Is procalcitonin a marker of critical illness in heatstroke?

Objective: To study the effect of non-exertional heatstroke on serum procalcitonin (PCT) levels. Design: Cohort study. Setting: The emergency and intensive care departments of two academic tertiary-care hospitals, Paris, France Patients: A total of 53 patients with defined heatstroke attending the emergency department and/or the intensive care unit during the August 2003 heat wave in France. Interventions: None. Measurements: Serum PCT measurement using a sensitive assay and vital and routine biological variables on arrival of patients presenting with classic heatstroke. Thirty-day mortality was recorded. Results: Among the 53 patients included, 14 (26%) were admitted to an intensive care unit (ICU). At 30 days, 24 patients (45%) had died. Median PCT value was 0.58 mu g/l (95% confidence interval 0.16 - 1.61) and 31 (58%) patients had PCT above 0.2 mu g/l (PCT+). Temperature above or equal to 40 C was the only variable significantly associated with fatal outcome. Median PCT values were 1.4 mu g/l (0.16 - 4.71) and 0.18 mu g/l (0.12 - 1.61) in the group of deceased and surviving patients respectively (p = 0.22). All patients admitted in ICU had elevated PCT values. Patients PCT+ initially presented with a more pronounced systemic inflammatory response. Microbiologically or clinically documented infection was not more frequent in PCT+ group. Conclusion: High serum PCT levels can be observed in heatstroke without any concomitant documented bacterial infection. The PCT is not a valid mortality predictor in heatstroke but could be an indicator of the severity of illness. Heatstroke could represent a model of a non-septic pathway of PCT synthesis.