Dexmedetomidine-Induced Torpor: A Potential Solution To Life Support Limitations In Space

Space shuttle payloads limit long-duration space travel due to the extensive closed-loop life support systems. Completing extended space missions requires greater fuel or sophisticated propulsion systems capable of accommodating weightier payloads. Artificial metabolic suppression (torpor) could reduce CO2 production, easing the burden on life support and propulsion systems. PURPOSE: To determine the degree of hypothermia and metabolic suppression induced by dexmedetomidine in cold and thermoneutral conditions. METHODS: Six healthy subjects (30 ± 7 y, mass: 76.2 ± 23.8 kg, BMI: 25 ± 6) were sedated with dexmedetomidine in thermoneutral (TN, 31.1 ± 0.3 °C) and cold (C, 19.8 ± 0.3 °C) environments for three hours. Heart rate (HR), core temperature (Tc), end-tidal CO2 (EtCO2), arterial oxygen saturation (SpO2), and blood pressure were measured throughout each condition, and mean arterial pressure (MAP) was calculated. Relative oxygen consumption (VO2), carbon dioxide production (VCO2), and resting metabolic rate (RMR) were measured 30 minutes immediately before each exposure and from 30-60, 90-120, and 150-180 min. RESULTS: HR (57 ± 10) and Tc (36.4 ± 0.5 °C) were lower in C than in TN (HR: 67 ± 11, p < 0.001, after 70 min.; Tc 36.9 ± 0.2 °C, p < .005 after 30 min.). VO2 (α = 0.9 ± 0.4 mL/kg/min-1), VCO2 (α = 56.9 ± 19.2 mL/min-1), and RMR (α = 487.9 ± 177.8 Kcal/D) decreased between baseline and 150-180 min in C (all p < 0.001) but not in TN. Mean EtCO2 was less in C (36 ± 3.2) than TN (38 ± 3.6) (p = 0.01). MAP and SpO2 were not different between conditions or from baseline. No other differences were observed between conditions or between conditions and baseline measurements. CONCLUSION: Dexmedetomidine-induced torpor will suppress metabolic functions and lower CO2 production in a cold environment compared to a thermoneutral one. Torpor could be a viable method to reduce the life support requirements for astronauts during extended space missions. The stability of MAP and SpO2, regardless of environmental conditions, suggests a safe profile for regulating metabolic rates in controlled settings. Human Torpor Fund, Inc