Scenario 13: Heparin Induced Thrombocytopenia (HIT)

A 22-year-old male is in the Surgical Intensive Care Unit (SICU) following a motor vehicle crash (MVC) where he sustained multiple life-threatening injuries including a torn aorta, ruptured spleen, and bilateral femur fractures. He has had difficulty maintaining his mean arterial pressure (MAP) and has required various vasopressors. He has a triple lumen central venous catheter (CVC) for monitoring his central venous pressure, administration of medications and blood products, as well as total parenteral nutrition. Per hospital protocol, he is receiving an unfractionated heparin 1:1000 flush after administration of each of the triple antibiotics that have been ordered to maintain patency of the lumens.  Seven days post injury, the APRN in the SICU is reviewing the patient’s morning labs and notes that his platelet count has dropped precipitously to 50,000 /mm3 from 148,000/mm3 two days ago. The APRN suspects the patient is developing heparin induced thrombocytopenia (HIT).

Question 1 of 2:

What is underlying pathophysiology of heparin induced thrombocytopenia?

Question 2 of 2:

The APRN assesses the patient and notes there is a decreased right posterior tibial pulse with cyanosis of the entire foot. The APRN recognizes this probably represents arterial thrombus formation. How does someone who is receiving heparin develop arterial and venous thrombosis?