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

Evaluation of oxygen administration in cesarean section under spinal anesthesia via lung ultrasound and the oxygen reserve index

BACKGROUND

Respiratory functions may be impaired in cesarean section (C/S) delivery performed under spinal anesthesia (SA) and oxygen supplementation may be required. Therefore, we conducted a randomized controlled study aimed to evaluate the effects of different oxygen administrations in pregnant women on the lungs during C/S under SA using ultrasound and oxygen reserve index (ORI).

METHODS

We conducted a randomized, controlled, single-center study from May 1, 2021, to March 31, 2022. A total of 90 patients scheduled for C/S under SA were randomly divided into 3 groups. Following the SA, patients in group 0 were treated with room air, in Group 3 were administered 3 L/min O₂ with a nasal cannula (NC), in Group 6 were administered 6 L/min O₂ with a simple face mask. In addition to routine monitoring, ORI values were measured. Lung aeration was evaluated through the modified lung ultrasound score (LUS) before the procedure (T0), at minute 0 (T1), 20 (T2), and hour 6 (T3) after the procedure, and ∆LUS values were recorded.

RESULTS

After SA, the ORI values of Group 3 were higher than Group 0 at all times (p < 0.05), while the intraoperative 1st minute and the 10th, 25th and 40th minutes after delivery (p = 0.001, p = 0.027, p = 0.001, p = 0.019) was higher than Group 6. When the LUS values of each group were compared with the T0 values a decrease was observed in Group 3 and Group 6 (p < 0.001, p = 0.016). While ∆LUS values were always higher in Group 3 than in Group 0, they were higher only in T1 and T2 in Group 6.

CONCLUSION

We determined that it would be appropriate to prefer 3 L/min supplemental oxygen therapy with NC in C/S to be performed under SA.

Perinatal Outcome following the Suspension of Intrapartum Oxygen Treatment

OBJECTIVE

This study aimed to evaluate whether the suspension of intrapartum maternal oxygen supplementation for nonreassuring fetal heart rate is associated with adverse perinatal outcomes.

STUDY DESIGN

A retrospective cohort study, including all individuals that underwent labor in a single tertiary medical center. On April 16, 2020, the routine use of intrapartum oxygen for category II and III fetal heart rate tracings was suspended. The study group included individuals with singleton pregnancies that underwent labor during the 7 months between April 16, 2020, and November 14, 2020. The control group included individuals that underwent labor during the 7 months before April 16, 2020. Exclusion criteria included elective cesarean section, multifetal pregnancy, fetal death, and maternal oxygen saturation <95% during delivery. The primary outcome was defined as the rate of composite neonatal outcome, consisting of arterial cord pH <7.1, mechanical ventilation, respiratory distress syndrome, necrotizing enterocolitis, intraventricular hemorrhage grade 3/4, and neonatal death. The secondary outcome was the rate of cesarean and operative delivery.

RESULTS

The study group included 4,932 individuals, compared with 4,906 individuals in the control group. The suspension of intrapartum oxygen treatment was associated with a significant increase in the rate of composite neonatal outcome (187 [3.8%] vs. 120 [2.4%], p < 0.001), including the rate of abnormal cord arterial pH <7.1 (119 [2.4%] vs. 56 [1.1%], p < 0.01). A higher rate of cesarean section due to nonreassuring fetal heart rate was noted in the study group (320 [6.5%] vs. 268 [5.5%], p = 0.03).A logistic regression analysis revealed that the suspension of intrapartum oxygen treatment was independently associated with the composite neonatal outcome (adjusted odds ratio = 1.55 [95% confidence interval, 1.23-1.96]) while adjusting for suspected chorioamnionitis, intrauterine growth restriction, and recent coronavirus disease 2019 exposure.

CONCLUSION

Suspension of intrapartum oxygen treatment for nonreassuring fetal heart rate was associated with higher rates of adverse neonatal outcomes and urgent cesarean section due to fetal heart rate.

KEY POINTS

· The available data on intrapartum maternal oxygen supplementation are equivocal.. · Suspension of maternal oxygen for nonreassuring fetal heart rate during labor was associated with adverse neonatal outcomes.. · Oxygen treatment might still be important and relevant during labor..

Effect of maternal oxygen supplementation for parturient undergoing elective cesarean section by high-flow nasal oxygen compared with room air on fetal acidemia: study protocol for a randomized controlled trial

BACKGROUND

Maternal oxygen supplementation is usually used as an intrauterine resuscitation technique to prevent fetal hypoxia and acidemia during delivery. However, there has been a great deal of controversy regarding the effects of prophylactic maternal oxygen during cesarean section, during which the incidence of fetal acidemia seems to be higher compared with that during labor. High-flow nasal oxygen (HFNO) can improve oxygenation better in patients with high-flow oxygen airflow. The purpose of this study is to determine whether maternal oxygen supplementation with HFNO has a positive effect on fetal acidemia during cesarean section through umbilical arterial blood gas analysis.

METHOD

This prospective, single-center, randomized, double-blinded trial will enroll 120 patients undergoing cesarean section. Participants will be randomly assigned to the HFNO group or air group at a 1:1 ratio. For parturients in the HFNO group, the flow rate is 40L/min, and the oxygen is heated to 37℃ with humidity 100% oxygen concentration through the Optiflow high-flow nasal oxygen system. And for the air group, the flow rate is 2 L/min with an air pattern through the same device. The primary outcome was umbilical artery (UA) lactate. Secondary outcomes include UA pH, PO2, PCO2, BE, the incidence of pH < 7.20 and pH < 7.10, Apgar scores at 1 and 5 min, and neonatal adverse outcomes.

DISCUSSION

Our study is the first trial investigating whether maternal oxygen supplementation with HFNO can reduce the umbilical artery lactate levels and the incidence of fetal acidemia in cesarean section under combined spinal-epidural anesthesia.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05921955. Registered on 27 June 2023.

Maternal Oxygen Administration during Labor: A Controversial Practice

Oxygen administration to the mother is commonly performed during labor, especially in the case of a non-reassuring fetal heart rate, aiming to increase oxygen diffusion through the placenta to fetal tissues. The benefits and potential risks are controversial, especially when the mother is not hypoxemic. Its impact on placental gas exchange and the fetal acid-base equilibrium is not fully understood and it probably affects the sensible placental oxygen equilibrium causing a time-dependent vasoconstriction of umbilical and placental vessels. Hyperoxia might also cause the generation of radical oxygen species, raising concerns for the developing fetal cells. Moreover, this practice affects the maternal cardiovascular system, causing alterations of the cardiac index, heart rate and vascular resistance, and unclear effects on uterine blood flow. In conclusion, there is no evidence that maternal oxygen administration can provide any benefit in the case of a non-reassuring fetal heart rate pattern, while possible collateral effects warn of its utilization. Oxygen administration during labor should be reserved for cases of maternal hypoxia.

Oxygen and mechanical stretch in the developing lung: risk factors for neonatal and pediatric lung disease

Chronic airway diseases, such as wheezing and asthma, remain significant sources of morbidity and mortality in the pediatric population. This is especially true for preterm infants who are impacted both by immature pulmonary development as well as disproportionate exposure to perinatal insults that may increase the risk of developing airway disease. Chronic pediatric airway disease is characterized by alterations in airway structure (remodeling) and function (increased airway hyperresponsiveness), similar to adult asthma. One of the most common perinatal risk factors for development of airway disease is respiratory support in the form of supplemental oxygen, mechanical ventilation, and/or CPAP. While clinical practice currently seeks to minimize oxygen exposure to decrease the risk of bronchopulmonary dysplasia (BPD), there is mounting evidence that lower levels of oxygen may carry risk for development of chronic airway, rather than alveolar disease. In addition, stretch exposure due to mechanical ventilation or CPAP may also play a role in development of chronic airway disease. Here, we summarize the current knowledge of the impact of perinatal oxygen and mechanical respiratory support on the development of chronic pediatric lung disease, with particular focus on pediatric airway disease. We further highlight mechanisms that could be explored as potential targets for novel therapies in the pediatric population.

