Effect of maternal oxytocin on umbilical venous and arterial blood flows during physiological-based cord clamping in preterm lambs.

BACKGROUND: Delayed umbilical cord clamping (UCC) after birth is thought to cause placental to infant blood transfusion, but the mechanisms are unknown. It has been suggested that uterine contractions force blood out of the placenta and into the infant during delayed cord clamping. We have investigated the effect of uterine contractions, induced by maternal oxytocin administration, on umbilical artery (UA) and venous (UV) blood flows before and after ventilation onset to determine whether uterine contractions cause placental transfusion in preterm lambs. METHODS AND FINDINGS: At ~128 days of gestation, UA and UV blood flows, pulmonary arterial blood flow (PBF) and carotid arterial (CA) pressures and blood flows were measured in three groups of fetal sheep during delayed UCC; maternal oxytocin following mifepristone, mifepristone alone, and saline controls. Each successive uterine contraction significantly (p<0.05) decreased UV (26.2±6.0 to 14.1±4.5 mL.min-1.kg-1) and UA (41.2±6.3 to 20.7 ± 4.0 mL.min-1.kg-1) flows and increased CA pressure and flow (47.1±3.4 to 52.8±3.5 mmHg and 29.4±2.6 to 37.3±3.4 mL.min-1.kg-1). These flows and pressures were partially restored between contractions, but did not return to pre-oxytocin administration levels. Ventilation onset during DCC increased the effects of uterine contractions on UA and UV flows, with retrograde UA flow (away from the placenta) commonly occurring during diastole. CONCLUSIONS: We found no evidence that amplification of uterine contractions with oxytocin increase placental transfusion during DCC. Instead they decreased both UA and UV flow and caused a net loss of blood from the lamb. Uterine contractions did, however, have significant cardiovascular effects and reduced systemic and cerebral oxygenation.

Longitudinal systolic left ventricular function in preterm and term neonates: reference values of the mitral annular plane systolic excursion (MAPSE) and calculation of z-scores.

The mitral annular plane systolic excursion (MAPSE) is a quick and reliable echocardiographic tool for assessing longitudinal left ventricular (LV) systolic function in children and adults. Because this parameter is affected by the LV longitudinal dimension, pediatric and adult normal values are not suitable for preterm and term neonates. A prospective study investigated a large group of preterm and term neonates [gestational age (GA), 26/0-6 to 40/0-6; birth weight (BW), 670-4,140 g]. The growth- and BW-related changes in MAPSE were determined to establish normal z-score values for preterm and term neonates. The MAPSE ranged from a mean of 0.36 ± 0.05 cm in preterm neonates with a GA of 26/0-6 to 0.56 ± 0.08 cm in term neonates with a GA of 40/0-6. The findings showed MAPSE, GA, and BW to be moderately correlated. Pearson's correlation coefficient was 0.56 for GA (MAPSE; p < 0.001) and 0.58 for BW (MAPSE; p < 0.001). The normal MAPSE values did not differ significantly between females and males (p = 0.946). The absolute values and z-scores of normal MAPSE values in healthy preterm and term neonates within the first 48 h of life were calculated, and percentile charts were established. Determination of LV function using MAPSE might be useful for vulnerable infants for whom a prolonged examination is inappropriate and for neonates with suboptimal visualization of the endocardium.

Time course study of blood pressure in term and preterm infants immediately after birth.

OBJECTIVE: To describe temporal changes in systolic, diastolic, and mean blood pressure (SBP, DBP, and MBP, respectively) in term and preterm infants immediately after birth. METHODS: Prospective observational two-center study. In term infants SBP, DBP, and MBP were assessed non-invasively every minute for the first 15 minutes, and in preterm infants every minute for the first 15 minutes, as well as at 20, 25, 30, 45, and 60 minutes after birth. Regression analyses were performed by gender and respiratory support in all neonates; and by mode of delivery, cord clamping time, and development of ultrasound-detected brain injury in preterm neonates. RESULTS: Term infants (n = 54) had a mean (SD) birth weight of 3298 (442) g and gestational age of 38 (1) weeks, and preterm infants (n = 94) weighed 1340 (672) g and were 30 (3) weeks gestation. Term infants' SBP, DBP and MBP within the first 15 minutes after birth were independent of gender or respiratory support. Linear mixed regression analysis showed that preterm infants, who were female, born vaginally, had delayed cord clamping and did not require positive pressure ventilation nor develop periventricular injury or ventriculomegaly, had significantly higher SBP, DBP, and MBP at some measurement points within the first hour after birth. CONCLUSIONS: We present novel reference ranges of BP immediately after birth in a cohort of term and preterm neonates. They may aid in optimization of cardiovascular support during early transition at all gestations.

