The long and winding road of acute normovolemic hemodilution

Decreased Transfusion Requirements with Use of Acute Normovolemic Hemodilution in Open Aortic Aneurysm Repair

OBJECTIVES

Acute normovolemic hemodilution (ANH) is an operative blood conservation technique involving the removal and storage of patient blood after induction of anesthesia, while maintaining normovolemia with crystalloid and/or colloid replacement. Developed and used predominately in cardiac surgery, ANH has been applied to the vascular surgery population but data regarding impact on transfusion requirements in this population is limited. The objective of this study is to compare transfusion requirements and coagulopathy in patients undergoing open abdominal aortic aneurysm repair (oAAA) employing ANH to those receiving only product replacement as clinically indicated.

METHODS

This is a retrospective review of patients undergoing elective oAAA at a quaternary aortic referral center from 2017-2019. Those eligible for ANH, no active cardiac ischemia, no valvular disease, normal LV/RV function, CKD < stage 3, HCT > 38%, normal coagulation profile, were included in the study. Patient demographics and characteristics were collected as were operative variables including extent of aneurysm, clamp site, visceral/renal ischemia time, operative time, and transfusion requirements. Post-operative morbidity, mortality, and length of stay were analyzed. Patients with and without ANH were matched and compared. Continuous measures were analyzed with Wilcoxon rank sum tests and t-tests.

RESULTS

Over the study period, 209 oAAA were performed, 76 patients met inclusion criteria; 27 patients underwent ANH while 49 did not. Patients with ANH had less PRBC transfusion intraoperative (Median [25^th,75^th]: 0 [0,1] vs. 1[0,2] units, p=0.02), at 24 hours(0[0,1] vs. 1[0,2] units, p=0.008), at 48 hours (0[0,1] vs. 1[0,2], p=0.007) and throughout the admission (0[0,1] vs. 2[0,2], p=0.011). There was no difference in intraoperative platelet or cryoprecipitate transfusions. At 48-hours, ANH had significantly higher platelet counts (142 ±35.8 vs. 124±37.6 x10(3)/mcL, p=0.044), lower PTT, and lower INR. There was no difference in MI, RTOR, or mortality (1 death overall). ANH patients had shorter LOS (7.0±2.7 vs 8.8±4.8 days, p=0.041).

CONCLUSIONS

ANH during oAAA results in less intraoperative and post-operative PRBC with improved coagulation parameters and a shorter hospital LOS.

Blood conservation in practice: an overview

Allogeneic blood transfusions are associated with risks and unfavourable outcomes. Blood conservation provides an alternative, with potential to improve patient care with limited or no blood transfusion. Many approaches are available, but the most essential ones are simple and cost free.