The Wilderness Medical Society convened a panel to review available evidence supporting practices for medical direction of search and rescue teams. This panel included of members of the Wilderness Medical Society Search and Rescue Committee, the National Association of EMS Physicians Wilderness Committee, and leadership of the Mountain Rescue Association. Literature about definitions and terminology, epidemiology, currently accepted best practices, and regulatory and legal considerations was reviewed. The panel graded available evidence supporting practices according to the American College of Chest Physicians criteria and then made recommendations based on that evidence. Recommendations were based on the panel's collective clinical experience and judgment when published evidence was lacking.

Introduction: The International Commission for Mountain Emergency Medicine (ICAR MedCom) developed updated recommendations for the management of avalanche victims. Methods: ICAR MedCom created Population Intervention Comparator Outcome (PICO) questions and conducted a scoping review of the literature. We evaluated and graded the evidence using the American College of Chest Physicians system.Results: We included 120 studies including original data in the qualitative synthesis. There were 45 retrospective studies (38%), 44 case reports or case series (37%), and 18 prospective studies on volunteers (15%). The main cause of death from avalanche burial was asphyxia (range of all stud-ies 65-100%). Trauma was the second most common cause of death (5-29%). Hypothermia accounted for few deaths (0-4%).Conclusions and recommendations: For a victim with a burial time < 60 minutes without signs of life, presume asphyxia and provide rescue breaths as soon as possible, regardless of airway patency. For a victim with a burial time > 60 minutes, no signs of life but a patent airway or airway with unknown patency, presume that a primary hypothermic CA has occurred and initiate cardiopulmonary resuscitation (CPR) unless temperature can be measured to rule out hypothermic cardiac arrest. For a victim buried > 60 minutes without signs of life and with an obstructed airway, if core temperature cannot be measured, rescuers can presume asphyxia-induced CA, and should not initiate CPR. If core temperature can be measured, for a victim without signs of life, with a patent airway, and with a core temperature < 30 degrees C attempt resuscitation, regardless of burial duration.

Lugnet, Viktor, Miles McDonough, Les Gordon, Mercedes Galindez, Nicolas Mena Reyes, Alison Sheets, Ken Zafren, and Peter Paal. Termination of cardiopulmonary resuscitation in mountain rescue: a scoping review and ICAR MedCom 2023 recommendations. High Alt Med Biol 00:000-000, 2023.Background: In 2012, the International Commission for Mountain Emergency Medicine (ICAR MedCom) published recommendations for termination of cardiopulmonary resuscitation (CPR) in mountain rescue. New developments have necessitated an update. This is the 2023 update for termination of CPR in mountain rescue.Methods: For this scoping review, we searched the PubMed and Cochrane libraries, updated the recommendations, and obtained consensus approval within the writing group and the ICAR MedCom.Results: We screened a total of 9,102 articles, of which 120 articles met the inclusion criteria. We developed 17 recommendations graded according to the strength of recommendation and level of evidence.Conclusions: Most of the recommendations from 2012 are still valid. We made minor changes regarding the safety of rescuers and responses to primary or traumatic cardiac arrest. The criteria for termination of CPR remain unchanged. The principal changes include updated recommendations for mechanical chest compression, point of care ultrasound (POCUS), extracorporeal life support (ECLS) for hypothermia, the effects of water temperature in drowning, and the use of burial times in avalanche rescue.

