Assessing bedside measures of autonomic nervous system dysregulation in the PICU

Autonomic nervous system (ANS) dysregulation is common during critical illness and is often measured using heart rate variability (HRV). It is unknown if other forms of ANS function, such as pupillary light reflex and thermoregulation, are altered in critically ill children. We aimed to determine whether automated pupillometry and delta (central-to-peripheral) skin temperatures were associated with HRV.

In this prospective observational pilot, inclusion criteria were admission to the pediatric intensive care unit (ICU) and mechanical ventilation. HRV was calculated using age-adjusted integer HRV (HRVi). Automated pupillometry and skin temperatures were recorded during the first 72 h of admission. The primary outcomes were: (1) correlation between HRVi and Neurological Pupil index (NPi), and (2) correlation between HRVi and delta skin temperature.

Of 29 patients enrolled, 18 had pupillometer data and 20 had temperature data. There were significant, small correlations between left and right NPi values and HRVi (r = 0.13, r = 0.12; p < 0.001), and delta skin temperatures and HRVi (r = 0.15, p < 0.001), which persisted after adjusting for confounders.

Abnormal pupillary light response and decreased delta skin temperatures are associated with lower HRVi. If validated, pupillometry and skin temperature could be considered physiologic biomarkers of ANS dysregulation in critically ill children.

While heart rate variability has strong associations with outcomes in critically ill children, there are limited data on other bedside tools of autonomic function in critically ill children. In this study, we found that pupillometry and skin temperature sensors correlate with heart rate variability in critically ill children. These physiological biomarkers may have a role in early detection of autonomic nervous system dysregulation.