Medical Care
Medical therapy centers on providing initial cardiopulmonary support, anticoagulation to prevent clot extension, and thrombolysis in the rare event of pulmonary embolism (PE) that leads to massive cardiorespiratory failure. When able, acquired risk factors such as central venous lines should be addressed. Much of the information regarding treatment of pulmonary embolism in children has been derived from that on adults.
Deciding how to treat a venous thrombosis that may lead to a pulmonary embolism is difficult. A survey of Canadian pediatric intensivists reported four patient factors commonly used to determine if a venous thrombosis was clinically important: clinical suspicion of a pulmonary embolism, symptoms, detection of thrombosis on clinical examination, and presence of an acute or chronic cardiopulmonary comorbidity that affects the patient's ability to tolerate a pulmonary embolism. [17]
Anticoagulation
Anticoagulation should be started in patients without contraindications (active bleeding). Systemic anticoagulation should be started with unfractionated or low molecular weight heparin (LMWH) to achieve an antifactor Xa level of 0.5-1 U/mL or, in the case of unfractionated heparin, activated partial thromboplastin time (aPTT) levels of twice the control value. Therapy should continue for 5-10 days.
Long-term anticoagulation should continue with LMWH for as long as 6 months to achieve a target antifactor Xa level of 0.5-1 U/mL. Alternatively, oral therapy with warfarin can be used to achieve an international normalized ratio (INR) of 2-3. If oral therapy is used, dosing should begin with initial systemic anticoagulation, with discontinuation of heparin on day 5.
Studies suggest that attempts to achieve a higher INR with warfarin are associated with an increased risk of bleeding without commensurately reducing the risk of new clot formation; therefore, aiming for an INR of 2-3 is recommended. Levels of more than 3 are generally unnecessary. Patients with the antiphospholipid syndrome may require INRs of more than 3.
Thrombolysis
Thrombolysis should be considered only if a large embolus is present in the pulmonary vasculature or in the setting of potential cardiac or pulmonary failure. Small case series have shown that systemic thrombolytic therapy can be safely used in pediatric patients with high risk venous thromboses. [27] Catheter-directed thrombolysis in centers with the appropriate expertise may be an alternative approach with lower risk of hemorrhage. [28] Potential benefit must be weighed against the significant risk of bleeding.
Supportive care
Pharmacologic support of the cardiovascular system may be necessary. Pressors, inotropic agents, and selective pulmonary vasodilators may be required in cases of obstructive shock from PE. Mechanical ventilation may be necessary both to provide respiratory support and as adjunctive therapy for a failing circulatory system. Extracorporeal membrane oxygenation (ECMO) has successfully been used to bridge patients who have suffered cardiac arrest or who are peri-arrest to definitive management. [29]
Children with sickle cell disease who present with pulmonary symptoms require treatment with a macrolide and cephalosporin antibiotic. Their clinical status should be closely monitored in order to anticipate those children who may develop acute chest syndrome. [8, 30]
Transfusion with packed RBCs (either simple or exchange) improves oxygenation immediately, helping to break the vicious cycle outlined above.
Transfer
Transfer to an appropriate institution for further workup and therapy. Generally, this is a tertiary center in view of the rarity of embolic disease in children.
Surgical Care
Surgical interventions in the management of pulmonary embolism consist primarily of embolectomy. Inferior vena cava filters have been used to prevent recurrent emboli, but few data are available regarding their use in children.
Embolectomy
Case reports and retrospective series support the use of surgical embolectomy in children centers with the appropriate resources and expertise. [1, 2] Consider embolectomy in the setting of massive cardiac failure when time is insufficient for natural or pharmacologic thrombolysis or if thrombolysis is contraindicated.
Very few cases of embolectomy in infants and neonates have been described in the literature. Kalanti et al reported a successful emergency surgical embolectomy in a 10-day-old preterm neonate who experienced sudden cardiorespiratory collapse. [2]
Vena caval filters
Otherwise known as Greenfield filters, these are placed surgically in the inferior vena cava (IVC) and prevent further emboli from reaching the pulmonary circulation. Indications for IVC filters include a contraindication to anticoagulation and recurrent PE despite adequate anticoagulation.
Historically, IVC filters have been limited to larger adolescent patients. Filter placement in younger patients has increased with the development of retrievable filters but is still limited to large centers with specific technical expertise. [31]
Complications include migration of the filter, sepsis, and misplacement of the filter.
Consultations
Consider consultations with the following specialists:
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Intensivist: A critical care specialist should be consulted in any case of pulmonary embolism with cardiorespiratory compromise.
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Pulmonologist: A pulmonologist is often consulted before the true diagnosis is made because of the nonspecific nature of the symptoms.
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Cardiologist: Consultation with a cardiologist is warranted to rule out a cardiac etiology for the presenting symptoms and signs and to perform ECHO and pulmonary angiography.
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Cardiothoracic surgeon: If embolectomy is considered, consultation with a cardiac surgeon is mandatory.
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Hematologist: A hematologist can suggest an appropriate workup for a procoagulant defect and can recommend an anticoagulation regimen. Consultation with a hematologist is essential in children with sickle cell disease. A free clinical consultation service for complex cases of thromboembolism in children is available for clinicians by calling The Pediatric Thrombosis Program at 1-800-NO-CLOTS (1-800-662-5687).
Diet and activity
No specific diet is contraindicated. However, excessive weight should be avoided in those with a history of pulmonary embolism.
Activity should not be limited. Mobilization should be encouraged in those with a history of pulmonary embolism or those at risk of having a pulmonary embolism. Patients taking anticoagulants should avoid high-impact sports.
Prevention
Anticipate patients at risk. Any child with a risk factor may develop a pulmonary embolism (PE). See Etiology. Methods to reduce risk include early mobilization, thromboembolic stockings, and prophylactic use of subcutaneous LMWH.
Current standard of care does not call for thromboprophylaxis in critically ill children without DVTs. [32] Practice with adolescent patients is mixed with a large minority routinely prophylaxing critically ill adolescents.
Females of childbearing age should be advised regarding the increased risk of thromboembolic disease during pregnancy. Women who are sexually active should be offered appropriate contraceptive advice. Those who wish to become pregnant should be referred to an obstetrician skilled in the management of hypercoagulable disorders during pregnancy.
Long-Term Monitoring
PT should be measured on a regular basis; the goal is an INR of 2-3.
The length of treatment depends on the presence of risk factors. If no underlying risk factors are present, therapy can be stopped within 1-2 months. If risk factors are present, especially anticardiolipin antibodies, therapy should continue for at least 4-6 months.
