Baseline serum concentrations of zinc, selenium, and prolactin in critically ill children

Objectives: To describe serum concentrations of zinc, selenium, and prolactin in critically ill children within 72 hours of PICU admission, and to investigate relationships between these immunomodulators and lymphopenia. Design: An analysis of baseline data collected as part of the multicenter Critical Illness Stress Induced Immune Suppression (CRISIS) Prevention Trial. Setting: PICUs affiliated with the Collaborative Pediatric Critical Care Research Network. Patients: All children enrolled in the CRISIS Prevention Trial that had baseline serum samples available for analysis. Interventions: None. Measurements and main results: Of 293 critically ill children enrolled in the CRISIS Prevention Trial, 284 had baseline serum samples analyzed for prolactin concentration, 280 for zinc concentration, and 278 for selenium concentration within 72 hours of PICU admission. Lymphocyte counts were available for 235 children. Zinc levels ranged from nondetectable (< 0.1 μg/mL) to 2.87 μg/mL (mean 0.46 μg/mL and median 0.44 μg/mL) and were below the normal reference range for 235 (83.9%) children. Selenium levels ranged from 26 to 145 ng/mL (mean 75.4 ng/mL and median 74.5 ng/mL) and were below the normal range for 156 (56.1%) children. Prolactin levels ranged from nondetectable (< 1 ng/mL) to 88 ng/mL (mean 12.2 ng/mL and median 10 ng/mL). Hypoprolactinemia was present in 68 (23.9%) children. Lymphopenia was more likely in children with zinc levels below normal than those with zinc levels within or above the normal range (82 of 193 [42.5%] vs. 10 of 39 [25.6%], p = 0.0498). Neither selenium nor prolactin concentrations were associated with lymphopenia (p = 1.0 and p = 0.72, respectively). Conclusions: Serum concentrations of zinc, selenium, and prolactin are often low in critically ill children early after PICU admission. Low serum zinc levels are associated with lymphopenia, whereas low selenium and prolactin levels are not. The implications of these findings and the mechanisms by which they occur merit further study.