This work was supported by grants from the Instituto de Salud Carlos III [PFIS2017-0224], &#34;Beca Ruza&#34; from the Sociedad Espa&#241;ola de Cuidados Intensivos Pedi&#225;tricos and the Vanderbilt Medical Scholars Program.
The sponsors were not involved in the collection, analysis, or interpretation of the data.
We would like to thank Isabel Salas for the help provided within the animal laboratory and the Mr. Carles F&#225;brega and Ms. Gemma Fernandez-Asensio from the Audio-Visual Techincal Team from Sant Joan de D&#233;u Hospital for their technical support with the video recording and production.

The intubation procedure outlined below was approved by the Barcelona University Institutional Animal Care and Use Committee (CEEA 180/19)
1. Experimental preparation
<ol>
	<li>Obtain the following materials: 2 mm diameter polyvinyl chloride (PVC) endotracheal tube, 6 French (Fr) polyurethane feeding tube, flat and wide tip dissection forceps and sterile lubricant (Figure 1).</li>
	<li>During the intubation and surgery processes, maintain sterile conditions.</li>
</ol>
2. Anesthesia
<ol>
	<li>Anesthetize the animal with 5 mg/kg xylazine and 25 mg/kg ketamine applied together intramuscularly in the vastus lateralis of the femoral quadriceps. Alpha-2 agonists such as dexmedetomidine can also be used instead of xylazine.</li>
	<li>Allow 3-5 minutes for the medication to reach effect.</li>
	<li>Readminister the same dose until deep anesthesia is achieved (negative pedal, palpebral and corneal reflexes). Ideally, the rabbit will maintain spontaneous breathing until intubation.</li>
</ol>
3. Endotracheal intubation
<ol>
	<li>Place the rabbit on a thermal blanket at 37 &#176;C. Place the animal in dorsal recumbency with the head in hyperextension. Align the head as straight and midline as possible. A four-centimeter roll made of sterile gauze placed in the dorsal region of the neck may be helpful to achieve at least 45&#176; of extension (Figure 2).</li>
	<li>Use flat and wide tip dissection forceps to open the oral cavity approximately one centimeter wide. Use forceps with a blunt and wide end to avoid mouth trauma.</li>
	<li>Measure the distance between mouth and the region of stomach (first rib). Introduce a lubricated 6 French (Fr) polyurethane gastric tube to the pre-measured mark (Figure 3-4).</li>
	<li>Move the feeding tube to the left and fix with adhesive tape to the surgical field.</li>
	<li>Introduce the 2 mm diameter PVC endotracheal tube, covered with sterile lubricant to the 3 cm mark.
	<ol>
		<li>If there are any difficulties in advancing the tube, move it completely and reattempt until a smooth glide is achieved. The risk of trauma to the larynx and epiglottis is significant with multiple intubation attempts. Fix the tube with adhesive tape to the surgical field (Figure 5-6).</li>
	</ol>
	</li>
	<li>Connect the endotracheal tube to the ventilator with following settings: Tidal volume - 10 mL/kg; respiratory rate: 40 breaths/min; FiO2 100%, PEEP 6.</li>
	<li>Confirm the correct position of the tube by the detection of CO2 in exhaled air (ETCO2), direct visualization of thoracic expansion and fogging of the tube. Monitoring of the animal by pulse oximetry and lung auscultation can also be helpful (Figure 7).</li>
	<li>At the conclusion of the experiment, use a standardized euthanasia protocol that consists of intravenous administration of pentobarbital 120-240 mg/kg. Repeat doses until breath cessation, reflex absence and asystole are acheived. 
	NOTE: In the surgical experiments, the animal is alive during the ventilation process and finally is euthanized.</li>
</ol>

