Impact of Cooling Strategies on Transfusion Requirements in Aortic Hemiarch Surgery

A. V. Norman¹, S. Challa², A. M. Wisniewski², R. Strobel², M. Mazzeffi³, M. Joseph⁴, D. Tang⁵, R. Singh⁶, M. Kontos⁷, M. Quader⁴, K. Yount², N. Teman², O. Preventza², J. Beller^2
1University of Virginia Health Systems, Charlottesville, Virginia ²University of Virginia, Charlottesville, Virginia ³University of Maryland, Baltimore, Maryland ⁴Carilion Clinic, Roanoke, Virginia ⁵Inova Heart and Vascular Institute, Falls Church, Virginia ⁶Inova Fairfax Hospital, Falls Church, Virginia ⁷Virginia Commonwealth University, Glen Allen, Virginia

Purpose: Deep hypothermic circulatory arrest (DHCA) is a strategy utilized in aortic arch surgery. Hypothermia is known to precipitate coagulopathy and increase bleeding. Conflicting data from single-center studies suggest that moderate hypothermic circulatory arrest (MHCA) may reduce transfusion requirements. We hypothesized that MHCA would reduce transfusion requirements.

Methods: We examined patients who underwent aortic hemiarch surgery for aneurysmal disease between July 2014 and May 2023 utilizing a multi-center regional collaborative database. Patients were stratified by MHCA and DHCA, which were defined as 24-28°C and < 24°C, respectively. Patients with aortic dissection, a temperature nadir outside of these parameters, or who had missing transfusion data were excluded. Total number of transfusions were examined for packed red blood cells (pRBC), fresh frozen plasma (FFP), cryoprecipitate, and platelets. Hierarchical regression analyses were performed to account for hospital random effect and assess for risk-adjusted preoperative and intraoperative predictors of increased transfusion requirements.

Results: We identified 451 patients who underwent aortic hemiarch surgery, of which 299 (66.3%) underwent MHCA and 152 (33.7%) DHCA. Baseline characteristics were largely similar between groups. MHCA patients less frequently underwent concomitant root operations (29.1% vs. 39.5%, p=0.03). MHCA was associated with shorter cardiopulmonary bypass (124 mins [100,161] vs. 204 mins [164,252], p< 0.01) and circulatory arrest times (11 mins [8,15] vs. 21 mins [17,30], p< 0.01). Cerebral perfusion was more frequently utilized in MHCA patients (98.3% vs. 84.9%, p< 0.01). In unadjusted analysis, MHCA patients received fewer pRBC (0 [0,1] vs. 1 [0,3]), cryoprecipitate (1 [0,1] vs. 1 [0,2]), and platelet transfusions (0 [0,2] vs. 1 [0,3], all p< 0.01) while the number of FFP transfusions were similar (Figure). Rates of renal failure (2.4% vs. 5.9%, p=0.05) and stroke (2.0% vs. 1.3%, p=0.60) were similar; however, the MHCA group had a lower incidence of prolonged ventilation (9.7% vs. 17.8%, p=0.01) and atrial fibrillation (23.4% vs. 34.2%, p=0.02) with shorter duration of intensive care stay (49 hours [27, 76] vs. 84 hours [48, 148], p< 0.01). Operative mortality was lower in the MHCA group (1.3% vs. 5.9%, p< 0.01). In risk adjusted analysis, cardiopulmonary bypass time, not MHCA, was independently associated with transfusion requirements (Table).

Conclusion: MHCA is associated with fewer transfusions and improved outcomes in selected patients for aortic hemiarch surgery. Although the degree of hypothermia was not independently associated with transfusion requirements, prolonged time on cardiopulmonary bypass in DHCA accounts for these differences. MHCA during hemiarch surgery may mitigate perioperative complications including transfusion needs.

Identify the source of the funding for this research project: This work was supported by a research grant from NHLBI/NIH (T32HL007849).