Effects of acetylsalicylic acid on the ductus arteriosus and circulation in fetal lambs in utero

Patent ductus arteriosus in preterm infants: is early transcatheter closure a paradigm shift?

The optimal management approach of the patent ductus arteriosus (PDA) in premature infants remains uncertain owing the lack of evidence for long-term benefits and the limited analyses of the complications of medical and surgical interventions to date. In recent years, devices suitable to plug the PDA of premature infants (including extremely low birthweight, <1000 g) have become available and several trials have demonstrated successful and safe transcatheter PDA closure (TCPC) in this population. Whether TCPC represents a paradigm shift in PDA management that will result in improved short- and long-term outcomes, less bronchopulmonary dysplasia, improved neurodevelopment, or better long term renal function remains to be seen. Careful rigorous study of the potential benefits of TCPC in this highly vulnerable population in the context of well-designed adequately powered trials is needed prior to widespread adoption of this approach.

Current paradigms and new perspectives on fetal hypoxia: implications for fetal brain development in late gestation

The availability of oxygen to the fetus is limited by the route taken by oxygen from the atmosphere to fetal tissues, aided or diminished by pregnancy-associated changes in maternal physiology and, ultimately, a function of atmospheric pressure and composition of the mother's inspired gas. Much of our understanding of the fetal physiological response to hypoxia comes from experiments designed to elucidate the cardiovascular and endocrine responses to transient hypoxia. Complementing this work is equally impactful research into the origins of intrauterine growth restriction in which animal models designed to restrict the transfer of oxygen from the maternal to the fetal circulation were used. A common assumption has been that outcomes measured after a period of hypoxia are related to cellular deprivation of oxygen and reoxygenation: an assumption based on a focus on what we can see "under the streetlights." Recent studies demonstrate that availability of oxygen may not tell the whole story. Transient hypoxia in the fetal sheep stimulates transcriptomics responses that mirror inflammation. This response is accompanied by the appearance of bacteria in the fetal brain and other tissues, likely resulting from a hypoxia-stimulated release of bacteria from the placenta. The appearance of bacteria in the fetus after transient hypoxia complements the recent discovery of bacterial DNA in the normal human placenta and in the tissues of fetal sheep. An understanding of the mechanism of the physiological, cellular, and molecular responses to hypoxia requires an appreciation of stimuli other than cellular oxygen deprivation: stimuli that we would have never known about without looking "between the streetlights," illuminating direct responses to the manipulated variables.

Prenatal effects of maternal consumption of polyphenol-rich foods in late pregnancy upon fetal ductus arteriosus

Fetal circulation has characteristic features, being morphologically and functionally different from extrauterine circulation. The ductus arteriosus plays a fundamental role in directing the blood flow to fetal inferior body parts. Basically, the ductus arteriosus directs 80-85% of the right ventricular output arising from the superior vena cava, coronary sinus, and a small part from the inferior vena cava to descending aorta. Its histological structure is made up predominantly by a thick muscular layer, differently from the aorta and the pulmonary artery, which increases with gestational age. The fibers have a circumferential orientation, especially at the external layers, facilitating and making effective ductal constriction. These factors may generate lumen alterations which may cause fetal and neonatal complications, such as heart failure, hydrops, neonatal pulmonary hypertension, and even death. Classically, maternal administration of indomethacin and/or other antiinflammatory drugs interfere in prostaglandins metabolism, causing ductal constriction. However, many cases of fetal ductal constriction, as well as of persistent neonatal pulmonary artery hypertension, remain without an established etiology, being referred as "idiopathic." In recent years, a growing body of evidence has shown that herbs, fruits, nuts, and a wide diversity of substances commonly used in daily diets have definitive effects upon the metabolic pathway of inflammation, with consequent inhibition of prostaglandins synthesis. This antiinflammatory action, especially of polyphenols, when ingested during the third trimester of pregnancy, may influence the dynamics of fetal ductus arteriosus flow. The goal of this review is to present these new observations and findings, which may influence dietary orientation during pregnancy.

Enhanced central and conduit pulmonary arterial reservoir function offsets reduced ductal systolic outflow during constriction of the fetal ductus arteriosus

Constriction of the fetal ductus arteriosus (DA) has disparate effects on mean and phasic hemodynamics, as mean DA blood flow is preserved until constriction is severe, but DA systolic and diastolic blood velocities change with only mild constriction. To determine the basis of this disparity and its physiological significance, seven anesthetized late-gestation fetal sheep were instrumented with pulmonary trunk (PT), DA, and left pulmonary artery (PA) micromanometer catheters and transit-time flow probes. Blood flow profile and wave intensity analyses were performed at baseline and during mild, moderate, and severe DA constriction (defined as pulmonary-aortic mean pressure differences of 4, 8, and 14 mmHg, respectively), produced with an adjustable snare. With DA constriction, mean DA flow was initially maintained but decreased with severe constriction (P < 0.05) in conjunction with a reduction (P < 0.05) in PT flow (i.e., right ventricular output). By contrast, DA systolic flow fell progressively during DA constriction (P < 0.001), due to decreased transmission of both early and midsystolic proximal flow-enhancing forward-running compression waves into the DA. However, DA constriction was also accompanied by greater systolic storage of blood in the PT and main PA (P < 0.025), and increased retrograde diastolic flow from compliant major branch PA (P < 0.001). Transductal discharge of these central and conduit PA blood reservoirs in diastole offset systolic DA flow reductions. These data suggest that, during DA constriction in the fetus, enhanced central and conduit PA reservoir function constitutes an important compensatory mechanism that contributes to preservation of mean DA flow via a systolic-to-diastolic redistribution of phasic DA flow.

