Abstract
The aim of this study was to find out whether the intracerebral concentration of cytochrome aa3 ([CytO2]) (the terminal enzyme of the respiratory electron transport chain) altered in response to changes in arterial carbon dioxide tension (PaCO2).
Six infants bom at 23-36 (median 28) weeks of gestation and aged 1-6 (2) days were studied by near infrared spectroscopy as previously described1. The infants were mechanically ventilated and had no clinical or ultrasonographic evidence of cerebral injury. PaCO2 was altered by 0.8-1.3 (1.1) kPa within the range 4.3-9.6 kPa by changes in ventilator rate, and the effect on total cerebral haemoglobin concentration ([tHb]) and [CytO2] observed. In all infants these variables were positively related: The change in [CytO2] with changes in PaCO2 ranged from 0.10 to 0.40 (0.25) μmol.1−.kPa−. The ratio Δ(CytO2]/Δ[tHb] ranged from 0.063 to 0.119 (0.083). There was no positive relation between changes in [CytO2] and arterial oxygen saturation (SaO2), which ranged from 88 to 98%.
We conclude that [CytO2] was directly related to PaCO2, probably through changes in cerebral perfusion. However [CytO2] did not appear to be related to SaO2 in the range studied.
1. JS Wyatt et al. Arch Dis Child 1989;64:953-967
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Edwards, A., Wyatt, J., McCormick, D. et al. 82 Relation between arterial carbon dioxide tension and cerebral oxidised cytochrome aa3, concentration in preterm infants. Pediatr Res 28, 290 (1990). https://doi.org/10.1203/00006450-199009000-00106
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DOI: https://doi.org/10.1203/00006450-199009000-00106
