Coagulation changes during thoracoabdominal aneurysm repair

The cause of coagulopathic hemorrhage during thoracoabdominal aneurysm (TAA) repair has not been well defined in human studies. We investigated changes in the coagulation system associated with supraceliac versus infrarenal cross-clamping to address this critical issue.

Blood levels of fibrinogen, the prothrombin fragment F1.2, D-dimer, and factors II, V, VII, VIII, IX, X, XI, and XII were analyzed in 19 patients with TAAs and four patients with abdominal aortic aneurysms (AAAs) at: (A) induction; (B) 30 minutes into supraceliac (TAA) or infrarenal (AAA) clamping; (C) 30 minutes after release of supraceliac or infrarenal clamps; and (D) immediately after surgery. Preoperative and intraoperative variables, including but not limited to aneurysm type, pathologic findings, comorbid conditions, clamp times, volume and timing of blood products, and clinical outcome, were prospectively recorded. Significance was determined by analysis of variance, Student's t test, and univariate linear regression.

Levels of fibrinogen and factors II, V, VIII, VIII, IX, X, XI, and XII decreased (p < 0.05) at time B versus time A and returned to near baseline by time D. D-dimer and F1.2 increased starting at time B and reached significance (p < 0.05) by time D. Data points were compared for the TAA and AAA groups. Although AAA groups demonstrated a trend to factor activity reduction and increased fibrinolysis, the effect was much less pronounced than in TAA and did not approach significance. No correlation of coagulation change with clamping time was present; however, visceral clamping times were all less than 65 minutes (mean, 44 minutes). Blood and factor replacement was initiated after time B. Univariate regression analysis of factor level versus total blood replacement demonstrated a significant (p < 0.04) correlation between the reduction in the levels of factors II, V, VII, VIII, X, and XII, and the increase in the level of D-dimer at time B and subsequent total blood replacement.

Thoracoabdominal aneurysm repair is associated with a reduction in clotting factor activity and an increase in fibrinolytic function, which occurs after placement of the supraceliac clamp. Explanations include visceral ischemia or a greater and longer ischemic tissue burden as the likely cause of coagulation alterations. Total blood replacement during TAA procedures was correlated to the degree of factor reduction and fibrinolysis at the time of visceral cross-clamping. An aggressive approach to early blood component replacement and to coagulation monitoring could lessen blood loss during TAA repair and avoid potentially disastrous bleeding complications.