Diastolic forward flow in the fetal main pulmonary artery and its implication for fetal cardiac cycle evaluation

OBJECTIVES

To examine if the fetal main pulmonary artery diastolic forward flows (MPADFs) are detected consistently, if the waves from fetal MPADFs coincide with those from atrial contractions, and the reproducibility of the cardiac cycle measurements using this technique.

METHODS

Two examiners performed a fetal pulsed Doppler echocardiography of the four chamber (4CV), ductal arch (DA) and short axis (SA) views on 44 women with singleton pregnancies. Time intervals between atrial contraction peaks and those between MPADF peaks were compared. Atrioventricular (AV) and ventriculoatrial (VA) intervals were measured from MPADF waves in DA and SA views and compared between observers. Intraclass correlation coefficients (ICCs) were calculated as a measure of inter-observer reproducibility.

RESULTS

In all observations, MPADFs were demonstrated. The mean time intervals between atrial contraction peaks from 4CV and those between MPADF peaks from DA and SA views were not significantly different. The mean AV and VA intervals were not significantly different between observers. Comparison of measurements of two observers had substantial agreements.

CONCLUSIONS

Our data show that MPADFs can be found consistently and coincide with atrial contractions. As cardiac cycle measurements can be done with considerable reproducibility, this technique may be useful in assessing fetal cardiac cycle.

Aspirin in pregnancy

Aspirin, acetylsalicylic acid, is the most frequently consumed drug in pregnancy, taken mostly without a prescription because of headache or a minor ailment. Numerous preparations containing acetylsalicylic acid are freely available over the counter under a variety of proprietary names, and in many cases pregnant women and their doctors may be unaware that aspirin is being taken.

The ductus arteriosus

The ductus arteriosus is a large vessel which connects the pulmonary trunk with the aorta. During fetal life it serves together with the foramen ovale as a shunt at cardiac level. Due to a complex regulatory mechanism it is capable of maintaining patency during fetal life and of rapid closure after birth. However, in premature neonates ductal patency frequently persists, an occurrence which may even be favourable in some situations. Recent investigations on the ductus arteriosus have provided new information about the regulatory mechanisms involved with its function. Initially, most studies on the fetal ductus arteriosus were conducted in animals. With the introduction of the combined use of two dimensional real-time and Doppler ultrasound systems the opportunity became available to study blood flow within the ductus arteriosus in the human fetus and neonate in a noninvasive manner. The increasing use in obstetric care of cyclo-oxygenase inhibitors for tocolysis and for prevention of the development of pregnancy induced hypertension and pre-eclampsia justifies the re-evaluation of the potential adverse effects of these drugs on the ductus arteriosus.

Usefulness of indomethacin for patent ductus arteriosus in full-term infants

The aim of this retrospective study was to evaluate the effectiveness of indomethacin therapy for patent ductus arteriosus (PDA) in full-term infants. The patients were 41 full-term infants with a PDA birth weight (BW) > or =2500 g and a gestational age (GA) > or =37 weeks. The echocardiographic evaluation and medical management of PDA in these infants was similar to that for PDA in low-birth-weight infants. Indomethacin (0.2-0.25 mg/kg/dose) was given intravenously at 12-24-hour intervals within 23 days of birth. Of the 41 infants, 12 showed complete closure, and 13 showed improvement of clinical symptoms. These 25 infants were classified as the responder group (61%). The other 16 infants, who did not show improvement in clinical symptoms, were classified as the nonresponder group. Statistical analysis revealed no difference between the two groups regarding GA, BW, Apgar score at 1 minute, minimum diameter of the DA before treatment, the average age at the initiation of treatment, and DA flow pattern. No severe adverse reactions were observed in any infant. Indomethacin therapy appears to be an effective medical treatment option for PDA in full-term symptomatic infants prior to considering surgical treatment.

Patent Ductus Arteriosus and Respiratory Outcome in Premature Infants

A persistent ductus arteriosus is a common event in preterm infants. The systemic-to-pulmonary shunting that occurs as the pulmonary vascular resistance decreases after birth can have significant cardiovascular and respiratory consequences. Acute pulmonary effects include pulmonary edema and hemorrhage, worsened lung mechanics and deterioration in gas exchange with hypoxemia and hypercapnia. The increased pulmonary blood flow can also produce damage to the capillary endothelium and trigger an inflammatory cascade. This, plus the need for longer and more aggressive mechanical ventilation, can explain the association between patent ductus arteriosus and an increased risk for bronchopulmonary dysplasia in extremely premature infants.