We have read the letter written by Dr. Dietrichs and Dr. Strapazzon with great interest. The suggestion of a biphasic relationship between risk of electrode-induced ventricular fibrillation (VF) and core temperature in a small number of cooled rabbit hearts (but not rats) in a laboratory setting is highly interesting. However, we would like to point out the following issues with the proposed parallelism with human electrophysiology and clarify the use of the Revised Swiss System for the field classification of primary accidental hypothermia, when no measurements of core temperature are available.1Musi M.E. Sheets A. Zafren K. et al.Clinical staging of accidental hypothermia: the revised Swiss system: recommendation of the International Commission for Mountain Emergency Medicine (ICAR MedCom).Resuscitation. 2021; 162: 182-187Abstract Full Text Full Text PDF PubMed Scopus (10) Google Scholar First, the Revised Swiss System is not a score and does not attempt to estimate a range of core temperature as suggested in Dr. Dietrich's letter. The main advantage of the Revised Swiss System is to move the field provider from estimating core temperature to estimate the patient's risk of cardiac arrest. We demonstrated the limitations of the original Swiss System, and acknowledge that the revised classification deserves a broad approach. Due to the continued unknowns of the natural history of the disease, we want to avoid inaccurate assumptions. Secondly, as discussed in the reference cited by the letter authors, cardiac electrophysiology is largely species-dependent.2Dietrichs E.S. Tveita T. Smith G. Hypothermia and cardiac electrophysiology: a systematic review of clinical and experimental data.Cardiovasc Res. 2019; 115: 501-509Crossref PubMed Scopus (17) Google Scholar While a rabbit heart resembles human cardiac electrophysiology better than other species, it is easy to imagine significant unknown differences to make direct comparisons of the myocardium of lagomorphs and homo sapiens problematic. Analyzing the history of accidental hypothermia electrophysiology research, we have already encountered that relevant animal findings do not completely correlate with human electrophysiology. For example, the hypothesis that J-waves correlate highly with ventricular fibrillation in humans, as demonstrated on hypothermic canines, has been inconsistently detected in human studies.2Dietrichs E.S. Tveita T. Smith G. Hypothermia and cardiac electrophysiology: a systematic review of clinical and experimental data.Cardiovasc Res. 2019; 115: 501-509Crossref PubMed Scopus (17) Google Scholar, 3Osborn J.J. Experimental hypothermia; respiratory and blood pH changes in relation to cardiac function.Am J Physiol. 1953; 175 (70): 389-398Crossref PubMed Scopus (326) Google Scholar, 4Boba A. An abnormal electrocardiographic pattern and its relation to ventricular fibrillation (observations during clinical and experimental hypothermia).Am Heart J. 1959; 57: 255Crossref PubMed Scopus (6) Google Scholar Thirdly, the electrophysiological studies cited by Dr. Dietrichs and Dr. Strapazzon hypothesize a biphasic relationship between core temperature and myocardial irritability (VF-susceptibility). They rely on the classic hypothermia staging of mild-moderate-severe hypothermia which is based on core temperature. In contrast to this assumption, the Revised Swiss System is based on a relationship between the level of consciousness and myocardial irritability (risk of CA), independent of the core temperature; the main advantage of this classification. Even if using the original system and core temperatures, the received letter suggests that during cooling towards 30 °C (i.e., stage 2), the risk of VF increases, whereas further cooling to severe hypothermia (i.e., stage 3) seems to induce resistance to VF. This was not observed in the cited study by Darocha et al. Of 206 patients with witnessed hypothermic cardiac arrest, only five of 206 (2.4%) had a body temperature >28 °C (lower limit of Stage 2 of the original Swiss Staging System). The mean body temperature at which witnessed cardiac arrest occurred, considering all rhythms, was 23.9 °C.5Frei C. Darocha T. Debaty G. et al.Clinical characteristics and outcomes of witnessed hypothermic cardiac arrest: a systematic review on rescue collapse.Resuscitation. 2019; 137: 41-48Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar Lastly, even in the scenario where patients are at greater risk of VF at hypothermia stage II than at stage III, VF/pVT accounts for 64% of patients presenting with subsequent cardiac arrest. While patients can present in cardiac arrest after developing VF, up to one third may develop asystole or PEA arrest without prior VF.5Frei C. Darocha T. Debaty G. et al.Clinical characteristics and outcomes of witnessed hypothermic cardiac arrest: a systematic review on rescue collapse.Resuscitation. 2019; 137: 41-48Abstract Full Text Full Text PDF PubMed Scopus (23) Google Scholar We are delighted that the Revised Swiss System has already ignited an electrophysiologic debate based on animal studies, but we wish to emphasize the practical field use of the RSS. Focussing on the level of consciousness and risk of CA allows first responders using this system to focus on careful patient handling, efficient transport and evacuation to an appropriate health care facility. HB receives grants, as the Head of the Institute of Mountain Emergency Medicine, from Eurac Research, Bolzano, Italy . KZ is a paid author of the topic, Accidental Hypothermia in Adults, for UpToDate. The other authors have no conflicts of interest to disclose. Revised Swiss System for clinical staging of accidental hypothermia – At which core temperatures are patients at high risk of cardiac arrest?ResuscitationVol. 165PreviewWe have read with great interest the Revised Swiss System for clinical staging of accidental hypothermia published in this journal by Musi et al.1 When an accurate core temperature measurement is not available for patients with primary accidental hypothermia,2 the authors propose a revised system that uses the level of consciousness as the primary element for staging. The authors suggest to use the score also to help identifying patients at higher risk of cardiac arrest. It has generally been assumed that the risk for hypothermia-induced arrhythmias and cardiac arrest negatively correlates to reduction of core temperature. Full-Text PDF

