Abstract P225: Frequency Domain Analysis of Heart Rate Variability in the Early Phase of Hemorrhage: Its Relation to Development of Shock
Purpose: Sympathetic withdrawal was suggested to represent a fundamental mechanism for the development of circulatory shock. However, its roles in the early phase of hemorrhage in clinical settings remain unknown. This prospective study was performed to test the hypothesis that parasympathetic neural predominance may occur in the early phase of hemorrhage, and discriminate hemorrhagic patients who later developed shock from those who did not.
Methods: Hemorrhagic patients without shock at the time of admission to ICU were enrolled. We used frequency domain analysis of heart rate variability (HRV) to assess autonomic function of patients. During the first 1 hour of admission, digital electrocardiogram (ECG) data was recorded and HRV indexes were derived off-line. The subjects were divided into two groups, those who developed shock later, and those who did not. We compared patients’ backgrounds, hemodynamic profiles, and spectral components in HRV at the time of ICU admission.
Results: Of 93 hemorrhagic patients admitted to ICU, 37 patients with ectopic beat- free ECG waveforms were enrolled (GI bleeding;17, trauma;17, others;3). Twelve of them developed shock after ICU admission (shock group), and 25 did not (non-shock group). Age, sex, causes of hemorrhage, respiratory rate, heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, pulse pressure, and APACHE II scores were similar between groups. In comparison with the non-shock group, the shock group had significantly lower LF (low frequency spectral power) (25.2±41.8 vs.55.6±83.p=0.023), lower total spectral power (34.9±53 vs.74.6±103.1, p=0.016), lower LF/HF (2.12±1.83 vs.6.83±5.35, p=0.01), lower LFnu (normalized low frequency R-R interval spectral power) (52.5±25.1 vs.70.2±23.5, p=0.018), and significantly higher HF/LF (1.36±1.53 vs.0.73±1.34, p=0.025), higher HFnu (normalized high frequency R-R interval spectral power) (40.7±22.9 vs.26±19.9, p=0.032).
Conclusions: These results indicated that parasympathetic neural predominance already existed in the early phase of hemorrhage in patients who later developed shock, suggesting that autonomic balance may provide important diagnostic and prognostic information.