Circumstances influencing umbilical-cord plasma catecholamines at delivery

Preeclampsia and future cardiovascular risk: A point of view from the clearance of plasma vasoactive amines

OBJECTIVE

To summarize the reported evidence on the relationship between vasoactive amines and preeclampsia.

METHODS

A literature search was conducted in MEDLINE/PubMed and EMBASE.

RESULTS

The summarized results are as follows: (1) Menstruation can effectively eliminate vasoactive amines norepinephrine, serotonin and histamine. (2) Pregnancy increases norepinephrine production due to fetal brain development and decreases vasoactive-amine elimination due to amenorrhea. (3) Preeclampsia is associated with a low renal and/or sweating capacity, or in rare cases, with increased norepinephrine production due to maternal pheochromocytoma and fetal neuroblastoma.

CONCLUSION

Preeclampsia is mainly due to decreased excretion of norepinephrine and other vasoactive amines.

Randomized Double-blinded Comparison of Norepinephrine and Phenylephrine for Maintenance of Blood Pressure during Spinal Anesthesia for Cesarean Delivery

Background:

During spinal anesthesia for cesarean delivery, phenylephrine can cause reflexive decreases in maternal heart rate and cardiac output. Norepinephrine has weak β-adrenergic receptor agonist activity in addition to potent α-adrenergic receptor activity and therefore may be suitable for maintaining blood pressure with less negative effects on heart rate and cardiac output compared with phenylephrine.

Methods:

In a randomized, double-blinded study, 104 healthy patients having cesarean delivery under spinal anesthesia were randomized to have systolic blood pressure maintained with a computer-controlled infusion of norepinephrine 5 μg/ml or phenylephrine 100 μg/ml. The primary outcome compared was cardiac output. Blood pressure heart rate and neonatal outcome were also compared.

Results:

Normalized cardiac output 5 min after induction was greater in the norepinephrine group versus the phenylephrine group (median 102.7% [interquartile range, 94.3 to 116.7%] versus 93.8% [85.0 to 103.1%], P = 0.004, median difference 9.8%, 95% CI of difference between medians 2.8 to 16.1%). From induction until uterine incision, for norepinephrine versus phenylephrine, systolic blood pressure and stroke volume were similar, heart rate and cardiac output were greater, systemic vascular resistance was lower, and the incidence of bradycardia was smaller. Neonatal outcome was similar between groups.

Conclusions:

When given by computer-controlled infusion during spinal anesthesia for cesarean delivery, norepinephrine was effective for maintaining blood pressure and was associated with greater heart rate and cardiac output compared with phenylephrine. Further work would be of interest to confirm the safety and efficacy of norepinephrine as a vasopressor in obstetric patients.

The health implications of birth by Caesarean section

Since the first mention of fetal programming of adult health and disease, a plethora of programming events in early life has been suggested. These have included intrauterine and postnatal events, but limited attention has been given to the potential contribution of the birth process to normal physiology and long-term health. Over the last 30 years a growing number of studies have demonstrated that babies born at term by vaginal delivery (VD) have significantly different physiology at birth to those born by Caesarean section (CS), particularly when there has been no exposure to labour, i.e. pre-labour CS (PLCS). This literature is reviewed here and the processes involved in VD that might programme post-natal development are discussed. Some of the effects of CS are short term, but longer term problems are also apparent. We suggest that VD initiates important physiological trajectories and the absence of this stimulus in CS has implications for adult health. There are a number of factors that might plausibly contribute to this programming, one of which is the hormonal surge or "stress response" of VD. Given the increasing incidence of elective PLCS, an understanding of the effects of VD on normal development is crucial.

Neonatal morbidity and mortality after elective cesarean delivery

This article explores the effects of elective cesarean delivery (ECD) at term on neonatal morbidity and mortality. Available data have limitations, and do not provide conclusive evidence regarding the safety of planned ECD versus planned vaginal delivery. Some data suggest an association between ECD and increased neonatal respiratory morbidity and lacerations, and possibly decreased central and peripheral nervous system injury. Potentially increased risks of neonatal mortality with ECD at term may be counterbalanced by risks for fetal demise in ongoing pregnancies. Patients and physicians considering ECD should review competing risks and benefits; further research is needed to inform these discussions.

