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Introduction: Although ultratrail races are increasing in popularity, there is a dearth of data regarding illnesses and medical care at these events. Data about injuries and illnesses for races taking place in the Himalayas, where the nearest medical facility can be hundreds of miles away, are even harder to find. This study aimed to describe the injuries and illnesses befalling the participants of a 7-stage 212 km (132 mi) trail race at high altitude., Methods: Ethical approval was obtained from Nepal Research Health Council. A retrospective study of the record of medical encounters among the 100 participants competing in the Manaslu trail race in Nepal from 2014 to 2016 was performed. Diagnoses were classified into various categories. Informed consent was taken from all participants., Results: Acute diarrhea was the most common ailment reported among the participants (18%), followed closely by musculoskeletal problems (17%). Altitude illness made up 6% of care provided. Approximately 35% of the athletes were using acetazolamide as prophylaxis for high altitude illnesses. The 1 case needing evacuation in the 3 iterations was high altitude pulmonary edema., Conclusions: Ultratrail races at high altitude pose a challenge in terms of provision of medical care in a remote setting with limited resources. However, most of the illnesses are minor in nature and easily managed by the race doctor. Knowledge of common illnesses among travelers to the area can help aid in preparation and provision of proper care, especially in remote settings with limited resources., (Copyright © 2020 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.)

Introduction: North American guidelines propose 125 mg acetazolamide twice daily as the recommended prophylactic dose to prevent acute mountain sickness (AMS). To our knowledge, a dose lower than 125 mg twice daily has not been studied., Methods: We conducted a prospective, double-blind, randomized, noninferiority trial of trekkers to Everest Base Camp in Nepal. Participants received the reduced dose of 62.5 mg twice daily or the standard dose of 125 mg twice daily. Primary outcome was incidence of AMS, and secondary outcomes were severity of AMS and side effects in each group., Results: Seventy-three participants had sufficient data to be included in the analysis. Overall incidence of AMS was 21 of 38 (55.3%) in reduced-dose and 21 of 35 (60.0%) in standard-dose recipients. The daily incidence rate of AMS was 6.7% (95% CI 2.5-10.9) for each individual in the reduced-dose group and 8.9% (95% CI 4.5-13.3) in the standard-dose group. Overall severity of participants' Lake Louise Score was 1.014 in the reduced-dose group and 0.966 in the standard-dose group (95% CI 0.885-1.144). Side effects were similar between the groups., Conclusions: The reduced dose of acetazolamide at 62.5 mg twice daily was noninferior to the currently recommended dose of 125 mg twice daily for the prevention of AMS. Low incidence of AMS in the study population may have limited the ability to differentiate the treatment effects. Further research with more participants with greater rates of AMS would further elucidate this reduced dosage for preventing altitude illness., (Copyright © 2018 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.)

Lowlanders rapidly ascending to high altitude (>2500 m) often develop acute mountain sickness (AMS). While acclimatization is the most effective method of reducing symptoms of AMS (ie, headache, fatigue, nausea, gastrointestinal distress, etc.), it may take several days to become fully acclimated. Prophylactic use of acetazolamide (AZ), a carbonic anhydrase inhibitor, has become a popular alternative to staged acclimatization because it can be a less time-consuming method of reducing symptoms of AMS. While numerous studies have shown the effectiveness of AZ in mitigating the symptoms of AMS, a review of the existing literature regarding the effects of AZ on submaximal and maximal exercise performance at sea level and at altitude has not been performed. Literature search identified 17 peer reviewed articles examining the effects of AZ on exercise performance both at sea level and at altitude, as well as the associated side effects of prophylactic AZ use for the attenuation of AMS. This review finds that AZ treated cohorts experience a reduction in time to exhaustion during both submaximal and maximal exercise performance at sea level. At altitude, AZ treated cohorts' recorded widely variable submaximal and maximal exercise performance. At sea level, AZ impairs submaximal and maximal exercise performance. Due to the wide variation of findings of previously published studies, the effects of AZ on submaximal and maximal exercise performance at altitude remain unknown., (Copyright © 2018 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.)

