Downregulation of procalcitonin in mechanicaly ventilated patients

Introduction

Procalcitonin (PCT) has recently attracted attention as a possible marker of the systemic inflammatory response to infection. Downregulation of PCT in healthy human subjects after repetitive injection of endotoxin has been published. This effect was not investigated in critical ill patients so far.

Methods

We obtained serum levels of Procalcitonin (PCT) in 14 consecutive patients with long term mechanical ventilation (30-150 days (65.0 ± 2.6 [Mean ± SEM])). All patients experienced at least two severe systemic infections. Conventional markers of infection (C-reactive proteine, fibrinogen, white blood cell count and body temperature) as well as microbiological screening was performed simultaneously.

Results

A marked rise of PCT over 2.0 ng/ml could be observed in 7 patients (group 1) in response to severe infection. On admission on ICU these patients presented PCT serum levels between 0.24 and 25.4 ng/ml (6.8 ± 1.3 [Mean ± SEM]). The remaining 7 patients (group 2) had PCT levels between 1.1 and 147.6 ng/ml (17.5 ± 7.4 [Mean ± SEM]) on admission. Recurrent microbiologically and clinically proved severe infections were not accompanied by increased levels of PCT. The mortality in group 1 was significantly lower than in the second group (43% vs. 100%) [P < 0.05, Chi-Square-Test].

Conclusions

Our data suggest a downregulation of PCT levels in critically ill patients. Lacking rise of PCT serum levels with recurrent severe infections seems to be associated with high mortality. The predictive value of PCT for severe infections might be impaired by this mechanism. Further studies are required to verify these findings and to explain the potential reasons for failure of PCT in detection of recurrent infections of some patients in ICU.