Bma Illustrated Medical Dictionary

in septicaemia. Microbiology also looks

for antibodies in the blood, which may

confirm immunity to an infection.

blood transfusionThe infusion of large

volumes of blood or blood products

directly into the bloodstream to remedy

severe blood loss or to correct chronic

anaemia. In an exchange transfusion,

nearly all of the recipient’s blood is

replaced by donor blood. Before a

transfusion, a sample of the recipient’s

blood is taken to identify the blood

groups, and it is matched with suitable

donor blood. The donor blood is trans-

fused into an arm vein through a plastic

cannula. Usually, each unit (about 500

ml) of blood is given over 1–4 hours; in

an emergency, 500 ml may be given in a

couple of minutes. The blood pressure,

temperature, and pulse are monitored

during the procedure.

If mismatched blood is accidentally

introduced into the circulation, anti-

bodies in the recipient’s blood may cause

donor cells to burst, leading to shockor

kidney failure. Less severe reactions can

produce fever, chills, or a rash. Reactions

can also occur as a result of an allergy

to transfused blood components. All

blood used for transfusion is carefully

screened for a number of infectious

agents, including HIV(the AIDSvirus)

and hepatitis Band hepatitis C.

In elderly or severely anaemic patients,

transfusion can overload the circulation,

leading to heart failure. In patients with

chronic anaemia who need regular trans-

fusion over many years, excess iron may

accumulate (haemosiderosis) and dam-

age organs such as the heart, liver, and

pancreas. Treatment with desferrioxamine

to remove excess iron may be needed.

blood transfusion, autologousThe

use of a person’s own blood, donated

earlier, for blood transfusion. Autolo-

gous transfusion eliminates the slight

but serious risk of contracting a serious

infectious illness from contaminated

blood. There is no risk of a transfusion

reaction occurring as a result of incom-

patibility between donor and recipient

blood. Up to 3.5 litres of blood can be

removed and stored in several sessions

at least 4 days apart and up to 3 days

before planned surgery. Blood may be

salvaged during surgery, filtered and

returned to the circulation, reducing the

need for transfusion of donated blood.

BLOOD TRANSFUSION BLOOD TRANSFUSION, AUTOLOGOUS

B

Bag of blood

Flow-rate

control

Blood enters

vein through a

plastic cannula

Nurse

monitors

blood

pressure

BLOOD TRANSFUSION

Sphygmomanometer

Stethoscope