Guidelines for blood sampling and measurement of pH and blood gas values in obstetrics. Based upon a workshop held in Zurich, Switzerland, March 19, 1993 by an Ad Hoc Committee

Acid base and metabolic parameters of the umbilical cord blood and cerebral oxygenation immediately after birth

Objective

Aim was to investigate whether acid-base and metabolic parameters obtained from arterial umbilical cord blood affect cerebral oxygenation after birth in preterm neonates with respiratory support and in term neonates without respiratory support.

Study design

This was a post-hoc analysis of secondary outcome parameters of a prospective observational study including preterm neonates with and term neonates without respiratory support. Non-asphyxiated neonates with cerebral oxygenation measured with near-infrared spectroscopy during the first 15 min and with blood gas analyses from arterial umbilical cord blood were included. Arterial oxygen saturation (SpO2) and heart rate (HR) were monitored with pulse oximetry. Potential correlations were investigated between acid-base and metabolic parameters (pH-value, bicarbonate, base-excess, and lactate) and crSO2/cFTOE 5 min after birth.

Results

Seventy-seven neonates were included: 14 preterm neonates with respiratory support (mean gestational age [GA] 31.4 ± 4.1 weeks; mean birth weight [BW] 1,690 ± 640 g) and 63 term neonates without respiratory support (GA 38.7 ± 0.8 weeks; BW 3,258 ± 443 g). Mean crSO2 5 min after birth was 44.0% ± 24.2% in preterm and 62.2% ± 20.01% in term neonates. Mean cFTOE 5 min after birth was 0.46 ± 0.06 in preterm and 0.27 ± 0.19 in term neonates. In preterm neonates with respiratory support higher lactate was significantly associated with lower crSO2 and SpO2 and tended to be associated with higher cFTOE. In term neonates without respiratory support no significant correlations were found.

Conclusion

In non-asphyxiated preterm neonates with respiratory support, lactate levels were negatively associated with crSO2 and SpO2, whereas in term neonates without respiratory support no associations were observed.

Acid-base and metabolic parameters and cerebral oxygenation during the immediate transition after birth-A two-center observational study

OBJECTIVE

The association between blood glucose level and cerebral oxygenation (cerebral regional oxygen saturation [crSO2] and cerebral fractional tissue oxygen extraction [FTOE]) in neonates has already been described. Aim of the present study was to investigate if acid-base and other metabolic parameters have an impact on cerebral oxygenation immediately after birth in preterm and term neonates.

STUDY DESIGN

Post-hoc analyses of secondary outcome parameters of two prospective observational studies were performed. Preterm and term neonates born by caesarean section were included, in whom i) cerebral near-infrared spectroscopy (NIRS) measurements were performed during the first 15 minutes after birth and ii) a capillary blood gas analysis was performed between 10 and 20 minutes after birth. Vital signs were routinely monitored with pulse oximetry (arterial oxygen saturation [SpO2] and heart rate [HR]). Correlation analyses were performed to investigate potential associations between acid-base and metabolic parameters (lactate [LAC], pH-value [pH], base-excess [BE] and bicarbonate [HCO3]) from capillary blood and NIRS-derived crSO2 and FTOE at 15 minutes after birth.

RESULTS

One-hundred-fifty-seven neonates, 42 preterm neonates (median gestational age [IQR] 34.0 weeks [3.3], median birth weight 1845g [592]) and 115 term neonates (median gestational age [IQR] 38.9 weeks [1.0], median birth weight 3230g [570]) were included in the study. Median crSO2 [IQR] values at 15 minutes after birth were 82% [16] in preterm neonates and 83% [12] in term neonates. Median FTOE [IQR] values at 15 minutes after birth were 0.13 [0.15] in preterm neonates and 0.14 [0.14] in term neonates. In preterm neonates, higher LAC and lower pH and BE were associated with lower crSO2 and higher FTOE. In term neonates, higher HCO3 was associated with higher FTOE.

CONCLUSION

There were significant associations between several acid-base and metabolic parameters and cerebral oxygenation in preterm neonates, while in term neonates only HCO3 correlated positively with FTOE.

Development of blood hemoglobin level early detection device based on a noninvasive optical platform

Blood hemoglobin levels are a reliable indicator for anemia screening, which generally uses an invasive system or takes blood using a syringe. Spectrophotometry can work by “substituting” the use of a phlebotomy tube needle with electromagnetic wave radiation or light. This study aims to develop and carry out a noninvasive diagnostic test for measuring hemoglobin levels. There are three main stages in this research: (i) measuring hemoglobin concentration and scanning an incident wavelength on standard hemoglobin solutions and blood controls, (ii) making a prototype variant of a noninvasive blood hemoglobin level measurement device, and (iii) testing the technology unit on the developed prototype. The measured hemoglobin value by the Trax Control Meter for low, middle, and high levels is almost the same as the expected range values, namely, 13.09, 16.8, and 17.81 g/dL, respectively. Three sets of device prototype variants were successfully developed: (i) the noninvasive blood hemoglobin level measuring device based on Raspberry Pi Prototype on Infant Finger and Thigh Probes, (ii) the level measuring prototype noninvasive hemoglobin in blood based on Internet of Things and WebServer, and (iii) the prototype of noninvasive blood hemoglobin level measuring device on in vitro probe with reflectance method. Testing the accuracy of the Biorad MeterTrax Trilevel using a multiformula regression calculation using the ZunZun server shows that the tool has an accuracy ranging from 0.12 to 0.30 g/dL.

