Hypoxanthine, xanthine, and uric acid in newborn pigs during hypoxemia followed by resuscitation with room air or 100% oxygen

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Abstract
To determine if resuscitation with room air is as effective as resuscitation with an FIO2 of 1.0. Prospective, randomized laboratory study. Experimental laboratory (neonatal or delivery ward). Twenty piglets, 1 to 2 wks of age. Piglets were randomized into two groups. Both groups underwent hypoxemia for 2 hrs and then underwent reoxygenation for 1 hr (group 1 with an FIO2 of 1.0 and group 2 with an FIO2 of 0.21). Hypoxanthine, xanthine, uric acid, PaO2, oxygen saturation, pH, base excess or deficit, and arterial pressure. During hypoxemia (PaO2 26 to 49 torr [3.5 to 6.5 kPa]), the mean hypoxanthine concentrations increased (p < .02) from 26.1 to 115.4 mumol/L in plasma, from 20.9 to 81.7 mumol/L in cerebrospinal fluid, and from 12.9 to 21.5 mumol/L in vitreous humor. Xanthine concentrations changed in a similar way, whereas uric acid concentrations increased only in plasma. During reoxygenation, hypoxanthine concentrations increased both in cerebrospinal fluid and in the vitreous humor. Final concentrations in these two fluid areas were 81.8 and 39.4 mumol/L, respectively (p < .02). Xanthine concentrations increased similarly. In plasma, hypoxanthine and xanthine concentrations decreased during reoxygenation. The final mean concentration of hypoxanthine was 76.8 mumol/L (p < .02). No change in plasma or cerebrospinal fluid uric acid concentrations were found during reoxygenation. The other measurements varied throughout the experiment, but no differences were found between the groups. There were no significant differences between the two treatment groups at any stage in the experiments. In this porcine model of hypoxemia, resuscitation with room air was as effective as was resuscitation with an FIO2 of 1.0, when circulating concentrations of oxypurines were used as an end-point.

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