scholarly journals Metabolic and cardiovascular effects on fetal sheep of sustained reduction of uterine blood flow.

1985 ◽  
Vol 368 (1) ◽  
pp. 109-129 ◽  
Author(s):  
W Gu ◽  
C T Jones ◽  
J T Parer
Keyword(s):  
Blood Flow ◽  
Cardiovascular Effects ◽  
Uterine Blood Flow ◽  
Fetal Sheep ◽  
Sustained Reduction

Behavioral activity during prolonged hypoxemia in fetal sheep

1988 ◽  
Vol 65 (6) ◽  
pp. 2420-2426 ◽  
Author(s):  
A. D. Bocking ◽  
R. Gagnon ◽  
K. M. Milne ◽  
S. E. White
Keyword(s):  
Blood Flow ◽  
Eye Movements ◽  
Normal Incidence ◽  
Behavioral Activity ◽  
Uterine Blood Flow ◽  
Fetal Sheep ◽  
Pregnant Sheep ◽  
Fetal Breathing ◽  
Fetal Breathing Movements ◽  
Internal Iliac

Experiments were conducted in unanesthetized, chronically catheterized pregnant sheep to determine the fetal behavioral response to prolonged hypoxemia produced by restricting uterine blood flow. Uterine blood flow was reduced by adjusting a vascular occluder placed around the maternal common internal iliac artery to decrease fetal arterial O2 content from 6.1 +/- 0.3 to 4.1 +/- 0.3 ml/dl for 48 h. Associated with the decrease in fetal O2 content, there was a slight increase in fetal arterial PCO2 and decrease in pH, which were both transient. There was an initial inhibition of both fetal breathing movements and eye movements but no change in the pattern of electrocortical activity. After this initial inhibition there was a return to normal incidence of both fetal breathing movements and eye movements by 16 h of the prolonged hypoxemia. These studies indicate that the chronically catheterized sheep fetus is able to adapt behaviorally to a prolonged decrease in arterial O2 content secondary to the restriction of uterine blood flow.

Chronic anemia in pregnant ewes: maternal and fetal effects

1991 ◽  
Vol 261 (5) ◽  
pp. R1075-R1083 ◽  
Author(s):  
D. Mostello ◽  
C. Chalk ◽  
J. Khoury ◽  
C. E. Mack ◽  
T. A. Siddiqi ◽  
...  
Keyword(s):  
Heart Rate ◽  
Blood Flow ◽  
Cardiac Output ◽  
Oxygen Delivery ◽  
Uterine Blood Flow ◽  
Chronic Anemia ◽  
Sustained Reduction ◽  
Arterial Po2 ◽  
Sustained Hypoxia ◽  
Sustained Increase

To examine maternal and fetal responses to a sustained reduction in maternal hematocrit during days 110-138 of ovine gestation, 22 ewes and their singleton fetuses were instrumented. By repetitive exchange transfusions, the hematocrit in 12 ewes was decreased from 28.1 +/- 0.8 (baseline, day 110) to 14.0 +/- 0.7% (day 117) and maintained at that level. Anemic ewes demonstrated a transient increase in heart rate from 99 +/- 4 to 116 +/- 4 beats/min and a sustained increase in cardiac output from 117 +/- 8 to 153 +/- 11 ml.min-1.kg-1 compared with control animals. Uterine blood flow steadily increased in control animals from 868 +/- 100 (day 110) to 1,410 +/- 177 ml/min (day 138) but failed to increase in the anemic ewes. Uterine oxygen delivery fell from 83 +/- 10 to 39 +/- 4 ml/min with production of anemia and remained low in the anemic ewes. Arterial PO2 and oxygen content in the fetuses of anemic ewes fell transiently below control values (19.9 +/- 0.8 vs. 23.4 +/- 1.0 mmHg and 5.3 +/- 0.3 vs. 6.8 +/- 0.4 ml/dl, respectively) but did not persist. Fetal weights at 138 days gestation were lower in the anemic group (2,596 +/- 329 vs. 4,313 +/- 132 g). We conclude that chronic maternal anemia results in a decreased uterine blood flow as well as decreased uterine oxygen delivery. The fetus responds with decreased growth but does not develop sustained hypoxia or acidosis.

Maternal Insufflation during the Second Trimester Equivalent Produces Hypercapnia, Acidosis, and Prolonged Hypoxia in Fetal Sheep

2004 ◽  
Vol 101 (6) ◽  
pp. 1332-1338 ◽  
Author(s):  
Kenichiro Uemura ◽  
Rebecca J. McClaine ◽  
Sebastian G. de la Fuente ◽  
Roberto J. Manson ◽  
Kurt A. Campbell ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Blood Flow ◽  
Oxygen Saturation ◽  
Partial Pressure ◽  
Uterine Blood Flow ◽  
Second Trimester ◽  
Blood Gas ◽  
Fetal Sheep ◽  
Total N ◽  
Arterial Blood

