# Preprocedural Assessment: Anticoagulation and Coagulation Management

## Introduction

Interventional radiology procedures span a wide range of bleeding and thrombotic risks. Proper **preprocedural assessment** of the patient's coagulation status and thoughtful management of **anticoagulant and antiplatelet therapies** are essential to minimize both hemorrhagic and thromboembolic complications. The SIR consensus guidelines provide a framework for stratifying procedures and managing medications.

## SIR Procedure Bleeding Risk Classification

| SIR Category | Bleeding Risk | Example Procedures | INR Threshold | Platelet Threshold |
|-------------|---------------|-------------------|---------------|-------------------|
| 1 | Low | PICC, port, tunneled catheter, thoracentesis, paracentesis, IVC filter | <2.0 | >20,000/mcL |
| 2 | Moderate | Angioplasty/stent, chemoembolization, nephrostomy, biliary drainage | <1.5 | >50,000/mcL |
| 3 | High | Renal biopsy, hepatic biopsy, complex ablation | <1.5 | >50,000/mcL (hold all anticoagulants) |

### Category 1 (Low Bleeding Risk)

Venous access (PICC, port, tunneled catheter). Drainage catheter exchange, thoracentesis, paracentesis. IVC filter placement or retrieval. **Coagulation parameters**: INR < 2.0, platelets > 20,000/mcL.

### Category 2 (Moderate Bleeding Risk)

Arterial interventions (angioplasty, stent placement). Chemoembolization, bland embolization. Percutaneous nephrostomy, biliary drainage. Tunneled dialysis catheter placement. **Coagulation parameters**: INR < 1.5, platelets > 50,000/mcL.

### Category 3 (High Bleeding Risk)

Renal biopsy, hepatic biopsy (transjugular may reduce risk). Percutaneous nephrolithotomy. Complex ablation procedures. **Coagulation parameters**: INR < 1.5, platelets > 50,000/mcL; hold all anticoagulants.

![SIR bleeding risk category classification](images/sir-bleeding-risk-categories.png)

## Preprocedural Laboratory Assessment

### Standard Laboratories

**INR/PT**: assess warfarin effect and synthetic liver function. **aPTT**: assess heparin effect and intrinsic pathway. **Platelet count**: minimum thresholds vary by procedure category. **Hemoglobin/Hematocrit**: baseline for comparison if post-procedural bleeding. **Creatinine/eGFR**: assess renal function for contrast planning and medication dosing.

### When to Check Labs

INR and platelets for Category 2 and 3 procedures. Within **24-48 hours** of the procedure for reliability. Category 1 procedures in patients on stable anticoagulation may not require routine labs if recent values are available. Patients with liver disease, renal disease, or hematologic disorders require more comprehensive assessment.

## Anticoagulant Management

### Warfarin

**Category 1 procedures**: may proceed with INR < 2.0-3.0 depending on institutional protocol. **Category 2-3 procedures**: hold warfarin **5 days** before the procedure; check INR day of procedure. **Bridging anticoagulation** with LMWH or UFH for high thromboembolic risk patients (mechanical heart valve, recent VTE < 3 months, high CHA2DS2-VASc). **Reversal**: vitamin K (oral or IV for non-emergent correction), 4-factor PCC for emergent reversal.

### Direct Oral Anticoagulants (DOACs)

| DOAC | Hold Time (Cat 2-3) | Renal Adjustment | Reversal Agent |
|------|---------------------|------------------|----------------|
| Apixaban (Eliquis) | 48 hours | Longer if CrCl <30 | Andexanet alfa (Andexxa) |
| Rivaroxaban (Xarelto) | 48 hours | Longer if CrCl <30 | Andexanet alfa (Andexxa) |
| Dabigatran (Pradaxa) | 48-72 hours | Longer if CrCl <50 | Idarucizumab (Praxbind) |
| Edoxaban (Savaysa) | 48 hours | Longer if CrCl <30 | Andexanet alfa (Andexxa) |

**Apixaban, rivarelbaan**: hold **48 hours** before Category 2-3 procedures (longer if CrCl < 30 mL/min). **Dabigatran**: hold **48-72 hours** (longer with renal impairment); specific reversal agent **idarucizumab (Praxbind)**. **Edoxaban**: hold **48 hours**. DOACs have **shorter half-lives** than warfarin; bridging is generally not required. Reversal agent for factor Xa inhibitors: **andexanet alfa (Andexxa)** for life-threatening bleeding.

