Copeptin as a marker of shock and predictor of adverse outcome in critically ill patients

Introduction

Arginine vasopressin (AVP) is a peptide hormone that is released in response to osmotic and haemodynamic changes in order to maintain fluid volume and vascular tone. As a 'stress hormone', AVP is significantly increased in acute haemodynamic instability [1]. Copeptin is a stable fragment of pre-pro-vasopressin that is released in equimolar quantities as AVP, and thus reflects levels of released AVP. Unlike AVP, copeptin is highly stable ex vivo and is thus used for analysis. We aimed to study whether copeptin is elevated in any form of acute haemodynamic instability (that is, shock state) and whether copeptin is a predictor of outcome in critically ill patients.

Methods

A total of 352 consecutive patients (65% male, 64 ± 15 years, SAPS 2 52 ± 23) admitted to the ICU of the Department of Cardiology/Medical University of Vienna were included. Blood samples were obtained on admission in all patients. Copeptin was determined using a recently developed immunoassay in the chemiluminescence/coated tube format [2].

Results

Two hundred and seventy-seven patients survived to ICU discharge and 75 patients died. Copeptin plasma levels were significantly higher in ICU nonsurvivors than in ICU survivors (194 ± 205 pmol/l vs 101 ± 100 pmol/l; P < 0.0001). The area under the ROC curve for prediction of ICU survival was 0.678 for copeptin. Patients with diagnosis of shock (n = 132) had significantly higher copeptin plasma levels than patients without shock (174 ± 169 pmol/l vs 93 ± 100 pmol/l; P < 0.0001). There was no statistically significant difference in copeptin plasma levels between patients with different shock forms. Using a Kaplan–Meier model for 28-day survival, patients with copeptin plasma levels above the mean had significantly lower survival rates compared with patients with copeptin plasma levels below the mean (P = 0.03).

Conclusion

In critically ill patients, elevated plasma levels of copeptin are a strong and independent predictor of adverse outcome. Copeptin is significantly increased in shock patients, independent of the shock category.