# Presentation: 520604

## Risks and Indications for RBCs Transfusions

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

## Adverse Effects of RBC Transfusions

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

## Risk of Transfusion-Transmitted Infections

|  | 2002 USA1 | 2007 Canada2 |
| --- | --- | --- |
| HBV | 1:205,000 | 1:153,000 |
| HCV | 1:1,935,000 | 1:2,300,000 |
| HIV | 1:2,135,000 | 1:7,800,000 |
| HTLV | 1:2,993,000 | 1:4,300,000 |
|  |  |  |

**1. Dodd RY et al. Transfusion. 2002;42:975-9**
**2. O'Brien SF et al.Transfusion. 2007;47:316-25 **

## Adverse Effects of RBC Transfusions

**Other pathogens**
**Bacteria**
**Malaria**
**Chagas**
**Babesia**

## 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)**

## Adverse Effects of RBC Transfusions

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

## Transfusion Fatalities Reported to the FDA (FY 2004 to 2006)

## Function of RBCs

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

## Normovolemic Amenia

**As hematocrit falls**
**Blood viscosity decreases**
**Cardiac output increases (********Stroke volume, ******** pulse)**
**Delivery of O****2**** ******
**O****2**** extraction ******** **
**Consumption of O****2**** remains constant**

## Limits of Compensation

**At very low hemoglobin levels (approximately 4 g/dL)**
**O****2**** delivery does not meet demand**
**Anerobic metabolism ******** lactic acidosis ******** cardiac arrest**

## 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 > 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**

## Hemoglobin and Hematocrit Levels in Healthy Adults

|  | Hemoglobin (g/dL) |  | 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**

## Transfusion Trigger:Multicenter, 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. 1999;340: 409-417**

## Transfusion Trigger:Multicenter, 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. 1999;340: 409-417**

## 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. 2007:356;1609-1619**
**Moderate to severe head injury**
**7.0 g/dL vs 10.0 g/dL**
**McIntyre LA et al. Neutrocrit Care 2006;5:4-9**
**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. 2001;29:227-234.**

## Optimal Hematocrit?

**Laboratory and mathematical model**
**Maximize delivery of oxygen**
**O****2**** 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 1967;22:501-504**
**Clinical **
**Risks associated with increasing the hemoglobin/hematocrit justify the clinical benefits**

## 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**

## 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.**