What is the workup and treatment for septic pulmonary embolism (PE) from Serratia?

Septic Pulmonary Embolism from Serratia: Workup and Treatment

Immediate Diagnostic Workup

Obtain blood cultures immediately before starting antibiotics, recognizing that cultures may be negative in up to 30% of cases, particularly with recent antibiotic exposure. 1, 2

Clinical Presentation to Recognize

• Fever (present in 93% of cases), dyspnea (36%), pleuritic chest pain (29%), cough (14%), and hemoptysis (7%) are the typical presenting features 2
• Median symptom duration before diagnosis is 18 days, reflecting the insidious nature of this condition 2
• Multiple organ dysfunction syndrome develops in 85% of critically ill patients, with acute respiratory failure being the most common organ failure (75%) 3

Essential Imaging Studies

• CT chest with contrast is the diagnostic imaging modality of choice and should be obtained urgently, as chest radiography is typically nonspecific 1, 2
• Look for the characteristic CT findings: feeding vessel sign (90%), peripheral nodules without cavities (80%) or with cavities (65%), and peripheral wedge-shaped opacities (75%) 3, 2

Source Identification Protocol

• Immediately search for the primary infection source, as this is identified in 100% of cases 2
• Perform transesophageal echocardiography (TEE) to evaluate for right-sided infective endocarditis, cardiac implantable electronic devices, or prosthetic valve infections 1, 2
• Examine for septic thrombophlebitis from indwelling catheters, bone/skin/soft tissue infections, or injection drug use 1
• In Serratia cases specifically, investigate for infected vascular access devices (Portacaths, central lines) as these are common sources 4

Antimicrobial Treatment

Initiate broad-spectrum IV antibiotics immediately upon suspicion, then narrow based on culture sensitivities. 1, 3

Specific Antibiotic Coverage for Serratia

• Imipenem-cilastatin is FDA-approved for lower respiratory tract infections and septicemia caused by Serratia marcescens 5
• Imipenem-cilastatin covers Serratia in multiple infection sites including respiratory tract, urinary tract, intra-abdominal, and bloodstream infections 5
• Prolonged antimicrobial treatment according to culture sensitivities is essential for resolution of septic emboli 4

Duration and Monitoring

• Continue IV antibiotics for a minimum of 4-6 weeks, with longer courses often required depending on source control 1, 3
• Monitor clinical response with serial imaging and inflammatory markers 3

Source Control Interventions

Definitive source control is mandatory and often requires invasive intervention beyond antibiotics alone. 1, 6

Device-Related Infections

• Remove all infected indwelling catheters, pacemakers, or Portacaths immediately 4, 2
• For cardiac implantable electronic devices, complete device extraction is necessary 1

Surgical Indications

• Early thoracotomy should be considered when medical management fails, as this can prevent the need for prolonged open drainage procedures 6
• Surgical options include decortication, wedge excision, or more extensive pulmonary resection depending on extent of involvement 6, 2
• For right-sided endocarditis, valve excision may be required 6
• Tube thoracostomy or thoracoscopic surgery with decortication may be needed for empyema or loculated collections 2

Vascular Interventions

• Consider inferior vena cava interruption or vein excision if emboli continue despite source control 6
• Anticoagulation alone is dangerous and insufficient; proper surgical intervention is essential 6
• The role of anticoagulation in septic thrombophlebitis remains undefined and should not replace source control 1

Critical Care Management

Respiratory Support

• Provide supplemental oxygen for hypoxemia 3
• Mechanical ventilation may be required in 75% of critically ill patients with acute respiratory failure 3

Monitoring for Complications

• Watch for acute kidney injury, disseminated intravascular coagulation, and lung abscess formation, as these are associated with significantly higher mortality 3
• Monitor serum creatinine, coagulation parameters, and Sequential Organ Failure Assessment scores 3
• Serial CT imaging to assess for abscess formation or progression 3

Prognostic Factors

• In-hospital mortality ranges from 20-30% in published series 1, 3
• Nonsurvivors have significantly higher APACHE II scores, SOFA scores, serum creatinine, and are more likely to have acute kidney injury and disseminated intravascular coagulation 3
• Pneumonia and liver abscess as primary sources are associated with the highest mortality 3

Critical Pitfalls to Avoid

• Do not rely on anticoagulation alone to control emboli—this is dangerous and inadequate 6
• Do not delay source control interventions while waiting for antibiotic response 6, 3
• Do not dismiss the diagnosis based on negative blood cultures, as these occur frequently with recent antibiotic exposure 1
• Do not wait for clinical deterioration before considering surgical intervention—early thoracotomy improves outcomes 6