Technical performance of lactate biosensors and a test-strip device during labour.

INTRODUCTION: Lactate in fetal blood has a high diagnostic power to detect fetal compromise due to hypoxia, as lactate allows an estimation of duration and intensity of metabolic acidemia. Biosensor technology allows an instantaneous diagnosis of fetal compromise in the delivery room. The goal of the current investigation is to define the preanalytical and analytical biases of this technology under routine conditions in a labour ward in comparison to test-strip technology, which allows measurement of lactate alone. MATERIAL AND METHODS: Three lactate biosensors (RapidLab 865, Siemens Medical Solutions Diagnostics, Bad Nauheim, Germany; Radiometer ABL625 and ABL 700, Radiometer Copenhagen, Denmark) and one test-strip device (Lactate Pro, Oxford Instruments, UK) were evaluated regarding precision in serial and repetitive measurements in over 1350 samples of fetal whole blood. The coefficient of variation (CV) and the standard deviation (SD) were calculated. The average value of all three biosensors was defined as an artificial reference value (refval). Blood tonometry was performed in order to test the quality of respiratory parameters and to simulate conditions of fetal hypoxia (pO (2): 10 and 20 mmHg). RESULTS: The precision of serial measurements of all biosensors indicated a coefficient of variation (CV) between 1.55 and 3.16% with an SD from 0.042 to 0.053 mmol/L. The test-strip device (Lactate Pro) mounted to 0.117 mmol/L and 3.99% (SD, CV). When compared to our reference value (refval) ABL 625 showed the closest correlation of -0.1%, while Siemens RapidLab 865 showed an overestimation of +8.9%, ABL700 an underestimation of -6.2% and Lactate Pro of -3.7%. CONCLUSION: For routine use all tested biosensors show sufficient precision. The test-strip device shows a slightly higher standard deviation. A direct comparison of measured lactate values from the various devices needs to be interpreted with caution as each method detects different lactate concentrations. Furthermore, the 40 min process of tonometry led to an increase of SD and coefficient of variation in all devices. This results in the important preanalytical finding that the precision of replicated measurements worsens significantly with time. The clinician should be aware of the type of analyser used and of preanalytical biases before making clinical decisions on the basis of lactate values.

Systematic instrumental errors between oxygen saturation analysers in fetal blood during deep hypoxemia.

BACKGROUND: During a study of artificially produced deep hypoxemia in fetal cord blood, systematic errors of three different oxygen saturation analysers were evaluated against a reference CO oximeter. METHODS: The oxygen tensions (PO2) of 83 pre-heparinized fetal blood samples from umbilical veins were reduced by tonometry to 1.3 kPa (10 mm Hg) and 2.7 kPa (20 mm Hg). The oxygen saturation (SO2) was determined (n=1328) on a reference CO oximeter (ABL625, Radiometer Copenhagen) and on three tested instruments (two CO oximeters: Chiron865, Bayer Diagnostics; ABL700, Radiometer Copenhagen, and a portable blood gas analyser, i-STAT, Abbott). The CO oximeters measure the oxyhemoglobin and the reduced hemoglobin fractions by absorption spectrophotometry. The i-STAT system calculates the oxygen saturation from the measured pH, PO2, and PCO2. The measurements were performed in duplicate. Statistical evaluation focused on the differences between duplicate measurements and on systematic instrumental errors in oxygen saturation analysis compared to the reference CO oximeter. RESULTS: After tonometry, the median saturation dropped to 32.9% at a PO2=2.7 kPa (20 mm Hg), defined as saturation range 1, and to 10% SO2 at a PO2=1.3 kPa (10 mm Hg), defined as range 2. With decreasing SO2, all devices showed an increased difference between duplicate measurements. ABL625 and ABL700 showed the closest agreement between instruments (0.25% SO2 bias at saturation range 1 and -0.33% SO2 bias at saturation range 2). Chiron865 indicated higher saturation values than ABL 625 (3.07% SO2 bias at saturation range 1 and 2.28% SO2 bias at saturation range 2). Calculated saturation values (i-STAT) were more than 30% lower than the measured values of ABL625. CONCLUSION: The disagreement among CO oximeters was small but increasing under deep hypoxemia. Calculation found unacceptably low saturation.

