Relationship between cerebrovascular dysautoregulation and arterial blood pressure in the premature infant

Abstract

Objective: To evaluate cerebrovascular autoregulation as a function of arterial blood pressure (ABP) in the critically ill, premature infant.Study Design: A prospective observational pilot study was conducted in two tertiary care Neonatal Intensive-Care Units. Premature infants (n ¼ 23, p30 weeks estimated gestational age with invasive ABP monitoring) were enrolled and received routine care while undergoing continuous autoregulation monitoring, using the cerebral oximetry index (COx). The COx is a moving, linear correlation coefficient between cortical reflectance oximetry and ABP. COx values were stratified as a function of ABP for individual subject recordings and for the cohort.Result: The mean duration of autoregulation monitoring was 3.2 days (median: 2.97, range: 0.61-3.99). A total of 10 of 23 (43%) developed intraventricular hemorrhage and 1 of 23 (4%) developed periventricular leukomalacia by head ultrasound. No association was found between neurologic injury and percentage of the monitoring periods with autoregulation impairment (defined as COx>0.5). Lower ABP was associated with dysautoregulation (higher COx values, P<0.01). The percentage of time with impaired autoregulation was greater with lower ABP (P ¼ 0.013, Spearman r ¼ 0.51).Conclusion: All infants studied had periods with intact and periods with impaired cerebrovascular autoregulation, measured with the COx. Low ABP was associated with impaired autoregulation.

Respiratory support for premature neonates in the delivery room: effects on cardiovascular function and the development of brain injury

“…We recently demonstrated that the initiation of high V T ventilation for the first 15 min after birth caused large fluctuations in CBF (Figure 3), impaired cerebral autoregulation (cerebral vasoparalysis), and increased vascular extravasation (leakage), a precursor to cerebral hemorrhage (4). Abnormal fluctuations in CBF (defined as prolonged swings in CBF, either high or low, for more than 10-20 s) are common in preterm infants (37) and occur as a result of adverse pulmonary, cardiovascular, or systemic (vascular) factors. The majority of abnormal CBF is due to impaired cardiovascular control (38).…”

Measuring cerebrovascular autoregulation in preterm infants using near-infrared spectroscopy: an overview of the literature

“…Soul et al found impaired cerebrovascular autoregulation in about 20% of the recording time using NIRS in 87 out of 90 very preterm infants during the first 5 days after birth [29]. Other studies also reported on fluctuating autoregulation impairment during the first days after birth [6,[30][31][32][33].…”

“…Munro et al reported that the lower threshold in MABP for cerebrovascular autoregulation, measured by NIRS, might be at 29 mmHg for preterm infants with a GA ranging from 23 to 30 weeks [46]. Other studies were not able to define a clear lower threshold for their cohorts but used a large change in magnitude or percentage of time of impaired cerebrovascular autoregulation to define dangerous MABP levels [29,30]. In contrast, Binder et al found that a 1-h hypotensive episode (defined as an MABP below the infant's GA) did not affect NIRS rSO 2 significantly in preterm infants with a GA <37 weeks [47].…”

“…Indeed, increased COx values occurred at lower MABP values, and lower MABP values were associated with longer periods of impaired cerebrovascular autoregulation (COx values >0.5). Preterm infants born with a lower GA had lower MABP values but unexpectedly did not show an increased duration with impaired cerebrovascular autoregulation [30]. Thirteen studies have used the TOx or COx technique for cerebrovascular autoregulation assessment in preterm infants (Table 1).…”

“…In 2011, Gilmore et al introduced the term COx in a preterm population, which is essentially the same as the TOx index, but using rSO 2 as a measure of cerebral oxygenation [30]. A cutoff value of 0.5 was used to delineate intact from impaired states of cerebrovascular autoregulation in 23 preterm infants (GA <30 weeks) with invasive MABP monitoring.…”