The endothelin system in pulmonary hypertension

Pulmonary hypertension (PH) may result from numerous clinical entities affecting the pulmonary circulation primarily or secondarily. It is recognized that vascular endothelial dysfunction contributes to the development and perpetuation of PH by creating an imbalance between vasodilating and antiproliferative forces and between vasoconstrictive and proliferative forces. In that context, endothelin-1 (ET-1) overproduction was rapidly targeted as a plausible contributor to the pathogenesis of PH. The lung is recognized as the major site for ET production and clearance. In all animal models of PH studied, circulating plasma ET-1 levels are elevated, accompanied by an increase in lung tissue expression of the peptide. The use of selective ETA and dual ETA-ETB receptor antagonists in these models both in prevention and in therapeutic studies have confirmed the contribution of ET-1 to the rise in pulmonary vascular tone, pulmonary medial hypertrophy, and right ventricular hypertrophy. This is found consistently in models affecting the pulmonary circulation primarily or producing PH secondarily. Recent clinical trials in patients with pulmonary arterial hypertension have confirmed the therapeutic effectiveness of ET-receptor antagonists in humans. We offer a systematic review of the pathogenic role of the ET system in the development of PH as well as the rationale behind the preclinical and ongoing clinical trials with this new class of agents.

Abraham Morris Rudolph: an appreciation

Dr Abraham Rudolph is one of the most distinguished pediatric cardiologists in the world. He entered pediatric cardiology (almost by accident) when the subject was still in its infancy and was present at--and indeed contributed to--most of its advances. He is best known for his studies on the pathophysiology of congenital heart diseases and for imaginative studies of fetal cardiovascular development and the transition to postnatal life.

Analysis of nonsteroidal antiinflammatory drugs in meconium and its relation to persistent pulmonary hypertension of the newborn

OBJECTIVE

The objective of this study was to detect fetal exposure to nonsteroidal antiinflammatory drugs (NSAIDs) by meconium analysis and to determine the relationship between fetal exposure to NSAIDs and the development of persistent pulmonary hypertension of the newborn (PPHN).

METHODS

In a case-control study of the inborn and outborn nurseries of a large urban medical center, meconium was collected from 101 newborn infants (40 with the diagnosis of PPHN based on clinical or echocardiographic criteria and 61 randomly selected, healthy, term infants [control]) and analyzed for NSAIDs (ibuprofen, naproxen, indomethacin, and aspirin) by gas chromatography/mass spectrometry. The risk of developing PPHN was determined in infants who were exposed antenatally to NSAID.

RESULTS

Infants with PPHN (n = 40) had a mean gestation of 38.9 weeks and birth weight of 3524 g, which were similar to the those of the control group (n = 61). However, the incidence of low Apgar scores (</=6) at 1 minute and 5 minutes was significantly higher in the PPHN group than in the control group. The diagnoses associated with PPHN were primary PPHN (25%), meconium aspiration syndrome (35%), respiratory distress syndrome (20%), low Apgar score/asphyxia (12.5%), and pneumonia/sepsis (8%). Mean duration of ventilator support for the PPHN group was 11 days. Nitric oxide (NO) was given to 19 infants (47.5%) for a mean duration of 25.4 hours. Fourteen of the 19 infants who were treated with NO (74%) required extracorporeal membrane oxygenation, and 2 died. The overall incidence of positive NSAID in meconium in the study population (n = 101) was 49.5%: 22.8% were positive for ibuprofen, 18.8% for naproxen, 7.9% for indomethacin, and 43.6% for aspirin. There was poor agreement (Cohen's kappa = 0.09) between maternal history of NSAID use and NSAID detection in meconium. PPHN was significantly associated with 1) the presence of at least 1 NSAID in meconium (odds ratio [OR] = 21.47; 95% confidence interval [CI] = 7.12-64.71) or 2) the presence in meconium of aspirin (OR = 8.09; 95% CI = 3.27-20.10), ibuprofen (OR = 12.89; 95% CI 3.93-42.32), or naproxen (OR = 3.31; 95% CI = 1.17-9.33). By logistic regression analysis, low Apgar scores at 1 and 5 minutes and the antenatal exposure to aspirin, naproxen, and ibuprofen were significantly associated with PPHN and treatment with inhaled NO or extracorporeal membrane oxygenation.

CONCLUSION

We confirm by meconium analysis the results of previous studies that demonstrated that the use of NSAIDs during pregnancy, particularly aspirin, ibuprofen, and naproxen, is high; is grossly underestimated by maternal history; and is significantly associated with PPHN. Thus, the easy access to over-the-counter NSAIDs of pregnant women should be reevaluated, and the potential dangers of these drugs to the newborn infant should be more effectively promoted.

Effects of maternal ingestion of low-dose aspirin on the fetal cardiovascular system

OBJECTIVE

Our purpose was to assess fetal central and regional hemodynamics in normal fetuses using two-dimensional, range-gated pulsed Doppler echocardiography in pregnant women on chronic baby aspirin regimen (87 mg).

STUDY DESIGN

Fifteen fetuses exposed to maternal chronic ingestion of baby aspirin were compared with 26 control fetuses. Longitudinal studies of the umbilical artery waveform and blood flow through the fetal right and left ventricles were obtained every 4 weeks during gestation in a group of fetuses exposed to daily maternal intake of 87 mg of aspirin. Pulsed Doppler waveforms were obtained below the tricuspid and mitral valves, at the level of the descending aorta (below the ductus), and at the level of the fetal renal artery as it enters the kidney. All tracings were recorded on a strip chart and analyzed with a digital light-pen and graphic overlay system. Peak systolic velocity and minimal diastolic velocity were obtained for the umbilical and fetal renal artery. Peak flow velocity and velocity time integral of the pulsed Doppler waveforms of the atrioventricular valves were calculated. Acceleration time/ejection time ratio was obtained for the descending aorta.