Background Anecdotal reports suggest that the second trimester is the safest time to conduct a laparoscopic procedure on a pregnant patient, but this supposition has not been tested empirically. Methods Previously instrumented preterm sheep (total n = 8) at gestational day 90 (term, 145 days) were anesthetized and then insufflated with carbon dioxide for 60 min at a pressure of 15 mmHg. Cardiovascular parameters were continuously recorded while blood gas status was determined before and at 15-min intervals during and up to 2 h after insufflation. Results Insufflation produced minimal maternal blood gas or cardiovascular changes except for a significant reduction in uterine blood flow. The decrease in perfusion increased fetal arterial blood partial pressure of carbon dioxide and decreased fetal pH, oxygen saturation, and oxygen content; there was also progressive fetal hypotension and bradycardia. After manually deflating the ewe, uterine blood flow returned to normal, and the fetal partial pressure of carbon dioxide and pH changes resolved within 1 h. However, fetal oxygen saturation and content remained depressed, and fetal cardiovascular status continued to decline during the 2-h postinsufflation monitoring period. Conclusion Previous studies with near-term sheep determined that carbon dioxide pneumoperitoneum produces respiratory acidosis but does not decrease fetal oxygenation. In contrast, the current findings indicate that in the preterm fetus, insufflation-induced hypercapnia and acidosis are accompanied by prolonged fetal hypoxia and cardiovascular depression. This result suggests that additional work should be conducted to confirm the presumed safety of conducting minimally invasive procedures during the second trimester.

Depression of uterine blood flow in response to cord compression in sheep

1982 ◽  
Vol 60 (6) ◽  
pp. 825-829 ◽  
Author(s):  
M. K. W. Cottle ◽  
G. R. Van Petten ◽  
P. van Muyden
Keyword(s):  
Blood Flow ◽  
Fluid Pressure ◽  
Cardiovascular Effects ◽  
Cord Compression ◽  
Tissue Fluid ◽  
Uterine Blood Flow ◽  
Fetal Hypoxia ◽  
Third Trimester ◽  
The Third ◽  
Stimulation Of

Seven conscious chronically cannulated ewes and their fetuses were studied in the third trimester of pregnancy. Compression of the umbilical cord for 4 min, to a degree simulating the occurrence in clinical obstetrics, not only produced the expected fetal hypoxia, acidemia, and cardiovascular effects but also significantly reduced uterine blood flow. In a ewe with twin fetuses, compression of the cord to only one fetus decreased the flow to that horn and had no effect on flow to the other horn. It is postulated that the reduction in uteroplacental flow was due to stimulation of α-adrenoceptors in the maternal placental vasculature by catecholamines of fetal origin, or the effects of increased tissue-fluid pressure in the fetal placenta, or a combination of these mechanisms.

scholarly journals Fetal endocrine responses to prolonged reduced uterine blood flow are altered following bilateral sectioning of the carotid sinus and vagus nerves

1998 ◽  
Vol 157 (1) ◽  
pp. 149-155 ◽  
Author(s):  
PE Stein ◽  
SE White ◽  
J Homan ◽  
L Fraher ◽  
HH McGarrigle ◽  
...  
Keyword(s):  
Blood Flow ◽  
Angiotensin Ii ◽  
Carotid Sinus ◽  
Arterial Oxygen Saturation ◽  
Cardiovascular Responses ◽  
Arterial Oxygen ◽  
Uterine Blood Flow ◽  
Vagus Nerves ◽  
Fetal Sheep ◽  
Fetal Plasma

The present study examines the effect of carotid sinus/vagosympathetic denervation on fetal endocrine responses to prolonged reduced uterine blood flow (RUBF). Fetal sheep had vascular catheters inserted following bilateral sectioning of the carotid sinus and vagus nerves (denervated, n = 7) or sham denervation (intact, n = 7). Uterine blood flow was mechanically restricted at 126.1 +/- 0.7 days (mean +/- S.E.M.) for 24 h, decreasing arterial oxygen saturation by 47.3 +/- 2.6% (P < 0.01). Fetal plasma samples were obtained at -1, 3, 6, 12 and 24 h for subsequent analyses of arginine vasopressin (AVP), angiotensin II and catecholamines. The AVP response to prolonged RUBF was markedly attenuated in denervated fetuses (15.6 +/- 3.6 to 34.9 +/- 6.0 pg/ml) when compared with intact (10.0 +/- 1.4 to 127.3 +/- 28.4 pg/ml). In contrast, intact fetuses demonstrated no change in plasma angiotensin II concentrations with RUBF whereas denervated fetuses demonstrated a marked increase from 47.5 +/- 18.9 to 128.7 +/- 34.2 pg/ml. The norepinephrine and epinephrine responses to prolonged RUBF were attenuated in denervated fetuses (950.1 +/- 308.9 and 155.8 +/- 58.5 to 1268.3 +/- 474.6 and 290.6 +/- 160.2 pg/ml respectively) when compared with intact (1558.3 +/- 384.4 and 547.3 +/- 304.7 pg/ml to 3289.2 +/- 1219.8 and 896.8 +/- 467.8 pg/ml respectively). These results support a role for the peripheral chemoreceptors in mediating fetal endocrine responses to prolonged RUBF, which may in part lead to the altered cardiovascular responses observed in denervated fetuses under these conditions.

