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Lear CA, Beacom MJ, Dhillon SK, Lear BA, Mills OJ, Gunning MI, Westgate JA, Bennet L, Gunn AJ. Dissecting the contributions of the peripheral chemoreflex and myocardial hypoxia to fetal heart rate decelerations in near-term fetal sheep. J Physiol 2023; 601:2017-2041. [PMID: 37017488 DOI: 10.1113/jp284286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 03/30/2023] [Indexed: 04/06/2023] Open
Abstract
Brief repeated fetal hypoxaemia during labour can trigger intrapartum decelerations of the fetal heart rate (FHR) via the peripheral chemoreflex or the direct effects of myocardial hypoxia, but the relative contribution of these two mechanisms and how this balance changes with evolving fetal compromise remain unknown. In the present study, chronically instrumented near-term fetal sheep received surgical vagotomy (n = 8) or sham vagotomy (control, n = 11) to disable the peripheral chemoreflex and unmask myocardial hypoxia. One-minute complete umbilical cord occlusions (UCOs) were performed every 2.5 min for 4 h or until arterial pressure fell below 20 mmHg. Hypotension and severe acidaemia developed progressively after 65.7 ± 7.2 UCOs in control fetuses and 49.5 ± 7.8 UCOs after vagotomy. Vagotomy was associated with faster development of metabolic acidaemia and faster impairment of arterial pressure during UCOs without impairing centralization of blood flow or neurophysiological adaptation to UCOs. During the first half of the UCO series, before severe hypotension developed, vagotomy was associated with a marked increase in FHR during UCOs. After the onset of evolving severe hypotension, FHR fell faster in control fetuses during the first 20 s of UCOs, but FHR during the final 40 s of UCOs became progressively more similar between groups, with no difference in the nadir of decelerations. In conclusion, FHR decelerations were initiated and sustained by the peripheral chemoreflex at a time when fetuses were able to maintain arterial pressure. After the onset of evolving hypotension and acidaemia, the peripheral chemoreflex continued to initiate decelerations, but myocardial hypoxia became progressively more important in sustaining and deepening decelerations. KEY POINTS: Brief repeated hypoxaemia during labour can trigger fetal heart rate decelerations by either the peripheral chemoreflex or myocardial hypoxia, but how this balance changes with fetal compromise is unknown. Reflex control of fetal heart rate was disabled by vagotomy to unmask the effects of myocardial hypoxia in chronically instrumented fetal sheep. Fetuses were then subjected to repeated brief hypoxaemia consistent with the rates of uterine contractions during labour. We show that the peripheral chemoreflex controls brief decelerations in their entirety at a time when fetuses were able to maintain normal or increased arterial pressure. The peripheral chemoreflex still initiated decelerations even after the onset of evolving hypotension and acidaemia, but myocardial hypoxia made an increasing contribution to sustain and deepen decelerations.
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Affiliation(s)
- Christopher A Lear
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Michael J Beacom
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Simerdeep K Dhillon
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Benjamin A Lear
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Olivia J Mills
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Mark I Gunning
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Jenny A Westgate
- Department of Obstetrics and Gynaecology, The University of Auckland, Auckland, New Zealand
| | - Laura Bennet
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
| | - Alistair J Gunn
- The Fetal Physiology and Neuroscience Group, Department of Physiology, The University of Auckland, Auckland, New Zealand
- Department of Paediatrics, Starship Children's Hospital, Auckland, New Zealand
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Brusseau R, Mizrahi-Arnaud A. Fetal anesthesia and pain management for intrauterine therapy. Clin Perinatol 2013; 40:429-42. [PMID: 23972749 DOI: 10.1016/j.clp.2013.05.006] [Citation(s) in RCA: 92] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Anesthesia provision for fetal intervention differs from most other anesthetic situations insofar as anesthesiologists must care for 2 or more patients-each with potentially conflicting requirements. The first is the mother who can readily indicate discomforts, can be monitored directly, and to whom drugs may be administered directly and easily. For the fetus (or fetuses), nociception must be assumed or inferred indirectly, monitoring is limited at best, and drug administration is complicated and often indirect. Fetal and maternal hemodynamic stability must be assured; and a plan to resuscitate the fetus, should problems occur during the procedure, must be developed.
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Affiliation(s)
- Roland Brusseau
- Department of Anesthesia, Perioperative and Pain Medicine, Boston Children's Hospital, 300 Longwood Avenue, Boston, MA 02115, USA.
