[Is oxygen therapy truly useful and necessary during elective cesarean section under spinal anesthesia?]

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.

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.

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.

Supplemental Perioperative Oxygen (80% FIO2) for the Prevention of Surgical Site Infection after Emergency Cesarean Section

Objective. Cesarean section can be a lifesaving procedure. However, as with many surgeries, it is not exempt of complications. Surgical site infections generate higher costs, serious morbidity, and mortality. This study evaluates the benefits of perioperative oxygen to prevent surgical site infections. Methods. We conducted a randomized controlled trial to assess the effects of perioperative oxygen to prevent surgical site infection after emergency cesarean section. Patients were randomized to receive either oxygen (80% FIO2) during cesarean section plus two hours postsurgery or no supplemental oxygen. A sample of 326 patients was calculated for the primary outcome (163 in each group) and they were evaluated daily before leaving the hospital, at days 15 and 30. Results. Initially, 360 patients were enrolled, from which 17 were excluded (sample size: 343 (179 patients in the air group and 164 in the oxygen group)). We found no significant difference in the incidence of surgical site infection between these two groups at any of the evaluation times. Conclusion. In this study of patients with emergency cesarean section, we showed that the use of supplemental oxygen does not reduce the incidence of surgical site infection. This trial is registeres with ClinicalTrials.gov NCT01340534.

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.

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) (The Cochrane Library, Issue 2, 2012), MEDLINE (1948 to February 2012) and EMBASE (1980 to February 2012). We did not apply language restrictions.

SELECTION CRITERIA

We included randomized controlled trials 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 included 10 trials with a total of 683 participants. Supplementary oxygen administration varied widely in dose and duration between trials. No cases of maternal desaturation were reported, although none of the 10 trials focused on maternal desaturation. Significant differences were noted in maternal oxygen saturation (higher with oxygen, N = three trials; mean difference (MD) 1.6%, 95% confidence interval (CI) 0.8 to 2.3, P < 0.0001), maternal PaO2 (oxygen pressure in the blood; higher with oxygen, N = six trials; MD 141.8 mm Hg, 95% CI 109.3 to 174.3, P < 0.00001), neonatal UaPO2 (foetal umbilical arterial blood; higher with oxygen, N = eight trials; MD 3.3 mm Hg, 95% CI 1.8 to 4.9, P < 0.0001) and UvPO2 (foetal umbilical venous blood; higher with oxygen, N = 10 trials; MD 5.9 mm Hg, 95% CI 3.2 to 8.5, P < 0.0001). No significant differences were reported in neonatal UapH (N = eight trials; MD 0.00, 95% CI -0.01 to 0.00, P = 0.26) and in average Apgar scores at one minute (N = five trials; MD 0.07, 95% CI -0.20 to 0.34, P = 0.6) and at five minutes (N = five trials; MD 0.00, 95% CI -0.06 to 0.05, P = 0.91).Only two out of 10 trials had a low risk of bias in all categories. When we separated the studies into low risk and high risk for bias, we found substantial statistical heterogeneity. None of the low-risk studies showed a significant difference in neonatal UaPO2 between the two intervention groups, whereas the high-risk studies showed a benefit for the neonatal oxygen group.The level of oxygen free radicals (malondialdehyde (MDA) and 8-isoprostane) was higher in participants who received supplementary oxygen (N = two trials; MD 0.2 µmol/L, 95% CI 0.1 to 0.4, P = 0.0002; MD 64.3 pg/mL, 95% CI 51.7 to 76.8, P < 0.00001, respectively).

AUTHORS' CONCLUSIONS

Current evidence suggests that supplementary oxygen given to healthy term pregnant women during elective caesarean section under regional anaesthesia is associated with higher maternal and neonatal oxygen levels (maternal SpO2, PaO2, UaPO2 and UvPO2) and higher levels of oxygen free radicals. However, the intervention was neither beneficial nor harmful to the neonate's short-term clinical outcome as assessed by Apgar scores.

[Caesarean sections under regional anesthesia: pros and cons of supplementary oxygen]

The routine administration of supplemental oxygen to women undergoing elective caesarean section under regional anesthesia in order to optimize oxygen supply to the fetus is common anesthetic practice in many German hospitals. However, this practice has been controversially discussed in the non-German literature for many years. This review presents and discusses the pros and cons of routinely providing supplemental oxygen to a parturient during caesarean section on the basis of the literature published over the last 30 years. Proponents of routine oxygen administration point to potential and unforeseeable risks of caesarean sections and consider the prophylactic administration of oxygen based on physiological considerations to be advantageous in terms of patient safety. Interestingly, data regarding the effects of an increased maternal FIO2 on improvement of fetal oxygenation are inconsistent, therefore, no unambiguous recommendation concerning which FIO2 to choose can be given. Opponents of routine oxygen supplementation allude above all to an increase in free radical activity in both mother and fetus; however, data in this respect are not consistent either. As supplemental oxygen to patients undergoing elective caesarean section without any risk factors under regional anesthesia is associated with potential risks while no advantage has so far been demonstrated, routine administration of oxygen has to be challenged and is no longer considered to be indicated by many. On the contrary, in cases of emergency with a concomitant risk of hypoxia for mother and fetus, administration of oxygen is indispensable in the light of present data.