Intermittent maternofetal oxygenation during late gestation improved birthweight, neonatal growth, body symmetry, and muscle metabolism in intrauterine growth-restricted lambs

In humans and animals, intrauterine growth restriction (IUGR) results from fetal programming responses to poor intrauterine conditions. Chronic fetal hypoxemia elevates circulating catecholamines, which reduces skeletal muscle β2 adrenoceptor content and contributes to growth and metabolic pathologies in IUGR-born offspring. Our objective was to determine whether intermittent maternofetal oxygenation during late gestation would improve neonatal growth and glucose metabolism in IUGR-born lambs. Pregnant ewes were housed at 40 °C from the 40th to 95th day of gestational age (dGA) to produce IUGR-born lambs (n = 9). A second group of IUGR-born lambs received prenatal O2 supplementation via maternal O2 insufflation (100% humidified O2, 10 L/min) for 8 h/d from dGA 130 to parturition (IUGR+O2, n = 10). Control lambs (n = 15) were from pair-fed thermoneutral ewes. All lambs were weaned at birth, hand-reared, and fitted with hindlimb catheters at day 25. Glucose-stimulated insulin secretion (GSIS) and hindlimb hyperinsulinemic-euglycemic clamp (HEC) studies were performed at days 28 and 29, respectively. At day 30, lambs were euthanized and ex vivo HEC studies were performed on isolated muscle. Without maternofetal oxygenation, IUGR lambs were 40% lighter (P < 0.05) at birth and maintained slower (P < 0.05) growth rates throughout the neonatal period compared with controls. At 30 d of age, IUGR lambs had lighter (P < 0.05) hindlimbs and flexor digitorum superficialis (FDS) muscles. IUGR+O2 lambs exhibited improved (P < 0.05) birthweight, neonatal growth, hindlimb mass, and FDS mass compared with IUGR lambs. Hindlimb insulin-stimulated glucose utilization and oxidation rates were reduced (P < 0.05) in IUGR but not IUGR+O2 lambs. Ex vivo glucose oxidation rates were less (P < 0.05) in muscle from IUGR but not IUGR+O2 lambs. Surprisingly, β2 adrenoceptor content and insulin responsiveness were reduced (P < 0.05) in muscle from IUGR and IUGR+O2 lambs compared with controls. In addition, GSIS was reduced (P < 0.05) in IUGR lambs and only modestly improved (P < 0.05) in IUGR+O2. Insufflation of O2 also increased (P < 0.05) acidosis and hypercapnia in dams, perhaps due to the use of 100% O2 rather than a gas mixture with a lesser O2 percentage. Nevertheless, these findings show that intermittent maternofetal oxygenation during late gestation improved postnatal growth and metabolic outcomes in IUGR lambs without improving muscle β2 adrenoceptor content.

Dangers of hyperoxia

Oxygen (O2) toxicity remains a concern, particularly to the lung. This is mainly related to excessive production of reactive oxygen species (ROS). Supplemental O2, i.e. inspiratory O2 concentrations (FIO2) > 0.21 may cause hyperoxaemia (i.e. arterial (a) PO2 > 100 mmHg) and, subsequently, hyperoxia (increased tissue O2 concentration), thereby enhancing ROS formation. Here, we review the pathophysiology of O2 toxicity and the potential harms of supplemental O2 in various ICU conditions. The current evidence base suggests that PaO2 > 300 mmHg (40 kPa) should be avoided, but it remains uncertain whether there is an "optimal level" which may vary for given clinical conditions. Since even moderately supra-physiological PaO2 may be associated with deleterious side effects, it seems advisable at present to titrate O2 to maintain PaO2 within the normal range, avoiding both hypoxaemia and excess hyperoxaemia.

Fetal Hemodynamic Response to Maternal Oxygenation in Normal and Complicated Pregnancies

Maternal oxygenation (MO) is widely applied in obstetrics. Scholars have conducted numerous studies on maternal hyperoxygenation and have reported many theoretical and applied achievements and a number of different points of view. The main purpose of this article is to discuss the effect of maternal oxygenation on fetal circulation during normal and complicated pregnancies and to ascertain its potential side effects and research gaps in this field. In complicated pregnancies, the fetus may benefit from oxygen therapy. However, large randomized controlled trials and longitudinal studies are necessary to support the widespread application of maternal oxygenation in this context.

Evaluation of an Initiative to Decrease the Use of Oxygen Supplementation for Category II Fetal Heart Rate Tracings

OBJECTIVE

To examine compliance with a guideline to reduce exposure to supplemental oxygen for category II fetal heart rate (FHR) tracings in normally oxygenated laboring patients.

METHODS

All patients in labor in an urban academic medical center from January 1 to July 31, 2020 were assessed. The preintervention group included those who delivered from January 1 to March 19, 2020. On March 20, 2020, a new guideline took effect that recommended no maternal supplemental oxygen for category II FHR tracings. The postintervention group delivered from March 20 to July 31, 2020. Exclusion criteria were planned cesarean delivery, multiple gestations, delivery at less than 24 weeks of gestation, intrauterine fetal death, and patients who received supplemental oxygen for an oxygen saturation lower than 95%. The primary outcome was the percentage of patients who received oxygen in labor analyzed by control charts and the rules of special cause variation. Chi-squared and t tests were used for secondary outcome assessment. P<.05 was considered significant.

RESULTS

A total of 1,333 patients were included, 474 patients in the preintervention group and 859 in the postintervention group. Oxygen was administered to 22.6% of patients before guideline implementation, compared with 0.6% after the guideline. Special cause variation was detected with an 8-point shift starting the month that the guideline was implemented, indicating statistical significance. There were no differences in any studied secondary maternal or fetal outcomes, although our statistical power to detect differences in infrequent outcomes was limited.

CONCLUSION

This quality-improvement study demonstrated significant adherence to the guideline that supplemental oxygen would no longer be given to patients with category II FHR tracings in the absence of maternal hypoxemia, with no significant change in maternal or perinatal outcomes.

Interventions for Intrapartum Fetal Heart Rate Abnormalities

Intrapartum fetal heart rate (FHR) decelerations may represent interrupted oxygen transfer to the fetus. In many cases, these interruptions are transient and do not result in progressive fetal acidemia with risk for asphyxia and neurological compromise. When significant FHR decelerations are present, reversible causes of reduced fetal oxygen delivery should be considered and corrective measures should be undertaken to optimize oxygenation. In this review, we describe potential intrapartum causes of reduced fetal oxygen delivery and the efficacy of common interventions for an abnormal FHR tracing.

Target arterial PO2 according to the underlying pathology: a mini-review of the available data in mechanically ventilated patients

There is an ongoing discussion whether hyperoxia, i.e. ventilation with high inspiratory O2 concentrations (FIO2), and the consecutive hyperoxaemia, i.e. supraphysiological arterial O2 tensions (PaO2), have a place during the acute management of circulatory shock. This concept is based on experimental evidence that hyperoxaemia may contribute to the compensation of the imbalance between O2 supply and requirements. However, despite still being common practice, its use is limited due to possible oxygen toxicity resulting from the increased formation of reactive oxygen species (ROS) limits, especially under conditions of ischaemia/reperfusion. Several studies have reported that there is a U-shaped relation between PaO2 and mortality/morbidity in ICU patients. Interestingly, these mostly retrospective studies found that the lowest mortality coincided with PaO2 ~ 150 mmHg during the first 24 h of ICU stay, i.e. supraphysiological PaO2 levels. Most of the recent large-scale retrospective analyses studied general ICU populations, but there are major differences according to the underlying pathology studied as well as whether medical or surgical patients are concerned. Therefore, as far as possible from the data reported, we focus on the need of mechanical ventilation as well as the distinction between the absence or presence of circulatory shock. There seems to be no ideal target PaO2 except for avoiding prolonged exposure (> 24 h) to either hypoxaemia (PaO2 < 55-60 mmHg) or supraphysiological (PaO2 > 100 mmHg). Moreover, the need for mechanical ventilation, absence or presence of circulatory shock and/or the aetiology of tissue dysoxia, i.e. whether it is mainly due to impaired macro- and/or microcirculatory O2 transport and/or disturbed cellular O2 utilization, may determine whether any degree of hyperoxaemia causes deleterious side effects.