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Chandra R, Portbury AL, Ray A, Ream M, Groelle M, Chikaraishi DM. Beta1-adrenergic receptors maintain fetal heart rate and survival. Neonatology 2005; 89:147-58. [PMID: 16210849 DOI: 10.1159/000088842] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Accepted: 07/25/2005] [Indexed: 12/30/2022]
Abstract
Beta-adrenergic receptor (betaAR) activation has been shown to maintain heart rate during hypoxia and to rescue the fetus from the fetal lethality that occurs in the absence of norepinephrine. This study examines whether the same subtype of betaAR is responsible for survival and heart rate regulation. It also investigates which betaARs are located on the early fetal heart and whether they can be directly activated during hypoxia. Cultured E12.5 mouse fetuses were treated with subtype-specific betaAR antagonists to pharmacologically block betaARs during a hypoxic insult. Hypoxia alone reduced heart rate by 35-40% compared to prehypoxic levels. During hypoxia, heart rate was further reduced by 31% in the presence of a beta(1)AR antagonist, CGP20712A, at 100 nM, but not with a beta2 (ICI118551)- or a beta3 (SR59230A)-specific antagonist at 100 nM. Survival in utero was also mediated by beta1ARs. A beta1 partial agonist, xamoterol, rescued 74% of catecholamine-deficient (tyrosine-hydroxylase-null) pups to birth, a survival rate equivalent to that with a nonspecific betaAR agonist, isoproterenol (87%). Receptor autoradiography showed that beta1ARs were only found on the mouse heart at E12.5, while beta2ARs were localized to the liver and vasculature. To determine if the response to hypoxia was intrinsic to the heart, isolated fetal hearts were incubated under hypoxic conditions in the presence of a betaAR agonist. Heart rate was reduced to 25-30% by hypoxia alone, but was restored to 63% of prehypoxic levels with 100 nM isoproterenol. Restoration was completely prevented if beta1ARs were blocked with CGP20712A at 300 nM, a concentration that blocks beta1ARs, but not beta2- or beta3ARs. Our results demonstrate that beta1ARs are located on the heart of early fetal mice and that beta1AR stimulation maintains fetal heart rate during hypoxia and mediates survival in vivo.
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Affiliation(s)
- Rashmi Chandra
- Department of Neurobiology, Duke University Medical Center, Durham, NC 27710, USA
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4
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Senat MV, Loizeau S, Couderc S, Bernard JP, Ville Y. The value of middle cerebral artery peak systolic velocity in the diagnosis of fetal anemia after intrauterine death of one monochorionic twin. Am J Obstet Gynecol 2003; 189:1320-4. [PMID: 14634562 DOI: 10.1067/s0002-9378(03)00644-6] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
OBJECTIVE The purpose of this study was to assess the value of the fetal middle cerebral artery peak systolic velocity in the prediction of anemia within 24 hours of the death of one monochorionic twin in twin-to-twin-transfusion syndrome and to establish the correlation between middle cerebral artery peak systolic velocity and hemoglobin concentration in fetuses who are at risk for acute anemia. STUDY DESIGN Doppler examination of the middle cerebral artery peak systolic velocity was performed in 20 monochorionic survivors of pregnancies that were complicated by twin-to-twin-transfusion syndrome that occurred between 20 and 34 weeks of gestation. Doppler examination was performed before cordocentesis and after intrauterine transfusion when appropriate. Both hemoglobin concentration and middle cerebral artery peak systolic velocity were expressed in multiples of the median. Severe anemia was defined as hemoglobin concentration of <0.55 multiples of the median, and we used the cutoff point of 1.50 times the median values at any gestational age to calculate the sensitivity and specificity of middle cerebral artery peak systolic velocity in detecting moderate or severe anemia. RESULTS Fetal anemia was confirmed in 10 of 20 fetuses. We performed seven intrauterine transfusions. The sensitivity and specificity of middle cerebral artery peak systolic velocity in the prediction of severe fetal anemia were of 90%, with a false-negative rate of 10%. The correlation between peak systolic velocity and hemoglobin concentration both before and after transfusion was evaluated by regression analysis and was strongly significant. CONCLUSION In fetuses who are at risk of acute anemia, the measurement of middle cerebral artery peak systolic velocity was found to be a reliable noninvasive diagnostic tool and may be helpful in counseling and planning invasive assessment.
