Hypotensive Extremely Low Birth Weight Infants Have Reduced Cerebral Blood Flow

Abstract

In ELBW infants (1) cerebral autoregulation is functional in normotensive but not hypotensive infants; (2) a breakpoint exists at approximately 30 mm Hg in the CBF-MAP autoregulation curve; and (3) dopamine improves both MAP and CBF.

Management of hypotension and low systemic blood flow in the very low birth weight neonate during the first postnatal week

“…During the first postnatal day, this number is generally considered to be equal to the numerical number of the given patient's gestational age. However, most [2][3][4] but not all 5 studies using 133 Xe clearance or near infrared spectroscopy (NIRS) to assess changes in cerebral blood flow (CBF) have found that the lower limit of the autoregulatory blood pressure range may be around 30 mm Hg even in the 1-day-old extremely low birth weight (ELBW) neonate. These findings are supported by observations made by the use of ultrasonography.…”

“…3,5,9,22 Management of this presentation of circulatory compromise is difficult and findings in the literature are somewhat contradictory. In a well-executed series using SVC blood flow as a surrogate measure of CBF in VLBW neonates during the first postnatal day, Evans, Kluckow, Osborn and colleagues described the hemodynamics of systemic and cerebral hypoperfusion, 7,8 the relationship between recovery from hypoperfusion and the development of IVH, 8 the weak relationship between SVC blood flow and systemic blood pressure 8 and the association between neurodevelopmental outcome at 3 years of age and low SVC blood flow during the first 24 postnatal hours.…”

“…22 Finally, recent findings using multiple, noncontinuous measurements of CBF by NIRS to assess the response of CBF and blood pressure to dopamine in ELBW neonates during the first two postnatal days also suggest that these patients respond to moderate-to-high doses of dopamine with an increase in both the blood pressure and CBF. 3 However, although CBF returns to the presumed normal range as blood pressure normalizes, its autoregulation remains impaired. Indeed, findings of an earlier study support this notion and indicate that, in sick preterm neonates, it may take up to 30-40 min or more for CBF autoregulation to recover after blood pressure has been normalized.…”

“…28 In summary, treatment of the hypotensive 1-day-old VLBW neonate remains complex even if systemic perfusion can be assessed by functional echocardiography. The use and stepwise titration of low-to-moderate dose dopamine 3,6,20,22,28 or epinephrine 22 to achieve blood pressure values 3 to 6 points higher than the gestational age of the patient is the preferred approach by many neonatologists during the first postnatal day. However, if there is evidence of myocardial dysfunction, dobutamine should be the first-line medication and low-dose dopamine may be added if blood pressure decreases upon initiation of dobutamine administration.…”

Definition of hypotension and assessment of hemodynamics in the preterm neonate

“…We do not know the mean arterial blood pressure value at which cerebrovascular autoregulation is lost in the preterm infant, although recent studies suggest that it may be as high as 28 to 30 mm Hg in even extremely low birth weight infants ( Figure 2). 22 There is an association between the loss of autoregulation, the resultant CBF fluctuations, and morbidity and mortality in preterm infants. 12,16,21 However, according to the physiological model (Figure 1), cerebral cellular function and structural integrity are not affected at the autoregulatory threshold, and association does not imply causation.…”