Risks and Indications for RBCs Transfusions

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Risks and Indications for RBCs Transfusions

• David Stroncek, MD
  Chief, Laboratory Services Section Department of
  Transfusion Medicine, Clinical Center, NIH,
  Bethesda, Maryland

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Adverse Effects of RBC Transfusions

• Viral Infections
• Hepatitis B
• Hepatitis C
• HIV
• HTLV I and II
• West Nile Virus
• CMV

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Risk of Transfusion-Transmitted Infections
2002 USA1 2007 Canada2
HBV 1205,000 1153,000
HCV 11,935,000 12,300,000
HIV 12,135,000 17,800,000
HTLV 12,993,000 14,300,000

1. Dodd RY et al. Transfusion. 200242975-9 2.
O'Brien SF et al.Transfusion. 200747316-25
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Adverse Effects of RBC Transfusions

• Other pathogens
• Bacteria
• Malaria
• Chagas
• Babesia

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Adverse Effects of RBC Transfusions

• Hemolytic Transfusion Reactions
• ABO (wrong unit of blood)
• Antibodies to other RBC antigens (delayed
  hemolytic transfusion reactions)
• Leukocyte antibody mediated problems
• Alloimmunization (refractory to platelet
  transfusions)
• Febrile reactions (antibody in transfusion
  recipient)
• Transfusion related acute lung injury (TRALI)
  (antibody in blood donor)

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Adverse Effects of RBC Transfusions

• Other
• Fluid overload
• Anaphylaxis
• Urticaria
• GVHD
• Immune modulation

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Transfusion Fatalities Reported to the FDA (FY
2004 to 2006)
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Function of RBCs

• Oxygen Transport
• Delivery of oxygen from lungs to tissues
• Oxygen transport is dependent on
• Hematocrit
• Cardiac output
• Oxygen extraction

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Normovolemic Amenia

• As hematocrit falls
• Blood viscosity decreases
• Cardiac output increases (?Stroke volume, ?
  pulse)
• Delivery of O2 ?
• O2 extraction ?
• Consumption of O2 remains constant

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Limits of Compensation

• At very low hemoglobin levels (approximately 4
  g/dL)
• O2 delivery does not meet demand
• Anerobic metabolism ? lactic acidosis ? cardiac
  arrest

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Indications for RBC transfusions

• 1940s
• Recommended that surgery patients have a
  hemoglobin of 8 to 10 g/dL
• Led to a general rule of hemoglobin gt 10 g/dL of
  surgery patients
• 1980s
• Development of invasive monitoring techniques
  lead to a better understanding of oxygen delivery
  and consumption
• Lower hemoglobin levels could be tolerated

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Hemoglobin and Hematocrit Levels in Healthy Adults
Hemoglobin (g/dL) Hemoglobin (g/dL) Hematocrit () Hematocrit ()
Mean -2SD Mean -2SD
Female 14.0 12.0 41 36
Male 15.5 13.5 47 41
Hematology Basic Principles and Practice.
Elsevier 2005
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Transfusion TriggerMulticenter, Randomized
Control Study of ICU Patients
Transfusion Strategy Hb Trigger Maintenance Level
Conservative 7.0 g/dL 7.0 to 9.0 g/dL
Liberal 10.0 g/dL 10.0 to 12.0 g/dL
Herbert PC et al. N Engl J Med. 1999340 409-417
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Transfusion TriggerMulticenter, Randomized
Control Study of ICU Patients
30-day mortality P
Restrictive 18.7 0.11
Liberal 23.3
Less acutely ill 30-day mortality P
Restrictive 8.7 0.03
Liberal 16.1
Cardiac disease patient 30-day mortality P
Restrictive 20.5 0.69
Liberal 22.9
Herbert PC et al. N Engl J Med. 1999340 409-417
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Restrictive vs Liberal Transfusion in Other
Conditions

• No difference
• Pediatric ICU patients
• 7.0 g/dL vs 9.5 g/dL
• Lacroix J, et al. N Engl J Med.
  20073561609-1619
• Moderate to severe head injury
• 7.0 g/dL vs 10.0 g/dL
• McIntyre LA et al. Neutrocrit Care 200654-9
• Possible difference
• Cardiovascular disease
• 7.0 g/dL vs 10.0 g/dL
• Liberal transfusions may be better in patients
  with acute myocardial infarction and unstable
  angina
• Hebert PC et al. Crit Care Med. 200129227-234.

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Optimal Hematocrit?

• Laboratory and mathematical model
• Maximize delivery of oxygen
• O2 delivery is proportional to hematocrit and
  blood flow rate.
• As hematocrit increases viscosity increases and
  flow rate decrease
• Optimal hematocrit is approximately 35
• Crowell JW and Smith EE. J Appl Physiol
  196722501-504
• Clinical
• Risks associated with increasing the
  hemoglobin/hematocrit justify the clinical
  benefits

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Conclusions

• Although RBCs are much safer than 20 years ago,
  transfusion practices have become more
  restrictive
• The transfusion threshold at most institutions is
  a hemoglobin of 7 to 8 g/dL for most patients
• Higher thresholds are used for specific patients

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Disclaimer

• The views expressed are those of the presenter
  and do not necessarily represent the position of
  the National Institutes of Health or the
  Department of Health and Human Services.