Non-linear Methods Predominant in Fetal Heart Rate Analysis: A Systematic Review

The analysis of fetal heart rate variability has served as a scientific and diagnostic tool to quantify cardiac activity fluctuations, being good indicators of fetal well-being. Many mathematical analyses were proposed to evaluate fetal heart rate variability. We focused on non-linear analysis based on concepts of chaos, fractality, and complexity: entropies, compression, fractal analysis, and wavelets. These methods have been successfully applied in the signal processing phase and increase knowledge about cardiovascular dynamics in healthy and pathological fetuses. This review summarizes those methods and investigates how non-linear measures are related to each paper's research objectives. Of the 388 articles obtained in the PubMed/Medline database and of the 421 articles in the Web of Science database, 270 articles were included in the review after all exclusion criteria were applied. While approximate entropy is the most used method in classification papers, in signal processing, the most used non-linear method was Daubechies wavelets. The top five primary research objectives covered by the selected papers were detection of signal processing, hypoxia, maturation or gestational age, intrauterine growth restriction, and fetal distress. This review shows that non-linear indices can be used to assess numerous prenatal conditions. However, they are not yet applied in clinical practice due to some critical concerns. Some studies show that the combination of several linear and non-linear indices would be ideal for improving the analysis of the fetus's well-being. Future studies should narrow the research question so a meta-analysis could be performed, probing the indices' performance.

Reference percentiles for paired arterial and venous umbilical cord blood gases: An indirect nonparametric approach

BACKGROUND

Reference intervals for arterial and venous umbilical cord blood gas (UCBG) parameters are scarce, are mainly focused on pH, pO2, pCO2 and base deficit, and are usually assessed using parametric tests, despite a generally skewed data distribution. Here, the purpose is to determine reference percentiles for nine parameters of concomitant arterial and venous UCBG (CAV-UCBG) from neonates at birth, using nonparametric tests.

METHODS

Results of CAV-UCBG, assayed over a 4.5-year period, were extracted from a hospital laboratory database for pH, pCO2, pO2, oxygen saturation, concentration of total oxygen, total carbon dioxide, hydrogen carbonate, total haemoglobin, and acid-base excess. Exclusion criteria were: a venous-arterial pH difference <0.02, an arterial-venous pCO2 <0.7 kPa, and a venous pCO2 <2.9 kPa. Nonparametric bivariate kernel density estimations were used for the selection of plots within the 95% percentile surface of the pCO2-to-pH relationship (NBKDE-95P). Outliers from skewed data were removed using an adjusted-Tukey method, and percentiles were calculated according to the CLSI EP28-A3 nonparametric method.

RESULTS

Overall, 31% (5033/16164) of CAV-UCBG were discarded using the three exclusion criteria. Then, 6% (670/11131) of CAV-UCBG were excluded from the NBKDE-95P, and 0.1 to 3.5% outliers were subsequently removed. Depending on the parameter, the 2.5th and 97.5th percentiles from the whole group were similar or slightly narrower compared to reference intervals from other studies, while those from female and male neonates did not differ substantially.

CONCLUSIONS

Using an indirect nonparametric approach, this study proposes new percentiles for parameters from concomitant arterial and venous umbilical cord blood gases.

Effect of intrapartum fetal stress associated with obstetrical interventions on viability and survivability of canine neonates

Aim:

This study was conducted with the objective of identifying and evaluating intrapartum fetal stress in connection with the type of delivery in bitches.

Materials and Methods:

A total of 26 bitches between 1 and 5 years, belonging to 10 different breeds were evaluated. Bitches were subjected to detailed clinico-gynecological examination based on history. Neonatal stress associated with spontaneous whelping (SW), assisted whelping (AW), and emergency cesarean section (EC) was evaluated using umbilical vein lactate (UL) estimation by collecting the blood from umbilical vein.

Results:

A high umbilical vein lactate value was associated with fetal distress. The mean umbilical lactate value was highest in EC (12.54±0.8 mmol/L) followed by AW (8.86±0.9 mmol/L) and the lowest value was found in SW (7.56±0.58 mmol/L). A significant increase (p<0.05) in umbilical lactate level was observed in EC group of canine neonates compared with AW and SW groups. Overall mean umbilical lactate values of neonates which died within 24 h (13.31±1.08 mmol/L) and the neonates which survived beyond 24 h (8.87±0.55 mmol/L) differed significantly at 5% level.

Conclusion:

Immediate identification of neonatal distress by use of umbilical vein lactate estimation is helpful for the clinician to undertake resuscitation or medical therapy to ensure better neonatal survivability.

Craniofacial tissue oxygen saturation is associated with blood pH using an examiner's finger-mounted tissue oximetry in mice

Although fetal scalp blood sampling is an examination to assess fetal acidosis during the intrapartum period, it has not been widely used by obstetricians because of its invasiveness. We have developed a small, portable oximetry with a sensor attached to the examiner's finger. Our previous report using this oximetry concluded that fetal head tissue oxygen saturation (StO 2 StO2 ) correlated with umbilical cord artery blood pH. We investigated whether the association between StO 2 StO2 and blood pH in mice could be validated using this oximetry. Eleven the Institute for Cancer Research (ICR) mice were measured using a near-infrared spectroscopy probe at the craniofacial site in a closed polyethylene bag while changing the oxygen concentration. A total of nine blood samples were collected and analyzed for pH. The StO 2 StO2 and tissue blood pH showed a strong positive correlation (r=0.90 r=0.90 and P=0.0009 P=0.0009 ). The StO 2 StO2 and total hemoglobin index also showed a positive correlation (r=0.84 r=0.84 and P=0.0049 P=0.0049 ). Thus, the results of the present study support those of our previous report on clinical cases and allow examiners to easily check the status of fetal acidosis. Fetal management using this oximetry might gain popularity with obstetricians in the near future.