<ol>
	<li>Gilroy, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endotracheal+intubation+of+rabbits+and+rodents.">Endotracheal intubation of rabbits and rodents.</a> Journal of the American Veterinary Medical Association. 179 (11), 1295 (1981).</li><li>Graham, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Common+procedures+in+rabbits.">Common procedures in rabbits.</a> The Veterinary Clinics of North America. Exotic Animal Practice. 9 (2), 367-388 (2006).</li><li>Fick, T. E., Schalm, S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+simple+technique+for+endotracheal+intubation+in+rabbits.">A simple technique for endotracheal intubation in rabbits.</a> Laboratory Animals. 21 (3), 265-266 (1987).</li><li>Conlon, K. 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=Atraumatic+endotracheal+intubation+in+small+rabbits.">Atraumatic endotracheal intubation in small rabbits.</a> Laboratory Animal Science. 40 (2), 221-222 (1990).</li><li>Johnson, D. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Endoscopic+intubation+of+exotic+companion+mammals.">Endoscopic intubation of exotic companion mammals.</a> The Veterinary Clinics of North America. Exotic Animal Practice. 13 (2), 273-289 (2010).</li><li>Falc&#227;o, S. 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=Technique+of+blind+tracheal+intubation+in+rabbits+(Oryctolagus+cuniculi)+supported+by+previous+maneuver+of+esophageal+cannulization.">Technique of blind tracheal intubation in rabbits (Oryctolagus cuniculi) supported by previous maneuver of esophageal cannulization.</a> Acta Cirurgica Brasileira. 26 (5), 352-356 (2011).</li><li>Miura, H., 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=Endotracheal+intubation+in+rabbits.">Endotracheal intubation in rabbits.</a> The Japanese Journal of Veterinary Anesthesiology. 19 (1), 25-29 (2012).</li><li>Thompson, K. L., 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=Endotracheal+Intubation+of+Rabbits+Using+a+Polypropylene+Guide+Catheter.">Endotracheal Intubation of Rabbits Using a Polypropylene Guide Catheter.</a> Journal of Visualized Experiments. (129), (2017).</li><li>Comolli, 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=Comparison+of+endoscopic+endotracheal+intubation+and+the+v-gel+supraglottic+airway+device+for+spontaneously+ventilating+New+Zealand+white+rabbits+undergoing+ovariohysterectomy.">Comparison of endoscopic endotracheal intubation and the v-gel supraglottic airway device for spontaneously ventilating New Zealand white rabbits undergoing ovariohysterectomy.</a> Veterinary Record. , 1-8 (2020).</li><li>Hua, 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=Effects+of+different+ventilation+strategies+on+lung+injury+in+newborn+rabbits.">Effects of different ventilation strategies on lung injury in newborn rabbits.</a> Pediatric Pulmonology. 47 (11), 1103-1112 (2012).</li><li>Kitchen, M. 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=The+role+of+lung+inflation+and+sodium+transport+in+airway+liquid+clearance+during+lung+aeration+in+newborn+rabbits.">The role of lung inflation and sodium transport in airway liquid clearance during lung aeration in newborn rabbits.</a> Pediatric Research. 73 (4-1), 443-449 (2012).</li><li>Boon, M. 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=Tubeless+tracheotomy+for+survival+airway+surgery+in+the+leporine+model.">Tubeless tracheotomy for survival airway surgery in the leporine model.</a> The Laryngoscope. 125 (3), 680-684 (2015).</li><li>Dion, G. R., 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=Morbidity+and+mortality+associated+with+preclinical+tracheostomy+models.">Morbidity and mortality associated with preclinical tracheostomy models.</a> The Laryngoscope. 128 (2), 68-71 (2018).</li><li>Phaneuf, L. R., 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=Tracheal+injury+after+endotracheal+intubation+and+anesthesia+in+rabbits.">Tracheal injury after endotracheal intubation and anesthesia in rabbits.</a> Journal of the American Association for Laboratory Animal Science. 45 (6), 67-72 (2006).</li></ol>

The authors have nothing to disclose.