Effect of prolonged catecholamine infusion on heart rate, blood pressure, breathing, and growth in fetal sheep

1995 ◽  
Vol 73 (12) ◽  
pp. 1750-1758 ◽  
Author(s):  
A. D. Bocking ◽  
S. E. White ◽  
S. Kent ◽  
L. Fraher ◽  
V. K. M. Man ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Rate ◽  
Blood Flow ◽  
Fetal Heart Rate ◽  
Fetal Heart ◽  
Tissue Growth ◽  
Uterine Blood Flow ◽  
Epinephrine Infusion ◽  
Fetal Sheep ◽  
Norepinephrine Infusion

Norepinephrine and epinephrine were infused into fetal sheep for 24 h to compare the effects on fetal heart rate, blood pressure, breathing movements, and tissue growth with those of prolonged reductions in uterine blood flow. Norepinephrine concentrations increased (p < 0.01) from 871 ± 71 to 6831 ± 1090 pg/mL (2 h) with norepinephrine infusion, and epinephrine concentrations increased from 310 ± 95 to 1424 ± 288 pg/mL (2 h) with epinephrine infusion. Fetal pH decreased (p < 0.01) from 7.37 ± 0.01 to 7.29 ± 0.02 at 0.5 h of the norepinephrine infusion and returned to control values by 2 h, whereas fetal lactate concentrations increased (p < 0.05) from 1.6 ± 0.2 to 4.6 ± 1.0 mmol/L at 2 h and remained elevated for 12 h. Lactate concentrations also increased with epinephrine infusion. Fetal heart rate increased (p < 0.05) from 176 ± 5 to 246 ± 6 and 220 ± 6 beats/min in the 1st h of norepinephrine and epinephrine infusions, respectively, with a subsequent decline. Fetal blood pressure increased (p < 0.05) from 43 ± 3 and 40 ± 2 to 53 ± 3 and 47 ± 2 mmHg (1 mmHg = 133.3 Pa) during the 1st h of norepinephrine and epinephrine infusions, respectively, remaining elevated for 24 h. Fetal body weights were not different between the groups of animals, although liver/body weight ratio was less (p < 0.05) in epinephrine-infused fetuses (0.030 ± 0.001) compared with vehicle-infused animals (0.036 ± 0.002). There was no change in DNA synthesis rate in any of the fetal organs, despite changes in organ-specific DNA and protein content. Our results indicate that the changes in fetal cardiovascular and behavioural function, as well as tissue growth, that occur with prolonged reductions in uterine blood flow are not mediated solely by elevated circulating catecholamine concentrations.Key words: fetal physiology, catecholamines, pregnancy.

Altered fetal cardiovascular responses to prolonged hypoxia after sinoaortic denervation

1999 ◽  
Vol 276 (2) ◽  
pp. R340-R346 ◽  
Author(s):  
P. Stein ◽  
S. E. White ◽  
J. Homan ◽  
M. A. Hanson ◽  
A. D. Bocking
Keyword(s):  
Blood Flow ◽  
Carotid Sinus ◽  
Arterial Oxygen Saturation ◽  
Cardiovascular Responses ◽  
Arterial Oxygen ◽  
Uterine Blood Flow ◽  
Vagus Nerves ◽  
Fetal Sheep ◽  
Peripheral Chemoreceptors

This study examines the role of the peripheral chemoreceptors in mediating fetal cardiovascular responses to prolonged hypoxia secondary to reduced uterine blood flow (RUBF). Fetal sheep were chronically instrumented for continuous heart rate (FHR), blood pressure (FBP), and carotid blood flow (CBF) measurements after bilateral sectioning of the carotid sinus and vagus nerves (denervated, n = 7) or sham denervation (intact, n = 7). Four days postoperatively, uterine blood flow was mechanically restricted, reducing fetal arterial oxygen saturation by 47.3% ( P < 0.01). An initial bradycardia was observed in intact (184.0 ± 10.7 to 160.5 ± 10.7 beats/min, not significant) but not denervated fetuses, followed by a tachycardia (180.0 ± 2.2 to 193.7 ± 2.7 beats/min, P < 0.05). FHR increased in denervated fetuses (175.5 ± 8.7 to 203.0 ± 17.9 beats/min, P < 0.05). FBP increased transiently in intact fetuses from 45.1 ± 1.0 to 55.4 ± 3.0 mmHg at 2 h ( P < 0.01), whereas denervated fetuses demonstrated a decrease in FBP from 47.1 ± 4.2 to 37.2 ± 3.7 mmHg (not significant). CBF increased ( P < 0.05) in both intact and denervated fetuses from 39.3 ± 2.8 and 29.7 ± 3.8 ml ⋅ min−1 ⋅ kg−1to 47.7 ± 0.4 and 39.1 ± 0.3 ml ⋅ min−1 ⋅ kg−1, respectively, whereas carotid vascular resistance decreased only in denervated fetuses (1.7 ± 0.1 to 1.1 ± 0.02 mmHg ⋅ ml−1 ⋅ min ⋅ kg−1, P < 0.05). We conclude that the peripheral chemoreceptors play an important role in mediating fetal cardiovascular responses to prolonged RUBF.

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