Prolonged relaxant effects of vecuronium in patients with deliberate hypermagnesemia: time for caution in cesarean section

We present two cases showing significantly prolonged action of vecuronium from magnesium treatment after general anesthesia for urgent cesarean section. The serum magnesium levels were maintained at a therapeutic range for severe eclampsia in one patient (5.6 mg.dl(-1)) and for tocolysis in another with placenta previa totalis (6.9 mg.dl(-1)). The obstetrics-specific emergency in each patient led us to proceed with general anesthesia but using reduced-dose vecuronium, which failed to prevent prolongation of the neuromuscular block. As a result, the patients received prolonged mechanical ventilation. Our cases underscore the need for anesthesiologists as well as obstetricians to be aware of the prolongation of the action of nondepolarizing muscle relaxants as a result of magnesium treatment.

Œdème pulmonaire aigu lors d’une menace d’accouchement prématuré : rôle de la tocolyse par la nicardipine

Beta adrenergic agonists are still used as first line treatment for preterm labor in many institutions, but their side effects lead to use alternative tocolytic drugs such as calcium channel blockers. We report three cases of pulmonary edema during preterm labor associated with the use of calcium channel blocker, intravenous nicardipine, widely used for tocolysis in France. In this article, potential mechanisms of this severe complication are briefly discussed: pregnancy-induced overload, deleterious hemodynamic effects of calcium channel blockers, concomitant administration of calcium channel blockers and/or beta-agonists and finally concomitant administration of physiological saline and/or glucocorticoids. Based on our experience, we recommend avoiding the association of calcium channel blockers and beta-agonists for preterm labor. Nicardipine, if used, should be administered at an adjusted dose with electric syringe to reduce volume infusion.

Spinal anesthesia-induced hypotension: a risk comparison between patients with severe preeclampsia and healthy women undergoing preterm cesarean delivery

We previously showed that, in comparison with term healthy parturients, patients with severe preeclampsia had a less frequent incidence of spinal hypotension, which was less severe and required less ephedrine. In the present study, we hypothesized that these findings were attributable to preeclampsia-associated factors rather than to a smaller uterine mass. The incidence and severity of hypotension were compared between severe preeclamptics (n = 65) and parturients with preterm pregnancies (n = 71), undergoing spinal anesthesia for cesarean delivery (0.5% bupivacaine, sufentanil, morphine). Hypotension was defined as the need for ephedrine (systolic blood pressure <100 mm Hg in parturients with preterm fetuses or 30% decrease in mean blood pressure in both groups). Apgar scores and umbilical arterial blood pH were also studied. Neonatal and placental weights were similar between the groups. Hypotension was less frequent in preeclamptic patients than in women with preterm pregnancies (24.6% versus 40.8%, respectively, P = 0.044). Although the magnitude of the decrease in systolic, diastolic, and mean arterial blood pressure was similar between groups, preeclamptic patients required less ephedrine than women in the preterm group to restore blood pressure to baseline levels (9.8 +/- 4.6 mg versus 15.8 +/- 6.2 mg, respectively, P = 0.031). The risk of hypotension in the preeclamptic group was almost 2 times less than that in the preterm group (relative risk = 0.603; 95% confidence interval, 0.362-1.003; P = 0.044). The impact of Apgar scores was minor, and umbilical arterial blood pH was not affected. We conclude that preeclampsia-associated factors, rather than a smaller uterine mass, account for the infrequent incidence of spinal hypotension in preeclamptic patients.

Intrapartum magnesium sulfate exposure attenuates neutrophil function in preterm neonates

BACKGROUND

Prenatal exposure to magnesium sulfate, a drug that is frequently used for attempted tocolysis in preterm labor, could alter neutrophil functional activity in infants born preterm.

OBJECTIVES

To determine the association between maternal tocolysis with magnesium sulfate and the cord blood neutrophil functional activity of preterm neonates.

METHODS

The chemotaxis, random motility, and chemiluminescence of neutrophils were compared in the cord blood of 10 preterm neonates born to mothers tocolysed with magnesium sulfate, 10 preterm infants whose mothers had not received any tocolysis, and 10 term infants. Data regarding the maternal and neonatal magnesium and calcium levels were collected and analyzed in association with the cord blood neutrophil functional activity of the preterm infants.