Neonatal mortality and morbidity after elective cesarean delivery versus routine expectant management: a decision analysis

A number of competing risks and benefits influence the rates of neonatal morbidity and mortality in elective cesarean delivery versus expectant management. To compare these rates, we developed complex decision trees to model the expected outcomes among hypothetical cohorts of 1,000,000 uncomplicated pregnancies undergoing elective cesarean delivery versus 1,000,000 comparable pregnancies undergoing routine pregnancy management. A separate tree was created for each complication, including neonatal death, respiratory morbidity, intracranial hemorrhage, and brachial plexus injury. We found that neonatal mortality was increased among elective cesarean deliveries, but perinatal mortality was higher with routine expectant management due to fetal deaths. Respiratory morbidity was substantially more common among infants delivered by elective cesarean delivery, whereas intracranial hemorrhage and brachial plexus injury were less common. We conclude that the fetal/neonatal impact of elective cesarean is mixed, but any improvement in perinatal health is likely to be small.

Does regular massage from late pregnancy to birth decrease maternal pain perception during labour and birth?—A feasibility study to investigate a programme of massage, controlled breathing and visualization, from 36 weeks of pregnancy until birth

The present study was undertaken to produce a detailed specification of a programme of massage, controlled breathing and visualization performed regularly by birth partners, from 36 weeks gestation and assisted by a trained professional, following hospital admission during labour and birth. As current research on massage interventions for pain relief in labour is poorly characterized, we began by undertaking a feasibility study on an established massage programme [Goldstone LA. Massage as an orthodox medical treatment past and future. Complementary Therapies in Nursing & Midwifery. 2000;6:169-75]. The intervention was designed in light of experimental findings that repeated massage sessions over 14 days increases pain threshold, by an interaction between oxytocin and opioid neurons [Lund I, Yu L-C, Uvnas-Moberg K, Wang J, Yu C, Kurosawa M, et al. Repeated massage-like stimulation induces long-term effects on nociception: contribution of oxytocinergic mechanisms. European Journal of Neuroscience 2002;16:330-8]. A 4 week time-frame was selected to coincide with a physiological increase in maternal pain threshold [Cogan R, Spinnato JA. Pain and Discomfort Thresholds in Late Pregnancy. Pain 1986;27:63-8, Whipple B, Josimovich JB, Komisaruk BR. Sensory thresholds during the antepartum, intrapartum, and postpartum periods. International Journal of Nursing Studies 1990;27(3):213-21, Gintzler AR, Komisaruk BR. Analgesia is produced by uterocervical mechano-stimulation in rats: roles of afferent nerves and implications for analgesia of pregnancy and parturition. Brain Research 1991;566:299-302, Gintzler AR, Liu N-J. The maternal spinal cord: biochemical and physiological correlates of steroid-activated antinociceptive processes. In: Russell JA, Douglas AJ, Windle RJ, Ingram CD, editors., Progress in Brain Research. Volume 133. The Maternal Brain. Neurobiological and Neuroendocrine adaptation and disorders in pregnancy and postpartum. Amsterdam: Elsevier Science, 2001. p. 83-97]. The main objective was to measure the effects of the programme on maternal pain perception during labour and birth. To detect any effect of massage during labour, on maternal cortisol and catecholamines, cord venous blood was taken to measure plasma concentrations following birth. Twenty-five nulliparous (N) and 10 multiparous (M) women participated in the study. Cortisol values were similar to published studies following labour without massage but pain scores on a Visual Analogue Scale (VAS), at 90min following birth were significantly lower than scores recorded 2 days postpartum [Capogna G, Alahuhta S, Celleno D, De Vlieger H, Moreira J, Morgan B, et al. Maternal expectations and experiences of labour pain and analgesia: a multi-centre study of nulliparous women. International Journal of Obstetric Anaesthesia 1996;5:229-35]. The mean score was 6.6. Previous studies suggest that a reduction from 8.5 to 7.5 would significantly reduce pharmacological analgesia in labour [Capogna G, Alahuhta S, Celleno D, De Vlieger H, Moreira J, Morgan B, et al. Maternal expectations and experiences of labour pain and analgesia: a multi-centre study of nulliparous women. International Journal of Obstetric Anaesthesia 1996;5:229-35].

