What are the clinical manifestations of septic emboli (septic pulmonary embolism)?

From the Guidelines

Septic emboli should be treated with aggressive intravenous antibiotics and source control to prevent permanent organ damage and reduce mortality. Septic emboli are infected blood clots that travel through the bloodstream and lodge in distant organs, causing infection and tissue damage. They typically originate from infectious sites like endocarditis, infected intravenous catheters, or deep tissue infections. According to the 2014 ESC guidelines on the diagnosis and management of acute pulmonary embolism 1, septic embolism to the pulmonary circulation is a relatively rare clinical event and is commonly associated with right-sided endocarditis.

Key Considerations

• Risk factors include intravenous drug abuse and infected indwelling catheters or pacemaker wires 1.
• The diagnosis is based on identifying the source of septic emboli, positive blood culture tests, and chest X-ray or CT after considering the clinical context 1.
• Although Staphylococcus aureus is the most common bacterial pathogen, the increasing number of immunocompromised patients—and those with indwelling catheters and vascular prostheses—leads to a rise in the incidence of anaerobic gram positive and -negative bacteria, bacterioide species, and fungi 1.

Treatment Approach

• Treatment requires aggressive intravenous antibiotics, typically starting with broad-spectrum coverage like vancomycin (15-20 mg/kg IV every 8-12 hours) plus piperacillin-tazobactam (4.5g IV every 6-8 hours) or meropenem (1g IV every 8 hours), later narrowed based on culture results.
• Therapy usually continues for 4-6 weeks.
• Source control is essential, which may require removing infected catheters, draining abscesses, or surgical debridement.
• Anticoagulation is generally avoided unless there are specific indications.
• Patients need close monitoring with serial blood cultures, imaging studies to identify metastatic infections, and evaluation of organ function.

Complications and Monitoring

• Septic emboli can cause serious complications including stroke, pulmonary infarction, organ abscesses, and septic shock, making prompt diagnosis and treatment crucial for preventing permanent organ damage and reducing mortality.
• The guidelines from the European Society of Cardiology 1 emphasize the importance of prompt and effective treatment to improve outcomes in patients with septic emboli.

From the Research

Definition and Causes of Septic Emboli

• Septic emboli are a rare clinical entity that is distinct from the classic and more common non-septic thrombotic pulmonary embolism 2.
• They should be suspected in patients with a systemic acute inflammatory reaction or sepsis who develop signs and symptoms of pulmonary involvement 2.
• The primary source of infection can be right-sided infective endocarditis, cardiac implantable electronic devices, and septic thrombophlebitis as a complication of bone, skin, and soft tissue infection including Lemierre's syndrome, indwelling catheters, or direct inoculation via injection drug use 2.

Diagnosis and Treatment of Septic Emboli

• The diagnosis of septic pulmonary embolism (SPE) depends on the specific radiologic finding of multiple, peripheral, nodular, possibly cavitated lesions 2.
• Invasive treatment of the infection source may be necessary; in thrombophlebitis, the efficacy and safety of anticoagulation remain undefined 2.
• Broad-spectrum antimicrobial therapy should be considered, and blood cultures may be negative, particularly among patients with recent antibiotic exposure 2.
• The management of a patient with severe sepsis is first to diagnose the infection, to collect samples immediately after diagnosis and to initiate promptly broad-spectrum antibiotic treatment 3.

Antibiotic Therapy and Sepsis

• The choice of empirical antimicrobial therapy should be based on host characteristics, site of infection, local ecology and the pharmacokinetics and pharmacodynamics of the antibiotics 3.
• In severe infection, guidelines recommend the use of a combination of antibiotics 3.
• After results of cultures are obtained, treatment should be re-evaluated to either de-escalate or escalate the antibiotics 3.
• Combining vancomycin and gentamicin may be a safer alternative to cefotaxime for late-onset sepsis (LOS), as this reduces exposure to broad-spectrum antibiotics 4.

Microbiology of Sepsis

• Coagulase-negative staphylococci (CoNS) are the leading cause of late-onset sepsis (LOS) in neonates 5.
• Increasing resistance of CoNS to beta-lactams and aminoglycosides has led to widespread use of vancomycin, which in turn may lead to resistance to vancomycin 5.
• Combination therapy of LOS has been advocated, and in vitro results support that combination therapy with penicillinase-resistant penicillin and aminoglycoside can be an alternative to vancomycin 5.