How an extended perinatal audit may improve perinatal policy

Abstract Objective: A perinatal audit has the intention of quality of care improvement based on analysis of perinatal death, with our without analysis of maternal morbidity and/or mortality. Additional analysis of cases of intrapartum asphyxia could provide more insight into ways to improve quality of perinatal care. Methods: Analysis of cases of perinatal death and asphyxia in Jan Yperman Hospital, Ieper, Belgium, in 2012. Results: Three perinatal deaths occurred, none were preventable. Nineteen cases of proven metabolic acidosis have been identified. Three cases are considered possibly preventable, four cases are considered preventable. In three (possibly) preventable cases, foetal monitoring was absent during the active second stage of labour. In two preventable cases, intervention following a significant ST event in the second stage of labour was delayed. In one case intervention was delayed in the first stage of labour, while in another, indicated operative delivery in the second stage was not conducted. Conclusions: Integrating intrapartum asphyxia in the perinatal audit gives an opportunity to identify and eliminate weak points in the perinatal care chain, thereby optimizing quality of care. Lessons learned from our internal audit are the value of foetal monitoring and adequate action on significant ST events during second stage of labour.

Nursing and midwifery management of hypoglycaemia in healthy term neonates

EXECUTIVE SUMMARY:

OBJECTIVES

The primary objective of this review was to determine the best available evidence for maintenance of euglycaemia* in healthy term neonates, and the management of asymptomatic hypoglycaemia in otherwise healthy term neonates.

INCLUSION CRITERIA

TYPES OF STUDIES: The review included any relevant published or unpublished studies undertaken between 1995 and 2004. Studies that focus on the diagnostic accuracy of point-of-care devices for blood glucose screening and/or monitoring in the neonate were initially included as a subgroup of this review. However, the technical nature and complexity of the statistical information published in diagnostic studies retrieved during the literature search stage, as well as the considerable volume of published research in this area, suggested that it would be more feasible to analyse diagnostic studies in a separate systematic review.

TYPES OF PARTICIPANTS

The review focused on studies that included healthy term (37- to 42-week gestation) appropriate size for gestational age neonates in the first 72 h after birth.

EXCLUSIONS

•  preterm or small for gestational age newborns; •  term neonates with a diagnosed medical or surgical condition, congenital or otherwise; •  babies of diabetic mothers; •  neonates with symptomatic hypoglycaemia; •  large for gestational age neonates (as significant proportion are of diabetic mothers). TYPES OF INTERVENTION: All interventions that fell within the scope of practice of a midwife/nurse were included: •  type (breast or breast milk substitutes), amount and/or timing of feeds, for example, initiation of feeding, and frequency; •  regulation of body temperature; •  monitoring (including screening) of neonates, including blood or plasma glucose levels and signs and symptoms of hypoglycaemia. Interventions that required initiation by a medical practitioner were excluded from the review.

TYPES OF OUTCOME MEASURES

Outcomes that were of interest included: •  occurrence of hypoglycaemia; •  re-establishment and maintenance of blood or plasma glucose levels at or above set threshold (as defined by the particular study); •  successful breast-feeding; •  developmental outcomes. TYPES OF RESEARCH DESIGNS: The review initially focused on randomised controlled trials reported from 1995 to 2004. Insufficient randomised controlled trials were identified and the review was expanded to include additional cohort and cross-sectional studies for possible inclusion in a narrative summary.

SEARCH STRATEGY

The major electronic databases, including MEDLINE/PubMed, CINAHL, EMBASE, LILACS, Cochrane Library, etc., were searched using accepted search techniques to identify relevant published and unpublished studies undertaken between 1995 and 2004. Efforts were made to locate any relevant unpublished materials, such as conference papers, research reports and dissertations. Printed journals were hand-searched and reference lists checked for potentially useful research. The year 1995 was selected as the starting point in order to identify any research that had not been included in the World Health Organisation review, which covered literature published up to 1996. The search was not limited to English language studies. ASSESSMENT OF QUALITY: Three primary reviewers conducted the review assisted by a review panel. The review panel was comprised of nine nurses with expertise in neonatal care drawn from senior staff in several metropolitan neonatal units and education programs. Authorship of journal articles was not concealed from the reviewers. Methodological quality of each study that met the inclusion criteria was assessed by two reviewers, using a quality assessment checklist developed for the review. Disagreements between reviewers were resolved through discussion or with the assistance of a third reviewer.

DATA EXTRACTION AND ANALYSIS

Two reviewers used a data extraction form to independently extract data relating to the study design, setting and participants; study focus and intervention(s); and measurements and outcomes. As only one relevant randomised controlled trial was found, a meta-analysis could not be conducted nor tables constructed to illustrate comparisons between studies. Instead, the findings were summarised by a narrative identifying any relevant findings that emerged from the data.

