Heparins Flashcards
What conditions are heparins indicated for?
1) LMWH are used for primary prevention of VTE (PE, DVT)
2) Option for initial treatment of VTE, until oral anticoagulation (e.g. with warfarin, dabigatran) is established. Fondaparinux and DOACs are alternatives
3) ACS: Heparin (usually LMWH) or fondaparinux are used with antiplatelet agents to reduce clot progression or maintain revascularisation
Outline the MoA of heparins
Antithrombin (AT) inactivates clotting factors, particularly factors IIa (thrombin) and Xa, providing a natural break to the clotting process. Heparins and fondaparinux act by enhancing the anticoagulant effect of AT.
outline the main adverse effects of heparins (4)
1) Haemorrhage. Bruising or other reactions may occur at the injection site.
2) Hyperkalaemia
3) Rarely heparin-induced thrombocytopenia
4) Skin reactions
Haemorrhage is a side effect of heparins. Explain how this should be managed and what can be administered if rapid reversal of anticoagulation is required.
1) If haemorrhage occurs it is usually sufficient to withdraw unfractionated or LMWH.
2) If rapid reversal is required protamine sulfate is an antidote, this is effective for UFH but much less so for LMWH, and ineffective against fondaparinux.
what is heparin-induced thrombocytopenia?
Dangerous immune reaction to heparin, characterised by low platelet count and thrombosis
what are the clinical signs of heparin-induced thrombocytopenia?
1) 30% reduction of platelet count
2) Thrombosis
3) Skin allergy
How should heparin-induced thrombocytopenia be managed?
1) if heparin-induced thrombocytopenia is strongly suspected, the heparin should be stopped
2) Alternative anticoagulant such as danaparoid should be given
3) Ensure platelet counts return to normal range in those who require warfarin
Hyperkalaemia is one of the side effects that can occur from heparin administration. Explain why this happens and state the individuals who are most at risk
1) Occurs occasionally due to inhibition of aldosterone secretion by heparin
2) At risk: patients with diabetes, chronic renal failure, acidosis, raised plasma potassium or those taking potassium sparing drugs. (Risk increases with duration)
Which heparin is least likely to cause heparin-induced thrombocytopenia?
1) HIT, less likely with LMWH than UFH
2) Does not occur with fondaparinux (also lower risk of hemorrhage)
Who should heparins be used in caution with?
1) Caution in those at increased risk of bleeding, including: clotting disorders, severe uncontrolled hypertension and recent surgery or trauma.
2) Withhold immediately before and after invasive procedures, particularly lumbar puncture and spinal anaesthesia
3) Renal impairment
4) elderly
Why should LMWH and fondaparinux need to be used in caution in renal impairment?
LMWH and fondaparinux accumulate, so a lower dose or UFH should be used instead (UFH may be preferred in renal impairment)
Outline some of the important interactions with regards to heparins
Combining heparins with other antithrombotic drugs (e.g. antiplatelets, warfarin) has an additive effect. This is sometimes desirable (e.g. in treating ACS), but it is associated with an increased risk of bleeding, so should otherwise be avoided
outline the monitoring requirements for heparins
1) Platelets should be measured before treatment with LMWH and heparin (unf, and more regularly if given for more than 4 days
2) Plasma potassium concentrations should be measured in patients at risk of hyperkalaemia before starting the heparin and monitored regularly thereafter, esp it treatment is >7 days
With regards to monitoring explain the advantage of using LMWH and fondaparinux over UFH
1) LMWH and fondaparinux anticoagulant effects are sufficiently predictable to obviate the need for routine laboratory monitoring. Monitoring not required for once daily treatment regimen
2) UFH has a less predictable effect
What is used as a measure of anticoagulation in the following:
1) LMWH and fondaparinux
2) UFH
1) Plasma antifactor Xa activity is measured (e.g. renal impairment, pregnancy, those under or overweight)
2) UFH: Activated partial thromboplastin ratio (APTR) (usual target 1.5–2.5)