Rabbits are widely used in animal experimentation due to their availability, high reproduction rate with short intergenerational times, and easy handling2. In our center, we use 5-7-day old New Zealand rabbits (Oryctolagus cuniculus) as a neonatal model to study the neurologic repercussions of extracorporeal surgery on the developing brain. As a result, we utilize procedures that require deep anesthesia and must use endotracheal intubation for periods of time up to an hour.
In the adult rabbit, several airway management techniques have been described, usually in a surgical context. When we tried to extrapolate these techniques to the rabbit kits, several problems arose. The rabbits weigh between 110 and 210 grams and have a maximum mouth opening range of 1 cm. These characteristics make direct visualization of the larynx difficult and it is complicated to find endoscopic material small enough. Another option described in the literature is to place an otoscope in the oral cavity and use it as a guide to introduce the PVC tube7. In newborn rabbits, both the presence of the tongue and the small size of the mouth make direct visualization of the glottis difficult. In addition, there are no supraglottic devices of adequate dimensions for newborns.
Due to the circumstances mentioned above, there are two fundamental mechanisms to secure the airway of the very small rabbit: tracheostomy and blind intubation. Tracheostomy is an invasive approach that has been used in both adult and newborn rabbits10, 12. It has the advantage of direct tracheal visualization, allowing the proceduralist to identify the exact location of the endotracheal tube. However, there is a high risk of mechanical complications and infection of the incision area, in addition to a decreased rate of survival of the animals once the procedures are completed13. Endoscopic/fiberoptic intubation is a method that would allow for direct visualization without surgery5. Another option to prevent laryngeal trauma is the use of a tight-fitting face mask, which has some additional drawbacks such as suboptimal ventilation and gastric distension.
In the laboratory, blind intubation is used to manage newborn rabbit airways. This method has been described in the adult rabbit as a feasible technique with high success index6. In the initial experiments, we tried to perform this technique without occlusion of the digestive tract. The result was a high rate of introduction of the endotracheal tube into the esophagus. With the insertion of the gastric tube prior to intubation, however, successful intubation was achieved in 90% of cases. Regarding the size of the endotracheal tube, we initially tried to use peripheral venous catheters up to 14 gauge in diameter, observing difficulties in both insertion (greater rigidity) and ventilation (diameter too small and difficulty connecting to the ventilator). In our experience, the use of 2 mm internal diameter endotracheal tubes introduced to a depth no more than 3 cm has been the most effective in ventilating small rabbits, shown by correct gasometric and ETCO2 values. While intubation in adult rabbits generally requires hyperextension of the head to essentially a 90&#176; angle to the horizontal surface of the table, we were able to perform the procedure with only a mild head extension.
One of the important elements to be considered when performing this procedure is the friable nature of the newborn rabbit trachea. Keeping this is mind, we introduce the pre-lubricated tube slowly and carefully to avoid tracheal perforation. We recommend not inserting the tube further than 3 cm, as this was found to be the optimal length during practice attempts, and halting the intubation if the proceduralist encounters any resistance; in this situation, it is preferable to remove the tube and start over. We experienced one case of likely tracheal perforation in the smallest animal in the cohort.
The main limitation of this technique is the difficulty in detecting the correct position of the endotracheal tube once introduced. In our experience, the advancement of the device without resistance, the detection of appropriate ETCO2, the fogging of the tube and visualization of thoracic expansion during ventilation, as well as the maintenance of vital signs have been sufficient to corroborate the suitability of the procedure in all cases. In some of the experimental subjects, arterial gasometries were performed during ventilation showing adequate levels of carbon dioxide and oxygen concentration. In addition, though histopathology analysis was not performed, previously published literature has described mucosal injury to the trachea in the absence of clinical changes secondary to intubation14.
In conclusion, the model of intubation in newborn rabbits we have described is a rapid technique that uses basic supplies and allows for effective ventilation. We believe this technique can be incorporated in the armamentarium of airway management of neonatal rabbits.

The peculiar anatomy of the rabbit&#39;s respiratory system makes endotracheal intubation complicated. The oral cavity is deep and narrow with a limited range of mouth opening and a relatively large tongue, making direct visualization of the larynx difficult even with the use of a laryngoscope1,2. Furthermore, intubation of the newborn rabbit, which is 10-20 times smaller than the adult, is even more of a challenging procedure. In addition to these anatomical characteristics, rabbits are prone to laryngospasm secondary to manipulation of the airway.
Several intubation techniques have been described in the literature, such as laryngoscope tracheal intubation, blind intubation, otoscope intubation, retrograde intubation, endoscope intubation, tracheostomy and supraglottic device ventilation3,4,5,6,7,8,9. All these techniques have been carried out successfully in adult rabbits; however, there are few publications regarding advanced airway management in the newborn rabbit10. One study describes performing tracheostomies in animals of this age to assess breathing mechanics and lung volumes, though this is an aggressive and irreversible technique11. This method for endotracheal intubation has proven to be an effective and low-cost method of airway management in newborn rabbits.

