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Blood thinners

Doctors prescribe medicines for varied reasons, to cure an ailment, to prevent or stop an infection, to ease symptoms, to reduce risks etc. But if there is one particular group of medicines where there is a need for rigorous monitoring regime when taken, it is blood thinners. Not without a reason. Though approved by the FDA, if not handled properly, prolonged use of blood thinners can be unsafe.


Need for Blood thinners

Blood thinners reduce the ability of the blood to clot. Blood thinners belong to a class of drugs called anticoagulants. Immediately after an injury, a scrape or a cut, the blood coagulates and seals the wound, forming a scab to protect from infection. The blood clots formed will be naturally dissolved in the body after the injury is healed. Here blood clotting is a saver and is essential for the body.


The mechanism is regarded as dangerous when blood clots form in the blood stream without an obvious injury and if the blood clot fails to dissolve naturally after the injury heals. The situation poses great risks as it can block circulation; the blood clot can travel to the arteries or veins in the brain, heart, kidneys, lungs and limbs. This in turn can lead to life-threatening conditions such as heart attack, stroke, damage body's organs and in extreme cases result in loss of life.

An updated (February 2014) American Academy of Neurology (AAN) guideline recommends people with an irregular heartbeat to take blood thinners to reduce the risk of stroke. As per doctor's prescription, every year around 2 million people take blood thinner medications every day. It is strongly recommended that blood thinner be taken only under medical supervision.


New vs. old blood thinners

Warfarin was introduced sixty years ago. It is regarded as the oldest anticoagulant blood thinner medication. For decades, Warfarin was the only blood thinner available to lower risks of stroke. There are new additions. A recent study has showed that new blood thinners might be more effective than older medications.

  • Dabigatran (Generic name) approved by FDA in October 2010
  • Rivaroxaban (Generic name) approved by FDA in October 2011
  • Apixaban (Generic name) approved by FDA in December 2012.

Detailed studies comparing Warfarin with the new addition state the following:


  • New drugs are similar or even better than warfarin in preventing stroke.

  • As the optimal dose of Warfarin varies from patient to patient, blood levels of patients on Warfarin need to be checked periodically.

  • New blood thinner medications are regarded as more convenient because the patients taking them do not need to have blood levels checked.

  • A study on effectiveness reflected that new blood thinners were approximately 20% more effective in reducing the risk of stroke and 10 % more effective in reducing the risk of death when compared to warfarin.

  • New blood thinners, in addition to being more convenient, are potentially more effective than and similar in safety to warfarin.

  • New blood thinners are more expensive than Warfarin.

  • Long-term safety and side effects of new blood thinners is not yet available.

  • With Warfarin, it is easier to reverse the blood thinning effect if a patient is bleeding or needs urgent surgery.

Types of blood thinners

It is chemical formulations that contribute to preventing clotting in various ways. Broadly blood thinner medications are classified into anticoagulant and anti platelet blood thinners.


Anticoagulant blood thinners

Anticoagulant blood thinner medications help decrease the tendency of blood clot formation. There are two ways to decrease the formation of blood clots in the body. Anticoagulants can interfere with platelets or block the body's production of clotting substances. Anticoagulant blood thinners are prescribed for people who have had a condition caused by a blood clot or are at risk of developing one.

Anticoagulant blood thinners are usually given by mouth. In some cases anticoagulants are given intravenously or by injecting them just under the skin (subcutaneously).


Warfarin: Warfarin is the generic drug. In the US, Warfarin is sold under the brand names Coumadin and Jantoven. Doctors prescribe Warfarin for two reasons, to prevent the formation of harmful blood clots or treat an existing blood clot. Some conditions for which Warfarin is prescribed include:



Patients prescribed Warfarin ought to know how Warfarin works. Knowing helps limit the intake of vitamin K rich foods like dark green vegetables such as broccoli, spinach, turnip greens, green peas etc. At any time, the blood needs certain proteins to clot. These proteins are made in the liver. To enable the liver in the process, Vitamin K is required.


When Warfarin is administered, it reduces the liver's ability to use Vitamin K. Warfarin and Vitamin K work against each other. Thus, the formation of blood clot becomes harder. The interaction between Warfarin and Vitamin K explains the need to partake a diet that is constant in Vitamin K while on Warfarin. The dosage of Warfarin may vary from person to person. A blood test may be recommended to determine the dosage. This blood test, Prothrombin Time or International Normalized Ratio is required to monitor the body's response to Warfarin. Based on test results, Warfarin dose will be determined.


