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Indications for transfusion
• Blood transfusions are given to increase oxygen-
carrying capacity and intravascular volume.
• Hemoglobin value at which blood should be
given will have to be a clinical judgment
based on many factors-
cardiovascular status, age
Anticipated additional blood loss
Mixed venous oxygen tension
Cardiac output, blood volume
Oxygen extraction ratio
1. Blood loss greater than 20% of blood volume
2. Hb level less than 8 g/dL
3. Hb level less than 9 to 10 g/dL with major disease
(e.g., emphysema, ischemic heart disease)
4. Hb level of less than 10 g/dL with autologous blood
5. Hb level less than 11 to 12 g/dL and ventilator
• The transfusion point can be determined
preoperatively from the hematocrit and by
estimating blood volume
• Patients with a normal hematocrit should
generally be transfused only aft er losses
greater than 10–20% of their blood volume.
The amount of blood loss can be calculated
• 1. Estimate blood volume
• 2. Estimate the red blood cell volume (RBCV)
at the preoperative hematocrit (RBCV preop ).
• 3. Estimate RBCV at a hematocrit of 30%
(RBCV 30% ), assuming normal blood volume
• 4. Calculate the RBCV lost when the
hematocrit is 30%; RBCV lost = RBCV preop –
RBCV 30% .
• 5. Allowable blood loss = RBCV lost × 3.
• An 85-kg woman has a preoperative hematocrit of
35%. How much blood loss will decrease her hematocrit
Estimated blood volume = 65 mL/kg × 85 kg
= 5525 mL.
RBCV 35% = 5525 × 35% = 1934 mL.
RBCV 30% = 5525 × 30% = 1658 mL.
Red cell loss at 30% = 1934 − 1658 = 276 mL.
Allowable blood loss = 3 × 276 mL = 828 mL.
Therefore, transfusion should be considered
only when this patient’s blood loss exceeds 800 mL.
Increasingly, transfusions are not recommended
until the hematocrit decreases to 24% or lower
(hemoglobin <8.0 g/dL), but it is necessary to take
into account the rate of blood loss and comorbid
conditions (eg, cardiac disease, in which case transfusion
might be indicated if only 800 mL of blood
Clinical guidelines commonly used include:
(1) one unit of red blood cells
will increase hemoglobin
1 g/dL and the hematocrit 2–
3% in adults;
(2) a 10-mL/kg transfusion of
red blood cells will
concentration by 3 g/dL and
the hematocrit by 10%.
1-Changes in Oxygen Transport
Changes in Oxygen Transport RBCs are transfused
primarily to increase transport of oxygen to tissues.
An increase in the circulating red cell mass produces an
increase in oxygen uptake in the lung and a
corresponding probable increase in oxygen delivery
to tissues. The respiratory function of red cells may
be impaired during preservation, making it difficult
for them to release oxygen to the tissues
immediately after transfusion.
Unless a patient has a preoperative coagulopathy
(aspirin,antiplatelet drugs hemophilia),
A transfusion induce coagulopathy usually occurs only after a
large amount of blood has been given (6 to 10 units of PRBCs)
This coagulopathy is caused by a combination of factors, of
which the most important are the volume of blood given and
the duration of hypotension or hypo perfusion.
The patient who is hypotensive and has received many
units of blood probably has a coagulopathy from a condition
that resembles disseminated intravascular coagulation (DIC)
and dilution of coagulation factors from stored bank blood
• Clinical manifestations include oozing into the
surgical field, hematuria, gingival bleeding,
petechial bleeding from venipuncture sites, and
• 3-dilutional thrombocytopenia
• Considering survival time and viability, total
platelet activity is only 50% to 70% of the original
in vivo activity after 6 hours of storage in bank
blood at 4°c.After 24 or 48 hours of storage,
platelet activity is only about 10%or 5% of normal
• 4-Low levels of Factors V and VIII
• These factors gradually decrease to 15%and 50%
normal, respectively, after 21 days of storage
• 5-Disseminated Intravascular Coagulation-like
• 6- Citrate Intoxication and Hyperkalemia
• 7-Temperature A decrease in body temperature as
small as 0.5 to I.0°C may induce
shivering postoperatively; this may increase oxygen
consumption by as much as 400%. To meet the
demands of elevated oxygen consumption, cardiac
.output must be Increase
• Perhaps the safest and most common method
of warming blood is to pass it through plastic
coils immersed in warm water (37 to 38°C)
• 7-Acid-Base Abnormalities the pH of bank blood
continues to decrease to about 6.9 after 21 days of
• 8- Hemolytic Transfusion Reaction
• Such a reaction can occur from infusion of as little as
10 mL of blood. Between 20% and 60% of patients
with severe symptomatic hemolytic reactions may
die, and these deaths usually result from AB0 blood
group incompatibility between the donor and the
• Haptoglobin, which is a protein that can bind
about 100 mg of hemoglobin per 100 mL of
• A sample of plasma that contains 2 mg/dL of
hemoglobin is faintly pink or light brown.
When the level of hemoglobin reaches 100
mg/dL, the plasma is red. When the level of
plasma hemoglobin reaches 150 mg/dL,