What is a sufficient blood pressure in the preterm newborn?

Hypotension is diagnosed in a high percentage of very low birth weight infants, particularly in the first 24 hours after birth and the resultant clinical approach is to support the blood pressure vigorously. However, the research base is not yet available to give a definite answer to the question, which blood pressure is really unacceptable in a given clinical situation. The clinical approach usually relies on reference blood pressure data or on clinical considerations. Reference blood pressure ranges established from observations of rather stable preterm infants and commonly used in "normal" premature infants are age- and weight related so-called "normal" blood pressures and "rules of thumb" while cerebral autoregulation adapted or outcome related lower limits of arterial blood pressure could be promising alternatives. Clinical signs, results of laboratory studies and cardiac function monitoring are tools used in stable and unstable premature infants for assessing if an acute blood pressure is adequate to prevent tissue malperfusion. In this rather unsatisfactory situation there is a growing body of evidence that also in premature infants systemic or regional blood flow and not blood pressure are the crucial hemodynamic parameters and that also in this age group there is at best a weak correlation between mean arterial blood pressure and left ventricular output or regional blood flow.