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Vascular Control III Pig Lab.doc


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Vascular Control III Pig Lab.doc

  1. 1. Vascular Control III Vascular Surgery SIU School of Medicine 1
  2. 2. Vascular Control III I. OJECTIVES By the end of this laboratory session participants should be able to… 1) Expose the infra-renal abdominal aorta and common iliac arteries. 2) Perform a tube graft replacement of the infra-renal aorta, analagous to the repair of an infra-renal abdominal aortic aneurysm in human subjects. II. ASSUMPTIONS The anatomy of the abdominal aorta and iliac vessels should be reviewed. In addition, prior to participation in the animal laboratory, the basic techniques of vascular control and the creation of an end-to-end vascular anastomosis should be practiced in the surgical skills lab using laboratory models. III. SUGGESTED READING 1) Zollinger & Zollinger. Atlas of Surgical Operations 7th Edition. McGraw Hill Inc., New York, 1993. Anatomy of the Abdominal Aorta and IVC - Plate IV Resection of Abdominal Aortic Aneurysm - Plate CXXXV-VIII 2) Sabiston DC. Textbook of Surgery 15th Edition. W.B. Saunders Co., Philadelphia, 1997. Aortic Abdominal Aneurysms IV. ANATOMICAL CONSIDERATION There are several anatomic structures that the surgeon needs to be aware of during repair of an infra-renal abdominal aortic aneurysm. 1) Duodenum The 3rd and 4th portions of the duodenum are retroperitoneal structures overlying the abdominal aorta. The duodenum must be carefully mobilized to the right in order to expose the aortic neck (Figure 1). 2
  3. 3. 2) Mesenteric Lymphatic’s As the aorta is cleared of overlying tissue, major mesenteric lymphatic’s joining the cisterna chyli must be ligated prior to division in order to avoid a lymphatic leak. 3) Inferior Mesenteric Vein (IMV) The IMV crosses from left to right over the upper aspect of the infra-renal aorta. To gain adequate exposure, it may need to be divided. Care should be taken to avoid excessive traction on the small bowel that is retracted superiorly in order to prevent tearing of this vein. 4) Left Renal Vein The left renal vein crosses the aorta anteriorly en route to the inferior vena cava (IVC) at the level of the aortic neck. The vein needs to be identified and dissected in order to achieve cephalad retraction (Figure 2). If additional exposure is required, the vein may be divided medially so that the venous flow from the left kidney can be diverted retrograde through the left adrenal, gonadal, and descending lumbar tributaries (Figure 3). The location of the left renal vein should be noted if preoperative CT scan is performed since the vein may occasionally lie posterior to the aorta. A small or absent left renal vein anterior to the aorta may be the only clue (if preoperative CT scan is not performed) that a retrograde left renal vein exists which if unrecognized, may lead to major venous injury during attempts at circumferential proximal aortic control. 5) Sympathetic Nerves Sympathetic fibers cross over the anterior surface of the aorta, communicating with lumbar ganglia laterally and then continuing across the origin of the left common iliac artery (CIA) and downward to join the pelvic plexuses (Figure 4). These nerves affect sexual function and division should be avoided, if possible. 6) Common Iliac Veins The iliac veins are a source of major bleeding that may be quite difficult to control. The proximal right CIA lies directly on top of the left iliac vein just beyond the aortic bifurcation. This is a notorious site for major iatrogenic venous injury since the vein is adherent to the artery and may be torn during attempts at CIA circumferential control. 7) Ureter The Ureter may be seen as it passes anterior to the iliac vessels (Figure 5). In addition, it may be adherent to the surface of large aneurysms 8) Lumbar Veins 3
  4. 4. Lumbar veins, lying posterior to the aorta, may be the source of troublesome bleeding if complete division of the aortic neck is performed. Therefore, the posterior wall of the aortic neck is left intact. 9) Inferior Mesenteric Artery (IMA) Dissection of the tissue overlying the aorta should be performed to the right of the origin of the IMA so that it is not inadvertently injured (Figure 5). V. DESCRIPTION OF THE LABORATORY MODULE A review of the technical aspects of the procedure will be presented and any general questions will be answered. Two participants will be assigned to each pig. The pigs will be sedated, anesthetized, and monitored by the DLAM Surgery Suite staff. The participants will work together to perform a midline laparotomy, achieve aortoiliac exposure, and place a PTFE interposition graft from the infra- renal aorta to the aortic bifurcation. Closure of the retro peritoneum and laparotomy incision will complete the session. VI. DESCRIPTION OF THE PROCEDURE 1) The abdomen is opened through a long midline incision extending from the xiphoid to the pubis (Figure 6). 2) After a thorough abdominal exploration, the duodenum and small bowel are mobilized to the right by incising the peritoneal attachments to the left of the duodenum (Figure 1). 