Effect of Oxygen vs Room Air on Intrauterine Fetal Resuscitation

Abstract

IMPORTANCE Two-thirds of women in labor receive supplemental oxygen to reverse perceived fetal hypoxemia and prevent acidemia. Oxygen is routinely administered for category II fetal heart tracings, a class of fetal tracing used to designate intermediate risk for acidemia. This liberal use of oxygen may not be beneficial, particularly because neonatal hyperoxygenation is harmful. OBJECTIVE To test the hypothesis that room air is noninferior to oxygen in improving fetal metabolic status among patients with category II fetal heart tracings. DESIGN, SETTING, AND PARTICIPANTS This was a randomized, unblinded noninferiority clinical trial conducted between June 2016 and July 2017 in the labor and delivery ward of a single tertiary care center. Women with singleton pregnancies at 37 weeks' gestational age or more who were admitted for delivery were eligible. Of those who met inclusion criteria, the patients who developed category II tracings in labor that necessitated intrauterine resuscitation were randomized in a 1:1 ratio to room air or oxygen. Analyses were intention-to-treat. INTERVENTIONS The oxygen group received 10 L of oxygen per minute by nonrebreather facemask until delivery. The room air group was exposed to room air only without a facemask. MAIN OUTCOMES AND MEASURES The primary outcome was umbilical artery lactate, a marker of metabolic acidosis and neonatal morbidity. Noninferiority was defined as a mean difference between groups of less than 9.0 mg/dL (1.0 mmol/L). Secondary outcomes were other umbilical artery gases, cesarean delivery for nonreassuring fetal status, and operative vaginal delivery. RESULTS Of the 705 patients who met inclusion criteria, 277 (39.3%) were enrolled on admission. During labor, 114 patients (41.2% of the enrolled patients) developed category II tracings and were randomized to room air (57 patients; 50.0% of the randomized patients) or oxygen (57 patients; 50.0% of the randomized patients). A total of 99 patients (86.8% of the randomized patients) with paired cord gases were included in the modified intention-to-treat analysis. The 99 patients included 76 African American women (77%); mean (SD) age was 27.3 (6.3) years in the oxygen group and 27.8 (5.3) years in the room air group. There was no difference in umbilical artery lactate between the group on oxygen and the group on room air (mean, 30.6 mg/dL [95% CI, 27.0 to 34.2 mg/dL] vs 31.5 mg/dL [95% CI, 27.9 to 36.0 mg/dL]); P = .69). The mean difference in lactate was 0.9 mg/dL (95% CI, −4.5 to 6.3 mg/dL), which was within the noninferiority margin. There was no difference in other umbilical artery gas components or mode of delivery between groups. CONCLUSIONS AND RELEVANCE Among patients with category II fetal heart tracings, intrauterine resuscitation with room air is noninferior to oxygen in improving umbilical artery lactate. The results of this trial challenge the efficacy of a ubiquitous obstetric practice and suggest that room air may be an acceptable alternative.

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

“…Our trial randomized 443 normal women and found there were no significant differences between 2 L/min O 2 group and room air group in the abnormal umbilical cord arterial pH values, and found in 217 non-random samples maternal O 2 exposure at super-physiological levels (median arterial blood PO 2 150 mmHg) cannot increase the umbilical cord venous PO 2 (30.2 versus 28.3 mmHg) [ 11 ]. Raghuraman et al [ 24 ] randomized 114 women with nonreassuring FHR tracings and found there were no significant differences between 10 L/min O 2 group and room air group in the abnormal umbilical cord arterial pH and lactate values, and they even found long durations of O 2 exposure were associated with lower in the UvPO 2 (32.5 versus 25.5 mmHg). Thorp et al [ 25 ] randomized 86 normal women and found maternal 10 L/min O 2 exposure were associated with more umbilical cord arterial pH < 7.2 events (9/41 versus 2/44), and found this O 2 exposure cannot increase the in the UvPO 2 (31.2 versus 29.7 mmHg).…”

“…Our results did not conflict with previous studies. In Raghuraman et al [ 24 ] and Thorp et al [ 25 ] trials, the O 2 flow rate was 10 L/min and the fraction of inspired O 2 (FIO 2 ) was about 60–80%, Thorp et al [ 25 ] showed high level O 2 exposure had no effect on UvPO 2, and Raghuraman et al [ 24 ] even showed longer high level O 2 exposure was associated with lower UvPO 2 . The effects of super-physiological O 2 induced vasoconstriction would reduce blood perfusion of tissue to a greater extent than the little maternal arterial O 2 content rise [ 11 ].…”

Effect of intrapartum oxygen on the rate of cesarean delivery: a meta-analysis

“…Five total articles were included in the systematic review and meta-analysis. [15][16][17][18][19] The search process according to the PRISMA statement is shown in Figure 1.…”

“…Characteristics of the five included studies in the meta-analysis are included in Table 1. [15][16][17][18][19] Two studies administered oxygen for NRFHM, 17,18 two administered oxygen prophylactically during the 2 nd stage, 15,19 and one administered oxygen prophylactically for at least 30 minutes before delivery. 16 Two studies administered oxygen at 2L/min 15,16 while three administered oxygen at10L/min.…”

“…16 Two studies administered oxygen at 2L/min 15,16 while three administered oxygen at10L/min. [17][18][19] Risk of bias is outlined in Figure 2. In general, bias was considered low in most areas.…”