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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.