Cardiac variability in critically ill adults: influence of sepsis.

Abstract

To evaluate, in critically ill adults, factors associated with impaired sympathovagal balance. One-month inception cohort study. Twenty-six-bed medical intensive care unit of a teaching hospital. Critically ill adults with an expected duration of intensive care unit stay of > or =48 hrs were enrolled. Patients with permanent arrhythmia or cardiac pacing were not included. None. 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. 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 <1.50, with an odds ratio of 3.63 (95% confidence interval, 1.47-9.01, 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. 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.