Low Molecular Weight Heparin
CLASS
- anticoagulant
MECHANISM OF ACTION
- potentiates the action of antithrombin III on Xa
PHARMACEUTICS
- injection: clear, colourless
- MW 2,000-6,000
DOSE
DVT prophylaxis:
- 40mg SC OD
- always chart dose at night -> procedures done during day will not be effected
Therapeutic anti-coagulation:
- 1mg/g BD or 1.5mg/kg OD-> dose adjust in renal failure
- calculate GFR
- loading dose: 1mg/kg (for everyone)
- maintenance dosing based on GFR:
-> > 60mL/min – 1mg/kg Q12 hourly or 1.5mg/kg Q24 hourly
-> 30-60mL/min – 0.8mg/kg Q12 hourly
-> < 30mL/min – 0.66mg/kg Q12 hourly - can measure anti-Xa levels in therapeutic anti-coagulation (renal impairment + very low or very high BMI, pregnancy)
ANTI-Xa MONITORING
- establish steady state (48 hours of dosing)
- use peak 4 hours after dose
- mostly not recommended
- therapeutic range = peak 0.5-1.2 IU/mL (BD dosing), 1-2 IU/mL (OD dosing)
- troughs not routinely recommended:
-> in BD dosing trough > 0.5 IU/mL at 12 hours post dose then patient can be changed to once daily dosing)
-> in OD dosing trough should be < 0.4 IU/mL at 20 hours post dose
DOSE ADJUSTMENT
- depending on peak level -> adjust by 25-50%
- repeat level after 48 hours
INDICATIONS
(1) DVT prophylaxis
(2) therapeutic anticoagulation
- VTE
- ACS
- arterial thrombosis
- AF
- bridging therapy for the chronically anti-coagulated
CONTRAINDICATIONS
- hypersensitivity
- bleeding
- procedures/surgery
- uncontrolled hypertension
- recent high risk surgery (CNS, TURP, eye)
ADVERSE EFFECTS
- bleeding
- decreased incidence of HITS
PHARMACOKINETICS
- Absorption – higher bioavailability than heparin
- Distribution
- Metabolism
- Elimination – t ½ = 2-3 hrs
References and Links
- Emergency Medicine PharmD — Protamine for LMWH (2013)
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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