Doppler ultrasonographic evidence of intrapartum brain-sparing effect in fetuses with low oxygen saturation according to pulse oximetry

How to Reach the Best Ultrasound Performance in the Delivery Room

Ultrasonography is an instrument that is present in the maternal-fetal assessment throughout pregnancy and with widely documented benefits, but its use in intrapartum is becoming increasingly relevant. From the assessment of labor progression to the assessment of placental disorders, ultrasound can be used to correlate with physiological findings and physical examination, as its benefit in the delivery room cannot yet be proven. There are still few professionals with adequate training for its use in the delivery room and for the correct interpretation of data. Thus, this article aims to present a review of the entire applicability of ultrasound in the delivery room, considering the main stages of labor. There is still limited research in evidence-based medicine of its various possible uses in intrapartum, but it is expected that further studies can bring improvements in the quality of maternal and neonatal health during labor.

Associations of maternal personal exposure to air pollution on fetal weight and fetoplacental Doppler: A prospective cohort study

We determined the influence of maternal air pollution exposure during each trimester of pregnancy on fetal and birth weight and fetoplacental hemodynamics. In total, 366 women with singleton pregnancies were prospectively followed in the city of São Paulo, Brazil. Nitrogen dioxide (NO2) and ozone (O3) were measured during each trimester using passive personal samplers. We evaluated fetal weight and Doppler velocimetry data from the umbilical, middle cerebral, and uterine arteries in the 3rd trimester, and birth weight. Multivariate analysis was performed, controlling for known determinants of fetal weight. Exposure to higher levels of O3 during the 2nd trimester was associated with higher umbilical artery pulsatility indices (PIs) [p=0.013; beta=0.017: standard error (SE)=0.007]. Exposure to higher levels of O3 during the 3rd trimester was associated with lower umbilical artery PIs (p=0.011; beta=-0.021; SE=0.008). Our results suggest that in the environment of São Paulo, O3 may affects placental vascular resistance.

Fetal anesthesia and pain management for intrauterine therapy

Anesthesia provision for fetal intervention differs from most other anesthetic situations insofar as anesthesiologists must care for 2 or more patients-each with potentially conflicting requirements. The first is the mother who can readily indicate discomforts, can be monitored directly, and to whom drugs may be administered directly and easily. For the fetus (or fetuses), nociception must be assumed or inferred indirectly, monitoring is limited at best, and drug administration is complicated and often indirect. Fetal and maternal hemodynamic stability must be assured; and a plan to resuscitate the fetus, should problems occur during the procedure, must be developed.

[Fetal assessment of the labor admission in low risk pregnancies]

The assessment of fetal well-being at the beginning of labor must lead to an appropriate monitoring, adapted to the present risks. Even if some medical events are unforeseeable, three ways of reflexions get clear: abnormal maternofetal signs at the admission indicate the need for an increased monitoring (NP5); the reading of the medical file could reveal a high-risk pregnancy; at least, the realization of electronic fetal heart rate monitoring for any woman at the beginning of the labor is recommended: in case of normality, it remains a good criterion of a fetal good health. In this context of admission, there is no evidence supporting that other techniques (amnioscopy, acoustic test, echography, Doppler, etc.) could be beneficial in low-risk women and be recommended (NP5). Research is to be continued in this field.

Ductus venosus Doppler measurement during labor

OBJECTIVES

To assess ductus venosus (DV) indices during the first stage of labor and the effect of ruptured membranes, meconium stained liquor and epidural analgesia (EDA).

METHODS

Prospective cross-sectional study. Eighty-one women with low-risk singleton term pregnancies participated, 51 had normal labor (Group 1), and 30 experienced ruptured membranes and/or stained liquor (Group 2). Of the latter group 14 received EDA. The effect of various interventions and application of EDA on the ductus venosus index (DVI) and pulsatility index for veins (DV PIV) were tested.

RESULTS

The feasibility rate was 94%. A significant increase of DV indices (DVI, DV PIV) was found in group 2 (P<0.001 and P<0.0005, respectively). The A-velocity was also significantly lower in group 2 (P<0.02). A markedly significant increase of DV indices (P<0.0001) among participants receiving EDA was observed in group 2. The mean+/-SD indices were: 0.53+/-0.10 for the DVI and 0.68+/-0.14 for the DV PIV in those women. There was a significant positive correlation of DV indices with the duration of amniorrhea in group 2 (PIV: r=0.66; P<0.002; DVI: r=0.68; P<0.001).

CONCLUSIONS

Long-term amniorrhea seems to affect the fetal venous circulation reflected in increased DV waveform indices.

