Key result
In fetal sheep, descending aorta peak systolic and mean maximum velocities were positively correlated to fetal core temperature and arterial pressure during cold stress and rewarming.
Why the study?
How does intrauterine cooling and rewarming affect descending aorta blood flow velocities in fetal sheep?
How does intrauterine cooling and rewarming affect descending aorta blood flow velocities in fetal sheep?
In fetal sheep, descending aortic blood flow velocities measured by Doppler sonography correlate with core temperature and arterial pressure during cold stress.
Provides preclinical evidence linking fetal aortic Doppler velocities to temperature and pressure; leaves open applicability to human perinatal cooling.
Pulsed wave Doppler sonography was used to determine peak systolic velocity (Vpeak), mean maximum velocity (Vmean) and Pulsatility Index (PI) in the descending aorta of chronically instrumented, unanesthetized fetal sheep (days 120-130 of pregnancy). Measurements were done 1-4 days after surgery using a duplex mechanical sector scanner (4.5 MHz) and offset attached pulsed wave Doppler probe (2.25 MHz) during periods of control, intrauterine cooling and rewarming. Mean values derived from the envelope curve of maximum shift frequencies were (controls): thoracic: Vmean 60.9 +/- 9.1 cm/sec, Vpeak 118.9 +/- 17.8 cm/sec, PI 1.57 +/- 0.24; abdominal: Vmean 49.6 +/- 10.9 cm/sec, Vpeak 98.9 +/- 20.4 cm/sec, PI 1.59 +/- 0.41. Vpeak was positively correlated to arterial pressure (r = 0.23) and PI showed an inverse correlation to heart rate (r = -0.22). During cold stress (reduction of fetal core temperature by 2.7 degrees C) and consecutive rewarming Vpeak and Vmean were positively correlated to fetal core temperature and arterial pressure (r = 0.2-0.26). PI revealed a weak negative dependency from core temperature and heart rate (r = -0.19 and -0.18 respectively).
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Hüneke et al. (1990) studied Fetal sheep. Intrauterine cooling and rewarming vs. Control periods was evaluated on Peak systolic velocity (Vpeak), mean maximum velocity (Vmean) and Pulsatility Index (PI) in the descending aorta. In fetal sheep, descending aorta peak systolic and mean maximum velocities were positively correlated to fetal core temperature and arterial pressure during cold stress and rewarming.
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