Background and Goal of Study: Therapeutic hypothermia (TH) for 72h is a recognised treatment for neonatal encephalopathy (NE). Xenon (Xe) is a promising adjunct neuroprotectant to TH. Delayed initiation (~10h of life) of 30% xenon with TH did not alter early MRI biomarkers of later adverse neurodevelopment. However, inhaled Xe for the entire 72h TH period may enhance brain protection. Xe costs $30/L but tissue uptake is slow, favouring a closed circuit with automated gas mixture control. To eliminate costly leaks from a controller supplied with pressurised Xe we developed an ambient pressure fresh gas addition system. We investigated the feasibility of using this to economically administer Xe with or without TH for 72h. Materials and Methods: Five newborn pigs were anaesthetised and ventilated via a cuffed tracheal tube, with (N=4) or without (N=1) a global hypoxic-ischaemic insult, then randomised to receive 50% inhaled Xe under hypothermia (Trectal 35°C, N=3) or normothermia (Trectal 38.5°C, N=2) for 72h with background propofol and fentanyl. A microcontroller acquired xenon / oxygen concentrations from sensors in a single-use closed circuit neonatal breathingsystem (Fig 1).  Into this circuit it injected 18ml boluses of oxygen, air or xenon from ambient pressure reservoir bags, to achieve set target concentrations. We report Xe consumption and concentration during this period. [Fig 1. Automated gas controller & breathing system] Results and Discussion: Mean (SD) hourly Xe consumption was 0.28 L/h (0.1) (Fig 2A), mean (SD) hourly Xe concentration was 49.6% (1.64) (Fig 2B). Median (IQR) % difference in achieving target Xe concentration was 4.2% (2.9, 7.8). [Fig 2. Xenon consumption and concentration vs time] Conclusion(s): The automated controller functioned as intended maintaining an inhaled Xe concentration close to the 50% target for 72h at a xenon gas cost of $8.4/h.
|Publication status||Published - Jun 2017|