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P.O. Box 3003
Dryden, ON P8N 2Z6
Phone: (807) 223-8264
Fax : (807) 223-7342
e-mail: [email protected]
Newsletter
2007-04
Red Cell Transfusions
Introduction: Red cell transfusion remains an important and most frequent part of blood component
therapy in adult and pediatric, medical and surgical patients. Understanding its uses and alternatives
will contribute to optimal patient care and minimization of health care costs.
A unit of packed red cells (RBC) comes from a unit of whole blood that has been separated into blood
components by centrifugation. One unit of packed RBC increases the hemoglobin by 10g/L and the
hematocrit by .03 in a normal adult.
Indications:
Treatment of Acute Anemia: Patients who have suddenly lost more than 20 to 30% of their blood
volume develop symptoms of anemia in spite of compensatory mechanisms. Hemodilution begins
almost immediately after the onset of hemorrhage and continues up to 72 h after cessation of
bleeding. Although this influx of fluid does not improve oxygen carrying capacity, it does help to
maintain blood volume and stabilize circulation.
The primary therapy for acute hemorrhage is volume replacement with a crystalloid, because the
treatment of or prevention of hypovolemic shock is more urgent than restoration of oxygen carrying
capacity. Colloids are no more advantageous physiologically than crystalloid during early resuscitation
and are more expensive. Furthermore, reference literature suggests a significant increase in the risk of
death with the use of albumin compared to crystalloid.
If symptoms persist after volume repletion, red cell transfusion should be considered. Transfusion of
RBCs increases oxygen delivery in patients who have symptomatic anemia although this capacity of O2
delivery to tissue lags behind the rise of Hgb/Hct.
In clinical practice the hemoglobin/ hematocrit level is the most common indicator used for the need
for red cell transfusion. It is important to note that these indicators estimate the oxygen carrying
capacity and do not assess tissue oxygenation. Physiological/chemical monitoring and lactate are
further useful indicators.
Newsletter
2007-04
Numerous publications have debated the risks and benefits of using hemoglobin levels between 60 and
100 g/L as a transfusion trigger for patients with acute blood loss. Generally, most isovolemic patient
with a hemoglobin < 70g/L may benefit from transfusion, while most patients with a hemoglobin > 10
g/L will not.
Indications for red cell transfusion to correct acute anemia include:
1)
Hemoglobin < 70 g/L in a symptomatic individual without premorbid conditions
2)
Hemoglobin < 90g/L in patients at increased risk from bleeding. These include:
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Elderly patients >65 years old
Patients with heart disease
Patients with cerebrovascular disease.
Patients with pulmonary disease
Treatment of Chronic Anemia:
Reversible causes of chronic anemia such as vitamin B12, folate,
and iron deficiency should be ruled out prior to transfusion. Only then should RBCs be transfused to
alleviate the symptoms of anemia and reduce morbidity associated with a patient's underlying disease.
Chronic anemia patients undergo compensatory changes that adapt them to lower hemoglobin levels.
A point of fundamental importance is that blood volume is little changed in patients with chronic
anemia due to compensatory increases in plasma volume. Thus, transfusion of chronically anemic
patients regularly causes hypervolemia which has the potential for precipitating cardiac
decompensation, particularly in elderly patients or in patients with known heart failure. Increased
circulatory volume is one of the most common adverse effects of transfusion.
The hemoglobin trigger level may be 70 g/L (hematocrit of .210) in individuals with chronic anemia
without symptoms. Transfusion will improve functional status in symptomatic patients up to a
hemoglobin level of 100 g/L. Transfusions beyond this level provide no further improvement in
functional status in most patients. This is especially true for patients with impaired cardiac output
because their inability to compensate for increased blood viscosity can actually decrease tissue
oxygenation. The major exception is patients with severe chronic obstructive pulmonary disease
(COPD) who may still be symptomatic at hemoglobin levels of 100 g/L and require a hemoglobin level
between 100 and 120g/L to alleviate symptoms.
Transfusion in Surgery:
Red cell transfusion is indicated during surgery when active bleeding
causes a blood loss of 10-15% or more of the patient's blood volume. In addition acute blood loss may
cause the blood pressure to drop by 20% or to a level of < 100 mm Hg, or if the pulse increases to
>100/min signifying hemodynamic instability.
The transfusion of colloid and/or crystalloid solutions is also indicated in bleeding patients to maintain
adequate blood volume. Indeed, as long as normovolemia is maintained with colloid and/or crystalloid
solutions and the patient's hemoglobin level is adequate, it is not necessary to replace all losses of red
cells.
Newsletter
2007-04
Red cell transfusion has often been used empirically prior to general anesthesia when the hemoglobin
is less than 90 or 100 g/L. There are no data that strongly support this practice. The key to tolerance
of anemia is the maintenance of normovolemia and compensatory mechanisms that increase cardiac
output and improve oxygen transport.
Postoperative hemoglobin in the range of 80-90 g/L appears to be safe for patients free of
cardiovascular disease, and justification should be provided and documented if blood is transfused
other than to replace losses at this level.
The indications for red cell transfusion perioperatively include:
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Preoperative Hb < 80 g/L in an otherwise healthy individual undergoing surgery associated
with anticipated blood loss >1000 mL
Preoperative Hb < 100 g/L in a patient at increased risk from bleeding
Intraoperative patients with unstable vital signs
Surgical blood loss >1000 ml
Follow up measurement of the recipient's hemoglobin and/or hematocrit can be performed between 15
min and 24 hours post-transfusion. The earliest time interval for assessment is 15 minutes following a
completed transfusion. Hemoglobin levels obtained at 24 hours post-transfusion are 10% higher than
values obtained after 15 minutes in the absence of further blood loss or excessive plasma volume
expansion.
Transfusion in the Setting of Angina:
Angina may be indicative of an impending myocardial
infarction. Indications for transfusion of patients with myocardial infarction are unclear.
Transfusion may improve myocardial oxygen delivery, but may also increase myocardial oxygen
consumption secondary to increased blood volume and blood viscosity. The decision to transfuse should
be based on critical patient evaluation and internal hemodynamic pressure monitoring.
References:
1. Transfusion Medicine Update. Institute for Transfusion Medicine. 1997. www.itxm.org
2. Red Blood Cell Transfusion Clinical Laboratory Navigator. 2006
www.clinlabnavigator.com/transfusion
Dr. MacDonald would be pleased to discuss these guidelines with you at his next onsite visit.
We’d like to hear from you!!
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Let us know by contacting your Laboratory Manager or,
Anna Robinson
Kenora-Rainy River Regional Laboratory Program, Inc.
Phone: 807-223-8264 Fax: 807-223-7342
e-mail: [email protected]