ICU Medication MasterclassUFH • LMWH • DTI • DOAC • PCC • Vitamin K • Protamine • Antidotes

Anticoagulation, Hemostasis & Emergency Reversal

Choose anticoagulation by indication, organ function and procedural risk; recognize HIT and major bleeding; reverse only when the clinical problem justifies it; and plan re-initiation once hemostasis is achieved.

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Choose UFH, LMWH, argatroban or bivalirudin according to renal/hepatic function, need for rapid interruption and HIT status.

Separate aPTT/anti-Xa assay problems from true heparin failure.

Match reversal to the actual anticoagulant, timing, bleeding severity and procedural urgency.

Know that factor-Xa reversal access is jurisdiction-specific; U.S. commercial andexanet sales ended in late 2025; the FDA later listed the product as permanently discontinued in January 2026.

Treat restarting anticoagulation as a second high-stakes decision rather than an automatic calendar date.

Major bleeding topic

Resuscitation, source control and hemostatic strategy.

Open →

Core agents

Choose by physiology, not by habit

The table below is a selection framework. Open the individual monograph for exact dosing, preparation, renal/CRRT/IHD adjustment, interactions and evidence traceability.

Unfractionated Heparin

Indirect Anticoagulant — Antithrombin-Dependent Factor IIa & Xa Inhibitor

Core agent

ICU role: Rapidly titratable parenteral anticoagulant with short effective half-life.

Choose: Useful when procedures are likely, renal function is poor/unstable, or rapid titration/reversal matters.

Hesitate: HIT and assay discordance; protamine reversal depends on dose/timing rather than being universally complete.

Monitor: aPTT or anti-Xa per validated local protocol, platelets/HIT assessment, bleeding.

Enoxaparin

Low-Molecular-Weight Heparin (LMWH) — Predominantly Factor Xa Inhibitor

Core agent

ICU role: Predictable LMWH for VTE treatment/prophylaxis and selected ACS indications.

Choose: Convenient when renal function is stable and frequent infusion titration is unnecessary.

Hesitate: Renal accumulation and only partial protamine reversal.

Monitor: Renal function, bleeding; anti-Xa only in selected situations/local protocols.

Argatroban

Direct thrombin inhibitor

Core agent

ICU role: Hepatically cleared direct thrombin inhibitor used commonly for HIT.

Choose: Attractive in HIT with severe renal dysfunction.

Hesitate: Dose reduction in hepatic dysfunction; raises INR and complicates warfarin transition.

Monitor: aPTT/validated DTI assay, hepatic function, INR during transition.

Bivalirudin

Direct thrombin inhibitor

Core agent

ICU role: Direct thrombin inhibitor used in HIT, procedural and extracorporeal settings.

Choose: Useful when rapid on/off DTI is desired and hepatic dysfunction makes argatroban less attractive.

Hesitate: Renal component of clearance; no one DTI is universally best for combined organ failure.

Monitor: aPTT/validated protocol, renal function, circuit/procedural response.

Apixaban

Factor Xa inhibitor

Core agent

ICU role: Oral factor Xa inhibitor for selected VTE/AF indications after acute instability resolves.

Choose: Useful once enteral absorption and clinical stability are reliable and indication allows a DOAC.

Hesitate: Not for mechanical heart valves; acute multiorgan failure/procedural uncertainty makes oral therapy difficult.

Monitor: Renal/hepatic trajectory, interactions, bleeding; timing of last dose.

Rivaroxaban

Factor Xa inhibitor

Core agent

ICU role: Oral factor Xa inhibitor for selected VTE/AF indications.

Choose: Convenient oral therapy in stable patients when indication and organ function fit.

Hesitate: Not for mechanical valves; absorption, renal/hepatic function and urgent procedure planning matter.

Monitor: Renal/hepatic function, interactions, bleeding, last dose.

Warfarin

Vitamin K antagonist

Core agent

ICU role: Vitamin K antagonist required for many mechanical-valve patients and selected long-term indications.

Choose: Essential when DOACs are inappropriate, including mechanical prosthetic valves.

Hesitate: Slow onset/offset, multiple interactions and INR variability in critical illness.

Monitor: INR, diet/drug interactions, bleeding, bridging indication.

4-Factor Prothrombin Complex Concentrate

Hemostatic Agent / Clotting Factor Concentrate

Core agent

ICU role: Concentrated vitamin K-dependent factors for rapid VKA reversal and selected major DOAC bleeding protocols.

Choose: Rapid warfarin reversal with IV vitamin K in life-threatening/critical-site bleeding.

Hesitate: Thrombotic risk; dosing/indication differs by anticoagulant and local protocol.

Monitor: Clinical hemostasis, INR for VKA, thrombotic complications.

