A novel approach to the management of pregnancies complicated by uteroplacental insufficiency and previous stillbirth

Early and late preeclampsia are characterized by high cardiac output, but in the presence of fetal growth restriction, cardiac output is low: insights from a prospective study

BACKGROUND

Preeclampsia and fetal growth restriction are considered to be placentally mediated disorders. The clinical manifestations are widely held to relate to gestation age at onset with early- and late-onset preeclampsia considered to be phenotypically distinct. Recent studies have reported conflicting findings in relation to cardiovascular function, and in particular cardiac output, in preeclampsia and fetal growth restriction.

OBJECTIVE

We conducted this study to examine the possible relation between cardiac output and peripheral vascular resistance in preeclampsia and fetal growth restriction.

STUDY DESIGN

We investigated maternal cardiovascular function in relation to clinical subtype in 45 pathological pregnancies (14 preeclampsia only, 16 fetal growth restriction only, 15 preeclampsia and fetal growth restriction) and compared these with 107 healthy person observations. Cardiac output was the primary outcome measure and was assessed using an inert gas-rebreathing method (Innocor), from which peripheral vascular resistance was derived; arterial function was assessed by Vicorder, a cuff-based oscillometric device. Cardiovascular parameters were normalized for gestational age in relation to healthy pregnancies using Z scores, thus allowing for comparison across the gestational range of 24-40 weeks.

RESULTS

Compared with healthy control pregnancies, women with preeclampsia had higher cardiac output Z scores (1.87 ± 1.35; P = .0001) and lower peripheral vascular resistance Z scores (-0.76 ± 0.89; P = .025); those with fetal growth restriction had higher peripheral vascular resistance Z scores (0.57 ± 1.18; P = .04) and those with both preeclampsia and fetal growth restriction had lower cardiac output Z scores (-0.80 ± 1.3 P = .007) and higher peripheral vascular resistance Z scores (2.16 ± 1.96; P = .0001). These changes were not related to gestational age of onset. All those affected by preeclampsia and/or fetal growth restriction had abnormally raised augmentation index and pulse wave velocity. Furthermore, in preeclampsia, low cardiac output was associated with low birthweight and high cardiac output with high birthweight (r = 0.42, P = .03).

CONCLUSION

Preeclampsia is associated with high cardiac output, but if preeclampsia presents with fetal growth restriction, the opposite is true; both conditions are nevertheless defined by hypertension. Fetal growth restriction without preeclampsia is associated with high peripheral vascular resistance. Although early and late gestation preeclampsias are considered to be different diseases, we show that the hemodynamic characteristics of preeclampsia were unrelated to gestational age at onset but were strongly associated with the presence or absence of fetal growth restriction. Fetal growth restriction more commonly coexists with preeclampsia at early gestation, thus explaining the conflicting results of previous studies. Furthermore, antihypertensive agents act by reducing cardiac output or peripheral vascular resistance and are administered without reference to cardiovascular function in preeclampsia. The underlying pathology (preeclampsia, fetal growth restriction, preeclampsia and fetal growth restriction) defines cardiovascular phenotype, providing a rational basis for choice of therapy in which high or low cardiac output or peripheral vascular resistance is the predominant feature.

Transdermal nitroglycerin in patients with severe pre-eclampsia with placental insufficiency: effect on uterine, umbilical and fetal middle cerebral artery resistance indices

OBJECTIVES

To evaluate the effect of transdermal nitroglycerin on Doppler velocity waveforms of the uterine, umbilical and fetal middle cerebral arteries in patients with severe pre-eclampsia.

METHODS

This was a prospective study of 30 singleton pregnancies (gestational age range: 24-31 weeks) with severe pre-eclampsia and abnormal uterine and umbilical artery Doppler waveforms. We compared maternal blood pressure as well as the resistance index (RI) and the pulsatility index (PI) of the uterine, umbilical and fetal middle cerebral arteries before and after application of a transdermal nitroglycerin patch (average dose 0.4 mg/h) for a period of 3 days. Intra-day comparisons before and after administration of nitroglycerin and a comparison between days 0 (no patch) and 3 after administration of the first dose of nitroglycerin were performed using ANOVA for paired samples.

RESULTS

A significant decrease in the PI and RI of the uterine (25.3 ± 4.9% and 21.2 ± 6.2%, respectively, P < 0.001) and umbilical (23.1 ± 6.9% and 19.7 ± 6.1%, respectively, P < 0.001) arteries was noted when comparing the first day without medication against the third day with the patch. No significant change in the PI and RI of the middle cerebral artery was observed. The mean arterial blood pressure decreased from 119.5 ± 4.5 mmHg to 114.8 ± 4.4 mmHg (P < 0.05).

CONCLUSION

The use of transdermal nitroglycerin in patients with severe pre-eclampsia is associated with a significant reduction in the RI and PI of the uterine and umbilical arteries, as well as of maternal blood pressure. Transdermal nitroglycerin does not affect the RI and PI of the fetal middle cerebral artery.

