Allan Doctor, MD

Professor of Pediatrics,Biochemistry and Molecular Biophysics

Washington UniversityDivision of Pediatric Critical Care Medicine

Saint Louis Children’s Hospital

Blood & ECMO Transfusion Thresholds and Anticoagulation Management

Dilemmas in Decision MakingMitigating Risk

● Research Funding NIGMS, NHLBI American Heart Association Doris Duke Foundation Children’s Discovery Institute Terumo, BCT; Entegrion

● Industry Consulting Viasys, iNO therapeutics Galera Pharmaceuticals Nitrox ~ N30Pharma Terumo, Novartis, Biogen

● Intellectual Property S-nitrosothiol assay systems NanoCrit artificial RBC system

● Equity KaloCyte, Inc. Founding President

● RBC Transfusion Decision Making Role of RBCs in O2 delivery to tissue RBC Storage Lesion Biology & Risks of Transfusion Physiology of anemia and evaluation of tolerance

● Anticoagulation Management Nomenclature & Physiology of Coagulation System Monitoring the Coagulation System Approaches to anticoagulation Response to (undesired) clotting and Bleeding

carbon dioxide oxygen● ~ 20-30 trillion RBCs circulate in the average adult ~ 45 gm dry weight, whole blood ~ 7% body mass RBCs comprise ~ 25% of cells in human body

● ~ 1.4M RBCs produced/second, ~ 200B/day Lifespan ~ 100 – 120 days Replace ~ 1% of the circulating mass/day Average human produces ~ 250 kg RBCs over a lifetime

● Arterio-venous transit requires ~ 20 sec. (at rest) RBCs travel ~ 400 km prior to senescence/clearance

● RBCs have roles beyond simple gas transport Regulation of regional vascular tone Major role in vascular antioxidant systems Participate in Immune regulation (self-recognition) Participate in physiologic response to hypoxia (organism and regional)

● Oxygen Transport ● Improve oxygen transport

Thoughtful Decision Making:Ensure that happens.

● RBC rheology Progressive loss of deformability Progressive adhesion to activated endothelium

● RBC metabolism Abnormal glycolysis & energy metabolism

ATP depletion (ion pumps fail) 2,3 – DPG depletion (p50 falls, O2 loading/delivery altered) Reducing equivalent (NADPH, GSH) depletion (oxidative stress) (↓ pH, ↑ lactate)

● Generation of Cytokines and Bioreactive agents Elaboration of RBC-derived microvesicles (vasoactive & pro-inflammatory)

Solubile CD40 ligand, lyso-PCs (activate primed PMNs)

● RBC control of regional blood flow Failed context-responsive control of vasoactive effectors in plasma Disruption of RBC NO metabolism

ABBB RBC Tx Guideline. Ann Intern Med. 2012;157(1):49-58.

Chaterjee. JAMA Intern Med. 2013.

Transfusion Increases Risk of All-Cause Mortality

Transfusion Increases Risk of MI● Mortality risk ratio 2.91 (95% CI: 2.4 – 3.4)● # needed to harm: 8 (95% CI: 6 - 17)● MI risk ratio 2.04 (95% CI: 1.06 – 3.93)

Villanueva. NEJM. 2013. 368:11-21.

● Pooled risk of infection Restrictive: 10.6% (95% CI: 5.6% - 15.9%) Liberal: 12.7% (95% CI: 7.0 – 18.7%) RR for any infection (favoring restrictive) is 0.92 (95% CI: 0.82 – 1.04) RR for serious infection (fav. restrictive) is 0.84 (95% CI: 0.73 – 0.96)

● Stratified risk (by patient type) Orthopedic surgery RR (fav. restrictive) is 0.72 (95% CI: 0.53 – 0.97) Sepsis RR (favoring restrictive) is 0.51 (95% CI: 0.28 – 0.95) No differences for all other categories

● NNT with restrictive strategy to prevent serious infection 48 (95% CI: 36 – 71)

Rhode. JAMA. 2014.

Holst. BMJ 2015;350:h1354

Fiser. PCCM. 2014;15:806-13.Smith. Perfusion. 2013;28:54-60.

