Lipid peroxidation in cord blood: the effect of amniotic fluid volume

A study of oxidative stress in neonates delivered through meconium-stained amniotic fluid

To estimate the levels of malondialdehyde (MDA) and 8-hydroxy-2-deoxyguanosine (8-OH-dG) in cord blood plasma of newborns born through meconium-stained amniotic fluid (MSAF) and also to find out the correlation between their levels with birth weight and gestation, we measured the cord blood plasma levels of MDA and 8-OH-dG in 59 newborns born through MSAF and 50 newborns born through clear liquor. The levels of cord blood plasma MDA and 8-OH-dG were significantly higher in full-term and late-preterm newborns born through MSAF. On further comparison, it was found that both full-term and late-preterm intrauterine growth restricted (IUGR) neonates had higher levels of these markers as compared to babies born as appropriate for gestational age (AGA) through MSAF. Plasma levels of MDA and 8-OH-dG were significantly correlated with birth weight even after controlling the relationship with gestational age for all cases as well as all full-term cases. These markers are also significantly correlated to each other.

CONCLUSIONS

The present study suggest that the neonates born through MSAF experience higher degrees of oxidative stress, as evidenced by increased levels of cord blood plasma MDA and 8-OH-dG. What is known: • Aspirated meconium has been found to induce free radical generation and cellular damage in animal studies. • Its role in free radical generation and oxidative damage in human neonates is scarce. What is new: • Neonates born through meconium-stained amniotic fluid experience significant oxidative stress.

Supplementary oxygen for emergency Caesarean section under regional anaesthesia

BACKGROUND

Controversy still exists if the administration of supplementary oxygen to patients having emergency Caesarean section (CS) under regional anaesthesia is beneficial or potentially harmful. Therefore, in a prospective double-blinded study, we randomized patients having emergency CS under regional anaesthesia to receive either air or 60% oxygen until delivery and compared the effects on fetal oxygenation and lipid-peroxidation in the mother and baby.

METHODS

We recruited 131 women having emergency CS under regional anaesthesia. Either 21% (air group) or 60% oxygen (oxygen group) was administered using a Venturi-type facemask until delivery. We compared the oxygen exposure duration, umbilical arterial (UA) and venous (UV) blood gases and oxygen content, and plasma concentration of 8-isoprostane. Subanalysis was performed according to whether or not fetal compromise was considered present.

RESULTS

Data from 125 patients were analysed. For the oxygen group vs the air group, there were greater values for UA PO(2) [mean 2.2 (SD 0.5) vs 1.9 (0.6) kPa, P=0.01], UA O(2) content [6.6 (2.5) vs 4.9 (2.8) ml dl(-1), P=0.006], UV PO(2) [3.8 (0.8) vs 3.2 (0.8) kPa, P<0.0001], and UV O(2) content [12.9 (3.5) vs 10.4 (3.8) ml dl(-1), P=0.001]. There was no difference between the groups in maternal, UA, or UV 8-isoprostane concentration. Apgar scores and UA pH were similar between the groups. Similar changes were observed regardless of whether fetal compromise was considered present (n=37) or not (n=88).

CONCLUSIONS

Breathing 60% oxygen during emergency CS under regional anaesthesia increased fetal oxygenation with no associated increase in lipid-peroxidation in the mother or fetus.

Lipid peroxidation in cord blood and neonatal outcome

BACKGROUND

Periventricular-intraventricular hemorrhage, necrotizing enterocolitis, chronic lung disease and retinopathy of prematurity have been referred to as oxygen radical diseases (ORD) because they are thought to be related to excess oxidant stress relative to anti-oxidant defenses in premature infants. 8-Isoprostane is a product of lipid peroxidation that can be used as a measure of free radical exposure or injury. The aim of the present study was to determine whether fetal oxidant stress is associated with adverse effects in preterm infants.

METHODS

Mothers delivering at gestational age <37 weeks were recruited. Umbilical arterial and venous cord blood samples were collected and 8-isoprostane levels measured. Levels of 8-isoprostane in cord blood were correlated with maternal and perinatal variables, neonatal mortality, and the development of one or more ORD.

RESULTS

Umbilical cord venous, but not arterial, 8-isoprostane levels were associated with mortality and the development of one or more of the ORD. After controlling for gestational age, for each unit change in the log value of 8-isoprostane in venous cord blood the odds of mortality were 12 (95% confidence interval [CI]: 1-223) and oxygen radical disease were 2.7 (95%CI: 1-7.2). Isoprostane levels were not related to gender, method of delivery, use of maternal magnesium or steroids, pregnancy-induced hypertension, or delivery room resuscitation.

