scholarly journals Dopamine infusion for postresuscitation blood pressure support after profound asphyxia in near-term fetal sheep

2012 ◽  
Vol 98 (3) ◽  
pp. 699-709 ◽  
Author(s):  
Paul P. Drury ◽  
Lindsea C. Booth ◽  
Laura Bennet ◽  
Joanne O. Davidson ◽  
Bert Wibbens ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Pressure Support ◽  
Fetal Sheep ◽  
Dopamine Infusion ◽  
Near Term

Cerebrovascular effects of intravenous dopamine infusions in fetal sheep

2002 ◽  
Vol 92 (2) ◽  
pp. 717-724 ◽  
Author(s):  
Christine A. Gleason ◽  
Roderick Robinson ◽  
Andrew P. Harris ◽  
Dennis E. Mayock ◽  
Richard J. Traystman
Keyword(s):  
Blood Pressure ◽  
Sch 23390 ◽  
Adrenergic Blockade ◽  
Receptor Blockade ◽  
Fetal Sheep ◽  
Dopamine Infusion ◽  
Cerebral Vasoconstriction ◽  
Arterial Blood ◽  
Near Term ◽  
Few Data

Preterm infants are often treated with intravenous dopamine to increase mean arterial blood pressure (MAP). However, there are few data regarding cerebrovascular responses of developing animals to dopamine infusions. We studied eight near-term and eight preterm chronically catheterized unanesthetized fetal sheep. We measured cerebral blood flow and calculated cerebral vascular resistance (CVR) at baseline and during dopamine infusion at 2.5, 7.5, 25, and 75 μg · kg−1 · min−1. In preterm fetuses, MAP increased only at 75 μg · kg−1 · min−1 (25 ± 5%), whereas in near-term fetuses MAP increased at 25 μg · kg−1 · min−1 (28 ± 4%) and further at 75 μg · kg−1 · min−1 (51 ± 3%). Dopamine infusion was associated with cerebral vasoconstriction in both groups. At 25 μg · kg−1 · min−1, CVR increased 77 ± 51% in preterm fetuses and 41 ± 11% in near-term fetuses, and at 75 μg · kg−1 · min−1, CVR increased 80 ± 33% in preterm fetuses and 83 ± 21% in near-term fetuses. We tested these responses to dopamine in 11 additional near-term fetuses under α-adrenergic blockade (phenoxybenzamine, n = 5) and under dopaminergic D1-receptor blockade (SCH-23390, n = 6). Phenoxybenzamine completely blocked dopamine's pressor and cerebral vasoconstrictive effects, while D1-receptor blockade had no effect. Therefore, in unanesthetized developing fetuses, dopamine infusion is associated with cerebral vasoconstriction, which is likely an autoregulatory, α-adrenergic response to an increase in blood pressure.

Peripheral chemoreflex activation and cardiac function during hypoxemia in near term fetal sheep without placental compromise

2021 ◽  
Author(s):  
Juulia Lantto ◽  
Tiina Erkinaro ◽  
Mervi Haapsamo ◽  
Heikki Huhta ◽  
Leena Alanne ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Carotid Artery ◽  
Arterial Oxygen ◽  
Sheep Model ◽  
Fetal Sheep ◽  
Descending Aorta ◽  
Arterial Blood ◽  
Near Term ◽  
Peripheral Chemoreflex

A drop in arterial oxygen content activates fetal chemoreflex including an increase in sympathetic activity leading to peripheral vasoconstriction and redistribution of blood flow to protect the brain, myocardium, and adrenal glands. By using a chronically instrumented fetal sheep model with intact placental circulation at near-term gestation, we investigated the relationship between peripheral chemoreflex activation induced by hypoxemia and central hemodynamics. 17 Åland landrace sheep fetuses at 115-128/145 gestational days were instrumented. Carotid artery was catheterised in 10 fetuses and descending aorta in 7 fetuses. After a 4-day recovery, baseline measurements of fetal arterial blood pressures, blood gas values, and fetal cardiovascular hemodynamics by pulsed Doppler ultrasonography were obtained under isoflurane-anesthesia. Comparable data to baseline was collected 10 (acute hypoxemia) and 60 minutes (prolonged hypoxemia) after maternal hypo-oxygenation to saturation level of 70-80% was achieved. During prolonged hypoxemia, pH and base excess (BE) were lower, and lactate levels higher in the descending aorta than in the carotid artery. During hypoxemia mean arterial blood pressure (MAP) in the descending aorta increased, while in the carotid artery MAP decreased. In addition, right pulmonary artery pulsatility index values increased, and the diastolic component in the aortic isthmus blood flow velocity waveform became more retrograde. Both fetal ventricular cardiac outputs were maintained even during prolonged hypoxemia when significant fetal metabolic acidemia developed. Fetal chemoreflex activation induced by hypoxemia decreased the perfusion pressure in the cerebral circulation. Fetal weight-indexed LVCO or AoI Net Flow-ratio did not correlate with a drop in carotid artery blood pressure.

