Vesoulis Z A, Rao R, Trivedi S B, Mathur A M
Division of Newborn Medicine, Edward Mallinckrodt Department of Pediatrics, Washington University School of Medicine, St Louis, MO, USA.
J Perinatol. 2017 Jun;37(6):679-683. doi: 10.1038/jp.2017.42. Epub 2017 Apr 6.
Heart rate variability (HRV) reflects integrity of the autonomic nervous system. However, no study has investigated the impact of therapeutic hypothermia (TH) on HRV measures in infants with hypoxic-ischemic encephalopathy (HIE). In this study, we evaluate the influence of temperature on measures of HRV for a group of infants with favorable outcomes, as compared with a control group of infants with unfavorable outcomes.
Term-born infants with moderate-severe HIE underwent standard TH treatment and prospective electroencephalography (EEG) and electrocardiogram (ECG) recording. Infants with favorable outcome (no seizures, normal/mild EEG scores at 96 h, no magnetic resonance imaging brain injury and normal neurodevelopmental scores at 18 to 24 months) were matched on gestational age, sex and worst encephalopathy score to a group of infants with unfavorable outcomes. Time- and frequency-domain HRV measures were calculated from 60 min of ECG data obtained at three time points: 24 h (hypothermia), 48 h (hypothermia) and 96 h (normothermia). The effect of time and temperature were evaluated using repeated-measures analysis of variance.
Sixteen infants were included (8 favorable, 8 unfavorable). For both groups of infants, an increase in the HR, RR and HF power was associated with an increase in temperature, but was not associated with any other HRV measure. In contrast, measures of HRV increased over time, as encephalopathy decreased, for infants with favorable outcomes (reflecting increased cortical-autonomic integration), but not for those with unfavorable outcomes.
In general, the effect of hypothermia on measures of HRV is limited to changes in heart rate (bradycardia) and respiratory rate, as opposed to changes in true variability. This supports the hypothesis that persistent changes in HRV are driven by the underlying brain injury and not by the process of TH.
心率变异性（HRV）反映自主神经系统的完整性。然而，尚无研究调查治疗性低温（TH）对缺氧缺血性脑病（HIE）婴儿HRV指标的影响。在本研究中，我们评估了温度对一组预后良好婴儿HRV指标的影响，并与预后不良的对照组婴儿进行比较。
足月出生的中重度HIE婴儿接受标准TH治疗，并进行前瞻性脑电图（EEG）和心电图（ECG）记录。将预后良好（无癫痫发作、96小时时脑电图评分正常/轻度、无磁共振成像脑损伤且18至24个月时神经发育评分正常）的婴儿按胎龄、性别和最严重脑病评分与一组预后不良的婴儿进行匹配。从三个时间点（24小时（低温）、48小时（低温）和96小时（正常体温））获取的60分钟ECG数据中计算时域和频域HRV指标。使用重复测量方差分析评估时间和温度的影响。
纳入16名婴儿（8名预后良好，8名预后不良）。对于两组婴儿，心率、呼吸频率和高频功率的增加与温度升高相关，但与任何其他HRV指标无关。相比之下，预后良好的婴儿（反映皮质-自主神经整合增加）的HRV指标随时间增加，随着脑病减轻，但预后不良的婴儿则不然。
一般来说，低温对HRV指标的影响仅限于心率（心动过缓）和呼吸频率的变化，而不是真正变异性的变化。这支持了以下假设，即HRV的持续变化是由潜在的脑损伤驱动的，而不是由TH过程驱动的。
