Technical Aspects of the Mouse Aortocaval Fistula

The overall goal of this procedure is to create successful aorta, cable fistulas, and this is accomplished by first carefully dissecting the aorta near the puncture site. Next, the aorta is clamped proximal to the desired position of the aorta caval fistula. Then a 25 gauge needle is used to make a puncture from the left aorta to the inferior vena cava.

Finally, hemostasis is accomplished without occluding the aorta caval fistula. Ultimately, Doppler ultrasound is used to show an increase in caval blood flow. The main advantage of this technique over existing methods like aortic caval, an osmosis, is that it is a straightforward method that can be completed in short time and does not use sutures that require time and training Prior to the operation.

Use pulse doppler to take baseline recordings of the supra and infra renal inferior vena cava or IVC and abdominal aorta using B mode, measure the diameter of each vasculature as well as the maximum velocity and waveform in each of the measuring points. Begin the procedure by autoclaving all surgical instruments and vascular clamps. After anesthetizing a male C 57 black, 10 week old mouse in 4%isof fluorine with 0.8 liters per minute.

Oxygen, use a toe pinch to check level of sedation. Place the mouse in a supine position. Attach a silicone mask and administer 2%isof fluorine.

Use a chemical hair remover to remove the hair from the neck to the lower abdomen. First, disinfect the surgical area with 70%ethanol. Under a surgical scope, make a midline incision from the lower edge of the liver to just above the pubis.

Insert a retractor and remove the entire bowel from the abdominal cavity. Then wrap it in saline soaked gauze and place it on the right side. Dissect the membrane that connects the retroperitoneum and lower colon to get a full view of the aorta and IVC.

Apply pressure on the bladder if it is dilated and gets in the way. Next, add a site between half to three quarters of the distance from the left renal vein to the aortic bifurcation. Dissect the left margin of the aorta so that it can be punctured.

The aorta is positioned about 45 degrees behind the IVC, and therefore it must be dissected posteriorly and to the left. Taking care not to dissect between the aorta and IVC, then carefully dissect the infrarenal aorta from the surrounding tissues, so as not to injure the IVC on the left and left renal vein with its tributaries on the right. Using microsurgery clips, clamp the proximal aorta, grasp the connective tissue surrounding the aorta and IVC and rotate it so that the puncture can be made from a slightly dorsal side of the aorta.

While in this rotated position, use a 25 gauge needle to puncture the aorta through to the IVC. The needle should be seen through the thin IVC wall. After confirming a successful hemostasis dec clamp, the aorta rather than dark venous blood flow arterial blood can now be seen flowing into the IVC.

Finally, return the bowels to their natural position and use six oh sutures to close the abdomen. Discontinue the isof fluorine and administer 0.1 milligrams per kilogram of buprenorphine intramuscularly every 12 hours for 24 hours postoperatively, house the animal in a solitary cage during recovery and administer wound care in accordance with your institution's animal care and use guidelines. The following day performed Doppler ultrasound to confirm the A VF and to check for changes in measurements taken prior to surgery.

As shown in these coronal and cross-sectional views of the ideal puncture site placement is critical to obtaining good survival without excessive hemorrhaging, which typically occurs with too much dissection between the aorta and IVC or from inadequate hemostatic. Pressure after practice survival on the first postoperative day is typically over 95%and approximately 91%at postoperative day seven. This schematic demonstrates the importance of wrapping the puncture site with connective tissue prior to applying pressure for hemostasis, allowing good hemostasis without compression of the A VF.In our experience, a successful A VF can be confirmed with ultrasound by the third day.

Once the A VF is confirmed by duplex to be present, it will usually remain stable until day 28. This figure shows typical doppler ultrasound findings in a successful A VF formation. Changes in waveforms are observed at the level of the A VF in the IVC and towards the heart.

The overall A VF confirmation rate on postoperative day three is 71.4%Once mastered, this technique can be completed in 15 to 20 minutes if performed correctly.