Cost effectiveness of universal umbilical cord blood gas and lactate analysis in a tertiary level maternity unit

A cost-effectiveness analysis of using umbilical cord blood pH for the diagnosis and management of neonatal asphyxia in term high-risk pregnancy

OBJECTIVE

The objective was to evaluate the cost-effectiveness of using umbilical cord blood pH (UC-pH) in combination with APGAR score for neonatal asphyxia, in terms of high-risk pregnancies, compared to using the APGAR score only. Neonatal outcomes and the proportions of patients admitted to the neonatal intensive care unit (NICU) were evaluated.

METHODS

A cost-effectiveness ambispective analysis study was carried out, comparing (i) UC-pH combined with APGAR score and (ii) APGAR score only in 399 term pregnancies with a high risk for neonatal asphyxia. Costs included implementation, medical, and admission costs. Incremental cost-effectiveness ratios (ICER) were calculated. The proportions of patients admitted to the NICU were evaluated.

RESULTS

UC-pH combined with APGAR score demonstrated a cost-effective outcome (3990.64 USD vs 5545.11 USD) and an ICER shown as saving 103.66 USD compared to the APGAR score alone. The need for NICU admission was less in the umbilical cord blood collection group (18 vs 33 cases).

CONCLUSION

A combination of UC-pH with APGAR score assessment for neonatal asphyxia in a high-risk term pregnancy can effectively reduce costs and requirement for NICU admission.

Association of maternal, fetal and labor variables with a low Apgar score in the fifth minute in term pregnancy: a case-control study

PURPOSE

To search for maternal, labor-related and fetal variables associated with low Apgar in the fifth minute in term pregnancy.

METHODS

A retrospective case-control study with term births was conducted in a public teaching hospital from 2013 to 2020. Cases were term births with Apgar score less than 7 in the fifth minute, and controls, the next one or two births following a case, with Apgar of 7 or more. Non-cephalic presentations, multiples and malformations were excluded. We accessed 100 cases and 190 controls. We considered significant values of p < 0.05.

RESULTS

Were accessed 27 variables which could be risk factors, from which 12 were associated with the outcome. We found a protective effect of prelabor cesarean for the outcome, odds ratio (OR) 0.38, p = 0.013. Consequently, we conducted two sets of analyses: in the whole group and in the group of laboring women. The values of OR were in general greater in the group of laboring women, compared with the whole group. We conducted multivariate analysis within the group of women in labor. The variables which fitted best in the model were nulliparity, male sex of the fetus, less than six prenatal visits and abnormal cardiotocography; all remained significant. An association of rupture of membranes more than 360 min with the outcome, even after controlling fpr duration of labor, was found; adjusted OR 2.45, p = 0.023.

CONCLUSION

Twelve variables were associated with the outcome. Prelabor cesarean had a protective effect. The time of ruptured membranes was associated with low Apgar.

A comparison of criteria for defining metabolic acidemia in live-born neonates and its effect on predicting serious adverse neonatal outcomes

BACKGROUND

Metabolic acidemia is a known risk factor for serious adverse neonatal outcomes in both preterm and term infants.

OBJECTIVE

This study aimed to evaluate the clinical significance of delivery umbilical cord gas measurements with regard to serious adverse neonatal outcomes, and to determine if distinct thresholds for defining metabolic acidemia differ in their ability to predict such adverse neonatal complications.

STUDY DESIGN

This is a retrospective cohort study of singleton live-born deliveries between January 2011 and December 2019. Stratification according to gestational age at birth (≥35 and <35 weeks of gestation) was performed, and comparisons of maternal characteristics, obstetrical complications, intrapartum events, and adverse neonatal outcomes were made between neonates with metabolic acidemia and those without. Metabolic acidemia (based on delivery umbilical cord gas analyses) was defined using both American College of Obstetricians and Gynecologists and Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria. The primary outcome of interest was hypoxic-ischemic encephalopathy requiring whole-body hypothermia.