<table><tbody><tr><td>2 mm diameter Polyvinyl Chloride (PVC) endotracheal tube</td><td>Vygon</td><td>520.20</td><td></td></tr><tr><td>6 French polyurethane feeding tube</td><td>Vygon</td><td>310.06</td><td></td></tr><tr><td>Anesthesia (Ketamine and Xylazine)</td><td></td><td></td><td></td></tr><tr><td>Multiparameter monitor Intellivue MP5</td><td>Phillips</td><td></td><td></td></tr><tr><td>Plain and wide tip dissection forceps</td><td>LensforVision</td><td>AK005</td><td></td></tr><tr><td>Sterile lubricant (Silkospray)</td><td>Rush</td><td></td><td></td></tr><tr><td>Ventilator Servo 900c</td><td>Maquet</td><td></td><td></td></tr></tbody></table>

blind endotracheal intubation in neonatal rabbits

The newborn rabbit is a useful animal model for various pathologies and procedures. Airway management of the rabbit is complex due to its anatomical characteristics, which is further complicated in the case of the newborn. Of the different methods of advanced airway management, endotracheal intubation is less aggressive than tracheostomy, and is more feasible than supraglottic management given the lack of supraglottic devices of such a small size. As direct glottis visualization is very difficult in animals this size, this blind intubation model is presented as an effective alternative, especially for experiments requiring prolonged anesthesia. Using this method, we performed blind intubations with a 90% success rate.

In the laboratory, this technique is carried out by medical personnel with experience in experimentation with New Zealand rabbits and expertise in pediatric airway management. The procedure has been performed by one investigator in 10 animals with a global success rate of 90%. Previously, another researcher had practiced optimizing both the position of the animal and the correct tube fixation length. None of the animals were intubated in esophagus. Only one attempt (10%) failed due to the extremely small size of the animal (Table 1). Once blind intubation has been practiced, success is achieved on the first attempt in most cases, even if the procedure is performed by personnel not previously trained in rabbit airway management. We achieved a 100% intubation success rate in one or two attempts in animals weighing equal to or greater than 120 g.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/61874/61874fig01.jpg" /> 
Figure 1: Materials needed for the experiment: Dissection forceps, feeding tube, endotracheal tube, sterile lubricant. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/61874/61874fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/61874/61874fig02.jpg" /> 
Figure 2: Position of the animal before intubation: Dorsal recumbency and mild hyperextension. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/61874/61874fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/61874/61874fig03.jpg" /> 
Figure 3: Mouth opening with dissection forceps. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/61874/61874fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/61874/61874fig04.jpg" /> 
Figure 4: The feeding tube is introduced into the stomach. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/61874/61874fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/61874/61874fig05.jpg" /> 
Figure 5-6: The endotracheal tube is introduced 3 cm blindly and fixed, along with the feeding tube, to the surgical field. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/61874/61874fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/61874/61874fig06.jpg" /> 
Figure 6: The fixed endotracheal tube and feeding tube. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/61874/61874fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/61874/61874fig07.jpg" /> 
Figure 7: The animal is connected to the ventilator. <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/61874/61874fig07large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>ANIMAL NUMBER</td>
			<td>WEIGHT (g)</td>
			<td>SUCCESS</td>
			<td>ATTEMPTS</td>
			<td>DEATH</td>
		</tr>
		<tr>
			<td>1</td>
			<td>150</td>
			<td>+</td>
			<td>1</td>
			<td>-</td>
		</tr>
		<tr>
			<td>2</td>
			<td>125</td>
			<td>+</td>
			<td>2</td>
			<td>-</td>
		</tr>
		<tr>
			<td>3</td>
			<td>180</td>
			<td>+</td>
			<td>1</td>
			<td>-</td>
		</tr>
		<tr>
			<td>4</td>
			<td>210</td>
			<td>+</td>
			<td>1</td>
			<td>-</td>
		</tr>
		<tr>
			<td>5</td>
			<td>120</td>
			<td>+</td>
			<td>2</td>
			<td>-</td>
		</tr>
		<tr>
			<td>6</td>
			<td>140</td>
			<td>+</td>
			<td>2</td>
			<td>-</td>
		</tr>
		<tr>
			<td>7</td>
			<td>200</td>
			<td>+</td>
			<td>1</td>
			<td>-</td>
		</tr>
		<tr>
			<td>8</td>
			<td>190</td>
			<td>+</td>
			<td>1</td>
			<td>-</td>
		</tr>
		<tr>
			<td>9</td>
			<td>180</td>
			<td>+</td>
			<td>1</td>
			<td>-</td>
		</tr>
		<tr>
			<td>10</td>
			<td>110</td>
			<td>-</td>
			<td>3</td>
			<td>+</td>
		</tr>
		<tr>
			<td>TOTAL</td>
			<td>160.5</td>
			<td>90%</td>
			<td>1.5</td>
			<td>10%</td>
		</tr>
	</tbody>
</table>
Table 1: Animal sample features and endotracheal intubation attempts.

