Catheter-Directed Thrombolysis (CDT)

Contents

1. Introduction
2. Indications
3. Contraindications
4. Interventional Options
5. Pre-Procedure
6. Technique
7. Pharmacologic Thrombolysis Protocol
8. Mechanical Thrombectomy
9. Case Imaging
10. Complications
11. Post-Procedure Monitoring
12. Bleeding Management
13. Follow-Up
14. References

1. Introduction

Catheter-directed thrombolysis (CDT) in pediatric patients represents a specialized intervention for life- and limb-threatening thrombotic events. Due to the lack of well-designed pediatric clinical trials, treatment recommendations have limited evidence and are mainly extrapolated from adult guidelines. This protocol focuses exclusively on pediatric patients, incorporating the latest evidence to provide comprehensive recommendations for catheter-directed thrombolytic therapy in children.

2. Indications

• Life-threatening thrombosis with hemodynamic compromise
• Limb-threatening thrombosis with risk of amputation or significant disability
• Organ-threatening thrombosis (renal, hepatic, pulmonary)
• Extensive iliofemoral deep vein thrombosis in selected cases
• Phlegmasia cerulea dolens — emergency indication for limb salvage
• Failed anticoagulation therapy with progression of thrombosis
• CVAD-related thrombosis causing superior or inferior vena cava syndrome
• Extensive pulmonary embolism with right heart strain
• Renal vein thrombosis with acute kidney injury
• Portal vein thrombosis with portal hypertension complications

3. Contraindications

Absolute Contraindications

• Active internal bleeding or recent major hemorrhage
• Intracranial hemorrhage within 3 months
• Recent neurosurgery or significant head trauma within 3 months
• Known intracranial mass lesion or arteriovenous malformation
• Active seizures or uncontrolled seizure disorder
• Severe uncontrolled hypertension for age
• Known bleeding diathesis or coagulopathy
• Thrombocytopenia (<50,000/mm³ despite transfusion)
• Recent major surgery within 10 days (relative to bleeding risk)

Relative Contraindications (Risk–Benefit Assessment Required)

• Prematurity with increased bleeding risk
• Recent minor surgery or invasive procedures
• Gastrointestinal bleeding history within 3 months
• Severe hepatic dysfunction
• Severe renal dysfunction
• Anticoagulation contraindications
• Age <28 days (use with extreme caution)

Laboratory Contraindications

Parameter	Threshold
INR	>2.0 (unless correctable with FFP)
aPTT	>2× normal (unless correctable)
Fibrinogen	<100 mg/dL
Hemoglobin	<8 g/dL (unless correctable)

4. Interventional Options

• IVC filter placement
• Pharmacological thrombolysis
• Mechanical thrombectomy

5. Pre-Procedure

• Review pre-procedure imaging to document site and extent of thrombosis
• Review indications and contraindications
• Discuss management with hematology — if the plan is to start an alteplase infusion, the patient will require an ICP/ICU bed

Baseline Laboratory Documentation

• CBC
• Coagulation and DIC screen

6. Technique

Consent Obtain consent for venography/angiography, including follow-up, thrombolysis, thrombectomy, angioplasty, and IVC filter placement.

Thrombectomy will typically require anesthesia, but in older children an infusion catheter can be placed under local anesthesia.

Initial Imaging

• Access vessel without thrombosis (e.g., for femoral DVT, access popliteal)
• Perform arteriography or venography of affected vessels
• Document extent and location of thrombosis
• Assess collateral circulation
• Identify underlying anatomical abnormalities

IVC Filter Placement

• Insert filter prior to thrombolysis when indicated
• Avoid placement through affected limb when possible
• Remove filter as soon as possible — if resolution of thrombus after thrombectomy, remove filter at the end of the procedure

Thrombolysis Approach

Select mechanical, pharmacologic, or combined approach based on clot burden assessment.

7. Pharmacologic Thrombolysis Protocol

Alteplase Preparation and Dosing

• Reconstitute with sterile water; can be diluted further with saline
• Loading dose: at the discretion of the interventionalist, typically 2–3 mg

Infusion Dosing Guidelines

Parameter	Value
Initial rate	0.06 mg/kg/hr
Maximum initial dose	1 mg/hr (regardless of weight)

Standard Concentrations

Weight	Concentration
Children <30 kg	10 mg t-PA in 500 mL normal saline (0.02 mg/mL)
Children >30 kg	20 mg t-PA in 1000 mL normal saline (0.02 mg/mL)

Infusion Setup

• Unifuse catheter can be placed; available in multiple lengths and infusion segment lengths (5–40 cm)
• If a vascular sheath is placed, saline can be run in the side arm of the sheath to maintain patency

