Umbilical Lactate Research Articles

Measurement Of Umbilical Venous Lactate Levels For Predicting Poor Neonatal Outcomes

Objectives: To determine the utility of umbilical venous lactate measurements for predicting poor neonatal outcomes. Method: This observational study was conducted at Kahuta Research Laboratories (KRL) hospital, Islamabad from May 2019 to October 2019. Singleton pregnancies with no known fetal congenital anomalies and gestational age greater than 28 weeks were included. Descriptive statistics were used to analyse the characteristics of study subjects and also composite neonatal outcomes. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were calculated. Result: Umbilical venous lactate levels were found to be highest in instrumental deliveries (48.7%) and lowest in those delivered by elective cesarean section (25.7%). Low APGAR score, need for initial resuscitation & neonatal intensive care unit admission, mechanical ventilation and neonatal morbidity were all associated with significantly higher lactate levels. Based on the maximal yield index, the optimal cut-off point for predicting neonatal morbidity was 46.5mg/dl (area under the receiver operating characteristics curve was 0.8). Based on this optimal cut-off point, it has a sensitivity of 62%, specificity of 92%, PPV 51% and NPV 94% for neonatal morbidity. Conclusion: Umbilical venous lactate measurement is a good predictor of poor neonatal outcome especially in situations when umbilical arterial blood cannot be taken due to technical difficulty. Mode of delivery has a strong association with fetal hypoxia and raised umbilical lactate levels. Keywords: lactate, neonatal outcomes, labour ward.

Umbilical arterial lactate levels after normal vaginal and elective cesarean delivery: The role of a longer active second stage most significant in high levels after vaginal delivery.

To evaluate umbilical arterial lactate concentrations after spontaneous vaginal delivery and after elective Cesarean delivery, and to study the simultaneous effects of maternal and obstetric variables in high lactate levels in vaginally delivered healthy term singletons. The birth register study included information about the umbilical artery lactate values and clinical perinatal data from 7723 women and their singleton newborns (7301 spontaneous vaginal and 422 elective cesareans) from Kuopio University Hospital, Finland. High lactate levels were evaluated more extensively among healthy term neonates (N = 6541), to evaluate high levels after normal vaginal labors. The mean lactate level was significantly lower after elective cesarean compared to vaginal delivery (2.42 [0.94] vs. 3.56 [1.62] mmol/l; p < 0.0001). Consequently, the 90th percentile limit values were 3.60 and 5.80 mmol/L. Among healthy term newborns born vaginally, higher lactate values (≥5.80 mmol/L) were independently associated with a longer duration of the active second stage of labor (ORs 1.91-10.97) and duration of ruptured fetal membranes (ORs 1.36-2.46), higher gestational age at birth (ORs 1.41-1.86), null parity (OR 2.17), maternal infection (OR 1.81) and short maternal stature (OR 1.45). We report 90th/95th limits for umbilical arterial lactate values in relation to the various durations of labors for term newborns who are delivered by the vaginal route. Even though the high umbilical lactate levels may indicate serious birth asphyxia, levels after vaginal birth reflect the physiological stress and subclinical transient asphyxia frequently seen in normal vaginal deliveries.

Umbilical cord arterial blood gas and lactate for predicting neonatal short term outcome

目的 研究新生儿脐血血气和乳酸对新生儿生后24 h内早期结局的预测作用。 方法 对2016年4月至2017年4月在北京新世纪妇儿医院产科出生的1 375例胎龄35周(及以上)无明显先天畸形的单胎活产新生儿进行前瞻性研究，生后1 min内进行脐血血气和乳酸检测，并观察新生儿生后24 h内的早期结局指标：是否复苏，1 min、5 min Apgar评分，是否入住新生儿病房，有无严重不良结局(插管、机械通气，新生儿窒息、缺氧缺血性脑病、胎粪吸入综合征，死亡)。 结果 胎龄35～41周(平均39周)，脐血血气多元回归分析显示乳酸与pH、BE呈负相关(P 0.05)。 结论 单独乳酸水平的监测可以作为简易的脐血血气指标予以应用。新生儿脐血pH、BE和乳酸水平均可以预测新生儿是否需要复苏，但不能预测早期严重不良结局。

Management of intra-partum foetal hypoxia due to prolonged second stage labour in a pug puppy