Side effects of Warfarin

Warfarin or Heparin, a common side effect of any anticoagulant medication is the risk of excessive bleeding. As these medicines prolong or lengthen or makes blood clot formation harder, it increases the time for formation of blood clots. If the time taken is too long, there is a possibility of excessive bleeding. There are other symptoms to look out for which are more common with Warfarin. Patients on Warfarin should immediately seek medical attention for any these common Warfarin side effects.


  • passing blood in your urine or feces (stools)
  • passing black feces
  • severe bruising
  • prolonged nosebleeds for more than 10 minutes
  • bleeding gums
  • blood while throwing up (vomiting)
  • coughing up blood
  • unusual headaches
  • sudden severe back pain
  • difficulty breathing or chest pain

Women who take Warfarin should contact health care provider if they experience heavy or increased bleeding during menstruation or any other bleeding from the vagina.

Irrespective of the gender, some patients may experience rashes, diarrhea, nausea, hair loss while on Warfarin. These are not common side effects but are termed as additional side effects of Warfarin.

Doctors do advice patients to seek help if the patient is involved in a major accident, experiences a significant blow to the head and finds it difficult to stop bleeding, if any. As Warfarin can interact with many other medicines, so do inform the doctor about all the medications being taken.

Warfarin during pregnancy: Warfarin should be avoided during pregnancy and women with certain health conditions like high blood pressure, ulcer in the digestive tract should not take Warfarin as it can lead to severe health complications.

Long terms risks of using Warfarin: Extensive research on prolonged use of Warfarin suggests that the risk increases with age. The patient is at risk of serious or even fatal bleeding including internal bleeding. In particular the risks are:


  • Bleeding strokes, or brain strokes (hemorrhage strokes)
  • Calcium build-up in the arteries and narrowing of the aortic valve that goes from the heart and carries oxygen to the body (aortic valve stenosis)

Heparin: Heparin is the generic name. In US, Heparin is available under the brand names Lipohepin, liquaemin and Panheparin. Heparin decreases the clotting ability of the blood and also prevents existing clots from getting larger. Thereby, the normal body systems dissolve the clots that are already formed. Heparin is usually administered as an injection. Heparin can be injected subcutaneously or as an intravenous infusion. The advantage of IV is that it can be turned off quickly for safety reasons. Heparin is prescribed for conditions such as:


  • Deep venous thrombosis
  • Arterial embolism
  • Pulmonary embolism
  • Prevention of blood clot during heart surgery, dialysis or blood transfusions
  • Peripheral artery obstruction by a foreign substance or a blood clot
  • Treatment to prevent peripheral artery thrombo-embolism.

It helps to know how heparin works. Heparin ensures that an anti-clotting protein which is present in the body works better, thus decreasing the clotting ability of the blood.

Available in different strengths, the doctor must prescribe the strength depending on the purpose for which it is prescribed. During the course of treatment, the doctor may increase or decrease the dosage.


Side effects of heparin

A unique possible side effect of Heparin is that several weeks after stopping the injection, bleeding episodes may occur. If the patient notices bruising or unusual bleeding such as a nosebleed, blood in the urine or stools, black or tarry stools or any other bleeding that doesn't cease, contact your healthcare provider.

Besides the common side effects of anticoagulant medications, Heparin's other side effects are visible at that point where the solution is injected.


  • Swelling
  • Pain
  • Irritation
  • Bruising

Herparin during pregnancy: FDA category for Heparin is C meaning there isn't established information that proves whether Heparin affects the fetus. It is best for pregnant women as well as breast-feeding mothers to use Heparin only if the medicine is prescribed by the doctor.


Long term risks of using Heparin

Prolonged use of Heparin particularly in the elderly may cause osteoporosis, a condition in which the bones become weak and may break easily.


Antiplatelet blood thinners

Antiplatelet blood thinner medications work to prevent the platelets (small cells in the blood) from clumping together to form a blood clot. This happens by inhibiting the production of thromboxane, a chemical that signals other platelets to come together. By inhibiting the production of thromboxane, platelets cease to come together to form the blood clot.

Thromboxane's role is helpful for a normal healthy individual who has suffered a wound. It acts as a self-sealing material. But, in the case of a stroke survivor, thromboxane's ability to bind and form a blood clot is potentially life-threatening. Hence, the need to use an antiplatelet blood thinner which are usually available in the form of tablets only.


Doctors prescribe antiplatelet Aspirin to patients who have had a stroke or TIA (transient ischemic attack) so as to reduce the risk of having another stroke. This is possible with Aspirin as it interferes with the blood's clotting action. The dosage varies from patient to patient and is largely guided by the patient's health condition.

