Effects of Pharmacologic Agents on Umbilical Blood Flow in Fetal Lambs &lt;i&gt;in utero&lt;/i&gt;

Berman, William; Goodlin, Robert C.; Heymann, Michaël; Rudolph, Abraham M.

doi:10.1159/000241078

Cited by 56 publications

(8 citation statements)

References 11 publications

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“…Since the fetal renin-angiotensin system is well developed in late gestation (20) a physiological role of the peptide in the fetal placental flow regulation could be expected. This is supported by findings in animals showing exogenously administered AT to cause fetal placental vasoconstriction (16,29,85,126,153), and also by AT-induced vasocontraction in isolated human umbilical, chorionic and stem villous arteries (V111,3,152, Fig. 3).…”

Section: Effects Of Angiotensin I1supporting

confidence: 58%

Contraction and Relaxation of Human Uterine and Placental Smooth Muscle

Maigaard

1987

Acta Obstet Gynecol Scand

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Section: Effects Of Angiotensin I1supporting

confidence: 58%

Contraction and Relaxation of Human Uterine and Placental Smooth Muscle

Maigaard

1987

Acta Obstet Gynecol Scand

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“…Increases in the plasma ANP concentration have been shown to increase plasma renin activity (12). If ANP also increases angiotensin I1 concentrations, this may be one mechanism contributing to the increase in umbilicalplacental vascular resistance (20). Because the activity of other vasoactive hormones may have been altered by ANP infusion in these studies, the responses we observed were probably a combination of ANP and other hormone effects.…”

Section: Discussionmentioning

confidence: 63%

“…It is possible that sympathetic mechanisms may have mediated the increase in peripheral vascular resistance in the fetus. However, because infusions of epinephrine and norepinephrine do not directly alter umbilical-placental vascular resistance (20), some other mechanism(~) may also be involved. Increases in the plasma ANP concentration have been shown to increase plasma renin activity (12).…”

Section: Discussionmentioning

confidence: 99%

Renal and Cardiovascular Effects of Atrial Natriuretic Peptide in Fetal Sheep

1989

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ABSTRACT. In the adult, atrial natriuretic peptide ( A S P ) has been postulated to regulate renal and cardiovascular function both when blood volume is expanded and when atrial pressure is increased. In late gestation fetal sheep, A S P has been detected in plasma concentrations higher than in pregnant adults; however, its function in the fetus is unclear. To assess the role of A S P in mediating changes in combined ventricular output and organ blood flow, GFR, urine flow rate, and urinary sodium excretion, we studied 11 chronically cannulated fetal sheep at 126 to 131 d gestation (term 145 d). We infused A N P in doses of 27 f 4 and 55 f 8 ng/kg/min into nine of the 11 fetuses and vehicle only into the remaining two fetuses. A S P increased hematocrit, Hb, and plasma protein concentrations, which suggests that blood volume decreased. Combined ventricular output and umbilical-placental blood flow, measured by the radionuclide-labeled microsphere technique, decreased from 458 k 158 to 344 f 59 ml/min/kg and 210 f 85 to 144 f 31 ml/min/kg, respectively and the calculated umbilical-placental vascular resistance increased from 0.20 f 0.10 to 0.32 f 0.09 mm Hg/ml/min/kg during the infusion of the high A S P dose. Blood flow to the gastrointestinal tract decreased with the high dose of A N P but blood flow to all other organs, mean arterial blood pressure, and heart rate did not change significantly. The effects of A N P on fetal renal function were minimal. Thus, A S P may play a role in maintaining fluid homeostasis in the fetus through its ability to decrease blood volume and to decrease combined ventricular output and umbilicalplacental blood flow. (Pediatr Res 26: [1][2][3][4][5]1989) Abbreviations ANP, atrial natriuretic peptide i.d., inner diameter o.d., outer diameter ANP is a peptide hormone located in the cardiac atria of many adult mammalian species. Plasma concentrations of ANP increase when extracellular fluid volume is expanded or when atrial pressure is increased (1). Increased plasma concentrations of ANP have a variety of renal, cardiovascular, and endocrine effects (2). Large doses of ANP cause diuresis and natriuresis (2), a decrease in arterial blood pressure and cardiac output (3), inhibition of renin secretion after a decrease in renal perfusion pressure (4), and inhibition of aldosterone and vasopressin secre- (5,6). ANP is present in the fetal cardiac atria and ventricles (7). Basal plasma concentrations of ANP are greater in the fetus than in the pregnant adult and increase further after volume expansion and acute hypoxemia (8, 9). At present, relatively little is known about the effects of ANP in the fetus. Injection of large amounts of ANP (8 g / k g ) decreases arterial blood pressure and increases heart rate (10). However, infusion of smaller amounts of ANP (70 ng/min) increases renal excretion of sodium, potassium, and calcium, but does not change heart rate or mean arterial blood pressure (I 1). Unfortunately, the plasma concentrations at which these effects occurred were not availa...

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“…This may reflect the strong direct relation between fetal heart rate and umbilical flow noted by Berman et al, (28). This may reflect the strong direct relation between fetal heart rate and umbilical flow noted by Berman et al, (28).…”

Section: Discussionmentioning

confidence: 82%

“…These authors (28) have proposed that umbilical vascular impedance increases as heart rate decreases, independent of caliber changes of placental resistance vessels. This explanation has been challenged (29).…”

Section: Discussionmentioning

confidence: 99%

The Effects of Bupivacaine on the Umbilical Circulation and Placental Gas Exchange in the Fetal Lamb

Fleming

Lambert

Walker

1987

Anesthesia & Analgesia

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AM. The effects of bupivacaine on the umbilical circulation and placental gas in the fetal lamb. Anesth Analg 1987;66:1121-6.Seven chronically catheterized fetal sheep at 125-140 days gestation were studied in 12 experiments to determine the direct effects of the Zocal anesthetic bupivacaine (infused intravenously to the fetus) on the umbilical circulation and placental gas exchange. Electrocortical activity, umbilical blood flow, heart rate, and umbilical arterial and venous pressures w e continuously monitored in experiments comprising a baseline period, a drug infusion perwd and a recovery period, each of 2 hr duration. Samples of umbilical arterial and venous blood were taken for blood gas analysis, and for bupivacaine assay using high pressure liquid chro-matography technique. Fetal plasma bupivacaine levels zoere 1.3 -+ 0.3 pglml (mean 5 SEM) between 60-120 min of infusion. Heart rate and umbilical blood pow decreased significantly to 89 and 94% of control, respectively, (P < 0.05) during the infusion and returned to control levels by 2 hr afterwards. Mean umbilical arterial and venous pressures were not significantly altered, and no significant rise in umbilical vascular resistance occurred. No changes occurred in umbilical arterial or venous pH, PO,, or Pco~. In summ a y , bupivacaine reversibly depressed fetal heart rate and umbilical blood pow without detrimental changes in fetal blood gas or acid-base status.

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Effects of Pharmacologic Agents on Umbilical Blood Flow in Fetal Lambs <i>in utero</i>

Cited by 56 publications

References 11 publications

Contraction and Relaxation of Human Uterine and Placental Smooth Muscle

Contraction and Relaxation of Human Uterine and Placental Smooth Muscle

Renal and Cardiovascular Effects of Atrial Natriuretic Peptide in Fetal Sheep

The Effects of Bupivacaine on the Umbilical Circulation and Placental Gas Exchange in the Fetal Lamb

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