Perinatal differential diagnosis of cystic kidney disease and urinary tract obstruction: anatomic pathologic, ultrasonographic and genetic findings.

According to the classification of Osathanondh and Potter of cystic kidney diseases an antenatal differential diagnosis is presented, which is based on the anatomic pathologic, ultrasonographic and genetic findings. Since the ultrasound evaluation influences the obstetric and neonatal management, each second and third trimester sonography should consider the most common malformations in pediatric autopsies. The autosomal recessive polycystic kidney disease (ARPK), autosomal dominant polycystic kidney disease (ADPK), multicystic renal dysplasia, obstructive multicystic kidneys and cystic renal malformations found in other syndromes with genetic linkage are discussed in this review.

Fetal pulse oximetry.

Within the last ten years several groups adapted pulse oximetry to be used in the fetus. The obvious advantage of this technology is the fact that a biochemical parameter--the arterial oxygen saturation--can be measured continuously during delivery. Nevertheless, the continuous information about the fetal oxygenation during delivery has a couple of obstacles to surmount. It is well known that fetal reflectance pulse oximetry may be influenced by a number of artifacts. In addition, severe physiological considerations should remind us of the limited diagnostic value of saturation monitoring alone in order to predict fetal acidosis. Some recent articles deal with the predictive value of fetal pulse oximetry for fetal compromise. While it appears that the fetal wellbeing is more likely to be in accordance with a normal saturation measured by current pulse oximetry systems, the number of fetuses detected by pulse oximetry suffering from hypoxia seems to be low. Different authors describe a poor sensitivity to predict fetal compromise. One reason therefore may be the reduced precision of the oxysensor in the low saturation range. Therefore, we conclude that the current generation of fetal pulse oximetry sensors is not improving the quality of combined fetal monitoring of fetal heart rate and fetal scalp blood analysis.

Correlation of fetal oxygen saturation to fetal heart rate patterns. Evaluation of fetal pulse oximetry with two different oxisensors.

BACKGROUND: The purpose of this study was the correlation of fetal oxygen saturation values to various fetal heart rate patterns, as well as to oxygen saturation values obtained by fetal blood analysis. These objectives need to be evaluated from the perspective that two generations of fetal oxisensors have been used. METHODS: Two different oxisensor systems (FS10: 660+890 nm and FS14: 735+890 nm) and a blinded pulse oximeter (type N400, Nellcor Puritan Bennett) were utilized to monitor 112 fetuses. All data, including oxygen saturation, fetal heart rate patterns, signal and contact quality were stored on a personal computer and evaluated after delivery. RESULTS: The following median fetal oxygen saturation values were obtained: during reassuring fetal heart rate sequences 54% with the oxisensor FS10 and 48% with the newer FS14 oxisensor, during intervals of variable decelerations 43% with the FS10 oxisensor and 40% with the FS14 oxisensor. These differences between values obtained during normal and abnormal fetal heart rate patterns are significant. Due to non-reassuring fetal heart rate patterns 81 fetal blood analyses were performed. The values of pulse oximetry were 9% higher (6% for the FS14) than those of spectrophotometry. Correlation of both methods was r=0.66 (0.74 for the FS14). CONCLUSIONS: In combination with fetal heart rate monitoring, fetal pulse oximetry promises a better differentiation between low and high risk heart rate patterns. Oxygen saturation values from intermittent fetal blood sampling reassure the clinician concerning the accuracy of this new method of intrapartum fetal surveillance and underline the increased quality of the new generation of oxisensor using light of a wavelength of 735 and 890 nm.

The safety of fetal pulse oximetry in parturients requiring fetal scalp blood sampling.