Alterations in Doppler velocimetry indices of the umbilical artery during fetal hypoxia in labor, in relation to cardiotocography and fetal pulse oximetry findings

AIM

The aim was to investigate fetal peripheral blood flow using external cardiotocography (CTG), Doppler velocimetry, and pulse oximetry (PO) in normal labor compared with those complicated by hypoxia.

SUBJECTS

During labor, 35 term fetuses with oxygen saturation values (FSPO(2)) between 30 and 40%, and 25 term fetuses with FSPO(2) values < or =30% for a period of 20 s to 2 min were studied. Fetuses were assessed using simultaneous CTG, PO, and Doppler ultrasonography of the umbilical artery (UA). The pulsatility index (PI), resistance index (RI), and flow velocity integral (FVI) were recorded. Peripartum outcomes were compared with those of 30 fetuses with SPO(2) values >40%. All groups presented abnormal CTG patterns and were comparable with regard to maternal age and parity.

SETTING

The Fetal Surveillance Unit of the 2nd Department of Obstetrics and Gynecology, "Aretaieion" Hospital, Athens University, Greece.

RESULTS

Umbilical artery Doppler revealed an initial increase in the RI and the PI in the presence of decreased oxygen saturation. The differences observed in Doppler velocity and impedance indices correlated with PO values. Fetal outcomes correlated with UA Doppler findings.

CONCLUSIONS

Alterations in UA Doppler velocimetry indices were observed during labor-induced fetal hypoxia. PO readings of <40% provoked an increase in the RI and PI. When PO readings remained <30% for >2 min, both the PI and the RI were further increased in a more prominent way. UA velocimetry indices correlated with perinatal outcome.

Evaluation of fetal intrapartum hypoxia by middle cerebral and umbilical artery Doppler velocimetry with simultaneous cardiotocography and pulse oximetry

OBJECTIVE

To investigate fetal circulation at different stages of hypoxia during labor, and to study blood flow alterations in the brain and peripheral tissues, through simultaneous use of three non-invasive techniques.

MATERIALS AND METHODS

Ninety two pregnant women between 38 and 41 weeks of gestation, comparable for maternal age and parity, were simultaneously monitored with cardiotocography (CTG), continuous fetal pulse oximetry and Doppler ultrasonography during the first stage of labor. In 70 cases evaluation was successful, and useful data was obtained. Doppler waveforms were obtained before and during abnormal CTG patterns, of both the umbilical (UA) and middle cerebral artery (MCA) to measure the pulsatility index (PI), resistance index (RI), and flow velocity integral (FVI). The study population was divided in three groups, according to CTG and fetal pulse oximetry tracings: 20 term fetuses with normal CTG patterns and oxygen saturation (FSPO(2)) values >40%, 30 term fetuses with abnormal CTG patterns and FSPO(2) values between 30 and 40%, and 20 fetuses with abnormal CTG patterns and FSPO(2) values <30% for a time up to 2 min. These were studied and peripartum outcomes were compared.

RESULTS

Redistribution of blood flow was noted at FSPO(2) values of 37%, in all groups. In the presence of reduced oxygen saturation (near to or below 30%), MCA Doppler showed significantly lower PI (1.06+/-0.33 vs.0.74+/-0.39, p=0.03) and RI (0.59+/-0.14 vs. 0.44+/-0.14, p=0.03), while that of the UA showed mildly higher resistance indices (0.98+/-0.14 vs. 1.28+/-0.50, p=0.01 and 0.57+/-0.12 vs. 0.79+/-0.24, p=0.004, respectively). When an oxygen saturation value of <30% was maintained for greater than 2 min, MCA Doppler indices reversed, likely indicating morbid fetal hypoxia. Differences in fetal outcomes between groups correlated with Doppler and pulse oximetry tracings.

CONCLUSIONS

During active labor the fetus maintains oxygen supply to the brain by redistributing blood flow. In cases of hypoxia this is feasible for only 2 min. We note a strong correlation between fetal pulse oximetry, Doppler velocimetry of the MCA and UA, and fetal morbidity.

The clinical significance of Doppler findings in fetal middle cerebral artery during labor

OBJECTIVES

(1) To investigate fetal intracranial circulation, relative to peripheral blood flow, during labor with abnormal cardiotocographic (CTG) patterns, using three non-invasive methods. (2) To determine the utility of monitoring middle cerebral artery (MCA) Doppler during labor.

INTERVENTIONS

Fetuses were assessed using simultaneous CTG, pulse oximetry, and Doppler ultrasonography of both the MCA and umbilical artery (UA) to measure the pulsatility index (PI), resistance index (RI), and flow velocity integral (FVI).

