+stent+and+paclitaxel-eluting+stent+using+a+novel+rat+aorta+stent+model.">Comparison of bare metal stent and paclitaxel-eluting stent using a novel rat aorta stent model.</a> J Vet Sci. 12 (2), 143-149 (2011).</li><li>Rouer, M., Meilhac, O., Delbosc, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+murine+model+of+endovascular+aortic+aneurysm+repair.">A new murine model of endovascular aortic aneurysm repair.</a> J Vis Exp. (77), e50740 (2013).</li><li>Hardhammar, P. A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reduction+in+thrombotic+events+with+heparin-coated+Palmaz-Schatz+stents+in+normal+porcine+coronary+arteries.">Reduction in thrombotic events with heparin-coated Palmaz-Schatz stents in normal porcine coronary arteries.</a> Circulation. 93 (3), 423-430 (1996).</li><li>Guerrero, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antioxidant+effects+of+a+single+dose+of+acetylsalicylic+acid+and+salicylic+acid+in+rat+brain+slices+subjected+to+oxygen-glucose+deprivation+in+relation+with+its+antiplatelet+effect.">Antioxidant effects of a single dose of acetylsalicylic acid and salicylic acid in rat brain slices subjected to oxygen-glucose deprivation in relation with its antiplatelet effect.</a> Neurosci Lett. 358 (3), 153-156 (2004).</li><li>Niitsu, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Repeat+oral+dosing+of+prasugrel,+a+novel+P2Y12+receptor+inhibitor,+results+in+cumulative+and+potent+antiplatelet+and+antithrombotic+activity+in+several+animal+species.">Repeat oral dosing of prasugrel, a novel P2Y12 receptor inhibitor, results in cumulative and potent antiplatelet and antithrombotic activity in several animal species.</a> Eur J Pharmacol. 579 (1-3), 276-282 (2008).</li><li>Kastrati, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intracoronary+stenting+and+angiographic+results:+strut+thickness+effect+on+restenosis+outcome+(ISAR-STEREO)+trial.">Intracoronary stenting and angiographic results: strut thickness effect on restenosis outcome (ISAR-STEREO) trial.</a> Circulation. 103 (23), 2816-2821 (2001).</li><li>Lowe, H. C., James, B., Khachigian, L. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+model+of+in-stent+restenosis:+rat+aortic+stenting.">A novel model of in-stent restenosis: rat aortic stenting.</a> Heart. 91 (3), 393-395 (2005).</li><li>Finn, A. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+novel+rat+model+of+carotid+artery+stenting+for+the+understanding+of+restenosis+in+metabolic+diseases.">A novel rat model of carotid artery stenting for the understanding of restenosis in metabolic diseases.</a> J Vasc Res. 39 (5), 414-425 (2002).</li></ol>

Bioabsorbable stents and animal models 
In recent years the general trend in medicine has been away from permanent implants (which remain in the patient&#39;s body for the rest of their life) to bio-absorbable materials. Magnesium stents, in particular, are already quite established in cardiology8,9. Unfortunately these stents have not yet been tested for other applications, such as cerebrovascular diseases. For this reason we decided to stu...

Subarachnoid hemorrhage due to a ruptured intracranial aneurysm is associated with a high mortality rate and poor neurological outcome in many survivors. There are currently two general approaches to occlude IA: either microsurgical clipping (which requires operative exposure of the aneurysm), or endovascular occlusion. As the less invasive endovascular coil treatment of narrow-necked IA has been shown to be associated with slightly lower morbidity (especially in the posterior circulation1,2), endovascular treatment options have become the preferred modality of many neurosurgical centers. Numerous devices have been developed in order to extend the indications of endovascular treatment and overcome the main limitation of IA recurrence after coiling. Intracranial stents are especially promising to overcome these limitations, as they serve as a scaffold for neo-endothelization and coil herniation prevention, as well as protect the parent artery and improve intraluminal intraaneurysmal thrombosis caused by reduction of blood inflow. There is a need to study novel intracranial stents in a low cost animal model; at both macroscopic and molecular levels.
The aim of this study was to design a safe, fast, and standardized surgical technique for stent application in an already established saccular aneurysm model in rats3,4,5. In the present project, we evaluated the role of a biodegradable magnesium stent.

