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BACTERIALLY CONTAMINATED BLOOD

Bacterially contaminated blood
Transfusion of bacterially contaminated blood can cause fever, shock, collapse and death.

Blood most commonly becomes bacterially contaminated at the time it is collected when the venepuncture site is not
cleansed sufficiently or when a non-sterile blood collection set or blood collecting bag is used.

Blood must always be examined for signs of contamination at the time of use, i.e. when collected from the blood bank and at the patient’s bedside.

When grossly contaminated, blood appears haemolyzed and dark in colour. Some bacteria also cause clotting.

Bacteria which commonly contaminate blood are able to multiply in refrigerated blood.

HEALTH CHECK BEFORE DONATING BLOOD

● Basic physical examination: To include a check for swollen glands, skin rashes, signs of intravenous drug use or abnormal bleeding (purpura).

● Weight of the person: Persons weighing 45–50 kg or more can safely donate 450 ml of blood.

● Temperature of the person (to exclude any febrile disease e.g. malaria): A donor should not give blood when their temperature is raised.

● Measurement of blood pressure: A donor should not have an abnormally low blood pressure nor a high blood pressure. The upper acceptable limits are a diastolic pressure of 100 mm Hg and systolic pressure of 180 mm Hg. The minimum acceptable blood pressure is 90/50 mm Hg.

● Pulse rate of the person: The pulse rate should be regular and less than 100 beats/minute (counting for at least 30 seconds).

● Test to check for anaemia: For example, measurement of haemoglobin or PCV or an estimate of haemoglobin level using the Haemoglobin Colour Scale. In most countries persons are accepted as blood donors with a haemoglobin of 120 g/l (12 g/dl) or more and haematocrit of 380 g/l (38%) or more. In some countries the lower limit for men is set at 130 g/l (13 g/dl). Higher haemoglobin levels will be
required at high altitudes.

OBJECTIVES OF QUALITY ASSURANCE (QA) IN BLOOD TRANSFUSION

• To prevent unnecessary blood transfusions.

● To provide blood that is consistently safe and effective, traceable, and available when it is needed.

● To obtain blood from low risk healthy donors and promote non-remunerated voluntary blood donation.

● To ensure appropriate tests and controls are used to screen blood for transfusion transmissible pathogens, and to type (group) and compatibility test blood.

● To minimize errors by implementing concise easy to follow standard operating procedures (SOPs) and monitoring staff compliance.

● To prevent patient misidentification and errors in blood labelling, documentation, and blood records.

● To ensure personnel are well motivated and trained to the standard required with sufficient on-site experience and continuing education to perform blood transfusion related techniques competently and safely

BLOOD TRANSFUSION IN VARIOUS CASES

TREATMENT OF ANAEMIA

For adults, including pregnant women, blood transfusion is indicated when:

A patient is in danger of dying of anaemic heart failure or hypoxia before specific medication can raise the haemoglobin.
Obstetric delivery is imminent and the mother’s haemoglobin is below 70 g/l (7 g/dl).
Emergency major surgery is essential and the haemoglobin is below 80 g/l (8 g/dl) with an anticipated blood loss of more than 500 ml.

In the above situations, the use of concentrated red cells (10 ml/kg body weight), is indicated to avoid cardiac overload. The transfusion should be administered slowly over 4–6 hours. When indicated, a rapidly acting diuretic should be administered. The pulse and respiratory rate should be monitored and the chest examined to detect volume overload.

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For infants and young children, blood transfusion is indicated when:

The haemoglobin is below 50 g/l (5.0 g/dl) and is associated with respiratory distress.
The haemoglobin is below 40 g/l (4.0 g/dl) and is complicated by malaria or bacterial infection even without respiratory distress.
The haemoglobin is below 30 g/l (3.0 g/dl) without apparent infection or respiratory distress.

In the above situations, transfusion with whole blood (not packed cells), 10 ml/kg body weight, without diruretics will be tolerated.
Children with respiratory distress but not profound anaemia should be treated with intravenous colloids, and be transfused only if the haemoglobin falls later to less than 50 g/l.

TREATMENT OF ACUTE HAEMORRHAGE

● Blood transfusion is indicated when there is acute haemorrhage with a loss of more than 30% of apatient’s total blood volume, and blood pressure and oxygenation cannot be maintained by crystalloid solutions (saline or Ringers’ lactate) or colloids (e.g. 5% dextran or 5% hydroxyethylstarch).

Acute blood loss should be managed by
replacement of volume. Only when shock
persists or worsens should whole blood be transfused.

Postpartum haemorrhage: Blood transfusion is indicated when hypotension and reduced cerebral function persist
after at least 50 ml/kg of volume replacement fluid has been given intravenously and all measures have been
taken to stop blood loss.

TREATMENT OF NEONATAL JAUNDICE

For newborn infants with a serum bilirubin above 300 µmol/l, an exchange blood transfusion is indicated.

HYPOGLYCAEMIA

A low blood glucose level is called hypoglycaemia. Persistent occurrences of hypoglycaemia with glucose levels less than 2.2 mmol/l accompanied by
symptoms such as fainting, fits, sweating, hunger, pallor, confusion, or violence, should be investigated. Causes of hypoglycaemia include severe malnutrition, kwashiorkor, severe liver disease, alcoholic excess, insulin secreting tumours, Addison’s disease, and certain drugs. Commonly, however, markedly
reduced blood glucose levels occur following the overtreatment of diabetes.