STUDY DESIGN

During labor 20 term fetuses with abnormal CTG patterns and oxygen saturation values >30%, and 24 term fetuses with abnormal CTG patterns and oxygen saturation values <30% were studied, and peripartum outcomes were compared. The groups were comparable with regard to maternal age and parity. Results were evaluated using the Student's t-test and Fisher exact test.

RESULTS

MCA Doppler showed significantly lower PI and RI, and higher FVI in the presence of reduced oxygen saturation. Differences in fetal outcomes between the two groups correlated with MCA Doppler findings.

CONCLUSIONS

In experienced hands, Doppler screening of fetal middle cerebral artery waveforms during labor can be useful in the evaluation of intrapartum hypoxia in complicated pregnancies.

Cerebral hemoglobin concentration and oxygen saturation measured by intensity modulated optical spectroscopy in the human fetus during labor

AIMS

To quantify hemoglobin concentration and oxygen saturation in the human fetal brain using intensity modulated optical spectroscopy during labor.

METHODS

A specially designed probe was applied to the fetal scalp in 20 women during uncomplicated labor at term. Optical fibres transmitted near infra-red light to and from an intensity modulated optical spectrometer (IMOS), which detected changes in the optical parameters of the infra-red light source. Using novel off-line analytic techniques, these changes were converted into absolute measurements of oxyhemoglobin (HbO2) and deoxyhemoglobin (Hb). Summing Hb and HbO2 gives total hemoglobin concentration (HbT) and HbO2/HbT x 100% provided measurements of cerebral saturation (SmcO2).

RESULTS

Of 20 fetuses studied, data from 10 fetuses were suitable for analysis. Over three consecutive uterine contractions, the mean (+/- SD) absolute cerebral concentrations of Hb and HbO2 were 30 +/- 18 and 46 +/- 21 mumol/l, respectively. This gave a mean cerebral HbT of 77 +/- 29 mumol/l and a mean SmcO2 of 59 +/- 12%. In the other ten fetuses insufficient light was detected to allow chromophore quantification.

CONCLUSION

These are the first absolute measurements of cerebral Hb and HbO2 in human fetuses during labor. The values of total hemoglobin are similar to those obtained in neonates with hypoxia-ischemia and the measurements of fetal cerebral oxygen saturation are similar to previously published values.

Magnetic resonance proton spectroscopy and diffusion weighted imaging of chick embryo brain in ovo

Metabolic compensatory mechanisms may partly account for the decreased vulnerability to hypoxia observed in the developing brain. We used proton magnetic resonance spectroscopy and diffusion-weighted imaging to measure the cerebral concentrations of lactate and other metabolites, as well as the apparent diffusion coefficient (ADC) of tissue water, before, during and after hypoxia in anaesthetised chick embryos in ovo. Reducing the inspired oxygen concentration to 8% for 40 min caused a significant rise in both mean (+/-S.D.) lactate:creatine and alanine:creatine ratios from 0.58 (0.41) to 1.56 (0.56) and 0.14 (0.14) to 0.29 (0.17), respectively. Under similar hypoxic conditions, ADC did not change from a mean baseline value of 0.95 (0.09), but did fall to 0.40 (0.12) x 10(9) mm(2) s(-1) with further stepwise reductions in oxygenation. Moderate hypoxia increases lactate concentration in the developing chick brain without compromising cellular energy metabolism.

Cerebral hemodynamics and fetal behavioral states

OBJECTIVE

This study aimed to evaluate the hemodynamic patterns of the proximal (M1) and distal (M2) portions of the middle cerebral artery, during different fetal behavioral states.

DESIGN

The study included 20 normal singleton pregnancies at between 36 and 40 weeks of gestation. After identification of the fetal behavioral state (FBS), flow velocity evaluation was performed on the proximal and distal segments of the middle cerebral artery during 'quiescence' (FBS-1F) and 'activity' (FBS-2F).

RESULTS

A statistically significant decrease of pulsatility index, reflecting a decrease of impedance to flow values, was identified in both segments of the middle cerebral artery (MCA) during 'activity', with a more marked decrease in the MCA-M2 than in MCA-M1 (M1, P = 0.0028; M2, P = 0.00000085). The mean fetal heart rate during 'quiescence' was significantly lower than during 'activity' (P = 0.0047). However, there was no significant correlation between the pulsatility index of both segments of the middle cerebral artery and the fetal heart rate during different fetal behavioral states.

CONCLUSIONS

The results of this study provide evidence of the influence of different fetal behavioral states on fetal cerebral hemodynamic patterns. We believe it is better to sample the proximal segment in clinical practice because it is less influenced by fetal behavioral state. This information should be considered when evaluating fetal cerebral hemodynamics.