Even mild respiratory distress alters tissue oxygenation significantly in preterm infants during neonatal transition.

UNLABELLED: Near-infrared spectroscopy (NIRS) enables continuous non-invasive measurements of regional oxygen saturation (rSO2). The aim was to evaluate the dynamics of rSO2 of the brain, preductal and postductal tissues during postnatal transition in preterm infants with and without respiratory support (RS). This single-centre study was designed as an exploratory prospective observational study. Fifty one preterm infants (≥ 30 + 0 and < 37 + 0 weeks) delivered by caesarean section were included. RS using a T-Piece-Resuscitator and supplemental oxygen were given according to guidelines. NIRS measurements were carried out by using Invos Monitor (Covidien; USA) for the first 15 min of life. Three NIRS transducers were attached on the forehead (rSO2brain), the right forearm (rSO2arm) and the left lower leg (rSO2leg). Two groups were compared based on need for RS: normal transition (NT) and RS group. RESULTS: In NT group rSO2brain increased over time and was significantly higher than rSO2arm, whereas in RS group rSO2brain and rSO2arm increased without significant differences. Courses of rSO2arm and rSO2leg increased over time and showed a converging pattern with initially lower values of rSO2leg in NT group and a diverging pattern with lower levels of rSO2leg in RS group. Overall, rSO2 levels were higher in NT compared to RS group. CONCLUSION: Our findings indicate that the decreased rSO2 levels in RS group compared to NT group are not only caused by lower arterial oxygen saturation levels, but also by a compromised perfusion even in infants with only mild respiratory distress.

Tidal volumes in spontaneously breathing preterm infants supported with continuous positive airway pressure.

OBJECTIVE: To describe changes in tidal volume (VT) and their correlation to changes in oxygen saturation and heart rate in spontaneously breathing preterm infants immediately after birth. STUDY DESIGN: In this prospective observational, 2-center study, a flow sensor was attached to the facemask of spontaneously breathing infants born at <37 weeks' gestational age who received continuous positive airway pressure (CPAP) immediately after birth. Respiratory function, heart rate, and oxygen saturation were continuously recorded during spontaneous breathing. RESULTS: Fifty-five infants (mean [SD] gestational age 31 [26-36] weeks and birth weight 1647 [500] g) received mask CPAP in the delivery room. CPAP was started at a median (IQR) 90 (60-118) seconds after birth and was delivered for 720 (300-900) seconds. Median VT ranged between 4.2 and 5.8 mL/kg with the individual VT varied between 0.9 and 19.8 mL/kg. Overall, VT increased over the first few minutes after birth and decreased thereafter. The increase in saturation after birth lagged behind the published normal ranges for spontaneously breathing preterm infants without CPAP. CONCLUSIONS: The 50th percentile for spontaneous VT in preterm infants during mask CPAP ranged from 4.2 to 5.8 mL/kg, with wide individual variation observed in the first minutes after birth. Preterm infants requiring CPAP after birth may take longer to achieve so-called "normal" saturation targets.

Human or monitor feedback to improve mask ventilation during simulated neonatal cardiopulmonary resuscitation.

OBJECTIVE: To investigate if external chest compressions (ECC) increase mask leak, and if human or technical feedback improves mask ventilation during simulated neonatal cardiopulmonary resuscitation (CPR). STUDY DESIGN: In this observational study, 32 participants delivered positive pressure ventilation (PPV) to a modified, leak-free manikin via facemask. Mask leak, tidal volume (VT), positive end expiratory pressure (PEEP) and respiratory rate (RR) were measured with a respiratory function monitor (RFM). Participants had to perform four studies. In the first study, participants performed PPV alone as baseline. Thereafter, three studies were performed in random order. In the PPV+ECC+manometer group, participants had to observe the manometer while the RFM was covered; in the PPV+ECC+RFM group, the RFM was used while the manometer was covered; and in the PPV+ECC+verbal feedback group, the RFM and manometer were covered while a team leader viewed the RFM and provided verbal feedback to the participants. RESULTS: Median (IQR) mask leak of all studies was 15% (5-47%). Comparing the studies, PPV+ECC+RFM and PPV+ECC+verbal feedback had significantly less mask leak than PPV+ECC+manometer. Mean (SD) VT of all studies was 9.5±3.5 mL. Comparing all studies, PPV+ECC+RFM had a significantly higher VT than PPV and PPV+ECC+manometer. As well, PPV+ECC+verbal feedback had a significantly higher VT than PPV. PEEP and RR were within our target, mean (SD) PEEP was 6±2 cmH2O and RR was 36±13/min. CONCLUSIONS: During simulated neonatal CPR, ECCs did not influence mask leak, and a RFM and verbal feedback were helpful methods to reduce mask leak and increase VT significantly.