Neonatal respiratory morbidity following elective caesarean section in term infants. A 5-year retrospective study and a review of the literature

Respiratory morbidity is an important complication of elective caesarean section. The presence of labour preceding caesarean section reduces the risk of neonatal respiratory morbidity. Recently, it has been shown that the incidence of respiratory morbidity is lower in infants with a gestational age of at least 39(+0) weeks at elective caesarean section compared to infants with a gestational age less than 39(+0) weeks.This article describes the results of a 5-year retrospective study on the incidence of respiratory distress in term neonates delivered by elective caesarean section in relation to gestational age and provides a literature review on neonatal respiratory morbidity following elective caesarean section.

Alfentanil given immediately before the induction of anesthesia for elective cesarean delivery

Opioids are routinely omitted at the induction of general anesthesia for cesarean delivery because of concerns about neonatal respiratory depression. The subsequent unmodified maternal stress response to tracheal intubation reduces placental perfusion. The short-acting opioid alfentanil may afford advantages at the induction, without subsequent neonatal depression. In this double-blinded study of elective cesarean deliveries, 40 patients were allocated randomly to receive either alfentanil 10 microg/kg (n = 18) or placebo (n = 22), 1 min before the induction of anesthesia with thiopental 4 mg/kg and succinylcholine 1.5 mg/kg. Anesthesia was maintained with 50% nitrous oxide, 0.5% isoflurane in oxygen, and atracurium. Neonates were assessed by using Apgar scores, Neurologic and Adaptive Capacity Scores, and umbilical cord blood gas and catecholamine analysis. After intubation, mothers receiving alfentanil had a smaller increase in mean arterial blood pressure, (11 +/- 15 vs 31 +/- 13 mm Hg, P < 0.001) and lower plasma norepinephrine concentrations, (336 +/- 152 vs 486 +/- 241 pg/mL, P < 0.05). Neonates in the alfentanil group had greater umbilical arterial oxygen tensions (27.8 +/- 7.0 vs 22.6 +/- 7.4 mm Hg), slightly reduced Apgar scores (both P < 0.05), but similar Neurologic and Adaptive Capacity Scores. One neonate in the alfentanil group required naloxone. The maternal stress response was attenuated in the alfentanil group but at the cost of early neonatal depression. However, all neonates should be monitored for possible immediate, but transient, respiratory depression.

Mode of delivery and childhood blood pressure

A number of studies have shown that children born by cesarean section have lower blood pressure during the neonatal period. The aim of this study was to investigate whether mode of delivery influenced childhood blood pressure: at age 7.5 to 8 y in a cohort of 756 children born preterm, at 7 to 9 y in a pilot study of 166 children born at term in the United Kingdom, and in a cohort of 650 Tasmanian children born at term. In the preterm cohort, systolic blood pressure was significantly lower in children born by cesarean section rather than delivered vaginally (99.3+/-10.0 versus 101.4+/-9.4 mm Hg; 95% confidence interval, -0.69 to -3.46; p = 0.003), with a significant trend to having a higher pressure in those born by breech versus forceps versus spontaneous vaginal delivery versus cesarean section. These findings were not replicated in the term cohorts. This raises the hypothesis that there is a sensitive period for programming later blood pressure by factors associated with mode of delivery and that this period does not extend to full-term.