High Altitude Medicine & BiologyVol. 22, No. 2 Book ReviewsFree AccessBook Review of Mountain Emergency Medicine (1st Edition) by Hermann Brugger, Ken Zafren, Luigi Festi, Peter Paal, and Giacomo StrappazzonAlison SheetsAlison Sheets—Reviewed by: Alison Sheets, MD, Boulder, Colorado, USA Search for more papers by this authorPublished Online:23 Jun 2021https://doi.org/10.1089/ham.2021.29023.sheAboutSectionsPDF/EPUB ToolsPermissionsDownload CitationsTrack CitationsAdd to favorites Back To Publication ShareShare onFacebookTwitterLinked InRedditEmail Mountain Emergency Medicine, 1st Edition, by Hermann Brugger, Ken Zafren, Luigi Festi, Peter Paal, and Giacomo Strappazzon, Edra Publishers, 672 pp., ISBN: 978-8821447334.Mountain activities and the accidents and illnesses that occur there have been documented over centuries. Recognition of the inherent dangers of high altitude, cold, snow, avalanches, rock fall, and fall from heights as well as illnesses from the exertions of reaching these high places is found in the literature of most mountain cultures. “Again, on passing the Great Headache Mountain, the Little Headache Mountain, the Red Land, the Fever Slope, men's bodies became feverish, they lose colour, and are attacked with headache and vomiting; the asses and cattle being all in like condition…” Ch'ien Han Shu, 30 BC.Mountain Emergency Medicine, edited by Hermann Brugger, Ken Zafren, Luigi Festi, Giacomo Strappazzon, and Peter Paal, is written for the rescuers who respond to these incidents. This substantial book is a product of the International Commission on Alpine Rescue's (ICAR) Medical Commission on mountain emergency medicine (MEDCOM). As a complete update and revision of ICAR MEDCOM's Consensus Guidelines on Mountain Emergency Medicine and Risk Reduction, published in 2001, this book defines the practice of mountain emergency medicine and mountain rescue. Forty-eight chapters cover everything from the history of mountain rescue, clothing for rescue work, organization of rescue teams, medical kits, multicasualty scenarios, and helicopter emergency medical services (HEMS), to all of the medical and traumatic conditions that may be encountered in mountainous terrain across the world. Aimed at the physician and advanced life support providers, the importance of teamwork and high-level technical mountaineering skills in addition to medical expertise is repeatedly emphasized. Historical background and illustrative scenarios add interest and context and help to lighten the sometimes-serious tone taken by chapter authors.Little is left out of this volume and several chapters provide welcome and unique additions to previous studies on the subject. Rescue team culture and the state of the industry, while heavily oriented toward European teams, address the intricacies and issues of high-performing complex organizations operating in risk-laden environments. The important addition of the education and training of current and potential rescue team members, most notably through the diploma in mountain medicine courses, illustrates the state-of-the-art approach to adult education in outdoor topics and could enhance any new or existing training programs. Although helicopter-based rescue, in contrast to HEMS, is much less common outside of the European Alps, the extensive experience of the contributors to these chapters is both inspiring and informative. The detailed discussion of dynamic hoist operations and the flight physics behind this technique has not, to my knowledge, been included in previous, nonaviation-based, publications.Some improvements for the next edition would be more diversity in the authors of the chapters and the referenced “significant rescuers” with regard to nationality, gender, medical certification, and field rescue experience. Each chapter reads as a stand-alone work and more ruthless editing would have helped reduce repetition and errors. Discussions of cardiopulmonary resuscitation indications and termination are in multiple chapters and do not always concur. Likewise other aspects of patient assessments, treatments, and packaging are found in multiple chapters, often repeating the same information. Finally, a greater acknowledgment of the practices outside of Europe, where physicians are rarely present on scene during mountain rescue or available for consultation, would make Mountain Emergency Medicine truly international and more useful for the less medically advanced rescuer.Regardless, this book has something for anyone involved in mountain rescue medicine, expedition medicine, guiding operations, or outdoor medical education. The stories alone will keep rescue enthusiasts reading. The clinicians and scientists will appreciate the newest medical innovations and the multitude of research updates. And for the majority of mountain rescuers, the practical technical recommendations, reinforcement of the medical basics, and the comprehensive coverage of the subject of mountain emergency medicine will ensure this manual's place on the bookshelf.FiguresReferencesRelatedDetails Volume 22Issue 2Jun 2021 InformationCopyright 2021, Mary Ann Liebert, Inc., publishersTo cite this article:Alison Sheets.Book Review of Mountain Emergency Medicine (1st Edition) by Hermann Brugger, Ken Zafren, Luigi Festi, Peter Paal, and Giacomo Strappazzon.High Altitude Medicine & Biology.Jun 2021.243-243.http://doi.org/10.1089/ham.2021.29023.shePublished in Volume: 22 Issue 2: June 23, 2021PDF download

