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Anesthesiology, Vol. 73, No. 6. (December 1990), pp. 1179-1185.
Abstract
The authors investigated the spinal blood flow and metabolic effects of subarachnoid clonidine in conscious rats prepared with chronically implanted subarachnoid catheters. For the blood flow experiments, rats received saline (n = 7) or clonidine 20 nmol (7 micrograms; n = 6), 100 nmol (27 micrograms; n = 5), or 400 nmol (107 micrograms; n = 7) intrathecally. Another group of rats received clonidine 400 nmol intravenously (n = 4). Spinal glucose utilization was measured in rats that received either saline ...
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Early Hum Dev, Vol. 29, No. 1-3. (l 1992), pp. 259-267.
Abstract
Failing intrauterine support to the fetus can lead to intrauterine growth retardation (IUGR) and hypoxia and it is associated with a high risk of perinatal morbidity and mortality. The main effects of moderate to severe hypoxia on the fetus are different degrees of blood flow redistribution and reduction of oxygen consumption to maintain oxygen delivery to the central organs at the expenses of peripheral organs. The redistribution results in a 'brain sparing' effect. Recently, a Doppler ultrasonic technology (continuous wave, pulsed ...
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Am J Physiol, Vol. 270, No. 1 Pt 2. (January 1996)
Abstract
The purpose of the present investigation was to study the effect of 7 days of uterine blood flow reduction on fetal growth. Reduction in uterine blood flow was accomplished by external occlusion of the terminal aorta in 20 pregnant sheep. Linear growth was monitored daily by means of a crown-rump length measuring device. The deliveries of oxygen, glucose, and lactate to the fetus, as well as their uptakes by the fetus, were determined before and after 7 days of uterine blood ...
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Pediatr Res, Vol. 40, No. 2. (August 1996), pp. 337-343.
Abstract
To determine the circulatory response of the preterm fetus to a sustained hypoxic insult, regional blood flow was measured (microsphere technique) in 12 unanesthetized fetal sheep (0.75 gestation) during a normoxic control period, after 1 h and 8 h of sustained hypoxemia, and after a 1-h recovery period. Associated endocrine changes which might relate to organ-specific changes in blood flow were also assessed. Myocardial and cerebral blood flow were increased by 240 and 90%, respectively, such that oxygen delivery to the ...
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Am J Obstet Gynecol, Vol. 120, No. 6. (15 November 1974), pp. 817-824.
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Am J Physiol, Vol. 240, No. 1. (January 1981)
Abstract
The effects of acute hemorrhage were studied in two groups each with six fetal lambs (100-116 amd 128-147 days gestation) 3-4 days after we implanted catheters. Fetal blood pressures, heart rate, arterial blood gases and pH, and combined ventricular output and its distribution (radionuclide-labeled microsphere technique) were measured before and 5 min after removal of 15% of fetal-placental blood volume measured by 125I-albumin dilution. Because there were no differences in responses in the two age groups, the data were pooled. Fetal ...
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Am J Obstet Gynecol, Vol. 181, No. 4. (October 1999), pp. 1018-1025.
Abstract
OBJECTIVES: We sought to investigate the fetal hemodynamic response to the acute stress of invasive procedures. STUDY DESIGN: The middle cerebral artery pulsatility index was measured by Doppler ultrasonography before and after 136 invasive procedures (fetal blood sampling, transfusion, shunt insertion, tissue biopsy, and ovarian cyst aspiration). The response of fetuses submitted to invasive procedures involving transgression of the fetal body, such as intrahepatic vein blood sampling, was compared with that of control procedures at the placental cord insertion. RESULTS: The ...
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J Appl Physiol, Vol. 99, No. 6. (December 2005), pp. 2331-2336.
Abstract
Nitric oxide causes dilation of the pulmonary circulation and reduction in net lung liquid production in the fetal lamb, two critical perinatal events. Phosphodiesterase inhibition alone causes similar changes and also enhances the effects of nitric oxide. To better define the cyclic guanosine 5'-monophosphate (GMP) pathway in these events, we studied the effects of a specific phosphodiesterase inhibitor, E4021, on pulmonary arteries and veins isolated from near-term fetal lambs, as well as in intact, chronically instrumented late-gestation fetal lambs. In the ...
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Am J Physiol Lung Cell Mol Physiol (30 June 2006)
Abstract
Mechanisms that maintain high pulmonary vascular resistance (PVR) in the fetal lung are poorly understood. Activation of the rho-kinase signal transduction pathway, which promotes actin-myosin interaction in vascular smooth muscle cells, is increased in the pulmonary circulation of adult animals with experimental pulmonary hypertension. However, the role of rho-kinase in the fetal lung is unknown. We hypothesized that activation of rho-kinase contributes to elevated PVR in the fetus. To address this hypothesis, we studied the pulmonary hemodynamic effects of brief (10 ...
