Published online May 1, 2007
PEDIATRICS
Vol. 119
No. 5
May 2007, pp.
1039-1040
(doi:10.1542/peds.2007-0634)
Both Extremes of Arterial Carbon Dioxide Pressure and the Magnitude of Fluctuations in Arterial Carbon Dioxide Pressure Are Associated With Severe Intraventricular Hemorrhage in Preterm Infants: In Reply
Namasivayam Ambalavanan, MD
Departments of Pediatrics
University of Alabama at Birmingham
Birmingham, AL 35249
We thank Dr Kaiser for his comments on our article.1 His comments focus on the association of hypercapnia with severe (grade III and IV) intraventricular hemorrhage (IVH), and his demonstration that increasing PaCO2 is associated with impaired cerebral autoregulation in premature infants2 suggests a possible mechanism for the IVH resulting from extreme hypercapnia. However, there were no significant differences in PaCO2 in infants with mild (grade I or II) IVH compared with infants with no IVH, which suggests that abnormal levels of PaCO2 are more likely to be associated with extension of preexisting hemorrhage rather than initiation or development of IVH.1 Dr Kaiser's comments also focus only on part of our findings. Our study also demonstrated an association of severe IVH with hypocapnia and fluctuations of PaCO2.1 Previous studies have primarily demonstrated an association between periventricular leukomalacia and hypocapnia,3,4 which may be caused by decreased cerebral blood flow and increased cerebral fractional oxygen extraction induced by the hypocapnia.5 As mentioned in our discussion, the mechanisms that underlie the association of severe IVH with hypocapnia and marked fluctuations in PaCO2 need to be determined in future studies, although decreases in cerebral blood flow induced by hypocapnia and ischemia-reperfusion resulting from marked fluctuations in PaCO2 may possibly be involved. Alternatively, hypercapnia, hypocapnia, and the fluctuations in PaCO2 could be effects, rather than the causes, of severe IVH, by either fluctuations in respiratory drive or changes in carbon dioxide production caused by intracranial pathology.
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PEDIATRICS (ISSN 1098-4275). ©2007 by the American Academy of Pediatrics