RESULTS

No significant differences were found among the two groups in either central or regional circulation.

CONCLUSION

Chronic daily maternal ingestion of baby aspirin does not significantly affect the central and regional circulation of the fetus.

Fetal ductus arteriosus ligation. Pulmonary vascular smooth muscle biochemical and mechanical changes

To evaluate the smooth muscle mechanical and biochemical changes associated with persistent pulmonary hypertension syndrome of the newborn, we studied 31 fetal sheep in which the ductus arteriosus was ligated at 125 days of gestation. Sixty-one noninstrumented and six sham-operated fetuses served as controls. All animals were delivered by cesarean section at 137-140 days of gestation, and the experimental group had the ductus arteriosus ligated for 12 +/- 3 days. The ligated group demonstrated a higher mean (+/- SEM) pulmonary artery pressure (72.3 +/- 3.8 versus 54.1 +/- 2 mm Hg, p < 0.01) and right ventricular mean free wall weight (12.5 +/- 0.7 versus 6.8 +/- 0.3 g, p < 0.01) as compared with the sham-operated group. Significant changes in the pulmonary vascular smooth muscle of the ligated group were observed. The myosin content of vessels from the second through fifth generation demonstrated a significant increase in actin and myosin content (p < 0.01), but given their disproportional changes, the noninstrumented group demonstrated a lower actin/myosin ratio than the experimental group (p < 0.01). Changes in the myosin heavy chain isoform stoichiometry, characterized by an increase in both the mean high/low myosin heavy chain isoform ratio (1.8 +/- 0.3 versus 1.0 +/- 0.1, p < 0.05) and the nonmuscle isoform as a percentage of the total myosin heavy chain (12.4 +/- 0.7% versus 2.7 +/- 0.9%, p < 0.01), were also observed in the ligated as compared with the noninstrumented animals. In addition, the muscle Mg-ATPase activity was significantly (p < 0.05) reduced in the experimental group.(ABSTRACT TRUNCATED AT 250 WORDS)

Indomethacin for the treatment of polyhydramnios: a case of constriction of the ductus arteriosus

Prenatal administration of indomethacin for the treatment of polyhydramnios at 27 weeks' gestation resulted in the rapid restoration of normal amniotic fluid volume. However, after 16 days therapy, fetal echocardiography revealed constriction of the fetal ductus arteriosus which did not reverse during the 17 days after the therapy was discontinued. The constriction resulted in right heart failure but no long-term effects on the infant after birth. Indomethacin is a powerful treatment for polyhydramnios but its use requires close monitoring of the fetal heart.

The placenta, PGE2 and parturition

It is proposed that prostaglandin E2 (PGE2), secreted by the fetal placenta of the sheep, acts as a circulating regulator of the physiological function of many fetal organs (tissue) in a way analogous to catecholamines in the adult. The specificity of PGE2 action in different tissues is determined by three different receptor subtypes which regulate intracellular calcium concentrations via the IP3 pathway, or cyclic AMP concentrations via the adenylcyclase system. The placenta, by secreting PGE2 (and possibly other factors such as adenosine), modifies the function of key organ systems allowing the fetus to survive and develop in the aqueous environment of the uterus. During fetal development, fetal organs and metabolic pathways can mature while their function is suppressed by placental PGE2. At birth, by ligating the cord and removing the placenta as the source of these inhibitory substances, the newborn is able to adapt readily to its new environment with fully-functional, mature organ systems. This paper discusses how placental PGE2 may regulate fetal breathing movements, whether the removal of placental PGE2 is involved in the initiation of continuous breathing at birth, and whether it suppresses the activity of the peripheral chemoreceptors during fetal life. The ability of PGE2 to maintain a widely patent ductus arteriosus, to suppress non-shivering thermogenesis, to stimulate fetal insulin secretion and to suppress the hepatic gluconeogenic pathway in the fetus is also discussed. Finally, the ability of PGE2 to activate the fetal hypothalamo-pituitary-adrenal axis is discussed, raising the possibility that the placenta also plays a key role in the initiation of birth in this species.

Purinoceptors in the pulmonary circulation of the rat and their role in hypoxic vasoconstriction

1. P2-purinoceptors have been characterized in the systemic circulation of a variety of species but little is known about their nature in the pulmonary vasculature. 2. In the isolated, blood perfused and ventilated lung of the rat the P2x selective analogues alpha,beta-methylene ATP(alpha,beta-meATP) (25 micrograms) and beta,gamma-methylene ATP (400 micrograms) caused a rise in pulmonary artery pressure (127 +/- 32% and 110 +/- 23% increase respectively, n = 6), demonstrating the existence of vasoconstrictor P2 receptors in the pulmonary circulation. 3. Repeated boluses of alpha,beta-meATP resulted in complete desensitization of the constrictor response to beta,gamma-meATP, but a small vasodilator response remained indicating unopposed stimulation of P2y receptors. The desensitization by alpha,beta-meATP had no effect on angiotensin II-induced vasoconstriction. 4. After desensitization of the vasoconstrictor P2 receptors with alpha, beta-meATP, hypoxic pulmonary vasoconstriction remained intact, indicating that these receptors are not involved in this response.

