# Heparin --- **Heparin** is a [[anticoagulants]] and anticoagulant. It works by affecting the [[coagulation|clotting cascade]] (but a different part than [[warfarin]]). This is is quite often prescribed for managing [[thrombus|thromboembolic]] disorders such as DVT or PE or prophylactically if patients are at a higher risk for thrombosis, such as if they are on bed rest or limited activity for longer than 5 days. Before giving heparin it is important to check a patient's platelet and [[partial and activated partial thromboplastin time|PTT]] results. Endogenous heparin is actually a produced by [[mast cells]] in connective tissues surrounding the capillaries. This type of heparin is referred to "endogenous heparin", and is found various body tissues, most abundantly in the liver and lungs. The heparin that we use as medicine is "exogenous heparin", which is obtained from bovine lung or porcine intestinal mucosa. Heparins (and LMWHs, see below) do not cross the [[placenta|blood-placental barrier]], so these are the *only* safe anticoagulant to be given during pregnancy. This is especially important to know because pregnancy puts a person in a hypercoagulable state. ## Heparin Induced Thrombocytopenia Heparin can cause increased bleeding, which is a general problem with anticoagulants, but a severe adverse reaction that can be triggered is **heparin induced thrombocytopenia** or **HIT**. As the name suggests, in some patients (about 5%) heparin interacts with platelets become aggregated and removed from circulation. - Signs & Symptoms - About 4-14 days after heparin started; up to 5% of those on heparin get HIT - Results from heparin therapy- activated platelets are aggregated and removed from circulation. - Basically platelets get used up by making random clots - Get baseline platelet count prior to starting heparin gtt - Comorbidities: - About 50% of people who develop HIT go on to develop a thrombosis (VTE, CVA, etc.) - This is because HIT is really about an inappropriate aggregation of platelets, so it can trigger a clot somewhere - Labs: - detectable antiheparin-PD4 antibodies, + IgG-specific ELISA assay, + platelet activation assay, monitor CBC (platelets) - Treatment: - DC heparin and start alternative anticoagulant [[anticoagulants|argatroban]] - Avoid all heparin in the future including flushes. Mark as 'Allergy'. ## aPTT Heparin lengthens the [[partial and activated partial thromboplastin time|aPTT]] time, or in other words it takes longer to clot the blood on heparin. ## LMWHs Low-molecular-weight heparins (LMWHs) also exist. They are more predictable and have a longer half-life. They can be given once a day. - **enoxaparin** (Lovenox) - **dalteparin** (Fragmin) The dose is based on the patient's body weight, which means we don't have to monitor the lab values as closely and this is why these are the drugs we usually send patients home on. >[!science] Cultural considerations >LMWHs are porcine based, which means taking them may against a person's cultural or religious preferences ## Antidote: Protamine Sulfate The antidote to heparin is **protamine sulfate**, which works by binding to the heparin molecules. ___