<table style="border-collapse:collapse;width:510pt" width="680">
	<colgroup>
		<col style="width:220pt" width="293" />
		<col style="width:115pt" width="153" />
		<col span="2" style="width:88pt" width="117" />
	</colgroup>
	<tbody>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="width:220pt;height:15.0pt" width="293">Medetomidine</td>
			<td class="xl17" style="width:115pt" width="153"></td>
			<td class="xl17" style="width:88pt" width="117"></td>
			<td class="xl17" style="width:88pt" width="117">any generic</td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Ketamin</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17">any generic</td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Buprenorphine</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17">any generic</td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Phosphate buffered saline</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Sodium dodecyl sulfate (0.1%)</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">3-0 resorbable suture</td>
			<td class="xl17">Ethicon Inc., USA</td>
			<td class="xl17">VCP428G</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">5-0 non absorbable suture</td>
			<td class="xl17">Ethicon Inc., USA</td>
			<td class="xl17">8618G</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">6-0 non-absorbable suture</td>
			<td class="xl17">B. Braun, Germany</td>
			<td class="xl17">C0766070</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">9-0 non-absorbable suture</td>
			<td class="xl17">B. Braun, Germany</td>
			<td class="xl17">G1111140</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">10-0 non-absorbable suture</td>
			<td class="xl17">Covidien, USA</td>
			<td class="xl17">N2530 Monosof</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Operation microscope</td>
			<td class="xl17">Zeiss, Germany</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Digital microscope camera</td>
			<td class="xl17">Sony, Japan</td>
			<td class="xl17">HXR-MC1P</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Standard surgical instruments</td>
			<td class="xl17"></td>
			<td class="xl17">multiple</td>
			<td class="xl17">see protocol 7.a</td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Microsurgical instruments</td>
			<td class="xl17"></td>
			<td class="xl17">multiple</td>
			<td class="xl17">see protocol 7.b</td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Vascular clip applicator</td>
			<td class="xl17">B. Braun, Germany</td>
			<td class="xl17">FT495T</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Temporary vascular clamps</td>
			<td class="xl17">B. Braun, Germany</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">19G Puncture needle&#160;</td>
			<td class="xl17">Angiomed GmbH, Germany</td>
			<td align="right" class="xl17">15820010</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Hydrophobic guide wire</td>
			<td class="xl17">Cook Medical, USA</td>
			<td class="xl17">G00650</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">4F sheat</td>
			<td class="xl17">Cordis Corporation, USA</td>
			<td class="xl17">504-604A</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Inflation syringe</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Laboratory shaker</td>
			<td class="xl17">Stuart</td>
			<td class="xl17">SRT6</td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Magnesium Stent 2.5/6 AMS with Polymer coating</td>
			<td class="xl17">Biotronik, Switzerland</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="21" style="height:15.75pt">
			<td class="xl18" height="21" style="width:220pt;height:15.75pt" width="293">Surgery drape&#160;</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Sterile cellulose swabs</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Syringes 1 ml and 2 ml</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Hollow needles 18G and 26G</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Isotonic sodium chloride</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Microtubes</td>
			<td class="xl17"></td>
			<td class="xl17"></td>
			<td class="xl17"></td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Eye ointment</td>
			<td class="xl17">Bausch + Lomb Inc, USA</td>
			<td class="xl17">Lacrinorm</td>
			<td class="xl17">any generic</td>
		</tr>
		<tr height="20" style="height:15.0pt">
			<td class="xl17" height="20" style="height:15.0pt">Small animal shaver</td>
			<td class="xl19"></td>
			<td class="xl19"></td>
			<td class="xl19"></td>
		</tr>
	</tbody>
</table>

biodegradable magnesium stent treatment of saccular aneurysms in a rat model - introduction of the surgical technique

The steady progess in the armamentarium of techniques available for endovascular treatment of intracranial aneurysms requires affordable and reproducable experimental animal models to test novel embolization materials such as stents and flow diverters. The aim of the present project was to design a safe, fast, and standardized surgical technique for stent assisted embolization of saccular aneurysms in a rat animal model.
Saccular aneurysms were created from an arterial graft from the descending aorta.The aneurysms were microsurgically transplanted through end-to-side anastomosis to the infrarenal abdominal aorta of a syngenic male Wistar rat weighing &#62;500 g. Following aneurysm anastomosis, aneurysm embolization was performed using balloon expandable magnesium stents (2.5 mm x 6 mm). The stent system was retrograde introduced from the lower abdominal aorta using a modified Seldinger technique.
Following a pilot series of 6 animals, a total of 67 rats were operated according to established standard operating procedures. Mean surgery time, mean anastomosis time, and mean suturing time of the artery puncture site were 167 &#177; 22 min, 26 &#177; 6 min and 11 &#177; 5 min, respectively. The mortality rate was 6% (n=4). The morbidity rate was 7.5% (n=5), and in-stent thrombosis was found in 4 cases (n=2 early, n=2 late in stent thrombosis).
The results demonstrate the feasibility of standardized stent occlusion of saccular sidewall aneurysms in rats - with low rates of morbidity and mortality. This stent embolization procedure combines the opportunity to study novel concepts of stent or flow diverter based devices as well as the molecular aspects of healing.

