Intravenous ¹³³Xe clearance in preterm neonates with respiratory distress. Internal validation of CBF∞ as a measure of global cerebral blood flow

Abstract

An intravenous ¹³³Xe clearance technique is described, giving very low values of global cerebral blood flow (CBF∞) in mechanically ventilated, preterm infants. External monitoring of the chest is used to estimate the arterial input function to the brain, with a modified correction to allow for increased recirculation due to right-to-left shunting. The results compared well in 10 studies in seven infants, where CBF∞ could also be calculated from direct simultaneous blood sampling from the right radial artery (7.9 ml/100 g/min±2.5 SD vs. 8.4±3.6, p>0.05). In 25 studies in 12 infants the results compared well with those calculated from simultaneous ¹³³Xe concentrations in expired air. Fifteen-minute clearance data gave better precision than 8-min data. The modified chest curve correction was partly effective in a case of extreme right-to-left shunting.

Key Words:

• artificial ventilation
• tracer kinetics