Anticoagulants

Question 1

Explain haemostasis.

Answer 1

Halting of bleeding by mechanincal or chemical means, or coagulation process of the body.

Question 2

Explain thrombus.

Answer 2

Aggregation of platelets, fibrin, clotting factors, and blood cells attached to an interior wall of a vein or artery.

Question 3

Explain embolus.

Answer 3

Foreign object, air, gas or thrombus that circulates in bloodstream until becoming lodged in a vessel.

Question 4

Explain coagulation.

Answer 4

Process of transforming a liquid into a solid.

Question 5

What is anticoagulants used for?

Answer 5

Prevent the formation of fibrin deposits, and thus prevent thrombus development.

Question 6

What are the two main types of anticoagulents? Give an example for each.

Answer 6

Parenteral - Heparin

Oral - Warfarin

Question 7

Explain the indications of heparin.

Answer 7

• used for all types of venous thromboembolism (VTE)
• prophylactic to prevent clots forming due to operation, inactivity etc.
• extracorporeal circulation (heart/lung and renal dialysis machines)

Question 8

Administering and maintaining the correct dosage within the therapeutic range is achieved by regular monitoring of blood concentrations. What is this monitoring called and how does it work?

Answer 8

Activated Partial Thromboplastin Time (APTT)

• measures the extent to which heparin inhibits thrombin
• low dose heparin such as 5000 units S/C, do not require monitoring

Question 9

Name eight adverse effects of heparin.

Answer 9

• haemorrhage
• local irritation (s/c injection site)
• mild pain
• haematoma
• elevated liver enzymes
• osteoporosis after prolonged high dose therapy
• early bleeding
  = bruising,
  = blood nose
  = bleeding gums
  = excessive menstrual bleeding
• internal bleeding
  = abdominal pain
  = malaena (blood stained stool)
  = haematemesis (blood stained vomit)
  = haemoptysis (blood stained sputum)
• thrombocytopenia

Question 10

Explain low molecular weight heparins (LMWH).

Answer 10

• reduce the incidence of heparin-induced thrombocytopenia
• easier to administer, and need less monitoring
• choice for use in thrombo-embolism in pregnancy

Question 11

Name one common form of LMWH.

Answer 11

• enoxaparin (Clexane)
• dalteparin (Fragmin)
• danaparoid (Orgaran)

Question 12

Explain the action of oral anticoagulants.

Answer 12

• interfere with hepatic synthesis of prothrombin (factor II) and factors VII, IX and X
• usually initiated at the same time or soon after starting heparin as it takes 36-48 hours to become effective

Question 13

Explain the indications of oral anticoagulants.

Answer 13

Prevention and management of DVT or pulmonary embolism.

Question 14

Name one common form of oral anticoagulants.

Answer 14

• phenindione (dindevan)

- warfarin (coumadin, marevan)

Question 15

Explain warfarin.

Answer 15

• only available in tablet form
• prevents extension of established clot or formation of new clots
• has a narrow therapeutic index
• effective after 36-72 hours, and may persist for 4-5 days after discontinuation of therapy

Question 16

Explain INR.

Answer 16

International Normalised Ratio (INR)

- used to regulate oral anticoagulant dosage

Question 17

Name the adverse effects of oral anticoagulants.

Answer 17

• bleeding
• alopecia
• fever
• hypersensitivity

Question 18

What is the specific antidote for Warfarin?

Answer 18

Phytomenadione (vitamin K, konakion adult)

Question 19

What is the specific antidote for Heparin?

Answer 19

Protamine sulfate