Published online May 1, 2007
PEDIATRICS Vol. 119 No. 5 May 2007, pp. 1039-1040 (doi:10.1542/peds.2007-0634)

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LETTER TO THE EDITOR

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.

REFERENCES

1. Fabres J, Carlo WA, Phillips V, Howard G, Ambalavanan N. 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. Pediatrics. 2007;119 :299 –305[Abstract/Free Full Text]
2. Kaiser JR, Gauss CH, Williams DK. The effects of hypercapnia on cerebral autoregulation in ventilated very low birth weight infants. Pediatr Res. 2005;58 :931 –935[CrossRef][Web of Science][Medline]
3. Okumura A, Hayakawa F, Kato T, et al. Hypocarbia in preterm infants with periventricular leukomalacia: the relation between hypocarbia and mechanical ventilation. Pediatrics. 2001;107 :469 –475[Abstract/Free Full Text]
4. Wiswell TE, Graziani LJ, Kornhauser MS, et al. Effects of hypocarbia on the development of cystic periventricular leukomalacia in premature infants treated with high-frequency jet ventilation. Pediatrics. 1996;98 :918 –924[Abstract/Free Full Text]
5. Victor S, Appleton RE, Beirne M, Marson AG, Weindling AM. Effect of carbon dioxide on background cerebral electrical activity and fractional oxygen extraction in very low birth weight infants just after birth. Pediatr Res. 2005;58 :579 –585[CrossRef][Web of Science][Medline]

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PEDIATRICS (ISSN 1098-4275). ©2007 by the American Academy of Pediatrics

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This Article Extract Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services E-mail this article to a friend Similar articles in this journal Alert me to new issues of the journal Add to My File Cabinet Download to citation manager Request Permissions Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Ambalavanan, N. Search for Related Content PubMed Articles by Ambalavanan, N. Related Collections Premature & Newborn Social Bookmarking                         What's this?