Neonatal hypoglycaemia

Newborn infants may suffer hypoglycaemia when blood glucose levels fall below 1.1 mmol/l. Infants particularly at risk are
underweight poorly nourished babies, twins, premature infants, and babies born of diabetic mothers. It is important to detect hypoglycaemia of the newborn because without treatment brain damage may
occur.

Malaria associated hypoglycaemia

In severe malaria, hypoglycaemia is a common finding and can increase mortality particularly in young children.
Hypoglycaemia can also occur in those being treated with quinine and quinidine.

False glucose values

A falsely high glucose level will result if a blood sample is collected from an arm receiving a glucose (dextrose) intravenous
(i.v.) infusion. A falsely low value may be obtained if the plasma is markedly icteric.

See also:

HYPERGLYCEMIA

A raised blood glucose level is called hyperglycaemia. When definite it is diagnostic of diabetes mellitus. In an adult with symptoms of diabetes mellitus, a random venous plasma glucose of 11.1 mmol/l or more on two occasions or a fasting value of 7.0 mmol/l or more on two
occasions is diagnostic.

Hyperglycemia occurs in pancreatic disease and some endocrine disorders such as thyrotoxicosis
Cushings syndrome.
Steroid therapy may also cause hyperglycaemia.
Transient hyperglycaemia often occurs following severe stress, e.g. after surgery, injury, shock, infections, or severe burns.

These are essentially forms of transient diabetes (e.g. “stress diabetes”, “steroid diabetes”). However, it is now recognized that a number of these patients
may have pre-existing type 2 diabetes, therefore it is important to check that hyperglycaemia does resolve when the intercurrent illness resolve.

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PREPARATION OF GLUCOSE CALIBRATION GRAPH

1. Take six tubes and label them ‘B’ (reagent blank) and 1 to 5. Pipette 1.5 ml of protein precipitant reagent into each tube. Note: The use of the protein precipitant reagent is required because it forms part of the buffer system and contains phenol which is needed for the colour reaction.

Add to each tube as follows:

Tube

B …………………….. 0.05 ml distilled water

1 ……………………. 0.05ml standard, 2.5 mmol/l

2 ……………………..0.05ml standard, 5 mmol/l

3 ……………………..0.05ml standard, 10 mmol/l

4 ………………………0.05ml standard, 20 mmol/l

5 ……………………..0.05ml standard, 25 mmol/l

3. Continue as described in steps 5 to 7 of the glucose method.

4. Take a sheet of graph paper and plot the absorbance of each standard (vertical axis) against its concentration in mmol/l (horizontal axis). A linear calibration should be obtained.

The useful working limit (linearity) of the glucose oxidase method is about 25 mmol/l.

Check the calibration graph by measuring a control serum. A new calibration graph should be prepared and checked against controls whenever stock reagents are renewed.

GLUCOSE

Glucose provides the energy for life processes. It is the main end product of carbohydrate digestion.

Oxidation of glucose by the glycolytic and tricarboxylic acid pathways provides the chemical energy needed for cellular activity.

When not required for the body’s immediate energy needs, glucose
is converted to glycogen and stored in the liver and muscles (glycogenesis).

When required to maintain the blood glucose level, liver glycogen is converted back to glucose (glycogenolysis).

Muscle glycogen provides the glucose for muscular activity. Excess glucose is oxidized to fatty acids and stored as fat in the tissues. If needed, glucose can also be formed from fats and protein (gluconeogenesis).

An increase in the breakdown of fats to provide energy, results in an increase in the
production of ketones.

Insulin is the most important hormone that regulates the amount of glucose in the blood, the rate at which glucose is
taken up by the tissues, and the conversion of glucose to glycogen. It is made and secreted by the beta-islet cells of the
pancreas. Only insulin is capable of reducing the concentration of glucose in the blood.

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D-DIMER AND FIBRINOLYTIC SYSTEM

Fibrinolysis is the enzymatic process used by the body to remove a fibrin thrombus to restore normal blood flow once damaged endothelium is repaired.
During the clotting process, tissue plasminogen activator (t-PA) released from the blood vessel wall and the plasma proenzyme plasminogen bind to the fibrin thrombus. When activated, plasminogen is converted to plasmin which degrades the
fibrin network, causing the clot to dissolve. During this process, fibrin degradation products (FDPs), i.e. fragments called D-Dimers are produced.

Raised FDP levels in DIC

In Disseminated intravascular coagulation (DIC), activated procoagulants are released into the circulation. Platelets and coagulation factors are consumed and fibrin is deposited in small vessels, activating the fibrinolytic system. The plasmin formed degrades the fibrin (also some fibrinogen), resulting in a build-up of FDPs in the circulation. The FDPs act as anticoagulants interfering with platelet function and fibrin stabilization.
Laboratory tests are available to semi-quantify D-DIMER in plasma.

THROMBIN TIME (TT) TEST PROCEDURE

(Courtesy of Diagen Thrombin Test Time Kit. Test )

Test the patient’s plasma and
control plasma in duplicate.

Pipette 200 l (0.2 ml) of plasma into a small glass tube. Incubate at 37°C for 1–2 minutes.
Add (0.1 ml) of thrombin, mix and start the stop-watch. Hold the tube in the water bath and tilt the mixture back and forth, looking for clot formation. When a clot forms, stop the stopwatch and record the time in seconds.
Report the patient’s TT (average of the duplicate tests) providing the TT of the control plasma is satisfactory.

What are the normal ranges for TT?

12–15 seconds

What are causes of prolonged TT?

DIC and other conditions which produce a low fibrinogen level
Abnormal fibrinogen
Treatment with heparin
Liver failure
Presence of inhibitors of thrombin such as FDPs

See also:

TT test principle