Effect of carbon dioxide on background cerebral electrical activity and fractional oxygen extraction in very low birth weight infants just after birth

Victor, Suresh; Appleton, Richard; Beirne, M; Marson, Anthony G; Weindling, A M

doi:10.1203/01.pdr.0000169402.13435.09

Cited by 63 publications

(60 citation statements)

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“…Abnormal background EEG activity characterized by prolonged interburst intervals has been linked to adverse neurologic outcome (22,23). The negative correlation between PaCO 2 and the relative power of the delta band suggested slowing of the EEG with hypocarbia (24). Suppression or prolonged discontinuity of the EEG occurred at MBP levels below 23 mm Hg (25).…”

Section: Discussionmentioning

confidence: 99%

The Relationship between Cardiac Output, Cerebral Electrical Activity, Cerebral Fractional Oxygen Extraction and Peripheral Blood Flow in Premature Newborn Infants

et al. 2006

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Cardiac output is a determinant of systemic blood flow and its measurement may therefore be a useful indicator of abnormal hemodynamics and tissue oxygen delivery. The purpose of this study was to investigate in very premature newborn infants the relationships between cardiac output (left and right ventricular outputs), systemic blood pressure, peripheral blood flow (PBF) and two indicators of cerebral oxygen delivery (cerebral electrical activity and cerebral fractional oxygen extraction (CFOE)). This was a prospective observational study performed on 40 infants of less than 30 wk gestation. Digital electroencephalograms (EEGs) were recorded for one hour every day during the first four days after birth and subjected to qualitative and quantitative analysis. Left and right ventricular outputs, mean blood pressure (MBP), CFOE, PBF and arterial blood gases were measured at the same time. Within the ranges studied, there was no apparent relationship between left or right ventricular output (RVO), PBF and indicators of cerebral perfusion (cerebral electrical activity and CFOE). The EEG was normal in infants with low left and right ventricular outputs (Ͻ150 mL/kg/min) and MBP Ͼ 30 mm Hg. Infants with low cardiac output and normal MBP seem able to maintain cerebral perfusion, possibly through vasodilatation of the cerebral microvasculature. Clinicians rely on its absolute value to guide therapy and the prescription of volume expanders and inotropes. However, systemic blood pressure is the product of systemic vascular resistance and cardiac output and is not a direct indicator of the systemic blood flow. Nevertheless, the clinician's approach is based on the assumption that hypotension causes decreased organ perfusion, including that of the brain, resulting in tissue damage. Furthermore, the relationship between MBP and cerebral blood flow remains unclear (1,2); it is presumed that cerebral blood flow is preserved by autoregulation even in very preterm babies but the limits of autoregulation are uncertain.Although cardiac output might reasonably be expected to be a major determinant of systemic blood flow (and therefore of tissue oxygen delivery), the relationship is not a simple one.Thus, a study of preterm infants with closed or insignificant patent ductus arteriosus, showed a weak but significant correlation between mean blood pressure (MBP) and left ventricular output (LVO) overall, but LVO was normal for some babies with low MBP, while for others MBP was normal when ventricular output was low (3).There have been relatively few studies of the relationship between cardiac output and cerebral perfusion in the human preterm infant. A recent study of infants between 24 and 30 wk gestation measured cerebral fractional oxygen extraction (CFOE) as a proxy measure of cerebral oxygen delivery: CFOE is increased when cerebral oxygen delivery is low. There was a weak but significant negative correlation between LVO and cerebral fractional oxygen extraction (4). Infants were particularly vulnerable to poor cerebral o...

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Section: Discussionmentioning

confidence: 99%

The Relationship between Cardiac Output, Cerebral Electrical Activity, Cerebral Fractional Oxygen Extraction and Peripheral Blood Flow in Premature Newborn Infants

et al. 2006

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“…If, in fact, the hypercapnic-induced increase in cerebral blood flow was greater than that we recorded with laser-Doppler, CMRO 2 would not decrease as much, or perhaps even remain constant. One study also demonstrated that in very low birth weight newborns (birth weight Ͻ1500 g, gestation Ͻ30 wk), elevated PaCO 2 levels were associated with suppression of electroencephalographic activity (25). Nonetheless, this issue is controversial.…”

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Fetal Hypercapnia and Cerebral Tissue Oxygenation: Studies in Near-Term Sheep