Vitamin K (IV)

Essential Coagulation Cofactor / Hemostatic Vitamin

Core agent

ICU role: Restores vitamin K-dependent factor synthesis in warfarin-associated major bleeding.

Choose: Give with PCC for sustained VKA reversal in critical bleeding.

Hesitate: Too slow to be the only urgent therapy in life-threatening warfarin hemorrhage.

Monitor: INR trend, infusion reaction precautions.

Protamine Sulfate

Heparin antagonist

Core agent

ICU role: Heparin-binding reversal agent for UFH and partial LMWH reversal.

Choose: Use when clinically significant heparin effect must be reversed.

Hesitate: Rapid infusion can cause hypotension/bradycardia/pulmonary vasoconstriction; LMWH reversal is incomplete.

Monitor: Hemodynamics during administration and clinical hemostasis.

Idarucizumab

Dabigatran-specific antibody fragment

Core agent

ICU role: Specific dabigatran-binding antidote.

Choose: Life-threatening/uncontrolled bleeding or urgent surgery with clinically relevant dabigatran effect.

Hesitate: Rebound dabigatran can occur in high drug burden/renal failure; does not reverse Xa inhibitors.

Monitor: Clinical hemostasis, renal function, recurrent anticoagulant effect.

Tranexamic Acid

Antifibrinolytic / Synthetic Lysine Analog

Core agent

ICU role: Antifibrinolytic used in selected trauma, postpartum and surgical bleeding contexts.

Choose: Time-sensitive use when the syndrome has evidence for antifibrinolysis.

Hesitate: Not a universal substitute for source control or factor/component replacement.

Monitor: Indication/timing, thrombotic risk, renal function.

Agent	ICU role	Why I choose it	Why I hesitate	What I monitor
Unfractionated Heparin Indirect Anticoagulant — Antithrombin-Dependent Factor IIa & Xa Inhibitor	Rapidly titratable parenteral anticoagulant with short effective half-life.	✓ Useful when procedures are likely, renal function is poor/unstable, or rapid titration/reversal matters.	✕ HIT and assay discordance; protamine reversal depends on dose/timing rather than being universally complete.	aPTT or anti-Xa per validated local protocol, platelets/HIT assessment, bleeding.
Enoxaparin Low-Molecular-Weight Heparin (LMWH) — Predominantly Factor Xa Inhibitor	Predictable LMWH for VTE treatment/prophylaxis and selected ACS indications.	✓ Convenient when renal function is stable and frequent infusion titration is unnecessary.	✕ Renal accumulation and only partial protamine reversal.	Renal function, bleeding; anti-Xa only in selected situations/local protocols.
Argatroban Direct thrombin inhibitor	Hepatically cleared direct thrombin inhibitor used commonly for HIT.	✓ Attractive in HIT with severe renal dysfunction.	✕ Dose reduction in hepatic dysfunction; raises INR and complicates warfarin transition.	aPTT/validated DTI assay, hepatic function, INR during transition.
Bivalirudin Direct thrombin inhibitor	Direct thrombin inhibitor used in HIT, procedural and extracorporeal settings.	✓ Useful when rapid on/off DTI is desired and hepatic dysfunction makes argatroban less attractive.	✕ Renal component of clearance; no one DTI is universally best for combined organ failure.	aPTT/validated protocol, renal function, circuit/procedural response.
Apixaban Factor Xa inhibitor	Oral factor Xa inhibitor for selected VTE/AF indications after acute instability resolves.	✓ Useful once enteral absorption and clinical stability are reliable and indication allows a DOAC.	✕ Not for mechanical heart valves; acute multiorgan failure/procedural uncertainty makes oral therapy difficult.	Renal/hepatic trajectory, interactions, bleeding; timing of last dose.
Rivaroxaban Factor Xa inhibitor	Oral factor Xa inhibitor for selected VTE/AF indications.	✓ Convenient oral therapy in stable patients when indication and organ function fit.	✕ Not for mechanical valves; absorption, renal/hepatic function and urgent procedure planning matter.	Renal/hepatic function, interactions, bleeding, last dose.
Warfarin Vitamin K antagonist	Vitamin K antagonist required for many mechanical-valve patients and selected long-term indications.	✓ Essential when DOACs are inappropriate, including mechanical prosthetic valves.	✕ Slow onset/offset, multiple interactions and INR variability in critical illness.	INR, diet/drug interactions, bleeding, bridging indication.
4-Factor Prothrombin Complex Concentrate Hemostatic Agent / Clotting Factor Concentrate	Concentrated vitamin K-dependent factors for rapid VKA reversal and selected major DOAC bleeding protocols.	✓ Rapid warfarin reversal with IV vitamin K in life-threatening/critical-site bleeding.	✕ Thrombotic risk; dosing/indication differs by anticoagulant and local protocol.	Clinical hemostasis, INR for VKA, thrombotic complications.
Vitamin K (IV) Essential Coagulation Cofactor / Hemostatic Vitamin	Restores vitamin K-dependent factor synthesis in warfarin-associated major bleeding.	✓ Give with PCC for sustained VKA reversal in critical bleeding.	✕ Too slow to be the only urgent therapy in life-threatening warfarin hemorrhage.	INR trend, infusion reaction precautions.
Protamine Sulfate Heparin antagonist	Heparin-binding reversal agent for UFH and partial LMWH reversal.	✓ Use when clinically significant heparin effect must be reversed.	✕ Rapid infusion can cause hypotension/bradycardia/pulmonary vasoconstriction; LMWH reversal is incomplete.	Hemodynamics during administration and clinical hemostasis.
Idarucizumab Dabigatran-specific antibody fragment	Specific dabigatran-binding antidote.	✓ Life-threatening/uncontrolled bleeding or urgent surgery with clinically relevant dabigatran effect.	✕ Rebound dabigatran can occur in high drug burden/renal failure; does not reverse Xa inhibitors.	Clinical hemostasis, renal function, recurrent anticoagulant effect.
Tranexamic Acid Antifibrinolytic / Synthetic Lysine Analog	Antifibrinolytic used in selected trauma, postpartum and surgical bleeding contexts.	✓ Time-sensitive use when the syndrome has evidence for antifibrinolysis.	✕ Not a universal substitute for source control or factor/component replacement.	Indication/timing, thrombotic risk, renal function.