CONCLUSION

Oxidant stress in utero may be an important determinant of mortality and morbidity in preterm infants. Elevated umbilical venous isoprostane levels suggest that oxidative injury to maternal and placental tissues predispose to adverse neonatal outcomes.

Relationship between umbilical cord morphology and nuchal cord entanglement

OBJECTIVE

To determine whether tightening of nuchal cord entanglement is more likely to occur where normal cord coiling is absent and there is deficient Wharton's jelly. The study was carried out in the delivery suite of a university teaching hospital, using a prospective matched controlled-pairs survey.

METHODS

Midwives identified index cases with nuchal cord entanglement at the time of delivery. The next delivery of equivalent gestation (+/- 1 week) without cord entanglement was taken as the control. Only singleton pregnancies with cephalic presentation undergoing spontaneous labor were studied. Placental insertion, nuchal entanglement (tight or loose), length, presence of knots, umbilical coiling index (UCI), and the amount of Wharton's jelly were recorded.

RESULTS

Longer cords were more frequent amongst male infants and were predisposed towards entanglement. There were no significant differences in the amount of Wharton's jelly, or in the UCI between tight and loose nuchal cord groups. The only measurement that differed significantly was the total cord length, with shorter cords predisposed towards tightening.

CONCLUSION

Whilst nuchal cord entanglement amongst male babies is frequently associated with long and straight umbilical cords, tightening is more likely to occur if the cord is of short or normal length. Neither low UCI nor low percentage of Wharton's jelly are predisposed towards tightening of cord entanglement.

Effects of high inspired oxygen fraction during elective caesarean section under spinal anaesthesia on maternal and fetal oxygenation and lipid peroxidation

BACKGROUND

Oxygen supplementation is given routinely to parturients undergoing Caesarean section under regional anaesthesia. While the aim is to improve fetal oxygenation, inspiring a high oxygen fraction (FIO2) can also increase free radical activity and lipid peroxidation in both the mother and baby. In this prospective, randomized, double-blind study, we investigated the effect of high inspired oxygen fraction (FIO2) on maternal and fetal oxygenation and oxygen free radical activity in parturients having Caesarean section under spinal anaesthesia.

METHODS

Forty-four healthy parturients were randomized to breathe either 21% (air group) or 60% oxygen (oxygen group) intraoperatively via a ventimask. Maternal arterial blood was collected at 5-min intervals from baseline until delivery, and umbilical arterial and venous blood was collected at delivery. We measured blood gases and the products of lipid peroxidation (8-isoprostane, malondialdehyde (MDA), hydroperoxide (OHP)) and purine metabolites.

RESULTS

At delivery, the oxygen group had greater maternal arterial PO2 [mean 30.0 (SD 6.3) vs 14.2 (1.9) kPa; mean difference 15.8 kPa, 95% confidence interval 12.9-18.7 kPa, P<0.001] and greater umbilical venous PO2 [4.8 (1.0) vs 4.0 (1.4) kPa; mean difference 0.8 kPa, 95% confidence interval 0.0-1.5 kPa, P=0.04] compared with the air group. Maternal and umbilical plasma concentrations of lipid peroxides (8-isoprostane, MDA, OHP) were greater in the oxygen group than in the air group (P<0.05).

CONCLUSIONS

We conclude that breathing high FIO2 modestly increased fetal oxygenation but caused a concomitant increase in oxygen free radical activity in both mother and fetus.

Oxidative stress in the fetal lamb brain following intermittent umbilical cord occlusion: a path analysis

OBJECTIVE

To evaluate the relative contribution of cord occlusion length intervals between occlusions and experimental duration on oxidative stress in the fetal lamb brain.

DESIGN

Acute, partially exteriorised fetal lambs with intermittent total cord occlusion.

SETTING

The Vivarium of Westmead Hospital, University of Sydney, Australia and The Chinese University of Hong Kong.

MAIN OUTCOME MEASURES

Arterio-venous differences in the concentration of organic hydroperoxides, measured in paired samples of carotid arterial and jugular venous blood, as an index of oxidative stress in the brain.

METHODS

Thirty-two fetal lambs were exposed to graded hypoxia, induced by intermittent total umbilical cord compression of 30 seconds, 60 seconds and 90 seconds duration, occurring every minute for a total of 27 occlusions over 81 minutes. Three sham experiments were also performed. In addition to organic hydroperoxides, carotid arterial blood samples were also assayed in 15 animals (two sham) for oxygen saturation, pH, hypoxanthine, xanthine and urate concentrations. A causal model for oxidative stress was defined: occlusions leading to hypoxia with a rise in hypoxanthine; reperfusion during intervals between occlusions leading to the accelerated production of xanthine and uric acid and the generation of oxygen free radicals, which in turn, are responsible for the rise in lipid peroxidation. Path analysis was performed to assess the strength of the relationships between these variables and the cord occlusion length, the interval between occlusions and the duration of the experiment.

