How to make a post-mortem diagnosis of sepsis?

Post-Mortem Diagnosis of Sepsis

The post-mortem diagnosis of sepsis requires a comprehensive sampling protocol including blood cultures, tissue specimens, and specific biochemical markers, with samples collected within 2 hours if stored at room temperature or 48 hours if refrigerated. 1

Sampling Protocol for Post-Mortem Sepsis Diagnosis

Essential Samples to Collect

• Blood cultures: Collect two sets for both aerobic and anaerobic cultures from the femoral vein (not cardiac blood) 1, 2
• Cerebrospinal fluid: For bacterial culture and molecular analyses 1
• Respiratory specimens: Nasopharyngeal swabs, lung tissue samples 1
• Tissue specimens: Spleen, heart, liver, kidney, and any tissues with macroscopic findings suggesting infection 1
• Swabs from any identifiable lesions: Particularly important for surgical site infections or other focal infections 1

Timing and Storage Considerations

• Samples should be sent to the laboratory within 2 hours when stored at room temperature 1
• If refrigerated in adequate transport media, samples can be stored up to 48 hours 1
• Snap-frozen tissues should be preserved at -80°C for potential molecular analyses 1

Diagnostic Approach

Macroscopic Examination

• Carefully examine for evidence of infection foci during external and internal examination 3
• Look for surgical wounds, vascular access sites, pressure areas, or injection sites for evidence of infection 1
• Examine for mottled or ashen appearance, non-blanching petechial or purpuric rash, or cyanosis of skin, lips, or tongue 1

Microbiological Testing

• Direct bacterial culture of collected specimens with antibiotic resistance studies 1
• Molecular analyses for viral pathogens from appropriate specimens 1
• Consider anaerobic cultures, particularly with abscesses, abdominal pathology, or peritonitis 1
• Interpret anaerobic findings cautiously due to potential post-mortem translocation from gastrointestinal tract 1

Biochemical and Immunohistochemical Markers

• C-reactive protein (CRP): Levels ≥50 mg/L have high sensitivity (98.5%) for sepsis 1, 3
• Procalcitonin (PCT): Levels ≥1.5 ng/ml have high sensitivity (100%) for sepsis 1, 4
• At least two biochemical/immunohistochemical markers should be elevated simultaneously for reliable diagnosis 4

Histopathological Examination

• Although sepsis lacks pathognomonic lesions, histopathology remains an essential component of diagnosis 3
• Look for inflammatory changes in organs, particularly in the lungs, liver, spleen, and kidneys 4

Special Considerations

Surgical Site Infections

• Distinguish between superficial, deep, and organ/space surgical site infections 1
• Deep surgical site infections and intra-abdominal sepsis are frequently associated with bacteremia 1
• Polymicrobial infections are common, particularly involving anaerobes 1

Ventilator-Associated Pneumonia

• For cases with suspected respiratory source, collect endotracheal aspirates or perform bronchoscopy sampling 1
• Gram staining is essential for evaluating respiratory specimens 1
• Presence of squamous cells (>10 per high power field) and absence of leukocytes (<25 per high power field) suggests contamination 1

Interpretation Challenges

• Post-mortem bacterial translocation can complicate interpretation of culture results 1
• Lack of ante-mortem clinical data makes diagnosis more challenging 4
• No single marker is specific enough for definitive diagnosis; a combination approach is necessary 4, 3
• Interpret findings in context of circumstances of death, autopsy findings, and all laboratory results 3

Diagnostic Algorithm

1. Collect comprehensive samples as outlined above 1
2. Perform macroscopic examination looking for infection sources 3
3. Conduct microbiological testing (cultures and molecular analyses) 1
4. Test for inflammatory markers (CRP, PCT) 1, 3
5. Perform histopathological examination of key organs 3
6. Integrate all findings to establish sepsis as cause of death 3