Though Aspirin is available OTC (over the counter), doctors recommend low doses of Aspirin for patients with the following medical history.

  • Patients who have had prior heart attacks
  • Patients who have had prior strokes
  • Patients with exertional and unstable angina
  • Patients with TIAs (transient ischemic attack called mini-stroke)
  • Patients at risk of atherosclerosis.

Aspirin is prescribed to patients who are considered to be at risk of having heart attack or stroke. Anyone with high cholesterol, high blood pressure, diabetic and smoke aggressively are regarded to be at risk of having heart attack or stroke.


Side effect of Aspirin

Most common side effect of taking low doses of Aspirin (100 mg dose) is heartburn and stomach upset. Seldom has there been a very serious side effect related to taking Aspirin as a blood thinner medication. However it is best to be aware of possible serious side effects such as bruising/bleeding, difficulty hearing, ringing in the ears, and change in urine amount, persistent or severe nausea /vomiting, unexplained tiredness, dizziness, dark urine, yellowing of eyes or skin.


Aspirin during pregnancy

The FDA has not assigned formally a pregnancy category. Aspirin is not recommended for use during pregnancy and while breast-feeding as it excretes into breast milk in small amounts.


Other antiplatelet blood thinners

Besides Aspirin, other antiplatelet medicines that are prescribed to prevent the platelets from sticking together include the following. Doctors prescribe a specific antiplatelet blood thinner taking into account the specific health condition and relative effectiveness of the blood thinner medicine. New drugs are continually added to the list with FDA approval.


  • Aspirin plus clopidogrel (brand name Plavix) is prescribed for patients who are diagnosed with coronary syndrome such as unstable angina or have had a heart attack, if stent is implanted or if the patient has had a stroke or mini stroke.

  • Aspirin plus extended dipyridamole (brand name Aggrenox) is prescribed for patients who have had a stroke or mini stroke (TIA).

  • Clopidogrel (brand name Plavix) is recommended by doctors if Aspirin is not suitable for a patient who has been diagnosed with acute coronary syndrome or had a stent implanted.

Long term risks of using Aspirin

Daily use of aspirin can have serious side effects including internal bleeding. Prolonged use of aspirin at higher doses (> 500 mg) can cause stomach ulcers, and can also prolonged bleeding.


Blood Type

Blood typing and cross matching test results are determined based on the reaction between the antigens and antibodies. An antigen causes the body to launch an attack against a foreign body and is known as an immune response. The attack begins when the body builds a special protein called an antibody. This antibody is uniquely designed to attack and nullify the foreign attack. In general a person's body makes antibodies only against foreign bodies and not against its own antigens.


Among the various antigens present in a person's body, the antigens found on the surface of red blood cells are important because they determine the person's blood type. When red blood cells having a certain blood type antigen are mixed with serum containing antibodies against that particular antigen, the antibodies attack and stick to the antigen. This is seen as clumping, formation of clump of cells while testing is done in a test tube.


For typing blood, a person's blood cells and serum are mixed in a test tube along with commercially prepared serum and cells. Clumping refers to the type of antigens or antibodies present and helps in determining the person's blood type. While cross matching blood, the patient's serum is mixed with cells from donor blood that may be used for transfusion. Clumping or lack of clumping in the test tube tells whether or not the blood is compatible.


There are over 600 known red blood cell antigens that are organized into 22 blood group systems. However routine blood typing and cross matching generally involves only two systems namely:

  • ABO
  • Rh blood group systems

Blood typing helps in determining the blood type a person has. ABO system is used to classify the blood type. There are four main categories under the ABO system:


Type O

Type A

Type B

Type AB

Blood typing also helps in determining the Rh factor of the blood. People who have the Rh protein in their blood are termed as Rh + (positive) and ones without it are termed as Rh – (negative). The Rh type is useful in deciding the blood type a person can safely receive during transfusion.

Blood type of a person is inherited and there is no normal or abnormal type. The blood type of a person is determined by checking out the following:

Type A: If the blood cells of a person agglutinate with Type A serum then the person has A blood type.

Type B: If the blood cells of a person agglutinate with Type B serum then the person has B blood type.

Type AB: If the blood cells of a person agglutinate with Type A and Type B serum then the person has AB blood type.

Type O: If the blood cell of a person does not agglutinate with Type A or Type B serum then the person has O blood type.