OBJECTIVE: To determine whether maternal or fetal morbidity is increased in association with fetal pulse oximetry monitoring using an atraumatic intrapartum transcervical fetal oxisensor. METHODS: In a prospective cohort study from January 1993 to June 1996, 196 fetuses were monitored during the intrapartum period with a fetal oximetry sensor placed between the uterine wall and the presenting fetal part. The oxisensors were in position for a median duration of 134 minutes. A total of 101 monitored fetuses underwent intrapartum fetal scalp blood sampling because of nonreassuring heart rate tracings. For a control group, we selected all cases during the same period in which fetal blood sampling was performed in the intrapartum period (n = 949) without pulse oximetry monitoring. Data for maternal and fetal morbidity were evaluated and tested for significant differences by the Mann-Whitney U test. RESULTS: There was no significant difference in gestational age, birth weight, duration of labor, fetal outcome parameters, cesarean rate, operative vaginal deliveries, episiotomy rate, or perineal injuries between the study and control groups. Similarly, the percentages of neonatal intensive care unit admissions, neonatal resuscitations, and neonatal infections were not statistically different in the two groups. A rare complication in the group with pulse oximetry monitoring was a transient impression of the oxisensor probe on the fetal cheek. The rates of postpartum maternal infections, anemia, or secondary wound disruptions were identical in both groups. CONCLUSION: There was no increased fetal or maternal morbidity associated with the use of an atraumatic intrapartum fetal pulse oxisensor.

The efficacy of intrapartum fetal surveillance when fetal pulse oximetry is added to cardiotocography.

OBJECTIVE: To determine if oxygen saturation measurement with pulse oximetry (SpO2) in combination with cardiotocograghy (CTG), improves the assessment of the intrapartum fetal condition. STUDY DESIGN: Four expert obstetricians individually evaluated 119 cases that were monitored during labor: during the first session the CTG data were available, and in the second session CTG and SpO2 data were evaluated. They were instructed to indicate the need for intervention and to estimate the umbilical artery pH. RESULTS: In the non-acidotic group (umbilical artery pH > or = 7.15, n = 112) the average(+/-S.D.) number of interventions decreased from 27(+/-17) to 16(+/-9) when SpO2 was available. This reduction in number of interventions resulted in an significantly increased specificity for two referees. In the acidotic group (n = 7) the average number of interventions also decreased, from 6(+/-2) to 4(+/-2), and as a consequence the sensitivity decreased. The pH estimate based on CTG + SpO2 was higher in both acidotic and non-acidotic fetuses than the estimated pH based on CTG alone. CONCLUSION: In this study all referees intervened less frequently when SpO2 was used as an adjunct to CTG. This resulted in fewer unnecessary operative interventions, but may also lead to unidentified fetal acidosis. The number of acidotic newborns (n = 7) was too small, however, to draw definite conclusions. Larger studies should address the efficacy of SpO2 in detecting fetal compromise before clinical use can be advocated.

[Lactate and glucose determination using biosensors in umbilical cord blood]. / Laktat- und Glucosebestimmung mittels Biosensoren im Nabelschnurblut.

Postpartal determination of lactate and glucose in the umbilical cord whole blood of 139 successive deliveries utilizing biosensors (blood gas analysator 865, Ciba Corning) are presented. The median lactate value in the umbilical arterial blood is 4.45 mmol/l and in the venous blood 4.23 mmol/l. Following categorization into control and high-risk groups, the arterial mean values are 4.23 mmol/l and 6.39 mmol/l and the respective venous values are 3.95 mmol/l and 5.04 mmol/l. Using the U-test these differences between the control and high-risk groups are significant. The mean of the measured lactate correlates significantly with the mean of the calculated base excess (< 0.001). The mean glucose value in the umbilical arterial blood is 78 mg/dl and in the venous 93 mg/dl. Between high-risk and control group no significant difference is found.

[Evaluating pulse oximetry in the fetus. Case control study for detection of undesirable complications]. / Evaluierung der Pulsoximetrie am Feten. Fallkontrollstudie zur Erfassung unerwünschter Komplikationen.