Clinical staging of accidental hypothermia is used to guide out-of-hospital treatment and transport decisions. Most clinical systems utilize core temperature, by measurement or estimation, to stage hypothermia, despite the challenge of obtaining accurate field measurements. Recent studies have demonstrated that field estimation of core temperature is imprecise. We propose a revision of the original Swiss Staging system. The revised system uses the risk of cardiac arrest, instead of core temperature, to determine the staging level. Our revised system simplifies assessment by using the level of responsiveness, based on the AVPU scale, and by removing shivering as a stage-defining sign.

Roy, Steven, Inigo Soteras, Alison Sheets, Richard Price, Kazue Oshiro, Simon Rauch, Don McPhalen, Maria Antonia Nerin, Giacomo Strapazzon, Myron Allen, Alistair Read, and Peter Paal. Guidelines for mountain rescue during the COVID-19 pandemic: official guidelines of the International Commission for Alpine Rescue. High Alt Med Biol. 22: 128–141, 2021. Background: In mountain rescue, uncertainty exists on the best practice to prevent coronavirus disease 2019 (COVID-19) transmission. The aim of this work was to provide a state-of-the-art overview of the challenges caused by the COVID-19 pandemic in mountain rescue. Methods: Original articles or reviews, published until December 27, 2020 in Cochrane COVID-19 Study Register, EMBASE, PubMed, and Google Scholar were included. Articles were limited to English, French, German, or Spanish with the article topic COVID-19 or other epidemics, addressing transmission, transport, rescue, or cardiopulmonary resuscitation. Results: The literature search yielded 6,190 articles. A total of 952 were duplicates and 5,238 were unique results. After exclusion of duplicates and studies that were not relevant to this work, 249 articles were considered for this work. Finally, 72 articles and other sources were included. Conclusions: Recommendations are provided for protection of the rescuer (including screening, personal protective equipment [PPE], and vaccination), protection of the patient (including general masking if low risk, specific PPE if high risk), equipment hygiene (including disinfection after every mission), use of single-use products, training and medical measures under COVID-19 precautions, and psychological wellbeing of rescuers during the COVID-19 pandemic. Adapted COVID-19 precautions for low-and-medium-income countries are also discussed.

Background Multiple trauma in mountain environments may be associated with increased morbidity and mortality compared to urban environments. Objective To provide evidence based guidance to assist rescuers in multiple trauma management in mountain environments. Eligibility criteria All articles published on or before September 30th 2019, in all languages, were included. Articles were searched with predefined search terms. Sources of evidence PubMed, Cochrane Database of Systematic Reviews and hand searching of relevant studies from the reference list of included articles. Charting methods Evidence was searched according to clinically relevant topics and PICO questions. Results Two-hundred forty-seven articles met the inclusion criteria. Recommendations were developed and graded according to the evidence-grading system of the American College of Chest Physicians. The manuscript was initially written and discussed by the coauthors. Then it was presented to ICAR MedCom in draft and again in final form for discussion and internal peer review. Finally, in a face-to-face discussion within ICAR MedCom consensus was reached on October 11th 2019, at the ICAR fall meeting in Zakopane, Poland. Conclusions Multiple trauma management in mountain environments can be demanding. Safety of the rescuers and the victim has priority. A crABCDE approach, with haemorrhage control first, is central, followed by basic first aid, splinting, immobilisation, analgesia, and insulation. Time for on-site medical treatment must be balanced against the need for rapid transfer to a trauma centre and should be as short as possible. Reduced on-scene times may be achieved with helicopter rescue. Advanced diagnostics (e.g. ultrasound) may be used and treatment continued during transport.

