ORAL ANTICOAGULATION
Oral Anticoagulants are drugs that are used as blood thinners especially in patients to prevent clotting of the blood. These medicines are useful in patients who have undergone valve replacements and in some special cases of coronary and vascular diseases.
INDICATIONS OF ORAL ANTICOAGULANTS
Ø Valve replacement with a mechanical valve and in this condition the patient has to use the medicine life-long
Ø Valve replacement with tissue valves and in some patients with valve repair. These patients have to use the drugs for only about 6 weeks as thereafter the artificial surfaces will get covered with patient’s cells
Ø Chronic atrial fibrillation: Here, the patient has a rhythm abnormality leading to irregular beating of the atrium [collecting part of the heart] and that leads to irregular heart beating. The patients usually will develop clot in the appendage of the left atrium and in some this may get dislodged and travel along the blood stream to block the distal part of blood vessel in the heart, limb or brain. This may have disastrous complications. The anticoagulation treatment should be considered as long as the patient suffers from atrial fibrillation.
Ø Coronary Surgery: Certain surgeons do administer oral anticoagulants in patients with coronary grafts. We use these drugs in patients who have undergone coronary endarterectomy as there is a large raw area which is prone to induce clotting within the blood vessel and lead to sudden obstruction, ischemia or heart attack. This treatment is usually given for 6-8weeks. In case the patient is having problem with anti-platelet drugs, there may be some logic for using the drugs. It is sometimes given in patients who have sluggish flow in the coronaries due to dilated ectatic vessels or coronary aneurysms.
Ø Deep vein thrombosis: Patients who have had clotting of the deep veins of the legs or sometimes clotting of the veins of the arm (Paget Shroeder Syndrome etc) will require to take oral anticoagulants till there is resolution of the venous problem.
Ø Vascular Surgery: In some patients with vascular surgery, oral anticoagulants are advised especially if there is a large raw area or there is expectation of sluggish flow.
CARE OF ORAL ANTICOAGULATION PROTOCOLS
v There are various types of tablets that are used for oral anticoagulants and mostly it is either WARFARIN or NICOUMALONE [ACITROM]
v These tablets act by antagonizing the action of Vitamin K in the liver and that is they suppress the production of the clotting agents in the bloodstream. In this way they prevent clotting and the effect is variable in nature depending on the amount of dietary Vitamin K and the function of the liver against the absorption and bioavailability of these medicines
v The function of these tablets is monitored by the Prothrombin time test and to effect a standardization of the results the test was normalized by the International Normalisation Ratio [INR]. Therefore mentioning the Prothrombin time alone is obsolete
v The Prothrombin time is measured against a control time and the ratio of patient’s time against the control is taken as the Prothrombin time ratio. The INR is calculated from the ratio. The expected INR in a patient who is on oral anticoagulant should be about 1.5 to 4.0. For Valve cases, we prefer an INR of 2.0-4.0
v Above an INR of 4.0, we can expect bleeding and that may occur from minor injuries or without cause such as gum bleeding, stroke or bleeding in the urine.
v Below an INR of 1.5, the purpose of taking the tablets is lost as it is useless and this may give rise to disastrous problems such as valve blockage or pulmonary embolism.
For further information on guidelines and protocols of oral anticoagulation click here:
