Rapid (0.5°C/min) minimally invasive induction of hypothermia using cold perfluorochemical lung lavage in dogs

Objective: Demonstrate minimally invasive rapid body core and brain cooling in a large animal model. Design: Prospective controlled animal trial. Setting: Private research laboratory. Subjects: Adult dogs, anesthetized, mechanically ventilated. Interventions: Cyclic lung lavage with FC-75 perfluorochemical (PFC) was administered through a dual-lumen endotracheal system in the new technique of ‘gas/liquid ventilation’ (GLV). In Trial-I, lavage volume (V-lav) was 19 ml/kg, infused and withdrawn over a cycle period (tc) of 37 s. (effective lavage rate V'-lav=31 ml/kg/min.) Five dogs received cold (∼4 °C) PFC; two controls received isothermic PFC. In Trial-II, five dogs received GLV at V-lav=8.8 ml/kg, tc=16 s, V'-lav=36 ml/kg/min. Measurements and main results: Trial-I tympanic temperature change was −3.7±0.6 °C (SD) at 7.5 min, reaching −7.3±0.6 °C at 18 min. Heat transfer efficiency was 60%. In Trial-II, efficiency fell to 40%, but heat-exchange dead space (VDtherm) remained constant. Lung/blood thermal equilibration half-time was 18 ml/kg. GLV cooling power appears more limited by PFC flows than lavage residence times. Concurrent gas ventilation may mitigate heat-diffusion limitations in liquid breathing, perhaps via bubble-induced turbulence. Objectivo: Demonstrar a redução rápida da temperatura central e cerebral num modelo de animal de grande porte com um método minimamente invasivo. Desenho: estudo controlado e prospectivo em animais. Contexto: laboratório de pesquisas privado. Sujeitos: Cães ventilados mecanicamente e anestesiados. Intervenção: lavagem cı́clica dos pulmões com FC-75 penfluorado (PFC) através de um tubo traqueal de duplo lumen, recorrendo à nova técnica de ventilação gás/lı́quido (GLV). No ensaio I, o volume da lavagem (V-lav.) foi de 19 ml/kg, introduzido recuperado em perı́odos cı́clicos de 37 s. Taxa de lavagem efectiva V-lav.=31 ml/kg/min. A cinco dos quais foi feita PFC a cerca de 4 °C. Dois grupos de controlo receberam PFC isotérmico. No ensaio II cinco dos cães receberam GLV a V-lav.=8.8 ml/kg, tc=16s, V’-lav.=36 ml/kg por minuto. Medições e result