Impact of intrauterine fetal resuscitation with oxygen on oxidative stress in the developing rat brain

Use of maternal oxygen for intrauterine resuscitation is contentious because of the lack of evidence for its efficacy and the possibility of fetal harm through oxidative stress. Because the developing brain is rich in lipids and low in antioxidants, it remains vulnerable to oxidative stress. Here, we tested this hypothesis in a term pregnant rat model with oxytocin-induced fetal distress followed by treatment with either room air or 100% oxygen for 6 h. Fetal brains from both sexes were subjected to assays for biomarkers of oxidative stress (4-hydroxynonenal, protein carbonyl, or 8-hydroxy-2'-deoxyguanosine), expression of genes mediating oxidative stress, and mitochondrial oxidative phosphorylation. Contrary to our hypothesis, maternal hyperoxia was not associated with increased biomarkers of oxidative stress in the fetal brain. However, there was significant upregulation of the expression of select genes mediating oxidative stress, of which some were male-specific. These observations, however, were not accompanied by changes in the expression of proteins from the mitochondrial electron transport chain. In summary, maternal hyperoxia in the setting of acute uteroplacental ischemia-hypoxia does not appear to cause oxidative damage to the developing brain.

Maternal Oxygen Supplementation Compared With Room Air for Intrauterine Resuscitation: A Systematic Review and Meta-analysis

IMPORTANCE

Supplemental oxygen is commonly administered to pregnant women at the time of delivery to prevent fetal hypoxia and acidemia. There is mixed evidence on the utility of this practice.

OBJECTIVE

To compare the association of peripartum maternal oxygen administration with room air on umbilical artery (UA) gas measures and neonatal outcomes.

DATA SOURCES

Ovid MEDLINE, Embase, Scopus, ClinicalTrials.gov, and Cochrane Central Register of Controlled Trials were searched from February 18 to April 3, 2020. Search terms included labor or obstetric delivery and oxygen therapy and fetal blood or blood gas or acid-base imbalance.

STUDY SELECTION

Studies were included if they were randomized clinical trials comparing oxygen with room air at the time of scheduled cesarean delivery or labor in patients with singleton, nonanomalous pregnancies. Studies that did not collect paired umbilical cord gas samples or did not report either UA pH or UA Pao2 results were excluded.

DATA EXTRACTION AND SYNTHESIS

Data were extracted by 2 independent reviewers. The analysis was stratified by the presence or absence of labor at the time of randomization. Data were pooled using random-effects models.

MAIN OUTCOMES AND MEASURES

The primary outcome for this review was UA pH. Secondary outcomes included UA pH less than 7.2, UA Pao2, UA base excess, 1- and 5-minute Apgar scores, and neonatal intensive care unit admission.

RESULTS

The meta-analysis included 16 randomized clinical trials (n = 1078 oxygen group and n = 974 room air group). There was significant heterogeneity among the studies (I2 = 49.88%; P = .03). Overall, oxygen administration was associated with no significant difference in UA pH (weighted mean difference, 0.00; 95% CI, -0.01 to 0.01). Oxygen use was associated with an increase in UA Pao2 (weighted mean difference, 2.57 mm Hg; 95% CI, 0.80-4.34 mm Hg) but no significant difference in UA base excess, UA pH less than 7.2, Apgar scores, or neonatal intensive care unit admissions. Umbilical artery pH values remained similar between groups after accounting for the risk of bias, type of oxygen delivery device, and fraction of inspired oxygen. After stratifying by the presence or absence of labor, oxygen administration in women undergoing scheduled cesarean delivery was associated with increased UA Pao2 (weighted mean difference, 2.12 mm Hg; 95% CI, 0.09-4.15 mm Hg) and a reduction in the incidence of UA pH less than 7.2 (relative risk, 0.63; 95% CI, 0.43-0.90), but these changes were not noted among those in labor (Pao2: weighted mean difference, 3.60 mm Hg; 95% CI, -0.30 to 7.49 mm Hg; UA pH<7.2: relative risk, 1.34; 95% CI, 0.58-3.11).

CONCLUSIONS AND RELEVANCE

This systematic review and meta-analysis suggests that studies to date showed no association between maternal oxygen and a clinically relevant improvement in UA pH or other neonatal outcomes.

Effects of perioperative oxygen concentration on oxidative stress in adult surgical patients: a systematic review

BACKGROUND

The fraction of inspired oxygen (FiO2) administered during general anaesthesia varies widely despite international recommendations to administer FiO2 0.8 to all anaesthetised patients to reduce surgical site infections (SSIs). Anaesthetists remain concerned that high FiO2 administration intraoperatively may increase harm, possibly through increased oxidative damage and inflammation, resulting in more complications and worse outcomes. In previous systematic reviews associations between FiO2 and SSIs have been inconsistent, but none have examined how FiO2 affects perioperative oxidative stress. We aimed to address this uncertainty by reviewing the available literature.

METHODS

EMBASE, MEDLINE, and Cochrane databases were searched from inception to March 9, 2020 for RCTs comparing higher with lower perioperative FiO2 and quantifying oxidative stress in adults undergoing noncardiac surgery. Candidate studies were independently screened by two reviewers and references hand-searched. Methodological quality was assessed using the Cochrane Collaboration Risk of Bias tool.

RESULTS

From 19 438 initial results, seven trials (n=422) were included. Four studies reported markers of oxidative stress during Caesarean section (n=328) and three reported oxidative stress during elective colon surgery (n=94). Risk of bias was low (four studies) to moderate (three studies). Pooled results suggested high FiO2 was associated with greater malondialdehyde, protein-carbonyl concentrations and reduced xanthine oxidase concentrations, together with reduced antioxidant markers such as superoxide dismutase and total sulfhydryl levels although total antioxidant status was unchanged.

CONCLUSIONS

Higher FiO2 may be associated with elevated oxidative stress during surgery. However, limited studies have specifically reported biomarkers of oxidation. Given the current clinical controversy concerning perioperative oxygen therapy, further research is urgently needed in this area.

The effect of intrapartum oxygen supplementation on category II fetal monitoring

BACKGROUND

Maternal oxygen administration is a widely used intrauterine resuscitation technique for fetuses with category II electronic fetal monitoring patterns, despite a paucity of evidence on its ability to improve electronic fetal monitoring patterns.

OBJECTIVE

This study investigated the effect of intrapartum oxygen administration on Category II electronic fetal monitoring patterns.

STUDY DESIGN

This is a secondary analysis of a randomized trial conducted in 2016-2017, in which patients with fetuses at ≥37 weeks' gestation in active labor with category II electronic fetal monitoring patterns were assigned to 10 L/min of oxygen by face mask or room air until delivery. Trained obstetrical research nurses blinded to allocation extracted electronic fetal monitoring data. The primary outcome was a composite of high-risk category II features including recurrent variable decelerations, recurrent late decelerations, prolonged decelerations, tachycardia, or minimal variability 60 minutes after randomization to room air or oxygen. Secondary outcomes included individual components of the composite high-risk category II features, resolution of recurrent decelerations within 60 minutes of randomization, and total deceleration area. The outcomes between the room air and oxygen groups were compared using univariable statistics. Time-to-event analysis was used to compare time to resolution of recurrent decelerations between the groups. Paired analysis was used to compare the pre- and postrandomization outcomes within each group.

