Preductal Arterial Blood Research Articles

Index of Suspicion in the Nursery

A 3,915-g term infant is born to a 19-year-old primi gravida. The mother has received regular prenatal care and her pregnancy is uneventful. She is negative for HIV, syphilis, and hepatitis B and is Rubella immune. She smoked marijuana during pregnancy, but denies any other substance abuse. She ruptures her membranes 14 hours before the delivery and has clear amniotic fluid. The infant is delivered by normal spontaneous vaginal delivery, which is complicated by shoulder dystocia. Apgar scores are 5, 7, and 9 at 1, 5, and 10 minutes, respectively. Soon after delivery, the infant is noted to have subcostal retractions. Clinical examination reveals an appropriately grown term infant who has tachypnea and subcostal retractions. Her right arm is noted to be extended and internally rotated with pronated forearm. She is also noted to have a large left-sided parieto-occipital scalp swelling. The rest of the examination is normal. Pulse oximetry measurement on the right hand shows 81% to 82% saturations in room air. The infant is transferred to ICU and is started on 40% supplemental oxygen, 2 L per minute by nasal cannula. The oxygen concentration is gradually increased to 100%, but the saturations remain in low 80s. A preductal arterial blood gas on 100% oxygen showed a pH 7.29, PCO2 47, PO2 50, and base excess of −4. In view of the persistent hypoxemia and desaturations, she is endotracheally intubated and mechanically ventilated. Blood is drawn for culture and complete blood cell count and she is commenced on ampicillin and gentamicin. The clinical findings along with the chest radiograph (Fig) suggest the diagnosis. Further investigations confirm the suspicion. Figure. Chest radiograph of the infant prior to intubation. …

Prediction of outcome in infants with congenital diaphragmatic hernia or severe diaphragmatic eventration.

Congenital diaphragmatic hernia (CDH) and severe congenital diaphragmatic eventration (SDE) still have high mortality. Our aims were to identify clinical prognostic factors for CDH and SDE, and to determine whether the size or area of the proximal bilateral pulmonary arteries (PA) correlate with the clinical outcome. We retrospectively analyzed medical charts of 26 patients--20 with CDH and 6 with SDE, but no obvious other associated anomalies--admitted over a 12-year period. We compared prenatal history, clinical manifestations, blood gas, and echocardiography before surgery in the survivors and the non-survivors. Ten patients (8 CDH, 2 SDE) died 2 to 16 days after birth, including 2 patients without surgery due to progressive hypoxemia. The survivors had significantly higher 1- and 5-min Apgar scores, higher the worst preductal arterial blood gas pH levels, lower oxygen indices, and lower PaCO2 (P < 0.05). The McGoon index of PA size measured by echocardiography was higher in survivors, but not statistically significant. Nakada PA index results, however, were statistically significant (93.07 +/- 32.02 vs. 121.07 +/- 27.08, P < 0.05) In conclusion, Apgar scores, preductal PaCO2, oxygen index, and pH level can predict prognosis in infants with CDH and SDE. The Nakada PA index, however, might be a useful prognostic marker for patients with CDH and SDE.

Correlation between fetal scalp blood samples and intravascular blood pH, pO2 and oxygen saturation measurements

Objective: This study was designed to compare the values of blood gases in local scalp blood, obtained by scalp blood sampling, with direct measurements of fetal preductal arterial blood in fetalsheep.Methods: Six fetal lambs were catheterized in the brachial artery and vein. Maternal oxygenation was reduced in steps from a fractional inspired oxygen concentration (FiO2)of 20 to 5% by addition of nitrogen to the inhaled gas mixture. Fetal scalp and arterial blood were sampled simultaneously at maternal FiO2 step intervals after maternal FiO2and oxygen were stable for > 5 min. Blood pH, pO2 and oxygen saturation were measured and linear regression was performed to determine the correlation between these values.Results:Scalp pH correlated well with arterial pH, whereas scalp pO2, pCO2 and oxygen saturation did not. However, when a secondary analysis was performed taking into accountthe effects of aerobic contamination, scalp pCO2, pO2 and oxygen saturation became highly correlated with arterial values.Conclusions: Local scalp blood oxygensaturation correlates highly with fetal preductal arterial values, when physiological artifacts are eliminated. The technique of scalp blood sampling introduces error into oxygenation saturation measurements,owing to difficulties in anaerobic sample collection. These results suggest that continuous measurement of fetal scalp oxygenation by noninvasive oximetry may be superior to direct sampling of scalp blood.

Prenatal diagnosis of congenital diaphragmatic hernia and pulmonary hypoplasia and therapeutic strategy

The outcome of fetuses with congenital diaphragmatic hernia (CDH) has been reported to be fatal when pulmonary hypoplasia (PH) is severe. As an indicator of PH, we attempted to measure the lung-thorax transverse area ratio (L/T) using ultrasonic echography. Immediate postnatal surgery was performed using high-frequency oscillatory ventilation (HFOV) and sometimes followed by extracorporeal membrane oxygenation (ECMO). Eighteen fetuses were treated and 14 survived. L/T correlated well with the best preductal arterial blood gas data before surgical reduction during manual ventilation and HFOV, while preductal PO2 and alveolar-arterial oxygen differences from patients managed with HFOV were better than those in patients with manual ventilation. Although L/T also correlated with the duration of O2 therapy and hospitalization in survivors without major anomalies, there was no significant difference between L/T in survivors and nonsurvivors. Because delayed institution of ECMO and complications related to ECMO management seemed to be a major cause of death in non-survivors, the unsalvageable L/T due to PH was estimated to be below 0.06 for HFOV and below 0.1 for conventional ventilation based on the correlation between L/T and preductal P02. These results suggest that L/T is a useful indicator of PH in patients with CDH and also that HFOV is advantageous in treating CDH with PH. The advantage of prenatal diagnosis in predicting unsalvageable L/Ts, should be considered in the therapeutic strategy.