RESULTS

A total of 91,694 neonates born at ≥35 weeks of gestation met the inclusion criteria. By American College of Obstetricians and Gynecologists criteria, 2659 (2.9%) infants had metabolic acidemia. Neonates with metabolic acidemia were at markedly increased risk for neonatal intensive care unit admission, seizures, need for respiratory support, sepsis, and neonatal death. Metabolic acidemia by American College of Obstetricians and Gynecologists criteria was associated with an almost 100-fold increased risk of hypoxic-ischemic encephalopathy requiring whole-body hypothermia (relative risk, 92.69; 95% confidence interval, 64.42-133.35) in neonates born at ≥35 weeks of gestation. Diabetes mellitus, hypertensive disorders of pregnancy, postterm deliveries, prolonged second stages, chorioamnionitis, operative vaginal deliveries, placental abruption and cesarean deliveries were associated with metabolic acidemia in neonates born ≥ 35 weeks of gestation. The highest relative risk was in those diagnosed with placental abruption (relative risk, 9.07; 95% confidence interval, 7.25-11.36). The neonatal cohort born <35 weeks of gestation had similar findings. When comparing those infants born ≥ 35 weeks of gestation with metabolic acidemia by American College of Obstetricians and Gynecologists criteria vs Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria, the Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria identified more neonates at risk for serious adverse neonatal outcomes. In particular, 4.9% more neonates were diagnosed with metabolic acidemia, and 16 more term neonates were identified as requiring whole-body hypothermia. Mean 1-minute and 5-minute Apgar scores were similar and reassuring among neonates born at ≥35 weeks of gestation with and without metabolic acidemia as defined by both American College of Obstetricians and Gynecologists and Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria (8 vs 8 and 9 vs 9, respectively; P<.001). Sensitivity and specificity were 86.7% and 92.2%, respectively, with the Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria, and 74.2% and 97.2% with the American College of Obstetricians and Gynecologists criteria.

CONCLUSION

Infants with metabolic acidemia identified on cord gas collection at delivery are at considerably greater risk of serious adverse neonatal outcomes, including an almost 100-fold increased risk of hypoxic-ischemic encephalopathy requiring whole-body hypothermia. Use of the more sensitive Eunice Kennedy Shriver National Institute of Child Health and Human Development criteria for defining metabolic acidemia identifies more neonates born at ≥35 weeks of gestation at risk for adverse neonatal outcomes, including hypoxic-ischemic encephalopathy requiring whole-body hypothermia.

Umbilical cord pH, blood gases, and lactate at birth: normal values, interpretation, and clinical utility

