We read with interest the paper by Naeye and Shaffer.1 The authors conclude among other things, that commonly obtained hematological values such as blood lymphocyte, normoblast and platelet counts can identify when brain damage began and the rate at which it advanced.
We have several concerns about the hematological data presented and the authors’ interpretations.
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1
Selection bias: The medical records of 608 full-term neonates with cerebral palsy of possible antenatal hypoxemic-ischemic origin were collected nation-wide. No subset of data is identified from a single institution or referral area. After excluding infants with nonhypoxemic-ischemic causes of brain damage, and including only those infants who had prolonged bradycardia documented by electronic fetal heart rate recordings, 92 subjects remained for study. Complete laboratory results were available for 58 of the 92 cases. Additional selection biases of this study were created by exclusion of asphyxial neonatal deaths and of cases of neonatal hypoxic-ischemic encephalopathy that survived without cerebral palsy.
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2
Duration of bradycardia: In modern obstetrics bradycardia is rarely ignored for more then few minutes. Prolonged bradycardia of more then 15 min is rare and represents questionable obstetrical care. We are also surprised that bradycardia lasting more than 60 min was compatible with fetal survival, and that stillbirths delivered after 60 min of bradycardia were successfully resuscitated.
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3
Use of the term ‘injury’: The authors address timing in relation to ‘asphyxial brain injury’ or ‘damage’, and not to asphyxial insult. The inference is that it is the brain injury that caused the observed changes in blood cell counts and multi-organ function, not the asphyxial insult. Given that the authors did not report data of infants who had intrapartum asphyxia without permanent brain injury, it is not clear how they made the leap from insult to injury.
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4
Presentation of blood cell counts: Multiple lymphocyte counts were reported to have been available for 58 infants; the numbers of infants with normoblast and platelet counts are not reported. Graphic representation of serial lymphocyte counts of the individual infants who ‘usually’ had ‘more than three in the first 5 h after birth’ could perhaps provide more insight into lymphocytic changes after asphyxia than the aggregated data presented in Figure 1.1
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