The Influence of Abnormal Blood Gases on Cerebral Blood Flow Velocity in the Preterm Newborn

“…Thus, in contrast to MABP-CBF autoregulation, "constancy of CBF" is not always synonymous with "healthy regulation of CBF." Acute changes in Pcoz should be avoided because they may trigger brain lesions by inducing hyper-or hypoperfusion (8). especially with normal Pco2-CBF autoregulation.…”

Section: Discussionmentioning

confidence: 99%

Simultaneous Influence of Blood Pressure, Pco2, and Po2 on Cerebral Blood Flow Velocity in Preterm Infants of Less than 33 Weeks' Gestation

et al. 1993

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“…NIRS examinations were performed shortly after enrollment, after 24 and 48 h, and on d 7 of life. Because indomethacin decreases cerebral blood flow velocities (13,14) for up to 2 h (13), infants receiving indomethacin were examined either before or more than 4 h after indomethacin administration.…”

Section: Methodsmentioning

confidence: 99%

Variability in Cerebral Oxygen Delivery Is Reduced in Premature Neonates Exposed to Chorioamnionitis

et al. 2006

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Premature infants exposed to chorioamnionitis are at increased risk for periventricular leukomalacia (PVL) and intraventricular hemorrhage (IVH), lesions that may result from inflammation and/or fluctuations in cerebral blood flow. The effect of chorioamnionitis on near-infrared spectroscopy (NIRS) measures of cerebral oxygen delivery has not been evaluated previously. Forty-nine infants born at 25-31 6/7 wk gestation underwent NIRS examination on d 1, 2, 3, and 7 of life. Variability in NIRS tracings was analyzed by partitioning each tracing into three components: long-term, intermediate, and short-term variability; the latter two components were analyzed. Chorioamnionitis-exposed infants manifest reduced intermediate variability in cerebral oxygenated and deoxygenated Hb but not total Hb. Infants with severe IVH/PVL had the lowest intermediate variability on d 1. Short-term variability was similar between chorioamnionitis-exposed and unexposed infants, and between infants with versus without severe IVH or PVL. We conclude that intermediate-term variability in NIRS cerebral oxygen delivery is reduced in chorioamnionitis-exposed infants. We speculate that intermediate variability represents the important time frame for evaluating the pathogenesis of perinatal brain injury. Further studies are needed to determine how these findings relate to cerebral blood flow autoregulation and oxygen utilization in premature infants. C horioamnionitis is perhaps the most common cause of premature delivery. Recent epidemiologic and clinical investigations indicate that premature infants who are exposed to chorioamnionitis are at increased risk for developing IVH (1), PVL (1,2), and cerebral palsy (2-4). The etiology of the white matter injury in chorioamnionitis-exposed infants remains uncertain but likely involves some component of ischemic (5-8) and/or inflammatory (9,10) damage to the developing oligodendroglia. It has been demonstrated that preterm infants who develop IVH have fluctuations in Doppler-derived cerebral blood flow velocities (11). With the application of NIRS, it became evident that infants with both IVH and PVL have fluctuations in cerebral oxygen delivery (12) that correlate with fluctuations in blood pressure and indicate impaired cerebral autoregulatory ability (11). The relationship between variability in NIRS measures of cerebral oxygen delivery and exposure to chorioamnionitis has not been evaluated previously.The overall objective of this investigation was to determine the variability among NIRS measures of cerebral oxygen delivery in premature infants exposed and unexposed to chorioamnionitis. We first devised a method that would allow us to assess both intermediate and short-term variability in NIRS measures of cerebral oxygenated, deoxygenated, and total Hb. Next, we tested the hypothesis that variability decreases with increasing gestational and postnatal age, as the risk of IVH and PVL abate. Finally, we compared variability in NIRS measures of cerebral oxygen delivery between infants ex...

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“…PaCO 2 is now generally considered to be the most influential regulator of the cerebral circulation (14), and, although the exact mechanism of the response is not known, the physiologic basis for it is well understood. CO 2 is one of the major products of cellular metabolism.…”

mentioning

confidence: 99%

Quantitative Near Infrared Spectroscopy Measurement of Cerebral Hemodynamics in Newborn Piglets

et al. 2002

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Severely premature infants are often at increased risk of cerebral hemorrhage and/or ischemic injury caused by immature autoregulatory control of blood flow to the brain. If blood flow is too high, the infant is at risk of hemorrhage, whereas too little blood flow can result in ischemic injury. The development of a noninvasive, bedside means of measuring cerebral hemodynamics would greatly facilitate both diagnosis and monitoring of afflicted individuals. It is to this end that we have developed a near infrared spectroscopy (NIRS) system that allows for quantitative, bedside measurement of cerebral blood flow (CBF), cerebral blood volume (CBV), and mean transit time (MTT). The technique requires an i.v. injection of the near infrared chromophore indocyanine green. Six newborn piglets, median age of 18 h (range 6 -54 h), median weight of 1.75 kg (range 1.5-2.1 kg), were studied. Measurements of CBF, CBV, and MTT were made at normocapnia, hypocapnia, and hypercapnia to test the technique over a range of hemodynamic conditions. The accuracy of our new approach has been determined by direct comparison with measurements made using a previously validated computed tomography technique. Paired t tests showed no significant difference between computed tomography and NIRS measurements of CBF, CBV, and MTT, and mean biases between the two methods were Ϫ2.05 mL·min Ϫ1 ·100 g Ϫ1 , Ϫ0.18 mL·100 g Ϫ1 , and 0.43 s, respectively. The precision of NIRS CBF, CBV, and MTT measurements, as determined by repeatedmeasures ANOVA, was 9.71%, 13.05%, and 7.57%, respectively. Since the first publication by Jobsis in 1977 (1), NIRS has been used in a variety of studies to investigate cerebral hemodynamics (2, 3). The underlying principles behind the use of NIRS to probe biologic media are relatively simple and have been described in detail elsewhere (1, 4 -8). There exist in biologic tissue four endogenous near infrared (NIR) light absorbers-oxy-Hb (HbO 2 ), deoxy-Hb (Hb), cytochrome oxidase (Cyt), and water. Because HbO 2 and Hb are generally present at relatively low concentrations in tissue, NIR light is able to penetrate tissue to a greater extent than other low-energy forms of light, in some cases up to distances of 8 -9 cm (6).As NIR light enters tissue, it is multiply scattered. The result of this scatter is that the total path length traveled by the NIR light is greater than the physical distance between the points of emission and detection. This extra distance can be accounted for using the differential path length factor (DPF), first described by Delpy et al. (9). With accurate knowledge of the DPF, a modified version of the Beer-Lambert law can be used to determine absolute changes in concentrations of NIR absorbers within tissue:where ⌬c is the change in concentration, ⌬A is the change in attenuation, ␣ is the extinction coefficient, L is the physical distance between emission and detection of NIR light, and B is the DPF. Measurement of concentration changes over time can

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The Influence of Abnormal Blood Gases on Cerebral Blood Flow Velocity in the Preterm Newborn

Cited by 44 publications

References 22 publications

Simultaneous Influence of Blood Pressure, Pco2, and Po2 on Cerebral Blood Flow Velocity in Preterm Infants of Less than 33 Weeks' Gestation

Simultaneous Influence of Blood Pressure, Pco2, and Po2 on Cerebral Blood Flow Velocity in Preterm Infants of Less than 33 Weeks' Gestation

Variability in Cerebral Oxygen Delivery Is Reduced in Premature Neonates Exposed to Chorioamnionitis

Quantitative Near Infrared Spectroscopy Measurement of Cerebral Hemodynamics in Newborn Piglets

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