A two year old female pug was presented to University Veterinary Hospital Kokkalai with difficulty in whelping The animal was subjected to detailed clinico gynaecological examination and ultrasonography The second puppy was delivered per vaginally with the administration of ecbolics Based on history clinical examination Apgar scoring and umbilical lactate values the condition of the neonate was diagnosed as intra partum foetal hypoxia due to prolonged expulsion time of the foetus After drying the puppy oxygen therapy was initiated with the help of a face mask at the rate of L min and the neonates was maintained in an incubator maintained at C The neonate had an uneventful recovery

Umbilical Lactate as a Measure of Acidosis and Predictor of Neonatal Risk: A Systematic Review

(BJOG 2017;124:584–594) Testing for acidosis at all deliveries is advocated by some as an early and effective way to identify infants at risk for a range of adverse neonatal outcomes. A low umbilical artery potential of hydrogen (pH) has been associated with poor outcomes such as cerebral palsy, encephalopathy, and death. While acidosis is not the direct cause of these negative outcomes and most acidotic newborns suffer no adverse effects, knowledge of the presence of the acidosis may allow clinicians to alter their treatment in an attempt to improve outcomes.

The introduction of umbilical cord lactate measurement and associated neonatal outcomes in a South African tertiary hospital labor ward

Purpose: To investigate the utility of umbilical artery (UA) lactate measurements in a South African hospital for assessing intrapartum care and predicting neonatal outcomes.Materials and methods: From 3 March–12 November 2014, we conducted a prospective cohort study of UA lactate levels at Kalafong Hospital, Pretoria, South Africa. Following birth, a UA blood sample (<0.5uL) was taken from a double-clamped segment of cord and the lactate measured. Maternal and neonatal characteristics and outcomes were recorded.Results: During the study, there were 4668 deliveries; including 1091 emergency cesarean and 154 instrumental deliveries. A lactate was recorded for 946 deliveries (20.3%). 190 babies required neonatal resuscitation, with an optimal cutoff for lactate of 5.45 mmol/L (sensitivity 68%, specificity 72%). 124 babies required nursery admission with the optimal cutoff for lactate 4.95 mmol/L (sensitivity 61%, specificity 59%). 55 babies had an Apgar score <7 at 5 min and the optimal lactate for this outcome was 5.65 mmol/L (sensitivity 64%, specificity of 69%).Conclusions: Umbilical lactate can be used in a middle-low resource setting as a measurement of intrapartum hypoxia, with reasonable sensitivity and specificity for the prediction of, or need for, resuscitation, admission to the nursery, and low Apgar scores.

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.

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

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. To synthesise the evidence on accuracy of umbilical cord lactate in measuring acidosis and predicting poor neonatal outcome. Studies published and unpublished between 1990 and 2014 from PubMed/Medline, EMBASE, Cochrane Central Register of Controlled Trials, and clinicaltrials.gov were assessed. Cross-sectional and randomised studies that assessed fetal acidosis (using lactate as the index test) with or without an assessment of neonatal outcome. 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. 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 5minutes (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%). 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. Umbilical cord lactate: a clinically applicable, inexpensive, effective way to measure intrapartum acidosis.

Closed‐loop double‐vasopressor automated system vs manual bolus vasopressor to treat hypotension during spinal anaesthesia for caesarean section: a randomised controlled trial

Hypotension necessitating vasopressor administration occurs commonly during caesarean section under spinal anaesthesia. We developed a novel vasopressor delivery system that automatically administers phenylephrine or ephedrine based on continuous non-invasive arterial pressure monitoring. A phenylephrine bolus of 50 μg was given at 30-s intervals when systolic blood pressure fell < 90% of baseline; an ephedrine bolus of 4 mg was given instead if systolic pressure fell < 90% of baseline together with a heart rate < 60 beats.min(-1). The control group used manual boluses of either phenylephrine 100 μg or ephedrine 8 mg, administered at 1-min intervals based on the same thresholds for systolic pressure and heart rate. This randomised, controlled, double-blinded trial involved 213 healthy women who underwent elective caesarean delivery under spinal anaesthesia using 11 mg hyperbaric bupivacaine with 15 μg fentanyl and 100 μg morphine. The automated vasopressor group had better systolic pressure control, with 37/106 (34.9%) having any beat-to-beat systolic pressure reading < 80% of baseline compared with 63/107 (58.9%) in the control group (p < 0.001). There was no difference in the incidence of reactive hypertension, defined as systolic pressure > 120% of baseline, with 8/106 (7.5%) in the automated vasopressor group vs 14/107 (13.1%) in the control group, or total dose of vasopressors. The automated vasopressor group had lower median absolute performance error of 8.5% vs control of 9.8% (p = 0.013), and reduced incidence of nausea (1/106 (0.9%) vs 11/107 (10.3%), p = 0.005). Neonatal umbilical cord pH, umbilical lactate and Apgar scores were similar. Hence, our system afforded better control of maternal blood pressure and reduced nausea with no increase in reactive hypertension when compared with manual boluses.

