Low-Molecular Weight Heparin in Pediatrics

Introduction

Welcome to PICU Doc On Call, a podcast dedicated to current and aspiring pediatric intensivists. I'm Dr. Pradip Kamat from Children’s Healthcare of Atlanta/Emory University School of Medicine, and I’m Dr. Rahul Damania from Cleveland Clinic Children’s Hospital. We are two Pediatric ICU physicians passionate about medical education in the PICU. This podcast focuses on interesting PICU cases and their management in the acute care pediatric setting.

Episode Overview

In today’s episode, we are excited to welcome Dr. Karen Zimowski, Assistant Professor of Pediatrics at Emory University School of Medicine and a practicing pediatric hematologist at Children’s Healthcare of Atlanta at the Aflac Blood & Cancer Center. Dr. Zimowski specializes in pediatric bleeding and clotting disorders.

Case Presentation

A 16-year-old female with a complex medical history, including autoimmune thyroiditis and prior cerebral infarcts, was admitted to the PICU with acute chest pain and difficulty breathing. Despite being on low-dose aspirin, her oxygen saturation was 86% on room air. A CT angiography revealed a pulmonary embolism (PE) in the left lower lobe and signs of right heart strain. The patient was hemodynamically stable, and thrombolytic therapy was deferred in favor of anticoagulation. She was placed on BiPAP to improve her respiratory status. Her social history was negative for smoking, illicit drug use, or oral contraceptive use.

Key Case Points

• Diagnosis: Pulmonary embolism (PE)
• Hemodynamics: Stable with no right ventricular (RV) strain on echocardiogram
• Management Focus: Anticoagulation and consultation with the hematology/thrombosis team

Expert Discussion with Dr. Karen Zimowski

Risk Factors and Epidemiology of VTE in Pediatrics

• Pathophysiology: Venous thromboembolism (VTE) in children involves components of Virchow’s triad: stasis of blood flow, endothelial injury, and hypercoagulability.
• Incidence: VTE is rare in the general pediatric population but increases significantly in hospitalized children.
• Age Distribution: Bimodal peaks in infants and adolescents aged 15-17 years.
• Risk Factors: Central venous lines, infections, congenital heart disease, cancer, and autoimmune disorders.

Clinical Manifestations of DVT

• Symptoms: Swelling, pain, warmth, and skin discoloration in the affected extremity.
• Specific Presentations:
• SVC syndrome from superior vena cava thrombosis
• Abdominal pain from portal vein thrombosis
• Hematuria from renal vein thrombosis
• Neurological symptoms from cerebral sinus venous thrombosis

Diagnostic Approach for DVT

• Imaging:
• Compression Doppler Ultrasonography: Primary method for diagnosing DVT in pediatric patients.
• MR Venography (MRV) and CT Venography (CTV): Used for abdominal and cerebral sinus thrombosis.
• Laboratory Studies:
• D-dimer: Useful in adults; limited specificity in children.
• Other Labs: Renal and liver function tests, CBC with differential, DIC panel.

Management of DVT

Anticoagulation Strategies

• Unfractionated Heparin (UFH):
• Targets factors IIa and Xa; requires frequent monitoring.
• Adverse events: Bleeding and thrombocytopenia.
• Low Molecular Weight Heparin (LMWH):
• More predictable pharmacokinetics than UFH.
• Advantages include ease of administration and lower risk of HIT.
• Vitamin K Antagonists (VKAs):
• Used for long-term anticoagulation.
• Requires regular INR monitoring.
• Direct Oral Anticoagulants (DOACs):
• Dabigatran, Rivaroxaban, and Apixaban used in pediatric VTE.
• Advantages: No routine monitoring required, predictable effects.

Conclusion

In this episode, we discussed the intricacies of VTE diagnosis and management in pediatric patients. We thank Dr. Karen Zimowski for sharing her expertise on anticoagulation and hemostasis in the PICU. For more episodes and our Doc on Call management cards, visit picudoconcall.org.

Stay tuned for our next episode, and thank you for listening!

References

1. Fuhrman & Zimmerman - Textbook of Pediatric Critical Care: Thrombosis in Pediatric Critical Care.
2. American Society of Hematology 2018 Guidelines for Management of Venous Thromboembolism: Treatment of Pediatric Venous Thromboembolism.
3. Antithrombotic Therapy in Neonates and Children: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.
4. O’Brien, SH, Stanek JR, Witmer CM, Raffini L. The Continued Rise of Venous Thromboembolism Across US Children’s Hospitals. Pediatrics (2022).