RESULTS

Sham experiments showed no change in organic hydroperoxide production. Following 30-second umbilical cord occlusions a sixfold drop in mean organic hydroperoxides was observed between carotid arterial and jugular venous levels. In contrast, following occlusions of 60 seconds duration (or longer) a median 20-fold increase in organic hydroperoxide production was observed. Path analysis revealed a strong indirect pathway from occlusion length --> hypoxanthine --> urate and weak positive pathways from oxygen saturation --> urate and from interval between occlusions --> urate. After accounting for these pathways reflecting oxidative stress, a strong direct path remained from time from first occlusion --> organic hydroperoxide production.

CONCLUSIONS

Peroxidation of lipids in the brain occurs under conditions of severe hypoxia and reperfusion associated with intermittent umbilical cord occlusions of 60 seconds or longer. The path analysis supported the causal model as originally defined, with the exception that the indirect pathway via pH was found to be trivial.

Umbilical cord vascular cell adhesion molecule concentration following labor

OBJECTIVE

This study was designed to determine if VCAM concentrations are increased in serum from neonates delivered vaginally compared to those delivered by cesarean in the absence of labor at term.

METHODS

Serum was collected from umbilical cords immediately after delivery of term uncomplicated pregnancies either prior to onset of labor by scheduled cesarean or following labor. VCAM concentration was determined by commercial ELISA.

RESULTS

Mean VCAM concentration was significantly higher in the laboring (1,106.2 +/- 279 ng/ml) than the nonlaboring group (906.9 +/- 217 ng/ml, P = 0.01).

CONCLUSIONS

Increases in neonatal serum VCAM concentrations may represent a response to enhanced lipid peroxidation and oxidative stress during labor as well as a component of the normal fetal immune response.

Determinants of umbilical cord arterial 8-iso-prostaglandin F2alpha concentrations

OBJECTIVE

To determine the concentration of 8-isoPGF(2alpha) in cord blood as a measure of oxidative stress during labour, and to compare them with other established parameters of in vivo lipid peroxidation and with the acid-base status of the newborn.

METHOD

Umbilical cord arterial and venous blood samples were collected from 81 singleton term deliveries for determination of 8-isoPGF(2alpha), malondialdehyde and organic hydroperoxides. In addition, metabolites derived from the oxidative metabolism of purines during hypoxia-reoxygenation and routine cord blood of oxygen saturation, pH, pO2, pCO2, HCO3 and base excess were measured.

RESULTS

Arterial concentrations of 8-isoPGF(2alpha) were significantly higher in cases with fetal distress, tight nuchal cord (P < 0.001), the umbilical coiling index, and male sex (P < 0.05) (R2 = 0.48). No correlation was found with any parameter of acid-base status. In arterial and venous blood the concentrations of organic hydroperoxides and hypoxanthine significantly correlated with the fetal nuchal cord (P < 0.001) (R2 = 0.26 and 0.16, respectively).

CONCLUSION

Our findings indicate that 8-isoPGF2(alpha) in cord arterial blood is a suitable parameter to quantify a possible oxidative stress in the fetus during labour. Measurements of the F2-isoprostane concentrations in cord blood at labour provide a clinically useful method to assess the perinatal outcome.

A comparison of three ultrasound estimates of intrapartum oligohydramnios for prediction of fetal hypoxia-reperfusion injury

A prospective observational study assessed the predictive value of three techniques for amniotic fluid volume assessment on umbilical cord arterial lipid peroxide levels and acid-base balance. Women with singleton, term, cephalic presentation, and an initially normal fetal heart rate tracing were recruited. All pregnancies had the largest vertical pocket (LVP), two diameter pocket (2phi), and amniotic fluid index (AFI) assessments before and after amniotomy and cord arterial acid-base and lipid peroxide determinations at delivery. In 171 cases with confirmed cord arterial samples, malondialdehyde (MDA), organic hydroperoxide (OHP), pH and base excess (BE) were examined in relationship to intrapartum LVP, 2phi and AFI before and after amniotomy. Improvements in correlation between the estimates of amniotic fluid volume and outcome measures were observed 30 min after amniotomy, particularly with lipid peroxide measurements. Examination of scatter-plots using Lowess regression suggested that the correlation was only valid in cases of oligohydramnios but that the cutoff values recommended in the literature for defining oligohydramnios were not appropriate in our population sample. We suggest that oligohydramnios should be defined as an AFI < 8 cm or LVP < 4 cm. We concur with the recommendation of < 15 cm2 for the 2phi measurement.

