- Kunle Emmanuel
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- Joined: Mon Jan 09, 2012 5:02 pm
- Location: Lagos
Massive blood transfusion (MBT) is arbitrarily defined as the replacement of a patient's total blood volume in less than 24 hours, or as the acute administration of more than half the patient's estimated blood volume per hour.
One of the major complications of MASSIVE BLOOD TRANSFUSION is HYPOCALCEMIA.
Each unit of blood contains approximately 3g of citrate (the anticoagulant in the blood bag that helps to prevent clotting of stored blood and blood products). Citrate chelates (binds to) ionic calcium to form a complex thus reducing the calcium level in the blood, a condition referred to as HYPOCALCEMIA.
The normal adult liver metabolizes 3g of citrate every 5 minute. This helps to clear up citrate from the blood. But in critically ill patients and in patients with impaired or compromised liver function, citrate accumulates in the body, causing citrate toxicity and hypocalcaemia. Hypothermia is another factor that can reduce the rate at which citrate is metabolized from the body.
Calcium is an important co-factor, especially in coagulation, and has a key role in mediating the contractility of myocardial, skeletal and smooth muscles. Hypocalcaemia results in hypotension, small pulse pressure, flat ST-segments and prolonged QT intervals on the ECG.
If there is clinical, biochemical or ECG evidence of hypocalcaemia, it should be treated with 5-10ml intravenous injection of calcium gluconate 10% given slowly over 3-5min.
Normal range of calcium in the blood: 8.5-10.5 mg/dl.
_To convert mmol/L to mg/dl, multiply by 18._
_To convert from mg/dl to mmol/L, divide by 18.
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