RESULTS

Neutrophil functional activity in the cord blood of the preterm neonates was significantly lower than in term neonates. However, the alteration of neutrophil chemotaxis, random motility and chemiluminescence was more noticeable in neonates with intrapartum exposure to magnesium sulfate as compared to preterm infants whose mothers received no tocolysis (30.9 +/- 2.3 vs. 36.7 +/- 2.7 microm, p < 0.01; 26.6 +/- 1.9 vs. 33.1 +/- 3.1 microm, p < 0.01; and 74.3 +/- 6.5 vs. 89.9 +/- 6.25 x 10(3) counts per min (cpm), p < 0.01, respectively). Furthermore, the reduction in neutrophil functional activity of preterm infants with intrapartum exposure to magnesium was directly correlated with the maternal serum magnesium levels (r = -0.90 to -0.85, p < 0.01).

CONCLUSION

In infants born preterm, intrapartum exposure to magnesium sulfate is a risk factor contributing to the alteration in neutrophil motility and post-phagocytic bactericidal capacity.

Self-limitation of intravenous tocolysis with beta2-adrenergic agonists is mediated through receptor G protein uncoupling

Tocolysis with a beta-adrenergic receptor agonist is the most common approach to premature labor management after the 25th wk of pregnancy. However, prolonged treatment is associated with a marked loss of efficacy. The biochemical mechanisms involved remain unclear. This study was undertaken to investigate the effect of fenoterol on beta-adrenergic receptor signal transduction in human myometrium. Myometrial biopsy specimens were obtained from 40 women at cesarean section between the 25th and 34th wk of pregnancy. Nineteen patients had received no tocolysis (controls, group I) and 21 had been treated with fenoterol (<48 h in 10, group II; > or = 48 h in 11, group III). As methods we used membrane preparation, adenylyl cyclase assay and cAMP RIA. Adenylyl cyclase activity was determined by the measurement of cAMP levels to evaluate signal transduction after stimulation of beta-adrenergic receptors with isoproterenol, G protein with GTP, and adenylyl cyclase with forskolin. The functional activity of GTP-binding regulatory proteins (G(s)) and adenylyl cyclase was not altered by fenoterol treatment. In the control group, the increase in adenylyl cyclase activity in response to GTP plus isoproterenol was greater than in response to GTP alone. The increase was reduced by 50% in group II and was insignificant in group III. There was no correlation between gestational age and basal adenylyl cyclase activity. Intravenous tocolysis with the beta2-adrenergic receptor agonist fenoterol leads to complete desensitization of the beta-adrenergic receptor system. In addition to the known reduction in receptor number (down-regulation) as underlying mechanism, uncoupling of the receptor from the stimulatory G protein G(s) was identified.

Pregnancy-Associated Cardiomyopathy

Background— Cardiomyopathy associated with pregnancy was first described more than half a century ago. However, because of its rare occurrence and geographical differences, the clinical profile of this condition has remained incompletely defined.

Methods and Results— Data obtained from 123 women with a history of cardiomyopathy diagnosed during pregnancy or the postpartum period were reviewed. One hundred women met traditional criteria of peripartum cardiomyopathy; 23 were diagnosed with pregnancy-associated cardiomyopathy earlier than the last gestational month. Peripartum cardiomyopathy patients had a mean age of 31±6 years and were mostly white (67%). Common associated conditions were gestational hypertension (43%), tocolytic therapy (19%), and twin pregnancy (13%). Left ventricular ejection fraction at the time of diagnosis was 29±11% and improved to 46±14% ( P ≤0.0001) at follow-up. Normalization of left ventricular ejection fraction occurred in 54% and was more likely in patients with left ventricular ejection fraction >30% at diagnosis. Maternal mortality was 9%. A comparison between the peripartum cardiomyopathy and early pregnancy-associated cardiomyopathy groups revealed no differences in age, race, associated conditions, left ventricular ejection fraction at diagnosis, its rate and time of recovery, and maternal outcome.

