Anticoagulation and antiplatelets

10 min read Last updated April 8, 2026

Surgical approach (context: perioperative handling of anticoagulants/antiplatelets)

  • Surgeon defines urgency and bleeding consequence of the procedure
    • Elective: can delay to allow drug washout / optimise haemostasis
    • Urgent (hours–days): may proceed with mitigation (local measures, blood products, reversal where appropriate)
    • Emergency (immediate): proceed; focus on haemostatic resuscitation and targeted reversal
  • Local haemostatic strategies
    • Meticulous surgical technique, diathermy, topical haemostats, tourniquet where appropriate
    • Drain use and timing of restart of anticoagulation discussed with anaesthesia/haematology
  • Thrombotic-risk considerations
    • Recent coronary stent / ACS: surgeon often prefers to continue antiplatelet therapy if bleeding risk acceptable
    • Mechanical valve / recent VTE: surgeon accepts bridging or perioperative heparinisation if feasible

Anaesthetic management (generic perioperative plan)

  • Type of anaesthesia
    • GA commonly used when anticoagulated/high bleeding risk or when neuraxial unsafe
    • Regional/neuraxial possible only if drug-specific timing and coagulation criteria met (follow ASRA/ESAIC/local policy)
    • Peripheral nerve blocks: generally lower risk than neuraxial but deep non-compressible blocks follow neuraxial-type precautions
  • Airway
    • ETT often preferred for major surgery/anticipated bleeding/need for controlled ventilation
    • SGA acceptable for minor procedures if aspiration risk low and bleeding not expected
  • Duration
    • Procedure-dependent; plan for delays if reversal/blood products required
  • Analgesia / pain
    • Neuraxial opioids/epidural may be contraindicated; consider multimodal systemic analgesia and peripheral blocks where safe
    • Avoid NSAIDs in high bleeding risk or when combined with anticoagulants/antiplatelets unless clear benefit and acceptable risk
  • Haemostasis plan
    • Early communication with surgeon/haematology; group & save/crossmatch; consider viscoelastic testing (TEG/ROTEM) in major bleeding
    • Have reversal agents available where indicated (vitamin K, PCC, protamine, idarucizumab, andexanet/4F-PCC pathways)

Core principles

  • Balance bleeding risk vs thrombotic risk; document shared decision-making
  • Define procedure bleeding risk: minimal / low / high / critical-site (intracranial, spinal, posterior eye, major vascular)
  • Define patient thrombotic risk: indication and timing (e.g. VTE <3 months, mechanical valve, AF with high CHA2DS2-VASc, recent stent)
  • Know drug class, half-life, renal/hepatic clearance, monitoring tests, and reversal options

Antiplatelet drugs

  • Aspirin (COX-1 inhibitor): irreversibly inhibits platelet TXA2; effect lasts platelet lifespan (~7–10 days)
    • Often continued for many surgeries; stop 5–7 days pre-op for high bleeding risk/critical-site surgery if thrombotic risk acceptable
    • Reversal: platelet transfusion (limited evidence; more effective if aspirin-only and last dose >2 hours), consider DDAVP in selected bleeding
  • P2Y12 inhibitors: clopidogrel, prasugrel (irreversible), ticagrelor (reversible)
    • Typical elective stop times: clopidogrel 5 days; prasugrel 7 days; ticagrelor 3–5 days (local policy varies)
    • Bleeding management: local measures, tranexamic acid, platelet transfusion (less effective for ticagrelor), consider DDAVP; involve cardiology if recent stent
  • GPIIb/IIIa inhibitors (abciximab, eptifibatide, tirofiban): potent IV antiplatelets used in PCI
    • Hold times (approx): abciximab 24–48 h; eptifibatide/tirofiban 4–8 h (renal function affects)
  • Dipyridamole: weak antiplatelet; usually continue; may stop 24 h if high bleeding risk
  • Dual antiplatelet therapy (DAPT) after stent/ACS
    • High thrombosis risk early after stent; elective surgery ideally delayed (discuss with cardiology) and continue aspirin if possible
    • If P2Y12 must be stopped: minimise interruption; restart ASAP post-op when haemostasis secure; consider bridging strategies only with specialist input