Right ventricular concentric hypertrophy and left ventricular dilatation by ductal constriction in fetal rats

Fetal cardiac changes due to ductal constriction by maternal ingestion of nonsteroidal anti-inflammatory drugs were studied morphologically in near-term rats as an animal model, and results were compared with values of control 1 (C1, twenty-first day) and control 2 (C2, twenty-second day). The fetal ductus was constricted (-70%) (p less than 0.05) by maternal administration of 10 mg/kg indomethacin. Dilatation of the right ventricle and evidence of congestive heart failure including increased pericardial effusion (+200%) (p less than 0.05) and an increase in water content in the abdominal wall were present at 1, 4, and 8 hours after drug administration. At 24 hours after drug administration, concentric right ventricular hypertrophy was shown by a diminished right ventricular cavity (-36% vs. C2) (p less than 0.05), increased right ventricular wall thickness (+70% vs. C2) (p less than 0.05), and increased right ventricular mass (+31% vs. C1) (p less than 0.05). Left ventricular dilatation was indicated by an increased cavity volume (+87% vs. C2) (p less than 0.05) and increased muscle mass (+29% vs. C1 [p less than 0.05] or +9% vs. C2 [p greater than 0.05]). Both the wet and dry weights of the ventricles were increased. In conclusion, fetal ductal constriction caused right ventricular hypertrophy, diminished right ventricular cavity, and left ventricular dilatation and hypertrophy at 24 hours after drug administration in rats after initial congestive failure.

Autoimmune disease in pregnancy

Autoimmunity, whether present in a recognized syndrome such as systemic lupus erythematosus or represented by the production of subclasses of autoantibodies, adversely affects reproduction. While fertility of patients with autoimmune disorders is generally unimpaired, important exceptions exist. Recent data regarding the impact of intercurrent pregnancy upon women with SLE suggest that the overall course of this disorder is not affected. The impact of SLE and related autoimmune phenomena during pregnancy primarily relates to adverse fetal outcome. Pregnancy wastage is excessive, and premature delivery and poor fetal growth are commonly encountered. The occurrence of fetal complications correlates with the level of maternal disease activity and the presence of specific autoantibodies. Management of pregnancy complicated by SLE or the production of autoantibodies associated with poor reproductive outcome should be directed at maintaining maternal disease quiescence. The adverse effect of the maternal disorder on fetal growth and development far outweighs actual or theoretical risks attributable to maternal drug therapy.

The role of eicosanoids in paediatrics

Prostanoids are unsaturated cyclic fatty acids, are synthesized primarily from arachidonic acid, and, like the leukotrienes, belong to the growing family of eicosanoids. As tissue hormones, prostanoids act on specific receptors near their site of synthesis and degradation. Prostanoids operate as modulators and mediators in a large spectrum of physiological processes. They are involved in the regulation of maternal and fetal circulation, patency of the ductus arteriosus, platelet-vessel wall interaction and kidney function. Besides their physiological function in protecting organ perfusion under stress conditions, they are also involved in diseases as described in the hyperprostaglandin E2-syndrome or--together with leukotrienes--in inflammatory processes. More specific pharmacological tools than the nonsteroidal antiinflammatory drugs, such as receptor antagonists, selective synthesis inhibitors, and eicosanoid analogues offer the prospect of enriching our arsenal of pharmacotherapeutic interventions in a variety of diseases. Before active intervention, however, more and specific biochemical analyses are required to identify the pathophysiological role of eicosanoid.

Patent ductus arteriosus in the neonate

Recently there has been a significant reappraisal of the role of PDA in the context of neonatal cardiopulmonary disease. This article reviews surgical intervention, pharmacologic treatment, and assessment of ductal patency in the neonate.

Effects of indomethacin on cardiac output distribution in normal and asphyxiated piglets

We determined the effect of breathing 9% CO2/10% O2/81% N2 (asphyxia) on cardiac output distribution (microspheres) in 4-5 day old unanesthetized, chronically instrumented piglets prior to and following intravenous indomethacin administration. Thirty minutes of asphyxia caused PaCO2 to increase from 35 +/- 2 mmHg to 66 +/- 2 mmHg, PaO2 to decrease from 73 +/- 4 mmHg to 41 +/- 1 mmHg, and pH to decrease from 7.52 +/- 0.05 to 7.21 +/- 0.07. Arterial pressure was increased slightly but cardiac output was not changed significantly. Asphyxia caused blood flow to the brain, diaphragm, liver, heart, and adrenal glands to increase while causing decreases in blood flow to the skin, small intestine, and colon. Blood flows to the stomach and kidneys tended to decrease, but the changes were not significant. Treatment with indomethacin during asphyxia did not alter arterial pressure or cardiac output but decreased cerebral blood flow to the preasphyxiated level and decreased adrenal blood flow about 20%. Indomethacin did not alter blood flow to any other systemic organ. At this time the piglet was allowed to breathe air for 2.5 hr undisturbed. Two and a half hours after indomethacin administration, blood flows to all organs returned to the preasphyxia control levels with the exception of cerebral blood flow which was reduced (93 +/- 13 to 65 +/- 7 ml/100 g X min). Three hours after indomethacin administration, the cerebral hyperemia caused by asphyxia was less (134 +/- 17 ml/100 g X min) than prior to indomethacin (221 +/- 15 ml/100 g X min). Indomethacin did not alter the asphyxia-induced changes to any other systemic organ.(ABSTRACT TRUNCATED AT 250 WORDS)

