Cardiac variability in critically ill adults: Influence of sepsis

Abstract

Objective To evaluate, in critically ill adults, factors associated with impaired sympathovagal balance. Design One-month inception cohort study. Setting Twenty-six-bed medical intensive care unit of a teaching hospital. Patients Critically ill adults with an expected duration of intensive care unit stay of ≥48 hrs were enrolled. Patients with permanent arrhythmia or cardiac pacing were not included. Interventions None. Measurement and Main Results Sympathovagal balance was assessed on the day after intensive care unit admission by the low-frequency/high-frequency ratio obtained from spectral components of heart rate signal: overall variability, low frequency, and high frequency. Results Forty-one patients, 13 with sepsis and 28 without sepsis, were assessed. Predictors of low-frequency/high-frequency ratio with the automatic interaction detection method were sepsis and age. Binary logit analysis adjusted for age showed that sepsis remained a strong and independent factor of a low-frequency/high-frequency ratio of p = .005). Use of mechanical ventilation, catecholamines, or sedation did not add any information. The use of the low-frequency/high-frequency ratio in diagnosing sepsis may be supported by a likelihood ratio for low frequency/high frequency <1 at 6.47. Conclusions This work suggests that impaired cardiac variability and notably sympathovagal balance (i.e., a low-frequency/high-frequency ratio <1.0) may be a diagnostic test for sepsis.