Why does heparin (Heparin) cause bleeding?

From the Guidelines

Heparin can cause bleeding due to its anticoagulant effect, which can lead to an increased risk of hemorrhage, particularly in patients with underlying bleeding disorders or those undergoing invasive procedures. The use of heparin, including unfractionated heparin (UFH) and low molecular weight heparin (LMWH), is a well-established treatment for various conditions, including pulmonary embolism and deep vein thrombosis 1. However, heparin therapy can increase the risk of bleeding, particularly in patients with certain contraindications, such as active bleeding, haemostatic disorders, severe uncontrolled hypertension, and recent surgery 1.

Some key points to consider when using heparin include:

• Monitoring platelet count is essential to detect heparin-induced thrombocytopenia (HIT), a rare but life-threatening side effect 1
• The risk of bleeding is higher with UFH compared to LMWH, particularly in patients with renal failure 1
• Contraindications to pharmacological thromboprophylaxis include patients with significant thrombocytopenia, untreated inherited or acquired bleeding disorders, evidence of active bleeding, and uncontrolled hypertension 1
• The optimal timing for the initiation of pharmacological thromboprophylaxis is crucial, and delaying treatment can increase the risk of mortality 1

In terms of management, it is essential to weigh the benefits and risks of heparin therapy and to closely monitor patients for signs of bleeding or other adverse effects. The use of heparin should be individualized, and the dose and duration of treatment should be adjusted based on the patient's specific condition and response to therapy. Additionally, alternative treatments, such as mechanical methods or other anticoagulants, may be considered in patients with a high risk of bleeding or other contraindications 1.

From the Research

Causes of Bleeding in HUS

• HUS is characterized by microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury (AKI) 2
• The major cause of HUS in childhood is infection with verocytotoxin (Shiga-like toxin)-producing bacteria, usually enterohemorrhagic Escherichia coli (VTEC/STEC) 2
• Infection with STEC can lead to bloody diarrhea, which is a common symptom of HUS 2, 3
• Thrombocytopenia, a condition characterized by low platelet count, can increase the risk of bleeding in HUS patients 4
• The activation of the coagulation system within capillaries can lead to organ failure and bleeding in HUS patients 5

Risk Factors for Bleeding in HUS

• Age under 3 years is a risk factor for HUS and bleeding 3
• The presence of certain STEC serogroups, such as O157, can increase the risk of HUS and bleeding 3
• The presence of certain Shiga toxin genes, such as stx2 and stx2a, can increase the risk of HUS and bleeding 3
• Leukocyte count over 20 × 10^9/L is a predictive factor for poor renal outcome and bleeding in HUS patients 3

Management of Bleeding in HUS

• Transfusion with packed red blood cells is needed in case of severe anemia 2
• Platelet transfusions are limited to the need for a surgical procedure or in active bleeding 2
• Eculizumab has been used for the treatment of STEC-HUS, but the value of this treatment remains to be determined 2, 4