scholarly journals Dopamine does not limit fetal cerebrovascular responses to hypoxia

2007 ◽  
Vol 102 (1) ◽  
pp. 130-134 ◽  
Author(s):  
Dennis E. Mayock ◽  
Rachel Bennett ◽  
Roderick D. Robinson ◽  
Christine A. Gleason
Keyword(s):  
Infusion Rate ◽  
Perfusion Pressure ◽  
High Dose ◽  
Fetal Hypoxia ◽  
Fetal Sheep ◽  
Dopamine Infusion ◽  
Cerebrovascular Resistance ◽  
Arterial Blood ◽  
Cerebral Vasodilatation ◽  
Near Term

Dopamine is used clinically to stabilize mean arterial blood pressure (MAP) in sick infants. One goal of this therapeutic intervention is to maintain adequate cerebral blood flow (CBF) and perfusion pressure. High-dose intravenous dopamine has been previously demonstrated to increase cerebrovascular resistance (CVR) in near-term fetal sheep. We hypothesized that this vascular response might limit cerebral vasodilatation during acute isocapnic hypoxia. We studied nine near-term chronically catheterized unanesthetized fetal sheep. Using radiolabeled microspheres to measure fetal CBF, we calculated CVR at baseline, during fetal hypoxia, and then with the addition of an intravenous dopamine infusion at 2.5, 7.5, and 25 μg·kg−1·min−1 while hypoxia continued. During acute isocapnic fetal hypoxia, CBF increased 73.0 ± 14.1% and CVR decreased 38.9 ± 4.9% from baseline. Dopamine infusion at 2.5 and 7.5 μg·kg−1·min−1, begun during hypoxia, did not alter CVR or MAP, but MAP increased when dopamine infusion was increased to 25 μg·kg−1·min−1. Dopamine did not alter CBF or affect the CBF response to hypoxia at any dose. However, CVR increased at a dopamine infusion rate of 25 μg·kg−1·min−1. This increase in CVR at the highest dopamine infusion rate is likely an autoregulatory response to the increase in MAP, similar to our previous findings. Therefore, in chronically catheterized unanesthetized near-term fetal sheep, dopamine does not alter the expected cerebrovascular responses to hypoxia.

Responses of fetal sheep to simulated no-decompression dives

1980 ◽  
Vol 48 (5) ◽  
pp. 776-780 ◽  
Author(s):  
M. K. Stock ◽  
E. H. Lanphier ◽  
D. F. Anderson ◽  
L. C. Anderson ◽  
T. M. Phernetton ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Flow ◽  
Maternal Blood ◽  
Arterial System ◽  
Fetal Sheep ◽  
Monitoring Result ◽  
Placental Blood ◽  
Near Term ◽  
Placental Blood Flow ◽  
Maternal Blood Pressure

The effect of simulated standard no-decompression dives to 60 and 100 ft of seawater was tested in 12 near term sheep carrying 16 fetuses. In the immediate postdive period there were no significant changes in fetal blood pressure or fetal placental or renal blood flow, but the maternal blood pressure was elevated and the maternal placental blood flow was depressed. Six surgically prepared fetuses were dived to 100 ft. Five died within 20 min of ascent and the sixth suffered severe cardiac arrhythmia and hypotension. At autopsy all fetuses were observed to have massive bubbling in the arterial system and heart. Five fetuses were dived to 100 ft without surgery. Two were alive 3 h later and no bubbles were present at autopsy, and three were born alive at term. With the 60-ft dives, three fetuses were subjected to surgery and all suffered massive bubbling. Two fetuses were dived to 60 ft without surgery; one was alive after 3 h and the other was born alive at term. We conclude that surgery and monitoring result in the formation of postdive gas bubbles that would not otherwise appear.