RESULTS

All 114 randomized patients (57 room air and 57 oxygen) were included in this analysis. There was no difference in resolution of recurrent decelerations within 60 minutes between the oxygen and room air groups (75.4% vs 86.0%; P=.15). The room air and oxygen groups had similar rates of composite high-risk category II features including recurrent variable decelerations, recurrent late decelerations, prolonged decelerations, tachycardia, and minimal variability 60 minutes after randomization. Time to resolution of recurrent decelerations and total deceleration area were similar between the room air and oxygen groups. Among patients who received oxygen, there was no difference in the electronic fetal monitoring patterns pre- and postrandomization. Similar findings were observed in the electronic fetal monitoring patterns pre- and postrandomization in room air patients.

CONCLUSION

Intrapartum maternal oxygen administration for category II electronic fetal monitoring patterns did not resolve high-risk category II features or hasten the resolution of recurrent decelerations. These results suggest that oxygen administration has no impact on improving category II electronic fetal monitoring patterns.

Maternal oxygen exposure may not change umbilical cord venous partial pressure of oxygen: non-random, paired venous and arterial samples from a randomised controlled trial

Background

Despite the widespread use of oxygen (O₂) in intrauterine resuscitation, the obstetric scientists’ understanding of O₂ therapy is full of contradictions. We tested the hypothesis that higher maternal arterial partial pressure of oxygen (PO₂) is associated with higher umbilical cord venous PO₂ (UvPO₂).

Methods

This is a planned secondary analysis of a randomised controlled trial (RCT), 443 normal women were 1:1 randomly allocated to receive 2 L/min O₂ or room air from the onset of second stage to delivery. We reported that maternal 2 L/min O₂ exposure cannot affect the umbilical cord arterial pH or the fetal heart rate (FHR) pattern. In 217 non-random samples, we found 2 L/min O₂ exposure increased the maternal arterial PO₂ to the median 150 mmHg (hemoglobin would be saturated). The primary outcome for this analysis was UvPO₂ in these non-random samples.

Results

There were no significant differences between the O₂ group (N = 107) and the control group (N = 110) in the UvPO₂ (median 30.2, interquartile 25.4–35.2 versus median 28.3, interquartile 23.4–35.3, mmHg, P = 0.379). There were also no significant differences between room air and different percentiles of O₂ exposure duration (< 25th, ≧ 25th < 50th, ≧ 50th < 75th, ≧ 75th percentile) in the UvPO₂.

Conclusions

Maternal O₂ exposure at super-physiological levels (median arterial blood PO₂ 150 mmHg) in normal labor may not change the UvPO₂.

Clinical trial registration

ClinicalTrials.govNCT02221440, first posted in 20 August 2014.

The duration of intrapartum supplemental oxygen administration and umbilical cord oxygen content

BACKGROUND

Maternal oxygen (O₂) administration is a commonly performed intrauterine resuscitation technique though to improve fetal oxygenation. However, hyperoxygenation is known to be harmful in both neonates and adults. Currently, there are no formal recommendations on whether a certain dose or duration of O₂ may be most helpful in improving umbilical cord gases or neonatal outcomes.

OBJECTIVE

We tested the hypothesis that prolonged supplemental O₂ exposure during labor is associated with increased umbilical cord O₂ concentrations.

STUDY DESIGN

This was a planned secondary analysis of a randomized noninferiority trial comparing O₂ with room air in laboring patients. Patients were randomized to receive either 10 L/min O₂ or room air at any point during active labor when they developed a category II fetal heart tracing that would otherwise require resuscitation. The primary outcome variable for this analysis was partial pressure of O₂ in the umbilical vein. The secondary outcome variable was partial pressure of O₂ in the umbilical artery. These outcome variables were compared between patients with short durations of O₂ exposure and those with long durations of O₂ exposure, defined as <75th percentile and ≥75th percentile of duration, respectively. The outcomes were also compared among the groups that received room air, O₂ for short durations, and O₂ for long durations.

RESULTS

Among the 99 patients with paired and validated cord gases who were included in this analysis, the partial pressure of O₂ in the umbilical vein was significantly lower in patients who received O₂ supplementation for longer durations than in those who received O₂ for shorter durations (median interquartile range 25.5 [21.5-33] vs 32.5 [26.5-37.5] mm Hg; P<.03). There was no difference in the partial pressure of O₂ in the umbilical artery or other cord gases between the short and long duration O₂ supplementation groups. Other methods of intrauterine resuscitation were similar between the short and long duration O₂ supplementation groups. There was no difference in the partial pressure of O₂ in the umbilical artery or in the umbilical vein when the room air, short duration O₂ supplementation, and long duration O₂ supplementation groups were compared.

CONCLUSION

Longer durations of O₂ exposure are not associated with a higher partial pressure of O₂ in the umbilical cord. In fact, patients with longer durations of O₂ exposure had lower partial pressure of O₂ in the umbilical vein, suggesting impaired placental O₂ transfer with prolonged O₂ exposure.

Response to category II tracings: Does anything help?

Electronic fetal monitoring (EFM) is the most commonly used tool to screen for intrapartum fetal hypoxia. Category II EFM is present in over 80% of laboring patients and poses a unique challenge to management given the breadth of EFM features that fall within this category. Certain Category II patterns, such as recurrent late or recurrent variable decelerations, are more predictive of neonatal acidemia than others. A key feature among many published algorithms for Category II management is the use of intrauterine fetal resuscitation techniques including maternal oxygen administration, amnioinfusion, intravenous fluid bolus, discontinuation of oxytocin, and tocolytic administration. The goal of intrauterine resuscitation is to prevent or reverse fetal hypoxia. This is most likely to be successful if the etiology of the Category II EFM pattern is identified and targeted resuscitative measures are performed.

Effects of the anesthesia technique used during cesarean section on maternal-neonatal thiol disulfide homeostasis

BACKGROUND

Thiols are organic compounds consisting of a sulfhydryl group which exerts antioxidant effects via dynamic thiol-disulfide homeostasis (TDH). The shift towards the disulfide states signals an oxidative situation. Maternal-neonatal oxidative stress can be affected by the anesthetic technique used during cesarean section. This study aimed to evaluate the relationship between the type of anesthesia used and the maternal-neonatal TDH.

METHODS

ASA I-II, term parturients undergoing elective cesarean section either under general (Group G) or spinal (Group S) anesthesia were included. Blood specimens were collected preoperatively and postoperatively from the mothers and from the umbilical venous cords at delivery. TDH was studied by a new method developed by the authors (O.E. and S.N.).

RESULTS

Postoperative mother's native thiol, total thiol, disulfide/total thiol, native thiol/ disulfide and disulfide levels were higher in Group G than in Group S. There was no significant difference between the groups in umbilical venous cord albumin, native thiol/total thiol, disulfide, native thiol/ disulfide and total thiol/ disulfide. However, in Group G, umbilical venous cord native thiol and total thiol levels were statistically significantly lower than those in Group S.

CONCLUSIONS

Our results showed that general anesthesia in cesarean section leads to an impairment in TDH when compared with spinal anesthesia. Oxidative stress might be modified by the preferred anesthetic technique.

Hyperoxygenation in pregnancy exerts a more profound effect on cardiovascular hemodynamics than is observed in the nonpregnant state

BACKGROUND

Supplemental oxygen is administered to pregnant women in many different clinical scenarios in obstetric practice. Despite the accepted uses for maternal hyperoxygenation, the impact of hyperoxia on maternal hemodynamic indices has not been evaluated. As a result, there is a paucity of data in the literature in relation to the physiological changes to the maternal circulation in response to supplemental oxygen.