Conclusions— This study helps to define the clinical profile of patients with pregnancy-associated cardiomyopathy diagnosed in the United States. Clinical presentation and outcome of patients with pregnancy-associated cardiomyopathy diagnosed early in pregnancy are similar to those of patients with traditional peripartum cardiomyopathy. These 2 conditions may represent a continuum of a spectrum of the same disease.

Evaluación farmacoeconómica de dos protocolos de tocolisis para la inhibición del parto prematuro

OBJECTIVE

Pharmacoeconomic assessment of two tocolysis protocols alternatively using atosiban or ritodrine as first-choice tocolytic agent able to delay birth for 48 hours in the acute management of premature birth risk in gravid women.

METHODS

The modeling technique used for the selection of the most efficient protocol was the decision analysis. A search for controlled clinical trials comparing the effectiveness and/or safety of atosiban versus ritodrine was performed in Medline and the Cochrane Library. Only differential costs were considered for cost analysis.

RESULTS

Cost-effectiveness obtained with the protocol including ritodrine as first-choice drug was Euros 194/effectiveness unit, and Euros 632/effectiveness unit when atosiban is used. The sensitivity analysis shows sensitivity only for an incidence of acute lung edema greater than 8% or a cost of at least Euros 50,000.

CONCLUSION

A tocolysis protocol using ritodrine as first-choice agent and atosiban as rescue drug is the most efficient option based on available evidence. In pregnant women where the likelihood of developing acute pulmonary edema is high, or when therapy cost is high, atosiban may be an appropriate alternative option.

Uterine contractions might increase heart preload in the recipient fetus in early-onset twin-twin transfusion syndrome: an ultrasound assessment

OBJECTIVES

Uterine contractions (UC) in twin pregnancy are often experienced, yet the effects of UC in twin-twin transfusion syndrome (TTTS) remain to be clarified. The recipient heart preload condition and the effects of UC were evaluated and the final objective was to clarify the effects of tocolysis.

METHODS

Firstly, the preload indexes (PLIs) and cardiothoracic area ratios (CTARs) were analyzed on both fetuses of 10 TTTS cases, aged from 14 to 28 gestational weeks in stage III/IV cases for evaluating the preload condition. Then, the PLIs in the presence and absence of UC in the recipient fetuses were determined to evaluate the difference.

RESULTS

The PLIs of the recipient and the donor fetuses were 0.78 +/- 0.34 (n = 163) and 0.35 +/- 0.13 (n = 71) respectively. The CTARs were 30.2 +/- 6.1 (n = 62) and 23.4 +/- 5.4 (n = 62) respectively. The PLIs in the absence and presence of UC in the recipient fetuses were 0.69 +/- 0.29 and 0.99 +/- 0.38 (n = 35). All above comparisons showed highly significant differences (p < 0.0001).

CONCLUSION

The recipient fetuses have signs of cardiac dilatation and a high-preload condition. UC transiently further raises high-preload conditions of the recipient fetus. Thus, tocolysis may be necessary for management in cases of early-onset severe TTTS.

New Data on the Importance of Gestational Mg Deficiency

Chronic primary Mg deficiency is frequent. About 20% of the population consumes less than two-thirds of the RDA for Mg. Women, particularly, have low intakes. For example, in France, 23% of women and 18% of men have inadequate intakes. Mg deficiency during pregnancy can induce maternal, fetal, and pediatric consequences that might last throughout life. Studies of gestational Mg deficiency in animals show that Mg deficiency may have marked effects on parturition and postuterine involution. It has interfered with fetal growth and development, and caused morbidity from hematological effects and disturbances in temperature regulation, to teratogenic effects. Emphasis, here, is on effects of chronic clinical gestational Mg deficiency as it affects the infant. Premature labor, contributed to by uterine hyperexcitability caused by chronic maternal Mg deficiency, that can be intensified by stress, gives rise to preterm birth. If the only cause of uterine overactivity is Mg deficiency, its supplementation constitutes nontoxic tocolytic treatment, as an adjuvant treatment, that is devoid of toxicity and enhances efficacy and safety of tocolytic drugs such as beta-2 mimetics. Evidence is considered that Mg deficiency or Mg depletion can contribute to the Sudden Infant Death Syndrome (SIDS). SIDS may be a fetal consequence of maternal Mg deficiency through impaired control of Brown Adipose Tissue (BAT) thermoregulation mechanisms leading to a modified temperature set point. SIDS can result from dysthermias: hypo- or hyperthermic forms. Possibly, simple nutritional Mg supplements might be preventive. Various stresses in an infant can transform simple Mg deficiency into Mg depletion. For example, lying prone can be stressful for the baby, as can parental smoking. The role of chronopathological stress appears to be often neglected, as it constitutes a clinical form of primary hypofunction of the biological clock [with its anatomical and clinical stigma such as reduced production of melatonin (MT) and of its urinary metabolite: 6 Sulfatoxy-Melatonin (6 SMT)]. SIDS might be linked to impaired maturation of both the photoneuroendocrine system and BAT. Prophylaxis of this form of SIDS should include atoxic nutritional Mg therapy for pregnant women with total light deprivation at night for the infant. Consequences of maternal primary Mg deficiency have been inadequately studied. To determine ultimate outcomes of gestational Mg deficiency in infants, a long-term multicenter placebo-controlled prospective study should undertaken on effects of maternal nutritional Mg supplementation on lethality/morbidity in fetus, neonates, infants, children and adults, not only during pregnancy and the baby's first year, but throughout life.