Renal sympathetic nerve activity during asphyxia in fetal sheep

2012 ◽  
Vol 303 (1) ◽  
pp. R30-R38 ◽  
Author(s):  
Lindsea C. Booth ◽  
Simon C. Malpas ◽  
Carolyn J. Barrett ◽  
Sarah-Jane Guild ◽  
Alistair J. Gunn ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Sympathetic Nerve ◽  
Sympathetic Nerve Activity ◽  
Nerve Activity ◽  
Fetal Sheep ◽  
Renal Sympathetic Nerve Activity ◽  
Renal Sympathetic Nerve ◽  
Arterial Blood ◽  
Near Term ◽  
Renal Sympathetic

The sympathetic nervous system (SNS) is an important mediator of fetal adaptation to life-threatening in utero challenges, such as asphyxia. Although the SNS is active well before term, SNS responses mature significantly over the last third of gestation, and its functional contribution to adaptation to asphyxia over this critical period of life remains unclear. Therefore, we examined the hypotheses that increased renal sympathetic nerve activity (RSNA) is the primary mediator of decreased renal vascular conductance (RVC) during complete umbilical cord occlusion in preterm fetal sheep (101 ± 1 days; term 147 days) and that near-term fetuses (119 ± 0 days) would have a more rapid initial vasomotor response, with a greater increase in RSNA. Causality of the relationship of RSNA and RVC was investigated using surgical (preterm) and chemical (near-term) denervation. All fetal sheep showed a significant increase in RSNA with occlusion, which was more sustained but not significantly greater near-term. The initial fall in RVC was more rapid in near-term than preterm fetal sheep and preceded the large increase in RSNA. These data suggest that although RSNA can increase as early as 0.7 gestation, it is not the primary determinant of RVC. This finding was supported by denervation studies. Interestingly, chemical denervation in near-term fetal sheep was associated with an initial fall in blood pressure, suggesting that by 0.8 gestation sympathetic innervation of nonrenal vascular beds is critical to maintain arterial blood pressure during the rapid initial adaptation to asphyxia.

scholarly journals Time scales of autonomic information flow in near-term fetal sheep

2012 ◽  
Vol 3 ◽  
Author(s):  
M. G. Frasch ◽  
B. Frank ◽  
M. Last ◽  
T. Müller
Keyword(s):  
Time Scales ◽  
Information Flow ◽  
Fetal Sheep ◽  
Near Term

scholarly journals Loss of interneurons and disruption of perineuronal nets in the cerebral cortex following hypoxia-ischaemia in near-term fetal sheep

2018 ◽  
Vol 8 (1) ◽  
Author(s):  
Tania M. Fowke ◽  
Robert Galinsky ◽  
Joanne O. Davidson ◽  
Guido Wassink ◽  
Rashika N. Karunasinghe ◽  
...  
Keyword(s):  
Cerebral Cortex ◽  
Perineuronal Nets ◽  
Fetal Sheep ◽  
Near Term

Heat production of fetal sheep brain in utero

1977 ◽  
Vol 43 (4) ◽  
pp. 747-749 ◽  
Author(s):  
R. M. Abrams ◽  
J. F. Clapp ◽  
M. Notelovitz ◽  
T. Tyler ◽  
S. Cassin
Keyword(s):  
Specific Heat ◽  
Heat Production ◽  
Brain Temperature ◽  
Main Pulmonary Artery ◽  
Fetal Brain ◽  
In Utero ◽  
Total Occlusion ◽  
Fetal Sheep ◽  
Sheep Brain ◽  
Near Term

Thermojunctions were implanted in the brains of 10 near term fetal sheep in utero under halothane anesthesia. Brief total occlusion of fetal brachiocephalic artery was followed immediately by an increase in brain temperature (mean +/- SE) of 0.130 +/- 0.014 degrees C-min-1. Occlusion of main pulmonary artery and ascending aorta, simultaneously, led to a brain temperature increase of 0.144 +/- 0.018 degrees C-min-1. Specific heat of three fetal brains was determined to be 0.898 +/- 0.014 cal-g-1. degrees C-1 or 3.76 +/- 0.059 J-g-1. Rate of fetal brain heat production, computed as the product of the higher rate of temperature change and brain specific heat, was 0.129 +/- 0.014 cal-g-1-min-1 or 9.00 +/- 0.98 mW-g-1.

scholarly journals Effect of Sildenafil on Pulmonary Circulation and Cardiovascular Function in Near-Term Fetal Sheep During Hypoxemia

2018 ◽  
Vol 26 (3) ◽  
pp. 337-347 ◽  
Author(s):  
Amarnath Bhide ◽  
Leena Alanne ◽  
Juha Rasanen ◽  
Heikki Huhta ◽  
Juulia Junno ◽  
...  
Keyword(s):  
Pulmonary Circulation ◽  
Cardiovascular Function ◽  
Fetal Sheep ◽  
Near Term
Sign in / Sign up

Export Citation Format

Share Document