Urinary Epinephrine Measurements in the Nicu and Their Correlation With Severity of Illness: Optimizing Reporting Methodology

Author Type(s)

Faculty, Resident/Fellow

Document Type

Abstract

Publication Date

2022

DOI

10.1136/jim-2022-ERM.132

Journal Title

Journal of Investigative Medicine

Department

Pediatrics

Abstract

Purpose of Study There is no established reliable method for reporting normalized urine epinephrine concentrations - particularly in the neonate. Urinary creatinine (Ucr) is often used to standardize urinary analyte concentrations but is influenced by clinical status, muscle mass and renal blood flow. In pheochromocytoma patients, 24h collection & normalization to urinary output are used. However, this may not be suitable for critically ill VLBWs due to the variable range of homeostatic imbalances. We sought to determine the preferred normalization tool by comparing 2 approaches after spot collection: i) to creatinine in the same sample (Epi/Cr ratio) or ii) extrapolated to 24h urinary output (ng/ml/kg/ day). Methods Used 46 samples were collected from 33 VLBWs on cotton sponges, acidified with 0.01 M HCL (1:1) and stored at -80°C before assay of duplicate samples (Rocky Mountain Dx kit; CO); batched to minimize variability. Protocol approved by NYMC IRB. Summary of Results Average time of collection was 31 weeks postmenstrual age, average gestational age was 28 ± 3/7 and average weight at time collection was 1.4 kg. When using Epi/Cr (ng/ml) ratio we found that higher Epi/Cr values [4.2 ± 0.5 vs 1.6 ± 0.3; 3.0 ± 0.4; x ± sem p< 0.0002] were associated with antibiotics exposure [72% (n= 18/25) vs 33% (n= 7/21); p< 0.01] and higher white blood cell counts [median 12 (min-max: 9.2, 19.5) vs 8.2 k/mm2 (5.1, 12.2); p< 0.04]. Patients receiving antibiotics had: higher white blood cell counts [13.5 (9.3, 19.8) vs 7.5 k/ mm2 (4.4, 11); p< 0.0009]; lower lymphocyte counts [29% ± 2.5 vs 44% ± 3; p< 0.0006]; higher absolute neutrophilic counts [7.3 (3.85, 11.1) vs 2.94 k/mm2 (2, 4.5); p< 0.0004]; higher FiO2 requirements [0.37 (0.27, 0.58) vs 0.21% (0.21, 0.25); p< 0.0001]; higher heart rates (174 ± 4 vs 163 bpm ± 4; p< 0.03); lower mean arterial pressures [31 ± 2 vs 38 mmHg ± 2; p< 0.02) and lower pulse oximeter saturations [84% (79%, 90%) vs 91% (84%, 96%); p< 0.02]. Conclusions Spot measurements of absolute epinephrine concentration normalized to 24h urine output showed no significant clinical correlates; presumably due to diminution of any individual stressor event distributed over 24h. In contrast, spot measurements obtained closer to the inciting event and normalized to Ucr correlated well with other indices of severity of illness, suggesting the Cr method is preferred for comparing rapid responses to stressors and interventions of short duration.

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