Prognostic value of serum zinc levels in critically ill patients

Introduction

Zinc is a trace element that is required for normal function of many enzymes. Intact zinc homeostasis must be present for normal function of the immune system, oxidative stress responses. We explored the hypothesis that a decline in serum zinc concentrations among critically ill patients is related to mortality, length of stay in the ICU, APACHE II and SOFA scores.

Methods

This prospective study was conducted in the ICU of the emergency department. All patients (>18 years) admitted to the ICU from September through November 2009 were enrolled into the study. Burn victims, alcoholics, patients with gastrointestinal fistulas and severe diarrhea were excluded from the study. Patients' demographic characteristics, APACHE and SOFA scores were recorded; blood samples were collected within 24 hours after admission and analyzed for serum zinc, copper, C-reactive protein and albumin levels. Patients were followed up for mortality and length of stay in the ICU for 28 days.

Results

Thirty-six patients were enrolled during the study period, with median age 70.5 years (18 to 87). The male to female ratio was 1:1.1. Serum zinc levels correlated inversely with SOFA scores (r = -0.41, P = 0.01). Patients with ≥8 SOFA scores had significantly lower serum zinc levels compared with patients with <8 SOFA scores (6.74 ± 1.63 μmol/l (n = 11) and 9.17 ± 2.76 μmol/l (n = 25), respectively; P < 0.05). There was no significant difference between serum zinc levels of patients with <25 and ≥25 APACHE II scores and also there was no significant difference between survivors and nonsurvivors. Serum zinc and copper levels had no significant relationship with length of stay in the ICU.

Conclusions

Serum zinc concentrations correlated inversely with SOFA scores in this study. This result supports that organ failure and critical illness leads to a decline in serum zinc concentrations and that zinc administration may be beneficial for critically ill patients.