Cryoprecipitate Dose for Fibrinogen Calculator
Cryoprecipitate Dose for Fibrinogen Calculator
Work out how many packs are needed to reach a target fibrinogen — for a single donation, a five-donation pool or a vial of fibrinogen concentrate, because the three differ three- to fivefold in what they contain.
Cryoprecipitate Dose for Fibrinogen
Deficit × plasma volume70 kg, haematocrit 30%, fibrinogen 0.8 g/L, target 2.0 g/L, pooled cryoprecipitate
Formula
Fibrinogen required (g) = (target − current fibrinogen, g/L) × plasma volume (L)
Packs = fibrinogen required (g) × 1,000 ÷ mg of fibrinogen per pack
- 400 mg per single donation
- the NICE NG24 full guideline quotes a mean of approximately 400 to 460 mg of fibrinogen in a single unit, and a pool is five units. Content varies widely between donations, so 400 mg is an assumption the dose inherits, not a measurement
- 2,000 mg per pooled unit
- five donations at the assumed 400 mg. NHSBT's adult therapeutic dose is two pools, or one single donation per 5 to 10 kg of body weight, and one dose is expected to raise fibrinogen by about 1 g/L
- 1,000 mg per vial of concentrate
- fibrinogen concentrate is assayed and labelled, so its content is known rather than estimated. It needs no thawing and no ABO matching, and the European trauma guideline suggests an initial dose of around 50 mg/kg
- plasma volume, not blood volume
- fibrinogen distributes in plasma, so the haematocrit has to come out. At 70 mL/kg of blood volume and a haematocrit of 0.30, a 70 kg adult has about 3.4 L of plasma — and a lower haematocrit means a larger plasma volume and a larger dose
Worked example
70 kg, haematocrit 30%, fibrinogen 0.8 g/L, target 2.0 g/L, pooled cryoprecipitate
Plasma volume = 70 × 70 mL/kg × (1 − 0.30) = 3,430 mL, which is 3.43 L
Deficit = 2.0 − 0.8 = 1.2 g/L, so 1.2 × 3.43 = 4.12 g of fibrinogen needed
At an assumed 2,000 mg per pooled unit: 4,116 ÷ 2,000 = 2.1 pooled units — issue two pools
The same deficit is about 10 single donations, or about 4 vials of fibrinogen concentrate
Two pools is the NHSBT adult therapeutic dose and is expected to raise fibrinogen by roughly 1 g/L, which is what this arithmetic reproduces — a useful check that the model and the guideline agree
Three products, three different quantities
| Product | Assumed fibrinogen per pack | Adult therapeutic dose | Practical points |
|---|---|---|---|
| Single donor cryoprecipitate unit | About 400 mg (NICE quotes a mean of 400–460 mg) | Ten units, or one unit per 5–10 kg | Content varies widely between donations. Needs thawing and cannot be split |
| Pooled cryoprecipitate unit (5 donations) | About 2,000 mg | Two pools | The standard UK issue. One dose raises fibrinogen by roughly 1 g/L. Needs thawing |
| Fibrinogen concentrate | 1,000 mg per 1 g vial, assayed | Around 50 mg/kg initially per the European trauma guideline — about 3.5 g at 70 kg | Content is known rather than assumed. No thawing, no ABO matching. Licensing for acquired deficiency varies by country |
Fibrinogen thresholds by setting
| Setting | Threshold | Where the figure comes from |
|---|---|---|
| Bleeding patient, clinically significant haemorrhage | Below 1.5 g/L | NICE NG24 |
| Before an invasive procedure, not bleeding | Below 1.0 g/L | NICE NG24 |
| Acquired deficiency with bleeding that is not severe, for example some DIC | 1.0 g/L may be more appropriate | NICE NG24 |
| Major haemorrhage, trauma | Below 1.5 g/L, maintain above it | BSH major haemorrhage guideline |
| Obstetric haemorrhage | Maintain above 2.0 g/L | A fibrinogen below 2 g/L early in a postpartum haemorrhage carries a high positive predictive value for progression to severe bleeding |
Name the product, or the dose means nothing
Fibrinogen is the first coagulation factor to fall to a critical level in major haemorrhage, and cryoprecipitate is the traditional way of replacing it. The arithmetic is straightforward: work out the plasma volume, multiply by the gap between the current and the target fibrinogen to get the grams required, then divide by the fibrinogen in one pack. The haematocrit belongs in that calculation because fibrinogen distributes in plasma rather than in whole blood, so a 70 kg adult with a haematocrit of 0.30 has about 3.4 litres of plasma to fill and an anaemic patient has more.