Tocolysis in term breech external cephalic version

OBJECTIVES

To study the effect of ritodrine tocolysis on the success of external cephalic version (ECV) and to assess the role of ECV in breech presentation at our centre.

MATERIAL AND METHODS

A prospective randomized double-blind-controlled trial comparing ritodrine and placebo in ECV of singleton term breech pregnancy at a tertiary hospital.

RESULTS

Among the 60 patients who were recruited, there was a success rate of 36.7%. Ritodrine tocolysis significantly improved the success rate of ECV (50% vs. 23%; P=0.032). There was a marked effect of ritodrine tocolysis on the ECV success in nulliparae (36.4% vs. 13.0%) and multiparae (87.5% vs. 57.1%). External cephalic version has shown to reduce the rate of cesarean section for breech presentation by 33.5% in our unit.

CONCLUSION

External cephalic version significantly reduced the rate of cesarean section in breech presentation, and ritodrine tocolysis improved the success of ECV and should be offered to both nulliparous and parous women in the case of term breech presentation.

Repeat Measurement of Cervical Length After Successful Tocolysis

OBJECTIVE

To measure the ultrasonographic cervical length in undelivered women after successful tocolysis for preterm labor, and to determine whether this could improve the predictive value of cervical length measured before initiation of tocolysis on the risk of preterm delivery.

METHODS

This was a prospective study of patients admitted and treated for uterine contractions at 24(+0) to 33(+6) weeks of gestation with a cervical length of 26 mm or less by transvaginal ultrasonography on admission. Intravenous tocolysis was stopped when delivery was delayed by 48 hours, and cervical length was remeasured before discharge. The primary outcome was preterm delivery, defined by a delivery before 37 weeks. Predictive analysis was based on logistic models, with estimated odds ratios and 95% confidence interval.

RESULTS

One hundred and nine patients were included in the study. The median (first, third quartile) cervical length on admission was 18 (13, 22) mm. The median (first, third quartile) variation in cervical length after tocolysis was stopped was 3 (0, 8) mm, and ranged from -13 to 26 mm. The median (first, third quartile) time interval from tocolysis to delivery was 53.0 (35.0, 70.0) days, with 45 (41.3%) patients delivered before 37 weeks. After adjustment for cervical length before admission and parity and gestational age on admission, the assessment of the variation in cervical length after successful tocolysis did not improve the predictive value of transvaginal sonography for the risk of preterm delivery (odds ratio 0.97; 95% confidence interval 0.90-1.03; P = .27).

CONCLUSION

To repeat ultrasonographic cervical length measurement after successful tocolysis for preterm labor is useless.

