Correlation of cord blood pH, base excess, and lactate concentration measured with a portable device for identifying fetal acidosis

Effect of pre-operative bicarbonate infusion on maternal and perinatal outcomes among women with obstructed labour in Mbale hospital: A double blind randomized controlled trial

INTRODUCTION

Oral bicarbonate solution is known to improve both maternal and perinatal outcomes among women with abnormal labour (dystocia). Its effectiveness and safety among women with obstructed labour is not known.

OBJECTIVE

To determine the effect and safety of a single-dose preoperative infusion of sodium bicarbonate on maternal and fetal blood lactate and clinical outcomes among women with obstructed labour (OL) in Mbale hospital.

METHODS

We conducted a double blind, randomised controlled trial from July 2018 to September 2019. The participants were women with OL at term (≥37 weeks gestation), carrying a singleton pregnancy with no other obstetric emergency, medical comorbidity or laboratory derangements.

INTERVENTION

A total of 477 women with OL were randomized to receive 50ml of 8.4% sodium bicarbonate (238 women) or 50 mL of 0.9% sodium chloride (239 women). In both the intervention and controls arms, each participant was preoperatively given a single dose intravenous bolus. Every participant received 1.5 L of normal saline in one hour as part of standard preoperative care.

OUTCOME MEASURES

Our primary outcome was the mean difference in maternal venous blood lactate at one hour between the two arms. The secondary outcomes were umbilical cord blood lactate levels at birth, neonatal sepsis and early neonatal death upto 7 days postnatal, as well as the side effects of sodium bicarbonate, primary postpartum hemorrhage, maternal sepsis and mortality at 14 days postpartum.

RESULTS

The median maternal venous lactate was 6.4 (IQR 3.3-12.3) in the intervention and 7.5 (IQR 4.0-15.8) in the control group, with a statistically non-significant median difference of 1.2 mmol/L; p-value = 0.087. Vargha and Delaney effect size was 0.46 (95% CI 0.40-0.51) implying very little if any effect at all.

CONCLUSION

The 4.2g of preoperative intravenous sodium bicarbonate was safe but made little or no difference on blood lactate levels.

TRIAL REGISTRATION

PACTR201805003364421.

A before and after study of the impact on obstetric and perinatal outcomes following the introduction of an educational package of fetal heart rate monitoring education coupled with umbilical artery lactate sampling in a low resource setting labor ward in South Africa

Introduction

Rates of cesarean section (CS) are increasing and abnormal fetal heart rate tracing and concern about consequent acidosis remain one of the most common indications for primary CS. Umbilical artery (UA) lactate sampling provides clinicians with point of care feedback on CTG interpretation and intrapartum care and may result in altered future practice.

Materials and methods

From 3rd March - 12th November 2014 we undertook a before and after study in Pretoria, South Africa, to determine the impact of introducing a clinical package of fetal heart rate monitoring education and prompt feedback with UA cord lactate sampling, using a hand-held meter, on maternal and perinatal outcomes.

Results

Nine hundred thirty-six consecutive samples were analyzed (pre n = 374 and post n = 562). There was no difference in mean lactate (4.6 mmol/L [95%CI 4.4–4.8] compared with 4.9 mmol/L [95%CI 4.7–5.1], p = 0.089). Suspected fetal compromise was reduced in the post-intervention period: 30·2% vs 22·1%, aOR 0·71, 95% CI 0·52–0·96, p = 0·027. Cesarean section rates were significantly reduced in the univariate analysis: pre- 40·3% vs post-intervention 31·6% (p = 0·007). This reduction remained significant when adjusted for previous cesarean section, primiparity, maternal HIV infection and preterm birth (aOR 0·72, 95%CI 0·54–0·98, p = 0·035). Neonatal outcomes did not differ between the two groups.

Conclusion

The introduction of a clinical practice package of fetal heart rate monitoring education combined with routine UA cord lactate sampling has the potential to reduce the cesarean section rate without increasing adverse neonatal outcomes in a low-resource setting.

The comparison of umbilical cord arterial blood lactate and pH values for predicting short-term neonatal outcomes

OBJECTIVE

Current clinical practice of assessing neonatal condition is based on evaluation of umbilical cord arterial blood pH value rather than lactate. However, evidence shows that lactate is direct and more predictive measurement than pH or at least of equal importance. This study is to assess and compare umbilical cord arterial lactate and pH values for predicting short-term neonatal outcomes.

MATERIALS AND METHODS

A retrospective cohort study was conducted at the tertiary level hospital, were arterial umbilical cord blood sampling was collected according to the standard procedures. Neonatal morbidity was registered if at least one of the following conditions was noted: Apgar score at 1 min after delivery was 6 or lower, resuscitation performed, including assisted ventilation and requirement of admission to neonatal intensive care unit. Mothers-newborns pairs were allocated into two groups: newborns exposed to perinatal hypoxia (group 1) and observed as healthy newborns (group 2). Receiver operating characteristics curves (ROC) were generated to assess the predictive ability of pH and lactate for the short-term neonatal outcomes.

RESULTS

901 neonates born at ≥37 weeks of gestation were included. Newborns exposed to perinatal hypoxia (group 1) encompassed 39 (4.3%) patients, and observed as healthy (group 2) - 862 (95.7%). Arterial umbilical cord blood pH in group 1 was 7.160 ± 0.126 as compared to 7.314 ± 0.083 in group 2; p < 0.001. Mean arterial lactate was significantly higher in group 1 than group 2 (6.423 ± 2.335 as compared to 3.600 ± 1.833; p < 0.001). The difference between areas under ROC curves representing pH and lactate was not significant (0.848 and 0.831 respectively; p = 0.6132).

