Whiteboard HIT

HIT characteristics

• Prothrombotic disorder

• 50% platelet drop or less than 100,000 platelet count

• 5-14 days after starting heparin

What is HIT related to?

30-50% related arterial &/or venous thromboembolism.

HIT MOA

• Pt’s who form antibodies against Heparin & PF4 complex causing platelet activation leading to clumping & eventual clot

Which type of Heparin is worse?

Bovine lung worse than porcine

HIT epidemiology

• More prevalent in females than males

• Mortality rate up to 30%

• 20% untreated undergo single or multiple amputations

Methods to detect HIT

• Immunoassay - detects binding of anti-PF4 heparin antibodies

• Functional Assay - platelet activation tests

Types of functional assays

Activate platelets in the presence of heparin

• Serotonin Release Assay (SRA)

• Heparin induced platelet activation (HIPA)

Acute HIT characteristics

• Persists until platelets recover

• Functional & immunoassay Positive

• ↓ platelet count

Subacute A HIT characteristics

• Period of platelet recovery

• Functional assay still positive

Subacute A HIT Treatment plan

• Delay surgery

• Use Heparin alternative

• Pre-op plasma exchange

Subacute B HIT characteristics

• Platelets recovered

• Immunoassay still Positive

Subacute B HIT Treatment plan

Use Heparin (Porcine preferred)

Remote HIT

• Anti-PF4/heparin antibodies no longer detectable

• Treatment plan: Use Heparin

Heparin alternatives

• Bivalrudin (Angiomax)

  • Most common

• Argatroban (Acova)

  • Use for renal dysfunction pt’s

DTI’s

Bivalrudin Suggested protocol

• 25 min ½ life

• Bolus 50 mg in prime

• Pt loading dose 1 mg/kg by anesthesia

• Continuous infusion 2.5 mg/kg/hr by anesthesia

ATS for HIT

• All shed blood to cell saver (no pump sucker usage)

• Use anticoagulant CPD (Citrate Phosphate Dextrose)

Prolonged R-value

• Hypocoagulable state

• Possible d/t heparin presence or ↓ coagulation factors

• Treat w/ FFP or protamine

DEC’d R-value

Hypercoagulable state

K-value meaning

• Fibrin contribution to clot strength

• Speed of clot formation

Prolonged K-value

• Fibrinogen deficiency

• Treat w/ Cryoprecipitate

R-value meaning

• Time of formation of fibrin strand polymer

• Time it takes for clotting to begin (similar to ACT)

MA meaning

Clot strength / platelet function

DEC’d MA value

• Lower platelet levels

• Treat w/ platelets or DDAVP

LY 30 meaning

Clot breakdown / fibrinolysis 30 min after MA

DEC’d LY 30 value

• Rapid consumption

• Treat w/ TXA

Brandy Snifter

Normal / Do nothing

Wine glass

• Factor deficiency

• Give FFP

Champagne flute

• Fibrinogen deficiency

• Give Cryo/fibrinogen

Test tube

• Thrombocytopenia

• Give platelets

Inverted Martini glass

• Fibrinolysis

• Give TXA

Heparin Assay Device Medtronic HMS Plus

• Calculates estimated heparin dosage

• Measures circulating level of Heparin

• Calculates protamine dosage based on circulating heparin level

• Detects residual heparin post protamine

#1 cause of clotted circuits

Protamine

Insufficient ACT

• Give more Heparin

• AT III for heparin resistance

• Use of FFP

Heparin Resistance causes

• Previous use of Heparin

• Pregnancy

• Shock

• AT III deficiency

• Infective endocarditis

Less frequent Clotted circuit causes

• Recalcification of blood prime before adding heparin

• Platelet fibrination of oxy

False clotted circuit conditions

• HPE

• Cold agglutinins

Cold agglutinins

• Circulating autoantibodies

• Activate at a certain hypothermia level

HPE

• W/in several min of CPB onset, pre oxy pressure INC’s

• Flow drops w/ no RPM change

HPE causes

• Lipid, Protein, Platelet aggregation in oxy fibers

• Associated w/ Diprivan usage (Lipid based drug)

• Not using Albumin in pump prime

HPE treatment

• Warm pt

• Give at least 10 mL of 25% Albumin

Clotted circuit Remediation

Safely & rapidly change out the circuit (assume clot is elsewhere)