Understanding back typing

People with type A blood will have anti-B antibodies. People with type B blood will have anti-A antibodies. People with type O blood will have both. So if the person's:

Blood clumps only when B cells are added then the blood type of the person is A.
Blood clumps only when A cells are added then the blood type of the person is B.
Blood clumps in both cases the blood type of the person is O.
Blood does not clump when both types of blood are added then the blood type of the person is AB.

Understanding Rh results

1. If the person's blood clumps together when anti-Rh serum is added then the person is Rh+.
2. If the person's blood does not clump together when anti-Rh serum is added then the person is Rh-.

Blood typing and cross matching results

There is no normal or abnormal result. However the result may make us understand the following:

  • Blood typing and cross matching help to find the most compatible blood for the recipient.

  • If the recipient's cross matching finds no antibody then blood typing would not be a problem at all.

  • If the cross matching results in finding antibodies then the lab finds out what type of an antibody it is and how it can be isolated.

  • However not all antibodies make it incompatible for blood transmission or transfusion.


Blood Transfusion

Blood transfusion is one of the important procedures administered in healthcare centers to meet surgical and trauma needs. This procedure is categorized under transfusion medicine section. Blood transfusion is a high-risk procedure as it involves multiple protocols and guidelines for safe and effective transfusion.


Guidelines and Procedure

Transfusion medicine has high significance as it involves the transfusion of blood and blood products depending upon the patient needs. Blood required for the transfusion is obtained from blood banks, which are established either by the government or privately following NCCLS standards for the blood banks. The standards are evaluated by organizations such as WHO to set a uniform and global protocol for safe transfusion. Blood transfusion is predominantly done to increase the percentage of hemoglobin in anemic patients and also to replace vital components such as platelets and serum proteins in some medical conditions. Other reasons for blood transfusion is to replace the amount of blood lost during surgery or trauma. Patients suffering thrombocytopenia (any disorder in which there is an abnormally low amount of platelets) might be in need of platelet transfusion.


Blood banks are authorized by the government to collect blood of different groups. Some of the rare groups include B negative, O negative and Bombay blood group. In these situations, the names and the address of these respective rare blood types are noted to ensure timely availability in case of a transfusion request. Cancer patients also require transfusion in case of conditions such as leukemia and malignant carcinomas associated with spleen or bone marrow. Leukocyte reduction procedure is followed in some transfusion centers in order to minimize the incidence of transfusion-associated allergic reactions. All donors are checked for a three-month gap before the subsequent transfusion to facilitate fresh blood collection from the donors containing viable red blood cells.


Different types of Blood transfusions:

Fresh Whole Blood: This is mostly needed during cardiac surgery or massive hemorrhage. Fresh Whole blood has RBC, plasma and fresh platelets.

Packed RBC: This is mostly needed to raise the hematocrit (the proportion of total blood volume that is composed of red blood cells).

Frozen packed RBC: Stored for nearly 3 years, frozen packed RBC is sparingly used. It is often used for rare blood groups. Patients suffering severe leukoagglutinin reactions or anaphylactic reactions might need this.

Leukocyte-Poor Blood: Patients who suffer severe leukoagglutinin reactions might need this. It is an expensive process as WBC are removed by centrifugation.


Precautions and risks

Transfusion is a very important procedure and hence primary analysis of the donor blood is done in order to avoid blood borne sepsis, transfusion allergies and organ damage. The donor blood is always cross-matched with the recipient's in order to check the compatibility of the blood. All procedures are documented to ensure safety and tracking of a transfusion procedure, as it is associated with medico-legal protocols. The A and B antigens are the first check before transfusion. In emergencies, type O/Rh-negative blood can be given to any recipient and usually packed cells are given. The Rh factor has also to be tested. Blood from the donor is also investigated for infections such as HIV 1&2, HBV, HCV, and VDRL to ensure safe transfusion.


Blood is collected from the healthy donor in a blood bank by administering venipuncture procedure from the brachial region. The obtained blood is transported for immediate need in surgeries or stored for few days in case of a scheduled surgery having the requirement for the particular blood group. The transfusion requirement is clearly stated in the surgical form and the blood bank technicians provide number of units required on the given date. Some of the common side effects associated with blood transfusions are infections of both viral and bacterial origin obtained from an infected donor. Receipt of blood contaminated with gram-negative bacteria often causes septic shock, Disseminated intravascular coagulation or DIA (a large amount of procoagulant enters the blood stream over a short period of time, overwhelming the body’s ability to replenish coagulation factors and causing bleeding) and acute kidney injury. Receipt of blood with gram-positive bacteria causes fever and Bacteremia (presence of bacteria in blood) but rarely causes sepsis.


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Collection of Pages - Last revised Date: March 23, 2019