Normal birth is a eustress reaction, a beneficial hedonic stress with extremely high catecholamines that protects us from intrauterine hypoxia and assists in the rapid shift to extrauterine life. Occasionally the cellular O2 requirement becomes critical and an O2 deficit in blood (hypoxemia) may evolve to a tissue deficit (hypoxia) and finally a risk of organ damage (asphyxia). An increase in H+ concentration is reflected in a decrease in pH, which together with increased base deficit is a proxy for the level of fetal O2 deficit. Base deficit (or its negative value, base excess) was introduced to reflect the metabolic component of a low pH and to distinguish from the respiratory cause of a low pH, which is a high CO2 concentration. Base deficit is a theoretical estimate and not a measured parameter, calculated by the blood gas analyzer from values of pH, the partial pressure of CO2, and hemoglobin. Different brands of analyzers use different calculation equations, and base deficit values can thus differ by multiples. This could influence the diagnosis of metabolic acidosis, which is commonly defined as a pH <7.00 combined with a base deficit ≥12.0 mmol/L in umbilical cord arterial blood. Base deficit can be calculated as base deficit in blood (or actual base deficit) or base deficit in extracellular fluid (or standard base deficit). The extracellular fluid compartment represents the blood volume diluted with the interstitial fluid. Base deficit in extracellular fluid is advocated for fetal blood because a high partial pressure of CO2 (hypercapnia) is common in newborns without concomitant hypoxia, and hypercapnia has a strong influence on the pH value, then termed respiratory acidosis. An increase in partial pressure of CO2 causes less increase in base deficit in extracellular fluid than in base deficit in blood, thus base deficit in extracellular fluid better represents the metabolic component of acidosis. The different types of base deficit for defining metabolic acidosis in cord blood have unfortunately not been noticed by many obstetrical experts and organizations. In addition to an increase in H+ concentration, the lactate production is accelerated during hypoxia and anaerobic metabolism. There is no global consensus on definitions of normal cord blood gases and lactate, and different cutoff values for abnormality are used. At a pH <7.20, 7% to 9% of newborns are deemed academic; at <7.10, 1% to 3%; and at <7.00, 0.26% to 1.3%. From numerous studies of different eras and sizes, it can firmly be concluded that in the cord artery, the statistically defined lower pH limit (mean -2 standard deviations) is 7.10. Given that the pH for optimal enzyme activity differs between different cell types and organs, it seems difficult to establish a general biologically critical pH limit. The blood gases and lactate in cord blood change with the progression of pregnancy toward a mixed metabolic and respiratory acidemia because of increased metabolism and CO2 production in the growing fetus. Gestational age-adjusted normal reference values have accordingly been published for pH and lactate, and they associate with Apgar score slightly better than stationary cutoffs, but they are not widely used in clinical practice. On the basis of good-quality data, it is reasonable to set a cord artery lactate cutoff (mean +2 standard deviations) at 10 mmol/L at 39 to 40 weeks' gestation. For base deficit, it is not possible to establish statistically defined reference values because base deficit is calculated with different equations, and there is no consensus on which to use. Arterial cord blood represents the fetus better than venous blood, and samples from both vessels are needed to validate the arterial origin. A venoarterial pH gradient of <0.02 is commonly used to differentiate arterial from venous samples. Reference values for pH in cord venous blood have been determined, but venous blood comes from the placenta after clearance of a surplus of arterial CO2, and base deficit in venous blood then overestimates the metabolic component of fetal acidosis. The ambition to increase neonatal hemoglobin and iron depots by delaying cord clamping after birth results in falsely acidic blood gas and lactate values if the blood sampling is also delayed. Within seconds after birth, sour metabolites accumulated in peripheral tissues and organs will flood into the central circulation and further to the cord arteries when the newborn starts to breathe, move, and cry. This influence of "hidden acidosis" can be avoided by needle puncture of unclamped cord vessels and blood collection immediately after birth. Because of a continuing anaerobic glycolysis in the collected blood, it should be analyzed within 5 minutes to not result in a falsely high lactate value. If the syringe is placed in ice slurry, the time limit is 20 minutes. For pH, it is reasonable to wait no longer than 15 minutes if not in ice. Routine analyses of cord blood gases enable perinatal audits to gain the wisdom of hindsight, to maintain quality assurance at a maternity unit over years by following the rate of neonatal acidosis, to compare results between hospitals on regional or national bases, and to obtain an objective outcome measure in clinical research. Given that the intrapartum cardiotocogram is an uncertain proxy for fetal hypoxia, and there is no strong correlation between pathologic cardiotocograms and fetal acidosis, a cord artery pH may help rather than hurt a staff person subjected to a malpractice suit based on undesirable cardiotocogram patterns. Contrary to common beliefs and assumptions, up to 90% of cases of cerebral palsy do not originate from intrapartum events. Future research will elucidate whether cell injury markers with point-of-care analysis will become valuable in improving the dating of perinatal injuries and differentiating hypoxic from nonhypoxic injuries.

AACC Guidance Document on the Use of Point-of-Care Testing in Fertility and Reproduction

Background

The AACC Academy revised the reproductive testing section of the Laboratory Medicine Practice Guidelines: Evidence-Based Practice for Point-of-Care Testing (POCT) published in 2007.