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Affiliation(s)
- M V Senat
- Department of Obstetrics and Gynecology, Hôpital de Poissy, University of Paris West, Rue du Champ Gaillard, 78300 Poissy, France
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Fletcher AJW, Gardner DS, Edwards CMB, Fowden AL, Giussani DA. Cardiovascular and endocrine responses to acute hypoxaemia during and following dexamethasone infusion in the ovine fetus. J Physiol 2003; 549:271-87. [PMID: 12665612 PMCID: PMC2342926 DOI: 10.1113/jphysiol.2002.036418] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
This study investigated the effects of fetal treatment with dexamethasone on ovine fetal cardiovascular defence responses to acute hypoxaemia, occurring either during or 48 h following the period of glucocorticoid exposure. To address the mechanisms underlying these responses, chemoreflex function and plasma concentrations of catecholamines, neuropeptide Y (NPY) and vasopressin were measured. Under general halothane anaesthesia, 26 Welsh Mountain sheep fetuses were surgically prepared for long-term recording at between 117 and 120 days of gestation (dGA; term is approximately 145 days) with vascular catheters and a Transonic flow probe around a femoral artery. Following at least 5 days of recovery, fetuses were randomly assigned to one of two experimental groups. After 48 h of baseline recording, at 125 +/- 1 dGA, half of the fetuses (n = 13) were continuously infused I.V. with dexamethasone for 48 h at a rate of 2.06 +/- 0.13 microg kg-1 h-1. The remaining 13 fetuses were infused with heparinized saline at the same rate (controls). At 127 +/- 1 dGA, 2 days from the onset of infusions, seven fetuses from each group were subjected to 1 h of acute hypoxaemia. At 129 +/- 1 dGA, 2 days after the end of infusions, six fetuses from each group were subjected to 1 h of acute hypoxaemia. Similar reductions in fetal partial pressure of arterial oxygen occurred in control and dexamethasone-treated fetuses during the acute hypoxaemia protocols. In control fetuses, acute hypoxaemia led to transient bradycardia, femoral vasoconstriction and significant increases in plasma concentrations of catecholamines, vasopressin and NPY. In fetuses subjected to acute hypoxaemia during dexamethasone treatment, the increase in plasma NPY was enhanced, the bradycardic response was prolonged, and the plasma catecholamine and vasopressin responses were diminished. In fetuses subjected to acute hypoxaemia 48 h following dexamethasone treatment, femoral vasoconstriction and plasma catecholamine and vasopressin responses were enhanced, whilst the prolonged bradycardia and augmented plasma NPY responses persisted. These data show that fetal treatment with dexamethasone modifies the pattern and magnitude of fetal cardiovascular responses to acute oxygen deprivation. Modifications to different mechanisms mediating the fetal defence responses to acute hypoxaemia that occur during dexamethasone treatment may reverse, persist or even become enhanced by 48 h following the treatment period.
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Tabacova SA, Kimmel CA. Atenolol: pharmacokinetic/dynamic aspects of comparative developmental toxicity. Reprod Toxicol 2002; 16:1-7. [PMID: 11934527 DOI: 10.1016/s0890-6238(01)00193-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Sonia A Tabacova
- National Center for Toxicological Research, US Food and Drug Administration, Rockville, MD, USA.
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Räsänen J, Jouppila P. Uterine and fetal hemodynamics and fetal cardiac function after atenolol and pindolol infusion. A randomized study. Eur J Obstet Gynecol Reprod Biol 1995; 62:195-201. [PMID: 8582495 DOI: 10.1016/0301-2115(95)02197-f] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVE To evaluate the short-term effects of intravenously given atenolol and pindolol on utero- and umbilicoplacental vascular impedance, fetal hemodynamics and cardiac function in patients suffering from pregnancy-induced hypertension. STUDY DESIGN A total of 24 women were randomized to receive atenolol or pindolol infusion. By using pulsed color Doppler techniques, uterine, placental arcuate, umbilical fetal middle cerebral and renal arteries were examined before, at the end and 30 min after the end of infusion. Pulsatility indices (PI) were calculated to assess vascular impedance. Fetal myocardial function was evaluated by using pulsed Doppler and M-mode echocardiography. Peak systolic velocities from the ascending aorta and pulmonary trunk, and also inner diameters and fractional shortenings of both ventricles were measured. RESULTS Both drugs significantly decreased maternal blood pressure. Immediately after the infusion, maternal heart rate was significantly decreased in both groups; but the decrease was clearer and lasted longer in the atenolol group. Pindolol caused no changes in utero- or umbilicoplacental vascular impedance, while atenolol increased it in the nonplacental uterine artery. After atenolol infusion, PI in the umbilical artery was higher than after pindolol. Pindolol had no effects on fetal hemodynamics, while atenolol decreased PI value in the fetal renal artery. Peak systolic velocity in the pulmonary trunk was decreased after atenolol. Pindolol did not affect the fetal cardiac function. In subgroups with originally increased utero- or umbilicoplacental vascular impedance, the responses in uterine and umbilical vascular impedance and in fetal hemodynamics and cardiac function after atenolol and pindolol were different compared to whole groups. CONCLUSION Differently acting antihypertensive agents seem to affect differently uteroplacental vascular impedance. Atenolol may have some direct effects on fetal hemodynamics and cardiac function. According to our results, pindolol seems to be more preferable in the treatment of pregnancy-induced hypertension than atenolol.