Watch this Scientific Journal Video about Blind Endotracheal Intubation in Neonatal Rabbits at JoVE.com

Blind Endotracheal Intubation in Neonatal Rabbits

We describe a technique of endotracheal intubation in newborn rabbits after esophageal catheterization with a gastric tube.

The newborn rabbit is a useful animal model for various pathologies and procedures. Airway management of the rabbit is complex due to its anatomical ...

blind-endotracheal-intubation-in-neonatal-rabbits

Universidad San Sebastian

Research

JoVE Journal

Medicine

5.3K Views.  Hospital Sant Joan de Déu, Institut de Recerca Sant Joan de Déu. We describe a technique of endotracheal intubation in newborn rabbits after esophageal catheterization with a gastric tube.

Video: Blind Endotracheal Intubation in Neonatal Rabbits

Guidelines for Elective Pediatric Fiberoptic Intubation

Fiberoptic intubation in pediatric patients is often required especially in difficult airways of syndromic patients i.e. Pierre Robin Syndrome. Small babies will desaturate very quickly if ventilation is interrupted mainly to high metabolic rate. We describe guidelines to perform a safe fiberoptic intubation while maintaining spontaneous breathing throughout the procedure. Steps requiring the use of propofol pump, fentanyl, glycopyrrolate, red rubber catheter, metal insuflation hook, afrin, lubricant and lidocaine spray are shown.

We describe guidelines to perform a safe and efficient elective fiberoptic intubation in pediatric patients while maintaining spontaneous ventilation.

Fiberoptic intubation in pediatric patients is often required especially in difficult airways of syndromic patients i.e. Pierre Robin Syndrome. Small ...

Endotracheal Intubation in Mice via Direct Laryngoscopy Using an Otoscope

Mice, both wildtype and transgenic, are the principal mammalian model in biomedical research currently. Intubation and mechanical ventilation are necessary for whole animal experiments that require surgery under deep anesthesia or measurements of lung function. Tracheostomy has been the standard for intubating the airway in these mice to allow mechanical ventilation. Orotracheal intubation has been reported but has not been successfully used in many studies because of the substantial technical difficulty or a requirement for highly specialized and expensive equipment. Here we report a technique of direct laryngoscopy using an otoscope fitted with a 2.0 mm speculum and using a 20 G&#160;intravenous catheter as an endotracheal tube. We have used this technique extensively and reliably to intubate and conduct accurate assessments of lung function in mice. This technique has proven safe, with essentially no animal loss in experienced hands. Moreover, this technique can be used for repeated studies of mice in chronic models.

Endotracheal Intubation in Mice via Direct Laryngoscopy Using an Otoscope

We have developed a simple, reliable, and relatively inexpensive method for endotracheal intubation in mice via direct laryngoscopy using an otoscope with a 2.0 mm speculum. This technique is atraumatic and can be used for repeated measurements in chronic experiments. We find it superior to tracheostomy or previously reported nonsurgical techniques.

Mice, both wildtype and transgenic, are the principal mammalian model in biomedical research currently. Intubation and mechanical ventilation are ...