RESULTS

Seven studies met the inclusion criteria for the objective of this systematic review. The review provided information on the effectiveness of three categories of intervention - type of feeds, timing of feeds and thermoregulation on two of the outcome measures identified in the review protocol - prevention of hypoglycaemia, and re-establishment and maintenance of blood or plasma glucose levels above the set threshold (as determined by the particular study). There was no evidence available on which to base conclusions for effectiveness of monitoring or developmental outcomes, and insufficient evidence for breast-feeding success. Given that only a narrative review was possible, the findings of this review should be interpreted with caution. The findings suggest that the incidence of hypoglycaemia in healthy, breast-fed term infants of appropriate size for gestational age is uncommon and routine screening of these infants is not indicated. The method and timing of early feeding has little or no influence on the neonatal blood glucose measurement at 1 h in normal term babies. In healthy, breast-fed term infants the initiation and timing of feeds in the first 6 h of life has no significant influence on plasma glucose levels. The colostrum of primiparous mothers provides sufficient nutrition for the infant in the first 24 h after birth, and supplemental feeds or extra water is unnecessary. Skin-to-skin contact appears to provide an optimal environment for fetal to neonatal adaptation after birth and can help to maintain body temperature and adequate blood glucose levels in healthy term newborn infants, as well as providing an ideal opportunity to establish early bonding behaviours.

IMPLICATIONS FOR PRACTICE

The seven studies analysed in this review confirm the World Health Organisation's first three recommendations for prevention and management of asymptomatic hypoglycaemia, namely: 1 Early and exclusive breast-feeding is safe to meet the nutritional needs of healthy term newborns worldwide. 2 Healthy term newborns that are breast-fed on demand need not have their blood glucose routinely checked and need no supplementary foods or fluids. 3 Healthy term newborns do not develop 'symptomatic' hypoglycaemia as a result of simple underfeeding. If an infant develops signs suggesting hypoglycaemia, look for an underlying condition. Detection and treatment of the cause are as important as correction of the blood glucose level. If there are any concerns that the newborn infant might be hypoglycaemic it should be given another feed. Given the importance of thermoregulation, skin-to-skin contact should be promoted and 'kangaroo care' encouraged in the first 24 h after birth. While it is important to main the infant's body temperature care should be taken to ensure that the child does not become overheated.

Re-evaluation of cord blood arterial and venous reference ranges for pH, pO(2), pCO(2), according to spontaneous or cesarean delivery

Umbilical cord blood gas analysis (pO(2) and pCO(2)) is now recommended in all high-risk baby deliveries and in some centers it is performed routinely following all deliveries. The aim of this study was to re-evaluate cord blood arterial and venous reference ranges for pH, pO(2), pCO(2) in newborns, delivered by spontaneous vaginal delivery (SVD) and by cesarean section (CS) performed in Faculty Hospital Motol. Two groups of subjects were selected for the study. Group I consisted of 303 newborns with SVD. Group II consisted of 189 newborns delivered by cesarean section. Cord blood samples were analyzed for standard blood gas and pH, using the analytical device Rapid Lab 845 and Rapid Lab 865. We obtained reference values expressed as range (lower and upper reference value expressed as 2.5 and 97.5 percentiles) for cord blood in newborns with SVD: arterial cord blood: pH=7.01-7.39; pCO(2)=4.12-11.45 kPa; pO(2)=1.49-5.06 kPa; venous cord blood: pH=7.06-7.44; pCO(2)=3.33-9.85 kPa; pO(2)=1.80-6.29 kPa. We also obtained reference values for cord blood in newborns delivered by CS: arterial cord blood: pH=7.05-7.39; pCO(2)=5.01-10.60 kPa; pO(2)=1.17-5.94 kPa; venous cord blood: pH=7.10-7.42; pCO(2)=3.88-9.36 kPa; pO(2)=1.98-7.23 kPa. Re-evaluated reference ranges play essential role in monitoring conditions of newborns with spontaneous and caesarean delivery.

Evaluation of newborn canine viability by means of umbilical vein lactate measurement, apgar score and uterine tocodynamometry

Newborn viability evaluation and early detection of fetal distress could contribute to reducing mortality at birth in canine species. High neonatal mortality rate in dogs is reported subsequent to complicated or uncomplicated whelping. Umbilical vein lactate and tocodynamometry could provide valuable clinical information to the obstetricians so that appropriate medical and surgical treatments or oxygen and warm administration can be properly and timely applied to mother and newborn pup. In humans, the fetal lactate level represents an objective indicator of fetal distress and a valid predictor of babies' survival. Fetal acidosis recognition by umbilical lactate (UL) measurement, APGAR score classification, and uterine activity monitoring during labour, can represent an advanced system in the evaluation of the canine newborn patient. The purpose of this study was to correlate UL levels with canine neonatal morbidity and mortality within 48 h of birth. We evaluated the relationship among neonatal parameters at birth (mucous membrane color, heart and respiratory rate, reflex irritability, mobility, suckling and vocalization, UL, weight, and temperature) with labour characteristics (uterine contractions recorded by the tocodynamometric system of Whelpwise ™ Veterinary Perinatal Specialties ®, delivery time, and pup presentation), in view to predict pup viability. We considered also vaginal parturition versus elective and emergency Caesarean section, and uterotonic drugs influence on delivery. Umbilical lactate concentration proved to be useful to predict canine neonatal mortality within 48 h of birth (P < 0.05). We identified 5 mmol/L of vein umbilical lactate concentration as the cut off value, allowing us to distinguish between healthy and distressed pups. Higher values of UL were related with distressed pups, whereas lower values characterized vigorous pups. Lactate concentrations lower than 5 mmol/L and APGAR scores higher than 9, related to mean delivery time of 105 min with effective uterine contractions (10 mm of Hg of strength or more, frequency from 4 to 12 contractions per hour, and 2-5 min in duration), should be considered good prognostic factors in canine labour and neonatology.

