This case highlighted a number of important issues:
1) The differential diagnosis of thrombocytopenia associated with pregnancy
Working out why a pregnant or post partum patient is thrombocytopenic can be difficult. A number of conditions can cause thrombocytopenia to a certain degree. Looking through this table can help, however it is common for patients to have features of a number of these conditions and correlating with the clinical features and which laboratory phenomena are most obvious is important.
(table from BCSH TTP guideline)
2) Appropriate transfusion of red cells
Transfusion in pregnancy and post partum is an important issue. Although red cell transfusion is relatively safe it still has risks involved, which include allergic reactions, haemolytic reactions, transfusion-related lung injury and wrong blood or component transfused due to human error. In major obstetric haemorrhage the role of transfusion is clear, however in stable asymtommatic anaemia it is contraindicated. Our patient was iron deficient during her pregnancy and this should have been corrected prior to delivery. Current guidelines suggest that anaemic women should receive a trial of iron in order to demonstrate iron deficiency (whilst simultaneously checking ferritin). 100-200mg of elemental iron should be taken and women should be encouraged to also increase vitamin C in their diet to increase absorption. Prolonged release preparations and co-administration of PPI should be avoided.
If there is significant anaemia, patients can’t tolerate oral iron or a rise is needed quicker then patients should be reviewed in a hospital setting and consideration should be made for intravenous preparations. All attempts should be made to reduce red cell usage by managing anaemic patients in the appropriate settings, avoiding further blood loss, use of cell salvage and correcting coagulopathies. Women of child-bearing age are a risk of developing antibodies to red cell antigens which could complicate future pregnancies.
Patient Blood Management is a multidisciplinary, evidence-based approach to optimising the care of patients who might need blood transfusion. Patient Blood Management puts the patient at the heart of decisions made about blood transfusion to ensure they receive the best treatment and avoidable, inappropriate use of blood and blood components is reduced.
3) Introduction to post transfusion purpura (PTP)
This is a rare complication of blood transfusion with approximately 0 to 2 cases per year in the UK. The incidence was previously higher prior to universal leucodepletion of blood products. Severe thrombocytopenia occurs 5-12 days following a transfusion of red cells or platelets.
Platelets are coated in a number of antigens, including ABH antigens, Lewis antigens, HLA class I antigens and HPA antigens. Human Platelet Antigens (HPA) are implicated in PTP. This occurs when blood products are transfused containing platelets (red cells contain small amounts of platelets but this is very low since leucodepletion) with an HPA type to which the recipient has antibodies. The patient commonly has developed antibodies from sensitisation during pregnancy and therefore women are more likely to be affected. This antibody-antigen reaction results in destruction of the donor platelets and also the patient’s platelets. It is unclear why the patient’s platelets are also destroyed:
- ? formation of antobodies that cross react
- ? bystander lysis due to complement fixation
- ? antigens from transfused platelets are adsorbed onto recipient platelets
- ? formation of non-specific, pan-reacting ‘auto’ antibodies
The most common implicated antibody is anti-HPA1a. Antibodies are tested by NHS Blood and Transplant. Management is with high dose IvIg and transfusion of random ABO-matched platelets. It is a serious condition and may prove fatal.
Further information can be found here:
- Thrombocytopenia in pregnancy: http://bloodjournal.hematologylibrary.org/content/121/1/38.full.pdf
- Post transfusion purpura: http://hospital.blood.co.uk/library/pdf/INF153.pdf
- Iron deficiency in pregnancy: http://www.bcshguidelines.com/documents/UK_Guidelines_iron_deficiency_in_pregnancy.pdf
- Transfusion in obstetrics: http://www.transfusionguidelines.org/transfusion-handbook/9-effective-transfusion-in-obstetric-practice
- Patient blood management: http://www.transfusionguidelines.org/uk-transfusion-committees/national-blood-transfusion-committee/patient-blood-management