The overall goal of the following experiment is to study the effects of spinal cord ischemia in a murn model. This is achieved by first inserting a laser doppler probe over the femoral artery. Next, the sternotomy is performed to access the aortic arch and left subclavian artery.
Then careful dissection of the aorta and subclavian arteries is performed in order to adequately reduce arterial blood flow to the spinal cord. Results are obtained. The cho, a postoperative neurologic deficit, which is based on the Baso mouse score.
The main advantage of this technique over other existing methods, such as the lateral thoracotomy, is that the plural space is not violated. This method can help to answer questions for the pathophysiology or spinal cord, isch perfusion injury, and and provide potentials for pharmacological interventions. The implication of this technique extends towards therapies in preventing paraplegia following spinal cord ischemia.
Though this method can provide insight into paraplegia, which complicates thoraco surgery, it can also be applied to other disease processes causing acute spinal cord ischemia, such as hypotension or vascular path. Generally, individuals new to this technique will struggle with the dissection of the aortic arch because extreme care is needed to avoid death, hemorrhage, or pneumothorax. So we first thought about this technique after we had several difficulties with lateral thoracotomy approach, which is widely published in the literature, but was associated with a higher mortality in our animals.
Visual demonstration of this method is critical as extreme caution is needed during the mediastinal dissection to prevent interoperative mortality. After anesthetizing a mouse according to the text protocol, ensuring that it is sufficiently sedated and removing the hair from the midline thorax and left lower extremity ventral surface, insert a lubricated rectal probe into the mouse's rectum and secured in place to the operating bed. Adjust the heating bed for a target rectal temperature of 36.5 degrees Celsius.
Next, make a small incision over the femoral artery and dissect the skin away from the subcutaneous tissue. Then insert a laser doppler probe over the femoral artery. Adjust the probe positions until the perfusion monitor registers greater than 800 perfusion units to carry out dissection of the aortic arch and subclavian artery.
Make a two centimeter skin incision above the sternal notch and gently dissect the skin away from the subcutaneous tissue. Dissect free the submandibular gland if bleeding occurs. Use a cotton swab to apply gentle pressure in the avascular plane.
Divide the submandibular gland through the midline using forceps. Gently lift the sternum and with scissors carefully make a one centimeter midline sternotomy through the midline of the sternum. Place five oh retraction sutures on each side at the edge of the sternum and retract the sternum laterally securing sutures to the operating bed.
Next, using blunt dissection, free the strap muscles along the trachea. Then use scissors to divide the left strap muscle to improve exposure. Dissect the thymus free from the surrounding tissue.
Continue blunt dissection until the great vessels are visualized. Using extreme caution to prevent entering into the pleural space, then place vascular clamps on the aortic arch and the left subclavian artery. Verify that the distal flow has been appropriately disrupted, which will be seen as a greater than 90%reduction in perfusion units.
Continue the occlusion for four to eight minutes. When the time is up, remove the vascular clamp and verify hemostasis to close the sternotomy and skin. Begin by removing the retraction suture on the left side of the mouse.
Use the right retraction suture to close the sternotomy and use a running five oh stitch to close the skin. Allow the mouse to recover in a cage placed on a heating pad before returning it to a normal cage with access to food and water. Monitor it for signs of respiratory distress and if necessary, euthanize according to the text protocol.
Finally, use the Baso mouse scale for locomotion to monitor the animal. At 12 hour intervals, mice underwent sham surgery or aortic occlusion for four to eight minutes. And postoperatively the animals were rated by the Baso mouse scoring system shown here.
This graph illustrates that mice that underwent sham surgery had no observable functional deficits at any point.Postoperatively. Mice subjected to moderate ischemia had near normal hind limb function at 12 hours with progressive functional decline to complete paralysis by 48 hours. And mice in the prolonged ischemia group had complete paralysis following surgery without any recoverable function.
After watching this video, you should have a good understanding of how to safely dissect the aortic arch and adequately reduce arterial blood flow of the spinal cord.
