Serum zinc in critically ill adult patients with acute respiratory failure

Background and aims Zinc deficiency leads to susceptibility to infections and may affect pulmonary epithelial cell integrity. Low zinc levels have also been associated with a degree of organ failure and decreased survival in critically ill children. Accordingly, the purpose of the study was to assess serum zinc in adult patients with acute respiratory failure, its association with ventilatory support time, intensive care unit (ICU) length of stay (LOS), organ dysfunction and 30-day mortality. Methods We included consecutive patients with acute respiratory failure during an eight-week prospective, observational multicentre study (the FINNALI-study). Acute respiratory failure was defined as a need for either non-invasive or invasive positive pressure ventilation for > 6 h regardless of the underlying cause or risk factors. After informed consent, a sample for zinc measurement was drawn at 6 h after the start of treatment and analysed from 551 of these patients. Results Low serum zinc was frequent (95.8%) at the onset acute respiratory failure. The median interquartile range [IQR] was 4.7 [3.0-6.9] mu mol/l. The median [IQR] serum zinc levels in non-infectious, sepsis and septic shock patients were 5.0 [3.1-7.1], 5.1 [3.5-7.3] and 3.8 [2.6-5.9] mu mol/l, respectively, P < 0.01. Baseline zinc levels were not associated with ventilatory support time (P=0.98) or ICU LOS (P=0.053). The area under curve in receiver operating characteristics analysis for serum zinc regarding 30-day mortality was 0.55 (95% CI 0.49-0.60). Conclusions Serum zinc on initiation of ventilation had no predictive value for 30-day mortality, ventilatory support time or intensive care unit LOS.