Methods

A panel of Academy members with expertise in POCT and laboratory medicine was formed to develop guidance for the use of POCT in reproductive health, specifically ovulation, pregnancy, premature rupture of membranes (PROM), and high-risk deliveries. The committee was supplemented with clinicians having Emergency Medicine and Obstetrics/Gynecology training.

Results

Key recommendations include the following. First, urine luteinizing hormone (LH) tests are accurate and reliable predictors of ovulation. Studies have shown that the use of ovulation predicting kits may improve the likelihood of conception among healthy fertile women seeking pregnancy. Urinary LH point-of-care testing demonstrates a comparable performance among other ovulation monitoring methods for timing intrauterine insemination and confirming sufficient ovulation induction before oocyte retrieval during in vitro fertilization. Second, pregnancy POCT should be considered in clinical situations where rapid diagnosis of pregnancy is needed for treatment decisions, and laboratory analysis cannot meet the required turnaround time. Third, PROM testing using commercial kits alone is not recommended without clinical signs of rupture of membranes, such as leakage of amniotic fluid from the cervical opening. Finally, fetal scalp lactate is used more than fetal scalp pH for fetal acidosis due to higher success rate and low volume of sample required.

Conclusions

This revision of the AACC Academy POCT guidelines provides recommendations for best practice use of POCT in fertility and reproduction.

Evidence-based labor management: third stage of labor (part 5)

During the third stage of labor, oxytocin and tranexamic acid, oxytocin and misoprostol, oxytocin and methylergometrine, or carbetocin is recommended for the prevention of postpartum hemorrhage after vaginal delivery. Intravenous oxytocin (10 IU) immediately after delivery of the neonate (after either anterior shoulder or whole-body delivery) and before delivery of the placenta is recommended. If oxytocin and tranexamic acid combination is chosen, intravenous tranexamic acid (1 g) in addition to intravenous oxytocin (10 IU) immediately after delivery of the neonate and before placental delivery is recommended. If oxytocin and misoprostol combination is chosen, sublingual misoprostol (400 µg) in addition to intravenous oxytocin (10 IU) immediately after delivery of the neonate is recommended. If there is no intravenous access or if in low-resource settings, sublingual misoprostol (400 µg) and intramuscular oxytocin (10 IU) are recommended. If oxytocin and methylergometrine combination is chosen, intramuscular methylergometrine (0.2 mg) and intravenous oxytocin (10 IU) immediately after delivery of the neonate are recommended. Single-dose intravenous or intramuscular carbetocin (100 µg) immediately after delivery of the neonate is recommended. Controlled cord traction and delayed cord clamping for approximately 60 seconds is recommended. There is insufficient evidence to support or refute umbilical cord milking, uterine massage, or nipple stimulation for the prevention of postpartum hemorrhage. Repair of first- and second-degree lacerations with continuous synthetic suture technique is recommended. No repair of first-degree lacerations if hemostatic and normal cosmesis can be considered. Repair of third-degree lacerations with end-to-end or overlap continuous synthetic suture technique is recommended. Repair of fourth-degree lacerations with delayed absorbable 4-0 or 3-0 polyglactin or chromic suture in a running fashion is recommended. The use of single-dose second-generation cephalosporin at the time of third- or fourth-degree laceration repairs can be considered. Skin-to-skin contact after delivery is recommended. There is insufficient evidence to support or refute routine cord blood gas sampling after delivery. Public cord blood banking is recommended.

[Predictive value of umbilical arterial cord pH on complications during hospitalization in neonates after cesarean section]

OBJECTIVE

To analyze the predictive value of umbilical arterial cord pH on complications of hospitalized neonates after cesarean section.