An EP4 receptor agonist prevents indomethacin-induced closure of rat ductus arteriosus in vivo

Indomethacin exerts a strong tocolytic effect by suppressing uterine contractions mediated by prostaglandins. However, indomethacin also induces in utero closure of fetal ductus arteriosus (DA), leading to serious neonatal consequences. Using rats, we tested the effect of an agonist for a subtype of prostaglandin E2 receptor (EP4), ONO-AE1-437 and its prodrug ONO-4819, as a DA dilator during indomethacin treatment. In vitro, ONO-AE1-437 exhibited a potent dilatory effect on DA against O(2)- and indomethacin-induced contractions in a concentration-dependent manner. In vivo, rat dams were given indomethacin (10 mg/kg, p.o.) alone or with ONO-4819 (0.3 micrograms/kg/h, s.c.) on d 21 of gestation and pups were delivered 4 h later through cesarean section to evaluate the ratio of diameter of DA to that of pulmonary artery. Pups from dams with no drug had DA/PA ratio of 0.9 +/- 0.05, whereas those from dams with indomethacin alone had a decreased ratio of 0.2 +/- 0.03. When ONO-4819 was co-administered to the dams, the ratio recovered significantly to 0.7 +/- 0.06. The administration of ONO-4819 to the dams did not induce any increase in the uterine activity. These results suggest that administration of an EP4 agonist in addition to indomethacin might prevent adverse reactions of indomethacin on fetal DA without restricting its tocolytic effects.

Defining standards of care in maternal-fetal medicine

OBJECTIVE

The purpose of this study was to describe current practice patterns for 7 controversial topics in Maternal-Fetal Medicine.

STUDY DESIGN

An interactive survey of obstetric treatment was performed as part of a postgraduate course at the 2004 Annual Meeting of the Society for Maternal-Fetal Medicine. Seven controversial topics were addressed, which included tocolytic therapy, progesterone supplementation for the prevention of preterm birth, screening for inherited thrombophilia, cervical cerclage for a shortened cervix, treatment of preterm premature rupture of membranes, magnesium sulfate seizure prophylaxis, and dexamethasone therapy for HELLP (hemolysis, elevated liver enzymes, and low platelet count) syndrome.

RESULTS

A total of 298 obstetric care providers attended the postgraduate course. By report, most attendees were maternal-fetal medicine specialists (60.7% of respondents) who were >10 years out from specialty training (56.3% of respondents) and who were practicing in a university-based setting (52.9% of respondents). An average of 233 practitioners (range, 157-298 practitioners) answered each question. An analysis of the responses allowed for the determination of current practice patterns in the 7 controversial areas addressed.

CONCLUSION

Contemporary practice patterns for 7 controversial topics in obstetric medicine are described. Such surveys may be useful in defining standards of care in maternal-fetal medicine.

Contemporary management of preterm premature rupture of membranes (PPROM): a survey of maternal-fetal medicine providers

OBJECTIVE

This study was undertaken to characterize variations in the management for women with preterm premature rupture of membranes (PPROM) among maternal-fetal medicine (MFM) specialists in the context of current recommendations for clinical practice and evidenced-based practice.

STUDY DESIGN

We performed a Web-based survey of 1375 MFM providers. Participants were queried on practice characteristics and management issues including use of tocolytics, antibiotics, steroids, and timing of delivery.

RESULTS

A total of 508 providers (37%), representing all 50 states and 13 countries, responded to the survey. Only 30% reported a formal departmental protocol for managing women with PPROM. Consistent use of steroids (99.4%) and antibiotics (99.6%) were reported. Administration of steroids was confined to < or =32 weeks by 37%, and < or =34 weeks by 51% of practitioners. Repeated dosing of steroids was uncommon (16%). The antibiotics use and rationale for use varied among respondents. Tocolytics were used by 73% of respondents with magnesium sulfate the main agent used (98%). Use of tocolytics was generally used for 48 hours or less to attain steroid benefit (88%). Amniocentesis was used by 66% of practitioners in the acute evaluation of PPROM. Fetal lung maturity testing was reported by 78% with variability noted with respect to the test used. Outpatient management of women with PPROM after viability was noted by 43% of respondents. Gestational age at which expectant management is abandoned in women with PPROM varied significantly between respondents: > or =34 weeks by 56%, > pr =35 weeks by 26%, > or =36 weeks by 12%, and > or =37 weeks by 4.0%.

CONCLUSION

Although many management practices for women with PPROM are consistent with currently available evidence and practice recommendations, substantial variations still exist among MFM providers.