3) The duodenum and small bowel are placed behind a large pad and retracted to the right. Next, the tissue overlying the aorta is incised from the level of the left renal vein to the aortic bifurcation, clipping or ligating any traversing lymphatics and small vessels. 4) The left renal vein is mobilized to allow for upward retraction (Figure 2). If necessary for adequate exposure, the renal vein may be divided (Figure 3). 5) The surface of the aorta is cleared of tissue, keeping to the right of the inferior mesenteric artery in case reimplantation of the vessel is necessary. The IMA is controlled with a double vessel loop (Figure 4, 5). 6) The aortic neck just below the renal arteries is then dissected laterally and blunt finger dissection is used to encircle the aorta. Using an angled vascular clamp, umbilical tape is passed posteriorly to aid in aortic vascular control and cross-clamping (Figure 7). Alternatively, a red rubber catheter, cut across its tip, may be passed initially and then used to guide the vascular clamp around the aorta (Figure 8) 7) The proximal common iliac arteries are dissected anteriorly and laterally. Red vessel loops are passed around each vessel twice using a right angle clamp. 8) The subject is given a heparin bolus (100 units/kg in human patient). 4
  5. 5. 9) Using aortic sizers, the proximal aortic neck is measured and an appropriate graft is chosen. 10) Both common iliac arteries are clamped using angled DeBakey clamps (Figure 9). 11) The aorta is clamped just below the renal arteries using a Satinsky clamp or a Crayford clamp. 12) The aorta is opened longitudinally, using a #11 blade and then the Potts scissors, “T’ing off” the aortotomy proximally and distally (Figure 10). In the human patient with an aneurysm, the thrombus is removed (Figure 11). 13) Bleeding lumbar vessel is ligated from the interior of the aorta using silk sutures in a figure-of-8 fashion (Figures 12, 13). 14) A vigorously back-bleeding IMA may be over sewn using Silk suture placed from within the aneurysm sac to avoid occluding the proximal IMA branches. Sometimes the IMA may need to be reimplanted. 15) The proximal anastomosis is performed using Prolene suture (3.0 Prolene in human subjects) in an end-to-end fashion, beginning posteriorly. The deep posterior bites incorporate a double thickness of aortic wall with each pass. The sutures are run in an over-and-over fashion on each side, ending in the midline anteriorly (Figures 14, 15, 16). Sutures are placed from the interior to the exterior of the vessel to avoid pushing the edge of plaque inward, creating an internal flap or dissection (Figure 17). 16) A vascular clamp is placed on the distal tube graft and the proximal aortic clamp is momentarily released to check for proximal anastomotic bleeding. Bleeding sites may be over sewn using additional Prolene suture. Once hemostasis at the proximal anastomosis is achieved, the aortic clamp is removed. 17) The tube graft is then transected distally at the appropriate length to perform a tension-free, kink-free interposition graft (Figure 18). 18) The distal aortic anastomosis is performed as described for the proximal anastomosis. Prior to completing the final few anterior sutures, the common iliac arteries and the graft are flushed to remove any air or debris by briefly loosening each of the vascular clamps. The sutures are then tied. 19) The vascular clamp on the graft is released to check for anastomotic bleeding. Hemostasis is achieved as described for the proximal anastomosis. 20) One common iliac artery clamp is removed, allowing for blood pressure stabilization after flow is restored to one leg. Until the patient’s blood pressure is in an acceptable range, partial unclamping may be necessary. Once stabilized, the other common iliac artery clamp is removed. The femoral pulses and pedal pulses are checked at this time to be sure distal embolization of atherosclerotic plaque has not occurred. 21) Irrigation may be performed and hemostasis inspected again. 22) The bowel is also checked for viability (IMA ligation or reimplantation). 23) In the case of a human patient, the aneurysm sac is closed around the graft using vicryl suture (Figure 19). 24) Using vicryl suture, the retro peritoneum is closed. 25) The midline fascia and skin are then closed. 5
  6. 6. VII. EQUIPMENT NEEDED Surgical gloves Surgical gowns Surgical masks Scalpel Scalpel Blades #10 Blade #15 Blade #11 Blade Scissors Suture Metzenbaum Angled Potts Electrocautery Forceps Tooth Adson DeBakey Lap Pads 4x4 Gauze Pads Ties 3-0 Silk 4-0 Silk Sutures 3-0 Vicryl 4-0 Vicryl 3-0 Silk 0 Prolene 4-0 Prolene suture – double-armed 5-0 Prolene suture – double-armed 6-0 Prolene suture – double-armed Clamps Right-angle Satinsky Crayford Angled DeBakey (2) Profunda Mosquito Kelley Retractors Deaver Richardson Vein 6
  7. 7. Self-retaining ring system Umbilical tape Red vessel loops – maxi & mini Needle holders Long Short Castroviejo PTFE graft – 6 x 40 or 8 mm x 40 Saline irrigation Suction – Fraser and Yankauer tips VIII. REFERENCES 1. Ouriel, K. and Rutherford R. Atlas of Vascular Surgery: Operative Procedures. W.B. Saunders Company, New York 1998. 2. Rutherford R. Atlas of Vascular Surgery: Basic Techniques and Exposures. W.B. Saunders Company, Philadelphia 1993. 3. Zollinger & Zollinger. Atlas of Surgical Operations 7th Edition. McGraw Hill Inc., New York, 1993. 7