The effect of time, temperature and storage device on umbilical cord blood gas and lactate measurement: a randomized controlled trial

Objective: Umbilical cord blood gas analysis has a significant and growing role in early neonatal assessment. Factors often delay analysis of cord blood allowing values to change. Consequently, this study evaluates the impact of time, temperature and method of storage on umbilical blood gas and lactate analyses. Methods: Umbilical cord segments from 80 singleton deliveries were randomized to: cords at room temperature (CR), cords stored on ice (CI), syringes at room temperature (SR) or syringes stored on ice (SI). Analysis occurred every 15 minutes for one-hour. Mixed model analysis of variance allowing for repeated measures was utilized. Results: Cord arterial pH deteriorated in CR, CI, and SI within 15 minutes (p ≤ 0.001), with SR stable until 60 minutes (p = 0.002). Arterial pCO2 remained stable in SR and CI, increased in SI (p = 0.002; 45 minutes) and decreased in CR (p < 0.001; 45 minutes). Arterial base excess deteriorated in CR and SI (p ≤ 0.009; 15 minutes), SR (p < 0.001; 30 minutes), and CI (p < 0.001; 45 minutes). Arterial lactate levels increased within 15 minutes in all groups (p < 0.001). Conclusions: Cord blood gas values change rapidly after delivery. Smallest changes were seen in SR group. Data suggest that analyses should be conducted as soon as possible after 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.

Does lactate level in the first 12 hours of life predict mortality in extremely premature infants?

To determine if high lactate levels within the first 12 h of life independently or in combination with Clinical Risk Index for Babies (CRIB) II can predict mortality in extremely premature babies. A retrospective review of medical charts of babies born between 2001 and 2003 with birthweight <1000 g or gestation <28 weeks was performed. Blood gases and highest umbilical lactate levels in first 12 h of life were noted. Area under the curve (AUC) was calculated for lactate, CRIB and CRIB II as a predictor of mortality. The AUC for lactate and CRIB II were combined using discriminant analysis. Two hundred nineteen infants were included in the study, 41 (18.7%) of whom died. The AUC for lactate was 0.67 (P < 0.001), while AUCs for CRIB and CRIB II score were 0.81 (P < 0.001) and 0.82 (P < 0.001), respectively. The AUC for the combined measure of lactate and CRIB II was 0.82, similar to CRIB II. Lactate predicts mortality in premature infants, but was found to be inferior to CRIB and CRIB II. Adding lactate level to CRIB II score does not improve its predictive ability.