The influence of antibiotic treatment on tocolysis in threatened advanced pregnancy

OBJECTIVE

The aim of this study was to determine: a) to what extent application of antibiotics enhances efficiency of tocolysis; b) whether the duration of antibiotic treatment influences its efficacy; c) what criterion is decisive for efficacy of tocolysis assisted by antibiotic therapy.

MATERIALS AND METHODS

223 successive women with unifetal pregnancies, aged 17 to 42 (average age 27.3), admitted to the Department of Gynecology and Obstetrics of the JU Medical College in the period from January 1, 1999 to September 9, 2001, were enrolled in the study. Using clinical methods such as: assessment of contractile activity of the uterus, of uterine cervix and membranes, presence of bleeding and other clinical symptoms, these women were diagnosed with imminent preterm labour.

CONCLUSIONS

Antibiotic treatment enhances the efficacy of tocolysis, influencing the time of prolonging pregnancy in imminent preterm delivery. This synergistic effect is clinically crucial as in this way significantly larger number of children will be born at term and also a number of premature neonates who survive may be increased.

Maternal cardiac arrest associated with attempted fetal injection of potassium chloride

We report a case of maternal cardiac arrest immediately after attempted fetal cardiac injection of potassium chloride. Prompt institution of maternal cardiac life-support protocols resulted in successful maternal resuscitation. The management of this case as well as that of fetal cardiac injections of potassium chloride is reviewed.

Chorioamnionitis risk and neonatal outcome in preterm premature rupture of membranes

OBJECTIVE

The objective of this study was to compare the neonatal outcome in patients with preterm premature rupture of membranes with and without clinical chorioamnionitis.

STUDY DESIGN

This is a retrospective study that included 254 pregnant women with preterm rupture of membranes. The study group was divided according to the presence or absence of clinical chorioamnionitis defined as the presence of two or more of the following criteria: maternal temperature >38 degrees C on two or more occasions > or =1 h apart, maternal tachycardia (> or =120 beats/min), uterine tenderness, foul smelling amniotic fluid, maternal leukocytosis > or =20,000 mm(-3) with bands and positive C reactive protein. Also the study population was divided according to the use of tocolysis. Exclusion criteria included multiple pregnancy, fetal congenital anomalies, diabetes mellitus and severe preeclampsia. Amniotic fluid was collected from the cervix or from the transabdominal amniocentesis. Antibiotics and tocolysis were used according to the hospital protocols. Parametric and nonparametric statistics were used for comparisons.

RESULTS

There were no significant differences in birth weight, Apgar scores at 1 and 5 min, rates of respiratory distress syndrome, intraventricular hemorrhage and necrotizing enterocolitis between patients with and without clinical chorioamnionitis or between women who received tocolysis and the ones that did not receive tocolysis. In cases of clinical chorioamnionitis and when tocolysis was used the neonates stayed longer in the neonatal intensive care unit (NICU).

CONCLUSION

Patients with preterm premature rupture of membranes and clinical chorioamnionitis have similar neonatal outcomes than the ones without clinical chorioamnionitis.