Stillbirths: Where? When? Why? How to make the data count?

Despite increasing attention and investment for maternal, neonatal, and child health, stillbirths remain invisible-not counted in the Millennium Development Goals, nor tracked by the UN, nor in the Global Burden of Disease metrics. At least 2·65 million stillbirths (uncertainty range 2·08 million to 3·79 million) were estimated worldwide in 2008 (≥1000 g birthweight or ≥28 weeks of gestation). 98% of stillbirths occur in low-income and middle-income countries, and numbers vary from 2·0 per 1000 total births in Finland to more than 40 per 1000 total births in Nigeria and Pakistan. Worldwide, 67% of stillbirths occur in rural families, 55% in rural sub-Saharan Africa and south Asia, where skilled birth attendance and caesarean sections are much lower than that for urban births. In total, an estimated 1·19 million (range 0·82 million to 1·97 million) intrapartum stillbirths occur yearly. Most intrapartum stillbirths are associated with obstetric emergencies, whereas antepartum stillbirths are associated with maternal infections and fetal growth restriction. National estimates of causes of stillbirths are scarce, and multiple (>35) classification systems impede international comparison. Immediate data improvements are feasible through household surveys and facility audit, and improvements in vital registration, including specific perinatal certificates and revised International Classification of Disease codes, are needed. A simple, programme-relevant stillbirth classification that can be used with verbal autopsy would provide a basis for comparable national estimates. A new focus on all deaths around the time of birth is crucial to inform programmatic investment.

Anaesthesiological considerations on tocolytic and uterotonic therapy in obstetrics

AIM

Significant side effects of tocolytic and uterotonic substances may be of concern to the anaesthesiologist. Recently, new drugs have been introduced having less side effects for both the mother and the neonate.

METHODS

A literature search was undertaken mainly focusing on meta-analyses, to review the possible side effects that might affect the course of anaesthesia and to suggest which precautions should be considered to prevent the occurrence of significant interactions with anaesthetic manipulations and drugs.

RESULTS

Magnesium sulphate has a proven benefit in lowering systolic blood pressure and preventing the occurrence of eclampsia, but not as a tocolytic. beta-adrenergic agonists are being abandoned due to the availability of tocolytic agents causing less side effects. Calcium channel blockers (CCB) are frequently used but can cause major maternal cardiovascular complications. Nitroglycerin seems to be appreciated as an acute tocolytic rather than a routine substance during pre-term labour. Cyclo-oxygenase-2 inhibitors are still under investigation but their tocolytic benefit is questionable mainly due to foetal side effects. Atosiban is considered the first-choice tocolytic. With respect to oxytocic drugs, oxytocine, prostaglandines and methylergometrine may all cause serious side effects especially when combined. The cardiovascular side effects of prostaglandins and methylergometrine can be life-threatening. Both oxytocin and carbetocin have a rather low risk for maternal complications.

CONCLUSION

Atosiban and CCB are at least as effective tocolytic agents as beta-mimetics but have significantly less side effects. Magnesium sulphate can cause neuromuscular blockade, especially when combined with CCB. Concerning oxytocic agents, short-acting oxyctocin and long-acting carbetocin have the least side effects as compared with prostaglandins and methylergometrine.

Effects of nitrovasodilators on the human fetal-placental circulation in vitro

This study examines the vasorelaxation of isolated human placental chorionic plate arteries and the perfused fetal-placental vasculature, in vitro, to a variety of nitrovasodilator compounds including glyceryl trinitrate (GTN) sodium nitroprusside (SNP), S-nitroso-N-acetylpenicillamine (SNAP), S-nitroso-N-glutathione (SNG) and NaNO(2). The effects of these compounds were also examined under conditions of high (>450 mmHg) and low oxygen (<50 mmHg) tension. In a separate series of experiments the effects of GTN and NaNO(2)were further investigated with addition of the antioxidants cysteine (100 microm), glutathione (100 microm) or superoxide dismutase (SOD) (30 I.U./ml). The order of nitrovasodilator potency, when added directly to isolated fetal vessels was GTN=SNP>SNAP=SNG>NaNO(2). The order under low oxygen tension was similar, GTN=SNP>SNG= SNAP>or=NaNO(2). SNG ( approximately fourfold) and NaNO(2)( approximately 50-fold) were significantly more potent under low oxygen conditions. Cysteine, glutathione and SOD were without effect on GTN induced vasodilatation. However, all three agents significantly enhanced (six- to ninefold) the effects of NaNO(2)under similar conditions. When infused directly into the fetal-placental circulation during in vitro perfusion experiments the order of potency was GTN>SNP>or=SNG>or=SNAP>or=NaNO(2). When the nitrovasodilators were infused indirectly via the maternal intervillous space the order of potency was GTN>or=SNP>or=NaNO(2)>or=SNAP=SNG. Our observations suggest that there are important differences in the action of different classes of nitrovasodilator compounds on the fetal-placental circulation. The changes observed with SNG and NaNO(2)may be influenced by levels of tissue oxygenation.