Prostanoids in cortical subarachnoid cerebrospinal fluid and pial arterial diameter in newborn pigs

These studies were designed to investigate the relationship between cerebral prostanoid synthesis and pial arterial caliber in chloralose-anesthetized newborn pigs with normal blood gases and pH and during combined arterial hypoxia and hypercapnia. Piglets less than 5 days old were equipped with closed cranial windows to allow direct observation of pial vessels, application of prostaglandin E2, and sampling of cortical subarachnoid cerebrospinal fluid. We found that prostanoids accumulate in cerebrospinal fluid on the cortical surface. The only prostanoid detected in arterial blood was 6-keto-prostaglandin F1 alpha [442 +/- 74 pg/ml (radioimmunoassay)]. Only small quantities of 6-keto-prostaglandin F1 alpha (214 +/- 53 pg/ml) and thromboxane B2 (122 +/- 18 pg/ml) were found in cerebrospinal fluid from the cisterna magna. Higher concentrations of 6-keto-prostaglandin F1 alpha (1056 +/- 159 pg/ml), thromboxane B2 (229 +/- 64 pg/ml), and prostaglandin E2 (4235 +/- 269 pg/ml) were found in cortical subarachnoid fluid. In contrast to arterial and cisternal concentrations, the concentrations of 6-keto-prostaglandin F1 alpha, thromboxane B2, and prostaglandin E2 in cortical subarachnoid fluid were increased reversibly by ventilation with 9% carbon dioxide, 10% oxygen, (6-keto-prostaglandin F1 alpha, 5436 +/- 1576 pg/ml; thromboxane B2, 694 +/- 122 pg/ml; and, prostaglandin E2, 12,455 +/- 3688 pg/ml). Further, pial arteries dilated in response to topical application of prostaglandin E2 at the concentration that was found in cortical subarachnoid fluid during combined hypoxia and hypercapnia. Systemic administration of indomethacin trihydrate (5 mg/kg) markedly reduced cortical subarachnoid fluid prostanoid concentrations and attenuated the pial artery vasodilation induced by combined hypoxia and hypercapnia.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiovascular changes due to premature closure of the ductus arteriosus: a mathematical model

Changes in the fetal cardiovascular system due to premature closure of the ductus arteriosus are described using a previously validated mathematical model. Results of the simulated closure of the ductus arteriosus are compared with reported results from animal experiments in which the ductus arteriosus was closed pharmacologically with prostaglandin synthetase inhibitors. The computed cardiovascular changes after ductus closure in the model resemble the changes obtained by administration of indomethacin. This suggests that the central cardiovascular effects of indomethacin (insofar as described here) can be completely attributed to closure of the ductus.

Increased thromboxane A2 production but normal prostacyclin by the placenta in hypertensive pregnancies

The production of vasodilatory, antiaggregatory prostacyclin (PGI2) and vasoconstrictory, proaggregatory thromboxane A2 (TxA2) by the placenta was studied in the cases of hypertensive pregnancy complications by superfusing pieces from maternal and fetal sides of placentae of 9 pre-eclamptic, 6 hypertensive and 11 healthy women in vitro and measuring the release of 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) and thromboxane B2 (TxB2), the breakdown products of PGI2 and TxA2 respectively, from the superfusate. Both sides of the placentae from the controls produced 6-keto-PGF1 alpha (maternal side 0.5 +/- 0.1 ng/g/min dry weight of tissue, mean +/- SEM; fetal side 0.7 +/- 0.2 ng/g/min) and TxB2 (maternal side 2.5 +/- 0.4 ng/g/min; fetal side 2.7 +/- 0.5 ng/g/min) with no correlation between the two. The 6-keto-PGF1 alpha production was normal in hypertensive complications whereas the TxB2 production was increased on the fetal side of the placentae obtained from the pre-eclamptic (3.7 +/- 0.3 ng/g/min: p less than 0.05) and hypertensive women (4.1 +/- 0.4 ng/g/min; p less than 0.025). This may explain the occurrence of microthrombi and infarctions in placentae of hypertensive women.