Intrapartum fetal hypoxia and biochemical markers: a review

Intrapartum fetal hypoxia is a rare event, although fetal intrapartum surveillance is discussed as a subject of major importance. This is mainly because of consequences of fetal hypoxia that may lead to cerebral palsy. A fetus suffering from hypoxia initially compensates by producing energy through anaerobic metabolism. At some stage, the fetus becomes decompensated and basic cellular functions fail, with risks of permanent morbidity or mortality. How long a fetus can survive on anaerobic metabolism differs because metabolic reserves differ, i.e., growth-restricted fetuses might deteriorate at an earlier stage. An increasing body of evidence has clarified brain-damaging mechanisms. Neuronal loss occurs in two phases: during the primary hypoxic event and later during the reperfusion/reoxygenation phase. Animal studies have suggested the possibility of prophylactic treatment to prevent neuronal loss after the hypoxic event. Intrapartum diagnostic tools should aim for detecting fetal hypoxemia/hypoxia when the fetus is still compensated. This may be achieved by assessment of biochemical data such as pH, lactate, and oxygen saturation, with the aim of prophylactic intervention before the fetus becomes decompensated. The measurement of cord blood levels of oxygen free radicals and excitatory amino acids at the time of birth may prove to be helpful in determining the risk of brain damage and evaluating the effect of prophylactic treatments to prevent or ameliorate brain injury from hypoxia.

Lactate in cord blood and its relationship to pH and catecholamines in spontaneous vaginal deliveries

The interrelationships between lactate and pH, nonadrenaline (NA), adrenaline (A) and dopamine (DA) were investigated in cord artery (CA) and vein (GV) blood at delivery. Sixty consecutive, spontaneous, vaginal deliveries with fetuses in cephalic presentation were assessed. Median gestational age at delivery was 40 weeks (range, 35-43). There were significant correlations between lactate and pH (P < 0.01), NA (P < 0.01), A (P < 0.05) and arterio-venous NA (P < 0.05) and DA differences (P < 0.01) in CA blood, while no variable correlated significantly to lactate in CV blood. The higher levels both of lactate and of catecholamines in CA blood are probably fetally derived. Dividing the material into high and low lactate subgroups (cut-off level, 75th percentile) showed a high lactate level to be associated with lower pH and higher catecholamine levels in CA blood, though the relationship was only statistically significant for pH. The levels both of catecholamines and of lactate were lower than those reported for cases of fetal distress, and reflect the lower level of fetal stress in the present series of normal deliveries. The low level of fetal stress and the differences in turnover rates between catecholamines and lactate might obscure their causal relationships, vis-a-vis fetal adaptation to extrauterine life during the course of parturition.

Umbilical cord venous progesterone at term delivery in relation to mode of delivery

OBJECTIVE

To determine whether the umbilical cord venous progesterone at term delivery is related to the mode of delivery.

METHODS

Thirty-nine pregnant patients at term were divided into three groups: elective cesarean section (control), spontaneous vaginal delivery, and emergency cesarean section. Umbilical cord venous and maternal serum progesterone were measured by radioimmunoassay. Statistical analysis was carried out using Student's t-test, with the level of significance set at P < 0.05.

RESULTS

Umbilical cord venous progesterone was significantly higher in babies delivered by emergency cesarean section (P < 0.001) and in those who had spontaneous vaginal delivery (P < 0.02), compared with the control group. Maternal serum progesterone concentrations showed no significant differences between the three groups. The Apgar scores of the stressed group of babies were significantly lower (P < 0.001).

CONCLUSION

The findings demonstrate that the fetuses exposed to stress during labor produce higher progesterone secretion. This could be one possible way the fetus protects itself against the sequelae of hypoxia.