Access to computerised analysis of intrapartum cardiotocographs improves clinicians' prediction of newborn umbilical artery blood pH

OBJECTIVE

To evaluate the impact of access to computerised cardiotocograph (CTG) analysis on reproducibility and accuracy of clinicians' predictions of umbilical artery blood pH (UAB pH) and 5-minute Apgar score.

DESIGN

Prospective evaluation of pre-recorded cases.

SETTING

A tertiary-care university hospital.

POPULATION

From databases of intrapartum CTGs acquired in singleton term pregnancies, 204 tracings with low signal loss and short time interval to delivery were consecutively selected.

METHODS

Tracings were randomly assigned to computer analysis by the Omniview-SisPorto 3.5 system (study group n = 104) or to no analysis (control group n = 100). Three experienced clinicians evaluated all tracing printouts independently and were asked to predict the newborns' UAB pH and 5-minute Apgar scores from them.

MAIN OUTCOME MEASURES

Interobserver agreement (measured by the intraclass correlation coefficient [ICC]) and accuracy in prediction of neonatal outcomes with 95% CI.

RESULTS

Agreement on prediction of UAB pH was significantly higher in the study group (ICC = 0.70; 95% CI 0.61-0.77) than in the control group (ICC = 0.43; 95% CI 0.21-0.60), and a trend towards better agreement was also seen in estimation of 5-minute Apgar scores (ICC = 0.55; 95% CI 0.38-0.68 versus ICC = 0.43; 95% CI 0.25-0.57). Observers predicted UAB pH values correctly within a 0.10 margin in 70% of cases in the study group (95% CI 0.61-0.79) versus 46% in the control group (95% CI 0.35-0.56). They predicted 5-minute Apgar scores within a margin of one in 81% of cases in the study group (95% CI 0.73-0.88) and in 70% of cases in the control group (95% CI 0.61-0.79).

CONCLUSIONS

Prediction of UAB pH is more reproducible and accurate when clinicians have access to computerised analysis of CTGs.

Prediction of neonatal acidemia by computer analysis of fetal heart rate and ST event signals

OBJECTIVE

The objective of the study was to evaluate the accuracy of computer analysis of fetal heart rate (FHR) and ST event signals in prediction of neonatal acidemia.

STUDY DESIGN

One hundred forty-eight FHR tracings were evaluated to identify red alerts provided by the system, based on automated analysis of FHR and ST event signals, and compared with the occurrence of umbilical artery acidemia (pH < or =7.05).

RESULTS

The presence of red alerts obtained sensitivity of 1.00 (95% confidence interval [CI], 0.56-1.00), specificity of 0.94 (95% CI, 0.89-0.97), positive predictive value (PPV) of 0.47 (95% CI, 0.22-0.72), negative predictive value (NPV) of 1 (95% CI, 0.96-1.00), positive likelihood ratio (PLR) of 17.6 (95% CI, 9.0-34.5), and negative likelihood ratio (NLR) of 0. When limiting analysis to red alerts that did not include ST data, sensitivity was 0.57 (95% CI, 0.20-0.88), specificity was 0.97 (95% CI, 0.92-0.99), PPV was 0.50 (95% CI, 0.17-0.82), NPV was 0.98 (95% CI, 0.93-0.99), PLR was 20.14 (95% CI, 6.3-64.2), and NLR was 0.44 (95% CI, 0.19-1.04).

CONCLUSION

Computer analysis of FHR and ST event signals provide higher accuracy in predicting neonatal academia.

Umbilical cord blood lactate: a valuable tool in the assessment of fetal metabolic acidosis

OBJECTIVE

The aim of the present study was (1) to evaluate the relationship between umbilical cord arterial blood lactate and pH, standard base excess (SBE), and actual base excess (ABE) at delivery and (2) to suggest a cut-off level of umbilical cord arterial blood lactate in predicting fetal asphyxia using ROC-curves, where an ABE value less than -12 was used as "gold standard" for significant intrapartum asphyxia.

STUDY DESIGN

This is a descriptive study of umbilical cord arterial blood samples from 2554 singleton deliveries. The deliveries took place at the Department of Obstetrics and Gynaecology, Hvidovre University Hospital, Copenhagen, Denmark where umbilical cord blood sampling and blood gas analysis is part of the routine assessment of all newborns.

RESULTS

We found significant correlations between lactate and pH (r=-0.73), lactate and SBE (r=-0.76), and lactate and ABE (r=-0.83). ROC-curves suggested a lactate cut-off level of 8mmol/l for indicating intrapartum asphyxia.

CONCLUSION

Lactate in arterial umbilical cord blood might be a more direct and accordingly more correct indicator of fetal asphyxia at delivery than pH and SBE (or ABE). Its potential as a predictor of neonatal outcome needs to be evaluated in future studies.

Determinants of the middle cerebral artery peak systolic velocity in the human fetus

OBJECTIVE

The purpose of this study was to identify physiologic determinants of the peak systolic blood flow velocity (PSV) of the middle cerebral artery (MCA) in the human fetus.

