tailieunhanh - Fetal Electrocardiography – part 6

Hoa của thai nhi Hành Vi thai nhi là đối tượng cho các tiểu bang khác nhau của ý thức và hoạt động và các nước này được đánh giá cao có liên quan đến nhịp tim ban đầu. Các quốc gia này được mô tả như là: Nhà nước IF-Không có các chuyển động cơ thể và chuyển động mắt nhanh chóng - một trạng thái ngủ. | The R-R Interval and the Cardiotocograph 73 Fetal Behavioural States The fetus is subject to various states of consciousness and activity and these states are highly relevant to the baseline heart rate. These states are described as State IF Absence of body movements and rapid eye movements a sleep state. State 2F Sleep state but with active rapid eye movements. State 3F Intermediate state between fetal activity and fetal wakefulness. State 4F Awake state true wakefulness. These states are not discernible until 36 weeks gestation. Episodes of inactivity are associated with low FHR variability and as these episodes rarely last longer than 40 minutes an antenatal trace should be continued for a minimum of one hour before it is considered that FHR variability is pathologically reduced. Vibro-acoustic stimulation may wake the baby and produce a transient tachycardia. High Fetal Heart Rate Variability Fluctuations of the FHR with a bandwidth in excess of 25 bpm often occur in labour or following acoustic stimulation of the fetus. Animal data have shown that the saltatory pattern can be demonstrated by inducing acute episodes of hypoxia in primates and may therefore represent episodes of cord compression Ikenoue 1981 . Low Fetal Heart Rate Variability Ingemarrson et al. 1993a have summarised the loss of FHR variability defined as less than 5 bpm under the following headings i Prematurity Tachycardia and reduced variability are common in labours before 34 weeks without associated acidosis. 74 Fetal Electrocardiography ii Fetal tachycardia A heart rate above 200 bpm is associated with low variability. iii Drugs such as pethidine reduce FHR variability and these changes appear to be associated with a change in the fetal behavioural state and presumably may be mediated through the CNS. Similar effects may be produced by beta-blockers. iv General anaesthesia. v Fetal malformations These malformations of both the CNS and fetal heart are associated with reduced variability. vi