PubMed · 6888460
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E Abadie, J F Leclercq, P Passa. 1983-09-29. Pindolol and hyperthyroidism.. https://doi.org/10.1056/nejm198309293091315
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Late-onset neonatal sepsis is a significant cause of morbidity and mortality, and early detection could prove beneficial. Previously, we found that abnormal heart rate characteristics (HRC) of reduced variability and transient decelerations occurred early in the course of neonatal sepsis and sepsis-like illness in infants in a single neonatal intensive care unit (NICU). We hypothesized that this finding can be generalized to other NICUs. We prospectively collected clinical data and continuously measured RR intervals in all infants in two NICUs who stayed for >7 d. We defined episodes of sepsis and sepsis-like illness as acute clinical deteriorations that prompted physicians to obtain blood cultures and start antibiotics. A predictive statistical model yielding an HRC index was developed on a derivation cohort of 316 neonates in the University of Virginia NICU and then applied to the validation cohort of 317 neonates in the Wake Forest University NICU. In the derivation cohort, there were 155 episodes of sepsis and sepsis-like illness in 101 infants, and in the validation cohort, there were 118 episodes in 93 infants. In the validation cohort, the HRC index 1) showed highly significant association with impending sepsis and sepsis-like illness (receiver operator characteristic area 0.75, p < 0.001) and 2) added significantly to the demographic information of birth weight, gestational age, and days of postnatal age in predicting sepsis and sepsis-like illness (p < 0.001). Continuous HRC monitoring is a generally valid and potentially useful noninvasive tool in the early diagnosis of neonatal sepsis and sepsis-like illness.
Sleep is not just the absence of wakefulness but a regulated process with an important restorative function. Based on electroencephalographic recordings and characteristic patterns and waveforms we can distinguish wakefulness and five sleep stages grouped into light sleep, deep sleep, and rapid-eye-movement (REM) sleep. In order to explore the functions of sleep and sleep stages, we investigated the dynamics of sleep stages over the night and of heart-rate variability during the different sleep stages. Sleep stages and intermediate wake states have different distributions of their duration and this allows us to create a model for the temporal sequence of sleep stages and wake states. Heart rate is easily accessed with a high precision by the recording and analysis of the electrocardiogram (ECG). Heart-rate regulation is part of the autonomous nervous system and sympathetic tone is strongly influenced by the sleep stages.
The traditional time domain heart rate variability index pNN50 is a percentage scale-based measure of large beat-to-beat changes in heart period that may reflect parasympathetic neural activity impinging on the sino-atrial node. However, pNN50 exhibits nonlinear saturation effects near 0% and 100% that may adversely affect its statistical properties. The purpose of this paper is to propose a revision of pNN50, Logit50, that is the natural logarithm of the odds of the occurrence of large beat-to-beat differences in R-R interval. Using five clinical and normal sample data sets, the revised Logit50 index is shown to retain the computational simplicity and interpretability of the pNN50, but to have better metric properties in statistical and clinical applications. In particular, the Logit50 is demonstrated to be relatively unaffected by the positive distributional skew that is common in most statistical applications of pNN50.