COAGULATION CHANGES DURING THORACOABDOMINAL ANEURYSM REPAIR

Purpose: 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 suprace liac versus infrarenal cross-clamping to address this critical issue. Methods: 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 aneur ysms (AAAs) at: (A) induction; (B) 30 minutes into supraceliac (TAA) o r infrarenal (AAA) clamping; (C) 30 minutes after release of supraceli ac or infrarenal damps; and (D) immediately after surgery. Preoperativ e and intraoperative variables, including but not limited to aneurysm type, pathologic findings, comorbid conditions, damp times, volume and timing of blood products, and clinical outcome, mere prospectively re corded. Significance was determined by analysis of variance, Student's t test, and univariate linear regression. Results: Levels of fibrinog en and factors II, V, VIII, VIII, IX, X, XI, and XII decreased (p <0.0 5) at time A 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 grou ps. Although AAA groups demonstrated a trend to factor activity reduct ion and increased fibrinolysis, the effect was much less pronounced th an in TAA and did not approach significance. No correlation of coagula tion change with damping time was present; however, visceral clamping times were all less than 65 minutes (mean, 44 minutes). Blood and fact or replacement was initiated after time B. Univariate regression analy sis of factor level versus total blood replacement demonstrated a sign ificant (p <0.04) correlation between the reduction in the levels of f actors II, V, VIII, VIII, X, and XII, and the increase in the level of D-dimer at time B and subsequent total blood replacement. Conclusions : Thoracoabdominal aneurysm repair is associated with a reduction in c lotting factor activity and an increase in fibrinolytic function, whic h occurs after placement of the supraceliac damp. Explanations include visceral ischemia or a greater and longer ischemic tissue burden as t he likely cause of coagulation alterations. Total blood replacement du ring TAA procedures was correlated to the degree of factor reduction a nd fibrinolysis at the time of visceral cross-clamping. An aggressive approach to early blood component replacement and to coagulation monit oring could lessen blood loss during TAA repair and avoid potentially disastrous bleeding complications.