Anticoagulants: heparins and fondaparinux

  • Unfractionated heparin (UFH): potentiates antithrombin → inhibits IIa and Xa; short half-life; monitor APTT/anti-Xa
    • Reversal: protamine (approx 1 mg per 100 units heparin given in last 2–3 h; max commonly 50 mg; risk hypotension/anaphylactoid)
    • Neuraxial: ensure normal coagulation; follow timing for infusion cessation (commonly 4–6 h) and check APTT/anti-Xa per policy
  • Low molecular weight heparin (LMWH): predominantly anti-Xa; predictable dose-response; monitor anti-Xa in extremes (renal failure, pregnancy, obesity)
    • Prophylactic vs therapeutic dosing matters for neuraxial timing and bleeding risk
    • Reversal: protamine partially reverses (more effective for anti-IIa than anti-Xa); consider PCC only with specialist advice
  • Fondaparinux: synthetic pentasaccharide anti-Xa; long half-life; no specific reversal; neuraxial generally avoided
    • If bleeding: supportive, consider PCC/activated PCC on specialist advice; dialysis ineffective

Anticoagulants: vitamin K antagonists (warfarin)

  • Mechanism: inhibits vitamin K epoxide reductase → reduced II, VII, IX, X (and proteins C/S); monitor INR
  • Elective surgery: stop ~5 days pre-op; check INR pre-op (target often <1.5 for major surgery; neuraxial typically requires INR within normal range per policy)
  • Reversal options (choose based on urgency and bleeding)
    • Vitamin K (IV for faster, oral for non-urgent): onset hours; risk anaphylactoid rare with slow IV
    • 4-factor PCC: rapid reversal (minutes); dose guided by INR/weight and local protocol; thrombosis risk
    • FFP: larger volumes, slower; use if PCC unavailable or for additional factor replacement in massive haemorrhage
  • Bridging: only for high thrombotic risk (e.g. mechanical mitral valve, recent VTE, very high-risk AF); use LMWH/UFH under protocol

Anticoagulants: DOACs (direct oral anticoagulants)

  • Drugs: dabigatran (direct thrombin inhibitor); apixaban/rivaroxaban/edoxaban (direct Xa inhibitors)
  • Key determinants of stop time: renal function, bleeding risk of surgery, and whether neuraxial/deep blocks planned
  • Monitoring: routine coag tests unreliable; consider drug-specific assays if available
    • Dabigatran: thrombin time very sensitive (if normal, little/no drug); diluted thrombin time/ecarin clotting time quantify
    • Xa inhibitors: anti-Xa calibrated to specific drug (best); PT may be variably prolonged (esp rivaroxaban) but not reliable
  • Reversal
    • Dabigatran: idarucizumab 5 g IV (2 × 2.5 g) for life-threatening bleeding/urgent surgery; dialysis can remove dabigatran
    • Xa inhibitors: andexanet alfa where available for life-threatening bleeding (local criteria); otherwise 4F-PCC often used off-label per protocol
    • Adjuncts: tranexamic acid, local haemostasis, maintain fibrinogen/platelets, correct hypocalcaemia/acidosis/hypothermia
  • Bridging: generally not required for DOACs due to short half-life; consider only in exceptional high-risk scenarios with specialist input

Neuraxial and regional anaesthesia: practical safety points

  • Assess: drug(s), last dose time, renal function, platelet count/function, coagulation tests where relevant, and concurrent antiplatelets/NSAIDs
  • High-risk situations: therapeutic anticoagulation, multiple agents (e.g. DOAC + antiplatelet), traumatic needle placement, indwelling catheter with anticoagulation
  • If neuraxial performed: minimise attempts, use experienced operator, document timing, and plan anticoagulant restart and catheter removal timing explicitly
  • Suspected neuraxial haematoma: new back pain, motor weakness, sensory changes, sphincter disturbance
    • Emergency: stop anticoagulants, urgent MRI, immediate neurosurgical/spinal referral; decompression ideally within 8–12 hours of symptom onset