2006

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The precise role of CO 2 in cerebral oxygenation is not as well defined as O 2 , especially in the immature brain. In the ovine fetus, we tested the hypotheses that arterial PCO 2 (PaCO 2 ) plays a critical role not only in the regulation of cerebral blood flow but also in the regulation of cerebral tissue oxygenation. I n the developing fetus and newborn infant, as well as the adult, the maintenance of optimal cerebral oxygenation is of critical importance, as the brain is highly dependent on a continuous and adequate O 2 supply to maintain structural and functional integrity. Cerebral tissue oxygenation is maintained and carefully regulated by the balance of several factors. These include CBF, arterial O 2 partial pressure (PaO 2 ) and content, cerebral metabolic rate for O 2 (CMRO 2 ), and the relative position of the Hb-oxygen dissociation curve (1,2). Arterial CO 2 tension (PaCO 2 ) long has been recognized as playing a major role in CBF regulation of the fetus (3) as well as the adult (4,5). Thus, it is reasonable to anticipate that CO 2 , as well as O 2 , plays a significant role in cerebral tissue oxygenation.Variation of PaCO 2 commonly occurs in the management of the fetus and newborn during the perinatal period. During labor, fetal hypercapnia with respiratory acidosis, in part resulting from transient compression of the umbilical cord, is not uncommonly seen (6). In addition, vaginal delivery itself may be associated with respiratory acidosis and hypoxia (7). Alternatively, with moderate to severe maternal hyperventilation, particularly during the later stages of labor, fetal hypocapnia with respiratory alkalosis may develop (8,9). In addition, among critically ill newborn infants, significant changes in PaCO 2 can present problems. Under some circumstances, hypocapnia is believed to be of value to prevent an excessive increase in CBF. In other instances, "permissive" hypercapnia is practiced to optimize CBF, to reduce the risk of periventricular leukomalacia, and to minimize ventilator-associated lung injury (10). Nonetheless, despite the critical importance of these issues, and knowledge that cerebrovascular PaCO 2 reactivity differs dramatically between the immature and mature organism (11), the role of CO 2 in cerebral tissue oxygenation has received relatively little attention, especially in the immature brain. (12)(13)(14). MATERIALS AND METHODSExperimental animals and instrumentation. For these studies, we used six pregnant Western ewes and their singleton fetuses obtained from Nebeker Ranch (Lancaster, CA). All surgical and experimental procedures were performed within the regulations of the Animal Welfare Act, the National Institutes of Health Guide for the Care and Use of Laboratory Animals, "The Guiding Principles in the Care and Use of Animals" approved by the Council of the American Physiologic Society, and the Animal Care and Use Committee of Loma Linda University.Pregnant ewes and their fetuses were instrumented at 122 Ϯ 3 d of gestation (term 145 d), as we have described in...

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“…The effects of pH, PcO 2 , and blood glucose concentration on EEG when babies are more than 48 h old differ from those noted in previous studies conducted during the first 48 h after birth. Victor et al (9) showed that lower levels of PcO 2 were associated with increased cerebral fractional oxygen extraction and slowing of EEG, while higher levels of PcO 2 were associated with suppression of EEG during the first 48 h of age. Granot et al (13) using amplitude integrated EEG on 65 preterm babies born before 28 wk gestational age showed that respiratory acidosis and hyperglycemia during the first 72 h after birth was associated with suppressed electrical activity.…”

Section: Permissive Hypercapnia and Eegmentioning

confidence: 99%

“…Prolonged EEG IBIs of more than 30 s in preterm infants born at less than 28 wk gestation and more than 25 s in preterm infants born at more 28 wk gestation have been associated with increased incidence of death or developmental motor abnormalities (6,7). EEG has been studied in relation to age, hypotension, hypo and hypercapnia, and cardiac output in preterm babies born before 30 wk gestation during the first 72 h after birth (8)(9)(10)(11). Lower levels of blood carbon dioxide have been associated with slowing of cerebral electrical activity and increased cerebral fractional oxygen extraction, while hypercapnia was associated with suppression of cerebral electrical activity during the first 48 h after birth (9).…”

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“…EEG has been studied in relation to age, hypotension, hypo and hypercapnia, and cardiac output in preterm babies born before 30 wk gestation during the first 72 h after birth (8)(9)(10)(11). Lower levels of blood carbon dioxide have been associated with slowing of cerebral electrical activity and increased cerebral fractional oxygen extraction, while hypercapnia was associated with suppression of cerebral electrical activity during the first 48 h after birth (9). However, the incidence of hypercapnia, permissive or otherwise is more common (42.6%) after 7 d of age than during the first 48 h after birth (2).…”

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Effect of permissive hypercapnia on background cerebral electrical activity in premature babies

et al. 2014

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ArticlesClinical Investigation nature publishing group background: Permissive hypercapnia is routinely practiced in neonatal intensive care units. The effect of permissive hypercapnia on the preterm brain and brain electrical activity is unknown. In this study, we aimed to determine the effect of chronic changes in partial pressure of blood carbon dioxide (PcO 2 ) on brain electrical activity in preterm newborn babies born at or before 32 wk gestation. Methods: Eighty-three 1-h long digital electroencephalography (EEG) recordings were performed once a week for 4 wk on 25 babies with median gestational age of 29 wk (range: 23-32) after 48 h of age. Capillary blood gas measurements were performed midway through EEG recordings. results: There are associations between EEG parameters and blood pH, PcO 2 , and blood glucose concentration. However, there are also strong and complex associations with gestational age and substantial individual patient effects that make it difficult to demonstrate predictive associations. PcO 2 and bicarbonate are significantly correlated with relative power of θ EEG band and Δ EEG band respectively after adjustment for age and intrababy correlations, but after allowing for multiple testing these relationships are of borderline statistical significance. conclusion: Compensated respiratory acidosis may affect EEG by increased delta wave activity in preterm babies born before 32 wk gestation.

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Effect of carbon dioxide on background cerebral electrical activity and fractional oxygen extraction in very low birth weight infants just after birth

Cited by 63 publications

References 45 publications

The Relationship between Cardiac Output, Cerebral Electrical Activity, Cerebral Fractional Oxygen Extraction and Peripheral Blood Flow in Premature Newborn Infants

The Relationship between Cardiac Output, Cerebral Electrical Activity, Cerebral Fractional Oxygen Extraction and Peripheral Blood Flow in Premature Newborn Infants

Fetal Hypercapnia and Cerebral Tissue Oxygenation: Studies in Near-Term Sheep

Effect of permissive hypercapnia on background cerebral electrical activity in premature babies

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