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Am J Obstet Gynecol, Vol. 195, No. 1. (July 2006), pp. 302-303.
Abstract
OBJECTIVE: The objective of the study was the catheterization of vessels in fetal sheep under ultrasound control. STUDY DESIGN: A catheter with guiding wire was introduced into the external jugular vein or carotid artery and advanced caudally. RESULTS: The aorta and umbilical vein could be accessed. CONCLUSION: Major segments of the circulation are accessible from the neck for chronic instrumentation. ...
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Auton Neurosci, Vol. 123, No. 1-2. (30 December 2005), pp. 19-25.
Abstract
OBJECTIVE: To characterize effects of sympathetic tone on fetal heart rate (FHR) reflex responses and FHR variability in late gestation. DESIGN/METHODS: Changes in FHR and autonomic tones were studied (i) after electrical vagal stimulation and (ii) during nitroprusside-induced hypotension, in seven late gestation ovine fetus in control condition (ctrl), after dobutamine (beta1-activation) and atenolol (beta1-blockade). Results are expressed as mean+/-SEM. RESULTS: (i) Minimal FHR after vagal stimulation was not influenced by atenolol or dobutamine but dobutamine accelerated FHR normalization. (ii) During ...
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Anesth Analg, Vol. 80, No. 5. (May 1995), pp. 949-954.
Abstract
Administration of fluids intravenously prior to spinal and epidural analgesia in obstetrics is required to prevent maternal hypotension and fetal hypoxia. A colloid solution, such as hydroxyethyl starch (HES), might be preferable considering the capacity to stay intravascularly for a longer period. In this study the placental transfer of HES and the hemodynamic effects after infusion were investigated using a chronic maternal-fetal sheep preparation. Either 500 mL HES 10% or 750 mL lactated Ringer's solution (RL) was infused intravenously into the ...
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Anesth Analg, Vol. 82, No. 5. (May 1996), pp. 1023-1026.
Abstract
Isoproterenol 5 micrograms may be an effective marker of accidental intravascular injection in women in labor; however, before isoproterenol can be incorporated in routinely used epidural test doses, the safety and usefulness should be determined in an animal model. This study was designed to examine the hemodynamic effects of isoproterenol in comparison with epinephrine in the pregnant ewe. Five doses of isoproterenol were tested and compared with two doses of epinephrine in a randomized cross-over fashion. After administration of isoproterenol there ...
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Eur J Anaesthesiol, Vol. 15, No. 3. (May 1998), pp. 320-323.
Abstract
A randomized crossover study was designed using the chronically instrumented pregnant sheep preparation to study the possible effects of epidural injection of adrenaline as a single compound on the circulation of mother and fetus. Three consecutive identical doses of adrenaline were administered epidurally with a 30 min interval between treatments. In a randomized crossover fashion two dosages (10 and 15 micrograms) were tested on different days. The day after the last epidural experiment the same doses of adrenaline were given intravenously ...
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Anesth Analg, Vol. 98, No. 2. (February 2004)
Abstract
Ketamine could be a useful maternal analgesic in obstetric surgery, as it might avoid the need for opioid administration and associated side effects in the newborn. Racemic ketamine passes the placental barrier and has oxytocin-like properties but does not seem to affect uterine blood flow (UBF). S(+)-ketamine was recently approved for clinical use, but its effects on UBF have not been evaluated. Therefore, we studied the effects of S(+)-ketamine on maternal and fetal hemodynamic variables. Equianalgesic doses of S(+)-ketamine (10 mg.kg(-1).h(-1)) ...
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Fetal Diagn Ther, Vol. 20, No. 3. (n 2005), pp. 208-213.
Abstract
BACKGROUND: Chronically compromised uterine perfusion may lead to placental insufficiency and subsequent intrauterine growth restriction (IUGR). Various therapeutic approaches (e.g. vasodilators, low-dose aspirin, intravenous glucose infusion, and hemodilution) are often of limited efficacy. Local anesthetics have been shown to improve placental blood flow in pre-eclamptic women. We hypothesized that epidural administration of local anesthetics might improve outcome in IUGR independent of the underlying cause. In preparation for a clinical trial to test this hypothesis, we performed a pilot study in 10 ...
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Eur J Anaesthesiol, Vol. 22, No. 5. (May 2005), pp. 359-362.