STUDY DESIGN

MCA PSV was measured with pulsed wave Doppler ultrasound in human fetuses who underwent cordocentesis. Hemoglobin, hematocrit, and blood gas values were analyzed from umbilical venous blood, and the data were normalized for gestational age. Total oxygen content of fetal venous blood was calculated from oxygen saturation, hemoglobin value, and pO2. Correlation and logistic regression analyses were performed to identify primary physiologic determinants of MCA PSV.

RESULTS

In 136 fetuses who underwent cordocentesis (predominantly for alloimmune disease), hematocrit, hemoglobin, and blood oxygen content correlated significantly with the MCA PSV (P < .01). Logistic regression modeling demonstrated that fetal hemoglobin content (odds ratio, 7.1; 95% CI, 3.71-13.7) and pCO2, but not pO2 or fetal blood oxygen content, accounted for increases in MCA PSV.

CONCLUSION

Under physiologic circumstances, fetal hemoglobin, and not fetal oxygenation, primarily determines the middle cerebral artery peak systolic velocity.

Prediction of neonatal state by computer analysis of fetal heart rate tracings: the antepartum arm of the SisPorto® multicentre validation study

OBJECTIVE

To evaluate the capacity of computer analysis of antepartum cardiotocographs performed by SisPorto 2.0 in predicting neonatal outcome.

STUDY DESIGN

A prospective observational study was conducted in eight tertiary care centres in Europe and Australia, involving pregnant women in the absence of labor, scheduled for elective caesarean section, whose last fetal heart rate (FHR) tracing was performed within 4h of delivery. After exclusion of fetal malformations, multiple pregnancies, tracings with less than 30 min, tracings with more than 15% signal loss, difficult fetal extractions, and anesthesia complications, a total of 345 cases were analyzed. Computer quantification of cardiotocographic parameters was compared with newborn Apgar score, umbilical artery pH, metabolic acidosis and neonatal hypoxic-ischemic encephalopathy, by means of receiver operating characteristic (ROC) curves.

RESULTS

Acceleration number, mean short-term variability, percentage of abnormal short-term variability and percentage of abnormal long-term variability had an excellent discriminative capacity to predict 1-min Apgar scores under or equal to 4 (areas under the ROC curve 0.96-1.00). The same parameters showed a slightly lower capacity to predict 5-min Apgar scores under or equal to 6 (areas under the ROC curve 0.81-0.89). The best cut-off values for these parameters, derived from the previously referred calculations, detected all cases of hypoxic-ischemic encephalopathy (n = 2). Cardiotocographic parameters showed a lower discriminative capacity in prediction of umbilical artery pH <7.20 (maximum area under the ROC curve 0.66) and <7.15 (maximum area under the ROC curve 0.69).

CONCLUSIONS

Computerized quantification of accelerations and variability in the antepartum allows a good prediction of 1 and 5-min Apgar scores, and to a much lesser degree umbilical artery pH.

Nursing and midwifery management of hypoglycaemia in healthy term neonates

OBJECTIVES

The primary objective of this review was to determine the best available evidence for maintenance of euglycaemia in healthy term neonates, and the management of asymptomatic hypoglycaemia in otherwise healthy term neonates.

INCLUSION CRITERIA

The review included any relevant published or unpublished studies undertaken between 1995 and 2004. Studies that focus on the diagnostic accuracy of point-of-care devices for blood glucose screening and/or monitoring in the neonate were initially included as a subgroup of this review. However, the technical nature and complexity of the statistical information published in diagnostic studies retrieved during the literature search stage, as well as the considerable volume of published research in this area, suggested that it would be more feasible to analyse diagnostic studies in a separate systematic review.The review focused on studies that included healthy term (37- to 42-week gestation) appropriate size for gestational age neonates in the first 72 h after birth.All interventions that fell within the scope of practice of a midwife/nurse were included:Interventions that required initiation by a medical practitioner were excluded from the review.Outcomes that were of interest included:The review initially focused on randomised controlled trials reported from 1995 to 2004. Insufficient randomised controlled trials were identified and the review was expanded to include additional cohort and cross-sectional studies for possible inclusion in a narrative summary.

SEARCH STRATEGY

The major electronic databases, including MEDLINE/PubMed, CINAHL, EMBASE, LILACS, Cochrane Library, etc., were searched using accepted search techniques to identify relevant published and unpublished studies undertaken between 1995 and 2004. Efforts were made to locate any relevant unpublished materials, such as conference papers, research reports and dissertations. Printed journals were hand-searched and reference lists checked for potentially useful research. The year 1995 was selected as the starting point in order to identify any research that had not been included in the World Health Organisation review, which covered literature published up to 1996. The search was not limited to English language studies.

ASSESSMENT OF QUALITY

Three primary reviewers conducted the review assisted by a review panel. The review panel was comprised of nine nurses with expertise in neonatal care drawn from senior staff in several metropolitan neonatal units and education programs. Authorship of journal articles was not concealed from the reviewers. Methodological quality of each study that met the inclusion criteria was assessed by two reviewers, using a quality assessment checklist developed for the review. Disagreements between reviewers were resolved through discussion or with the assistance of a third reviewer.

DATA EXTRACTION AND ANALYSIS

Two reviewers used a data extraction form to independently extract data relating to the study design, setting and participants; study focus and intervention(s); and measurements and outcomes.As only one relevant randomised controlled trial was found, a meta-analysis could not be conducted nor tables constructed to illustrate comparisons between studies. Instead, the findings were summarised by a narrative identifying any relevant findings that emerged from the data.