Arterial Pouch Microsurgical Bifurcation Aneurysm Model in the Rabbit

Endovascular treatment for intracranial aneurysms gained importance over the past decades, consequently there is an increased need of testing endovascular devices. Animal models respecting rheological, hemodynamic and aneurysm wall conditions are highly warranted. Therefore, the aim of the present study was to design a novel standardized and reproducible surgical technique to create autologous arterial pouch bifurcation aneurysms with non-modified and modified wall conditions in rabbits.
Bifurcation aneurysms were created by end-to-side anastomosis of the right on the left common carotid artery, both serving as parent arteries for the arterial pouch, which was microsurgically sewn on. Grafts were taken from the proximal right common carotid artery, either for the control (n = 7, immediate autologous re-implantation) or modified (n = 7, incubated with 100 international units elastase for 20 minutes before autologous re-implantation) group. Pouch and parent artery patency were controlled by fluorescence angiography immediately after creation. At follow-up (28 days), all rabbits underwent contrast enhanced magnetic resonance angiography and fluorescence angiography followed by aneurysm harvesting, macroscopic and histological evaluation.
A total of 16 female New Zealand White rabbits were operated upon. Two animals died prematurely. At follow-up, 85.72% of all aneurysms remained patent. Both groups revealed an increase in aneurysm size over time; this was more pronounced in the control group (6.48 &#177; 1.81 mm3 at time of creation vs. 19.85 &#177; 6.40 mm3 at follow-up, p = 0.037) than in the modified group (8.03 &#177; 1.08 mm3 at time of creation vs. 20.29 &#177; 6.16 mm3 at follow-up, p = 0.054).
Our findings demonstrate the adequacy of this new rabbit model which allows for the creation of bifurcation aneurysms with different wall conditions in a microsurgical approach. Given the excellent long-term patency and the property of aneurysm growth over time, this model may serve as an important tool for preclinical evaluation of novel endovascular therapies.

Developing and testing endovascular devices for intracranial aneurysm treatment is still of great importance. Most aneurysm models used today miss either the important characteristics of an arterial degenerated wall or the hemodynamics of a true bifurcation. Therefore, we aimed to design a novel arterial pouch bifurcation model in rabbits.

Endovascular treatment for intracranial aneurysms gained importance over the past decades, consequently there is an increased need of testing endovascular ...

Neuroscience

Simplifying Transcutaneous Intratracheal Drug Delivery in the Newborn Preterm Rabbit

Intratracheal (IT) drug delivery allows the direct delivery of pharmaceutical substances to the lung, maximizing potential pulmonary benefit and minimizing systemic drug exposure. The transcutaneous technique is simple and allows for the IT delivery of substances to the lung of prematurely born rabbits shortly after birth. Newborn pups are anesthetized with inhaled Isoflurane before being placed in a supine position with the neck extended. The larynx is identified and stabilized before transcutaneous placement of a 26-gauge (G) catheter into the trachea. Following catheterization of the trachea, a 30 G blunt needle attached to a Hamilton syringe is introduced into the IT catheter and is used for delivering a precise volume into the trachea during spontaneous respiration. After the IT injection is completed, the needle and catheter are withdrawn, and the pup is allowed to recover from anesthesia. Transcutaneous IT injection delivers a large proportion of the injected substance to the lung, with the majority remaining in the lung 3 hours after the intervention. The injections are well tolerated from the day of birth and can be repeated for multiple consecutive days without influencing survival. This technique can be used to investigate the effect of pharmaceutical agents on lung development and in the prevention of neonatal lung injury in preterm rabbits.

Transcutaneous intratracheal injection allows for effective intrapulmonary drug delivery during spontaneous respiration. Single and multiple injections are well tolerated with no effect on survival. The technique is simple to perform and can examine the effect of substances on lung development and the prevention of lung injury in newborn rabbits.

Intratracheal (IT) drug delivery allows the direct delivery of pharmaceutical substances to the lung, maximizing potential pulmonary benefit and ...