Objective: This study aimed to compare 3 treatment modalities during sleep at an altitude of 5300 m to identify strategies for reducing the incidence of periodic breathing at high altitude., Methods: Fifteen trekkers, with identical ascent profiles and no signs or symptoms of altitude illness, served as subjects. All study participants arrived at 5300 m after a gradual ascent from 1300 m. On their second night at 5300 m, subjects were randomly assigned (with a computer-based random assignment procedure) to 1 of 4 different treatment groups: control (n = 4); 1 L/min O(2) via a demand system during sleep (n = 3); 1 L/min O(2)/CO(2) mix (1.5% CO(2)) via a demand system during sleep (n = 4); or 125 mg acetazolamide 30 minutes before bedtime (n = 4). Heart rate, respiration rate, blood oxygen saturation, tidal volume, minute volume, and apnea hypopnea index were measured., Results: Upon comparing the 4 groups, there were no statistically significant differences between the variables. One-way analysis of variance indicated a trend toward statistical significance for SaO(2) between groups (F = 2.9, P = .08), and Tukey Honestly Significant Difference (HSD) post hoc tests indicated a trend in the SaO(2) difference between the 1 L/min oxygen and control groups (P = .07). While 1-way analysis of variance suggested no difference for respiratory rate between groups (F = 2.5, P = .1), Tukey HSD indicated a trend in statistical difference of the respiratory rate between 1 L/min O(2) and 1 L/min O(2)/CO(2) mixture (P = .08)., Conclusions: These statistical trends found between control and treatment groups indicate that further study is warranted., (Copyright © 2011 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.)

Objectives: Over the last 20 years a number of small trials have reported that spironolactone effectively prevents acute mountain sickness (AMS), but to date there have been no large randomized trials investigating the efficacy of spironolactone in prevention of AMS. Hence, a prospective, double-blind, randomized, placebo-controlled trial was conducted to evaluate the efficacy of spironolactone in the prevention of AMS., Methods: Participants were sampled from a diverse population of western trekkers recruited at 4300 m on the Mount Everest base camp approach (Nepal side) en route to the study endpoint at 5000 m. Three hundred and eleven healthy trekkers were enrolled, and 251 completed the trial from October to November 2007. Participants were randomly assigned to receive at least 3 doses of spironolactone 50 mg BID, acetazolamide 250 mg BID, or visually matched placebo. A Lake Louise AMS Score of 3 or more, together with the presence of headache and 1 other symptom, was used to evaluate the incidence and severity of AMS. Secondary outcome measures were blood oxygen content and the incidence and severity of high altitude headache (HAH)., Results: Acetazolamide was more effective than spironolactone in preventing AMS (OR = 0.28, 95% CI 0.12-0.60, p < 0.01). Spironolactone was not significantly different from placebo in the prevention of AMS. AMS incidence for placebo was 20.3%, acetazolamide 10.5%, and spironolactone 29.4%. Oxygen saturation was also significantly increased in the acetazolamide group (83% ± 0.04) vs spironolactone group (80% ± 0.05, p < 0.01)., Conclusions: Spironolactone (50 mg BID) was ineffective in comparison to acetazolamide (250 mg BID) in the prevention of AMS in partially acclimatized western trekkers ascending to 5000 m in the Nepali Himalaya., (Copyright © 2011 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.)