Abstract
BACKGROUND AND OBJECTIVE: Epidural and spinal anaesthesia are the preferred mode of anaesthesia for Caesarean section. Volume preloading is recommended to prevent maternal hypotension and a reduction in uteroplacental blood flow, although positive effects of volume preloading on maternal cardiac output and arterial pressure are debatable. Doppler measurements of the umbilical artery beyond deriving pulsatility indices are not routinely performed. METHODS: After Institutional Review Board approval and written informed consent, 14 consecutiVe women with epidural anaesthesia for Caesarean section received either ...
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Fetal Diagn Ther, Vol. 20, No. 5. (t 2005), pp. 377-382.
Abstract
INTRODUCTION: Maternal hypotension is a major concern in obstetric anesthesia, and concerns have been raised about standard vasopressor therapy with ephedrine. Therefore, we evaluated the maternal and fetal hemodynamic effects of two potential alternatives to ephedrine. METHODS: Hypotension was induced by epidural administration of lidocaine in 6 chronically instrumented pregnant ewes (at 118-122 days of gestation, term 145 days). Three treatments were studied: 25 mg ephedrine, 5 mg etilefrine and 100 mg cafedrine/5 mg theodrenaline (C/T) intravenously. Mean fetal and maternal ...
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J Pediatr Surg, Vol. 37, No. 12. (December 2002), pp. 1678-1680.
Abstract
BACKGROUND/PURPOSE: Nonimmune hydrops in the fetus is a finding that often portends death. The association and prognosis of fetuses with congenital diaphragmatic hernia (CDH) and hydrops is not known. METHODS: A retrospective review of all prenatally diagnosed cases and referrals of CDH was performed. Variables analyzed included gestational age at diagnosis and delivery, side of hernia, presence of associated anomalies and hydrops, and neonatal outcome. RESULTS: Since 1993, 474 prenatal referrals for CDH have been made. One hundred seventy-five were evaluated; ...
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Pediatr Res, Vol. 54, No. 1. (July 2003), pp. 44-51.
Abstract
Recent in vitro studies reported that nitric oxide release and pulmonary vasorelaxation can be mediated by endothelial alpha2-adrenoceptor activation. As norepinephrine (alpha1-,alpha2-, and beta1-adrenoceptor agonist) was found to induce pulmonary vasodilation in the ovine fetus, we hypothesized that alpha2-adrenoceptors may modulate basal pulmonary vascular tone and mediate the vascular effect of norepinephrine during fetal life. To determine the role of alpha2-adrenoceptors and the mechanisms of norepinephrine-mediated vasodilation in the fetal pulmonary circulation, we tested, in chronically prepared late-gestation fetal lambs, the ...
Note (first note only)
methodiek catheterisatie is interessant
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Am J Physiol Regul Integr Comp Physiol, Vol. 281, No. 2. (August 2001)
Abstract
High levels of circulating catecholamines are found in the fetus, and fetal stress and birth induce a marked surge in catecholamine secretion. Little is known about the role of catecholamines on the fetal pulmonary circulation. To determine the effects of catecholamines on the pulmonary vascular tone, we tested the hemodynamic response to norepinephrine and dopamine infusion in chronically prepared late-gestation fetal lambs. We found that norepinephrine infusion (0.5 microg. kg(-1). min(-1)) increased pulmonary artery pressure (PAP) by 10 +/- 1% (P ...
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Ann Chir, Vol. 126, No. 7. (September 2001), pp. 659-665.
Abstract
STUDY AIM: Mechanisms that modulate fetal pulmonary circulation and transitional circulation at birth are incompletely understood. The aim of this experimental study was to describe an animal model in order to study the perinatal pulmonary circulation. MATERIAL AND METHODS: Pregnant ewes were operated on between 126 and 128 days gestation (term = 145 days). A skin incision was performed to the fetal lambs in utero and catheters were placed into the ascending aorta and the superior vena cava after insertion in ...
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Am J Obstet Gynecol, Vol. 189, No. 1. (July 2003), pp. 208-215.
Abstract
OBJECTIVES: Although mechanisms of glucocorticoids-induced parenchymal lung maturation have been largely studied, little is known about the pulmonary vascular effects of antenatal glucocorticoids (GCs). We therefore hypothesized that antenatal GCs may alter the hemodynamic response to vasodilatory agents in the fetal lung. STUDY DESIGN: We tested the hemodynamic response to acetylcholine, increased PaO(2), and norepinephrine infusion before and after maternal GC administration in chronically prepared, late-gestation fetal lambs (135-137 days of gestational age, term = 147 days). RESULTS: We found that ...
