Blood conservation strategies need to be more aggressive in revision cardiac surgery. When compared with first-time cardiac surgery, blood product utilization for revision cases was two to four times greater—a difference that is much greater than the 75% increase previously reported (Transfusion 1995;35:850-854). According to the researchers, understanding transfusion requirements should lead to better preparation from anesthesiologists and use of more targeted interventions, and possibly reduced blood use.
“Knowing that revision cases have a dramatic increase in blood utilization should allow anesthesiologists to be better prepared for either emergency bleeding or hemorrhaging upon opening the chest, or more diffuse microvascular bleeding that’s harder for surgeons to control,” said Nadia Blakemore Hensley, MD, assistant professor of anesthesiology and critical care medicine at the Johns Hopkins University School of Medicine, in Baltimore. “But these patients should also be targeted ahead of surgery, when there is time to increase hemoglobin with erythropoietin or iron supplementation, or by correcting coagulopathies.”
As Dr. Hensley reported, a study by Bracey et al demonstrated that revision cardiac surgery has a 75% greater transfusion requirement than first-time cardiac surgery, but these data are more than 20 years old. Moreover, said Dr. Hensley, this study was conducted before restrictive transfusion triggers and newer blood conservation measures that have been implemented (JAMA 2010;304:1559-1567; N Engl J Med 2015;372:997-1008).
Dr. Hensley and her colleagues acquired electronic health record data from a web-based portal and their institution’s anesthesia information management system. Cases were between January 2009 and June 2016. The researchers aimed to examine both coronary artery bypass (CAB) and non-CAB patients, as well as intraoperative and whole-hospital transfusion requirements for all major blood components. Four categories of surgery were defined: 1) redo CAB, 2) non-redo CAB, 3) redo non-CAB and 4) non-redo non-CAB. Children younger than 18 years of age were excluded, as were minimally invasive procedures (e.g., transcatheter aortic valve replacement). Investigators included 6,445 patients in the final analysis.
Transfusion Requirements Have Changed
As Dr. Hensley reported at the International Anesthesia Research Society 2017 annual meeting (abstract 1879), with CAB surgeries, the mean transfusion requirements for redo patients were two- to fourfold greater than the non-redo CAB patients. For non-CAB surgeries, however, the mean transfusion requirements for redo cases were two times greater.
CAB, coronary artery bypass; CRYO, cryotherapy; FFP, fresh frozen plasma; PLTS, platelets; RBCs, red blood cells.
“A lot has changed in cardiac surgery in the past 20 years,” said Dr. Hensley, who noted that the concept of patient blood management was only introduced in the last 10 years or so. “Primary sternotomy surgeries are probably not getting transfused as much as they were in the past because of more restrictive transfusion triggers. In addition, cardiac surgeons now routinely use antifibrinolytics, and have incorporated strategies like acute normovolemic hemodilution, viscoelastic point-of-care testing and routine use of hemoconcentrators on cardiopulmonary bypass to target blood conservation.”
According to Dr. Hensley, understanding the requirements for transfusion and the factors that correlate with blood utilization may help anesthesiologists prepare appropriately for revision cardiac surgery. Microvascular bleeding, for example—which occurs when layers of scar tissue from a primary sternotomy are dissected—is common in revision cases but is not easily seen or repaired by surgeons. Data concerning surgical duration of revision cases also showed significant increases in bypass or aortic cross-clamping time, which has been linked to increased blood transfusion requirements in previous studies.
“Anesthesiologists should prepare for injuries to any major structure when going into the sternum,” Dr. Hensley added. “At our institution, the culture is to have a cooler of blood in the room in case of accidental punctures in the right ventricle or pulmonary artery, which can cause fast hemorrhaging and demand immediate blood.”
Finally, said Dr. Hensley, these discrepancies in blood utilization should encourage providers to be more aggressive with blood conservation strategies or tailor strategies specifically to revision cases. Use of iron and erythropoietin in patients with anemia; acute normovolemic hemodilution; specific perfusion methods, such as hemoconcentration; and viscoelastic testing to determine requirements for plasma and platelets may help conserve blood in the future, the authors noted.
Moderator of the session, Daniel Stoltzfus, MD, anesthesiologist at MedStar Washington Hospital Center, in Washington, D.C., suggested that it would be interesting to stratify results according to surgeon and inquired about the use of blood factor concentrates.
“We all know that we can make a difference in outcome—someone who is meticulous compared to someone who is less so,” Dr. Stoltzfus said. “Were blood factor concentrates like PCC [prothrombin complex concentrate] or factor VII used or just pure component products?”
“The majority of [blood factor concentrate] cases are revision, but we haven’t looked at those data because the number is going to be so low that I doubt it will be significant, but we do have plans for additional analyses,” Dr. Hensley said. “We are looking at more granular data of these patients so that we can categorize them correctly and understand the effect of more complex surgery on the risk of bleeding. Even after accounting for confounding variables, revision surgery was an inde pendent risk factor for both moderate and massive transfusion.”