Prevention of cerebral palsy during labour: role of foetal lactate

Intrapartum foetal monitoring goal is to prevent foetal asphyxia and its most severe consequence: cerebral palsy (CP). In this paper we describe the detection methods and the criteria needed to assess asphyxia during labour for preventing CP. Foetal cerebral damage assessment is considered from the medical-legal point of view. CP represents the most frequent pathology of childhood related to pregnancy and childbirth with an incidence of 0.2% in children born alive. It is clinically regarded as the result of a spectrum of diseases due to damage or to faded development of the nervous system which generally appears at the time of the first stage of intra-uterine growth or depends on problems arising at birth. The goal of our analysis is to recall the various moments in which this event can take place and, if possible, the moment and the degree of the event of asphyxia and its effect on foetal conditions, in order to control and treat it. One hundred and eighty-eight fetuses were evaluated by means of Apgar score, intrapartum cardiotocography, observation of the presence of meconium stained amniotic fluid, and clinical features of distress at birth. Lactate concentrations were measured during labour and at delivery in blood samples obtained from the foetal presenting part (foetal scalp) and from the umbilical cord with the use of a rapid electrochemical technique. Evidence of clinical foetal distress was not related to the severity of asphyxia. An increased lactate level was found in asphyctic infants and a clear correlation between lactic acidosis and foetal distress was documented. Low Apgar scores were observed in infants with moderate or severe asphyxia at delivery. Scalp lactate correlated significantly with umbilical artery lactate (P = 0.49, 0.01), but with neither Apgar score at 1 min (R = -0.21, ns) nor at 5 min (R = -0.11, ns). Lactate concentration was higher in case of instrumental delivery compared to spontaneous delivery (P = 0.0001). No perfect correlation was found between lactate level and neonatal outcome, but there were not a significant number of neonates with immediate complications. The rate of instrumental delivery in the distress group was significantly higher than in that of the healthy fetuses (P < 0.01), so spontaneous labour was less frequently associated with foetal distress than instrumental delivery (P < 0.01). In the distress group, severe variable decelerations were generally recorded in the second stage of labour. The incidence of neonatal Apgar score </=7 in neonates with abnormal baseline foetal heart rate (FHR) was higher than in those with severe variable decelerations, mild variable decelerations, and transient tachycardia (P < 0.05). The duration of the active second stage of labour correlated significantly with the presence of foetal lactate (P < 0.001) at the time of crowning of foetal head, and the presence of lactate in umbilical cord blood at delivery (P < 0.001). Expulsion time >/=45 min, compared with a shorter active second stage, and acidaemia at birth implied larger arterial-venous lactate differences (P < 0.001). The presence of foetal lactate at crowning was also significantly associated with the level of umbilical arterial-venous lactate difference (P = 0.03). Analysis of the fetus should start with the assessment of lactates and acid-base balance. The method which revolutionized the techniques of foetal monitoring is undoubtedly represented by cardiotocography. However, likely most of neurological outcomes are not correlated with a perinatal event or with peripartum asphyxia. Approximately 10% of cases of CP would actually be due to perinatal asphyxia, and this percentage approaches approximately to 15% if we consider only newborns at term. This again confirms the weak association of a causal relationship between asphyxia and CP. In addition, available foetal suffering markers are vague and allow to identify only less than half of the effective cases of newborns which will develop CP.

Comparison of effects of rapid colloid loading before and after spinal anesthesia on maternal hemodynamics and neonatal outcomes in cesarean section

The effects of colloid loading after spinal anesthesia on hemodynamics in parturients during cesarean section have not been fully understood. This study tested the hypothesis that colloid loading after spinal blockade can reduce hypotension compared with preloading, and affect neonatal outcomes. A prospective, randomized, double-blinded study was performed in 54 healthy parturients (ASA I or II) undergoing elective cesarean section. Patients were randomly allocated into one of three groups to receive rapid infusion of 6% hydroxyethylstarch (HES) (70 kDa/0.5) before spinal anesthesia (15 ml x kg(-1), HES preload group, n = 18), or rapid infusion of HES after induction of spinal anesthesia (15 ml x kg(-1), HES coload group, n = 18), or no rapid infusion (control, n = 18). The incidence of hypotension, and the amount of ephedrine used to treat hypotension was compared. Neonatal outcomes were also assessed by pH, base excess, lactate concentration, and Apgar scores. The incidence of hypotension was significantly lower in HES preload and HES coload groups than control group (P < 0.01). Although systolic blood pressure decreased after spinal blockade in all groups, the lowest SBP after spinal blockade until delivery was significantly higher in fluid loading groups than control (P < 0.001). Similarly, total dose of ephedrine to treat hypotension was lower in fluid loading groups (P < 0.001). Umbilical cord pH, umbilical lactate concentration, and the incidence of neonates with Apgar score <7 were similar. Colloid loading after induction of spinal anesthesia was similarly effective in reducing hypo- tension compared with preloading in cesarean section.

Ontogenic and nutritionally induced changes in fetal metabolism in the horse.