OBJECTIVES: Fetal pulse oximetry (PO) requires basically continuous contact of a transcervically positioned oxisensor with fetal skin. To improve signal quality adjustments of the oxisensor may be necessary. Against this background it was our intention to find out if this intrauterine device causes an increase in fetal or maternal infectious morbidity. STUDY DESIGN: We enrolled into this prospective trial 63 deliveries monitored by a blinded fetal pulse oximeter (N 400, Nellcor Inc. Pleasanton, CA) and a fetal oxisensor (FS 10; lambda = 660 + 890 nm). The control group of similar gestational age was formed by 63 chronologically following deliveries under responsibility of the same physician to reduce personal bias of obstetrical management. RESULTS: While the obstetrical risk factors (non-reassuring FHR i.e.) were significantly higher in the group with PO, gestational age, number of operative deliveries, pH of umbilical cord and Apgar score ratings did not show any significant difference. The number of post partum anaemias and local or systemic infections were identical (3 in each group). Seven neonates of the PO group had to be transferred to NICU versus 12 in the control group. The duration of antibiotic treatment, mechanical ventilation or phototherapy did not differ significantly; neither did the number of neonatal infections. CONCLUSION: In the group of fetuses monitored by fetal pulse oximetry there was no increase in fetal or maternal infectious morbidity. There was no evidence of adverse side effects which might limit the advantage of continuous oxygen saturation monitoring.

Fetal pulse oximetry.

Fetal pulse oximetry provides a tool for the surveillance of the fetus at risk of hypoxia. The experience of 150 deliveries monitored by pulse oximetry and the analysis of data may allow preliminary recommendations for clinical use in cases of suspected fetal hypoxia based on a suspicious FHR. In most cases, saturation values above 33% suggest fetal well-being. Further fetal evaluation, for example by fetal blood samples or other means, is necessary to assess alterations of FHR pattern or decreases in saturation values. Pulse oximetry may allow a differentiation between cases that need further evaluation, such as scalp blood sampling, and those which do not. The number of repeated assessments may be reduced as long as the oxygen saturation and FHR pattern do not worsen. The effect of therapeutic measures on fetal oxygenation can be directly observed. The positive preliminary experiences with fetal pulse oximetry predominate even if high expectations of easy detection of fetal hypoxia have so far not been fulfilled.

Continuous monitoring of fetal oxygen saturation by pulse oximetry.

OBJECTIVE: To compare spectrophotometric saturation values of fetal blood sampling to the saturation readings by pulse oximetry. METHODS: During a clinical trial, fetal oxygen saturation was monitored during labor by a fetal oxisensor and a fetal pulse oximeter. Fifty-one fetal scalp blood samples were assessed because of abnormal fetal heart rate (FHR) patterns. The pulse oximeter displayed only signal quality readings. The investigator had to perform adjustments if signal quality fell below 50%. After delivery, the saturation at the moment of fetal blood analysis could be read from a printout and compared to the saturation values of scalp blood sampling. RESULTS: The share of usable signal time was 51% overall, but only 40% in the 20-minute period during fetal blood sampling. Comparison with the reference method resulted in a median deviation of 6% (tenth percentile -10%; 90th percentile 18%) for pulse oximetry. The correlation coefficient between saturation values by pulse oximetry and fetal scalp blood sampling was 0.67. The correlation coefficient with the partial pressure of oxygen and oxygen saturation by pulse oximetry was 0.61, whereas it was 0.88 between partial pressure and saturation from the spectrophotometric analysis of the scalp sample. CONCLUSIONS: Fetal pulse oximetry corresponds satisfactorily to results from fetal blood analysis. Low invasiveness and continuous monitoring are the advantages of this method. At present, the available sensor generates only a limited amount of signal time. However, in combination with FHR monitoring, pulse oximetry promises greatly improved detection of fetal hypoxia.

[Value of measuring fetal oxygen saturation for reducing the need for fetal blood analysis in abnormal cardiotocogram. Experiences with 2 sensor generations of fetal reflexion pulse oximetry]. / Bedeutung der fetalen Sauerstoffsättingungsmessung zur Reduktion von Fetalblutanalysen bei suspektem Kardiotokogramm. Erfahrungen mit zwei Sensorgenerationen der Reflexionspulsoximetrie am Feten.

