Fetal monitoring with lactate

[Comparison of the measurement of lactate at the cord by hand-held devices approved for use during labor with a reference device]

OBJECTIVE

To compare two portable lactate devices, Lactate Scout and StatStrip Xpress, to a laboratory reference device by assessing the concordance of cord blood lactate values at birth.

METHODS

We conducted a single-center prospective validation study in a level 3 maternity hospital. For all cord samples taken at birth, we analyzed lactates on the reference device (GEM4000®) and on two portable devices Lactate Scout and StatStrip Xpress. We compared the lactate values from each of the two handheld devices to the reference device.

RESULTS

A total of 101 samples were collected. Each was analyzed by all three machines. The average lactate value obtained by the different machines was 3.7mmol/L. The mean difference between the Lactate Scout and GEM4000® apparatus was 0.0mmol/L±0.8mmol/L. Between these two devices at lactate threshold of 4.8mmol/L, the negative predictive value was 96,2% (76/79) and the area under the curve was 0.98 (95% CI 0.96-1]. The mean difference between StatStrip Xpress and GEM4000® was 0.1mmol/L±0.7mmol/L. Between these two devices at the lactate threshold of 4.8mmol/L, the negative predictive value was 97,4% (76/78) and the area under the curve was 0.95 (95% CI 0.86-1).

CONCLUSION

There is a good correlation between the lactates obtained by the reference device and the two portable devices Lactate Scout and StatStrip Xpress.

Intrapartum fetal asphyxia: study of umbilical cord blood lactate in relation to fetal heart rate patterns

PURPOSES

To correlate between umbilical artery cord blood lactate and acid-base status with intrapartum fetal heart rate monitoring, and to measure the reliability of umbilical cord blood lactate for prediction of early neonatal outcome.

METHODS

Sixty-six participants with intrapartum abnormal fetal heart rate monitoring and 60 participants with normal intrapartum recordings were recruited. The abnormal recordings included late onset, atypical variable and simple variable decelerations. After delivery, the arterial cord blood lactate, pH, actual base excess (ABE), and Apgar score were measured in all participants.

RESULTS

There was significant inverse correlation between cord lactate and pH and ABE in all participants (correlation coefficient = -0.7, p < 0.0001). The cord lactate was significantly higher in the late onset and atypical variable decelerations groups compared to control (p < 0.0001). There was no significant correlation between the Apgar score and blood lactate in all groups; however, the sensitivity and specificity of cord lactate to predict low score at 5 min were higher in comparison to cord pH.

CONCLUSIONS

Umbilical cord blood lactate is a reliable marker for intrapartum fetal asphyxia compared to cord acid-base status with better prediction for newborns with low Apgar score.

Surveillance during labour

The technology of intrapartum surveillance made rapid strides from the 1960s through the 1980s but then stagnated as increasing resort to caesarean section was made rather than improving measures of fetal condition and labour progress. However, despite caesarean section rates commonly over 30%, medicolegally expensive mistakes continue to be made because it is difficult to teach clinicians to make reliable use of existing technology. It may be that as with aircraft navigation, the safest solution is to replace human judgement with the obstetric equivalent of automatic pilots.

[Fetal pulse oximetry: clinical practice]

OBJECTIVE

To assess in current practice the application of our protocol of using fetal pulse oximetry during labor, to evaluate whether fetal scalp blood sampling can be reduced and to determinate reliability of fetal pulse oximetry on the prediction of poor neonatal outcomes.

STUDY DESIGN

Prospective observational unicenter cohort including 449 patients during two years. All pregnancies were singleton, greater than or equal to 37 weeks' gestation, cephalic presentation, and had non reassuring fetal heart rate. The poor neonatal outcome was defined by one of the followings: arterial umbilical cord pH<or=7.15, umbilical cord base deficit greater than or equal to 12 mmol/l, 5 min Apgar score less than or equal to 7, transfer in neonatal intensive care unit, secondary respiratory distress and death.

RESULTS

The use of fetal pulse oximetry was concordant with our protocol in more than 80% of cases. The frequency of fetal scalp blood sampling was significantly reduced from 9.9 to 8.6% after the introduction of our protocol. With a 30% threshold, diagnostical values of fetal oximetry for a poor neonatal outcome were 9.1% for sensitivity, 93.1% for specificity, 79.4% for negative predictive value and 25.9% for positive predictive value. With a 40% threshold, the diagnostic values were 74, 51.6, 88.2 and 28.9% respectively.

CONCLUSION

The strict application of our protocol allow a less aggressive management of labor with a significant decrease in fetal scalp blood sampling. This study shows that with a 40% threshold, fetal pulse oximetry could be considered as a reliable tool for the management of labor with no increase of poor neonatal outcomes. On the other hand, the threshold which could determine whether an abnormal fetal heart rate needs immediate intervention still remains unclear.

[Fetal scalp blood sampling for pH and lactate measurement during labour]

The wide use of continuous of fetal heart rate monitoring (FHR) since the seventies has been accompanied by an increase in cesarean delivery rates, without any decrease in cerebral palsy rate. Second line methods of fetal monitoring have been developed in order to better identify fetuses truly at risk of intrapartum asphyxia. The use of fetal scalp blood sampling (FBS) for fetal monitoring seems logical since neonatal acidosis is one of the major criteria of birth asphyxia. Studies show that the use of FBS reduces the increase in cesarean deliveries associated with the use of continuous FHR monitoring. However, FBS is invasive, non continuous and technically uneasy, with a rather high rate of failed blood samplings. Fetal scalp lactates measurement by micromethod requires a much smaller volume of blood. Although a wider assessment is required, the predictive value of fetal blood lactates seems to be similar to that of fetal scalp blood pH.

Lactacidemia in intrauterine growth restricted (IUGR) pregnancies: relationship to clinical severity, oxygenation and placental weight

The aim of the study was to evaluate the impact of clinical severity and placental weight upon fetal lactacidemia in intrauterine growth restricted (IUGR) pregnancies. Seventy pregnancies complicated by IUGR were compared with 70 normal (appropriate for gestational age, AGA) pregnancies at the time of elective cesarean section. IUGR pregnancies were divided according to clinical severity in three groups: Group 1 had normal fetal heart rate (FHR) and normal pulsatility index of the umbilical artery (PI); Group 2 had normal FHR and abnormal PI; and Group 3 had abnormal FHR and PI. No cases with severe lactacidemia had placental weights >or=250 g. Forty-four fetuses had placental weight <250 g: Twenty-four had severe lactacidemia and all were Group 2 and 3, whereas 20 had normal umbilical artery lac (lactate) (and small placentas) regardless of the clinical severity. Gestational age, fetal and placental weights, F/P ratios, uv (umbilical vein) and ua lac and ua oxygen content and pH were significantly decreased in fetuses with small placentas and high lactate. There was a significant relationship between fetal and placental weight in AGA and IUGR. However, IUGR fetuses with placental weight >or=250 g exhibited an F/P ratio significantly lower than that in AGA fetuses suggesting that IUGR may be due to a reduction of placental function per gram of tissue.