Urinary and plasma cytokines in the critically ill

Introduction

We have previously demonstrated changes in circulating cytokines during the evolution of severe illness in ICU patients. This pilot study aimed to measure changes in circulating and urinary cytokines in critically ill patients receiving normal and high-nitrogen enteral feeds.

Methods

Patients (n = 40) were recruited from an adult, medical/ surgical ICU; urine and blood samples were obtained over three consecutive days. TNF-α, IL-6, IL-8, MCP-1 and leptin were measured by monoclonal antibody sandwich kit (ELISA). SIRS criteria were applied using the white blood cell count, heart rate, temperature and respiratory rate.

Results

Urinary cytokine concentrations (u[…]) were significantly raised in ICU patients relative to controls (at least P < 0.005). In addition, higher u[TNF-α ] (74%, P < 0.048) and u[IL-8] were observed in the highest SIRS index group (n = 8). There was a significantly higher u[IL-6] in the surgical group (n = 24) compared with sepsis and trauma patients (P < 0.0005). Plasma leptin levels (p[Lep]) increased with the duration of ICU stay. Urinary leptin was readily detectable in ICU patients: this has not been reported before. There was a marked elevation of u[Lep] (3.5-fold) in SIRS relative to non-SIRS patients (P < 0.001). The mean u[IL-6] was significantly decreased (45%, P < 0.01) in patients given a high protein diet. There was a strong inverse correlation between u[MCP-1] and dietary intake.

Conclusion

Urinary measures have potential in monitoring the ICU patient immune status noninvasively; urinary IL-8 and leptin may be markers of SIRS; a high-protein diet appears to reduce u[IL-6]; u[MCP-1] may be a marker of dietary delivery.