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Title: Effect of hematocrit and systolic blood pressure on cerebral blood flow in newborn infants

Abstract

The effects of hematocrit and systolic blood pressure on cerebral blood flow were measured in 15 stable, low birth weight babies. CBF was measured with a modification of the xenon-133 (/sup 133/Xe) clearance technique, which uses an intravenous bolus of /sup 133/Xe, an external chest detector to estimate arterial /sup 133/Xe concentration, eight external cranial detectors to measure cephalic /sup 133/Xe clearance curves, and a two-compartmental analysis of the cephalic /sup 133/Xe clearance curves to estimate CBF. There was a significant inverse correlation between hematocrit and CBF, presumably due to alterations in arterial oxygen content and blood viscosity. Newborn CBF varied independently of systolic blood pressure between 60 and 84 mm Hg, suggesting an intact cerebrovascular autoregulatory mechanism. These results indicate that at least two of the factors that affect newborn animal CBF are operational in human newborns and may have important clinical implications.

Authors:
; ; ; ;
Publication Date:
Research Org.:
Univ. of Pennsylvania, Philadelphia
OSTI Identifier:
6468181
Resource Type:
Journal Article
Resource Relation:
Journal Name: J. Cereb. Blood Flow Metab.; (United States); Journal Volume: 3
Country of Publication:
United States
Language:
English
Subject:
59 BASIC BIOLOGICAL SCIENCES; BRAIN; BLOOD FLOW; BLOOD COUNT; BLOOD PRESSURE; CLEARANCE; DYNAMIC FUNCTION STUDIES; HOMEOSTASIS; INFANTS; TRACER TECHNIQUES; XENON 133; AGE GROUPS; BETA DECAY RADIOISOTOPES; BETA-MINUS DECAY RADIOISOTOPES; BODY; CENTRAL NERVOUS SYSTEM; CHILDREN; DAYS LIVING RADIOISOTOPES; EVEN-ODD NUCLEI; INTERMEDIATE MASS NUCLEI; INTERNAL CONVERSION RADIOISOTOPES; ISOMERIC TRANSITION ISOTOPES; ISOTOPE APPLICATIONS; ISOTOPES; NERVOUS SYSTEM; NUCLEI; ORGANS; RADIOISOTOPES; XENON ISOTOPES; 551001* - Physiological Systems- Tracer Techniques

