The Basics
Both hemophilia A and B are X-linked recessive diseases. Hemophilia A is characterized by factor VIII deficiency. 45-70% of cases can have severe bleeding. Hemophilia B is caused by factor IX deficiency, and 70% of cases have only mild bleeding. 1 Almost 30% of patients with severe hemophilia A and 3-5% of patients with severe hemophilia B will develop Inhibitors (neutralizing alloantibodies) and will require specific treatments.2 The incidence of inhibitors is affected by both the environment, such as factor replacement given in the past, as well as genetics.
| Factor Levels | Typical Presentation |
| >5% | Rarely have significant bleeding. Majority of problems occur with severe injury, procedures, or surgery |
| 1-5% | May bleed with minor injuries but rarely have spontaneous bleeding (i.e. hemarthrosis) |
| <1% | At risk for severe bleeding and significant bruising or bleeding from trivial trauma. May have significant bleeding from mucosal membranes. Prone to spontaneous hemarthrosis. |
Factor Replacement and More
The degree of factor replacement indicated varies based on clinical scenario. For reference, normal clotting levels are 50-100%.
| Bleeding Severity | Target factor VIII or IX activity |
| MILD (e.g. minor trauma, hemarthrosis) | 30-40% |
| MODERATE (e.g. oral or mucosal hemorrhages, epistaxis) or for prophylaxis for surgical/dental procedure | 50-80% |
| SEVERE (e.g. severe trauma, especially to head, neck, abdomen) | 80-100% |
How Is Hemophilia Treated?
- If a patient has a suspected bleed, give replacement factor first, and then perform tests second.
- Try to correct the level of circulating factor as soon as possible. Most families will present with their own supply/formulation of factor from home that has been prescribed for their child… USE IT! Factors are extremely expensive and can be hard to get from the pharmacy in a reasonable amount of time.
Hemophilia A
- Factor VIII: 1 U/kg increases the plasma level by 2%3
- 25 U/kg = 50% correction (for minor bleeds)
- 50 U/kg = 100% correction (for major bleeds)
- 3 types of factor replacements4
- Recombinant: Non-human product
- Purified: Only factor VIII, obtained from human product
- Intermediate purity: Human product which also contains vWF
- Desmopressin: Only works for minor bleeds and only in those with mild hemophilia
- Aminocaproic Acid (Amicar) or Tranexamic Acid: Anti-fibrinolytics that help to stabilize clot formation5,6
- Should only be used for mucosal bleeds and NEVER in patients with renal bleeds or renal insufficiency.
- Controversial: If you have no recombinant or purified human factor, you can use cryoprecipitate, which contains both vWF and factor VIII along with fibrinogen and factor XIII, or fresh frozen plasma (FFP), which contains all clotting factors. Be aware that with these agents there is concern with volume overload, safety of use, and difficulty with achieving hemostasis.
Hemophilia B
- Factor IX: 1 U/kg increases the plasma Factor IX level by 1%3
- 50 U/kg = 50% correction (for minor bleeds)
- 100 U/kg = 100% correction (for severe bleeds)
- Recombinant and purified factors are available4
- Aminocaproic Acid (Amicar) or Tranexamic Acid: Same as in Hemophilia A
- Controversial: Using FFP. It contains all clotting factors including Factor IX. Again, factor concentrates, bypassing agents, and purified plasma products are preferred by national guidelines. Cryoprecipitate has no utility in Factor IX deficiency.
Patients with Inhibitors
- NovoSeven (recombinant factor VIIa) is a bypassing agent, whereby it “bypasses” the inhibitors.
- Dose: 90-150 mcg/kg
- Has a short half-life and may require multiple subsequent doses
- FEIBA (factor eight inhibitor bypassing agent) is a plasma-derived bypassing agent.
- Dose: 50 U/kg
- Caution: Must be given slowly, because rapid infusion can cause excessive clotting (e.g. stroke).
Take Home Points
Having a patient with hemophilia who is bleeding can be a frightening thing, but just remember a couple of basics:
- Use the factor that the patient or family has. It will save time and may be the only factor that works for the patient with inhibitors. Due to cost, use the closest vial size to the recommended dose and use the whole vial. Do not waste the factor.
- Ask the parents questions. They usually know A LOT about their child’s illness and can give you a good amount of information.
- Remember to aim for 100% correction for severe bleeds. That means 50 U/kg of factor VIII and 100 U/kg of factor IX.
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