New data on the importance of gestational Mg deficiency

Chronic primary Mg deficiency is frequent. Around 20% of the population consumes less than two-thirds of the RDA for Mg, in both genders and in women particularly: for example, in France, 23% of women and 18% of men. Primary Mg deficiency may occur in fertile women. Gestational Mg deficiency is able to induce maternal, fetal, and pediatric consequences which might last throughout life. Experimental studies of gestational Mg deficiency show that Mg deficiency during pregnancy may have marked effects on the processes of parturition and of postuterine involution. It may interfere with fetal growth and development from teratogenic effects to morbidity: i.e. hematological effects and disturbances in temperature regulation. Clinical studies on the consequences of maternal primary Mg deficiency in women have been insufficiently investigated. To check the validity of the role of this frequent gestational Mg deficiency, the protocol of a long term multicentric placebo controlled prospective study on the effects of maternal nutritional Mg supplementation on lethality and morbidity in fetus, neonates, infants, children and adults should be carried out not only during pregnancy and the first year of life, but throughout life. Two clinical forms of chronic gestational Mg deficiency in women have been stressed: Premature labor when chronic maternal Mg deficiency is involved in uterine hyperexcitability, Sudden Infant Death Syndrome (SIDS) when it is caused by either simple Mg deficiency or various forms of Mg depletion. Nutritional Mg treatment of premature labor. If gestational Mg deficiency is the only cause for uterine overactivity, nutritional Mg supplementation constitutes the etiopathogenic atoxic tocolytic treatment. But although it is an adjuvant factor in premature labor, it is only a useful accessory treatment, devoid of toxicity but which increases the effectiveness and safety of the associated tocolytic drugs such as beta-2 mimetics. SIDS due to gestational Mg deficit: Mg deficiency or various forms of Mg depletion. SIDS may be caused by the fetal consequences of maternal Mg deficiency through an impaired control of Brown Adipose Tissue (BAT) thermoregulation, mechanisms leading to a modified temperature set point. SIDS may result from dysthermias: hypo- or hyperthermic forms. A possible prevention could rest on simple maternal nutritional Mg supplementation. Various stresses in pregnant women or in the infant may transform a simple Mg deficiency into Mg depletion: stress in baby care such as bedding in prone position, environmental factors such as parental smoking, but the role of chronopathological stress particularly appears to be too often neglected as it constitutes a clinical form of primary hypofunction of the biological clock [with its anatomical and clinical stigma such as reduced production of melatonin (MT) and of its urinary metabolite: 6 Sulfatoxy-Melatonin (6 SMT)]. SIDS might be linked to an impaired maturation of both the photoneuroendocrine system and BAT. A preventive treatment of this form of SIDS should associate atoxic nutritional Mg therapy for pregnant women with total light deprivation at night for the infant. The place of Mg therapy for the infant and of MT, L Tryptophan and taurine is uncertain for the moment.

[Ex utero intrapartum technique]

Upper airway obstruction of a neonate constitutes an emergency. The ex utero intrapartum technique (EXIT) is a procedure for safely managing airway obstruction at birth, in which placental support is maintained until the airway is evaluated and secured. The anaesthetist is involved in preventing uterine contractions that impair oxygenation of the foetus and cause placental separation, in providing foetal anaesthesia to help airway manipulations, in maintaining foetal pattern of circulation, in preventing and treating maternal hypotension and in resuscitating the neonate. General anaesthesia with high concentration of inhalational agents is preferred as it provides surgical tocolysis and foetal anaesthesia. Additional uterine relaxation may be obtained using tocolytic drugs like nitroglycerin or beta-adrenergic agonists. During EXIT the foetus is delivered only as far as the shoulders or thorax leaving the cord entirely in utero to maximize the duration of placental support and to minimize heat and water loss. In this position foetal airway is examined and secured, which may involve tracheal intubation, bronchoscopy or tracheostomy. The umbilical cord is divided and the neonate is completely delivered only after the airway has been secured. With EXIT, a potential life-threatening emergency at birth can be managed like an elective procedure that can improve the prognosis for foetuses with airway obstruction.

Tocolyse dans les situations pathologiques particulières

In twin pregnancies, the use of beta-adrenergics is associated with a significantly higher incidence of cardiovascular complications, and calcium channel blockers as well as oxytocin antagonists currently appear as first line agents. After extreme preterm delivery of the first twin and in selected patients, the birth of second twin may be delayed with a mean gain of 10-50 days. In cases of symptomatic placenta previa with mild-to-moderate bleeding, tocolytic agents may be associated with a prolongation of pregnancy and increased birth weight without significant impact on frequency or severity of bleeding. Calcium channel blockers are the drugs of choice in the event of diabetes. Indomethacin is a potent tocolytic, in particular in patients with polyhydramnios. However, it may cause oligohydramnios, premature closure of the ductus arteriosus and intrauterine fetal death when high doses are administered for a duration exceeding 48 to 72 hours, particularly beyond 32 weeks' gestation. The neonatal complications of indomethacin occur frequently. Tocolysis appears to reduce the failure rate of external cephalic version at term.