Citation Formats

Younkin, D.P., Reivich, M., Jaggi, J.L., Obrist, W.D., and Delivoria-Papadopoulos, M. Effect of hematocrit and systolic blood pressure on cerebral blood flow in newborn infants. United States: N. p., 1987. Web. doi:10.1038/jcbfm.1987.66.
Younkin, D.P., Reivich, M., Jaggi, J.L., Obrist, W.D., & Delivoria-Papadopoulos, M. Effect of hematocrit and systolic blood pressure on cerebral blood flow in newborn infants. United States. doi:10.1038/jcbfm.1987.66.
Younkin, D.P., Reivich, M., Jaggi, J.L., Obrist, W.D., and Delivoria-Papadopoulos, M. Mon . "Effect of hematocrit and systolic blood pressure on cerebral blood flow in newborn infants". United States. doi:10.1038/jcbfm.1987.66.
@article{osti_6468181,
title = {Effect of hematocrit and systolic blood pressure on cerebral blood flow in newborn infants},
author = {Younkin, D.P. and Reivich, M. and Jaggi, J.L. and Obrist, W.D. and Delivoria-Papadopoulos, M.},
abstractNote = {The effects of hematocrit and systolic blood pressure on cerebral blood flow were measured in 15 stable, low birth weight babies. CBF was measured with a modification of the xenon-133 (/sup 133/Xe) clearance technique, which uses an intravenous bolus of /sup 133/Xe, an external chest detector to estimate arterial /sup 133/Xe concentration, eight external cranial detectors to measure cephalic /sup 133/Xe clearance curves, and a two-compartmental analysis of the cephalic /sup 133/Xe clearance curves to estimate CBF. There was a significant inverse correlation between hematocrit and CBF, presumably due to alterations in arterial oxygen content and blood viscosity. Newborn CBF varied independently of systolic blood pressure between 60 and 84 mm Hg, suggesting an intact cerebrovascular autoregulatory mechanism. These results indicate that at least two of the factors that affect newborn animal CBF are operational in human newborns and may have important clinical implications.},
doi = {10.1038/jcbfm.1987.66},
journal = {J. Cereb. Blood Flow Metab.; (United States)},
number = ,
volume = 3,
place = {United States},
year = {Mon Jun 01 00:00:00 EDT 1987},
month = {Mon Jun 01 00:00:00 EDT 1987}
}
  • The authors have shown that the fall in cerebral blood flow (CBF) as hematocrit (Hct) rises is due to the independent effects of increasing red blood cell (RBC) concentration and arterial O{sub 2} content (Ca{sub O{sub 2}}). In the present study, they tested the hypothesis that the magnitude of the effect of RBC concentration depends on the base-line cerebral fractional oxygen extraction (E). Pentobarbital-anesthetized 1- to 7-day-old sheep were first exchange transfused with plasma to lower Hct to 20%. Base-line E was set to either high or low levels by induction of hypocarbia, or hypercarbia. A second isovolemic exchange transfusionmore » with pure methemoglobin-containing adult sheep red cells then raised Hct with no significant increase in Ca{sub O{sub 2}}. Pa{sub CO{sub 2}} was maintained and other variables with potential effect on CBF did not change. CBF corrected for any individual alteration in CMRo{sub 2}. This study supports the hypothesis that the magnitude of the decline in CBF secondary to an increase in RBC concentration depends on the initial E. The effect of RBC concentration on CBF is greatest when E is low.« less
  • The authors examined effects of hypothermia on cerebral metabolic rate and cerebral blood flow in anesthetized, newborn pigs (1-4 days old). Cerebral blood flow (CBF) was determined with 15-{mu}m radioactive microspheres. Regional CBF ranged from 44 to 66 ml{center dot}min{sup {minus}1}{center dot}100 g{sup {minus}1}, and cerebral metabolic rate was 1.94 {plus minus} 0.23 ml O{sub 2}{center dot}100 g{sup {minus}1}{center dot}min{sup {minus}1} during normothermia (39{degree}C). Reduction of rectal temperature to 34-35{degree}C decreased CBF and cerebral metabolic rate 40-50%. In another group of piglets, they examined responsiveness of the cerebral circulation to arterial hypercapnia during hypothermia. Although absolute values for normocapnic andmore » hypercapnic CBF were reduced by hypothermia and absolute values for normocapnic and hypercapnic cerebrovascular resistance were increased, the percentage changes from control in these variables during hypercapnia were similar during normothermia and hypothermia. In another group of animals that were maintained normothermic and exposed to two episodes of hypercapnia, there was no attenuation of cerebrovascular dilation during the second episode. They conclude that hypothermia reduces CBF secondarily to a decrease in cerebral metabolic rate and that percent dilator responsiveness to arterial hypercapnia is unaltered when body temperature is reduced.« less
  • The tremendous growth of interest in neurologic intensive care and in the pathophysiology of the cerebral circulation in the past few years has resulted in increasing numbers of studies that document alterations in cerebral flow during the course of various diseases or as a response to treatment of them. Before pediatricians come to conclusions based on these studies, it is important to have an understanding of the techniques involved. The techniques are complex and difficult but are based on understandable principles. They also have limitations and are subject to misinterpretations. Pediatricians should become knowledgeable about some of these techniques andmore » their limitations because it is likely that they will be applied with increasing frequency in the next several years. We are on the threshold of exciting discoveries in abnormalities of cerebral blood flow and cerebral metabolism not only in critically ill children but also in children with congenital and learning disorders.« less