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Hypotension and Brain Injury
Limperopoulos C, Bassan H, Kalish L et al. Current Definitions of Hypotension Do Not Predict Abnormal Cranial Ultrasound Findings in Preterm Infants. Pediatrics 2007 120: 966-977. [Full text] [PDF]
Objective. 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.
Methods. We prospectively measured
mean arterial pressure in 84 infants who were 
30
weeks’ gestational age. 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.
Results. 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 
27
weeks’ gestational age and those with lower illness severity scores.
Conclusions. 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.
Comments.
Brain injury remains a significant cause of both morbidity and mortality in infants who are born prematurely. Two major factors that contribute to the development of brain injury are (1) loss of cerebral autoregulation and (2) abrupt alterations in cerebral blood flow and pressure. This study addressed almost all factors contributing to brain injury in premature infants. The authors used3 existing definitions of hypotension; (MAP [1] <30 mmHg, [2] less than the infant's GA, and [3] <10th percentile of MAP for birth weight and postnatal age. The analysis showed lack of association between hypotension defined by these criteria and abnormal cranial ultrasound findings. However, volume expander use on day 2 was significantly associated with overall abnormal ultrasound findings (P = .03), and volume expander use on day 3 was significantly associated with all abnormal ultrasound outcomes (P < .005 for each outcome). There was no significant association between abnormal cranial ultrasound findings and pressor-inotrope treatment. Several variables were tested and did not seem to exert a confounding effect on the relationship between BP and abnormal cranial ultrasound finding. I agree with authors that other factors could play a rule in causing brain injury because the study populations were sicker as well the techniques used for BP measurement and analysis were not sufficiently sensitive to detect this association. SAA.
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