Clinical decision matrix

What changes the drug choice?

Acute VTE + severe AKI + likely procedure

Preferred reasoning: UFH is often practical because it is titratable and can be interrupted rapidly.

Avoid: Assuming a DOAC is automatically easiest in an unstable patient with changing renal function and procedures.

Why: The best anticoagulant is the one whose kinetics fit the next 24–48 hours, not only the long-term indication.

Suspected HIT

Preferred reasoning: Stop all heparin exposure and use a non-heparin anticoagulant when indicated; choose argatroban/bivalirudin by organ function and context.

Avoid: Switching from UFH to LMWH or waiting for confirmatory testing in a high-probability, thrombosis-risk situation.

Why: HIT is a prothrombotic immune syndrome, not simply a low-platelet bleeding disorder.

Mechanical mitral valve

Preferred reasoning: Warfarin remains the chronic anticoagulant standard; parenteral bridging decisions depend on thrombotic/bleeding context.

Avoid: Apixaban/rivaroxaban as a convenient substitute for mechanical-valve anticoagulation.

Why: DOAC evidence does not support mechanical prosthetic valves.

Life-threatening warfarin bleeding

Preferred reasoning: 4-factor PCC plus IV vitamin K, alongside source control/resuscitation.

Avoid: Vitamin K alone when immediate factor replacement is needed.

Why: PCC provides rapid factors; vitamin K sustains reversal as new factors are synthesized.

Life-threatening dabigatran bleeding

Preferred reasoning: Idarucizumab when relevant drug effect is present; dialysis is an additional option in selected severe accumulation.

Avoid: Using a Xa-specific strategy for a direct thrombin inhibitor.

Why: Reversal must match the drug class and pharmacokinetics.

Life-threatening apixaban/rivaroxaban bleeding

Preferred reasoning: Use the institution's current factor-Xa reversal pathway; PCC remains widely used where a specific Xa antidote is unavailable, and local regulatory availability must be checked.

Avoid: Teaching andexanet as universally available in 2026.

Why: U.S. commercial andexanet sales ended in December 2025; availability/regulatory status differs across jurisdictions.

Organ failure & special settings

When standard pharmacology stops being standard

Renal failure

Priority: Favor agents whose clearance/titration profile fits the indication; UFH/argatroban may be easier than renally accumulating options in unstable kidney function.

Pitfall: Applying a fixed dose to rapidly changing AKI without reassessment.

Hepatic failure

Priority: Recognize argatroban and warfarin complexity; distinguish drug effect from baseline coagulopathy.

Pitfall: Using INR alone to infer bleeding risk or warfarin intensity in severe liver dysfunction.

ECMO / CRRT

Priority: Use circuit-specific anticoagulation protocols and validated assays; bivalirudin/argatroban may be used when HIT or heparin limitations exist.

Pitfall: Assuming the same target/assay applies across all circuits and devices.

Intracranial hemorrhage

Priority: Reverse clinically relevant anticoagulant effect rapidly while controlling BP and involving neurosurgical/stroke teams.

Pitfall: Delaying reversal for a nonessential confirmatory test when the drug/timing and critical bleed are clear.

Restart after major bleeding

Priority: Balance re-bleeding anatomy/control against thrombosis indication; mechanical valve, recent VTE and AF carry different urgency.

Pitfall: Using one universal restart day for every indication and bleeding site.

