Heparin as an Anticoagulant (Injection)
Antithrombin III blocks the formation of prothrombin to thrombrin. Antithrombin III interrupts the coagulation cascade, not allowing fibrinogen to turn to fibrin and a lattice won’t be formed.
Heparin activates Antithrombin III, so clots can’t form. There are several potential uses of heparin and it’s primarily used as an injectable. When heparin is administered subcutaneously, it is usually a low dose and it’s a prophylactic dose for high risk patients to prevent post-operative clotting. Usually these high risk patients are hip patients, abdominal surgery patients, bed-ridden patients and so forth.
Heparin as a constant infusion following bolus dose
We also use heparin intravenously as a constant infusion following a bolus dose when we are dealing with serious thrombosis such as deep vein thrombosis and pulmonary embolism. These people will get a bolus dose to get their levels up and then an infusion will start to maintain them. We hopefully will be able to switch them to an oral medication such as warfarin.
Heparin Flush
When a patient is hospitalized, we need an access port to their veins. If they are getting something intravenously, they are usually getting multiple medications through the same access port. We call this piggy backing. A catheter is typically inserted into the patients vein with a port outside the skin so that instead instead of sticking the patient with a needle everytime, we stick it into the port.
When we disconnect the infusion, we flush the line with saline and push the rest of the drug (~1cc) into the vein. If we have a catheter sitting in the persons vein with nothing flowing through it for the next several hours, a clot could form there, making this catheter line unusable and having to be pulled. So after the line is flushed with saline, we put a very small amount of heparin in there and let it dwell in the catheter, to hopefully not allow a clot to form. Then hours later we could use it again.
There are many hospitals that have a procedure protocol to never put heparin in a heparin lock because some studies have shown that saline is almost good enough. So the hospital are taking a financial risk because it saves them lots of money. After 3 days the policy is such that they have to put a new catheter in anyway. So they are taking the chance that this saline flush is going to be good for 3 days. They don’t, however, take a chance with this when it’s a central-line since it’s going straight to the heart with the vena-cavae. This may be a PICC line (peripherally inserted central catheter). They can’t take the risk of this line clotting.
Why do we ever put a catheter into the vena cavae? It’s when a person is intended to receive therapy for a prolonged period of time. It could be antibiotic treatment that could go on for weeks. Another possibility is cancer chemotherapy. Another reason is when a person can’t eat and must get all their nutrition through a very hypertonic solution (25-35% dextrose). Only at the vena cavae will this hypertonic solution be diluted fast enough.
Recap
- Heparin Activates Antithrombin III
- Injectable administration only
- Subcutaneously is used to prevent post operative clotting, or bed ridden patient clotting
- Heparin flush
- Constant infusion following bolus dose
- Treatment of deep venous thrombosis, pulmonary embolism
- Eventually we may switch to warfarin