OBJECTIVES: Does the knowledge of fetal oxygen saturation allow to avoid fetal scalp blood sampling and to predict a pH < or = 7.25 of the fetal blood sample? STUDY DESIGN: Out of a group of 135 fetuses we determined the median, the 10th, 5th and 3rd percentile of oxygen saturation values by a blinded fetal pulse oximeter. Due to abnormal FHR-patterns, 110 fetal scalp blood samples (FBA) were assessed by the technique introduced by Saling. The pH of these FBA's ranged from 7,16-7,48 (median 7,28). We chose a 20 minute period before the FBA and calculated the individual median and percentiles. According to the pH of < or = 7,25 in FBA we calculated the chi-square test for significance. RESULTS: The median of <35% SpO2 has a sensitivity of 23%, specificity of 77%, positive predictive value of 27% and a negative predictive value of 73%. CONCLUSION: Fetal oxygen saturation alone shows a high specificity and a low sensitivity for pH < 7,25. In addition to FHR monitoring, pulse oximetry.

[Fetal oxygen saturation in suspected hypoxia and the normal cardiotocogram (CTG). A prospective study for validating pulse oximetry in the fetus]. / Fetale Sauerstoffsttigung bei hypoxieverdächtigem und unauffälligem Kardiotokogramm (CTG). Eine prospektive Untersuchung zur Validierung der Pulsoximetrie am Feten.

During a clinical study 70 women in labour were monitored with fetal pulse oximetry. The oxisensor (FS 10) was positioned between fetal cheek and the uterine wall at a cervical dilatation of 2 cm or more. The advantage of the method is its minimal invasive character and the continuous monitoring of oxygen saturation. The pulse oximeter (N 400, Nellcor) had been blinded for the investigation following criteria met by FDA, so that the investigator could not read the saturation values. Preliminary results of more than 120 hours of monitoring intervals of 10 seconds show the following saturation values (median): 55% under normal CTG (10. perc. 36%, 90. perc. 73%), 42% during episodes of variable decelerations (10. perc. 22%, 90. perc. 63%), 53% during episodes of early decelerations (10. perc. 39%, 90. perc. 74%). Due to pathological fetal heart rate patterns 42 fetal blood analysis were performed. Because of these spectrophotometric saturation measurements (ABL 330, OSM 3, Radiometer) the deviation of the two methods could be calculated. The values of pulse oximetry were 5% higher than those of spectrophotometry. Correlation of both methods was r = 0.64.

Differences in morbidity and mortality according to type of referral of very low birthweight infants.

Maternal and social risk, prenatal and obstetric care, resuscitation and neonatal care in very-low-birthweight infants (VLBW) may vary with the type of referral. In 453 VLBW's (< 1500 g) admitted to our neonatal intensive care unit 1987-1992, we classified transport type as: A: No transport (n = 240), B: Maternal transport (n = 88), C: Infant transport (n = 125). Stepwise multiple discriminant function was determined for the identified factors. The risk of mortality was investigated by logistic regression analysis. In group A, mean maternal age was higher and mothers' social status lower than in groups B and C. In group B, infants were considerably smaller and less mature, but when adjusted for gestational age, suffered less frequently from RDS, obviously due to more frequent induction of lung maturation. In group C, less than half of the infants were resuscitated by a neonatologist. Infants of this group were frequently hypothermic at admission and required prolonged artificial ventilation more frequently. Total VLBW survival averaged 77%, increasing from 69 to 88% within the study period. Total rate of severe intraventricular hemorrhage was 4.8% in surviving infants. VLBW infants with different forms of referral differ in their inherent risk. After maternal transport they have less morbidity despite a higher grade of immaturity. Regionalization of perinatal care for these infants remains the greatest potential for further reduction in infant mortality.

[Prospective study of the clinical value of C-reactive protein in amniotic infection syndrome]. / Prospektive Untersuchung über die klinische Wertigkeit des C-reaktiven Proteins beim Amnioninfektionssyndrom.

