Cerebral Oxygenation Is Highly Sensitive to Blood Pressure Variability in Sick Preterm Infants

Abstract

ObjectivesThe significance of blood pressure variability (BPV) for cerebral oxygenation in extremely preterm infants has not been explored, though BPV may well be associated with end organ injury. We hypothesized that increased BPV in sick preterm infants, by exceeding the cerebral autoregulatory capacity, is associated with cerebral oxygenation changes which closely follow the blood pressure fluctuations. We assessed the autoregulatory capacity in the early postnatal period, by determining the correlation between BPV (mmHg2) and coherence of mean arterial blood pressure (MABP mmHg) and cerebral oxygenation (tissue oxygenation index, TOI %).Study DesignThirty-two preterm infants of mean gestational age of 26.3 (±1.5) weeks were studied on the first 3 postnatal days. Spectral analysis (Coherence and transfer-function gain analysis) was used to calculate coherence of MABP and TOI; BPV was quantified using power spectral density of MABP.ResultsOverall, maximum Coherence showed a trend for positive correlation with BPV (n = 32, p = 0.06). Infants identified as clinically unstable with documented brain injury (n = 7) had high Coherence values at low BPV. Separate analysis of stable infants (excluding the 7 critically ill infants) revealed a significant association between maximum Coherence and BPV (n = 25, p = 0.006).ConclusionsFluctuation in cerebral oxygenation is closely associated with increased BPV in preterm infants undergoing intensive care. Moreover, in the critically sick preterm infant, blood pressure-dependent variations in cerebral oxygenation occur even with relatively lower BPV, suggesting they have severely impaired autoregulation, and placing them at greater vulnerability to cerebral injury arising from blood pressure fluctuations.

Fast Doppler as a novel bedside measure of cerebral perfusion in preterm infants

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Cerebral autoregulation in the preterm newborn using near-infrared spectroscopy: a comparison of time-domain and frequency-domain analyses

“…19 Phase shift has not been reported for studies of CA in neonates based on spontaneous fluctuations in MAP. 8,10,[20][21][22][23] This might be due to the fact that the interpretation of phase over a frequency range is difficult. What does the average phase shift in a frequency band actually mean?…”

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“…Increased systemic cytokines in premature infants with chorioamnionitis are associated with hemodynamic disturbances leading to cerebral hypoxia/ischemia, whereas co-morbid chorioamnionitis and placental perfusion defect put preterm infants at higher risk of abnormal neurologic outcomes than either insult alone [7,8,9]. Similarly, animal studies have demonstrated systemic inflammation induced by lipopolysaccharide sensitizes hypoxic/ischemic injury in the immature brain [10].…”