Editors' ChoicePreterm Birth

Toward personalized medicine for the tiniest patients

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Science Translational Medicine  03 Jun 2015:
Vol. 7, Issue 290, pp. 290ec91
DOI: 10.1126/scitranslmed.aac6310

Maintaining adequate oxygen delivery to the brain is one of the central tasks of the cardiovascular system. A mismatch between cerebral oxygen demand and cerebral perfusion can lead to impaired neurocognitive function, irreversible neurologic damage, and ultimately neuronal cell death. To guard against possible fluctuations in cerebral blood flow, the vasculature of the brain can actively modulate its resistance and thereby regulate its own blood supply—a property termed cerebrovascular autoregulation. This process may be critically underdeveloped in babies born prematurely.

With impaired autoregulation, arterial hypotension leads to uncompensated cerebral hypoperfusion, resulting in hypoxic-ischemic injury to the brain. Arterial hypertension, on the other hand, may lead to distention and rupture of fragile cerebral blood vessels, resulting in a hemorrhagic injury. The key, therefore, is to keep arterial blood pressure “normal” in premature babies. But what is the normal blood pressure for a 750 g newborn that was delivered 14 weeks too early and whose mean arterial pressure (MAP) measures a mere 29 mm Hg? A rational approach to personalized hemodynamic management in this vulnerable population is currently lacking.

To close this gap, da Costa and colleagues evaluated a new index of cerebrovascular autoregulation. This index was the correlation coefficient between slow-wave fluctuations in tissue oxygenation (measured by near-infrared spectroscopy) and heart rate. A low absolute value of the correlation coefficient indicated intact cerebrovascular autoregulation. The authors defined an optimal blood pressure for an individual baby as the MAP value of the baby corresponding to the lowest associated value of the new autoregulation index, thus maximizing the brain’s autoregulatory capacity.

In a cohort of 60 preterm babies, the authors were able to demonstrate that babies with measured MAPs significantly below the calculated individualized optimal blood pressure had an increased rate of mortality, whereas those with MAPs exceeding the optimal blood pressure suffered from more severe cerebral hemorrhage. Their results suggest that personalization of hemodynamic management may be possible by titrating blood pressure so as to maximize a baby’s autoregulatory capacity. Given the potential for severe and lifelong disability stemming from brain injury early in life, these results are encouraging and call for prospective validation to improve the care of the tiniest and most fragile of patients.

C. S. da Costa et al., Monitoring of cerebrovascular reactivity for determination of optimal blood pressure in preterm infants. J. Pediatr. 10.1016/j.jpeds.2015.03.041 (2015). [Abstract]

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