COAGULATION
COAGULATION TESTS
INR; aPTT

Any patient who has undergone major surgery, sustained a significant trauma or suffered a serious infection will have a widespread inflammatory response. Visibly, inflammation causes fluid to collect throughout the body tissues, making the patient look swollen. It also makes the blood vessels dilate, leading to a reduction in the blood pressure. This often needs to be treated with large amounts of intravenous fluids. Systemic inflammation will also increase the metabolic rate, causing the heart rate and breathing to increase. It can also cause a mild fever and rise in the white blood cell count.

Inflammation also activates the clotting system. The medical term for clotting is coagulation. When a patient has systemic inflammation, they can develop systemic clotting. If the cause of the inflammation is not relieved, clotting can become a serious problems. It can begin to occur in all of the tiny capillaries, blocking the flow of blood and oxygen to the tissues and organs. This can lead to organ failure.

When a patient has a lot of clotting taking place, they can run out of the cells that they need to make clots. Platelets are a type of blood cell that will stick to the wall of a blood vessel and create a clot. We also have many different proteins in the blood that stimulate clot production, and make the clot strong. These proteins are called clotting factors or coagulation factors.

When clotting factors get used up because of excessive clotting, the patient may begin to bleed. Bleeding that develops due to the depletion of clotting factors is a life-threatening complication called Disseminated Intravascular Coagulation (or DIC).

Laboratory tests can be done to evaluate the coagulation system. The most common tests are called the INR (International Normalized Ratio) and the aPTT (Activated Partial Prothrombin Time). These tests measure the time in seconds that it takes the blood to clot. If it takes longer for blood to clot than normal, the INR and/or aPTT become higher. This indicates an increased risk for bleeding. If the INR and aPTT has increased because the patient has used up too many clotting factors, we can replace the clotting factors by giving a transfusion of Fresh Frozen Plasma. On rare occasions, we may give a concentrated preparation of a specific clotting factor.

Anticoagulants (Blood Thinners):

We sometimes want to prolong the time it takes for blood to clot. We may want to do this if the patient is at risk for serious clotting problems, such as a heart attack or Deep Vein Thrombosis. Drugs that prolong the time it takes for blood to clot are called anticoagulants or blood thinners. Heparin is a commonly used anticoagulant.

We often give low dose anticoagulants by infection under the skin to thin the blood and reduce the chances of develop blood clots. We call this DVT (Deep Vein Thrombosis) or Veno-Thrombotic Embolic (VTE) prevention.

 

 

Last Updated: October 23, 2014

Blood

Image 1: Blood transfusion

 

 

 

 

 

LHSCPatients, Families & Visitors

Last Updated October 23, 2014 | © 2007, LHSC, London Ontario Canada