Intrapartum fetal hypoxia and biochemical markers: a review

Intrapartum fetal hypoxia is a rare event, although fetal intrapartum surveillance is discussed as a subject of major importance. This is mainly because of consequences of fetal hypoxia that may lead to cerebral palsy. A fetus suffering from hypoxia initially compensates by producing energy through anaerobic metabolism. At some stage, the fetus becomes decompensated and basic cellular functions fail, with risks of permanent morbidity or mortality. How long a fetus can survive on anaerobic metabolism differs because metabolic reserves differ, i.e., growth-restricted fetuses might deteriorate at an earlier stage. An increasing body of evidence has clarified brain-damaging mechanisms. Neuronal loss occurs in two phases: during the primary hypoxic event and later during the reperfusion/reoxygenation phase. Animal studies have suggested the possibility of prophylactic treatment to prevent neuronal loss after the hypoxic event. Intrapartum diagnostic tools should aim for detecting fetal hypoxemia/hypoxia when the fetus is still compensated. This may be achieved by assessment of biochemical data such as pH, lactate, and oxygen saturation, with the aim of prophylactic intervention before the fetus becomes decompensated. The measurement of cord blood levels of oxygen free radicals and excitatory amino acids at the time of birth may prove to be helpful in determining the risk of brain damage and evaluating the effect of prophylactic treatments to prevent or ameliorate brain injury from hypoxia.

Lipid peroxidation in cord blood at birth: the effect of labour

OBJECTIVE

To determine the effect of labour on free oxygen radical activity in the fetus, as reflected by lipid peroxide levels in umbilical cord arterial blood.

DESIGN

Prospective, observational study.

SETTING

Department of Obstetrics and Gynaecology, The Chinese University of Hong Kong.

METHODS

Umbilical cord arterial and venous blood samples were collected from singleton term infants delivered by elective caesarean section. Base excess, PO2, pCO2 and pH were measured in both samples and compared to identify double venous samples. Cord arterial acid-base balance and concentrations of organic hydroperoxides and malondialdehyde were compared with those obtained from normal vaginal deliveries.

RESULTS

Cord arterial blood samples, obtained from cases of uncomplicated labour followed by spontaneous vaginal delivery, had significantly higher lipid peroxide concentrations than those delivered following elective caesarean section. This was most marked for malondialdehyde with a median value increased by 105%, whilst organic hydroperoxide was increased by only 27%. Of the acid-base parameters, base excess was increased by 78%, with only minimal changes in pH, pCO2 and PO2. These differences remained highly significant after including other pregnancy characteristics in multivariate analysis.

CONCLUSION

The findings indicate that high levels of free oxygen radical activity in the fetus are a function of the labour process, as are changes in acid-base balance.

Lipid peroxidation in cord blood: a randomised sequential pairs study of prophylactic saline amnioinfusion for intrapartum oligohydramnios

OBJECTIVE

To determine the efficacy of prophylactic intrapartum amnioinfusion in reducing cord arterial lipid peroxide levels in cases of intrapartum oligohydramnios.

DESIGN

Sequential randomised pairs trial.

SETTING

Delivery suite of a teaching hospital, the Chinese University of Hong Kong.

POPULATION

Women with singleton, term pregnancy, cephalic presentation, clear amniotic fluid and an amniotic fluid index < or = 5 cm, with a normal intrapartum fetal heart rate tracing within 30 minutes of amniotomy.

METHODS

Selected patients were randomised either for prophylactic saline amnioinfusion or as control cases. Cord arterial lipid peroxide concentrations and acid base balance were determined at delivery.

MAIN OUTCOME MEASURES

Operative intervention for fetal distress, cord arterial malondialdehyde and organic hydroperoxide levels, pH and base excess.

RESULTS

Amnioinfusion was associated with significant reductions in the incidence of operative delivery for fetal distress and in lipid peroxide levels, an increase in base excess, but no significant alteration in pH.

CONCLUSIONS

Oligohydramnios in labour is associated with high levels of lipid peroxidation, reflecting cellular damage by release of free radicals following hypoxia reperfusion. Prophylactic intrapartum saline amnioinfusion is an effective technique for the reduction of lipid peroxidation and of the incidence of operative intervention for fetal distress but has no significant effect on overall operative delivery rates.