Objective: High altitude headache (HAH) is the most common neurological complaint at altitude and the defining component of acute mountain sickness (AMS). However, there is a paucity of literature concerning its prevention. Toward this end, we initiated a prospective, double-blind, randomized, placebo-controlled trial in the Nepal Himalaya designed to compare the effectiveness of ibuprofen and acetazolamide for the prevention of HAH., Methods: Three hundred forty-three healthy western trekkers were recruited at altitudes of 4280 m and 4358 m and assigned to receive ibuprofen 600 mg, acetazolamide 85 mg, or placebo 3 times daily before continued ascent to 4928 m. Outcome measures included headache incidence and severity, AMS incidence and severity on the Lake Louise AMS Questionnaire (LLQ), and visual analog scale (VAS)., Results: Two hundred sixty-five of 343 subjects completed the trial. HAH incidence was similar when treated with acetazolamide (27.1%) or ibuprofen (27.5%; P = .95), and both agents were significantly more effective than placebo (45.3%; P = .01). AMS incidence was similar when treated with acetazolamide (18.8%) or ibuprofen (13.7%; P = .34), and both agents were significantly more effective than placebo (28.6%; P = .03). In fully compliant participants, moderate or severe headache incidence was similar when treated with acetazolamide (3.8%) or ibuprofen (4.7%; P = .79), and both agents were significantly more effective than placebo (13.5%; P = .03)., Conclusions: Ibuprofen and acetazolamide were similarly effective in preventing HAH. Ibuprofen was similar to acetazolamide in preventing symptoms of AMS, an interesting finding that implies a potentially new approach to prevention of cerebral forms of acute altitude illness., (Copyright 2010 Wilderness Medical Society. Published by Elsevier Inc. All rights reserved.)

Objective: The interaction of 15 variables representing physical characteristics, previous altitude exposure, and ascent data was analyzed to determine their contribution to acute mountain sickness (AMS)., Methods: Questionnaires were obtained from 359 volunteers upon reaching the summit of Mt Whitney (4419 m). Heart rate and arterial oxygen saturation were measured with a pulse oximeter, and AMS was identified by Lake Louise Self-Assessment scoring. Multiple logistic regression analysis was used to identify significant protective and risk factors for AMS., Results: Thirty-three percent of the sample met the criteria for AMS. The odds of experiencing AMS were greater for those who reported a previous altitude illness (adjusted odds ratio [OR] = 2.00, P < .01) or who were taking analgesics during the ascent (adjusted OR = 2.09, P < .01). Odds for AMS decreased with increasing age (adjusted OR = 0.82, P < .0001), a greater number of climbs above 3000 m in the past month (adjusted OR = 0.92, P < .05), and use of acetazolamide during the ascent (adjusted OR = 0.33, P < .05)., Conclusions: The significant determinants of AMS on the summit of Mt Whitney were age, a history of altitude illness, number of climbs above 3000 m in the past month, and use of acetazolamide and analgesics during ascent.

Objective: To study the effect of medroxyprogesterone on blood gases and cerebral regional oxygenation at high altitude, alone and in conjunction with acetazolamide, and to assess the effect on acute mountain sickness (AMS)., Design: Two placebo-controlled trials during rapid ascent to high altitude., Participants: In the first trial, 20 participants, and in the second trial, 24 participants., Setting: During rapid ascent to 4680 m and on rapid ascent to 5200 m., Intervention: In the first trial, participants were randomized to receive medroxyprogesterone 30 mg or a placebo twice a day. In the second trial, participants were randomly assigned to one of 4 groups: a placebo twice daily, medroxyprogesterone 30 mg twice daily, acetazolamide 250 mg plus a placebo twice daily, or acetazolamide 250 mg plus medroxyprogesterone 30 mg twice daily., Main Outcome Measures: Blood gas changes and symptom scores of AMS in both trials and cerebral regional oxygen saturations in the first trial only., Results: Medroxyprogesterone improved peripheral oxygen saturations in both trials and improved PaO2 in combination with acetazolamide. Cerebral regional oxygen saturation was not altered by medroxyprogesterone. The reduction in symptom scores and in the extent of AMS was not significant in this limited study., Conclusions: Medroxyprogesterone acts as a respiratory stimulant, but the clinical benefit regarding the development of AMS was unproven at high altitude. Combined medroxyprogesterone and acetazolamide gave the best PaO2.