The effects of perfluorocarbon dosing strategy on cerebral blood flow when starting partial liquid ventilation: A randomized, controlled, experimental study

Introduction: Partial liquid ventilation may benefit the lung disease in preterm neonates but intratracheal instillation of perfluorocarbon increases cerebral blood flow and may cause brain injury. We aimed to determine if the effects of perfluorocarbon administration on cerebral blood flow vary by dose-volume, rate of administration, endotracheal tube portal of entry, or closely targeting PaCO2. Methods: Forty-two dosing events (in eleven rabbits) were randomised to different dosing strategies, including a sham (i.e., placebo/control) dose of air over 20 min, 20 mL/kg of perfluorocarbon slowly over 20 min, 10 mL/kg of perfluorocarbon slowly over 20 min, 10 mL/kg of perfluorocarbon moderately fast over 10 min, 10 mL/kg of perfluorocarbon rapidly over 5 min, 10 mL/kg of perfluorocarbon slowly over 20 min via the endotracheal tube tip lumen (as opposed to the proximal end of the tube used in all other groups), or 10 mL/kg of perfluorocarbon slowly over 20 min whilst targeting a PaCO2 of 45 50 mmHg. Blood gases, haemodynamics, cortical cerebral blood flow and carotid flow were recorded continuously for 30 minutes from the start of each dose. Results: Carotid flow increased with 20 mL/kg perfluorocarbon and cortical cerebral blood flow was significantly more variable. Carotid and cortical cerebral blood flow increased using 10 mL/kg or 20 mL/kg with no difference between the two dose-volumes. There was no difference in cerebral blood flow by rate of administration, but carotid blood flow was more variable during slow administration. There were no differences in the increase in cerebral blood flow by portal of entry. If PaCO2 was maintained between 45 50 mmHg there was no increase in cerebral blood flow and there was less variable carotid flow. Conclusions: Cerebral blood flow increases with perfluorocarbon dosing. This occurs regardless of the dose-volume of perfluorocarbon. These effects were mitigated by closely targeting PaCO2.