OBJECTIVE

The hemodynamic effects of oxygen therapy are under-recognized and the impact of hyperoxygenation on maternal hemodynamics is currently unknown. Using noninvasive cardiac output monitoring which employs transthoracic bioreactance, we examined the effect of brief hyperoxygenation on cardiac index, systemic vascular resistance, blood pressure, stroke volume, and heart rate in pregnant mothers during the third trimester, compared with those effects observed in a nonpregnant population subjected to the same period of hyperoxygenation.

STUDY DESIGN

Hemodynamic monitoring was performed in a continuous manner over a 30-minute period using noninvasive cardiac output monitoring. Hyperoxygenation (O₂ 100% v/v inhalational gas) was carried out at a rate of 12 L/min via a partial non-rebreather mask for 10-minutes. Cardiac index, systemic vascular resistance, stroke volume, heart rate, and blood pressure were recorded before hyperoxygenation, at completion of hyperoxygenation, and 10 minutes after the cessation of hyperoxygenation. Two-way analysis of variance with repeated measures was used to assess the change in hemodynamic indices over time and the differences between the 2 groups.

RESULTS

Forty-six pregnant and 20 nonpregnant women with a median age of 33 years (interquartile range, 26-38 years) and 32 years (interquartile range, 28-37 years) were recruited prospectively, respectively (P=.82). The median gestational age was 35 weeks (33-37 weeks). In the pregnant group, there was a fall in cardiac index during the hyperoxygenation exposure period (P=.009) coupled with a rise in systemic vascular resistance with no recovery at 10 minutes after cessation of hyperoxygenation (P=.02). Heart rate decreased after hyperoxygenation exposure and returned to baseline by 10 minutes after cessation of therapy. There was a decrease in stroke volume over the exposure period, with no change in systolic or diastolic blood pressure. In the nonpregnant group, there was no significant change in the cardiac index, systemic vascular resistance, stroke volume, heart rate, or systolic or diastolic blood pressure during the course of exposure to hyperoxygenation.

CONCLUSION

Hyperoxygenation during the third trimester is associated with a fall in maternal cardiac index and a rise in systemic vascular resistance without recovery to baseline levels at 10 minutes after cessation of hyperoxygenation. The hemodynamic changes that were observed in this study in response to hyperoxygenation therapy during pregnancy could counteract any intended increase in oxygen delivery. The observed maternal effects of hyperoxygenation call for a reevaluation of the role of hyperoxygenation treatment in the nonhypoxemic pregnant patient.

Premature Lambs Exhibit Normal Mitochondrial Respiration after Long-Term Extrauterine Support

BACKGROUND

In an effort to mitigate the major morbidities and mortality associated with extreme prematurity, we have developed an EXTrauterine Environment for Neonatal Development (EXTEND) designed to provide physiologic support of extremely premature infants.

OBJECTIVES

We have previously shown that long-term, physiologic support of premature fetal lambs is possible with EXTEND, but in this study, we sought to demonstrate bioenergetic equipoise at the tissue level.

METHODS

Four premature fetal lambs were delivered by hysterotomy at gestational ages (GA) of 105-107 days (term ∼145 days), cannulated via the umbilical vessels, and transitioned to support on EXTEND for 3-4 weeks. Five control fetuses were age-matched to the GA of experimental fetuses at the time of study end (128-134 days GA) and immediately sacrificed after hysterotomy. Mitochondria were isolated from the heart, liver, kidney, and skeletal muscle of fetuses at the time of sacrifice, and oxygen consumption rates (OCRs) were measured.

RESULTS

There were no differences in basal mitochondrial OCR between EXTEND and control fetuses for heart, kidney, or skeletal muscle. For liver, the basal OCR was higher in EXTEND fetuses compared to controls. There were no differences in physiologic maximal OCR or reserve capacity for any tissue analyzed.

CONCLUSIONS

Fetal lambs supported by EXTEND demonstrate physiologic mitochondrial function as evidenced by adequate basal and physiologic maximal cellular respiration as well as preserved reserve capacity.

Reference percentiles for paired arterial and venous umbilical cord blood gases: An indirect nonparametric approach

BACKGROUND

Reference intervals for arterial and venous umbilical cord blood gas (UCBG) parameters are scarce, are mainly focused on pH, pO2, pCO2 and base deficit, and are usually assessed using parametric tests, despite a generally skewed data distribution. Here, the purpose is to determine reference percentiles for nine parameters of concomitant arterial and venous UCBG (CAV-UCBG) from neonates at birth, using nonparametric tests.

METHODS

Results of CAV-UCBG, assayed over a 4.5-year period, were extracted from a hospital laboratory database for pH, pCO2, pO2, oxygen saturation, concentration of total oxygen, total carbon dioxide, hydrogen carbonate, total haemoglobin, and acid-base excess. Exclusion criteria were: a venous-arterial pH difference <0.02, an arterial-venous pCO2 <0.7 kPa, and a venous pCO2 <2.9 kPa. Nonparametric bivariate kernel density estimations were used for the selection of plots within the 95% percentile surface of the pCO2-to-pH relationship (NBKDE-95P). Outliers from skewed data were removed using an adjusted-Tukey method, and percentiles were calculated according to the CLSI EP28-A3 nonparametric method.

RESULTS

Overall, 31% (5033/16164) of CAV-UCBG were discarded using the three exclusion criteria. Then, 6% (670/11131) of CAV-UCBG were excluded from the NBKDE-95P, and 0.1 to 3.5% outliers were subsequently removed. Depending on the parameter, the 2.5th and 97.5th percentiles from the whole group were similar or slightly narrower compared to reference intervals from other studies, while those from female and male neonates did not differ substantially.

CONCLUSIONS

Using an indirect nonparametric approach, this study proposes new percentiles for parameters from concomitant arterial and venous umbilical cord blood gases.

Defining Physiological Normoxia for Improved Translation of Cell Physiology to Animal Models and Humans

The extensive oxygen gradient between the air we breathe (Po₂ ~21 kPa) and its ultimate distribution within mitochondria (as low as ~0.5-1 kPa) is testament to the efforts expended in limiting its inherent toxicity. It has long been recognized that cell culture undertaken under room air conditions falls short of replicating this protection in vitro. Despite this, difficulty in accurately determining the appropriate O₂ levels in which to culture cells, coupled with a lack of the technology to replicate and maintain a physiological O₂ environment in vitro, has hindered addressing this issue thus far. In this review, we aim to address the current understanding of tissue Po₂ distribution in vivo and summarize the attempts made to replicate these conditions in vitro. The state-of-the-art techniques employed to accurately determine O₂ levels, as well as the issues associated with reproducing physiological O₂ levels in vitro, are also critically reviewed. We aim to provide the framework for researchers to undertake cell culture under O₂ levels relevant to specific tissues and organs. We envisage that this review will facilitate a paradigm shift, enabling translation of findings under physiological conditions in vitro to disease pathology and the design of novel therapeutics.

A Review of the Impact of Obstetric Anesthesia on Maternal and Neonatal Outcomes

Obstetric anesthesia has evolved over the course of its history to encompass comprehensive aspects of maternal care, ranging from cesarean delivery anesthesia and labor analgesia to maternal resuscitation and patient safety. Anesthesiologists are concerned with maternal and neonatal outcomes, and with preventing and managing complications that may present during childbirth. The current review will focus on recent advances in obstetric anesthesia, including labor anesthesia and analgesia, cesarean delivery anesthesia and analgesia, the effects of maternal anesthesia on breastfeeding and fever, and maternal safety. The impact of these advances on maternal and neonatal outcomes is discussed. Past and future progress in this field will continue to have significant implications on the health of women and children.