What the calculation cannot do without being told is convert grams into packs, because the three products in common use differ three- to fivefold. A single donor unit contains a mean of around 400 to 460 mg of fibrinogen by the NICE estimate, with wide variation between donations. A pooled unit is five donations, so roughly 2,000 mg. A vial of fibrinogen concentrate holds an assayed gram. Two pools — the NHSBT adult therapeutic dose — is about 4 g and raises fibrinogen by roughly 1 g/L in an average adult, which is the figure UK guidance quotes and the figure this model reproduces. A request for 'two units of cryo' could mean 0.8 g or 4 g, and the laboratory should not have to guess.
The trigger is not one number either. NICE gives 1.5 g/L for a bleeding patient and 1.0 g/L before an invasive procedure, and notes that 1.0 g/L may be more appropriate in acquired deficiency with bleeding that is not severe. Obstetric practice runs higher: a fibrinogen below 2 g/L early in a postpartum haemorrhage predicts progression to severe bleeding with high positive predictive value, so obstetric protocols aim to keep it above 2.0 g/L. A level of 1.8 g/L is therefore reassuring in a bleeding trauma patient and a reason to act in a postpartum one.
Two cautions on the measurement itself. Use the Clauss fibrinogen: the fibrinogen derived from the prothrombin time reagent reads unreliably at exactly the low levels that matter and should not drive replacement. And a requirement far above an adult therapeutic dose usually means fibrinogen is still being consumed rather than simply diluted, so look for continuing haemorrhage, disseminated intravascular coagulation or amniotic fluid embolism, and treat the cause alongside the replacement. Every dose here supports a clinician's prescription rather than replacing it, and blood products are given against a clinical indication, not against a number.
Frequently asked questions
How much fibrinogen is in a unit of cryoprecipitate?
The NICE NG24 full guideline quotes a mean of approximately 400 to 460 mg in a single donor unit, and a pool is five units, so roughly 2,000 mg. Content varies widely between donations, which is why the achieved rise varies and why the level should be re-measured.
What is the adult dose of cryoprecipitate?
Two pooled units, or one single donation per 5 to 10 kg of body weight, according to NHSBT and NICE. One such dose is expected to raise fibrinogen by about 1 g/L in an average adult — which is what this calculator's plasma-volume arithmetic reproduces.
What fibrinogen level should trigger cryoprecipitate?
NICE gives below 1.5 g/L in a bleeding patient and below 1.0 g/L before an invasive procedure. Obstetric haemorrhage is managed to a higher target: a fibrinogen below 2 g/L early in a postpartum haemorrhage strongly predicts progression to severe bleeding.
Is fibrinogen concentrate the same as cryoprecipitate?
No. Fibrinogen concentrate has an assayed, labelled fibrinogen content, needs no thawing and needs no ABO matching, whereas cryoprecipitate's content is variable and it must be thawed. Licensing for acquired hypofibrinogenaemia differs between countries, so check local availability.
Which fibrinogen assay should be used to guide the dose?
The Clauss method. A fibrinogen derived from the prothrombin time reagent is unreliable at the low levels that actually drive replacement and can read substantially higher than the true value, which risks withholding a dose that is needed.
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References
- National Institute for Health and Care Excellence. Blood Transfusion. NICE guideline NG24; 2015.
- Nascimento B, Goodnough LT, Levy JH. Cryoprecipitate therapy. Br J Anaesth. 2014;113(6):922–934.
- Charbit B, Mandelbrot L, Samain E, et al. The decrease of fibrinogen is an early predictor of the severity of postpartum haemorrhage. J Thromb Haemost. 2007;5(2):266–273.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.