Prostaglandin endoperoxide H synthase inhibitors and other tocolytics in preterm labour

Preterm delivery (<37 weeks of gestation) is the major obstetrical complication in developed countries, yet attempts to delay labour and prolong pregnancy have largely been unsuccessful. One of the many reasons it is so difficult to prevent preterm birth is that the nature of preterm labour changes as a function of gestational age, maternal lifestyle factors or infection, to list a few of the reasons. The inhibitors of prostaglandin endoperoxide H synthase (PGHS), known as the Non-steroidal Antiinflammatory Drugs, have been viewed with interest as tocolytics with promising effectiveness under most conditions of preterm labour. Three isoforms of PGHS exist; the first two, PGHS-1 and -2, have been studied for their catalytic activity, X-ray crystallographic structure, and physiological roles in the adult and the foetus. Mixed inhibitors and isoform-specific inhibitors of PGHS have been developed, and their roles in delaying preterm labour are examined and compared to other tocolytics.

Pharmacological knockout of endothelin ET(A) receptors

We employed newly developed antagonists, which are specific for endothelin ET(A) receptors, to test whether this drug could mimic the phenotype of the mouse with corresponding gene knock out. Newborn rats, whose dams were given the ET(A) antagonist from day 7 of gestation, exhibited the typical ET(A)-lacking phenotypes like craniofacial abnormalities and major vessel anomalies. Interestingly, craniofacial abnormality was seen in the pups that were exposed to the drug in the mid-gestational period, while another phenotype, patent ductus arteriosus (DA), was seen in the pups that were exposed to the drug in the late gestation. We have focused on the function of the ET system in DA closure after birth because the animals with a genetic defect of ET(A) would die of suffocation shortly after birth. Rat pups were delivered by Caesarean section and were given the antagonist intraperitoneally. The antagonists caused an inhibition of DA closure in vivo at 3 h after birth when DA closure was completed in the control pups. Next, we tested the potential utilities of the ET(A) specific antagonists in tocolysis with NSAIDs which sometimes leads to a closure of fetal DA in utero. Indomethacin administration to rat dams resulted in the constriction of DA in utero which was cancelled by the co-administration of the antagonists. These results suggested that ET(A) plays a physiological role in the postnatal closure of the rat DA in vivo and that ET(A) specific antagonists may be able to leave fetal DA intact during tocolysis with NSAIDs.

Does terbutaline damage the developing heart?

BACKGROUND

Beta(2)-Adrenoceptor (betaAR) agonists, such as terbutaline, are widely used to arrest preterm labor. They also cross the placenta where they stimulate receptors in fetal tissues, which in turn use betaAR input for trophic control of cell replication and differentiation.

METHODS

As rats are altricial, we administered terbutaline in two different postnatal exposure periods (10 mg/kg given daily on Days 2-5 or 11-14).

RESULTS

Hearts were examined twenty-four hours after the last dose and on postnatal day 30 for cardiac damage. Neither treatment paradigm caused an increase in cardiac abnormalities compared to controls but quantitative analysis of the number of nuclei indicated reductions in females.

CONCLUSIONS

These findings do not support earlier case reports of outright myocardial necrosis after terbutaline tocolysis in human infants. Nevertheless, the significant statistical association between terbutaline and cardiac anomalies in epidemiological studies suggest that terbutaline may sensitize the developing heart to other insults that affect development.

[Enzymatic diagnosis of neurological risk of premature labor]

The level of oxytocinase in the pregnant woman's blood is a sensitive marker of the efficiency of the hypothalamus/hypophisis/suprarenal glands in mother and fetus, as well as the quantity of hormone production, also in placenta, which determines the duration of pregnancy and the course of labor. In the study, the level of oxytocinase was measured before the labour in 485 pregnant women at risk of premature labour. After the mean duration of pregnancy of 264 +/- 12 days, 353 infants were born fully mature (group I), and 132 with the lowered maturity of 6-9 Klimek points (group II). In group II, the mean pregnancy duration (249 days), body mass (2700 g) and oxytocinase level (5.6 mumol/l/min) were significantly lower and tocolysis was necessary twice as often (41% vs. 21%). Independently of the level of newborn maturity in cases of tocolysis the mean level of oxytocinase was significantly 2.6 times lower (3 +/- 0.8 mumol/l/min) than in the other pregnant women (7.9 mumol/l/min). It proves, that low oxytocinasaemia becomes normal following the ACTH-depot therapy, which eliminates the necessity of tocolysis.