Autacoids and control of human placental blood flow

1. Humans have a haemochorial, villous placenta. Uterine blood passes through maternal sinuses, bathing placental villi through which fetal blood circulates. Blood flow through each circulation is high and vascular resistance low. This haemodynamic situation is essential for efficient placental function. 2. The low placental vascular resistance is due to a lack of nervous influences together with pregnancy-induced changes promoting vasodilatation. Increases occur in output of the vasodilators prostacyclin and nitric oxide and also in membrane sodium pump activity. 3. Many autacoids are present in umbilical blood. Fetal vessels of the placenta develop intense vasoconstriction in the presence of some autacoids, such as thromboxane A2 and prostaglandins F2 alpha and E2, and respond weakly to others, such as angiotensin II and 5-hydroxytryptamine. Nevertheless, vasodilator influences predominate. 4. The diseases of pre-eclampsia and fetal growth retardation are associated with reduced output of nitric oxide and prostacyclin and with increased production of thromboxane A2 and endothelin-1. These changes promote vasoconstriction, increased vascular sensitivity to vasoconstrictor stimuli, platelet aggregation and intravascular coagulation, retarding blood flow and feto-placental growth. 5. Aspirin and glyceryl trinitrate have been investigated for possible therapeutic use in pre-eclampsia and fetal growth retardation. Improved drug therapy is likely as knowledge increases of the importance of autacoids in normal placental function and in the changes that occur during disease.

Cumulative changes in the fetal electrocardiogram and biochemical indices of fetal hypoxia

Previous studies have shown that the relationship between P-R interval of the fetal electrocardiogram (FECG) and the fetal heart rate (FHR) varies according to the acid-base status of the fetus. In the normal fetus there is a negative correlation between these two parameters. However, as acidosis develops, the relationship becomes positive. In order to express this relationship in a quantitative form, an index known as the ratio index (RI) has been derived. This index provides a cumulative time based description of the relationship between the P-R interval and FHR for the whole labour. The aim of this study was to evaluate this derived index and compare it with fetal hypoxia. The FECG was recorded from 132 fetuses during labour using a fetal scalp electrode, and analysed using the Nottingham FECG system. Changes in the nature of this relationship between the P-R interval and heart rate were compared against biochemical markers of asphyxia, namely umbilical artery pH, lactate and umbilical venous norepinephrine and hypoxanthine. Significant correlations were demonstrated between the RI and umbilical arterial pH (r = -0.38, P < 0.01), lactate (r = 0.36, P < 0.01), log10norepinephrine (r = 0.37, P < 0.01), and hypoxanthine (r = 0.28, P < 0.01). The measurement of the ratio index during labour may be a useful method of determining fetal hypoxia during labour.

Catecholamine levels and associated cardiovascular responses in infants with meconium-stained amniotic fluid

Catecholamine levels and associated cardiovascular responses were determined in 21 control and 30 term infants with meconium-stained amniotic fluid (MSAF). Cord arterial blood was obtained for determination for norepinephrine (NE) and epinephrine (EPI) levels; cardiovascular measurements included heart rate and systolic blood pressure at 30 min. Pregnancy was uncomplicated in all cases. The total length of labor 964 +/- 402 versus 555 +/- 312 min (P < 0.001) and active phase of labor 300 +/- 261 versus 135 +/- 104 min (P < 0.001) were significantly longer in MSAF infants when compared to controls. The 1 min Apgar score was < 7 (range 1-6) in 11 of 30 MSAF infants versus 0 of 21 control infants; these 11 infants required positive pressure ventilation for approximately 60 s secondary to transient respiratory depression (RD). The 5 min Apgar score was > 7 in 49 of the 51 infants. Infants with MSAF exhibited a higher PaCO2 (6.89 +/- 1.17 vs 6.24 +/- 1.17 mmHg; P < 0.02) and lower pH (7.25 +/- 0.06 vs 7.29 +/- 0.05; P < 0.02) compared to controls. Infants with transient RD demonstrated the most marked arterial blood gas differences, i.e., PCO2 7.41 +/- 1.30 mmHg (P < 0.001), pH 7.21 +/- 0.07 (P < 0.001) and base deficit -6 +/- 4 versus -3 +/- 2.8 (P < 0.001) when compared to controls. NE and EPI levels were significantly higher in MSAF versus control infants, i.e., 12600 +/- 3040 versus 3740 +/- 1000 pg/ml (SEM) (P < 0.02) and 1550 +/- 250 versus 620 +/- 130 pg/ml (P < 0.001) respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