Analysis of Neonatal Outcome with Supplemental Oxygen to Mother during Elective Cesarean Section under Spinal Anesthesia: A Prospective Randomized Controlled Trial

Background:

Many questions have arisen on benefits of routine use of supplemental oxygen during elective cesarean section (CS) under spinal anesthesia.

Aims:

The aim of this randomized controlled study was to evaluate neonatal outcome in immediate postpartum period with or without supplemental oxygen to mother, undergoing elective CS under spinal anesthesia.

Materials and Methods:

One hundred and thirty-four nonlaboring term pregnant women were allocated randomly into two groups to breathe room air (air group) or oxygen (oxygen group). Times from starting oxygen supplementation to delivery interval, skin incision to delivery (I-D) interval, and uterine incision to delivery (U-D) interval were recorded. APGAR scores were assessed at 1 min and 5 min after delivery. Umbilical cord blood gas analysis was done immediately to measure pH, oxygen partial pressure, carbon dioxide partial pressure (PCO₂), and bicarbonate.

Statistical Analysis:

Statistical comparisons were performed using either Student's t-test or Mann–Whitney U-test.

Results:

For oxygen group versus air group, In Oxygen group, proportion of fetal acidosis was significantly less; umbilical arterial (UA) blood pH (7.22 ± 0.05 vs. 7.19 ± 0.05, P = 0.001) as well as umbilical venous (UV) blood pH (7.26 ± 0.05 vs. 7.22 ± 0.06, P < 0.001) were significantly higher and UA PCO2 (55.4 ± 9.9 vs. 62.9 ± 6.9, P = 0.001) and UV PCO2 (51.4 ± 8.2 vs. 54.3 ± 7.2, P = 0.036) were significantly lower compared to air group. APGAR scores were similar between the groups.

Conclusions:

Supplemental oxygen has potential benefits as demonstrated by less proportion of FA in mothers receiving supplemental oxygen.

Update on Fetal Monitoring: Overview of Approaches and Management of Category II Tracings

Electronic fetal monitoring (EFM) is widely used to assess fetal status in labor. Use of intrapartum continuous EFM is associated with a lower risk of neonatal seizures but a higher risk of cesarean or operative delivery. Category II fetal heart tracings (FHTs) are indeterminate in their ability to predict fetal acidemia. Certain patterns of decelerations and variability within this category may be predictive of neonatal morbidity. Adjunct tests of fetal well-being can be used during labor to further triage patients. Intrauterine resuscitation techniques should target the suspected etiology of intrapartum fetal hypoxia. Clinical factors play a role in the interpretation of EFM.

The effect of the modes of delivery on the maternal and neonatal dynamic thiol-disulfide homeostasis

Background: Thiols are organic compounds containing sulfhydryl groups which exert antioxidant effects via dynamic thiol-disulfide homeostasis. The shift towards disulfide indicates the presence of oxidative environment. The thiol-disulfide homeostasis has not been studied in different mode of delivery before. Aims: To investigate the effects of mode of parturition on the thiol-disulfide homeostasis in mothers and term infants. Study design: The participants were grouped according to the mode of their delivery: group vaginal delivery (VD, n = 40) and group cesarean section (C/S, n = 40). Three serum samples were collected: from mothers at the beginning of labor, from the cord blood (CB), and from the infants at the 24th hour after birth. The dynamic thiol-disulfide homeostasis in both groups were compared. Results: The levels of native-thiol and total-thiol in CB were significantly higher in VD group than those with C/S group. The levels of disulfide were higher in infants born by C/S compared with those born by VD. The disulfide-to-native thiol ratio, disulfide-to-total thiol ratio, and native thiol-to-total thiol ratio were similar between two groups. Conclusion: Our results showed that the dynamic thiol-disulfide homeostasis of the neonate was greatly influenced by the way of delivery and supported that vaginally delivered infants have less oxidative stress.

Intrauterine resuscitation during the second stage of term labour by maternal hyperoxygenation versus conventional care: study protocol for a randomised controlled trial (INTEREST O2)

BACKGROUND

Perinatal asphyxia is, even in developed countries, one the major causes of neonatal morbidity and mortality. Therefore, if foetal distress during labour is suspected, one should try to restore foetal oxygen levels or aim for immediate delivery. However, studies on the effect of intrauterine resuscitation during labour are scarce. We designed a randomised controlled trial to investigate the effect of maternal hyperoxygenation on the foetal condition. In this study, maternal hyperoxygenation is induced for the treatment of foetal distress during the second stage of term labour.

METHODS/DESIGN

This study is a single-centre randomised controlled trial being performed in a tertiary hospital in The Netherlands. From among cases of a suboptimal or abnormal foetal heart rate pattern during the second stage of term labour, a total of 116 patients will be randomised to the control group, where normal care is provided, or to the intervention group, where before normal care 100% oxygen is supplied to the mother by a non-rebreathing mask until delivery. The primary outcome is change in foetal heart rate pattern. Secondary outcomes are Apgar score, mode of delivery, admission to the neonatal intensive care unit and maternal side effects. In addition, blood gas values and malondialdehyde are determined in umbilical cord blood.

DISCUSSION

This study will be the first randomised controlled trial to investigate the effect of maternal hyperoxygenation for foetal distress during labour. This intervention should be recommended only as a treatment for intrapartum foetal distress, when improvement of the foetal condition is likely and outweighs maternal and neonatal side effects.

TRIAL REGISTRATION

EudraCT, 2015-001654-15; registered on 3 April 2015. Dutch Trial Register, NTR5461; registered on 20 October 2015.

Effect of maternal oxygen inhalation on foetal free radical activity: a prospective, randomized trial

BACKGROUND

Maternal inhalation of 35-40% oxygen concentration has no significant effect on foetal partial pressure of oxygen, and 60-100% produced maternal and foetal hyperoxia with increased free radical activity. The benefit of 50% maternal oxygen inhalation on foetal oxygenation, oxidant stress and total antioxidant status (TAS) during Caesarean section (CS) has not been simultaneously evaluated.

METHODS

In this prospective, randomized, controlled trial 120 ASA physical status I-II, term pregnant women were recruited to elective CS (n = 60) and emergency CS (n = 60) and received either 50% oxygen or air inhalation following subarachnoid block (SAB). Patients and investigators were blinded to the inhaled oxygen concentration. The primary outcome of the study was foetal umbilical artery (UA) malondialdehyde (MDA) at birth.

RESULTS

In both elective and emergency CS, there was no difference in foetal oxidative stress and TAS in spite of increase in maternal PaO2. In elective CS, maternal MDA was higher at delivery in mothers breathing 50% oxygen as compared to their own baseline values (P = 0.04). In emergency CS, maternal TAS at 10 min was lower in mothers inhaling 50% oxygen as compared to air (P = 0.01). The average duration of maternal oxygen supplementation was ~10.3 min in elective and ~7.4 min in emergency CS. Neonatal outcome, episodes of maternal hypotension and oxygen desaturation were similar in both the groups.

CONCLUSION

Brief duration of 50% oxygen maternal inhalation during elective or emergency CS did not significantly affect foetal MDA and TAS under SAB.

Intrauterine Hyperoxemia and Risk of Neonatal Morbidity

OBJECTIVE

To test the hypothesis that intrauterine hyperoxemia is associated with an increased risk of neonatal morbidity.

METHODS

This was a secondary analysis of a prospective study of singleton, nonanomalous deliveries at or beyond 37 weeks of gestation at an institution with a universal umbilical cord gas policy from 2010 to 2014. The primary outcome was a composite of neonatal morbidity including neonatal death, meconium aspiration syndrome, intubation, mechanical ventilation, hypoxic-ischemic encephalopathy, and hypothermic therapy. Intrauterine hyperoxemia was defined as umbilical vein partial pressure of oxygen 90th percentile or greater of the cohort. Adjusted relative risks (RRs) were estimated for neonatal morbidity controlling for confounders. Analysis was performed for the entire cohort and stratified by the presence of acidemia defined as umbilical artery pH less than 7.1.