In an open prospective investigation the median levels of C-reactive protein were determined in annormal collective. The median lies at 0.8 mg/dl in maternal serum withdrawn sub partu and in umbilical vein blood, and at 1.45 mg/dl immediately after ligation of the cord. Hopes on finding a biochemical parameter that could supply reliable information already during labour on a possible inflammatory infection in mother and child, did not materialize from the data found. Prediction of an infection of the newborn using CPR is only minimal. The most important practical information is given by the negative CRP in the umbilical vein blood. In this case the probability of an infection of the newborn is very slight. A high temperature during labour was the best predictor of the probability of endometritis puerperalis. This clinical finding, due to its specificity, is superior to CRP and the other parameters investigated.

[Reducing the incidence and morbidity of very low birth weight premature infants after maternal transport to a perinatal center]. / Senkung von Häufigkeit und Morbidität sehr untergewichtiger Frühgeborener nach mütterlichem Transport in ein perinatales Zentrum.

An improvement in the mortality and morbidity of very low-birth-weight infants could be confirmed by the regionalisation of high-risk pregnancies. The immaturity of premature newborn limits the therapeutic success. Our aim is therefore on the one hand, to make an early diagnosis of patients at risk of threatened premature delivery, and secondly, to provide intensive therapy for women already showing symptoms of premature delivery, to achieve the best possible prognosis. A reduction in the number of very low birth-weight infants and their mortality and morbidity rate appears to be possible if the pregnant women can be placed in a perinatal centre in good time; if the pregnancy can be prolonged and fetal lung maturation can be induced by betamethasone; if the delivery can be managed carefully, avoiding hypoxaemia, shock situations, and trauma; in certain cases this would mean performing a caesarean section by isthmo-cervical longitudinal incision; if primary neonatal care is performed by an experienced neonatologist. With the standard of neonatology as it is today, a considerable increase in the survival rates of very low birth-weight infants can hardly be expected. Nevertheless, to cut down their numbers is the biggest potential for the future reduction of the infant mortality rate.

[Alpha-thalassemia as a rare differential diagnosis of hydrops fetalis et placentae]. / Die alpha-Thalassämie als seltene Differentialdiagnose des Hydrops fetalis et placentae.

alpha-Thalassaemia is a disturbance of the alpha-chain synthesis of the haemoglobin, which occurs mostly in the Far East. On account of the total absence of alpha-chains, the homozygous form is considered to be fatal. However, beta and lambda chains exist abundantly. Abortion, intrauterine or perinatal death are the results of the extreme anaemia (Hb-Bart's syndrome), despite modern intensive medical care. The prenatal diagnosis is possible by: 1. DNA analysis of material obtained by chorion villi sampling or culture of fibroblasts, when a risk of re-occurrence is known to the physician. 2. Hb-electrophoresis from foetal blood in cases of hydrops of uncertain origin. When the diagnosis of this fatal disease is established, there is no foetal indication for delivery by Caesarian section.

[Diagnosis of postpartal disorders of adaptation in hospital delivery of out patients]. / Diagnostik postpartaler Adaptationsstörungen bei der ambulanten Klinikentbindung.

Delivery in a hospital on an outpatient basis is increasingly accepted in obstetrics. In West Berlin about 15% of the mothers consider this as desirable, and about 10% actually utilize it. Delivery at home, which is associated with safety hazards, is getting less frequent. Since the problem of disturbed adaptation of the infant can be quite difficult, the method of choice is the easily manageable noninvasive monitoring of heart and respiratory frequency of the newborn during the first hour after birth. This can help to detect latent disturbances of adaptation and premature discharge of the infant from hospital is avoided. The following aspects must be considered: 1. Monitoring is noninvasive and does not exercise stress on the infant. 2. Mother and child are not separated during the monitoring. Hence, the early mother-child relationship is not disturbed. 3. The obstetrician can assess the state of adaptation of the newborn more clearly with the help of the cardiorespiratory diagram. This makes it easier for him to decide whether a child may be released or ought to stay in hospital. 4. If the paediatrician is consulted, he has at his command useful data on a child he does not know with the exception of a few anamnestic data and the actual examination findings.