Department of Physiology, Pt. BD Sharma Post graduate Institute of Medical Sciences, 1st Floor, Rohtak, India.
Department of Physiology, All India Institute of Medical Sciences, Room no. 2017, Teaching Block, Second Floor, Ansari Nagar, New Delhi, India.
High Blood Press Cardiovasc Prev. 2022 Jul;29(4):385-391. doi: 10.1007/s40292-022-00525-6. Epub 2022 Jun 7.
Haemorrhage is associated with changes in the cardiac autonomic drive which begins during early stages of mild haemorrhage. The knowledge of chronology of the autonomic changes at smaller timescale during the period of haemorrhage can help identify the primary autonomic parameter which signals the institution of cardiovascular reflex mechanisms.
To evaluate the heart rate variability in 2-min sequential segments with one minute overlap during and after the period of mild haemorrhage (450 ml) using blood donation as a model of acute blood loss.
47 male blood donors who had volunteered for blood donation were recruited for the study. Continuous lead II ECG was recorded before the start of the blood donation (5 min), during the period of the blood donation (~ 5-7 min) and after blood donation (5 min). The parasympathetic and sympathetic drive to heart was estimated by measures of heart rate variability in time and frequency domain.
A significant decrease in the parameters assessing parasympathetic drive i.e., normalised High frequency (HFn) and NN50 (Number of pairs of adjacent NN intervals differing by more than 50 ms) and pNN50 (NN50 divided by the total number of all NN Intervals) was observed during blood donation at 3-5 min, as compared to baseline. An increase in parameters associated with sympathetic drive i.e., normalised low frequency (LFn) was observed only in the post donation period at 2-3 min. A significant rise in LF/HF ratio which is a marker of sympatho vagal balance was observed at 4-5 min during blood donation when compared to baseline.
The initial cardiac autonomic change during mild haemorrhage is withdrawal of parasympathetic drive, followed by an increase in sympathetic tone which occurs much later.
出血与心脏自主驱动的变化有关，这种变化始于轻度出血的早期阶段。了解出血期间较小时间尺度上自主变化的时间顺序，可以帮助确定指示心血管反射机制建立的主要自主参数。
使用献血作为急性失血模型，评估轻度出血（450 毫升）期间和之后两分钟连续分段的心率变异性，每个分段重叠一分钟。
招募了 47 名自愿献血的男性献血者参加这项研究。在献血开始前（5 分钟）、献血期间（约 5-7 分钟）和献血后（5 分钟）连续记录 II 导联心电图。通过时间和频率域的心率变异性测量来估计心脏的副交感和交感驱动。
与基线相比，在献血期间的 3-5 分钟观察到评估副交感驱动的参数显着下降，即正常化高频（HFn）和 NN50（相邻 NN 间期差值超过 50ms 的对数）和 pNN50（NN50 除以所有 NN 间期的总数）。仅在献血后的 2-3 分钟观察到与交感驱动相关的参数增加，即正常化低频（LFn）。与基线相比，在献血期间的 4-5 分钟观察到 LF/HF 比值显着升高，这是交感迷走神经平衡的标志物。
轻度出血期间心脏自主神经的初始变化是副交感神经驱动的撤出，随后是交感神经张力的增加，这种增加发生得晚得多。
