UC Davis

Background

The Neonatal Resuscitation Program (NRP) recommends using 100% O₂ during chest compressions and adjusting FiO₂ based on SpO₂ after return of spontaneous circulation (ROSC). The optimal strategy for adjusting FiO₂ is not known.

Methods

Twenty-five near-term lambs asphyxiated by umbilical cord occlusion to cardiac arrest were resuscitated per NRP. Following ROSC, lambs were randomized to gradual decrease versus abrupt wean to 21% O₂ followed by FiO₂ titration to achieve NRP SpO₂ targets. Carotid blood flow and blood gases were monitored.

Results

Three minutes after ROSC, PaO₂ was 229 ± 32 mmHg in gradual wean group compared to 57 ± 13 following abrupt wean to 21% O₂ (p < 0.001). PaO₂ remained high in the gradual wean group at 10 min after ROSC (110 ± 10 vs. 67 ± 12, p < 0.01) despite similar FiO₂ (~0.3) in both groups. Cerebral O₂ delivery (C-DO₂) was higher above physiological range following ROSC with gradual wean (p < 0.05). Lower blood oxidized/reduced glutathione ratio (suggesting less oxidative stress) was observed with abrupt wean.

Conclusion

Weaning FiO₂ abruptly to 0.21 with adjustment based on SpO₂ prevents surge in PaO₂ and C-DO₂ and minimizes oxidative stress compared to gradual weaning from 100% O₂ following ROSC. Clinical trials with neurodevelopmental outcomes comparing post-ROSC FiO₂ weaning strategies are warranted.

Impact

In a lamb model of perinatal asphyxial cardiac arrest, abrupt weaning of inspired oxygen to 21% prevents excessive oxygen delivery to the brain and oxidative stress compared to gradual weaning from 100% oxygen following return of spontaneous circulation. Clinical studies assessing neurodevelopmental outcomes comparing abrupt and gradual weaning of inspired oxygen after recovery from neonatal asphyxial arrest are warranted.