Current definitions of hypotension do not predict abnormal cranial ultrasound findings in preterm infants

Hypotension is a commonly treated complication of prematurity, although definitions and management guidelines vary widely. Our goal was to examine the relationship between current definitions of hypotension and early abnormal cranial ultrasound findings.

We prospectively measured mean arterial pressure in 84 infants who were < or = 30 weeks' gestational age and had umbilical arterial catheters in the first 3 days of life. Sequential 5-minute epochs of continuous mean arterial pressure recordings were assigned a mean value and a coefficient of variation. We applied to our data 3 definitions of hypotension in current clinical use and derived a hypotensive index for each definition. We examined the association between these definitions of hypotension and abnormal cranial ultrasound findings between days 5 and 10. In addition, we evaluated the effect of illness severity (Score for Neonatal Acute Physiology II) on cranial ultrasound findings.

Acquired lesions as shown on cranial ultrasound, present in 34 (40%) infants, were not predicted by any of the standard definitions of hypotension or by mean arterial pressure variability. With hypotension defined as mean arterial pressure < 10th percentile (< 33 mmHg) for our overall cohort, mean value for mean arterial pressure and hypotensive index predicted abnormal ultrasound findings but only in infants who were > or = 27 weeks' gestational age and those with lower illness severity scores.

Hypotension as diagnosed by currently applied thresholds for preterm infants is not associated with brain injury on early cranial ultrasounds. Blood pressure management directed at these population-based thresholds alone may not prevent brain injury in this vulnerable population.