Bruce Cartwright: Blood Conservation

BLOOD CONSERVATION Bruce Cartwright Royal Prince Alfred Hospital

Status quo? • Cardiac surgery consumes 15-20% of blood product

supply •  RBC transfusion rate 5-80%; platelets up to 40%

• Up to 20% of cardiac surgical patients have a preoperatively identified risk factor for bleeding

• Around 5% of patients return to the OR for investigation of bleeding •  “Microvascular coagulopathy” is diagnosed in >50%

The cardiac dilemma • Don’t transfuse

•  Re-exploration for bleeding increases morbidity and mortality up to 3 to 4 times

•  Acute bleeding causes haemorrhagic shock, tamponade and cardiac decompensation

•  Return to ICU after re-exploration is associated with higher rates of infective complications, arrhythmias and prolonged pulmonary support and complications

• Do transfuse •  Risk especially with platelets •  TRALI, allergy, allommunisation, GVHD, renal failure, volume

overload (TACO), immunosuppresion/immunomodulation •  Increasing COST

Normal perioperative course

Normal cardiac course HAEMODILUTION ACTIVATION CONSUMPTION CPB Prime - crystalloids/colloids

Contact Activation -  XIIa, kallikrein and

bradykinin

Thrombin and Plasmin mediated

Cardioplegia Tissue factor activation -  Tissue injury -  Monocyte related -  Pericardial blood

Inflammation mediated -  Elastase -  Complement -  Leukocyte-platelet

complexes Cell Salvage - Loss of platelets and coagulation factors

Activation of fibrinolysis -  Increased tPA via

endothelial cells and pericardial cavity

-  Intrinsic activation -  Heparin and

protamine effects

Mechanical (ECC) -  Oxygenator -  Cardiotomy suction

and vents -  Filters -  Centrifugal and roller

pumps

Coating the Circuit

Edmunds, L. H. (2004). Cardiopulmonary bypass after 50 years. New England Journal of Medicine, 351(16), 1603–1606

What do we do to address this? Key components

• Attentive preoperative assessment • Surgical approaches to limit periop bleeding • Strategies to limit haemodilution, activation and

consumption associated with extracorporeal circulation • Systemic and topical pharmacological agents • Point of care testing to target blood product therapy and

recently use of factor concentrates • Post operative fluid management and transfusion

thresholds to limit unnecessary blood product use

Preoperative assessment • Current Strategies

•  identification of at-risk patients •  cessation of over the counter supplements and all herbal remedies •  timing of surgery with clopidogrel cessation according to platelet

aggregometry threshold •  investigation of preoperative anaemia

• Considerations for the future: •  screening for anaemia in preop clinic with subsequent

administration of IV iron +/- erythropoietin

Surgical Strategies •  IMA bed haemostasis prior to retractor removal •  immediate bandaging of vein harvest sites •  attention to sternum, ITA bed, pericardial edges and aortic

adventitia prior to sternal closure •  topical haemostatic agents •  topical tranexamic acid on pericardium prior to closure •  cell salvage especially for OPCAB and redo sternotomy •  stratification to OPCAB where antiplatelet therapy

inappropriate for cessation if possible

Perioperative Perfusion Strategies •  Current strategies

•  Pre bypass fluid limited to 500ml crystalloid •  Retrograde autologous priming in all patients •  Transfusion trigger based on DO2i rather than Haematocrit alone

together with supportive evidence of VCO2i, SvO2, lactate and adequacy of regional circulation where available such as NIRS

•  Normovolaemic haemodilution in selected cases •  Shear force and blood air interface management: pump sucker

activated only on demand, minimisation of air entrainment into vents

•  Future considerations •  biocompatible circuits, heparin alternatives, platelet anaesthesia •  quarantining of cardiotomy blood •  modified ultrafiltration

Systemic pharmacological agents Current practise •  Tranexamic acid • No routine use of starch solutions Future directions • Aprotinin returns? • Cangrelor platelet anaesthesia • Direct thrombin vs indirect thrombin inhibition

Point of Care Testing Multifaceted approach • Viscoelastic testing

•  Need to utilise full capacity of technology •  Rapid TEG, heparinase TEG, functional fibrinogen, platelet

mapping where appropriate •  ROTEM: ExTEM, FIbTEM, InTEM, hepTEM, ApTEM

• Platelet aggregometry •  Multiple electrode aggregometry (Multiplate)

• Activated Clotting time •  low range vs high range, heparinase

• Prothrombin complex assessment •  Coagucheck with Quick estimation

• Rapid turnover platelet count and fibrinogen level

Post operative management • Crystalloid resuscitation in preference to HES & 4%

Albumex •  no fluid challenge use for treatment of isolated low CVP or

low urine output where all other signs point to adequate cardiac output

•  no empiric blood product transfusion •  red cell transfusion trigger: Hb <70 unless evidence of

cardiogenic shock, severe vasoplegia or end organ dysfunction

•  protamine where heparin rebound has been documented •  early take back where point of care testing rules out

microvascular coagulopathy

Results • All case transfusion rate: steady fall from 65% to 35%

0

10

20

30

40

50

60

70

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Results – average usage

0

0.5

1

1.5

2

2.5

3

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Red Blood Cells

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Platelets

0

0.5

1

1.5

2

2.5

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Fresh Frozen Plasma

0 0.5

1 1.5

2 2.5

3 3.5

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Cryoprecipitate

Results – cost reductions

0.00

0.02

0.04

0.06

0.08

0.10

0.12

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Activated Factor 7

$0

$500

$1,000

$1,500

$2,000

$2,500

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Total cost per patient

$0

$200,000

$400,000

$600,000

$800,000

$1,000,000

$1,200,000

$1,400,000

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

At 600 per year

Elective Coronary Surgery

0

10

20

30

40

50

60

70

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Elective Surgery – other benefits

•  average decrease in 4 hour blood loss of 31% •  reductions in ICU length of day by 25 hours when not

transfused (vs transfused) •  reduction in length of hospital stay by 1 day when not

transfused

Current Challenges

0

10

20

30

40

50

60

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Non Elective Coronary

0 10 20 30 40 50 60 70 80 90

Q1 Q2 Q3 Q4 Q5 Q6 Q7 Q8 Q9

Aortic Surgery

Future directions • Preoperative Fe +/- EPO • Circuit Modifications

•  biocompatible circuits, heparin alternatives, platelet anaesthesia •  quarantining of cardiotomy blood, MECC •  modified ultrafiltration

• Aprotinin or alternatives •  Integrated electronic data collection •  Tranfusion trigger assessment • Refining POC algorithms • State/Nationwide/International colloboration •  Factor Concentrates