CONCLUSION

Umbilical cord arterial lactate and pH predicted short-term neonatal outcomes with similar efficacies.

Umbilical lactate as a measure of acidosis and predictor of neonatal risk: a systematic review

BACKGROUND

Umbilical cord lactate is one approach to measuring acidosis and intrapartum hypoxia, knowledge of which may be helpful for clinicians involved in the care of women and newborns.

OBJECTIVE

To synthesise the evidence on accuracy of umbilical cord lactate in measuring acidosis and predicting poor neonatal outcome.

SEARCH STRATEGY

Studies published and unpublished between 1990 and 2014 from PubMed/Medline, EMBASE, Cochrane Central Register of Controlled Trials, and clinicaltrials.gov were assessed.

SELECTION CRITERIA

Cross-sectional and randomised studies that assessed fetal acidosis (using lactate as the index test) with or without an assessment of neonatal outcome.

DATA COLLECTION AND ANALYSIS

Correlations between index and reference test(s) were recorded, as were the raw data to classify the predictive ability of umbilical lactate for neonatal outcomes. Meta-analysis of correlation was performed. We plotted estimates of the studies' observed sensitivities and specificities on Forest plots with 95% confidence intervals (CI). Where possible, we combined data using meta-analysis, applying the hierarchical summary receiver operating characteristics model and a bivariate model.

MAIN RESULTS

Twelve studies were included. Umbilical lactate correlated with pH [pooled effect size (ES) -0.650; 95% CI -0.663 to -0.637, P < 0.001], base excess (ES -0.710; 95% CI -0.721 to -0.699, P < 0.001), and Apgar scores at 5 minutes (ES 0.300; 95% 0.193-0.407, P < 0.001). Umbilical lactate had pooled sensitivity and specificity for predicting neonatal neurological outcome including hypoxic ischaemic encephalopathy of 69.7% (95% CI 23.8-94.4%) and 93% (95% CI 86.8-96.3%).

AUTHORS' CONCLUSION

Umbilical cord lactate is a clinically applicable, inexpensive and effective way to measure acidosis and is a tool that may be used in the assessment of neonatal outcome.

TWEETABLE ABSTRACT

Umbilical cord lactate: a clinically applicable, inexpensive, effective way to measure intrapartum acidosis.

Attitudes towards the implementation of universal umbilical artery lactate analysis in a South African district hospital

Background

Of the 5.54 million stillbirths and neonatal deaths occurring globally each year, a significant amount of these occur in the setting of inadequate intrapartum care. The introduction of universal umbilical artery lactate (UA) measurements in this setting may improve outcomes by providing an objective measurement of quality of care and stimulating case reflection, audit, and practice change. It is important that consideration is given to the barriers and facilitators to implementing this tool outside of a research setting.

Methods

During the period 16/11/2014 -13/01/2015, we conducted a training course in cardiotocograph (CTG) interpretation, fetal physiology, and the sampling and analysing of UA lactate, with a pre and post questionnaire aimed at assessing the barriers and facilitators to the introduction of universal UA lactate in a district hospital in the Eastern Cape, South Africa.

Results

Thirty-five pre-training questionnaires available (overall response rate 95 %) and 22 post training questionnaires (response rate 63 %) were available for analysis. Prior to training, the majority gave positive responses (strongly agree or agree) that measuring UA lactate assists neonatal care, is protective for staff medicolegally, and improves opportunities for audit and teaching of maternity practice (n = 33, 30, 32; 94.4 %, 85.7 %, 91.4 % respectively). Respondents remained positive about the benefits post training. An increased workload on medical or midwifery staff was less likely to be seen as barrier following training (71 vs. 38.9 % positive response, p = 0.038). A higher rate of respondents felt that expense and lack of equipment were likely to be barriers after completing training, although this wasn’t significant. There was a trend towards lack of time and expertise being less likely to be seen as barriers post training.

Conclusion

The majority of participants providing intrapartum care in this setting are positive about the role of universal UA lactate analysis and the potential benefits it provides. Training aids in overcoming some of the perceived barriers to implementation of universal UA lactate analysis.

Lactate point-of-care testing for acidosis: Cross-comparison of two devices with routine laboratory results

Objectives

Lactate is a major parameter in medical decision making. During labor, it is an indicator for fetal acidosis and immediate intervention. In the Emergency Department (ED), rapid analysis of lactate/blood gas is crucial for optimal patient care. Our objectives were to cross-compare-for the first time-two point-of-care testing (POCT) lactate devices with routine laboratory results using novel tight precision targets and evaluate different lactate cut-off concentrations to predict metabolic acidosis.

Design and methods

Blood samples from the delivery room (n=66) and from the ED (n=85) were analyzed on two POCT devices, the StatStrip-Lactate (Nova Biomedical) and the iSTAT-1 (CG4+ cassettes, Abbott), and compared to the routine laboratory analyzer (ABL-735, Radiometer). Lactate concentrations were cross-compared between these analyzers.

Results

The StatStrip correlated well with the ABL-735 (R=0.9737) and with the iSTAT-1 (R=0.9774) for lactate in umbilical cord blood. Lactate concentrations in ED samples measured on the iSTAT-1 and ABL-735 showed a correlation coefficient of R=0.9953. Analytical imprecision was excellent for lactate and pH, while for pO₂ and pCO₂ the coefficient of variation was relatively high using the iSTAT-1.

Conclusion

Both POCT devices showed adequate analytical performance to measure lactate. The StatStrip can indicate metabolic acidosis in 1 μl blood and will be implemented at the delivery room.