Current neonatal resuscitation guidelines recommend a 3:1 ratio of chest compressions (CC) to ventilations (i.e. 90 CC/min and 30 breaths/min) and that CC be started when the heart rate (HR) is less than 60 beats per minute after a minute of effective positive pressure ventilation. Outcomes for neonates requiring CC after delivery are poor; this may be due in part to the lower than physiologic heart rate or to delays in initiating CC. In neonates, heart rate is the primary determinant of cardiac output. Two key questions remain unresolved: 1) would achieving a higher rate of CC (i.e., 120/min with continuous CC and asynchronous ventilations at 30/min) increase blood flow to essential organs compared to the traditional 3:1 CC and ventilation resuscitation, and 2) what is the optimum HR at which to initiate CC? Given the unique challenges related to transition from fetal circulation to neonatal circulation (egress of fetal lung liquid and the impact of circulatory shunts through the ductus venosus and ductus arteriosus), the perinatal asphyxial cardiac arrest fetal lamb model is ideal to address these key questions. Relevance Most studies on neonatal resuscitation stem from manikin models that fail to truly reflect physiologic changes or piglet models that have cleared their lung fluid and that have undergone transition of their fetal circulation. The current evidence on C:V ratio and the optimal heart rate when to initiate CC remains weak. We propose to conduct the first study to evaluate continuous, uninterrupted CC in a newborn perinatal asphyxiated lamb model with transitioning circulation and fluid-fill lungs closely matching the newborn in the delivery room. Our findings could change the standard of care for neonatal resuscitation and improve outcomes in newborns with severe perinatal compromise.
In the severely asphyxiated newborn, ventilation may not be sufficient and chest compressions (CC) may be required for successful resuscitation, while the optimal compression-to-ventilation (C:V) ratio remains unknown. This study will compare the hemodynamic variables and time to achieve return of spontaneous circulation during continuous CC with asynchronous ventilation to the current recommended 3:1 C:V resuscitation in a perinatal asphyxiated cardiac arrest lamb model. The results of this study could change the standard of care for neonatal resuscitation and improve outcomes in infants delivered with severe perinatal compromise.
