Cerebral intravascular oxygenation correlates with mean arterial pressure in critically ill premature infants

Objectives. Premature infants experience brain injury, ie, germinal matrix- intraventricular hemorrhage (GMH-IVH) and periventricular leukomalacia (PVL ), in considerable part because of disturbances in cerebral blood flow (CBF ). Because such infants are susceptible to major fluctuations in mean arter ial blood pressure (MAP), impaired cerebrovascular autoregulation would inc rease the likelihood for the changes in CBF that could result in GMH-IVH an d PVL. The objectives of this study were to determine whether a state of im paired cerebrovascular autoregulation could be identified reliably and conv eniently at the bedside, the frequency of any such impairment, and the rela tion of the impairment to the subsequent occurrence of severe GMH-IVH and P VL. Patients and Methods. To monitor the cerebral circulation continuously and noninvasively, we used near-infrared spectroscopy (NIRS) to determine quant itative changes in cerebral concentrations of oxygenated hemoglobin (HbO(2) ) and deoxygenated hemoglobin (Hb) from the first hours of life. Our previo us experimental study showed a strong correlation between a measure of cere bral intravascular oxygenation (HbD), ie, HbD = HbO(2) = Hb, determined by NIRS, and volemic CBF, determined by radioactive microspheres. We studied 3 2 very low birth weight premature infants (gestational age: 23-31 weeks; bi rth weight: 605-1870 g) requiring mechanical ventilation, supplemental oxyg en, and invasive blood pressure monitoring by NIRS from 1 to 3 days of age. MAP measured by arterial catheter pressure transducer and arterial oxygen saturation measured by pulse oximetry were recorded simultaneously. The rel ationship of MAP to HbD was quantitated by coherence analysis. Results. Concordant changes (coherence scores >. 5) in HbD and MAP, consist ent with impaired cerebrovascular autoregulation, were observed in 17 of th e 32 infants (53%). Eight of the 17 infants (47%) developed severe GMH-IVH or PVL or both. Of the 15 infants with apparently intact autoregulation, ie , coherence scores <.5, only 2 (13%) developed severe ultrasonographic lesi ons. Thus, for the entire study population of 32 infants, 8 of the 10 with severe lesions exhibited coherence scores >. 5. Conclusions. We conclude that NIRS can be used in a noninvasive manner at t he bedside to identify premature infants with impaired cerebrovascular auto regulation, that this impairment is relatively common in such infants, and that the presence of this impairment is associated with a high likelihood o f occurrence of severe GMH-IVH/PVL.