AUTACOIDS AFFECTING VASCULAR TONE IN THE HUMAN FETAL EXTRACORPOREAL CIRCULATION

1. The human fetal extracorporeal circulation is normally a vasodilated, low pressure system. 2. As this vasculature lacks innervation, autacoids have been postulated as being of great importance in controlling its tone. 3. This has now been confirmed by pharmacological in vitro techniques, particularly utilizing perfusion of the isolated umbilical cord and placental lobule. 4. The fetal umbilical-placental vessels are sensitive to a wide range of vasoconstrictor autacoids, some of which can cause intense vasospasm. 5. Thromboxane A2 receptors have been identified in both umbilical vein and placental villous vessels. 6. Prostacyclin and endothelial cell-derived relaxing factor (or nitric oxide) may be largely responsible for the low vascular resistance normally found in the fetal extracorporeal circulation. 7. Immediately after birth it is likely that stimuli such as cooling, stretching and handling of the umbilical cord cause release of eicosanoids and other autacoids from the vessels, leading to their complete closure.

Catecholamine secretion in fetal adaptation to stress

From the beginning of labor, the fetus must successfully adapt from intrauterine life to the stress of birth and, finally, to extrauterine life. The role of hormones known as catecholamines in this adaptive mechanism is described. An understanding of the physiology of catecholamine secretion will enhance the nursing care of mothers and their infants during this important transitional period.

Biochemical changes in the mother and the fetus during labor and its significance for the management of the second stage

In 69 patients with uneventful pregnancies, term labor was studied prospectively with respect to length of second stage, number of bearing down efforts, maternal and fetal levels of lactate, epinephrine and norepinephrine. Maternal venous blood concentrations were measured in early labor and at the time of delivery while samples from umbilical artery and vein provided fetal blood. There was a significant rise of lactate and catecholamines in maternal blood during labor and at delivery fetal lactate concentration was lower than the maternal level while for epinephrine and norepinephrine fetal levels were higher. For all three compounds umbilical artery concentrations were higher than umbilical venous levels. While there was no correlation between the biochemical parameters in maternal blood and length of second stage maternal lactate and norepinephrine concentration at the time of delivery significantly correlated with the number of bearing down efforts. Umbilical artery lactate correlated with both, length of second stage and number of bearing down efforts.

Does ephedrine influence newborn neurobehavioural responses and spectral EEG when used to prevent maternal hypotension during caesarean section?

The recovery of 16 infants born by elective caesarean section with spinal anaesthesia, in which either ephedrine or fluid load was used to prevent maternal hypotension, were studied using Scanlon's neurobehavioural tests and a computerized EEG. Neurobehavioural testing showed no differences between the ephedrine and the non-ephedrine groups of infants at ages of 3 h, 1 day, 2 days and 4-5 days, whereas the spectral EEG showed significant differences between the two groups during the first 2 h after delivery, which had disappeared 24 h later. It is suggested that small doses of ephedrine given to the mother i.v. to prevent hypotension during spinal anaesthesia have short-lived effects on the neonate's central nervous system, which will be detected in the spectral EEG, but not in neurobehavioural tests.

Cardiac function and sympathoadrenal activity in the newborn after cesarean section under spinal and epidural anesthesia

Left ventricular systolic time intervals, bupivacaine concentrations, adrenaline and noradrenaline levels were determined in 19 neonates delivered by elective cesarean section. Ten of the cesarean sections were performed under spinal and nine under epidural anesthesia. Plain bupivacaine 0.5% was used for the epidural anesthesia and bupivacaine 0.5% in glucose 8% for the spinals. The noradrenaline and adrenaline levels were higher in the neonates whose mothers received epidural anesthesia. The differences in catecholamine and bupivacaine concentrations were not associated with differences in left ventricular dynamics, or the timing of postnatal circulatory changes. The significant exposure of the neonate to bupivacaine, at maternal epidural anesthesia, seems to have no negative effect on early neonatal circulation in the healthy term infant.

