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

Amnioinfusion for potential or suspected umbilical cord compression in labour

BACKGROUND

Amnioinfusion aims to prevent or relieve umbilical cord compression during labour by infusing a solution into the uterine cavity.

OBJECTIVES

To assess the effects of amnioinfusion for potential or suspected umbilical cord compression on maternal and perinatal outcome .

SEARCH METHODS

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (31 October 2011).

SELECTION CRITERIA

Randomised trials of amnioinfusion compared with no amnioinfusion in women with babies at risk of umbilical cord compression in labour.

DATA COLLECTION AND ANALYSIS

The original review had one author only (Justus Hofmeyr (GJH)). For this update, two authors (GJH and T Lawrie) assessed 13 additional trial reports for eligibility and quality. We extracted data and checked for accuracy.

MAIN RESULTS

We have included 19 studies, with all but two studies having fewer than 200 participants. Transcervical amnioinfusion for potential or suspected umbilical cord compression was associated with the following reductions: caesarean section overall (13 trials, 1493 participants; average risk ratio (RR) 0.62, 95% confidence interval (CI) 0.46 to 0.83); fetal heart rate (FHR) decelerations (seven trials, 1006 participants; average RR 0.53, 95% CI 0.38 to 0.74); Apgar score less than seven at five minutes (12 trials, 1804 participants; average RR 0.47, 95% CI 0.30 to 0.72); meconium below the vocal cords (three trials, 674 participants, RR 0.53, 95% CI 0.31 to 0.92); postpartum endometritis (six trials, 767 participants; RR 0.45, 95% CI 0.25 to 0.81) and maternal hospital stay greater than three days (four trials, 1051 participants; average RR 0.45, 95% CI 0.25 to 0.78). Transabdominal amnioinfusion showed similar trends, though numbers studied were small.Mean cord umbilical artery pH was higher in the amnioinfusion group (seven trials, 855 participants; average mean difference 0.03, 95% CI 0.00 to 0.06) and there was a trend toward fewer neonates with a low cord arterial pH (less than 7.2 or as defined by trial authors) in the amnioinfusion group (eight trials, 972 participants, average RR 0.58, 95% CI 0.29 to 1.14).

AUTHORS' CONCLUSIONS

The use of amnioinfusion for potential or suspected umbilical cord compression may be of considerable benefit to mother and baby by reducing the occurrence of variable FHR decelerations, improving short-term measures of neonatal outcome, reducing maternal postpartum endometritis and lowering the use of caesarean section, although there were methodological limitations to the trials reviewed here. In addition, the trials are too small to address the possibility of rare but serious maternal adverse effects of amnioinfusion. More research is needed to confirm the findings, assess longer-term measures of fetal outcome, and to assess the impact on caesarean section rates when the diagnosis of fetal distress is more stringent. Trials should assess amnioinfusion in specific clinical situations, such as FHR decelerations, oligohydramnios or prelabour rupture of membranes.

Obstetric approaches to the prevention of meconium aspiration syndrome

Meconium aspiration syndrome (MAS) is associated with increased risk for perinatal mortality and morbidities. To provide an overview of the advances in our knowledge concerning the obstetric approaches to the prevention of MAS. The evidence of the effectiveness of intrapartum surveillance, amnioinfusion, and delivery room management in the prevention of MAS are reviewed in the present paper. Meconium aspiration syndrome remains one of the most common but challenging conditions for obstetricians and pediatricians. The available evidence did not demonstrate a beneficial effect of either of obstetric strategies in the prevention of MAS.

Meconium-stained liquor during labor is associated with raised neonatal cord blood 8-iso-prostaglandin F2alpha concentration

OBJECTIVE

The purpose of this study was to compare the umbilical arterial 8-iso-prostaglandin F2alpha, concentrations between pregnancies that were complicated by moderate or thick meconium-stained liquor and those with clear liquor.

STUDY DESIGN

Umbilical cord arterial blood samples were collected from 247 singleton pregnancies with either moderate or thick meconium-stained liquor at any stage of labor or clear liquor at all stages of labor for the determination of the total 8-iso-prostaglandins F2alpha concentration.

RESULTS

The median total 8-iso-prostaglandins F2alpha concentration of the meconium-stained liquor group was significantly higher than that of the control group (719.2 vs 115.8 pg/mL). Among the meconium-stained liquor group, those who had a change from "clear liquor" at early labor to "moderate/ thick meconium-stained liquor" at late first stage or at delivery (late meconium-stained liquor group) had higher 8-iso-prostaglandins F2alpha concentration, compared with those who had moderate/ thick meconium-stained liquor since early labor (early meconium-stained liquor group; 959.8 vs 499.9 pg/mL). With the use of multiple regression analysis, meconium-stained liquor, duration of second stage of labor, and abnormal fetal heart tracings were independent determinants of cord blood 8-iso-prostaglandins F2alpha concentration.

CONCLUSION

Moderate or thick meconium-stained liquor is an independent factor for increased oxidative stress in pregnancy.

Prophylactic transcervical amnioinfusion in laboring women with oligohydramnios

OBJECTIVES

Evaluation of prophylactic intrapartum amnioinfusion in women with oligohydramnios.

METHODS

Assiut University Hospital during the period from February 2000 to September 2001, 160 laboring women with oligohydramnios [amniotic fluid index (AFI) </=5 cm] were randomized into: amnioinfusion and control groups. Inclusion criteria were: term singleton gestation, vertex presentation, cervical dilatation <4 cm, and assuring fetal heart rate (FHR). Trans-cervical amnioinfusion was done with warmed normal saline.

RESULTS

there was a significant increase in AFI after amnioinfusion (P<0.001). The amnioinfusion group showed lower cesarean section rate for fetal distress (P=0.003), lower incidence of abnormal FHR (P=0.006), fewer neonates with Apgar score <7 at 1 min (P<0.001), and 5 min (P=0.009), meconium below vocal cords (P<0.001), umbilical arterial pH<7.1 (P=0.003), and significantly shorter hospital stay (P=0.02).

CONCLUSION

Prophylactic trans-cervical amnioinfusion is a simple, safe and effective procedure.

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.

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.