Isolated Lung Perfusion System in the Rabbit Model

The isolated lung perfusion system has been widely used in pulmonary research, contributing to elucidate the lungs&#39; inner workings, both micro and macroscopically. This technique is useful in the characterization of pulmonary physiology and pathology by measuring metabolic activities and respiratory functions, including interactions between circulatory substances and the effects of inhaled or perfused substances, as in drug testing. While in vitro methods involve the slicing and culturing of tissues, the isolated ex vivo lung perfusion system allows to work with a complete functional organ making possible the study of a continuous physiological function while recreating ventilation and perfusion. However, it should be noted that the effects of the absence of central innervation and lymphatic drainage still have to be fully assessed. This protocol aims to describe the assembly of the isolated lung apparatus, followed by the surgical extraction and cannulation of lungs and heart from experimental lab animals, as well as to display the perfusion technique and signal processing of data. The average viability of the isolated lung ranges between 5-8 h; during this period, the pulmonary capillary permeability increases, causing edema and lung injury. The functionality of preserved pulmonary tissue is measured by the capillary filtration coefficient (Kfc), used to determine the extent of pulmonary edema through time.

The isolated rabbit lung preparation is a gold standard tool in pulmonary research. This publication aims to describe the technique as developed for the study of physiological and pathological mechanisms involved in airway reactivity, lung preservation, and preclinical research in lung transplantation and pulmonary edema.

The isolated lung perfusion system has been widely used in pulmonary research, contributing to elucidate the lungs&#39; inner workings, both micro and ...

Endotracheal Intubation of Rabbits Using a Polypropylene Guide Catheter

Endotracheal intubation in rabbits can be challenging due to their unusual anatomy. Achieving a patent airway during anesthesia is critical for the avoidance of airway obstruction, prevention of gastric tympany, and to allow ventilatory support. Due to the difficulty of intubation, alternative methods such as the use of laryngeal mask airways or laryngeal tubes have been explored. However, these methods do not result in direct access to the trachea and thus may present a risk for development of complications. In addition, lack of direct intubation of the trachea can result in personnel exposure to waste anesthetic gases. Numerous methods for endotracheal intubation have been described, including blind placement, use of a fiberoptic laryngoscope or endoscope, and cricoid placement. Despite these numerous publications, many still struggle to achieve success. Here we provide a detailed description of an intubation technique that can be taught with minimal training with a short time to proficiency. Briefly, after administration of injectable anesthesia and proper positioning of the rabbit, a polypropylene catheter is placed into the trachea by direct visualization using a laryngoscope. The catheter is then used as a guide to direct the endotracheal tube into the trachea. This method allows for intubation without the need for expensive equipment and can be performed by a single individual without the need for an assistant. In conclusion, this technique can be easily taught and performed at very little cost in any clinical or research setting.

Endotracheal intubation in rabbits is challenging due to their unusual anatomy. Here we present a technique for direct intubation of the trachea using a polypropylene catheter as a guide. This method utilizes relatively inexpensive supplies, requires minimal training, and can be easily performed in any clinical setting.

Endotracheal intubation in rabbits can be challenging due to their unusual anatomy. Achieving a patent airway during anesthesia is critical for the ...

Biology

Model of Ischemia and Reperfusion Injury in Rabbits

The protocol here provides a simple, highly replicable methodology to induce in situ acute regional myocardial ischemia in the rabbit for non-survival and survival experiments. New Zealand White adult rabbit is sedated with atropine, acepromazine, butorphanol, and isoflurane. The animal is intubated and placed on mechanical ventilation. An intravenous catheter is inserted into the marginal ear vein for the infusion of medications. The animal is pre-medicated with heparin, lidocaine, and lactated Ringer&#39;s solution. A carotid cut-down is performed to obtain arterial line access for blood pressure monitoring. Select physiologic and mechanical parameters are monitored and recorded by continuous real-time analysis.
With the animal sedated and fully anesthetized, either a fourth intercostal space small left thoracotomy (survival) or midline sternotomy (non-survival) is performed. The pericardium is opened, and the left anterior descending (LAD) artery is located.
A polypropylene suture is passed around the second or third diagonal branch of the LAD artery, and the polypropylene filament is threaded through a small vinyl tube, forming a snare. The animal is subjected to 30 min of regional ischemia, achieved by occluding the LAD by tightening the snare. Myocardial ischemia is confirmed visually by regional cyanosis of the epicardium. Following regional ischemia, the ligature is loosened, and the heart is allowed to re-perfuse.
For both survival and non-survival experiments, the myocardial function can be assessed via an echocardiography (ECHO) measurement of the fractional shortening. For non-survival studies, data from sonomicrometry collected using three digital piezoelectric ultrasonic probes implanted within the ischemic area and the left ventricle developed pressure (LVDP) using an apically inserted left ventricle (LV) catheter can be continuously acquired for evaluating the regional and global myocardial function, respectively.
For survival studies, the incision is closed, a left needle thoracentesis is performed for pleural air evacuation, and postoperative pain control is achieved.