Maternal and fetal endocrine stress response at vaginal delivery with and without an epidural block

Maternal and fetal stress response at vaginal delivery were studied in 19 normal parturients at term. Ten patients to whom an epidural block (group EA) had been administered were compared with 9 patients (group NEA) who used only nitrous oxide for pain relief. Plasma concentrations of ACTH, cortisol, 17-alpha-hydroxyprogesterone, blood glucose and catecholamines were measured in maternal and umbilical vein blood at delivery and in maternal vein blood 30 minutes after delivery. At delivery maternal plasma concentrations of ACTH, cortisol and catecholamines were lower in the EA group compared with in the NEA group. There were no differences in umbilical plasma concentrations of the studied stress variables between the two groups. A linear relation was demonstrated between maternal and umbilical vein cortisol concentration. In both the EA and NEA group a significant fall in ACTH, 17-alpha-hydroxyprogesterone and catecholamine concentrations were demonstrated 30 minutes after delivery, whereas cortisol and blood glucose were virtually unchanged. It was found that epidural anesthesia reduced the maternal stress hormones at delivery but seemed to have little or no effect on the fetal endocrine stress hormones.

Catecholamines in arterial and venous umbilical blood: placental extraction, correlation with fetal hypoxia, and transcutaneous partial oxygen tension

In 34 parturient women the levels of free epinephrine (E), norepinephrine (NE), and dopamine (D) were determined by a radioenzymatic method using maternal venous and umbilical arterial and venous blood. The study was conducted to investigate the relationship between fetal catecholamines and hypoxia, fetal heart rate (FHR), and transcutaneous pO2 (tcpO2). The placental catecholamine extraction rates were also calculated. Results The NE concentrations (10,200 pg/ml) and the E concentrations (1,120 pg/ml) in the fetal arterial blood were highly elevated with mean values increased 4-fold over umbilical vein values. Compared with the maternal venous blood, NE values were increased 20-fold, and E values 10-fold. Free D concentrations in fetal arterial blood (130 pg/ml) had risen 2.5-fold over maternal levels. These results suggest that the catecholamines measured in cord blood are of fetal origin and that the placenta has a high capacity for inactivation of free catecholamines. The placental extraction rate is 77 +/- 14% for NE, 76 +/- 16% for E, and 33 +/- 25% for D. The placental extraction rates for E and NE were virtually identical; in agreement with morphological studies they demonstrated absence of sympathetic innervation on the fetal side of the placenta. Highly significant correlations were found between fetal arterial NE concentrations and the 1-minute APGAR score, pH and base deficit in the umbilical artery and alterations of the FHR (deceleration area, baseline FHR). Further analysis of FHR alterations reveals that an increase in deceleration area without tachycardia is not correlated with an increase of fetal arterial NE concentration. A significant rise in NE was only found with additional tachycardia which is often associated with a loss of oscillation amplitude. Fetal arterial E concentrations were found to correlate with the fetal parameters indicating increased adrenal secretion of the hormone during fetal stress. However, correlation coefficients were lower than those obtained for NE. A significant effect of fetal hypoxia on arterial and venous D levels could not be demonstrated. Fetal tcpO2 varies between 0-25 mm Hg during the last two hours before delivery. In most cases tcpO2 was lower than the arterial pO2. Besides epidermal thickness and artifacts, skin perfusion is a major factor influencing the tcpO2 (transcutaneous arterial pO2 difference). Vasoconstriction of the cutaneous vessels induced by increased NE secretion during hypoxia may obviously produce a fall in tcpO2.(ABSTRACT TRUNCATED AT 400 WORDS)

Sympathoadrenal activity and peripheral blood flow after birth: comparison in infants delivered vaginally and by cesarean section

The possible influence of sympathoadrenal activity on peripheral blood flow was studied. Limb blood flow was measured with venous occlusion plethysmography at 30 minutes, 2 hours, and 24 hours after birth in 24 healthy, full-term infants, of whom 14 were delivered by elective cesarean section. Mean arterial pressure was simultaneously measured noninvasively, and peripheral vascular resistance calculated. Umbilical artery blood at birth and peripheral venous blood at 2 and 24 hours were analyzed for concentrations of catecholamines and hematocrit. The limb blood flow was significantly lower at 30 minutes in the vaginally delivered infants compared with those delivered by cesarean section. There was a gradual increase in limb blood flow over the 24 hours in those delivered vaginally, whereas in the section group only small changes were observed. The peripheral vascular resistance was higher both at 30 minutes and at 2 hours in those delivered vaginally, which corresponded to the higher catecholamine concentrations at birth and at 2 hours in this group. Two hours after birth there was a significant correlation between noradrenaline levels and peripheral vascular resistance. The results indicate that the sympathoadrenal system influences peripheral circulation at birth and is important in the circulatory adaptation of the newborn infant.