2001-10; 484 ECMO runsRBC transfusion of 10 mL/kg/day was associated with a 24%increase mortality (OR 1.024, 95% CI 1.004-1.046, p=0.018).

o 1984-2011; 827 ECMO runs Grp 1: non-leukoreduced, Grp II: leukoreducedo Group I each Tx of 10 mL/kg/d of pRBC ~ 33% increase in mortality (P <0.05)o Group II each Tx of 10 mL/kg/d of pRBC ~ 21% increase in mortality (P = 0.07)

Jackson. J Surg Res. 2014.;192:6-11.

Voelker. Artif Organs. 2015.

● Single Center, Univ Leipzig, GDR● Hb ‘trigger’ 7 g/dL or ‘when physiologic triggers were present’● Overall survival of ~60% consistent with rates in ELSO registry and CESAR trial

Agerstrand. Ann Thorac Surg. 2015.

● Single Center, Columbia● Hb ‘trigger’ 7 g/dL, low dose

anticoagulation (aPTT 40-60), autotransfusion at decannulation

● Overall survival of ~74%

● Donor and Native RBCs do not exhibit similar physiology.

● These differences progress as a function of storage duration.

● These differences impair O2 delivery to tissue, even by native RBCs.

● Transfusion, surprisingly, harms critically ill, anemic patients.

● There is sufficient basic, translational, & clinical evidence to support a fundamental practice change in transfusion medicine

● RBC Transfusion Decision Making Role of RBCs in O2 delivery to tissue RBC Storage Lesion Biology & Risks of Transfusion Physiology of anemia and evaluation of tolerance

● Anticoagulation Management Nomenclature & Physiology of Coagulation System Monitoring the Coagulation System Approaches to anticoagulation Response to (undesired) clotting and Bleeding

Dalton (CPCCRN). PCCM. 2015;16:167-74

o Bleeding occurrence: 38%o 40% reduced survival (RR 0.59; 95%CI: 0.53-0.66)

o Thrombosis occurrence: 31%o 33% reduced survival (RR 0.67; 95%CI: 0.60-0.74)

● Initiation (coagulation is initiated by formation of TF-VIIa complex) Exposure of subendothelium (collagen & TF bearing cells) Engagement of circulating VIIa with exposed TF TF-VIIa complex

Platelets adhese to exposed collagen and ‘activate’ Counter-regulatory system: circulating & endo-bound ATIII and TFPI, endo based

thrombomodulin/thrombin activate APC & prevent propagation to uninjured regions

collagen

● Tissue Factor Pathway (extrinsic)● Contact Activation Pathway (intrinsic)● Final Common Pathway (thrombin burst/fibrin generation)

Zymogens (circulating inactive enzyme) of a serine protease are activated, then catalyze the next reaction in a cascade (signal amplification). Cofactors: Ca+, phospholipid (plt memb. platform for complex formation) Regulators (deficiencies cause thrombophilia)

● Amplification (Action moves from TF bearing cell/matrix to activated platelet surface) TF-VIIa complex Xa activates thrombin, which ‘prepares’ plt surface (PAR/PS) vWF (from inj endo) facilitates platelet adhesion and integrin activation Activated plts release granules (ADP, 5HT, PAF, vWF, pF4, TXA2), which further activate

plts and constrict vessels

● Propogation (thrombin burst leads to fibrin formation) ‘Ten’ase and ‘Prothrombin’ase complexes (Xa & Va key) assemble on plt surface and

generate the ‘thrombin burst’ fibrin (from fibrinogen) Granule contents activate PLA2, activates GIIb/IIIa, crosslinks plts & fibrin

● normal process that prevents disproportionate clot growth and enables clot dissolution after healing

● Plasminogen is incorporated into clots during formation● t-PA & urokinase are slowly released by endothelium &

matrix after vesssel injury● t-PA and UK convert plasminogen to plasmin (initiating

fibrinolysis)● (regulated by) Plasminogen activator inhibitor (PAI 1/2) also

produced by endothelium & inhibit both t-PA and UK

● Fibrin degradation products are generated (FDP) D-dimer is a specific FDP FDPs compete with thrombin, slowing clot formation (retard conversion of

fibrinogen to fibrin) [part of DIC pathology]

