Basic Surgical Techniques in the Göttingen Minipig: Intubation, Bladder Catheterization, Femoral Vessel Catheterization, and Transcardial Perfusion

Endotracheal intubation should be performed whenever a mini pig undergoes general anesthesia to facilitate surgery because it maintains a patent airway permits assisted ventilation and protects the airways from aspirate. Mini pigs can be intubated from various positions, but having the animal on its back tends to be easier for those who regularly carry out human intubation as it presents the airway in a similar manner besides means of assisted ventilation. Equipment needed for endotracheal intubation is slings for opening the mouth low pressure suction with blunt tip veterinary laryngoscope with straight blade between 17 and 25 centimeters long style it syringe with air stethoscope and adhesive tape.

For adult gutting and mini pigs. An endotracheal tube size five to seven millimeters is appropriate. In this video, a 5.5 millimeter tube was used.

The mini pig is placed on its back and properly supported. In order to ensure that the laryngeal passage is kept straight, the tongue is pulled out slightly and the jaw held open by an assistant. Without overextending the head rotation of the airways or excessive extension of the head can occlude airways making the laryngeal opening more difficult to identify.

The laryngoscope is used to depress the tongue and the tip of the suction is used to displace the epiglottis from the soft palate. The tip of the laryngoscope is then used to press the epiglottis upward toward the base of the tongue, revealing the laryngeal opening. Opening the retinoids cartilages and vocal cords come into view and the endotracheal tube is advanced gently with a slight rotation into the trachea.

During expiration, the tube cuff is inflated according to the specifications of the manufacturer. While taking care to avoid excess inflation, which may cause swelling and edema of the airways, pigs have a bronchus to ventilate the right cranial pulmon lobe. It is therefore important to place the tube above the tracheal bifurcation.

This is facilitated by using the correct tube size and by fastening the proximal end of the tube at the level of the snout using adhesive tape. When the mini pig is properly intubated, a free passage of air must be felt through the tube and chest auscultation should reveal respiration sounds in both the left and right side of the thorax. Upon connecting the ventilator with monitoring system to the mini pig, physiological expiratory, carbon dioxide values should be measurable and the carbon dioxide curve that follows the respiration pattern decided by the ventilator settings can be observed.

Endotracheal intubation of mini pigs can be challenging because the laryngeal passage is narrow and the vocal cord's mucus membrane is easily traumatized. If too large a tube or too much force is used, the use of Xylocaine spray or muscle relaxant can facilitate the introduction of the tube. But the use of neuromuscular blockers should only be done by personnel who are well trained in such procedures.

Bladder catheterization may be used as a way to monitor the urine production, which can provide useful information about hydration state as well as renal and cardiovascular function during long surgical procedures. Catheterization of the urinary bladder through the urethra is easily done in female pigs. While this procedure is extremely difficult, perhaps impossible in males for adult mini pigs, a Foley catheter French size eight or 10 is appropriate due to the curvature and size of the external urethral.

Opening a catheter with stylet is preferable. Necessary equipment includes a speculum blunt tip forceps, a syringe with saline lubricant, and a closed system urine drainage bag. In order to best visualize the external urethral orifice during catheterization, the mini pig is placed on its back with the support under the lumbar region.

While an assistant pulls the hind legs cran, the female external urethral opening is located in the floor of the vagina, approximately one third to one half of the distance to the cervix. However, because the animal is placed on the back, the position of the urethral opening will appear to be inverted. The catheter is controlled with the blunt tip forceps, so the tip of the catheter is in continuation of the forceps.

Carefully insert the catheter in the urethral opening. The urethra is easily traumatized if too much force is used during catheterization, however, slight resistance may initially be felt until the catheter has passed the external urinary sphincter. If this problem persists, this may indicate that the animal is not sedated deeply enough.

The solution is to wait a while and let the anesthesia take its effect. As the catheter reaches the bladder, remove the style and urine will be seen flowing. Inflate the balloon with saline according to the specifications of the manufacturer, and gently pull the catheter out until the balloon catches on the bladder neck.

Attach the closed system urine drainage bag, tape the catheter to the tail to avoid accidental displacement of the catheter. When handling the animal with proper training and experience, transurethral bladder catheterization can be done with little difficulty. This minimal invasive procedure can prevent contamination of delicate medical technical equipment and painful bladder extension, which may harm animal and influence the experiment due to increased vagal tone and altered physiological parameters.

Arterial and venous catheterization is useful for obtaining repeated blood samples and monitoring various physiological parameters. When performing vessel catheterization in survival studies, strict aseptic technique must be employed to avoid infections. Necessary equipment includes scalpel, blunt tip, surgical scissors, tissue forceps, small blunt tip, surgical forceps, small self retaining tissue retractor, needle holder surgical swaps, suture with needle heparinized saline as a flush fluid to maintain catheter patency.

