750 mg per day of acetazolamide in the prevention of acute mountain sickness (AMS), as recommended in the meta-analysis published in 2000 in the British Medical Journal, may be excessive and is controversial. To determine if the efficacy of low-dose acetazolamide 125 mg bd (250 mg), as currently used in the Himalayas, is significantly different from 375 mg bd (750 mg) of acetazolamide in the prevention of AMS, we designed a prospective, double-blind, randomized, placebo-controlled trial. The participants were sampled from a diverse population of (non-Nepali) trekkers at Namche Bazaar (3440 m) in Nepal on the Everest trekking route as they ascended to study midpoints (4280 m/4358 m) and the endpoint, Lobuje (4928 m), where data were collected. Participants were randomly assigned to receive 375 mg bd of acetazolamide (82 participants), 125 mg bd of acetazolamide (74 participants), or a placebo (66 participants), beginning at 3440 m for up to 6 days as they ascended to 4928 m. The results revealed that composite AMS incidence for 125 mg bd was similar to the incidence for 375 mg bd (24% vs. 21%, 95% confidence interval, -12.6%, 19.8%), in contrast to significantly greater AMS (51%) observed in the placebo group (95% confidence interval for differences: 8%, 46%; 12%, 49% for low and high comparisons, respectively). Both doses of acetazolamide improved oxygenation equally (82.9% for 250 mg daily and 82.8% for 750 mg daily), while placebo endpoint oxygen saturation was significantly less at 80.7% (95% confidence interval for differences: 0.5%, 3.9% and 0.4%, 3.7% for low and high comparisons, respectively). There was also more paresthesia in the 375-mg bd group (p < 0.02). We conclude that 125 mg bd of acetazolamide is not significantly different from 375 mg bd in the prevention of AMS; 125 mg bd should be considered the preferred dosage when indicated for persons ascending to altitudes above 2500 m.
Introduction
The goal of the current study was to characterize the rate and estimate associated mortality and morbidity of exertional heat stroke (EHS) in U.S. military service members.
Materials and Methods
The current study was a retrospective cohort medical chart review study of all active-duty U.S. military service members, hospitalized with EHS at any MTF in the world between January1, 2007 and July 1, 2014. Enrolled patients were identified by altered mental status and elevated temperatures associated with physical exercise.
Results
Out of 607 service members with an International Classification of Disease code indicating any type of heat injury, 48 service members met inclusion criteria for EHS. Core temperature was M = 105.8°F (41°C), standard deviation = 1.43, 90% were diagnosed with EHS prior to hospitalization, and 71% received prehospital cooling. Meantime to normothermia post-hospitalization was 56 minutes (standard deviation = 79.28). Acute kidney injury was diagnosed in 40% of patients although none developed hyperkalemia or required dialysis. Disseminated intravascular coagulation was rare (4%, n = 2) and overall observed mortality was very low (2%, n = 1).
Conclusion
EHS is aggressively identified and treated in U.S. Military Treatment Facilities. Mortality and morbidity were strikingly low.
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