Resident progression

R1 → R5 bedside cases

Recognition becomes selection, then organ-failure adjustment, competing physiology and senior-level prioritization.

Warfarin reversal

A patient on warfarin has life-threatening intracranial bleeding and INR 4.6.

Show reasoning

Use rapid factor replacement with 4-factor PCC plus IV vitamin K, alongside hemorrhage-specific care. Vitamin K alone is too slow for immediate hemostatic correction.

Heparin in AKI

A patient with acute PE has CrCl 18 mL/min, a planned invasive procedure tomorrow and no HIT history.

Show reasoning

UFH is often the practical acute choice because it can be titrated and interrupted rapidly; monitor with the institution's validated aPTT/anti-Xa strategy.

HIT with renal failure

Platelets fall >50% five days after heparin and a new DVT appears. The patient is dialysis-dependent with preserved liver function.

Show reasoning

Stop all heparin and initiate a non-heparin anticoagulant when clinically indicated; argatroban is attractive in severe renal failure because clearance is hepatic. Send confirmatory testing without delaying appropriate therapy in a high-probability case.

Factor Xa inhibitor ICH in 2026

A patient on apixaban presents with a large spontaneous ICH 3 hours after the last dose. A trainee suggests andexanet because an old poster lists it as standard.

Show reasoning

Use the current local factor-Xa reversal pathway and verify regulatory/formulary availability. In the U.S., andexanet commercial sales ended in late 2025; 4F-PCC is commonly used when a specific antidote is unavailable. Do not delay hemorrhage control while debating an unavailable product.

Restart after controlled GI bleed

A patient with recent high-risk PE has endoscopically controlled GI bleeding. Hemoglobin is stable but thrombosis risk remains high.

Show reasoning

Restart timing is individualized: confirm durable hemostasis, reassess anatomy/rebleeding risk and weigh the high-risk VTE indication. The correct plan is not 'never restart' or a fixed calendar day detached from the patient's competing risks.

Full medication monograph

Unfractionated Heparin

Antithrombin-dependent anticoagulant with factor IIa and Xa inhibition. Its immediate IV onset, short titratable effect and protamine reversibility are useful when rapid control is important, but LMWH is preferred over UFH for mo…

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Enoxaparin

Depolymerized derivative of unfractionated heparin with predominantly anti-Xa activity — predictable, weight-based subcutaneous dosing without routine monitoring in most patients, but renally cleared and only partially reversible…

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Argatroban

Short-acting IV anticoagulant used particularly for HIT when renal failure makes renally cleared alternatives less attractive.

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Bivalirudin

Short-acting parenteral thrombin inhibitor used in PCI and selected HIT/ECMO/MCS settings with institution-specific monitoring.

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Apixaban

Oral factor Xa inhibitor frequently encountered in ICU bleeding, urgent procedures, AF and VTE.

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Rivaroxaban

Once-daily factor Xa inhibitor after VTE lead-in; important ICU issues include renal function, food-dependent absorption at higher doses and bleeding reversal.

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Warfarin

Oral vitamin K antagonist with delayed onset/offset, extensive interactions and a central role in mechanical-valve anticoagulation.

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

4-Factor Prothrombin Complex Concentrate

Lyophilized concentrate of vitamin K-dependent coagulation factors used for urgent reversal of vitamin K antagonist anticoagulation in adults with major bleeding or urgent surgery/invasive procedures; it rapidly replaces deficien…

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Vitamin K (IV)

Parenteral fat-soluble vitamin essential for post-translational gamma-carboxylation of clotting factors II, VII, IX, and X in the liver, providing sustained endogenous factor regeneration during warfarin reversal and severe coagu…

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Protamine Sulfate

Cationic antidote that neutralizes UFH and partially reverses LMWH; excessive protamine itself can impair coagulation.

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Idarucizumab

Specific dabigatran reversal agent for life-threatening/uncontrolled bleeding or urgent surgery when clinically significant dabigatran effect is present.

Dosing • renal/CRRT • toxicity • interactions →

Full medication monograph

Tranexamic Acid

Synthetic lysine analog that competitively blocks plasminogen lysine-binding sites, inhibiting plasmin formation and fibrin clot degradation, reducing mortality in bleeding trauma (CRASH-2) and postpartum hemorrhage (WOMAN) when …

Dosing • renal/CRRT • toxicity • interactions →

Evidence & bedside-use boundary

This Masterclass teaches selection and reasoning. Exact dosing, concentration, infusion preparation, renal/hepatic/RRT adjustment and monitoring must be checked in the linked medication monograph and the institution's current formulary/protocol. Local resistance patterns and regulatory drug availability can change faster than a static teaching page.

FDA — Update on ANDEXXA safety and availability

U.S. commercial sales ended after December 2025; local availability must be verified.