The present study demonstrates a highly reproducible animal model of acute regional myocardial ischemia and reperfusion injury in rabbits using a left mini-thoracotomy for survival cases or a midline sternotomy for non-survival cases.

The protocol here provides a simple, highly replicable methodology to induce in situ acute regional myocardial ischemia in the rabbit for non-survival and ...

Implantation of Electroencephalogram and Electrocardiogram Telemetry Devices in Neonatal Rabbit Kits

Pathogenic variants in ion channel genes are associated with a high rate of sudden unexpected death in epilepsy (SUDEP). Mechanisms of SUDEP are poorly understood but may involve autonomic dysfunction and cardiac arrhythmias in addition to seizures. Some ion-channel genes are expressed in both the brain and the heart, potentially increasing the risk of SUDEP in patients with ion-channelopathies associated with epilepsy and cardiac arrhythmias. Transgenic rabbits expressing epilepsy variants provide a whole organism to study the complex physiology of SUDEP. Importantly, rabbits more closely replicate human cardiac physiology than do mouse models. However, rabbit models have additional health and anesthesia considerations when undergoing invasive monitoring procedures. We have developed a novel method to surgically implant a telemetry device for long-term simultaneous electroencephalogram (EEG) and electrocardiogram (ECG) monitoring in neonatal rabbit kits. Here, we demonstrate surgical methods to implant a telemetry device in P14 (weight range 175-250 g) kits with detailed attention to surgical approach, appropriate anesthesia and monitoring, and postoperative care, resulting in a low complication rate. This method allows for continuous monitoring of neural and cardiac electrophysiology during critical points in the development of cardiac arrhythmias, seizures, and potential SUDEP in rabbit models of genetic or acquired epilepsies.

Mechanisms of sudden unexpected death in epilepsy (SUDEP) are poorly understood and challenging to translate from current models. Transgenic rabbits may offer insights into these mechanisms. We describe a method for long-term, continuous electroencephalography and electrocardiography recordings in transgenic rabbit kits to evaluate serious events that may lead to death.

Pathogenic variants in ion channel genes are associated with a high rate of sudden unexpected death in epilepsy (SUDEP). Mechanisms of SUDEP are poorly ...

Tracheal Cannulation in Rabbit Model: A Procedure to Insert Tracheal Cannula into the Rabbit Trachea

Source: Pacheco-Baltazar A, et al. <a href="https://www-jove-com.bdigitaluss.remotexs.co/v/62734">Isolated Lung Perfusion System in the Rabbit Model.</a> J. Vis. Exp. (2021).
This video demonstrates the surgical creation of an opening in the rabbit trachea to insert a tracheal cannula for artificially ventilating the lungs.

Kaniulacja tchawicy w modelu królika: procedura wprowadzania kaniuli tchawicy do tchawicy królika

Source: Pacheco-Baltazar A, et al. Isolated Lung Perfusion System in the Rabbit Model. J. Vis. Exp. (2021).
This video demonstrates the surgical creation ...

JoVE Encyclopedia of Experiments

Large Animal Models

Leporine

Tracheal Intubation for Mechanical Ventilation: A Procedure to Insert Endotracheal Tube in Trachea of Rabbit Model

Source: Marger, L. et al, <a href="https://www-jove-com.bdigitaluss.remotexs.co/v/59976">Calvarial Model of Bone Augmentation in Rabbit for Assessment of Bone Growth and Neovascularization in Bone Substitution Materials.</a> J. Vis. Exp. (2019)
In this video, we demonstrate the tracheal intubation &#8212; an invasive procedure for insertion of an endotracheal tube through the mouth in a rabbit model. This procedure allows for mechanical ventilation of the lungs.

Blind Endotracheal Intubation in Neonatal Rabbits

Podsumowanie

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Model of Ischemia and Reperfusion Injury in Rabbits

Implantation of Electroencephalogram and Electrocardiogram Telemetry Devices in Neonatal Rabbit Kits

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