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J Perinat Med, Vol. 31, No. 6. (2003), pp. 538-539.
Abstract
Authors suggest that high incidence of persistence pulmonary hypertension among neonates delivered by elective cesarean is related to lower levels of circulating norepinephrine in neonates after cesarean section than after vaginal delivery. ...
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Br J Anaesth, Vol. 93, No. 6. (December 2004), pp. 818-824.
Abstract
BACKGROUND: This experimental study was performed to determine the effects of norepinephrine on: (i) the pulmonary vascular tone during the development of pulmonary hypertension (PH) in the fetus and (ii) the circulatory adaptation at birth after chronic intrauterine PH. METHODS: Chronically instrumented fetal lambs were randomized into two groups: (i) a group with PH obtained by antenatal partial ligation of the ductus arteriosus (DA) (n=9) and (ii) a control group without DA ligation (n=6). Pulmonary vascular responses to norepinephrine (1.5 microg ...
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Am J Physiol Regul Integr Comp Physiol, Vol. 288, No. 2. (February 2005)
Abstract
The fetus is able to exhibit a stress response to painful events, and stress hormones have been shown to modulate pulmonary vascular tone. At birth, the increased level of stress hormones plays a significant role in the adaptation to postnatal life. We therefore hypothesized that pain may alter pulmonary circulation in the perinatal period. The hemodynamic response to subcutaneous injection of formalin, which is used in experimental studies as nociceptive stimulus, was evaluated in chronically prepared, fetal lambs. Fetal lambs were ...
Note (first note only)
"Norepinephrine levels did not change during any of the protocols"
"Data suugest that endotracheal suctioning may elevate PAP...(22)" : quid endotracheal balloon?
Wat als ze ipv opiaten bijvoorbeeld een axillair blok met LA zouden doen ? Technisch lijkt me dit haalbaar, ze dissecceren de oksel toch al voor vasculaire access, dus kan er ook een plexus-catheter achtergelaten worden.
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Am J Physiol Lung Cell Mol Physiol, Vol. 288, No. 6. (June 2005)
Abstract
We investigated the pulmonary vascular effects of prophylactic use of sildenafil, a specific phosphodiesterase-5 inhibitor, in late-gestation fetal lambs with chronic pulmonary hypertension. Fetal lambs were operated on at 129 +/- 1 days gestation (term = 147 days). Ductus arteriosus (DA) was compressed for 8 days to cause chronic pulmonary hypertension. Fetuses were treated with sildenafil (24 mg/day) or saline. Pulmonary vascular responses to increase in shear stress and in fetal PaO2 were studied at, respectively, day 4 and 6. Percent ...
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Biol Neonate, Vol. 88, No. 2. (2005), pp. 73-78.
Abstract
OBJECTIVE: Adaptation to extra-uterine life requires dramatic increase in pulmonary blood flow. Mechanisms that induce pulmonary vasodilatation at birth are incompletely understood but include alveolar ventilation, increase in PaO2, and production of vasoactive mediators. We hypothesized that antenatal glucocorticoids (GC) increase pulmonary vasodilatation to birth-related stimuli. STUDY DESIGN: To test this hypothesis, we studied the pulmonary hemodynamic response at birth to mechanical ventilation with low (<10%) and then with high (100%) FiO2 in chronically prepared late-gestation fetal lambs treated or not ...
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Ultrasound in Obstetrics and Gynecology, Vol. 18, No. 6. (12 December 2002), pp. 656-661.
Abstract
<BR><FONT SIZE="+1" >Objective</FONT ></TD ></TR ><TR ><TD >To establish by Doppler ultrasound the effects of acute blockage of umbilical cord vessels on the fetal central circulation.</TD ></TR ><TR ><TD ><BR><FONT SIZE="+1" >Design</FONT ></TD ></TR ><TR ><TD >Experimental study in anesthetized pregnant sheep.</TD ></TR ><TR ><TD ><BR><FONT SIZE="+1" >Methods</FONT ></TD ></TR ><TR ><TD >In 11 anesthetized pregnant sheep (0.66 of gestation), Doppler velocity profiles and/or venous flow rates were recorded in the ductus venosus, the fetal aorta, the umbilical arteries and the ...
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Ultrasound in Obstetrics and Gynecology, Vol. 25, No. 3. (March 2005), pp. 277-281.
Note (first note only)
geen verschillen gevonden in Doppler parameters van pulmonary blood flow tussen TO en controle ondanks een verdriedubbelling van het longvolume.
NB : Doppler-onderzoek gebeurde bij gesedeerde moeders (Xylazine 0.25 mg/kg) : effect op de pulm circ van de foetus ?
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