Invited commentary

Abstract

Elective surgery for the thoracic aorta has become safer than ever before [1Svensson L.G. Sun J. Nadolny E. Kimmel W.A. Prospective evaluation of minimal blood use for ascending aorta and aortic arch operations.Ann Thorac Surg. 1995; 59: 1501-1508Abstract Full Text PDF PubMed Scopus (22) Google Scholar, 2Davies R. Rizzo J. Kopf G. Elefteriades J. Safety of thoracic aortic surgery in the present era.Circulation. 2001; : 11643Google Scholar]. Much of this improved safety is due directly to improvements in hemostasis. Routine use of activated clotting time (ACT) to guide heparin reversal use of antifibrinolytic agents, advent of water-tight collagen-impregnated grafts, and availability of biological glues have all contributed to hemostatic enhancement. As aortic surgery has become safer and more routine, attention has become focused on blood conservation in aortic surgery, which previously took a back seat to issues of achieving survival, avoiding stroke, and preventing paraplega. Shibata and colleagues provide an important contribution by demonstrating that many patients can avoid blood transfusions in aortic surgery through a concerted blood conservation program. Intraoperative blood salvage is commonly practiced in all types of cardiac surgery. The cornerstone of the approach taken by Shibata’s group is large volume preoperative auto-donation of blood (1600 mL or greater). Two main issues arise with this approach. First, there is some finite danger inherent in delaying surgery for weeks or months to permit multiple auto-donations and blood regeneration. Although the rupture risk for most aneurysms is expressed over months to years, every busy aortic program encounters rupture deaths during the work-up phase. Recent reports suggest that for aneurysm size greater than 6 cm, the monthly rate of rupture, dissection, or death would be greater than 1% per month [3Davies R. Goldstein L. Coady M. et al.Yearly rupture or dissection rates for thoracic aortic aneurysms simple prediction based on size.Ann Thorac Surg. 2002; 73: 17-28Abstract Full Text Full Text PDF PubMed Scopus (716) Google Scholar]. Such a rupture rate would dwarf the rate of potential transmission of HIV from blood transfusion. There exists also a theoretical concern that hemodilution from phlebotomy may engender a hyperdynamic response (increased dp/dt) that may increase the susceptibility to rupture. Patients with symptomatic or extremely large or rapidly growing aneurysms should probably undergo traditional prompt operative scheduling, without prolonged delay for blood harvesting. The second issue is a “horse and cart” or “chicken and egg” paradox. Do the authors believe that blood transfusion caused the complications observed in the transfusion group (prolonged ventilation, infection, renal failure, death)? Is it not likely that these transfused patients had a more complicated course (intraoperatively or postoperatively, especially in terms of bleeding) and thus required blood transfusion? The complications cited may be the result of the more complicated course rather than the blood transfusions per se. Doctor Shibata and his group have made a significant contribution by demonstrating that major aortic thoracic surgery can be done without blood transfusion by supplementing routine conservation methods with large-volume, preoperative auto-donations of the patient’s own blood.