The average duration of surgery was 167 (&#177; 22) min, 26 (&#177; 6) min of which were needed for aneurysm creation and a further 23 (&#177; 7) min required for stent application and reconstruction of the arteriotomy (Figure 3).
Mortality, morbidity, and macroscopic in-stent thrombosis were the primary endpoints of the study. The regular follow-up periods were 7 days (n=28), and 21 days (n=32) res...

Watch this Scientific Journal Video about Biodegradable Magnesium Stent Treatment of Saccular Aneurysms in a Rat Model - Introduction of the Surgical Technique at JoVE.com

Biodegradable Magnesium Stent Treatment of Saccular Aneurysms in a Rat Model - Introduction of the Surgical Technique

Reproducable experimental animal models are needed for the testing of novel embolization materials, which have been designed to treat endovascular occlusion of intracranial aneurysms (IA). The present study aims to develop a safe and standardized surgical technique for stent assisted embolization of saccular aneurysms in a rat animal model.

The steady progess in the armamentarium of techniques available for endovascular treatment of intracranial aneurysms requires affordable and reproducable ...

The overall goal of this standardized method for occluding saccular sidewall aneurysms in rats using biodegradable magnesium stents is to study novel concepts in stent devices and the molecular aspects of aneurysm healing. This method can help answer key questions in the neurosurgical and neuroradiological field related to the function of new stent or flow diverter devices. The main advantage of this technique is that it represents a standardized and safe procedure with low morbidity and mortality rates.It is also highly reproducible and thus improves the reliability of associated studies. Under general anesthesia, open the abdomen of the donor rat below the xiphoid process. First incise along the midventral line and separate the skin from the musculature.Then dissect the abdominal musculature and identify the diaphragm above the liver at the insertion point of the thoracic cavity. Next access the thoracic cavity and euthanize the rat with an intracardiac ketamine injection. Then mobilize the left lung and fix it to the right side using a cellulose swab.Next expose the aortic arc and above the aorta, clamp the azygos and left cranial caval veins using two mosquito clamps. Then cut between the clamps and leave the clamps attached. Now increase the access to the aortic arc and descending aorta using micro scissors and micro forceps.Along the aorta, identify the left subclavian artery and first intercostal artery. Now place a nonabsorbable 6-0 suture just cranial of the first intercostal artery and tie it up. At the proximal end, cut the aorta right after the origin of the left subclavian artery.Finally remove the newly created aneurysm with a cut just below the ligature. After measuring the aneurysm, immediately transplant the graft into the recipient rat. Start the surgery on the recipient rat with a mid ventral incision distal of the xiphoid process and open the abdominal muscles along the linea alba.Then move aside the small intestines, the cecum, and the colon and attach a self-holding retractor to keep the abdominal cavity open. Place a swab beneath the liver to improve the retroperitoneal exposure. Fat masses can be moved aside as well.Now open the parietal peritoneum to expose the abdominal aorta. First bluntly dissect the surrounding retroperitoneal fat to expose a longer length of the vessel. Be careful when handling the ureters, testicular vessels, and the superior mesenteric artery.They are often covered by a thin layer of adipose tissue. When proceeding to a sharp dissection, only grasp the adventitia to avoid damaging the vessel wall. Once exposed, dissect the abdominal aorta.Start at the distal segment which is the most technically challenging segment to dissect. Use micro scissors and micro forceps starting at the vena cava alongside the arterial adventitial layer between the vessels. Small lumbar arteries may arise as segmental vessels from the dorsal surface of the aorta.Coagulate and cut these as needed. Also try to identify the right iliolumbar artery. Its origin is most frequently caudal to the left counterpart but this varies.Once the dissection is finished, without stretching the vessel, place a small, colored rubber pad underneath it to indicate where the arterial puncture will be performed. Now proceed with the dissection of the abdominal aorta from the vena cava in the middle segment. Identify the superior mesenteric artery at its origin from the abdominal aorta and keep it intact.Also do not damage the lumbosacral plexus. Use lots of flushing and be mindful of the short coagulation time. Ultimately establish the location of the stent in the middle segment and be sure to leave enough room for the abdominal vessels around the stent.Now place a small piece of gauze and a colored rubber pad under the aorta for better exposure. Then dissect the proximal segment of