The overall goal of this procedure is to illustrate the methodology for femoral artery and venous catheterization for chronic and acute uses. This is accomplished by first preparing a pocket in the lower leg for the catheter for placement. The second step is to isolate the femoral artery and vein and prepare them for catheter placement.
The third step is to insert and secure the catheters within the femoral vein and artery. The final step is the surgical wrapup, including securing the catheters to prevent their movement during animal movement or growth. Closing the incisions and placing the animal in the tether type jacket with careful aseptic surgical techniques and catheter placement and maintenance.
It is possible to sustain patent chronic catheters for future blood draws, drug administration or blood pressure and heart rate measures. Visual demonstration of this method is critical. The current available illustrations and text protocols lack much of the necessary detailed visual representation needed to implement this method.
Demonstrating the procedure will be Dr.Carrie Northcott After anesthetizing, shaving and scrubbing the experimental animal, place a sterile drape over the surgical areas. Then begin the procedure by making an approximately one to one and a half centimeter horizontal incision on the back of the rat's neck at the level of the shoulder blades using a pair of blunt tip scissors. Dissect the subcutaneous pocket approximately the size of a quarter in the animal's back.
Cover the incision with a sterile saline soaked piece of gauze. Then after turning the rat onto its back, make an approximately one to one and a half centimeter incision along the angle of the hind leg. Now holding the blunt tip scissors at a 45 degree angle, dissect within the incision to separate the connective tissue until the femoral artery and vein are exposed.
After blunt, dissecting another small quarter size pocket below the skin, this time along the inside of the leg, place retractors into the incision area so that the artery and vein can be viewed fully. Then using fine tip forceps, gently separate the nerve that is along the femoral artery, away from the artery and vein, being careful not to damage the nerve. Next, separate the artery and vein is one unit exposing about a one half to one centimeter in length section of both vessels.
Now holding the forceps perpendicular to the vessels, separate the vessels in parallel to avoid damaging them. To begin, first soak some two by two gauze in sterile saline. Then after placing the gauze over the incisions, turn the rat to its stomach, ensuring that the top of the hemostats is point up that is not towards the spine.
Insert long straight Rochester pain. Four steps into the incision on the back of the animal and guide them subcutaneously down the back to the level of the hips at approximately the hip region. Turn the hemostats towards the incision and push the tip of the hemostats out of the prepared leg incision.
Then gently grasping the ends of the catheters opposite the ends to be inserted with the forceps. Carefully pull the catheters through the back and out the neck.Incision. Fill blunted needle syringes with 20 units per milliliter heparin saline solution, and then place them in the ends of the catheters taking care to ensure that there are no air bubbles, fill the catheters and check that the catheters are patent.
Finally leaving the syringes attached to the end of the lines, turn the rat onto its pack. Once again. First place a folded piece of sterile four oh silk under the femoral vein, and then cut the silk at the folded end, making two pieces of silk under the vein.
Then separate the two pieces of silk pulling one piece distally towards the leg of the animal and pulling the other proximally towards the body. With the suture on the proximal side, nearest the body tie a loose ligature. Do not tighten it fully.
Now grasp the silk at the knot with small hemostats pulling it taut without tightening the knot. Pull the other piece of silk as far as possible towards the leg in order to give yourself a nice length of vessel to work with. Using forceps.
Tie this suture into a triple knot. Occluding the vessel. Place one to two drops of lidocaine onto the vein using the van micro dissecting scissors.
Make a small incision at a 45 degree angle and approximately one third to one fourth of the way through in the vein. Then use a forceps to carefully grasp the vein catheter. Next, place a fine tip to 45 degree forceps into the incision.
Gently open the 45 degree forceps within the vein, and then carefully place the venous catheter under the forceps and insert the catheter into the vein. After the catheter is in the vessel, be sure to hang onto the catheter with a set of forceps at all times until it is secure in the animal, or it is likely that the catheter will come out when the ligature is reached. Loosen the knot by adjusting the hemostats so the silk is no longer taut and the catheter can be fully inserted.
When the catheter is fully inserted, tighten the proximal ligature around the vein in the catheter tying a triple knot using the silk near the leg. For a distal ligature, tie the silk around the catheter. Then slowly draw back the syringe until there is a small amount of blood visible in the catheter to ensure that the knot is not too tight.
After checking that the catheter is functional, depress the plunger until the blood is no longer visible. And finish tying a triple knot in the silk to ensure that the catheter does not come out of the vein. Following this, catheterize the femoral artery in a similar fashion.
Briefly place four oh silk under the artery. Then separate the two pieces of silk pulling one piece distally towards the leg of the animal and pulling the other proximally towards the body. Unlike with the vein, when catheterizing the artery first, pull the distal piece of silk towards the leg and tie this suture.
With a triple knot occluding the vessel due to the blood flowing from the heart to the leg. This will cause the vessel to enlarge. Now with the proximal silk piece remaining, tie a loose ligature, grasp the silk at the knot with small hemostats pulling it taut without tightening the knot.
Next place one to two drops of lidocaine onto the artery. Make a small incision at a 45 degree angle, approximately one third to one quarter of the way through the artery, using a forceps to hold open the lumen, slip the catheter into the artery. Then using the proximal ligature, tie a triple knot around the artery and catheter.
Next, check the blood flow in the catheter and tie the distal ligature as before. After checking that the catheter is functional, depress the plunger until the blood is no longer visible, and finish tying a triple knot in the silk. To ensure that the catheter does not come out, make a dime to quarter size loop in the catheters and place them on the inside of the leg.
After placing both catheters, secure them with one to two stitches of five oh surgical sutures into the muscle layer. Close the incision with uninterrupted sutures using four oh lon, and then after turning the rat onto its stomach, make another loop in the catheters about the size of a quarter and place it in the pocket dissected in the back of the animal. Close the incision with sutures.
Then using a drop of vet bond, secure the catheters in the back. Clamp the catheters near the back incision with padded hemostats and remove the syringes from the ends. Finally fit the rat with a tether type jacket, feeding the catheters through the spring on the jacket.
Put the syringes back on the catheters. Remove the hemostats and tighten the jacket. Then replace the hemostats and trim the catheters.
Now cap the catheters to maintain the heparin lock and remove the hemostats. Begin by clamping the catheter with padded forceps. Then remove the catheter.
Plug a blunt tip needle and place a blunt tip syringe with lock solution onto the catheter, unclamp the forceps, and then fill the catheter with 0.3 milliliters of lock solution rec. Clamp the catheter and remove the syringe. Then replace the catheter plug and unclamp the forceps.
Finally, gently push the plug in slightly to ensure no blood is in the tip of the catheter. Following surgical recovery, blood pressure measurements can be obtained from the awake freely moving animal. The equipment used for these measurements include the power lab, eight sp, the quad bridge and the blood pressure transducer as denoted with the dotted lines.
In this experiment, phenyl, rine and alpha one adrenergic receptor agonist was administered into the femoral vein line. The animal's blood pressure was simultaneously measured from the femoral arterial line, and as can be seen in the figure, the pulse pressure represented in the top graph and the mean arterial pressure represented in the bottom graph immediately increased in response to the drug. The heart rate, however, temporarily dropped and then gradually increased to pre drug levels after the phenylephrine was administered.
Then after recovering from the effects of the alpha adrenergic agonist, the administration of the non-selective alpha adrenergic antagonist, phentolamine indicated with the second dotted line caused the animal's blood pressure to decrease. Once again, once mastered, this technique can be done in 20 to 30 minutes.
