HYPOXANTHINE, XANTHINE, AND URIC-ACID IN NEWBORN PIGS DURING HYPOXEMIA FOLLOWED BY RESUSCITATION WITH ROOM AIR OR 100-PERCENT OXYGEN

Objective. To determine if resuscitation with room air is as effective as resuscitation with an FIO2 of 1.0. Design: Prospective, randomized laboratory study. Setting. Experimental laboratory (neonatal or deliv ery ward). Subjects: Twenty piglets, 1 to 2 wks of age. Interventions: Piglets were randomized into two groups. Both groups underwent hypoxe mia 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). Measurements and Mai n Results: 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 concentrat ions 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 re oxygenation, hypoxanthine concentrations increased both in cerebrospin al fluid and in the vitreous humor. Final concentrations in these two fluid areas were 81.8 and 39.4 mumol/L, respectively (p < .02). Xanthi ne concentrations increased similarly. In plasma, hypoxanthine and xan thine concentrations decreased during reoxygenation. The final mean co ncentration of hypoxanthine was 76.8 mumol/L (p < .02). No change in p lasma or cerebrospinal fluid uric acid concentrations were found durin g reoxygenation. The other measurements varied throughout the experime nt, but no differences were found between the groups. Conclusions: The re were no significant differences between the two treatment groups at any stage in the experiments. In this porcine model of hypoxemia, res uscitation 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.