• Anticoagulation in patients with heparin induced thrombocytopenia (HIT)
  
  • see Heparin induced thrombocytopenia guideline
• Argatroban is the preferred alternative anticoagulant in patients with HIT with critical illness, increased bleeding risk, extensive thrombosis, or potential need for urgent procedures
• Fondaparinux or a DOAC are reasonable options in clinically stable patients at low to average risk of bleeding (off licence use)
• Thrombocytopenia is not a contraindication to anticoagulation in HIT
• For advice, contact consultant haematologist

• Preferred alternative anticoagulant in critically ill patients with suspected or proven HIT (with/without thrombosis)
• Direct thrombin inhibitor with a half-life of 50 min
• Eliminated by hepato-biliary route

Administration

• Check baseline platelet count and APTT
• No dose modification in patients with renal impairment
• Specific dosage protocol for patients on haemodialysis, contact haematologist
• Use with caution in patients in critical care and hepatic impairment (e.g. Child Pugh class B)
• Contraindicated in patients with severe hepatic impairment https://www.mdcalc.com/calc/340/child-pugh-score-cirrhosis-mortality (e.g. Child Pugh class C)
• No proven reversal agent - if patient bleeds, contact consultant haematologist

IV infusion by syringe pump

• Preparation: 50 mg/50 mL (1 mg/mL) solution for infusion - ready to use
• Administer via a syringe driver

Dosage

• Maximum dose 10 microgram/kg/min
• Check APTT 2 hr after initiation of infusion

Table 1: Argatroban dosage for HIT

• DOACs are preferred for clinically stable HIT patients (with/without thrombosis) at low to average bleeding risk
• Use is off licence but supported by major international guidelines 
• Rivaroxaban has been most studied in this area - if contraindicated, discuss alternative DOAC with consultant haematologist 

Contraindications

• Same in HIT and VTE
• DOACs contraindicated in pregnancy and breastfeeding
• If eGFR <15 mL/min (30 mL/min for dabigatran), contraindicated
• If eGFR <50 mL/min, discuss with haematologist and renal physician 

Rivaroxaban

• HIT with thrombosis - 15 mg 12-hrly for 21 days then 20 mg once daily
• HIT without thrombosis - 15 mg 12-hrly until platelet count >150 x 10⁹/L then 20 mg once daily
• All doses to be taken with food

• Danaparoid is a low-molecular-weight heparinoid, chemically distinct from heparin
• Use to treat suspected or proven HIT (with/without thrombosis)
  
  • consider when argatroban is contraindicated
• Use to prevent venous thrombosis in patients with a history of HIT 
• No proven reversal agent - if patient bleeds, contact consultant haematologist

Administration

• For patients undergoing dialysis, discuss with haematology
• Check baseline platelet count and APTT

Bolus preparation

• Take 4500 units (3.6 mL of 1250 units/mL) danaparoid sodium injection
  
  • make up to 45 mL in a syringe with sodium chloride 0.9% or glucose 5% = 100 units/mL
• The diluted solution is stable for 24 hr

Dosage

Table 2: Danaparoid dosing for HIT

• Use in HIT is unlicensed. Seek haematology advice before prescribing 
  
  • consider when argatroban contraindicated
• Use to prevent venous thrombosis in patients with a history of HIT 
• Fondaparinux is an indirect anti-Xa inhibitor and has a half-life of 17-20 hr
• Avoid in patients with renal impairment with eGFR <30 mL/min, use argatroban instead
  
  • if eGFR <50 mL/min, discuss with haematologist and renal physician
• Before starting, check baseline platelet count and APTT, renal function
• No proven reversal agent - if patient bleeds, contact consultant haematologist

Fondaparinux dosing for adult patients with HIT

• If body weight <50 kg, give 5 mg SC once daily
• If body weight 50-100 kg, give 7.5 mg SC once daily
• If body weight >100 kg, give 10 mg SC once daily
• If use in patients with renal impairment unavoidable, reduce dose and monitor anti-Xa levels - discuss with haematologist and renal physician

Prevention of VTE in patients with a history of HIT

• Give 2.5 mg SC once daily

Suspected HIT

• Whilst awaiting HIT testing results, consider prophylactic intensity fondaparinux 2.5 mg once daily in patients with suspected HIT with both of:
  
  • an intermediate 4T score (10-15% likelihood of HIT). Scoring tool in HIT guideline
  • high risk of bleeding and no other indication for therapeutic-intensity anticoagulation

• Use in HIT is unlicensed. Seek haematology advice before prescribing
• Bivalirudin is a direct thrombin inhibitor licensed for use in coronary interventions 
  
  • it has a short half-life of 30–40 min which can be prolonged to 3 hr in patients with severe renal impairment
  • for patients with renal impairment, use argatroban
  • elimination of bivalirudin is by enzymic metabolism and renal excretion. No dose adjustment is required for hepatic impairment 
  • there is no known antidote
  • rare cases of anaphylactic reaction have been associated with IV bolus or infusion
• Before starting infusion, obtain baseline platelet count and APTT
• No proven reversal agent - if patient bleeds, contact consultant haematologist

Preparation

• 250 mg powder for reconstitution for injection or infusion

Administration for HIT

• Check baseline platelet count and APTT, renal function
• Reconstitute each 250 mg vial with 5 mL water for injection
  
  • swirl gently until completely dissolved and the solution is clear
• Withdraw 5 mL from the vial, and further dilute to a total volume of 50 mL with glucose 5% or sodium chloride 0.9%
  
  • gives a final concentration of 5 mg/mL
• For HIT, given by intravenous infusion via infusion pump

Dosage for HIT

Table 3: Bivalirudin dosing for HIT for adult patients