NEONATAL RESUSCITATION ASPHYXIA RESPONSE

neonatal resuscitation - Response to asphyxia
The fetus or newborn that is subjected to asphyxia begins a diving reflex (so termed because of certain similarities to the physiology of diving seals) in an attempt maintain perfusion and oxygen delivery to vital organs. Pulmonary vascular resistance increases, leading to a decreased pulmonary blood flow and increased blood flow directly to the left atrium.

Systemic cardiac output is redistributed, with increased flow to the heart, brain, and adrenal gland and decreased flow to the rest of the body. Early in asphyxia systemic blood pressure increases. However, with ongoing hypoxia and acidosis, the myocardium fails and the blood pressure begins to decrease, leading to tissue ischemia and hypoxia.

Infants who are undergoing asphyxia have an altered respiratory pattern. Initially, they have rapid respirations. These respiratory efforts eventually cease with continued asphyxia (termed primary apnea).

During primary apnea, the infant responds to stimulation with reinstitution of breathing. However, if the asphyxia continues, the infant then begins irregular gasping efforts, which slowly decrease in frequency and eventually cease (termed secondary apnea). Infants who experience secondary apnea do not respond to stimulation and require positive pressure ventilation to restore ventilation.

Primary and secondary apnea cannot be clinically distinguished. Therefore, if an infant does not readily respond to stimulation, positive pressure ventilation should be instituted as outlined in the Neonatal Resuscitation Program guidelines. If an infant is experiencing primary apnea, the stimulation of the ventilatory efforts cause the infant to resume breathing.

If the infant is in secondary apnea, positive pressure ventilation is required for a period. The longer the infant is asphyxiated, the longer the onset of spontaneous respirations is delayed following the initiation of effective ventilation through the use of positive pressure ventilation.