Reference ranges for regional cerebral tissue oxygen saturation and fractional oxygen extraction in neonates during immediate transition after birth.

OBJECTIVE: To define reference ranges for regional cerebral tissue oxygen saturation (crSO2) and regional cerebral fractional tissue oxygen extraction (cFTOE) during the first 15 minutes after birth in neonates requiring no medical support. STUDY DESIGN: The crSO2 was measured using near infrared spectroscopy (Invos 5100 cerebral/somatic oximeter monitor; Somanetics Corp, Troy, Michigan) during the first 15 minutes after birth for term and preterm neonates. The near infrared spectroscopy sensor was placed on the left forehead. Peripheral oxygen saturation and heart rate were continuously measured by pulse oximetry, and cFTOE was calculated. Neonates were excluded if they required any medical support. RESULTS: A total of 381 neonates were included: 82 term neonates after vaginal delivery, 272 term neonates after cesarean delivery, and 27 preterm neonates after cesarean delivery. In all neonates, median (10th-90th percentiles) crSO2 was 41% (23-64) at 2 minutes, 68% (45-85) at 5 minutes, 79% (65-90) at 10 minutes, and 77% (63-89) at 15 minutes of age. In all neonates, median (10th-90th percentiles) cFTOE was 33% (11-70) at 2 minutes, 21% (6-45) at 5 minutes, 15% (5-31) at 10 minutes, and 18% (7-34) at 15 minutes of age. CONCLUSION: We report reference ranges of crSO2 and cFTOE in neonates requiring no medical support during transition immediately after birth. The use of cerebral oxygenation monitoring and use of these reference ranges in neonates during transition may help to guide oxygen delivery and avoid cerebral hypo-oxygenation and hyperoxygenation.

The influence of perinatal asphyxia on peripheral oxygenation and perfusion in neonates.

BACKGROUND: Perinatal asphyxia influences peripheral oxygenation and perfusion in neonates. OBJECTIVES: The aim was to investigate the influence of perinatal asphyxia on peripheral oxygenation and perfusion in neonates by using near-infrared spectroscopy (NIRS). METHODS: Prospective observational study. Neonates with gestational age >34 weeks and birth weight >2000 g without infection or congenital malformations were included. Peripheral muscle NIRS measurements in combination with venous occlusion were performed once in the first 48 h of life. Tissue oxygenation index (TOI), mixed venous oxygenation (SvO2), fractional oxygen extraction (FOE), haemoglobin flow (Hbflow), oxygen delivery (DO2) and oxygen consumption (VO2) were assessed. Furthermore arterial oxygen saturation, heart rate, blood pressure and temperatures were measured. Neonates with a UapH≤7.15 and an Apgar 5≤6 were compared to neonates with a UapH≥7.15, an Apgar 5≥7 (control group) and a UapH was correlated to NIRS parameters. RESULTS: 8 asphyxiated neonates were compared to 30 neonates in the control group. TOI (67.7±5.5%) and DO2 (29.0±14.2 µmol/100 mL/min) were significantly lower in asphyxiated neonates compared to the controls (TOI 71.8±4.9%, p=0.045; DO2 43.9±16.9 µmol/100 mL/min, p=0.028) and FOE was significantly higher (0.33±0.05) compared to the controls (0.28±0.06, p=0.028). Furthermore significant correlations between UapH and DO2 (r=0.78, p=0.022), VO2 (r=0.80, p=0.018) and FOE (r=-0.75, p=0.034) in the asphyxiated group were found. CONCLUSION: Peripheral oxygenation and perfusion measured with NIRS are compromised in neonates with perinatal asphyxia with worsening of parameters and degree of acidosis in the umbilical cord blood.

