Elevated Procalcitonin and Mental Changes
Elevated procalcitonin does not directly cause mental changes; rather, mental status alterations are a manifestation of the underlying severe sepsis or septic shock that also causes the procalcitonin elevation. 1
Understanding the Relationship
Mental status changes and elevated procalcitonin are both consequences of the same underlying pathophysiology—severe infection with systemic inflammatory response—not a cause-and-effect relationship between the biomarker and neurologic symptoms. 1
Sepsis-Associated Mental Changes
- Altered mental status is a diagnostic criterion for severe sepsis, appearing alongside other organ dysfunction markers such as hypotension, oliguria, and lactate elevation. 1
- Mental dysfunction specifically correlates with septic shock severity (the most severe form of sepsis), which is also associated with procalcitonin levels >10 ng/mL. 2
- The mental changes result from hypoperfusion, metabolic derangements, and inflammatory mediators affecting brain function during severe sepsis, not from procalcitonin itself. 1
Procalcitonin as a Severity Marker
- Procalcitonin levels correlate with infection severity: <0.5 ng/mL suggests bacterial infection is unlikely, 0.5-2.0 ng/mL indicates SIRS, 2.0-10 ng/mL indicates severe sepsis, and >10 ng/mL indicates septic shock. 3, 4
- Research demonstrates that high procalcitonin levels show significant association with both mental dysfunction and septic shock, indicating these are parallel manifestations of severe disease. 2
- Procalcitonin >10 ng/mL combined with mental status changes can help determine septic shock as the underlying diagnosis. 2
Clinical Implications
When you encounter a patient with both elevated procalcitonin and mental changes:
- Immediately assess for septic shock criteria: hypotension despite adequate fluid resuscitation, lactate >2 mmol/L, and requirement for vasopressor therapy to maintain MAP ≥65 mmHg. 1, 3
- Initiate aggressive resuscitation with fluid therapy and early antimicrobial therapy within the first hour of recognition. 1, 3
- Evaluate for organ dysfunction using Sequential Organ Failure Assessment (SOFA) scoring, as mental changes represent neurologic organ dysfunction in the context of severe sepsis. 5, 6
- Obtain blood cultures before antibiotics (if no substantial delay >45 minutes) and start empiric broad-spectrum coverage targeting all likely pathogens. 1, 3
Important Caveats
- Do not attribute mental changes to procalcitonin elevation alone—always search for the underlying infectious source and assess for other causes of altered mental status (hypoglycemia, hypoxia, stroke, medications). 1
- Serial procalcitonin measurements are more valuable than single values; a 50% rise indicates worsening infection, while >25% decrease indicates treatment response. 3, 4
- Confounding factors that can elevate procalcitonin without bacterial infection include severe viral illnesses (though rarely >10 ng/mL), ARDS, and renal dysfunction. 3, 4