Resuscitation of Asphyxiated Newborn Infants With Room Air or Oxygen: An International Controlled Trial: The Resair 2 Study

Abstract

Objective. Birth asphyxia represents a serious problem worldwide, resulting in ∼1 million deaths and an equal number of serious sequelae annually. It is therefore important to develop new and better ways to treat asphyxia. Resuscitation after birth asphyxia traditionally has been carried out with 100% oxygen, and most guidelines and textbooks recommend this; however, the scientific background for this has never been established. On the contrary, theoretic considerations indicate that resuscitation with high oxygen concentrations could have detrimental effects. We have performed a series of animal studies as well as one pilot study indicating that resuscitation can be performed with room air just as efficiently as with 100% oxygen. To test this more thoroughly, we organized a multicenter study and hypothesized that room air is superior to 100% oxygen when asphyxiated newborn infants are resuscitated. Methodology. In a prospective, international, controlled multicenter study including 11 centers from six countries, asphyxiated newborn infants with birth weight >999 g were allocated to resuscitation with either room air or 100% oxygen. The study was not blinded, and the patients were allocated to one of the two treatment groups according to date of birth. Those born on even dates were resuscitated with room air and those born on odd dates with 100% oxygen. Informed consent was not obtained until after the initial resuscitation, an arrangement in agreement with the new proposal of the US Food and Drug Administration's rules governing investigational drugs and medical devices to permit clinical research on emergency care without the consent of subjects. The protocol was approved by the ethical committees at each participating center. Entry criterion was apnea or gasping with heart rate <80 beats per minute at birth necessitating resuscitation. Exclusion criteria were birth weight <1000 g, lethal anomalies, hydrops, cyanotic congenital heart defects, and stillbirths. Primary outcome measures were death within 1 week and/or presence of hypoxic–ischemic encephalopathy, grade II or III, according to a modification of Sarnat and Sarnat. Secondary outcome measures were Apgar score at 5 minutes, heart rate at 90 seconds, time to first breath, time to first cry, duration of resuscitation, arterial blood gases and acid base status at 10 and 30 minutes of age, and abnormal neurologic examination at 4 weeks. The existing routines for resuscitation in each participating unit were followed, and the ventilation techniques described by the American Heart Association were used as guidelines aiming at a frequency of manual ventilation of 40 to 60 breaths per minute. Results. Forms for 703 enrolled infants from 11 centers were received by the steering committee. All 94 patients from one of the centers were excluded because of violation of the inclusion criteria in 86 of these. Therefore, the final number of infants enrolled in the study was 609 (from 10 centers), with 288 in the room air group and 321 in the oxygen group. Median (5 to 95 percentile) gestational ages were 38 (32.0 to 42.0) and 38 (31.1 to 41.5) weeks (NS), and birth weights were 2600 (1320 to 4078) g and 2560 (1303 to 3900) g (NS) in the room air and oxygen groups, respectively. There were 46% girls in the room air and 41% in the oxygen group (NS). Mortality in the first 7 days of life was 12.2% and 15.0% in the room air and oxygen groups, respectively; adjusted odds ratio (OR) = 0.82 with 95% confidence intervals (CI) = 0.50–1.35. Neonatal mortality was 13.9% and 19.0%; adjusted OR = 0.72 with 95% CI = 0.45–1.15. Death within 7 days of life and/or moderate or severe hypoxic–ischemic encephalopathy (primary outcome measure) was seen in 21.2% in the room air group and in 23.7% in the oxygen group; OR = 0.94 with 95% CI = 0.63–1.40. Heart rates did not differ between the two groups at any time point and were (mean ± SD) 90 ± 31 versus 93 ± 33 beats per minute at 1 minute and 110 ± 27 versus 113 ± 30 beats per minute at 90 seconds in the room air and oxygen groups, respectively. Apgar scores at 1 minute (median and 5 to 95 percentiles) were significantly higher in the room air group (5 [1 to 6.7]) than in the oxygen group (4 [1 to 7]); however, at 5 minutes there were no significant differences, with 8 (4 to 9) versus 7 (3 to 9). There were significantly more infants with very low 1-minute Apgar scores (<4) in the oxygen group (44.4%) than in the room air group (32.3%). There also were significantly more infants with 5-minute Apgar score <7 in the oxygen group (31.8%) than in the room air group (24.8%). There were no differences in acid base status or Sao2during the observation period between the two groups. Mean (SD) Pao2 was 31 (17) versus 30 (22) mm Hg in cord blood in the room air and oxygen groups, respectively (NS). At 10 minutes Pao2 was 76 (32) versus 87 (49) mm Hg (NS), and at 30 minutes, the values were 74 (29) versus 89 (42) mm Hg in the room air and oxygen groups, respectively. Median (95% CI) time to first breath was 1.1 (1.0–1.2) minutes in the room air group versus 1.5 (1.4 to 1.6) minutes in the oxygen group. Time to the first cry also was in mean 0.4 minute shorter in the room air group compared with the oxygen group. In the room air group, there were 25.7% so-called resuscitation failures (bradycardia and/or central cyanosis after 90 seconds) that were switched to 100% oxygen after 90 seconds. The percentage of resuscitation failures in the oxygen group was 29.8%. Conclusions. This study with patients enrolled primarily from developing countries indicates that asphyxiated newborn infants can be resuscitated with room air as efficiently as with pure oxygen. In fact, time to first breath and first cry was significantly shorter in room air- versus oxygen-resuscitated infants. Resuscitation with 100% oxygen may depress ventilation and therefore delay the first breath. More studies are needed confirming these results before resuscitation guidelines are changed.