Case 5--2001. Port-access cardiac surgery and aortic dissection: the role of transesophageal echocardiography

Iatrogenic Aortic Dissection Associated With Cardiac Surgery: A Narrative Review

Iatrogenic aortic dissection (iAD) is a relatively rare but a life-threatening complication associated with cardiac surgery. All members of the team caring for cardiac surgical patients (surgeons, perfusionists, and anesthesiologists) must be familiar with this complication to minimize its incidence and improve outcome. The present narrative review focuses on iAD occurring intraoperatively and during the early postoperative period (within 1 month) of cardiac surgery. The review also addresses iAD that occurs late (beyond 1 month) after cardiac surgery and iAD associated with other procedures. iAD occurs in about 0.06% of cases when the ascending aorta is the site of arterial cannulation, in about 0.6% when the femoral or iliac arteries are used, and in about 0.5% when the axillary or subclavian arteries are used. Mortality is estimated to be 30% but is more than double if not recognized until the postoperative period. Site of origin of dissection is most commonly the arterial inflow cannula (∼33%). Other common sites are the aortic cross-clamp or partial occlusion clamp (∼29%) and the proximal saphenous vein anastomosis site (14%). Sixty percent of cases occur during coronary artery bypass graft (CABG) surgery and 17% during aortic valve surgery with or without CABG. iAD may be somewhat less common in off-pump versus on-pump CABG but is still not very rare. Risk factors, presentation, diagnosis, and management are reviewed in detail as is the key role of the use of echocardiography in the early diagnosis of iAD and for guiding its management.

Negative fluid displacement: an alternative method to assess patency of arterial line cannulation

Optimal flow rate with minimal pressure gradient is the goal of arterial cannulation for cardiopulmonary bypass (CPB). Misplacement of the arterial cannula or vascular pathology can lead to hemolysis or intimal damage with subsequent aortic dissection. The risk of dissection with aortic cannulation is low, 0.04-0.2% for ascending aortic cannulation and 0.2-3% for femoral cannulation. However, dissection-related mortality is significant. Common methods for assessing adequacy of arterial cannulation include minimal pressure when injecting 100-mL boluses and the presence of pulsation in the cannula. Using these techniques, misplacement of the cannula can be masked due to the small amount of volume that is transfused during the assessment. Displacement of fluid into a cannula that is in a false lumen or close to the intimal surface may not indicate a misplaced arterial cannula. Negative fluid displacement is an alternative method of evaluating the integrity of arterial cannulation. During retrograde arterial priming (RAP), fluid is drained from the arterial cannula into a collection bag. Absence of fluid return or a flow < 500 mL/minute is indicative of either arterial line occlusion or cannula misplacement. At this point, the arterial cannula can be repositioned prior to instituting CPB. Since using this technique in over 13000 bypass procedures, we have had only one dissection. This one event occurred during partial occlusion clamping of the ascending aorta. With increased use of femoral cannulation for minimally invasive cardiac surgical procedures, this RAP technique can enhance the perfusionist's and the surgeon's ability to safely perform bypass in the presence of higher dissection risk.