The relationship between oxygen saturation and pH in umbilical blood: Implications for intrapartum fetal oxygen saturation monitoring

OBJECTIVE: Our purpose was to evaluate the relationship between umbilical arterial blood oxygen saturation determined by hemoximetry (Sao2) and umbilical arterial blood pH and base excess determined by blood gas analysis to establish a ″critical threshold” for fetal preductal arterial oxygen saturation determined by reflectance pulse oximetry (Spo2). STUDY DESIGN: Umbilical artery and vein blood specimens were obtained at delivery. Blood gas analysis and hemoximetry were performed. Polynomial regression analysis and receiver-operator characteristic curves were calculated for umbilical arterial blood Sao2 and theoretic preductal arterial blood Sao2 versus umbilical arterial blood pH and base excess. RESULTS: A total of 1101 paired umbilical artery and vein specimens were obtained. When the umbilical arterial blood Sao2 was ≥30%, umbilical arterial blood pH was ≥7.13 in 99.0% (388/392) of cases and <7.13 in 1.0% (4/392) of cases. When umbilical arterial blood Sao2 was <30%, umbilical arterial blood pH was ≥7.13 in 91.4% (648/709) of cases and <7.13 in 8.6% (61/709) of cases. CONCLUSIONS: From these analyses, it appears that an Spo2 cutoff value of 30% would be reasonable in clinical trials of intrapartum fetal pulse oximetry. (Am J Obstet Gynecol 1996;175:682-7.)

Catecholamine and serotonin concentrations in fetal guinea-pig brain: relation to regional cerebral blood flow and oxygen delivery in the growth-restricted fetus.

To test the hypothesis that intrauterine growth restriction (IUGR) would lead to altered neurotransmitter metabolism in the brain because of poorer oxygenation, blood flows and tissue concentrations of noradrenaline, dopamine, serotonin and their metabolites were measured in 14 parts of the brain of guinea-pig fetuses at 61-64 days' gestation. Eight fetuses with IUGR induced by uterine artery ligation were compared with 8 controls. Regional brain blood flows were determined by the microsphere method and tissue concentrations of monoamines by HPLC with electrochemical detection. The oxygen content of preductal arterial blood was significantly lower in IUGR fetuses than in controls (2.3 +/- 0.6 v. 3.5 +/- 0.5 mM; P < 0.001). Although this was compensated by increases in blood flow to many areas of the brain, significant decreases occurred in oxygen delivery to the temporal and occipital cortex, hippocampus and cerebellum of IUGR fetuses. In contrast, oxygen delivery to brainstem areas was maintained. Noradrenaline concentrations were closely similar in brains from the two groups, except for an increase in the caudate nucleus of IUGR fetuses. Dopamine concentrations were significantly elevated in brainstem areas. Concentrations of 3,4-dihydroxyphenylglycol (DOPEG), a noradrenaline metabolite, and 3,4-dihydroxyphenylacetic acid (DOPAC), a dopamine metabolite, showed a similar pattern of increase in brains of IUGR fetuses, possibly resulting from increased synthesis of noradrenaline and dopamine rather than from decreased degradation. Concentrations of serotonin were significantly higher in frontal and temporal cortex of IUGR fetuses, and the serotonin metabolite 5-HIAA increased significantly in cortical areas. Changes in neurotransmitter metabolism could not be related to oxygen supply, since serotonin concentrations increased in the forebrain, despite reduced oxygen delivery and the known dependence of tryptophan-5-hydroxylase on tissue PO2, and dopamine levels were elevated in the brainstem, where the oxygen supply was maintained.

Cerebral glucose utilization during aerobic metabolism in fetal sheep.

Extract: The relative utilization rates of glucose and oxygen by the fetal brain were evaluated by measuring simultaneously arteriovenous differences of glucose (Δ glucose) and oxygen (Δ oxygen) across the cerebral circulation of 10 fetal sheep. The mean ± 1 SEM Δ glucose was 0.197 ± 0.012 mM, and the Δ oxygen was 1.11 ± 0.08 mM. Preductal arterial blood was obtained from the brachiocephalic artery; cerebral venous blood was obtained from the fetal sagittal sinus up to 6 days following surgery. A glucose/oxygen quotient was calculated to determine the fraction of cerebral oxygen consumption required to metabolize the glucose utilized by the brain to CO2 and H2O. This quotient was 1.06 with 95% confidence limits of 1.12 and 1.02. These data indicate that glucose can supply all the aerobic metabolic requirements of the fetal brain. Speculation: Although glucose seems to be the primary substrate of cerebral metabolism, the amount of glucose acquired by the fetal lamb via the umbilical circulation can satisfy, at most, one-half of the total fetal aerobic needs. Thus the fetal brain seems much more dependent on glucose than do other fetal organs, and may be particularly vulnerable to periods of hypoglycemia.