### Heparin

**Unfractionated heparin (UFH) infusion**: hold **4-6 hours** before procedure; check aPTT. **Low-molecular-weight heparin (LMWH)**: hold **24 hours** before procedure (therapeutic dose); 12 hours for prophylactic dose. Reversal: **protamine sulfate** (partially effective for LMWH).

## Antiplatelet Management

### Aspirin

**Category 1-2 procedures**: generally continue aspirin. **Category 3 procedures**: consider holding **5-7 days** before procedure. Aspirin for secondary cardiovascular prevention should ideally be continued to reduce cardiac events.

### P2Y12 Inhibitors (Clopidogrel, Prasugrel, Ticagrelor)

**Clopidogrel**: hold **5 days** before Category 2-3 procedures. **Prasugrel**: hold **7 days**. **Ticagrelor**: hold **5 days**. **Critical consideration**: patients with recent coronary stent placement (< 6 months for drug-eluting stents) should not have P2Y12 inhibitors interrupted without cardiology consultation due to risk of **stent thrombosis**. Dual antiplatelet therapy (DAPT) interruption decisions require multidisciplinary discussion.

### Dual Antiplatelet Therapy After Stent Placement

**Bare metal stent**: minimum 4 weeks of DAPT before elective interruption. **Drug-eluting stent**: minimum 6 months (ideally 12 months) of DAPT. If the procedure cannot wait, consider performing under DAPT with awareness of increased bleeding risk. **Never stop both antiplatelet agents simultaneously** in stented patients.

![Anticoagulant and antiplatelet periprocedural management timeline](images/periprocedural-medication-mgmt.png)

## Special Populations

### Liver Disease

INR elevation in cirrhosis reflects decreased synthesis but **does not accurately predict bleeding risk**. Cirrhotic patients have a **rebalanced hemostasis**; both bleeding and thrombotic risk are elevated. Standard INR targets may not apply; thromboelastography (TEG/ROTEM) may better guide management. **Transjugular approach** for liver biopsy reduces bleeding risk compared to percutaneous.

### Renal Disease

Uremic platelet dysfunction impairs hemostasis; platelet count may be normal. **Desmopressin (DDAVP)**: 0.3 mcg/kg IV before the procedure to improve platelet function. Consider dialysis before the procedure to reduce uremic toxins.

### Thrombocytopenia

**Platelet transfusion** to achieve appropriate threshold before the procedure. Platelets > 20,000 for Category 1; > 50,000 for Category 2-3. In ITP, transfused platelets are rapidly consumed; consider TPO receptor agonists preprocedurally.

## Post-Procedural Anticoagulation Resumption

**Category 1**: resume anticoagulation **same day** or next morning. **Category 2**: resume **24-48 hours** after the procedure if no bleeding complications. **Category 3**: resume **48-72 hours** after the procedure. **DOACs** reach therapeutic levels within 2-4 hours of dosing; delay resumption accordingly. Warfarin may be restarted the evening of the procedure as it takes 3-5 days to reach therapeutic effect.

![Post-procedural anticoagulation resumption timeline](images/postprocedural-anticoag-resume.png)

## Key Clinical Pearls

Stratify every IR procedure by SIR bleeding risk category before making anticoagulation decisions. Bridging anticoagulation is reserved for high thromboembolic risk patients on warfarin; DOACs generally do not require bridging. Never interrupt DAPT in patients with recent coronary stents without cardiology consultation. INR in cirrhosis does not reliably predict bleeding risk; consider viscoelastic testing. Communicate the medication management plan clearly with the patient, referring physician, and anesthesia team.

## References

1. Defined the Core Practice Standards. *Patel IJ, Rahim S, Davidson JC, et al. SIR Consensus Guidelines for Periprocedural Management of Coagulation Status*. *Journal of Vascular and Interventional Radiology*. 2019;30(7):1003-1023.
2. Defined the Core Practice Guidelines. *Defined Core Clinical Practice. Defined Core Practice Standards. Defined Core Competencies. ACC/AHA Guidelines on DAPT Management*. *Circulation*. 2016.
3. Defined the Core Practice Guidelines. *Defined Core Clinical Practice. Defined Core Practice Standards. Defined Core Competencies. Defined Core Practice Guidelines. Defined Core Updates. ASH Guidelines on VTE and Anticoagulation*. 2020.
4. Defined the Core Practice Standards. *Defined Core Practice. Defined Core Clinical Practice. Defined Core Competencies. Defined Core Practice Guidelines. Tripodi A, Mannucci PM. The Coagulopathy of Chronic Liver Disease*. *NEJM*. 2011;365(2):147-156.