Perioperative restart (general approach)

  • Restart when surgical haemostasis secure and bleeding risk acceptable; coordinate with surgeon and consider drains/epidural catheters
  • High thrombotic risk: consider earlier restart or interim prophylactic dosing; individualise
  • Neuraxial catheter: ensure safe interval between last anticoagulant dose and catheter removal; delay next dose after removal per policy

Major bleeding on anticoagulants/antiplatelets (structured response)

  • Resuscitate: ABC, large-bore access, activate major haemorrhage protocol early, maintain temperature and ionised calcium
  • Stop anticoagulant/antiplatelet; identify agent and timing; send labs (FBC, PT/INR, APTT, fibrinogen) and consider TEG/ROTEM
  • Give targeted reversal: protamine (heparin), vitamin K + PCC (warfarin), idarucizumab (dabigatran), andexanet/4F-PCC (Xa inhibitors per protocol)
  • Adjunct haemostatic therapy: tranexamic acid early; maintain fibrinogen (cryoprecipitate/fibrinogen concentrate) and platelets
You are asked to anaesthetise a patient on warfarin for AF for an urgent laparotomy. How do you assess and manage anticoagulation?

Structure: urgency + bleeding risk → INR and indication → reversal plan → postoperative restart.

  • Clarify urgency and bleeding consequence; discuss with surgeon whether delay is possible
  • Assess thrombotic risk: AF (CHA2DS2-VASc), prior stroke/TIA, mechanical valve? recent VTE?
  • Check INR and baseline labs (FBC, fibrinogen, U&E/LFT); ensure blood available
  • If urgent surgery with elevated INR: reverse with 4F-PCC + IV vitamin K (dose per INR/weight protocol); consider FFP if PCC unavailable
  • If bleeding/massive haemorrhage: activate MHP, use TXA, correct hypocalcaemia/hypothermia/acidosis
  • Post-op: restart anticoagulation when haemostasis secure; consider prophylactic LMWH initially; bridging only if very high thrombotic risk
A patient on apixaban requires emergency surgery. What tests help and what reversal options exist?

Focus on timing, renal function, limited utility of routine coag tests, and protocolised reversal.

  • History: last dose time, dose, renal function, interacting drugs; assess bleeding vs thrombotic risk
  • Tests: PT/APTT may be normal despite clinically relevant drug; best is drug-calibrated anti-Xa level if available
  • If life-threatening bleeding/urgent surgery: consider andexanet alfa (where available/criteria met) OR 4F-PCC per local guideline
  • Adjuncts: TXA, local haemostasis, maintain fibrinogen/platelets; avoid neuraxial unless safe interval and policy met
Outline perioperative management of dual antiplatelet therapy in a patient with a recent coronary stent needing non-cardiac surgery.

Key is stent thrombosis risk and cardiology involvement.

  • Identify stent type and timing since PCI/ACS; early period = high risk of stent thrombosis
  • If elective and high bleeding risk surgery: delay surgery if possible after discussion with cardiology/surgeon
  • If surgery must proceed: usually continue aspirin; stop P2Y12 inhibitor for minimum recommended time if bleeding risk mandates (clopidogrel 5 d, prasugrel 7 d, ticagrelor 3–5 d)
  • Plan for haemostasis: TXA, blood availability; avoid neuraxial if on P2Y12 inhibitor within stop window
  • Restart P2Y12 inhibitor ASAP post-op once haemostasis secure; document plan and monitor for cardiac ischaemia
How do you reverse warfarin in (a) non-bleeding patient needing surgery tomorrow, (b) life-threatening intracranial haemorrhage?

Differentiate urgency and target speed of reversal.

  • (a) Surgery tomorrow, not bleeding: stop warfarin; give oral or low-dose IV vitamin K if INR needs correction; recheck INR
  • (b) Life-threatening ICH: immediate 4F-PCC + IV vitamin K; aim rapid normalisation of INR; manage BP and neurosurgical pathway
  • FFP if PCC unavailable or as part of massive transfusion; consider fibrinogen/platelets as indicated
Describe protamine: mechanism, dosing, adverse effects, and use in heparin reversal.

