Heart Rate Variability in Emergency Department Patients with Sepsis

Abstract

Objective: To test the hypothesis that heart rate variability (HRV) can provide an early indication of illness severity among patients presenting to the emergency department (ED) with sepsis. Methods: The authors enrolled a convenience sample of 15 ED patients meeting the American College of Chest Physicians/Society of Critical Care Medicine criteria for sepsis. Each patient had continuous Holter monitoring performed in the ED. Acute Physiology and Chronic Health II (APACHE II) and Sequential Organ Failure (SOFA) scores were calculated for the day of presentation. Holter tapes obtained in the ED were analyzed off-line to calculate HRV variables for the 5-minute segment with the least artifact and non-sinus beats. These variables were correlated with APACHE II and SOFA scores. Results: LFnu (normalized low-frequency power), an assessment of the relative sympathetic contribution to overall HRV, was correlated with increased illness severity as calculated using APACHE II (r = Ϫ0.67, r 2 = 0.43) and SOFA (r = Ϫ0.80, r 2 = 0.64) scores. LF/HF ratio (low-frequency/high-frequency ratio), a measure of sympathovagal balance, was correlated with the SOFA score [r = Ϫ0.54 (95% CI = Ϫ0.83 to Ϫ0.01), r 2 = 0.29]. All five patients who required critical care monitoring or ventilatory support or who died during the first 5 days of their hospitalization had LFnu values below 0.5 and LF/HF ratios less than 1.0. None of the patients with measurements greater than these threshold values died or required these interventions during the five days following admission. Conclusions: A single variable, LFnu, which reflects sympathetic modulation of heart rate, accounted for 40-60% of the variance in illness severity scores among patients presenting to the ED with sepsis. HRV, as reflected in LFnu and the LF/HF ratio and measured with a single brief (5-minute) period of monitoring while in the ED, may provide the emergency physician with a readily available, noninvasive, early marker of illness severity. The threshold effect of LFnu and LF/HF in the prediction of early clinical deterioration was an unexpected finding and should be regarded as hypothesis-generating, pending further study.

Use of the low-frequency/high-frequency ratio of heart rate variability to predict short-term deterioration in emergency department patients with sepsis

“…In contrast to our earlier study demonstrating the utility of HRV in predicting morbidity and mortality,21 our findings do not support the use of the LF/HF ratio by itself as an initial triage tool to identify moderately ill ED patients with sepsis at increased risk for short-term deterioration. Although there was a statistically significant relationship between the LF/HF ratio and short-term deterioration, this measure of HRV, obtained at presentation, by itself failed to consistently identify those patients who subsequently met one or more of the study endpoints, as reflected by the finding that 66% (21/32) of the patients who deteriorated had an LF/HF ratio >1 and would therefore have been incorrectly categorised using this criterion.…”

“…The ratio of low-frequency power to high-frequency power (LF/HF ratio) has been used as a summary measure of autonomic function 20. In 2001, we performed a pilot study of 14 ED patients with sepsis and found that all patients admitted to the ICU who required invasive critical care support or died had LF/HF ratios less than 1 21. Subsequent investigators have found similar associations between altered HRV and illness severity,22 development of multiple organ dysfunction syndrome,23 success or failure of early resuscitation,24 development of septic shock25 and in-hospital mortality 26…”

Heart rate variability - a potential early marker of sub-acute post-stroke infections

“…(A) HRV indices obtained in the acute phase. In addition to the investigated traditional linear HRV indices in this study, advanced non-linear HRV indices of complex autonomic control that predict sepsis and related outcome in newborns and adults (8,10,11,31,34) might also be useful in poststroke monitoring. (B) HRV indices obtained in the sub-acute phase (similar patients like in a).…”

“…This is because of the link between the immune system and the activity of the autonomic nervous system (ANS), which is reflected in heart rate variability (HRV) indices. However, several studies report that HRV indices are of diagnostic and prognostic value in critical care patients (4,(6)(7)(8)(9) and predict the development of infection and sepsis (10)(11)(12). The regulation of the immune response by the central nervous system and its associations with the cardiac autonomic control assessable with HRV indices are not fully understood.…”

Complex systems and the technology of variability analysis

“…For example, using spectral HRV and blood pressure variability analyses in consecutive patients admitted to an ICU, increasing total and LF HRV power were associated with recovery and survival, whereas progressive decreases in HRV were associated with deterioration and death [62]. In separate investigations involving patients in the emergency room [63] or admitted to an ICU after 48 hours [64], decreased total, LF and LF/HF HRV was not only present in patients with sepsis but also correlated with subsequent illness severity, organ dysfunction and mortality. Several reviews discuss the application of HRV spectral analysis to the critically ill patient [65-68].…”