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Affiliation(s)
- J Räsänen
- Department of Obstetrics and Gynecology, University of Oulu, Finland
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Harper A, Murnaghan GA. Maternal and fetal haemodynamics in hypertensive pregnancies during maternal treatment with intravenous hydralazine or labetalol. BRITISH JOURNAL OF OBSTETRICS AND GYNAECOLOGY 1991; 98:453-9. [PMID: 2059591 DOI: 10.1111/j.1471-0528.1991.tb10339.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Intravenous treatment with 10 mg of hydralazine or 100 mg of labetalol was randomly allocated to 30 hypertensive pregnant women. Umbilical artery flow velocity waveforms were recorded using a pulsed Doppler duplex scanner (ATL Mk V) and umbilical artery pulsatility index (PI) and fetal heart rate (FHR) were derived from these recordings. Maternal blood pressure decreased significantly after both drugs. Maternal pulse rate increased after hydralazine but did not change significantly after labetalol. FHR did not change significantly after hydralazine but decreased after labetalol. PI decreased after hydralazine and increased after labetalol--most fetuses showed little change but a few in each group showed large changes in PI, as did two of five additional patients studied. We attributed the decrease in PI in some fetuses after hydralazine to vasodilation, and the increase in PI in some fetuses after labetalol to vasoconstriction in the fetoplacental circulation, suggesting that fetal beta-blockade may occur after maternal treatment with labetalol.
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Affiliation(s)
- A Harper
- Department of Obstetrics and Gynaecology, Queen's University of Belfast
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9
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Bocking AD, Gagnon R, White SE, Homan J, Milne KM, Richardson BS. Circulatory responses to prolonged hypoxemia in fetal sheep. Am J Obstet Gynecol 1988; 159:1418-24. [PMID: 3207118 DOI: 10.1016/0002-9378(88)90567-4] [Citation(s) in RCA: 71] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Experiments were conducted in 11 chronically catheterized pregnant sheep to determine the distribution of blood flow within the fetus during prolonged (48 hours) hypoxemia secondary to the restriction of uterine blood flow. Uterine blood flow was mechanically restricted with a polytetrafluoroethylene vascular clamp placed around the maternal common internal iliac artery such that mean (+/- SEM) fetal arterial oxygen tension decreased from 23.4 +/- 1.9 to 17.3 +/- 0.8 mm Hg at 1 hour of hypoxemia and remained low for 48 hours. There was an initial increase in fetal arterial carbon dioxide pressure from 48.5 +/- 0.9 mm Hg during the control period to 56.2 +/- 2.3 mm Hg at 1 hour; this parameter subsequently returned to control values, whereas base excess showed a transient decrease. Fetal cerebral, myocardial, and adrenal blood flows were significantly increased at 1, 24, and 48 hours of hypoxemia. In contrast, there was no change in nuchal muscle or renal blood flows with hypoxemia of this magnitude. Cotyledonary blood flow increased transiently by 38% at 1 hour of hypoxemia, but was not changed from control at 24 and 48 hours. These experiments demonstrate that the sheep fetus is able to maintain the normal protective circulatory adjustments seen with acute hypoxemia for up to 48 hours in the absence of progressive metabolic acidemia.
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Affiliation(s)
- A D Bocking
- Department of Obstetrics/Gynaecology, University of Western Ontario, London, Canada
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10
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Ingemarsson I, Arulkumaran S, Ratnam SS. Single injection of terbutaline in term labor. I. Effect on fetal pH in cases with prolonged bradycardia. Am J Obstet Gynecol 1985; 153:859-65. [PMID: 4073156 DOI: 10.1016/0002-9378(85)90690-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Thirty-three patients with prolonged fetal bradycardia (fetal heart rate baseline less than 100 bpm for a minimum of 3 minutes or less than 80 bpm for at least 2 minutes) in labor were studied. They were treated with a bolus injection of terbutaline if the bradycardia persisted at less than 80 bpm for 2 minutes and other efforts to improve the fetal heart rate (oxygen, positional changes) had failed. After the bolus injection a scalp blood pH (or a cord arterial pH in abdominal deliveries) was obtained within 30 minutes. Fetal acidosis was common if the bradycardia lasted 10 minutes or more, particularly if the rate was less than 80 bpm with a flat baseline for 4 minutes or more. The fetal heart rate improved after injection in 30 cases; 23 patients had vaginal delivery of infants in good condition. Ten underwent cesarean section: three for no improvement in fetal heart rate, two for cord prolapse, four for later ominous fetal heart rate, and one for failure to progress. These results suggest that tocolysis in selected cases can be of benefit for the fetus with prolonged bradycardia. In cases with an ominous fetal heart rate pattern preceding the bradycardia and in abruptio placentae immediate operative intervention without delay is probably better. Administration of terbutaline should be regarded as a temporary measure until it is apparent that the fetal heart rate has recovered. Preparation for emergency delivery should be made while a recovery is awaited.
