Cooling to Facilitate Metabolic Suppression in Healthy Individuals
BACKGROUND: Carbon dioxide (CO2) toxicity could be catastrophic for astronauts. Suppressing metabolism by lowering body temperature decreases CO2 production and may facilitate rescue in the event of a crippled ship. Lowering body temperature requires shivering
suppression. We evaluated dexmedetomidine to facilitate cooling of healthy individuals.
METHODS: Following consent, we administered a 1 mcg · kg−1 bolus of dexmedetomidine followed by continuous infusion (0.5–1.4 mcg · kg−1 · h−1) for 3 h of cooling. We cooled subjects using a bolus of 30 cc · kg−1 of 4°C saline followed by surface cooling. We measured vital signs, thermal and comfort scales, sedation, and shivering for 3 h and during recovery. ANOVA evaluated changes in measures over time.
RESULTS: Nine subjects completed the study. Mean age was 31 (SD 8) yr, mean mass was 71 (SD 14) kg, height of 168 (SD 9) cm, and body mass index of 25 (SD 3). Median time to 1°C drop in core temperature was 16 (IQR 15, 32) min. Temperature changed over time with median lowest temperature being 33.1°C (IQR 32.8°C, 34.1°C). Neither heart rate nor diastolic blood pressures changed over time. Systolic blood pressure decreased over time. Subjects responded to verbal stimuli and completed tasks throughout the protocol. During cooling and maintenance, subjects reported discomfort and the sensation of being cold.
CONCLUSION: Dexmedetomidine facilitates shivering suppression during prolonged cooling in healthy individuals. Subjects are easily roused, have mild decreases in systolic blood pressure, and note sensations of discomfort and cold. Cooling to suppress metabolism is a feasible countermeasure to prolong astronaut endurance.
Rittenberger JC, Flickinger KL, Weissman A, Repine M, Elmer J, Guyette FX, Callaway CW. Cooling to facilitate metabolic suppression in healthy individuals. Aerosp Med Hum Perform. 2019; 90(5):475–479.
METHODS: Following consent, we administered a 1 mcg · kg−1 bolus of dexmedetomidine followed by continuous infusion (0.5–1.4 mcg · kg−1 · h−1) for 3 h of cooling. We cooled subjects using a bolus of 30 cc · kg−1 of 4°C saline followed by surface cooling. We measured vital signs, thermal and comfort scales, sedation, and shivering for 3 h and during recovery. ANOVA evaluated changes in measures over time.
RESULTS: Nine subjects completed the study. Mean age was 31 (SD 8) yr, mean mass was 71 (SD 14) kg, height of 168 (SD 9) cm, and body mass index of 25 (SD 3). Median time to 1°C drop in core temperature was 16 (IQR 15, 32) min. Temperature changed over time with median lowest temperature being 33.1°C (IQR 32.8°C, 34.1°C). Neither heart rate nor diastolic blood pressures changed over time. Systolic blood pressure decreased over time. Subjects responded to verbal stimuli and completed tasks throughout the protocol. During cooling and maintenance, subjects reported discomfort and the sensation of being cold.
CONCLUSION: Dexmedetomidine facilitates shivering suppression during prolonged cooling in healthy individuals. Subjects are easily roused, have mild decreases in systolic blood pressure, and note sensations of discomfort and cold. Cooling to suppress metabolism is a feasible countermeasure to prolong astronaut endurance.
Rittenberger JC, Flickinger KL, Weissman A, Repine M, Elmer J, Guyette FX, Callaway CW. Cooling to facilitate metabolic suppression in healthy individuals. Aerosp Med Hum Perform. 2019; 90(5):475–479.
Keywords: cognition; dexmedetomidine; hypothermia; metabolism
Document Type: Short Communication
Publication date: 01 May 2019
- This journal (formerly Aviation, Space, and Environmental Medicine), representing the members of the Aerospace Medical Association, is published monthly for those interested in aerospace medicine and human performance. It is devoted to serving and supporting all who explore, travel, work, or live in hazardous environments ranging from beneath the sea to the outermost reaches of space. The original scientific articles in this journal provide the latest available information on investigations into such areas as changes in ambient pressure, motion sickness, increased or decreased gravitational forces, thermal stresses, vision, fatigue, circadian rhythms, psychological stress, artificial environments, predictors of success, health maintenance, human factors engineering, clinical care, and others. This journal also publishes notes on scientific news and technical items of interest to the general reader, and provides teaching material and reviews for health care professionals.
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