Effects of inspired hypoxic and hypercapnic gas mixtures on cerebral oxygen saturation in neonates with univentricular heart defects.

BACKGROUND: Neonates with functional single ventricle often require hypoxic or hypercapnic inspired gas mixtures to reduce pulmonary overcirculation and improve systemic perfusion. Although the impact of these treatments on arterial oxygen saturation has been described, the effects on cerebral oxygenation remain uncertain. This study examined the effect of these treatments on cerebral oxygen saturation and systemic hemodynamics.

METHODS: Neonates with single ventricle mechanically ventilated with room air were enrolled in a randomized crossover trial of 17% inspired oxygen or 3% inspired carbon dioxide. Each treatment lasted 10 min, followed by a 10-20-min washout period. Cerebral and arterial oxygen saturation were measured by cerebral and pulse oximetry, respectively. Cerebral oxygen saturation, arterial oxygen saturation, and other physiologic data were continuously recorded.

RESULTS: Three percent inspired carbon dioxide increased cerebral oxygen saturation (56 +/- 13 to 68 +/- 13%; P < 0.01), whereas 17% inspired oxygen had no effect (53 +/- 13 to 53 +/- 14%; P = 0.8). Three percent inspired carbon dioxide increased the mean arterial pressure (45 +/- 8 to 50 +/- 9 mmHg; P < 0.01), whereas 17% inspired oxygen had no effect. And 3% inspired carbon dioxide decreased arterial pH and increased arterial carbon dioxide and oxygen tensions.

CONCLUSIONS: Inspired 3% carbon dioxide improved cerebral oxygenation and mean arterial pressure. Treatment with 17% inspired oxygen had no effect on either.