O0696 Oct.3: 3:35pm - Optimal Inspired Oxygen Weaning Strategy Following Return of Spontaneous Circulation After Perinatal Asphyxial Arrest.

Background: Early hyperoxemia in neonates with perinatal acidemia is associated with higher incidence of hypoxic-ischemic encephalopathy (Kapadia et al J Peds 2013). Hence, judicious use of oxygen (O2) during resuscitation is warranted. In neonatal cardiac arrest at term gestation, current NRP guidelines recommend initiation of positive pressure ventilation (PPV) with 21% O2 and titration based on SpO2, but 100% O2 during chest compressions (CC). However, following return of spontaneous circulation (ROSC), a combination of hyperemia (due to hypercarbia) and hyperoxia can result in cerebral oxidative stress and reperfusion injury.

Objective: Abrupt weaning of inspired O2 to 21% after ROSC followed by upward titration (21%O2-titrate up) will limit hyperoxia without altering cerebral oxygen delivery (C-DO2) compared to gradual weaning from 100% O2 with titration (100%O2-wean down) based on target preductal SpO2 of 85-95% in term lambs with cardiac arrest induced by umbilical cord occlusion.
Design/

Methods: Asphyxia was induced in 25 term lambs by umbilical cord occlusion. PPV was initiated after 5min of asystole with 21% O2, with increase to 100% with CC. After ROSC, lambs were randomized to either (a) abrupt weaning of inspired O2 to 21% which was then titrated upwards or (b) gradual weaning of inspired O2 downwards from 100% O2 to achieve NRP recommended target preductal SpO2 of 85-95% in both groups. Hemodynamics and blood gases were recorded for 10min after ROSC.

Results: Out of 25 lambs in asphyxial arrest, 13 were randomized to 21%O2-titrate up and 12 to 100%O2-wean down. Arterial hemoglobin, lactate and PaO2 at arrest and C-DO2 during CC were similar between the groups (table 1). PaO2 at 3 min after ROSC was 229±110mmHg in 100%O2-wean down compared to 57±41 in 21%O2-titrate up (p<0.001) and continued to be significantly higher at 10min after ROSC (110±33 vs. 67±37, p<0.01) in spite of similar FiO2 at 10min (figure 1). Although mean C-DO2 was similar during CC, following ROSC it was higher and above physiological range in 100%O2-wean down compared to 21%O2-titrate up (p<0.05, figure 2).
Conclusion(s): The simple intervention of abrupt weaning to 21% O2 after ROSC in neonatal asphyxial arrest may limit excessive PaO2 levels. However, C-DO2 attained with 100%O2-wean down approach are higher and above the physiological range in healthy term lambs (1.98 to 3.55ml/kg/min). Clinical studies with long term follow up are needed to determine the impact of weaning strategy following ROSC on cerebral oxidative stress and neurodevelopmental outcome.