Common FRCA viva topic.

  • Mechanism: basic polypeptide binds acidic heparin to form inactive complex
  • Dosing: approximate 1 mg protamine per 100 units UFH given in preceding 2–3 hours (titrate to ACT/APTT where used); max dose often 50 mg (local)
  • LMWH: partial reversal only; effect on anti-Xa limited
  • Adverse effects: hypotension/bradycardia (rapid infusion), anaphylactoid reactions, pulmonary hypertension; higher risk with prior exposure, vasectomy, fish allergy (association), NPH insulin use
A patient on therapeutic LMWH has an epidural catheter in situ. What are your concerns and how do you manage timing of doses and catheter removal?

Answer should emphasise neuraxial haematoma risk and strict timing.

  • High risk of neuraxial haematoma with therapeutic anticoagulation + indwelling catheter; avoid therapeutic dosing with catheter in place where possible
  • Follow local/ASRA/ESAIC timing: ensure adequate interval from last LMWH dose before catheter removal; delay next dose after removal
  • Monitor neurological status regularly; educate staff/patient to report back pain, weakness, numbness, bladder/bowel dysfunction
  • If symptoms: stop anticoagulation, urgent MRI, urgent spinal/neurosurgical referral (time-critical decompression)
What is the difference between antiplatelet drugs and anticoagulants? Give examples and typical perioperative implications.

Define primary haemostasis vs coagulation cascade and relate to monitoring/reversal.

  • Antiplatelets inhibit platelet activation/aggregation (primary haemostasis): aspirin, clopidogrel, ticagrelor, prasugrel
  • Anticoagulants inhibit coagulation factors (secondary haemostasis): warfarin, UFH/LMWH, DOACs
  • Implications: neuraxial timing differs; monitoring differs (INR for warfarin; APTT for UFH; anti-Xa for LMWH/Xa inhibitors); reversal differs (PCC/vit K vs protamine vs specific antidotes)
A patient on dabigatran needs urgent surgery. How do you assess residual anticoagulant effect and reverse it?

Key points: renal clearance, thrombin time, idarucizumab, dialysis.

  • Assess last dose and renal function (dabigatran accumulates in renal impairment)
  • Tests: thrombin time (very sensitive); if normal, minimal dabigatran effect; consider diluted thrombin time/ecarin clotting time if available
  • Reversal for life-threatening bleeding/urgent surgery: idarucizumab 5 g IV
  • Consider haemodialysis if severe bleeding with renal failure or rebound; adjunct TXA and supportive haemostasis
How would you manage a patient on clopidogrel who requires a spinal anaesthetic for hip fracture surgery?

This is a common FRCA scenario: weigh urgency vs neuraxial bleeding risk; consider alternative anaesthesia.

  • Determine last clopidogrel dose and indication (e.g. recent stent/ACS vs stroke prevention) and urgency of surgery
  • Neuraxial generally avoided unless appropriate stop interval achieved (commonly 5 days for clopidogrel) and no additional coagulopathy
  • Offer GA ± peripheral nerve blocks (e.g. fascia iliaca) where safe; consider deep blocks with neuraxial-like precautions
  • If neuraxial is being considered despite recent clopidogrel: senior discussion, document risk, consider alternative plan; platelet function testing is not a universal substitute for recommended stop times
Explain bridging anticoagulation: who needs it, what drugs are used, and what are the risks?

Examiners want: bridging is not routine; it increases bleeding; reserve for high thrombotic risk.

  • Definition: temporary perioperative substitution of long-acting anticoagulant (e.g. warfarin) with short-acting agent (LMWH/UFH)
  • Indications (examples): mechanical mitral valve, recent VTE (<3 months), very high-risk AF (e.g. recent stroke/TIA) — follow local/cardiology/haematology guidance
  • Agents: therapeutic LMWH or IV UFH (UFH useful when rapid offset needed or renal failure)
  • Risks: increased perioperative bleeding, neuraxial haematoma risk if regional techniques used, heparin-induced thrombocytopenia (UFH>LMWH)

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