Supplemental Heparin Protocol

Parameter	Value
Route	Can be given peripherally
Sub-therapeutic dose	10 units/kg/hr (no loading dose)
Maximum dose	500 units/hour regardless of weight

8. Mechanical Thrombectomy

• Can be performed as primary treatment or follow 12–24 hours of thrombolytic therapy
• If primary: lace thrombus with 2–4 mg of alteplase using a 4/5 Kumpe catheter or infusion catheter; leave to dwell for 5–10 minutes
• Penumbra Lightning Bolt: use the largest caliber catheter that can be safely used. For DVT in older children, use a 12F system. See manufacturer IFU; call rep for assistance if not familiar with the device
• Residual thrombus can then be macerated using angioplasty balloons

9. Case Imaging

Step 1 -- Pre-procedure venogram demonstrates occlusive thrombus in the right external iliac vein.

Step 2 -- An infusion catheter has been placed extending across the length of the thrombus.

Step 3 -- Post-thrombolysis and mechanical thrombectomy venogram demonstrates patent iliac veins and IVC, with mild residual thrombus.

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10. Complications

Timeframe	Complications
Immediate (0–24 hours)	Vascular access complications (arterial puncture, hematoma, vessel injury)
Early (24–72 hours)	Local and systemic bleeding (major, minor, site-specific); intracranial hemorrhage with neurosurgical involvement; catheter-related complications (malposition, occlusion, infection)
Late (>72 hours)	Long-term thrombotic complications; post-thrombotic syndrome; vessel-related complications and interventions

11. Post-Procedure Monitoring

The post-procedure thrombolysis plan is included in EPIC.

Every 15 Minutes During Infusion

• Neurological assessment (age-appropriate)
• Bleeding evaluation: all access, IV, and surgical sites
• Vital signs: BP, HR, RR
• Extremity assessment: color, temperature, perfusion, pulses
• NPO while alteplase is infusing

Hourly Assessments

• Comprehensive neurological exam in verbal children
• Pain assessment using age-appropriate scales
• Urine output monitoring (goal >1 mL/kg/hour)
• Signs of systemic bleeding

Laboratory Monitoring (Every 4–6 Hours)

• Complete blood count with differential
• Comprehensive metabolic panel
• Coagulation studies: PT/INR, aPTT
• Fibrinogen level (maintain >100 mg/dL; >150 mg/dL in neonates)
• D-dimer trending

Additional Monitoring

• Type and crossmatch maintained
• Arterial blood gas if respiratory concerns
• Lactate if perfusion concerns

Dose Modifications

Finding	Action
Fibrinogen <100 mg/dL	Reduce t-PA by 50%
Fibrinogen <75 mg/dL despite cryoprecipitate	Hold therapy
Platelet count <100,000/mm³	Platelet transfusion
Persistently low fibrinogen	Cryoprecipitate

Monitoring location by thrombus type Continuous vital sign monitoring per ICU/ICP protocol is required for arterial thrombosis. For non-critical venous thrombosis, monitoring can be performed on the hematology floor. Continuously monitor the affected limb for signs of underperfusion (color, temperature, perfusion, limb girth, etc.). Only essential venipunctures should be obtained while t-PA is infusing — avoid IM injections.

12. Pediatric Bleeding Management

Major Bleeding Protocol

Immediate interventions

• Stop all thrombolytics and heparin immediately
• Activate massive transfusion protocol if available
• Notify pediatric intensivist and hematology immediately
• Consider surgical consultation for accessible bleeding

Reversal Agents

Agent	Dose
Aminocaproic acid	100 mg/kg IV loading dose, then 30 mg/kg/hour
Cryoprecipitate	10–15 mL/kg to raise fibrinogen >150 mg/dL
Fresh frozen plasma	15–20 mL/kg for coagulopathy
Platelet transfusion	10–15 mL/kg to maintain >100,000/mm³

Minor Bleeding Management

• Local measures: direct pressure, topical hemostatic agents
• Continue monitoring with increased frequency
• Consider dose reduction rather than discontinuation
• Maintain fibrinogen >100 mg/dL with cryoprecipitate

Hypersensitivity Reactions

• Stop infusion immediately
• Antihistamines: diphenhydramine 1 mg/kg IV
• Corticosteroids: methylprednisolone 2 mg/kg IV
• Epinephrine if anaphylaxis suspected

13. Follow-Up

Intermediate Care (1–7 Days)

• Transition to therapeutic anticoagulation
• Imaging follow-up within 24–48 hours
• Mobilization as clinically appropriate
• Family education for home monitoring

Long-Term Follow-Up

• Hematology follow-up at 1 week, 1 month, 3 months
• Imaging surveillance at 3 and 6 months
• Developmental assessment in younger children
• Thrombophilia workup when appropriate

14. References (click to expand)

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