Two 18 gauge IV cannula two four French bright tip sheaths with introducer and seldinger G wire. The depth of anesthesia is assessed by testing the interdigital pain reflex. The femoral artery and vein are approached with the mini pig placed on its back and the rear leg retracted laterally.

Identify in the skin fold between the gracilis and sartorious muscle where the pulsation of the superficial part of the medial saphenous artery disappears. Make a longitudinal superficial skin incision cranial to this point, thereby avoiding inadvertently damaging the medial saphenous vessels. Use a blunt tip scissors to dissect the underlying subcutaneous tissue.

The fascia division of the sartorius and gracilis muscle is divided cranial to the penetration site of the medial saphenous vessels. First with a small blunt tip, surgical forceps, and then digitally the two muscle groups are separated with a small self retaining tissue retractor while taking care not to damage the femoral nerve and vessels, the artery is isolated for a length of approximately one to two centimeters. Using blunt dissection, rotate the beveled ven flon needle so the lumen is facing upwards.

Bend the needle a little so it will follow the vessel curvature more easily. Remember to test whether the needle can still move back and forth. The artery is punctured.

The needle retracted and the seldinger guide wire is inserted through the venton tube. Remove the ven flon tube while gently applying pressure on the artery to ensure fixation of the G wire. The sheath with introducer is inserted over the salter wire and advanced to the desired position, after which the introducer and seing or wire is removed.

The femoral vein is located just below and medial to the artery. After isolating the vein using blunt dissection, the vein is cannulated as previously described for the artery. To verify that both the artery and vein are correctly catheterized draw blood from both sheaths and compare the color of the samples.

Whenever drawing a blood sample, remember to subsequently flush the catheters with heparinized saline. In order to maintain catheter patency, the catheters are secured and the skin is closed. With a few sutures, a vessel loop can be placed around the artery and vein in order to fixate the vessels prior to puncture.

Despite its advantages, we generally avoid this additional step because it requires excess dissection of the vessels and increases the risk of damaging the lateral and deep branches. The present footage demonstrates how to catheterize the femoral vessels. Catheterization of femoral vessels is preferable to catheterization of the neck vessels for ease of access.

When performing experiments involving frame based stereotaxic neurosurgery and brain imaging, trans cardial perfusion is the most effective fixation method and yields preeminent results. When preparing mini pig organs for histology and histochemistry, the following equipment is needed for the procedure. Perfusion system relevant profusion fluids, IV cannula syringe, pentobarbital scalpel, blunt tip, surgical scissors, bone shears, and two large self holding forceps, of which at least one has a curved tip.

A self retaining sternal retractor is not absolutely necessary, but it eases the procedure considerably. Trans cardial perfusion must be performed in a well ventilated room with a high power fume extraction system and facilities that allow collection of profuse eight liquids and blood for subsequent safe disposal. After injecting a lethal dose of Penta Barbital, test the interdigital pain reflex.

The best access to the heart and aorta is provided via a median sternotomy. Make a deep longitudinal skin incision extending from the manubrium to the xiphoid process of the sternum. Gain access to the thoracic cavity by making a small incision in the diaphragm just below the xiphoid process.

Insert the bone shears into the thoracic cavity and bisect The sternum care must be taken when performing this procedure because the heart may be adherent at some place to the inside of the sternum. After the sternum has been divided, put in the self retaining sternal retractor and open the thoracic cavity if still intact, make a small incision in the pericardium at the apex of the heart, and then digitally open the pericardial sack. Identify the left ventricle, the right oracle, and the aorta.

Together with the superior caval vein, make a small superficial cut near the apex of the heart and access the left ventricle by perforating the myocardium with a blunt tipped instrument. Insert the perfusion cannula inside the left ventricle and move the cannula tip cran into the aorta. When the cannula is felt between the second and third finger in the aorta, clamp the cannula into place.

With the self holding curved forceps, make an incision into the right oracle and begin injecting the fixative through the perfusion cannula. The flow of profuse eight in the aorta can be felt and blood will pour out through the incised right oracle as the Perfuse eight flow into the mini pig vessels continues. Notice how systemic profusion with para formaldehyde induces hyperextension of the limbs and twitching of the superficial musculature due to aldehyde cross linkage of nerves and muscles.

When using a perfusion system powered by compressed air, make sure to remove the cannula or clamp the clear silicone tube before the canister is empty In order to avoid air from entering the vascular system. In the present video, we use a perfusion system powered by compressed air instead of gravity. The advantage of systems utilizing compressed air is that the hydrostatic pressure exerted is constant during the process, ultimately providing the best organ profusion.