Plasma free hemoglobin and perfusion – some things to consider

1. Plasma free hemoglobin and perfusion – some things to consider Mark Yazer, MD Associate Professor of Pathology, University of Pittsburgh The Institute for Transfusion Medicine

2. Disclosure I have no financial or corporate affiliation with the maker of the Hemobag, Global Blood Resources

3. Encapsulated hemoglobin is good • Hb in RBCs is a miracle of nature • Perfectly suited to do its main job of gas exchange

4. Normal RBC senescence is good Goodbye world!

5. Freehemoglobinis bad

6. Freehemoglobinis bad

8. NO is not N2O

9. Oh NO? Oh yes NO

10. RBCs and Hb are involved in NO transport: Oxygenated RBCs permeable to NO NO NO NO 2,3 2,3 NO 2,3 NO

11. RBCs and Hb are involved in NO transport: Deoxygenated RBCs less permeable to NO NO NO NO 2,3 2,3 2,3 NO NO

12. Free Hb scavenges NO NO NO NO

13. PFHb increases during storage 0.13 g/dl 0.21 g/unit Donadee C et al. Circulation in press

14. PFHb increases during storage Donadee C et al. Circulation in press

15. Free Hb scavenges NO • Transient increase in rat MAP when NO scavenged • Clinical significance? “Whether a transient inhibition in NO signaling is sufficient to increase the risk of multiorgandysfunction or hemostatic activation in at-risk populations of patients remains to be determined” Minutes Donadee C et al. Circulation in press

16. How much PFHb is a problem? • 35 on-pump aortic aneurysm repair patients • Post-operative PFHb cutoff value of 10 μmol/l (0.02 g/dl) had 79% sens, 69% spec for acute kidney injury (AKI) 0.02 g/dl 0.01 g/dl VermeulenWindsant IC et al. KindeyInt2010:913

17. Hemolysis after blood bank cell washing COBE model 2 O’Leary MF et al. Transfusion 2011:955

18. Hemolysis after blood bank cell washing “Our data support a decrease in the expiration time of washed units to 6 hours or less.” 0.17 g COBE model 1 >200 0.13 g 100 NO outcome data presented!! Free Hb (mg/dl) COBE model 2 50 Fresenius O’Leary MF et al. Transfusion 2011:955

19. Hemolysis after routine blood bank manipulations ? COBE Model 1 Harm S et al. submitted

20. Significant amount of PFHb in unit of washed RBCs 0.5 g “The significance of these findings, in particular any morbidity from the potentially increased plasma free Hb burden from irradiated and potentially from washed RBCs, needs to be evaluated in clinical studies.” 0.15 g ? COBE Model 1 Harm S et al. submitted

21. Hemolysis after cell salvage washing Szpisjak DF et al. AnesthAnalg2000:40

23. Hemolysis after post-operative cell salvage • Study to compare the extent of RBC membrane damage in 2 post-op cell salvage devices • Forty patients undergoing first time, elective TKA were enrolled • Unwashed: 20 had post-op cell salvage with a “flip and drip” device (Suretrans, Davol Inc.) • Washed: 20 had post-op cell salvage with OrthoPAT (Haemonetics) device • Samples of the blood to be reinfused were sampled • PFHb and mechanical fragility index calculated Ley JT et al. Transfusion in press

24. What is sublethal injury?

25. MFI measures RBC mechanical stress tolerance

26. Mechanical Fragility Index calculation

27. Demographics of patients in study Ley JT et al. Transfusion in press

28. PFHb not lower in washed salvaged blood 30 g Ley JT et al. Transfusion in press

29. Hemolysis after post-operative cell salvage • The washing device inflicted more sublethal injury on the RBCs than the unwashed device • Predicted mean storage age of washed RBCs: 164 days • Predicted mean storage age of unwashed RBCs: 6 days Raval JS et al. Vox Sang 2010:325

30. Conclusions on washing vs not washing • Previously thought that washing would produce a product with less PFHb than unwashed device • This was not found in our study • Washed device returned significantly more encapsulated Hb • Clinical effect of sublethal injury on washed RBCs unknown

31. Blood bank washing also increases MFI Harm S et al. submitted

33. Effect of Hemobag processing on RBCs • The Hemobag uses modified ultrafiltration to concentrate the residual whole blood in the CPB-circuit • What is the effect of the repeated passes through the hemoconcentrator/ultrafilter on the RBCs? Samolyk KA et al. Perfusion 2005:343

34. Effect of Hemobag processing on RBCs • Collected samples before and after processing with Hemobag from 8 patients undergoing on-pump cardiac surgery • Sorin DHF0.6 hemoconcentrator/ultrafilter • 65 ± 15 years, 6/8 male • 5 CABG, 2 valve repair, 1 ascending Aorta repair • No patients were transfused while on bypass • Average CPB time: 124 ± 34 min • Average length of Hemobag processing: 5.56 ± 1.13 min Harm S et al. submitted

35. Hemobag product is highly concentrated Harm S et al. submitted

36. MFI and PFHb not increased after Hemobag processing Harm S et al. submitted

37. Comparison of PFHb load after washing • Cobe BRAT 2 until mid-2006, then Haemonetics CS5 105.0 mg/dl Kelleher A et al. Anaesthesia online early

38. Effect of Hemobag processing on RBCs • Comparing RBC parameters after Hemobag processing with data from TKA recovery • Unwashed Washed Post-Hemobag • Total PFHb (g) 0.51±0.120.55 ±0.350.23±0.13 • Total Hb (g) 61±12160±10334±11.6 • Total PFHb:Total Hb • 0.0087 0.0035 0.0069 0.20 g/unit Ley JT et al. Transfusion in press

39. Conclusions on PFHb and perfusion • Hb belongs in RBCs! • NO is best left unscavenged • A “safe” level of PFHb is not yet known • Its effects on MAP are transient and of uncertain clinical significance • A washed unit is not devoid of PFHb • Returning some PFHb with cell salvage seems inevitable • Hemoconcentration/ultrafiltration produces a product that is at least on par with other salvage devices • Fragility of intact cells is not increased