RESULTS

Of 7,789 patients with validated paired cord gases, 106 (1.4%) had the composite neonatal morbidity. There was no difference in composite neonatal morbidity in patients with and without intrauterine hyperoxemia in the entire cohort (1.5% compared with 1.3%, adjusted RR 1.5, 95% confidence interval [CI] 0.9-2.7). The rate of acidemia was not significantly different in the two groups (1.9% compared with 1.8%, adjusted RR 1.5, 95% CI 0.9-2.5). In stratified analysis, there was evidence of effect modification (P for interaction <.001) with a significant association between intrauterine hyperoxemia and neonatal morbidity in the presence of acidemia (41.2% compared with 21.4%, adjusted RR 2.3, 95% CI 1.1-3.5), but not in its absence (0.8% compared with 1.0%, adjusted RR 1.0, 95% CI 0.5-2.2).

CONCLUSION

Intrauterine hyperoxemia, compared with normoxemia, is associated with a small but significantly increased risk of neonatal morbidity in acidemic neonates.

Oxygen and oxidative stress in the perinatal period

Fetal life evolves in a hypoxic environment. Changes in the oxygen content in utero caused by conditions such as pre-eclampsia or type I diabetes or by oxygen supplementation to the mother lead to increased free radical production and correlate with perinatal outcomes. In the fetal-to-neonatal transition asphyxia is characterized by intermittent periods of hypoxia ischemia that may evolve to hypoxic ischemic encephalopathy associated with neurocognitive, motor, and neurosensorial impairment. Free radicals generated upon reoxygenation may notably increase brain damage. Hence, clinical trials have shown that the use of 100% oxygen given with positive pressure in the airways of the newborn infant during resuscitation causes more oxidative stress than using air, and increases mortality. Preterm infants are endowed with an immature lung and antioxidant system. Clinical stabilization of preterm infants after birth frequently requires positive pressure ventilation with a gas admixture that contains oxygen to achieve a normal heart rate and arterial oxygen saturation. In randomized controlled trials the use high oxygen concentrations (90% to 100%) has caused more oxidative stress and clinical complications that the use of lower oxygen concentrations (30-60%). A correlation between the amount of oxygen received during resuscitation and the level of biomarkers of oxidative stress and clinical outcomes was established. Thus, based on clinical outcomes and analytical results of oxidative stress biomarkers relevant changes were introduced in the resuscitation policies. However, it should be underscored that analysis of oxidative stress biomarkers in biofluids has only been used in experimental and clinical research but not in clinical routine. The complexity of the technical procedures, lack of automation, and cost of these determinations have hindered the routine use of biomarkers in the clinical setting. Overcoming these technical and economical difficulties constitutes a challenge for the immediate future since accurate evaluation of oxidative stress would contribute to improve the quality of care of our neonatal patients.

The 2015 Gerard W. Ostheimer Lecture: What's New in Labor Analgesia and Cesarean Delivery

Every year the Board of Directors of the Society for Obstetric Anesthesia and Perinatology selects an individual to review the literature pertinent to obstetric anesthesiology published the previous calendar year. This individual selects the most notable contributions, creates a syllabus of the articles, and then presents his/her overview in an annual lecture named in honor of the late Gerard W. Ostheimer, a pioneering obstetric anesthesiologist from the Brigham and Women's Hospital. This article reviews the literature published in 2014 focusing on the themes of labor analgesia and cesarean delivery. Its contents were presented as the Gerard W. Ostheimer Lecture at the 47th Annual Meeting of the Society for Obstetric Anesthesia and Perinatology, May 16, 2015, in Colorado Springs, Colorado. The syllabus is available as Supplemental Digital Content (http://links.lww.com/AA/B397).

Supplemental oxygen for caesarean section during regional anaesthesia

BACKGROUND

Supplementary oxygen is routinely administered to low-risk pregnant women during an elective caesarean section under regional anaesthesia; however, maternal and foetal outcomes have not been well established. This is an update of a review first published in 2013.

OBJECTIVES

The primary objective was to determine whether supplementary oxygen given to low-risk term pregnant women undergoing elective caesarean section under regional anaesthesia can prevent maternal and neonatal desaturation. The secondary objective was to compare the mean values of maternal and neonatal blood gas levels between mothers who received supplementary oxygen and those who did not (control group).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; 2014, issue 11), MEDLINE (1948 to November 2014) and EMBASE (1980 to November 2014). The original search was first performed in February 2012. We reran the search in CENTRAL, MEDLINE, EMBASE in February 2016. One potential new study of interest was added to the list of 'Studies awaiting Classification' and will be incorporated into the formal review findings during the next review update.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) of low-risk pregnant women undergoing an elective caesarean section under regional anaesthesia and compared outcomes with, and without, oxygen supplementation.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data, assessed methodological quality and performed subgroup and sensitivity analyses.

MAIN RESULTS

We found one new included study in this updated version. In total, our updated review includes 11 trials (with 753 participants). The low quality of evidence showed no significant differences in average Apgar scores at one minute (N = six trials, 519 participants; 95% confidence (CI) -0.16 to 0.31, P = 0.53) and at five minutes (N = six trials, 519 participants; 95% CI -0.06 to 0.06, P = 0.98). None of the 11 trials reported maternal desaturation. The very low quality of evidence showed that in comparison to room air, women in labour receiving supplementary oxygen had higher maternal oxygen saturation (N = three trials, 209 participants), maternal PaO2 (oxygen pressure in the blood; N = six trials, 241 participants), UaPO2 (foetal umbilical arterial blood; N = eight trials, 504 participants; 95% CI 1.8 to 4.9, P < 0.0001) and UvPO2 (foetal umbilical venous blood; N = 10 trials, 683 participants). There was high heterogeneity among these outcomes. A subgroup analysis showed no significant difference in UaPO2 between the two intervention groups in low-risk studies, whereas the high-risk studies showed a benefit for the neonatal oxygen group.

AUTHORS' CONCLUSIONS

Overall, we found no convincing evidence that giving supplementary oxygen to healthy term pregnant women during elective caesarean section under regional anaesthesia is either beneficial or harmful for either the mother or the foetus' short-term clinical outcome as assessed by Apgar scores. Although, there were significant higher maternal and neonatal blood gas values and markers of free radicals when extra oxygen was given, the results should be interpreted with caution due to the low grade quality of the evidence.

Interventions for Intrauterine Resuscitation in Suspected Fetal Distress During Term Labor: A Systematic Review

IMPORTANCE

Intrauterine resuscitation techniques during term labor are commonly used in daily clinical practice. Evidence, however, to support the beneficial effect of intrauterine resuscitation techniques on fetal distress during labor is limited and sometimes contradictory. In contrast, some of these interventions may even be harmful.

OBJECTIVE

To give insight into the current evidence on intrauterine resuscitation techniques. In addition, we formulate recommendations for current clinical practice and propose directions for further research.

EVIDENCE ACQUISITION

We systematically searched the electronic PubMed, EMBASE, and CENTRAL databases for studies on intrauterine resuscitation for suspected fetal distress during term labor until February 2015. Eligible articles and their references were independently assessed by 2 authors. Judgment was based on methodological quality and study results.

RESULTS

Our literature search identified 15 studies: 4 studies on amnioinfusion, 1 study on maternal hyperoxygenation, 1 study on maternal repositioning, 1 study on intravenous fluid administration, and 8 studies on tocolysis. Of these 15 research papers, 3 described a randomized controlled trial; all other studies were observational reports or case reports.