1. Using the Fick principle and tracer methodology, the metabolic rates of chronically catheterized fetal foals (n = 24) were measured at different gestational ages during the second half of gestation and in response to maternal fasting for 36 h in late gestation (n = 4, term approximately 335 days). 2. Absolute rates of umbilical blood flow, fetal glucose utilization and umbilical uptake of oxygen (O2) and glucose increased from mid-gestation to 300 days and then plateauxed until term. The absolute rate of umbilical lactate uptake was significant after, but not before, 280 days of gestation. Weight specific rates of umbilical uptake and fetal utilization of glucose decreased progressively throughout the second half of gestation. 3. Weight specific rates of CO2 production from glucose carbon were also inversely correlated with gestational age. Umbilical lactate uptake per kilogram of fetus was lower after 320 days than between 281 and 300 days. In contrast, no gestational trends were observed in the weight specific rates of fetal O2 uptake and urea production. Glucose production by the fetal horse was negligible, even very close to term. 4. Maternal fasting for 36 h reduced the rate of umbilical uptake and utilization of glucose production but had no effect on the rates of endogenous glucose production and umbilical uptake of oxygen and lactate by the horse fetus. 5. The observations show that fetal metabolism is highly dependent on glucose in the horse compared to the sheep in mid- and late gestation. Different species therefore adopt different strategies in meeting the nutritional demands of the growing fetus during the second half of gestation.

Glucose, lactate and oxygen metabolism in the fetal pig during late gestation.

Using [U-14C]glucose tracer, rates of umbilical uptake, utilization and production of glucose, and of CO2 production from glucose carbon, were measured in seven chronically catheterized fetal pigs, when the sow was in the fed state, between 100 and 113 days of gestation (term, 114 +/- 2 days). At the same time, rates of umbilical O2 and lactate uptake were determined in all seven fetuses by the Fick principle. The mean fetal rates of umbilical glucose uptake, glucose utilization and CO2 production from glucose carbon were 38.4 +/- 4.2, 41.3 +/- 5.2 and 126.9 +/- 12.6 mumol min-1 (kg fetal body weight)-1, respectively (n = 7), No glucose production was therefore detected in the fetuses. Production of CO2 from glucose carbon accounted for 37.3 +/- 3.4% (n = 7) of the umbilical O2 uptake, which averaged 340 +/- 13 mumol min-1 kg-1 (n = 7). There was also significant umbilical lactate uptake in the fetal piglets when the sow was in the fed state (32.6 +/- 10.4 mumol min-1 kg-1, n = 7, P < 0.05). No significant changes in fetal glucose, O2 or lactate metabolism were observed with increasing age towards term. The fetal rates of glucose metabolism and of umbilical uptake of O2 and lactate were not correlated with fetal blood glucose level. Hence, glucose is used for both oxidative and non-oxidative metabolism in utero and is an important, although not the sole, source of carbon for metabolic processes in the fetal pig during late gestation.

Glucose and oxygen metabolism in the fetal foal during late gestation

With the use of [U-14C]glucose tracer methodology, the rates of umbilical uptake, utilization, oxidation, and production of glucose were determined in nine chronically catheterized fetal foals in the fed state between 268 and 325 days of gestation (term approximately 335 days). At the same time, the rates of umbilical O2 and lactate uptake were measured in all nine fetuses by Fick principle. The mean fetal rates of umbilical glucose uptake, glucose utilization, and CO2 production from glucose carbon were 36.9 +/- 2.5, 36.4 +/- 1.7, and 117.7 +/- 17.4 mumol.min-1.kg fetal body wt-1, respectively (n = 9). Endogenous glucose production was therefore negligible in the fetal foal in the fed state. Production of CO2 from glucose carbon accounted for 40.9 +/- 6.5% of the umbilical O2 uptake, which averaged 292 +/- 15 mumol.min-1.kg-1 (n = 9). No significant changes in fetal glucose or O2 metabolism were observed with increasing gestational age. The rates of umbilical glucose uptake, glucose utilization, and CO2 production from glucose carbon (P < 0.01), but not the rate of umbilical O2 uptake (P > 0.05), were positively correlated with the fetal blood glucose level. There was a significant umbilical lactate uptake in the fetuses older than 290 days (12.3 +/- 4.1 mumol.min-1.kg-1, n = 5, P < 0.05) but not in the younger animals (6.2 +/- 9.6 mumol.min-1.kg-1, n = 4, P > 0.05). Hence, glucose is used for both oxidative and nonoxidative metabolism in utero and is a major, although not the sole, oxidative substrate in the fetal foal during late gestation.

