Preterm neonatal cardiovascular instability: does understanding the fetus help evaluate the newborn?

Preterm newborns, particularly very low birth weight newborns, frequently experience intermittent hypotension and/or hypoperfusion. Organ perfusion is largely distinct from systemic hypotension, suggesting that changes in underlying vascular tone are the major determinants of perfusion. Preterm fetuses have a remarkable anaerobic tolerance and ability to survive major insults with no or limited injury, balanced by relative immaturity of key autonomic responses. Exposure to hypoxia-ischaemia and infection trigger complex changes in vascular tone that evolve over many days and there is evidence that these are centrally controlled and linked, in part, with underlying organ metabolism. Hypoperfusion frequently occurs after hypoxia-ischaemia without organ injury occurring. Hypoxia-ischaemia, infection and many clinical interventions, such as steroid therapy and ventilation, can interact to increase or decrease the risk of brain injury.