METHODS

This was a retrospective cohort study and carried out in Peking University First Hospital from January 1, 2017 to June 30, 2017. Neonates who were delivered by cesarean section were enrolled. The primary endpoint was the incidence of complications during in-hospital stay (including infection, aspiration pneumonia, myocardial damage, etc.). The subjects were divided into two groups:with or without complication. The umbilical arterial cord pH values were compared between the two groups. Perinatal baseline characteristics of maternal and neonatal data were recorded. The ROC curve was used to analyze the value of umbilical arterial cord pH in predicting neonatal complications during hospitalization. Multivariate Logistic regression was employed to analyze the potential risk factors of neonatal complications.

RESULTS

In the study, 872 neonates were included in the final analysis (541 in elective surgery and 331 in emergency surgery). The overall incidence of neonatal complications during hospitalization was 14.1%. The first three higher incidences were infection, aspiration pneumonia and myocardial damage. The average pH value in neonates without complication was 7.31 while 7.29 in neonates with complication. There was statistical significance between the two groups (P<0.001). The overall incidence of pH≤7.20 was 3.1% (27/872). The patients in neonates without complication had higher incidence of pH≤7.20 than those in neonates with complication (1.6% vs. 12.2%, P<0.001). Multivariate Logistic regression showed 6 risk factors of neonatal hospitalized complications including preterm delivery (OR=8.224, 95%CI: 4.910-13.777, P<0.001), pregnancy-induced hypertension (OR=1.886, 95%CI: 1.004-3.546, P=0.049), intrauterine growth restriction (OR=4.429, 95%CI: 1.280-15.330, P=0.019), emergency cesarean section (OR=2.711, 95%CI: 1.682-4.369, P<0.001), umbilical arterial blood gas pH≤7.20 (OR=7.420, 95%CI: 2.951-18.655, P<0.001) and 5-minute Apgar score <10 scores (OR=11.849, 95%CI: 3.977-35.128, P<0.001). The areas under the ROC curve of umbilical arterial blood gas pH in all neonatal, elective and emergency cesarean section were 0.570 (95%CI: 0.508-0.633, P=0.012), 0.559 (95%CI: 0.465-0.652, P=0.189) and 0.617 (95%CI: 0.538-0.697, P=0.002), respectively.

CONCLUSION

Umbilical arterial cord pH≤7.20 was related with increased incidence of neonatal complications after cesarean section,but ROC curve analysis showed a lower predictive value.

Re-examining the arterial cord blood gas pH screening criteria in neonatal encephalopathy

OBJECTIVE

Screening criteria for neonatal encephalopathy remain a complex combination of subjective and objective criteria. We examine the utility of universal cord blood gas testing and mandatory encephalopathy evaluation for infants with pH ≤7.10 on umbilical cord arterial blood gas (cABG) as a single screening measure for timely identification of moderate/severe encephalopathy.

DESIGN, SETTING, PATIENTS

Infants born at a single centre between 2008 and 2015, who were ≥36 weeks, had no congenital anomalies and had a cABG pH ≤7.10 were identified for a retrospective cohort study. Maternal/perinatal and patient factors were collected.

RESULTS

27 028 infants were born during the study period; 412 met all inclusion criteria. Of those, 35/85 infants with pH <7.00 and 34/327 infants with pH between 7.00 and 7.10 had moderate/severe encephalopathy. Encephalopathy was identified on the basis of pH and examination alone (no other perinatal criteria present) in 5/35 and 13/34 infants in the two pH groups, respectively.A cABG pH threshold of ≤7.10 was associated with a sensitivity of 74.2% and a specificity of 98.7% for detection of moderate/severe encephalopathy. Based on these data, 25 infants with cABG pH between 7.00 and 7.10 will need to be screened to identify one neonate with moderate/severe encephalopathy, who might have otherwise been missed using conventional screening, a 15% increase in appropriate selection and treatment over current methods.

CONCLUSION

Universal cord blood gas screening with a pH threshold ≤7.10 and mandatory encephalopathy examination results in greater detection of infants with moderate/severe encephalopathy and timely initiation of therapeutic hypothermia.