The central control of fetal breathing and skeletal muscle movements

Breathing movements in the sheep fetus have been observed from a gestational age of about 40 days. From 95 to 115 days fetal breathing movements are almost continuous, interrupted by apnoea rarely exceeding 2 min. From 115 days until term (about 147 days) breathing and movements of the trunk and limbs are episodic. Breathing normally occurs only during rapid-eye-movement sleep as identified by low-voltage cortical electrical activity. Active movements of the neck muscles occur predominantly in high-voltage electrocortical activity. Hypercapnia or acid cerebrospinal fluid perfusion cause an increase in the regularity and depth of breathing when present, and recruit intercostal and laryngeal abductor activity. Isocapnic hypoxia, however, in contrast to the hyperventilation seen postnatally, causes arrest of fetal breathing movements. This effect is due to a central inhibition. Section of the brain stem, from the caudal hypothalamus rostrally, causes dissociation of fetal breathing movements and electrocortical activity into independent rhythms. Section of the brain stem caudally, in the upper pons or at the inferior colliculus, also causes a dissociation of electrocortical activity from breathing movements, which become almost continuous. Isocapnic hypoxia causes an increase in the rate and depth of breathing movements. It is concluded that the arrest of breathing in intact fetal lambs is not due to a direct effect on the respiratory centre in the medulla. The lumbar polysynaptic flexor reflex response becomes episodic after 115 days gestation but, in contrast to fetal breathing movements, is enhanced during high-voltage electrocortical activity. Isocapnic hypoxia arrests movements of the fetal limbs and trunk and inhibits the lumbar flexor reflex. This inhibition of the reflex is prevented by section of the spinal cord at T12, but persists after section of the brain stem in the upper pons. It is attributed to an action on the medulla, independent of the systemic arterial chemoreceptors. Small doses of pentobarbitone (5 mg/kg) cause arrest of fetal breathing movements by a suprapontine mechanism, abolished by brain stem transection, and inhibition of the lumbar flexor reflex by an action on the spinal cord, persisting after transection at T12. Inhibitors of prostaglandin synthetase (indomethacin, meclofenamate or aspirin) induce continuous fetal breathing movements, while prostaglandin E2 arrests fetal breathing. The site of action is on the medulla, as shown by section of the brain stem and of afferents from the systemic arterial chemoreceptors.(ABSTRACT TRUNCATED AT 400 WORDS)

Analgesics during pregnancy

The thalidomide tragedy of the late 1950s clearly proved the need for caution, and questionable drug use should always be avoided. The teratogenic potential of a drug is related to dosage and time of administration. During blastogenesis, fetal death may occur; during embryogenesis, deformity may develop; and during the last trimester, functional anomalies or "covert embryopathy" may be seen. Finally, the benefit to risk ratio of every drug must be carefully weighed, and only those with proved safety to the feto-maternal unit should be prescribed. Aspirin may be administered to the pregnant woman as an anti-inflammatory agent but in the lowest therapeutic dosage. In the later stages of pregnancy, however, aspirin should be avoided since it may prolong labor, lead to greater blood loss during delivery, and increase the incidence of stillbirths. The pyrazolones, although not associated with teratogenic side effects, may lead to sometimes fatal agranulocytosis and, accordingly, are not recommended in pregnancy. Acetaminophen is the analgesic and antipyretic of choice during all phases of pregnancy.

Constriction of fetal ductus arteriosus by non-steroidal anti-inflammatory drugs

Transplacental effects of 24 non-steroidal anti-inflammatory drugs (NSAIDs) on the fetal ductus arteriosus were studied in full-term pregnant rats using the whole-body freezing technique. All sixteen acidic NSAIDs constricted the fetal ductus in a dose-dependent relationship, but considerable differences in the intensity of effect was noticed with the clinical dose of each drug. Six of the eight basic NSAIDs did not constrict the fetal ductus at 50 to 100 times the usual clinical dose. It is concluded that acidic NSAIDs probably should not be administered to pregnant women. However, it may be established in the future that some basic NSAIDs can be administered safely to pregnant women without hazardous effect on the fetus.

Persistent pulmonary hypertension in the neonate: diagnosis and management

PPHN should be recognized as a clinical condition associated with a number of pulmonary and systemic diseases. Present therapy has resulted in increased survival, but the aggressive methods required to produce improvement necessitate a clear understanding of the underlying pathophysiology in order to minimize sequelae.

Differential inhibition of fetal vascular prostacyclin and platelet thromboxane synthesis by nonsteroidal anti-inflammatory drugs in humans

To study the synthesis of proaggregatory, vasoconstricting thromboxane A2 (TxA2) by human fetal platelets we evaluated the formation of its stable metabolite thromboxane B2 (TxB2) during thrombin-induced spontaneous clotting of blood from the umbilical vein of 13 healthy infants. We further compared the effects of acetylsalicylic acid, indomethacin, naproxen sodium and diclofenac sodium on platelet TxA2 production in response to thrombin-induced aggregation during spontaneous clotting, and on prostacyclin (PGI2) production by umbilical arteries in a superfusion system by measuring the 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) concentration in the superfusate. For every drug four concentrations covering the clinically significant range were studied. The basal production of TxB2 by fetal platelets (181.5 +/- 22.5 ng/ml, mean +/- SEM) was comparable with that of adults (216.1 +/- 11.5 ng/ml). The concentrations of the drugs needed for 50% inhibition of TxB2 generation were 19.0 mumol/l for acetyl-salicylic acid, 0.09 mumol/l for indomethacin, 0.06 mumol/l for diclofenac sodium and 4.2 mumol/l for naproxen sodium. The basal production of 6-keto-PGF1 alpha by umbilical arteries was 24.5 +/- 3.2 ng/min/g. The concentrations of the drugs needed for 50% inhibition of 6-keto-PGF1 alpha production were 360.0 mumol/l for acetylsalicylic acid, 4.0 mumol/l for indomethacin, 2.3 mumol/l for diclofenac sodium and 15.0 mumol/l for naproxen sodium. Thus fetal platelet cyclo-oxygenase was 4-44 times more sensitive to these prostaglandin synthesis inhibitors than umbilical artery cyclo-oxygenase.