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11
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Jovanovic R. Serial serum potassium and glucose levels during treatment of premature labor with oral terbutaline. Int J Gynaecol Obstet 1985; 23:399-404. [PMID: 2866991 DOI: 10.1016/0020-7292(85)90149-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The effects of prolonged use of orally-administered terbutaline on mothers and their infants were studied. The only side effect observed in all patients was transient maternal tachycardia. Fifty-six percent of the patients experienced palpitations, nervousness and tremors during the first few days of therapy, which thereafter resolved. This is contrary to the serious side effects reported during intravenous infusion of beta-mimetic agents. Maternal serum potassium and plasma glucose levels remained in the normal range during the entire therapy. Neonatal apgar, birthweight and metabolic parameters were all appropriate for gestational age. It appears that orally-administered terbutaline produces no significant maternal biochemical or biophysical changes, or any side effects on the fetus.
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Abstract
Growth retardation in the human fetus associated with maternal cardiovascular disease is frequently accompanied by birth asphyxia and perinatal mortality. We have investigated the cardiovascular responses to acute hypoxemia in the fetal lamb with growth retardation secondary to embolization of the uteroplacental vascular bed. In the basal period, fetal arterial P02 and umbilical perfusion were significantly lower, and perfusion of the adrenal glands, brain, and heart was significantly higher, in embolized than in control fetal lambs. During imposed acute hypoxemia there was preferential perfusion of vital organs, the adrenal glands, brain, and heart in control and embolized fetuses. This preferential perfusion to the vital organs during hypoxemia was significantly more pronounced in embolized animals. Because of the increased compensation during acute hypoxemia, as reflected by the increased preferential perfusion of vital organs, the growth-retarded fetuses would probably decompensate sooner if the hypoxemia was prolonged.
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13
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Parer JT. The influence of beta-adrenergic activity on fetal heart rate and the umbilical circulation during hypoxia in fetal sheep. Am J Obstet Gynecol 1983; 147:592-7. [PMID: 6139022 DOI: 10.1016/0002-9378(83)90024-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
To determine the importance of beta-adrenergic activity during hypoxia in the fetus, 13 studies were carried out on seven chronically instrumented sheep at nine tenths of gestation. Hypoxia was induced by having the mother breathe gas mixtures that resulted in a reduction of maternal arterial oxygen tension to 32 mm Hg. Hypoxia resulted in a decrease in fetal heart rate (165 +/- 17 to 140 +/- 28 bpm) and fetal oxygen consumption (5.9 +/- 1.3 to 3.0 +/- 1.5 ml/min/kg) and increases in fetal arterial and umbilical venous pressures. There was no change in umbilical blood flow (209 +/- 58 ml/min/kg). Propranolol, 1.1 ml/kg, was rapidly infused into a fetal vein to achieve complete beta-adrenergic blockade. Umbilical vascular resistance increased significantly, fetal heart rate decreased to 112 +/- 22 bpm, and umbilical blood flow decreased to 165 +/- 73 ml/min/kg. There was no further decrease in fetal oxygen consumption. These decreases are approximately twice those seen after propranolol without hypoxia. These findings suggest that during hypoxia there is an increase in beta-adrenergic activity, which tends to maintain fetal heart rate and umbilical blood flow. This activity counteracts the increase in vagal activity with hypoxia, which decreases heart rate.
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Bryant RC. Genetics of schizophrenia. Lancet 1983; 1:1158-60. [PMID: 6133172 DOI: 10.1016/s0140-6736(83)92885-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Rubin PC, Low RA, Reid JL. Antihypertensive therapy in pregnancy. Lancet 1983; 1:1160. [PMID: 6133173 DOI: 10.1016/s0140-6736(83)92886-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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