Is fetal acidosis in the human fetus maternogenic during labor? A reanalysis

The purpose of this study was to investigate whether maternogenic fetal acidosis can occur at the time of labor and delivery and to evaluate the extent of the possible maternal contribution to fetal acidosis. We have therefore determined fetal and maternal lactate concentrations and acid-base status under various conditions in 589 women at the end of gestation and during labor. The results show that metabolic acidosis develops in all fetuses because of increased production of lactic acidosis is primarily of fetal origin: 1) the umbilical arteriovenous lactate differences were positive and large in steady-state conditions as well as in depressed newborns; 2) the conditions that could produce a net transfer of lactate from the mother to the fetus, namely a positive maternofetal gradient of lactate and proton, were rarely observed; and 3) the correlation between fetal and maternal lactate levels was very weak, with regression coefficients decreasing from near steady-state conditions to acute stress conditions, indicating that the increase in lactate in the fetus and mother occurs independently. This correlation indicates also that increased maternal lactate production under conditions of labor and delivery can make a contribution by affecting the rate of net transfer from fetus to mother. This is possible in approximately 6% of the fetuses.

268 LACTATE UPTAKE BY THE FETAL AND NEONATAL SHEEP LIVER

In the fetal sheep, lactate is an important metabolic substrate and previous studies have shown placental lactate production and lactate uptake by the fetal liver. In the neonatal sheep, there is no placental lactate source and blood lactate concentrations are lower than in the fetus. To compare the importance of lactate as a substrate for fetal and neonatal liver metabolism, we measured lactate flux across the liver in 16 fetal sheep (mean gestational age 129 days) which had catheters chronically placed in the right or left hepatic vein, portal vein, descending aorta and umbilical vein and in 5 neonatal sheep (mean age 9 days) with similar catheters except for the umbilical vein. In addition, we measured umbilical lactate uptake in the fetal sheep. In the fetus, net hepatic lactate uptake was 5.0 mg/min/100 g. There was a linear correlation between hepatic and umbilical lactate uptake (r = 0.74, p < .005); hepatic uptake could account for nearly 90% of umbilical uptake, but hepatic lactate extraction was only 7.7% of hepatic lactate delivery (94.2 mg/min/100 g). In the neonate, net hepatic lactate uptake was more than twice the fetal rate (11.0 mg/min/100 g) and hepatic lactate extraction was 32.9% of hepatic lactate delivery (31.0 mg/min/100 g). Lactate is therefore an important substrate for both fetal and neonatal liver metabolism. Although lactate delivery to the neonatal liver decreases, increased hepatic extraction compensates so that hepatic lactate uptake actually increases. (Supported by HL24056.)

1263 LACTIC ACID TOLERANCE IN THE NON-HYPOXIC FETAL LAMB

Lactic acid is considered in contradictory ways: as a normal fetal nutrient or as an indicator of fetal distress. Fetal lactic acidemia has been induced experimentally by hypoxia, combining effects of hypoxia and lactic acidemia. We chose to separate these effects by infusing lactic acid into 14 late gestation fetal lambs via a continuous infusion technique, and into 5 lambs using a lactate clamp technique. Animals (Fetal Weight=3.5±0.2 kg) had catheters in the umbilical vein, fetal pedal artery, pedal vein and brachial vein, and, in 6 animals, the fetal hepatic vein. Animals were well oxygenated and well nourished after recovery for at least 7 days. Lactic acid infusion into the fetal brachial vein at an average of 20 mg/min for 90-180 min rapidly established a new metabolic steady state, increasing arterial lactate by 2.8±0.36 mM*, and decreasing arterial pH from 7.36±0.006 to 7.29±0.02*. Umbilical lactate uptake determined by the Pick Principle fell from 7.3±1.2 to 3.1±1.7 mg/min* during infusion, and fetal arterial glucose increased from 1.02±0.06 mM to 1.13±0.05 mM*, decreasing both umbilical glucose uptake from 18.2±1.4 to 14.9±2.7 mg/min* and umbilical glucose/oxygen quotient (GOQ) from .51±.05 to .39±.02*. During infusion, hepatic lactate/oxygen quotient rose from 0.31±0.08 to .77±.12*, and hepatic GOQ reversed from +0.33±.05 (consumption) to -0.56±0.27* (production). [*=p <0.05, paired].Rapid continuous fetal lactic acid infusion is well tolerated by the non-hypoxic fetal lamb, and alters fetal metabolism of glucose and lactic acid.