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.

Preliminary experience with point-of-care EEG in post-cardiac arrest patients.

OBJECTIVE: Abnormal electroencephalography (EEG) patterns are common after resuscitation from cardiac arrest and have clinical and prognostic importance. Bedside continuous EEGs are not available in many institutions. We tested the feasibility of using a point-of-care system for EEG acquisition. METHODS: We prospectively enrolled a convenience sample of post-cardiac arrest patients between 9/2015-1/2017. Upon hospital arrival, a limited EEG montage was applied. We tested both continuous EEG (cEEG) and this point-of-care EEG (eEEG). A board-certified epileptologist and a board-certified neurointensivist jointly reviewed all EEGs. Cohen's kappa coefficient evaluated agreement between eEEG and cEEG and Fisher's exact test evaluated their associations with survival to hospital discharge and proximate cause of death. RESULTS: We studied 95 comatose post-cardiac arrest patients. Mean age was 59 (SD17) years. Most (61%) were male, few (N = 22; 23%) demonstrated shockable rhythms, and PCAC IV illness severity was present in 58 (61%). eEEG was interpretable in 57 (60%) subjects. The most common eEEG interpretations were: continuous (21%), generalized suppression (14%), burst-suppression (12%) and burst-suppression with identical bursts (10%). Seizures were detected in 2 eEEG subjects (2%). No patient with seizure or burst-suppression with identical bursts survived. cEEG demonstrated generalized suppression (31%), burst-suppression with identical bursts (27%), continuous (18%) and seizure (4%). The eEEG and cEEG demonstrated fair agreement (kappa = 0.27). Neither eEEG nor cEEG was associated with survival (p = 0.19; p = 0.11) or proximate cause of death (p = 0.14; p = 0.8) CONCLUSIONS: eEEG is feasible, although artifact often precludes interpretation. eEEG is fairly associated with cEEG and may facilitate post-cardiac arrest care.