RESULTS

Seven studies met the inclusion criteria for the objective of this systematic review. The review provided information on the effectiveness of three categories of intervention - type of feeds, timing of feeds and thermoregulation on two of the outcome measures identified in the review protocol - prevention of hypoglycaemia, and re-establishment and maintenance of blood or plasma glucose levels above the set threshold (as determined by the particular study). There was no evidence available on which to base conclusions for effectiveness of monitoring or developmental outcomes, and insufficient evidence for breast-feeding success.Given that only a narrative review was possible, the findings of this review should be interpreted with caution. The findings suggest that the incidence of hypoglycaemia in healthy, breast-fed term infants of appropriate size for gestational age is uncommon and routine screening of these infants is not indicated. The method and timing of early feeding has little or no influence on the neonatal blood glucose measurement at 1 h in normal term babies. In healthy, breast-fed term infants the initiation and timing of feeds in the first 6 h of life has no significant influence on plasma glucose levels. The colostrum of primiparous mothers provides sufficient nutrition for the infant in the first 24 h after birth, and supplemental feeds or extra water is unnecessary.Skin-to-skin contact appears to provide an optimal environment for fetal to neonatal adaptation after birth and can help to maintain body temperature and adequate blood glucose levels in healthy term newborn infants, as well as providing an ideal opportunity to establish early bonding behaviours.

IMPLICATIONS FOR PRACTICE

The seven studies analysed in this review confirm the World Health Organisation's first three recommendations for prevention and management of asymptomatic hypoglycaemia, namely:1 Early and exclusive breast-feeding is safe to meet the nutritional needs of healthy term newborns worldwide.2 Healthy term newborns that are breast-fed on demand need not have their blood glucose routinely checked and need no supplementary foods or fluids.3 Healthy term newborns do not develop 'symptomatic' hypoglycaemia as a result of simple underfeeding. If an infant develops signs suggesting hypoglycaemia, look for an underlying condition. Detection and treatment of the cause are as important as correction of the blood glucose level.If there are any concerns that the newborn infant might be hypoglycaemic it should be given another feed. Given the importance of thermoregulation, skin-to-skin contact should be promoted and 'kangaroo care' encouraged in the first 24 h after birth. While it is important to main the infant's body temperature care should be taken to ensure that the child does not become overheated.

Intrapartum management of nonreassuring fetal heart rate patterns: a randomized controlled trial of fetal pulse oximetry

OBJECTIVE

We tested if fetal pulse oximetry in addition to electronic fetal monitoring (CTG) and scalp blood sampling improves the accuracy of fetal assessment and allows safe reduction of operative deliveries (-50%) and scalp blood sampling (-50%) performed because of nonreassuring fetal status. Study design A randomized controlled trial was conducted in 146 patients with term pregnancies in active labor and abnormal fetal heart rate patterns: 73 had electronic fetal heart rate monitoring (CTG) and fetal scalp blood sampling (control group), 73 had CTG, fetal scalp blood sampling, and continuous fetal pulse oximetry (study group).

RESULTS

There was a reduction of -50% in operative deliveries and fetal scalp blood sampling performed because of nonreassuring fetal status in the study group: operative deliveries, study versus control 25/49 (P </= .001); fetal scalp sampling, study versus control 32/64 (P </= .001). An increase in cesarean sections because of dystocia in the study group did not change the net number of operative deliveries. There was no difference between the 2 groups in adverse maternal or neonatal outcomes, as well as for the end points of metabolic acidosis and need for resuscitation.

CONCLUSION

There was a safe reduction in operative deliveries (-50%) and scalp blood sampling (-50%) performed because of nonreassuring fetal status. The increase in cesarean sections because of dystocia in the study group was a well-documented arrest of labor, but it did not change the total number of operative deliveries in this group.

The merit of routine cord blood pH measurement at birth

We searched the literature for mean values of arterial cord blood pH at birth and their lower limits of statistical normality. An arterial cord blood pH, correctly sampled, measured, validated, and interpreted, provides the most objective and sensitive index for fetal hypoxemia during labor. We advise to sample both artery and vein from a clamped segment of the cord within 30 minutes after birth. In accordance with physiological and statistical evidence, it is proposed to classify arterial cord blood pH in three categories: normal (when > 7.11), abnormal (when < 6.99), and borderline (7.00-7.11). An abnormal pH indicates that the fetus was in a state of biochemical decompensation at birth. Disadvantages of routine measurement include extra work load and the lack of a universally agreed definition of normal or abnormal pH. The major advantage of routine measurement is to provide care-givers with immediate feedback on their care during childbirth and an opportunity to learn from that feedback.

Complement system in healthy term newborns: reference values in umbilical cord blood

Activation of the complement system occurs in several diseases. For reliable identification of complement activation in neonates, we establish reference ranges of several components in cord blood of healthy term newborns. For this study, cord blood samples were taken from 125 healthy term newborns. Concentrations of C1r, C2, C5, C7, Properdin, and factors D, H, and I were determined by single radial immunodiffusion. C3a and C5a were measured by specific EIA and complement function was measured by hemolytic assays. The results were expressed as 5th percentile, median, and 95th percentile. The following respective concentrations were found: C1r: 27, 47, 65 mg/l; C2: 12.0, 18.0, 24.0 mg/l; C5: 64, 92, 127 mg/l; C7: 32, 60, 89 mg/l; Properdin: 5.6, 9.7, 14.2 mg/l; factor D: 3.6, 5.2, 7.3 mg/l; factor H: 178, 234, 296 mg/l; and factor I: 15, 24, 32 mg/l. The functional activity of the whole complement system was 24%, 43%, 97% and for the alternative pathway 39%, 58%, 76%. The concentration of the activated split products C3a was 4, 65, 255 microg/l and of C5a, 0.11, 0.26, 1.19 microg/l. These reference values may be important for the detection of deficiencies of native complement proteins or perinatal processes leading to an activation of the complement system.

