scholarly journals Peripheral chemoreflex control of fetal heart rate decelerations overwhelms the baroreflex during brief umbilical cord occlusions in fetal sheep

2020 ◽  
Vol 598 (20) ◽  
pp. 4523-4536 ◽  
Author(s):  
Christopher A. Lear ◽  
Michi Kasai ◽  
Lindsea C. Booth ◽  
Paul P. Drury ◽  
Joanne O. Davidson ◽  
...  
Keyword(s):  
Heart Rate ◽  
Umbilical Cord ◽  
Fetal Heart Rate ◽  
Fetal Heart ◽  
Fetal Sheep ◽  
Peripheral Chemoreflex

scholarly journals Effects of β-adrenergic stimulation on fetal heart rate, heart rate variability, and T-wave elevation during brief umbilical cord occlusions in fetal sheep

2020 ◽  
Vol 319 (5) ◽  
pp. R551-R559
Author(s):  
Christopher A. Lear ◽  
Michael J. Beacom ◽  
Jenny A. Westgate ◽  
Shoichi Magawa ◽  
Tomoaki Ikeda ◽  
...  
Keyword(s):  
Heart Rate ◽  
Umbilical Cord ◽  
Fetal Heart Rate ◽  
Fetal Heart ◽  
Saline Control ◽  
Adrenergic Blockade ◽  
Adrenergic Stimulation ◽  
Fetal Sheep ◽  
T Wave ◽  
Wave Elevation

Circulating catecholamines are critical for fetal adaptation to hypoxia by regulating fetal heart rate (FHR) and promoting myocardial contractility and peripheral vasoconstriction. They have been hypothesized to contribute to changes in FHR variability (FHRV) and T-wave morphology, clinical indexes of fetal well-being during labor. β-Adrenergic blockade with propranolol does not affect FHRV during labor-like hypoxemia and only attenuated the increase in T-wave height between the episodes of hypoxemia. To further investigate the potential role of catecholamines, we investigated whether pharmacological β-adrenergic stimulation could increase FHRV and T-wave elevation during intermittent labor-like hypoxemia. Nineteen chronically instrumented fetal sheep at 0.85 of gestation received isoprenaline hydrochloride ( n = 7) or saline (control, n = 12), followed by three 1-min complete umbilical cord occlusions (UCOs) separated by 4-min reperfusion periods. Before the UCOs, infusion of isoprenaline increased FHR ( P < 0.001), absolute-T/QRS ratio ( P < 0.001), and one measure of FHRV [root-mean-square of successive RR interval differences (RMSSD), P < 0.05]. UCOs triggered deep FHR decelerations. During UCOs, isoprenaline was associated with increased FHR ( P < 0.001) and absolute-T/QRS ratio ( P < 0.05), but no effect on T/QRS ratio was observed when normalized to baseline before UCOs (normalized-T/QRS ratio). Between UCOs, isoprenaline increased FHR ( P < 0.001) and absolute-T/QRS ratio ( P < 0.05) but did not affect normalized-T/QRS ratio or any measures of FHRV. Arterial pressure was not affected by isoprenaline at any point. Our findings indicate that circulating catecholamines regulate FHR but not FHRV during labor-like hypoxemia and promote T-wave elevation between but not during intermittent fetal hypoxemia.

scholarly journals Early decelerations of the fetal heart rate from occlusion of the umbilical cord

1978 ◽  
Vol 6 (2) ◽  
pp. 69-79 ◽  
Author(s):  
C. Méndez-Bauer ◽  
A. Ruiz Canseco ◽  
M. Andujar Ruiz ◽  
A. Menendez ◽  
J. Arroyo ◽  
...  
Keyword(s):  
Heart Rate ◽  
Umbilical Cord ◽  
Fetal Heart Rate ◽  
Fetal Heart

Umbilical cord haematoma with altered fetal heart rate

2009 ◽  
Vol 29 (2) ◽  
pp. 150-151 ◽  
Author(s):  
A. Barbati ◽  
M. G. Cacace ◽  
D. Fratini ◽  
T. Ceccarelli ◽  
F. Capanna ◽  
...  
Keyword(s):  
Heart Rate ◽  
Umbilical Cord ◽  
Fetal Heart Rate ◽  
Fetal Heart

Biphasic changes in fetal heart rate variability in preterm fetal sheep developing hypotension after acute on chronic lipopolysaccharide exposure

2014 ◽  
Vol 307 (4) ◽  
pp. R387-R395 ◽  
Author(s):  
Christopher A. Lear ◽  
Joanne O. Davidson ◽  
Lindsea C. Booth ◽  
Guido Wassink ◽  
Robert Galinsky ◽  
...  
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Fetal Heart Rate ◽  
Low Dose ◽  
Fetal Heart ◽  
Transient Increase ◽  
Electromyographic Activity ◽  
Fetal Sheep ◽  
Arterial Blood ◽  
Fetal Heart Rate Variability

Perinatal exposure to infection is highly associated with adverse outcomes. Experimentally, acute, severe exposure to gram-negative bacterial lipopolysaccharide (LPS) is associated with increased fetal heart rate variability (FHRV). It is unknown whether FHRV is affected by subclinical infection with or without acute exacerbations. We therefore tested the hypothesis that FHRV would be associated with hypotension after acute on chronic exposure to LPS. Chronically instrumented fetal sheep at 0.7 gestation were exposed to a continuous low-dose LPS infusion ( n = 12, 100 ng/kg over 24 h, followed by 250 ng·kg−1·24 h−1 for a further 96 h) or the same volume of saline ( n = 10). Boluses of either 1 μg LPS or saline were given at 48, 72, and 96 h. Low-dose infusion was not associated with hemodynamic or FHRV changes. The first LPS bolus was associated with tachycardia and suppression of nuchal electromyographic activity in all fetuses. Seven of twelve fetuses developed hypotension (a fall in mean arterial blood pressure ≥5 mmHg). FHRV was transiently increased only at the onset of hypotension, in association with increased cytokine induction and electroencephalogram suppression. FHRV then fell before the nadir of hypotension, with transient suppression of short-term FHRV. After the second LPS bolus, the hypotension group showed a biphasic pattern of a transient increase in FHRV followed by more prolonged suppression. These findings suggest that infection-related hypotension in the preterm fetus mediates the transient increase in FHRV and that repeated exposure to LPS leads to progressive loss of FHRV.

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