Placental drug transfer: effects of gestational age and species

The available evidence suggests that for most drugs, adverse effects in the fetus may vary with gestational state and among species due to: (i) changes in the fetal exposure to the drug (i.e. due to changes in the pharmacokinetics of the drug in the mother and/or the fetus), or to (ii) changes in the susceptibility of the fetus to the drug. The fetal exposure to a drug during gestation is influenced more by the varying capacity of mother and/or fetus to eliminate the drug than by any intrinsic 'barrier' phenomenon at the placenta. Although differential maternal/fetal protein binding, active transplacental transport processes and 'ion-trapping' effects may influence the fetal exposure of some drugs, the main mechanisms by which fetal exposure may be modulated during pregnancy are via the capacity for irreversible drug elimination--by the fetus or, less often, by the placenta. The susceptibility of a fetus to adverse drug reactions is determined by the ontogeny of vital processes and the nature of the interaction between the drug and the process. Hence 'gestational state' and 'species' dependent differences in adverse drug effects, in the presence of a constant level of exposure of drug, reflect the time dependent appearance of these processes and the differences in ontogeny of the processes among species. At present, no studies have attempted to relate the measured fetal drug exposure to the intensity of a drug response at different stages of gestation or among species. Although there is a dearth of information in this field, it is apparent that in all species the placentas of all species pose little obstruction to the passage of xenobiotics (including drugs), to the fetus. The consequence of this exposure will depend on a myriad of pharmacokinetic and pharmacodynamic considerations for a given substance in a given species. Hence the outcome cannot be predicted, but must be empirically determined. Extrapolation of findings among different drugs, species and gestational states must be undertaken with caution, recognizing the above considerations and limitations.

Twenty-five years of progress in the medical treatment of pediatric and congenital heart disease

In the past 25 years there has been a many-fold increase in the prospect that with early recognition and modern treatment the newborn with critical congenital heart disease will reach adult life in a healthy condition, prepared to earn a living and to function as a spouse and as a parent. Advancements in the medical treatment of congenital heart disease may create less public acclaim than may surgical treatment but many purely medical developments provide the basis for achieving ultimate surgical success and, by judicious use of some forms of medical treatment, operation can be avoided altogether. The eight major contributions to patient care that are discussed in this review and the 35 that are simply listed are merely examples of the many developments that have occurred in the past 25 years. These include: 1) the organization of pediatric cardiology and the contribution of volunteer health organizations, 2) continuing medical education aimed at promoting early diagnosis of congenital heart disease and prompt referral to a cardiac center, 3) advances in the technology of cardiac catheterization, 4) Rashkind's balloon atrial septostomy and other catheter manipulative procedures, 5) pharmacologic manipulation of the ductus, 6) beta-adrenergic blockade for control of a variety of problems, including paroxysmal hypoxemic attacks, certain arrhythmias and relief of symptoms in hypertrophic cardiomyopathy, 7) echocardiography, and 8) advances in arrhythmias, electrophysiologic studies and use of pacemakers.

Uptake and metabolism of prostaglandin E1 in isolated perfused fetal, newborn and adult rabbit lungs

PGE1 has been used to maintain the patency of the ductus arteriosus in newborns with pulmonary hypertension. However, it is known that adult lungs avidly take up and metabolize circulating PGE1. We compared the ability of isolated perfused lungs from previable, 26-day gestation, fetal rabbits; newborn rabbits (within 12 hours of birth) and 3 month old adult rabbits to metabolize a 20-second bolus of PGE1. The concentration of PGE1 infused was approximately 2 orders of magnitude below the Km for the PGE1 uptake process so that first order uptake kinetics are assured. The retention time of a vascular marker dye was monitored as an index of pulmonary vascular surface area. In all three sizes of lungs perfusate flow was adjusted to produce an approximately 7 second dye retention time. At these flows the adult lungs inactivate about 45 percent of the infused PGE1. In contrast, fetal and newborn rabbit lungs both inactivate about 22 percent of the infused PGE1. We conclude that the ability of the lung to take up and metabolize circulating PGE1 is markedly reduced in premature and term newborns.

Postoperative fetal circulation: POFC

Active pulmonary vasoconstriction and subsequent right-to-left atrial and/or ductal shunting of venous blood may influence the course of many neonatal cardiorespiratory disorders. The term "persistent fetal circulation" has been applied to these infants. This report concerns the late occurrence of fetal circulation after major intraabdominal operative procedures in two neonates. The first patient was a full-term, 3.6-kg infant with a covered, large liver-containing omphalocele. Cyanosis, hypoxia, and a right-to-left shunt were present at birth, but were improved by 24 hr of life. Primary repair was delayed for 6 days, in the belief that fetal circulation was unlikely to recur. On day 7, primary fascial closure of the omphalocele was followed by severe hypoxia secondary to right-to-left shunt, documented to be due to postoperative fetal circulation (POFC). The second was a 1600-g premature infant who was well until noted to be lethargic on the fourth day of life. Radiologic findings of pneumoperitoneum led to laparotomy and closure of a spontaneous gastric perforation. Twenty-four hours later the patient developed severe hypoxia and a right-to-left shunt at the atrial level was documented with contrast echocardiogram, again supporting the diagnosis of POFC. Each patient survived and has a normal heart. Both patients responded to hyperventilation and/or tolazoline therapy. Contrast echocardiography was a helpful, noninvasive means of establishing the diagnosis. This diagnosis should be considered in postoperative neonates after more common cardiac and pulmonary causes of hypoxia are excluded.