Umbilical artery blood gases in healthy term newborn infants

OBJECTIVE

To study the distributions of pH and gas values in umbilical arterial (UA) blood of normal newborns following uncomplicated pregnancies and vaginal births.

METHODS

In 681 consecutive normal term infants who were born during 1990, we examined the UA pH and blood gas values obtained immediately following delivery. Maternal inclusion criteria were defined as an uncomplicated pregnancy and a normal spontaneous vaginal delivery. Umbilical artery blood samples were collected at each birth and were evaluated for pH, carbon dioxide pressure (PaCO2), oxygen pressure (PaO2), bicarbonate, and base excess. All newborns in this study had the following inclusion criteria: singletons, no malformations, growth appropriate for gestational age (AGA), and Apgar scores of 7 or more at 1, 5 and 10 min of life.

RESULTS

The lowest UA pH was 7.04 and the 10th percentile value was 7.21. The lowest UA PaO2 was 4.6 mmHg and the 10th percentile value was 10.1 mmHg. The highest UA PaCO2 was 75.4 mmHg and the 90th percentile 62 mmHg. The 10th percentile of the base deficit in the extracellular fluid was 5.9 mmol/l.

CONCLUSIONS

The distributions of the UA pH and gas values of a collective of normal newborns were illustrated.

Evaluation of the newborn’s blood gas status

Blood gas measurements and complementary, noninvasive monitoring techniques provide the clinician with information essential to patient assessment, therapeutic decision making, and prognostication. Blood gas measurements are as important for ill newborns as for other critically ill patients, but rapidly changing physiology, difficult access to arterial and mixed venous sampling sites, and small blood volumes present unique challenges. This paper discusses considerations for interpretation of blood gases in the newborn period. Blood gas measurements and noninvasive estimations provide important information about oxygenation. The general goals of oxygen therapy in the neonate are to maintain adequate arterial PaO2 and SaO2, and to minimize cardiac work and the work of breathing. Pulse oximetry and transcutaneous oxygen monitoring are extraordinarily useful techniques of estimating and noninvasively monitoring the neonate’s oxygenation, but each method has limitations. Arterial blood gas determinations of pCO2 provide the most accurate determinations of the adequacy of alveolar ventilation, but capillary, transcutaneous, and end-tidal techniques are also useful. An approach to and examples of acid-base disorders are presented. Three hemoglobin variants relevant to the newborn are considered: fetal hemoglobin, carboxyhemoglobin, and methemoglobin. Blood gases obtained in the immediate perinatal period can help assess perinatal asphyxia, but particular attention must be paid to the sampling site, the time of life, and the possible and proven diagnoses.

Umbilical vein oxygen tension independent from gestational age at birth

Umbilical venous oxygen tension (UVPO2) and gestational age are negatively correlated antepartum. To see if the negative correlation between UVPO2 and gestational age would still be present postpartum, a retrospective study of all 7522 births at the University of Zurich Hospital from 1989 through 1992 was performed. The 6612 infants with UVPO2 values were divided into low and higher risk groups. Singletons between the 10th and 90th weight percentiles, born vaginally with cephalic presentation after spontaneous onset of labor from healthy mothers were considered low risk. All other births were considered higher risk. No correlations between UVPO2 and gestational age were found in any group studied (low risk, higher risk or total population). The higher risk group had a lower mean UVPO2 than the low risk group (p < .0001). Since there is a negative correlation before birth and none after birth, this indicates that some preterm infants may be subject to greater drops in UVPO2 during delivery than term infants. The magnitude of the drop increases with additional complications and immaturity. However, not all preterms have normal UVPO2 values for gestational age antepartum. Some preterms already have a low UVPO2 in utero and experience a drop in UVPO2 during delivery as well.

The oxygen status of fetal blood

OBJECTIVE

To estimate the acid-base and oxygen status of fetal blood and compare with maternal placental venous blood. DATA SOURCES AND CALCULATIONS: We selected pH and blood gas data from the literature pertaining to umbilical vein and artery blood obtained by cordocentesis and estimated values for the 30th and 40th gestational week. Average values for maternal venous blood leaving the placenta were estimated on the assumption of equal maternal arterio-venous and umbilical veno-arterial total oxygen concentration differences.

RESULTS

pH and pCO2 of maternal blood leaving the placenta and umbilical vein blood are almost identical at week 30. A small pCO2 and pH difference may exist at week 40. The pO2 of the maternal placental venous blood and umbilical vein blood are almost identical at week 30, but at week 40 a pO2 difference indicates an umbilical arterio-venous shunting of as much as 30%. The fetal mixed venous pO2 falls from 2.6 kPa to 2.2 kPa from the 30th to the 40th gestational week.

CONCLUSION

More accurate measurements are needed to confirm our results. Future measurements should be performed with a combined pH-blood gas analyser and haemoximeter to allow determination of the complete oxygen status of the blood.