Transfer and metabolism of norepinephrine studied from maternal-to-fetal and fetal-to-maternal sides in the in vitro perfused human placental lobe

An in vitro system for the dual perfusion of an isolated lobe of human placenta was used to study transfer and metabolism of 3H-labeled norepinephrine at two different concentrations. At 39 mumol/L, the transfer of total radioactivity from the maternal to the fetal side was 11.60% +/- 0.60% and significantly higher (p less than 0.05) than that in the opposite direction (6.50% +/- 0.37%). In both directions almost 50% of tritium was transferred as norepinephrine while the rest was metabolized and appeared on the other side as normetanephrine, dihydroxymandelic acid, and vanillylmandelic acid. When a reduced concentration (870 nmol/L) was infused into either the maternal or the fetal compartment, transfer and metabolism were similar to those determined before. Analysis of the tissue showed 50% of total radioactivity as normetanephrine, dihydroxymandelic acid, and vanillylmandelic acid and 17% as conjugates. Inclusion of the monoamine oxidase inhibitor clorgyline in the perfusate significantly reduced fetal-to-maternal transfer but not transfer in the reverse direction. In addition, inhibition of placental monoamine oxidase resulted in a considerable reduction in dihydroxymandelic acid and vanillylmandelic acid while the normetanephrine fraction increased. Norepinephrine significantly increased glucose utilization and lactate production. A possible physiologic role of norepinephrine transferred from the fetal into the maternal circulation during labor is discussed.

Fetal scalp catecholamines during labor

Samples of scalp blood were collected from 129 fetuses during the first stage of labor for analysis of plasma norepinephrine and epinephrine concentrations by high-performance liquid chromatography. The catecholamine levels were related to scalp blood pH and fetal heart rate patterns during the 20-minute period preceding the collection of scalp blood. The median norepinephrine level was 9.2 nmol/L (range, 1.3 to 99.7), and the median epinephrine level was 0.5 nmol/L (range, less than 0.5 to 19.2) (n = 111) during the first stage of labor when the pH was above 7.25. The norepinephrine level was considerably higher than that in the resting adult. Significantly higher concentrations of catecholamines were found when scalp blood pH was below 7.26 (p less than 0.001). Maternal analgesia did not influence the fetal catecholamine levels in uncomplicated labor. Significantly higher concentrations of norepinephrine were found during the appearance of abnormal fetal heart rate patterns.

Plasma progesterone in the umbilical vessels at term--an overview

This paper reports the results of umbilical cord vein and artery, and maternal peripheral vein plasma progesterone levels in over 300 term human deliveries, individual aspects of which have previously been reported. An attempt was made to assess the fetal status objectively, and the results confirm that cord progesterone levels are correlated with the mode of delivery, the clinical indications for the mode of delivery and the clinical condition of the fetus after delivery. No relation was found to fetal sex, induction of labour or maternal antenatal complications.

Role of labour in the establishment of functional residual capacity at birth

Intrathoracic pressure and volume changes were measured during the spontaneous first breath in 11 healthy term neonates delivered by emergency caesarean section (CS). Although inspiratory and expiratory rates were higher than those found among babies delivered by elective CS, inspiratory volume was very similar and these babies, unlike those delivered by elective CS, had all formed a functional residual capacity at the end of the first breath. We obtained cord arterial and venous samples for catecholamine analysis concurrently, and found that most of the babies had concentrations of plasma noradrenaline similar to babies delivered by elective CS--high values were found only among infants who had suffered fetal distress. Both catecholamine excretion and method of delivery may be important in the formation of the functional residual capacity at birth.