● Fibrinolysis pharmacologically inhibited by: serine protease inhibitor Aprotinin [inhibits plasmin] (no longer available) Lysine analog Tranexamic Acid (TXA) & ε-aminocarpoic acid (Amicar)

inhibit plasminogen activation, efficacy of TXA >>> Amicar

● Loss of HMW VWF multimers● Impaired VWF binding to platelets

and collagen● Dx: ratio of collagen binding capacity

to VWF-antigen (VWF:CB/VWF:Ag) & VWF multimeric analysis

● Rx:● Desmopressin● VWF containing concentrates● Plasmapheresis● Recombinant FVIIa● Antifibrinolytic (Amicar & TXA)

● Attempt to manage shear

Tiede. Blood.2011;117:6777-6785

Heilmann. Intensive Care Med. 2012. 38:62–68. Kalbehnn. J Atheroscler Thromb. 2015. 22:265-71.

22/33 (66%) with aVWFS Bled

Pasala. ASAIOJ. 2014; 60:419–423.

Tauber. Anesth Analg. 2015;120:730–6.

● ACT (Activated Clotting Time) [target ~ 180-220 sec] Whole blood, POC, Time to clot after contact activation (XII XIIa) ACT varies with heparin effect , but loses fidelity in complex situations Useful at extreme levels of anticoagulation (CPB/ECMO utility)

Atallah. Perfusion 2014;29:456-461. Bembea. ASAIOJ. 2013;59:63-8.

● Anti-Xa (activity or concentration) [target ~ 0.3-0.7 IU/mL] Measures ability of heparin-bound ATIII to inhibit Xa FXa and ATIII (+/-) added to patient plasma, residual Xa activity measured ~ reliable measure of heparin pharmacokinetics (particularly for LMWH) does not measure heparin pharmacodynamics (varies with patient FX &

thrombin, fibrinogen, etc.) [less so for LMWH] Does not measure overall ‘hemostatic potential’, which also includes thrombin

generation/activity, fibrinogen, platelet #/function, and fibrinolysis.

Desphande. PAS Meeting. 2015.

● PT (extrinsic p’way) & aPTT (intrinsic p’way) PT: TF + WB, activating the extrinsic pathway. Rate dominated by FVII. FVII

has a short t1/2; depends on VitK. aPTT: add kaolin/silica (any negatively charged substance as surrogate for

collagen); phospholipid + Ca++ (partial thromboplastin) also added for the tenaseand prothrombinase complexes of the final common pathway.

aPTT not affected by VII deficiency. Both require > 50% less of any given factor to prolong

● ATIII activity [target varies with heparin pharmacokinetics] Evaluate thrombin and/or Xa inhibition in the presence of heparin +/- mix subject plasma with excess thrombin, Xa and heparin Add artificial chromogenic substrate for thrombin, measure ‘activity’ May tell you if ATIII is rate limiting in thrombin/Xa inhibition

collagen

● R – time until clot initiation (2 mm)

(+/-) VIIa & TF (initial Xa/thrombin activation)● K – time until clot reaches threshold ‘strength’ (20 mm)

Pace of fibrin initiation (fibrinogen may be rate limiting)● α angle – rate of ‘gelation’

Fibrinogen/Thrombin burst (fibrin buildup) (as above)● MA/G - maximum amplitude, clot ‘strength’

Fibrin & Platelet ‘bonding’ via GPIIb/IIIa (~ 80% plts, 20% fibrin)

● LY30 - %age of clot strength loss from MA, 30 min Fibrinolysis

Desphande. PAS Meeting. 2015.Edwards. Am J Clin Pathol 2008;130:99-102.

vWF ?surgical bleeding

plasma

cryoprecipitate

platelets

aspirin/dipyramidole

TXA/Amicar

heparinoid/DTI/etc.

Protamine (? R +/- heparinase)