CONCLUSIONS AND RELEVANCE

Little robust evidence to promote a specific intrauterine resuscitation technique is available. Based on our literature search, we support the use of tocolysis and maternal repositioning for fetal distress. We believe the effect of amnioinfusion and maternal hyperoxygenation should be further investigated in properly designed randomized controlled trials to make up the balance between beneficial and potential hazardous effects.

Whither oxygen for intrauterine resuscitation?

Oxygen is frequently administered to women in labor in the hope of improving fetal status. However, there is a paucity of outcome data to support this practice. Although maternal oxygen administration may make physiological sense, unwarranted faith in maternal oxygen therapy may delay the indicated intervention or result in continued labor stimulation when neither is in the best interests of the fetus. A properly designed clinical trial would help answer whether maternal oxygen supplementation in labor should be considered an indicated intervention for nonreassuring fetal status.

Effects of elevated oxygen and carbon dioxide partial pressures on respiratory function and cognitive performance

Hyperoxia during diving has been suggested to exacerbate hypercapnic narcosis and promote unconsciousness. We tested this hypothesis in male volunteers (12 at rest, 10 at 75 W cycle ergometer exercise) breathing each of four gases in a hyperbaric chamber. Inspired Po2 (PiO2) was 0.21 and 1.3 atmospheres (atm) without or with an individual subject's maximum tolerable inspired CO2 (PiO2 = 0.055–0.085 atm). Measurements included end-tidal CO2 partial pressure (PetCO2), rating of perceived discomfort (RPD), expired minute ventilation (V̇e), and cognitive function assessed by auditory n-back test. The most prominent finding was, irrespective of PetCO2, that minute ventilation was 8–9 l/min greater for rest or exercise with a PiO2 of 1.3 atm compared with 0.21 atm ( P < 0.0001). For hyperoxic gases, PetCO2 was consistently less than for normoxic gases ( P < 0.01). For hyperoxic hypercapnic gases, n-back scores were higher than for normoxic gases ( P < 0.01), and RPD was lower for exercise but not rest ( P < 0.02). Subjects completed 66 hyperoxic hypercapnic trials without incident, but five stopped prematurely because of serious symptoms (tunnel vision, vision loss, dizziness, panic, exhaustion, or near syncope) during 69 normoxic hypercapnic trials ( P = 0.0582). Serious symptoms during hypercapnic trials occurred only during normoxia. We conclude serious symptoms with hyperoxic hypercapnia were absent because of decreased PetCO2 consequent to increased ventilation.

Oxygen for intrauterine resuscitation: of unproved benefit and potentially harmful

Maternal oxygen is often given to laboring women to improve fetal metabolic status or in an attempt to alleviate nonreassuring fetal heart rate patterns. However, the only 2 randomized trials investigating the use of maternal oxygen supplementation in laboring women do not support that such supplementation is likely to be of benefit to the fetus. And by increasing free radical activity, maternal oxygen supplementation may even be harmful. Based on a review of the available literature, we conclude that until it is studied properly in a randomized clinical trial, maternal oxygen supplementation in labor should be reserved for maternal hypoxia, and should not be considered an indicated intervention for nonreassuring fetal status.

Comparison of oxidative stress markers in umbilical cord blood after vaginal and cesarean delivery

Objective

The purpose of our study was to investigate the effect of the mode of delivery on the oxidant and antioxidant system in umbilical cord blood.

Methods

We performed gas analysis of umbilical venous blood and umbilical arterial blood immediately after delivery in 38 women; eighteen women had a vaginal delivery while 20 women delivered via cesarean section at over 37 weeks gestation. We examined lipid peroxide concentration by thiobarbituric acid reaction, protein carbonyl content by 2,4-dinitrophenylhydrazine reaction, and total antioxidant capacity by oxygen radical absorbance capacity assay.

Results

Lipid peroxide levels in umbilical venous blood were significantly higher in patients delivering by planned cesarean section (1.81 ± 0.06 nmol/mg protein) than those with vaginal delivery (1.24 ± 0.05 nmol/mg protein) (P < 0.05). Antioxidant capacity in umbilical venous blood was significantly higher in patients delivering by planned cesarean section (119.70 ± 0.13 µM/µL) than those with a vaginal delivery (118.70 ± 0.29 µM/µL) (P < 0.05). There was no significant difference in the carbonyl content of umbilical venous blood or in the lipid peroxide, carbonyl content, and total antioxidant capacity of umbilical arterial blood.

Conclusion

Lipid peroxidation levels and antioxidant capacity in umbilical venous blood were higher in patients delivering by planned cesarean section than those with a vaginal delivery. Therefore, we propose that both the mother and neonate are exposed to higher oxidative stress during cesarean section delivery.

Cesarean delivery under spinal anesthesia is associated with decreases in cerebral oxygen saturation as assessed by NIRS: an observational study

OBJECTIVES

To investigate the effect of spinal anesthesia on cerebral rSO2 during elective cesarean delivery (CD).

METHODS

Thirty-four women scheduled for elective CD under spinal anesthesia were recruited. In the operating room rSO2 of the left and right frontal area and right thigh was recorded using three disposable sensors. A combination of 1.8-2.0 ml of 0.75% ropivacaine plus 10 μg of fentanyl were injected intrathecally. Systolic and diastolic blood pressure, heart rate, SpO2 as well as rSO2 of the left and right forehead areas and right thigh were recorded before, 5, 10, and 25 to 50 minutes after spinal injection, after uterine incision and placenta delivery, and analyzed with ANOVA repeated measures. The study was approved by the Aretaieio Hospital Institutional Review Board and registered with ClinicalTrials.gov (ID: NCT01669135).

RESULTS

The rSO2 left and right frontal area values decreased significantly from baseline (p=0.0001 and p=0.0001 respectively), with most remarkable decreases 5 and 10 minutes after spinal injection, from 65 (SD 8.7)% to 56 (SD 9.3)% and 56 (SD 9.5)% (p=0.0001 and p=0.0001) for the left and from 63 (SD 7.7)% to 55 (SD 9.3)% and 56 (SD 8.9)% (p=0,0001 and p=0.0001) for the right frontal area respectively. The rSO2 right thigh values increased significantly during the study period (p=0.0001).

KEY LIMITATIONS

Contribution of extracranial circulation to the rSO2, lack of PaCO2 and cardiac output measurements.

CONCLUSIONS

Women undergoing CD under spinal anesthesia may present decreases in cerebral rSO2. The clinical impact of these results remains to be determined.

Effects of supplemental oxygen on maternal and neonatal oxygenation in elective cesarean section under spinal anesthesia: a randomized controlled trial

The use of supplemental oxygen in uncomplicated cesarean deliveries under spinal anesthesia has been thoroughly investigated during recent decades. The aim of this study was to determine the benefits for both mother and infant of administering supplemental, low-dose oxygen via a nasal cannula versus having no supplement (i.e., room air only). Healthy parturients at term undergoing elective cesarean section under spinal anesthesia were randomly allocated into two groups: an oxygen group (n = 170), who received 3 LPM oxygen via a nasal cannula; and a room-air group (n = 170), who were assigned to breathe room air. Maternal oxygen saturation was measured continuously by using pulse oximeter. The desaturation was determined by oxygen saturation <94% over 30 seconds. Umbilical cord gases and Apgar scores were collected followed delivery of the infant. All maternal desaturation events occurred in 12 parturients assigned to the room-air group. Most events were concurrent with hypotension. The umbilical venous partial pressure of oxygen was significantly higher in the oxygen group. The other blood gas measurements and Apgar scores were not significantly different between the two groups. Based on our findings, the use of supplemental oxygen could prevent maternal desaturation resulting from receiving sedation and intraoperative hypotension.