Right ventricular performance in preterm and term neonates: reference values of the tricuspid annular peak systolic velocity measured by tissue Doppler imaging.

BACKGROUND: The tricuspid annular peak systolic velocity (S') is an echocardiographic measurement to assess systolic right ventricular function in adults and children. OBJECTIVE: We determined growth and birth weight-related changes of S' to establish reference values in preterm and term neonates. METHODS: A prospective study was conducted in a group of 290 preterm and term neonates (gestational age 26 + 0 to 40 + 6 weeks of gestation; birth weight 660-4,460 g). A correlation of S' values with established tricuspid annular plane systolic excursion (TAPSE) values was performed. RESULTS: The S' ranged from a mean of 4.5 cm/s (Z-score ± 2 SD: 3.6-5.5 cm/s) in preterm neonates in week 26(0-6) of gestation to 7.8 cm/s (Z-score ± 2 SD: 5.5-10.1 cm/s) in term neonates in week 40(0-6) of gestation. The S' values increased from 26 to 40 weeks of gestation. S' and week of gestation are strongly correlated: Pearson's correlation coefficient was 0.66 for week of gestation - S' (p < 0.001). A significant correlation was found between S' and TAPSE values (r = 0.67; p < 0.001). CONCLUSION: Z-scores of S' values were calculated and percentile charts were established to serve as reference data for preterm and term neonates with structurally normal hearts.

Cerebral and peripheral regional oxygen saturation during postnatal transition in preterm neonates.

OBJECTIVE: To evaluate peripheral regional oxygen saturation (rpSO2) and cerebral regional oxygen saturation (rcSO2) during the immediate postnatal transition in late preterm infants with and without the need for respiratory support. STUDY DESIGN: This was a prospective observational study using near-infrared spectroscopy to evaluate changes in rpSO2 and rcSO2. These variables were measured during the first 15 minutes of life after elective cesarean delivery. Peripheral oxygen saturation (SpO2) and heart rate were measured continuously by pulse oximetry, and cerebral fractional tissue oxygen extraction (cFTOE) was calculated. Two groups were compared based on their need for respiratory support: a respiratory support group and a normal transition group. Positive-pressure ventilation was delivered with a T-piece resuscitator, and oxygen was adjusted based on SpO2 values. A Florian respiratory function monitor was used to record the ventilation variables. RESULTS: There were 21 infants in the normal transition group and 21 infants in the respiratory support group. Changes in heart rate over time were similar in the 2 groups. SpO2, rcSO2, and rpSO2 values were consistently higher in the normal transition group. In the respiratory support group, cFTOE values remained significantly elevated for a longer period. CONCLUSION: This systematic analysis of rpSO2, rcSO2, and cFTOE in late preterm infants found significantly lower oxygen saturation values in infants who received respiratory support compared with a normal transition group. We hypothesize that the elevated cFTOE values in the respiratory support group represent compensation for lower oxygen delivery.

aEEG and NIRS during transition and resuscitation after birth: promising additional tools; an observational study.

AIM OF THE STUDY: During resuscitation no routine cerebral monitoring is available. We aimed at monitoring cerebral activity and oxygenation continuously during neonatal transition and resuscitation. METHODS: Neonates ≥34 weeks of gestation born via cesarean section were included. Cerebral activity was continuously measured with amplitude-integrated-EEG (aEEG) and cerebral oxygenation (rSO2) with near-infrared-spectroscopy (NIRS) during the first 10 min after birth. For quantitative analysis of aEEG every minute the mean minimum amplitude (V(min)) and maximum amplitude (V(max)) was determined. Uncompromised neonates were compared to neonates in need of resuscitation. RESULTS: Out of 224 eligible neonates 31 uncompromised and 15 in need of respiratory support were included. Uncompromised neonates showed higher values for V(min) in the third minute and higher values for V(max) in the third and fourth minute compared to the tenth minute post-partum. In uncompromised neonates rSO2 values during the first 6 min after birth were lower compared to minute ten. Neonates in need of respiratory support had lower rSO2 values over the first 8 min after birth compared to minute ten. CONCLUSIONS: This is the first study demonstrating that monitoring of aEEG and NIRS to measure cerebral activity and oxygenation during immediate postpartum transition is feasible. During transition compromised neonates requiring resuscitation showed a different cerebral activity pattern compared to uncompromised neonates.