the abdominal aorta located proximal to the renal vein. After opening the parietal peritoneum, separate the vessels with two blunt forceps.Then after a dorsal circumnavigation of the aorta, place a small piece of a colored rubber beneath it to facilitate the future application of a proximal clip. Clamp the aorta in the middle segment. First apply the distal clamp then the proximal clamp.Next remove the adventitia at the planned anastomosis site using micro forceps and micro scissors. Do not injure the vessel wall. Next lift a small piece of vessel wall using micro forceps and perform a linear incision with micro scissors to make a hole with the same size as the aneurysm base.Then flush the artery with saline in both directions using a blunted needle. Now place the first two stitches of the end-to-side anastomosis at the proximal and distal end of the arteriotomy. Grasp the vessel as little as possible while placing the sutures.Then close the incision with interrupted sutures to complete the anastomosis. To proceed, remove the distal clamp first. Place an extra suture in case of major bleeding from backflow.Then remove both clamps and rinse the anastomosis site. Check the patency of the distal abdominal aorta using a direct milking test. Then remove the gauze swab under the colored rubber pad and wait 10 minutes before proceeding with the stent implantation.To start the stent implantation, first clip the artery puncture site in the distal segment at the distal clamp and then the proximal clamp. Then remove the loose connective tissue and some of the adventitia at the puncture site. Next place a large temporary clamp in the proximal segment to avoid major hemorrhaging during the arterial puncture.Now lift the vessel wall and puncture the distal arterial segment using an 18-gauge puncture needle and thoroughly flush the artery with saline. Next insert a hydrophobic guidewire into the puncture site and remove the proximal clamp from the distal segment. Advance the guidewire to the clamp in the proximal segment.Then insert the Teflon introducer using the Seldinger technique. Advance the dilater to be proximal to the anastomosis site. Then check that the three-way stopcock is turned off to avoid unnecessary loss of blood.Next remove the guidewire and dilater. After vacuuming the balloon system, set the system to one bar of pressure, and then insert the observable magnesium stent using the size four Fogarty introducer. When the stent is finally in place, carefully inflate the balloon to eight or nine bar while continuously checking the anastomosis sutures for ripping.Then deflate and remove the balloon. While removing the introducer, be ready with a temporary clip as retrograde oozing from the proximal patent arteries may be significant. Now place a clip in the proximal distal segment and remove the temporary clamp in the proximal segment.Next thoroughly flush the puncture site with saline and close it with interrupted, nonabsorbable 10-0 sutures. If possible avoid grasping the vessel wall. Check for distal artery patency with the direct milking test.Remove the colored rubber pad. Finish by closing the surgical site as described in the tech's protocol. The average duration of surgery was about three hours of which about 1/2 hour was needed for aneurysm creation and another half hour was needed for stent application and reconstruction of the arteriotomy.There were no deaths during surgery. In 87%of surgeries, the desired endpoint of a patent artery was achieved. The other animals included five that experienced complications and four that died within three days due to early in stent thrombosis.In two animals, late in stent thrombosis occurred 21 days postoperatively with no accompanying neurological deficits. One animal suffered wound dehiscence on the second postoperative day with a consecutive loss of volume. We first had the idea for this method when we recognized that biodegradable stent devices gained increasing popularity in the treatment of coronary heart disease and realized that today's techniques of stent insertion are associated with high rates of morbidity and mortality.Once mastered, this technique can be performed in an average time of two hours and 15 minutes if it is performed properly. Following this procedure, other methods like intra aneurysm coil embolization can be performed in order to answer additional questions about aneurysm healing.

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Research

JoVE Journal

Neuroscience

11.0K vistas.  Kantonsspital Aarau. The overall goal of this standardized method for occluding saccular sidewall aneurysms in rats using biodegradable magnesium stents is to study novel concepts in stent devices and the molecular aspects of aneurysm healing. This method can help answer key questions in the neurosurgical and neuroradiological field related to the function of new stent or flow diverter devices. The main advantage of this technique is that it represents a standardized and safe procedure with low morbidity and mort...