Introduction A history of preexisting hypertension is common in people participating in mountain activities; however, the relationship between blood pressure (BP), preexisting hypertension, and acute mountain sickness (AMS) is not well studied. We sought to determine these relationships among trekkers in the Everest region of Nepal. Methods This was a prospective observational cohort study of a convenience sample of adult, nonpregnant volunteers trekking in the Everest Base Camp region in Nepal. We recorded Lake Louise Scores for AMS and measured BP at 2860 m, 3400 m, and 4300 m. The primary outcome was AMS. Results A total of 672 trekkers (including 60 with history of preexisting hypertension) were enrolled at 2860 m. We retained 529 at 3400 m and 363 at 4300 m. At 3400 m, 11% of participants had AMS, and 13% had AMS at 4300 m. We found no relationship between AMS and measured BP values ( P>0.05), nor was there any relation of BP to AMS severity as measured by higher Lake Louise Scores ( P>0.05). Preexisting hypertension (odds ratio [OR] 0.16; 95% CI 0.025–0.57), male sex (OR 0.59; 95% CI 0.37–0.96), and increased SpO2 (OR 0.93; 95% CI 0.87–0.98) were associated with reduced rates of AMS in multivariate analyses adjusting for known risk factors for AMS. Conclusions AMS is common in trekkers in Nepal, even at 3400 m. There is no relationship between measured BP and AMS. However, a medical history of hypertension may be associated with a lower risk of AMS. More work is needed to confirm this novel finding.

Multiple trauma in mountain environments may be associated with increased morbidity and mortality compared to urban environments. To provide evidence based guidance to assist rescuers in multiple trauma management in mountain environments. All articles published on or before September 30th 2019, in all languages, were included. Articles were searched with predefined search terms. PubMed, Cochrane Database of Systematic Reviews and hand searching of relevant studies from the reference list of included articles. Evidence was searched according to clinically relevant topics and PICO questions. Two-hundred forty-seven articles met the inclusion criteria. Recommendations were developed and graded according to the evidence-grading system of the American College of Chest Physicians. The manuscript was initially written and discussed by the coauthors. Then it was presented to ICAR MedCom in draft and again in final form for discussion and internal peer review. Finally, in a face-to-face discussion within ICAR MedCom consensus was reached on October 11th 2019, at the ICAR fall meeting in Zakopane, Poland. Multiple trauma management in mountain environments can be demanding. Safety of the rescuers and the victim has priority. A crABCDE approach, with haemorrhage control first, is central, followed by basic first aid, splinting, immobilisation, analgesia, and insulation. Time for on-site medical treatment must be balanced against the need for rapid transfer to a trauma centre and should be as short as possible. Reduced on-scene times may be achieved with helicopter rescue. Advanced diagnostics (e.g. ultrasound) may be used and treatment continued during transport.

INTRODUCTION:A better understanding of the nature of morbidity and mortality in avalanche accidents helps direct both rescue efforts as well as preventive strategies to reduce fatalities.METHODS:We reviewed all avalanche fatalities from the avalanche years beginning in 1994 to 2015 in the state of Colorado, United States, using the database maintained by the Colorado Avalanche Information Center. For each fatality, we obtained the coroner's official determination of cause of death, and autopsy records if one was performed. We used these records to determine cause of death. Injury severity scores (0-75 scale) were calculated for those victims who underwent autopsy.RESULTS:Mortality information was available for 110 fatalities occurring during the 21-year study period. Of these, 64 underwent autopsy. Asphyxia was the cause of death in 65% of fatalities (72/110). Trauma was the cause of death in 29% of the fatalities (32/110). Of these, the primary cause was multiple system trauma in 38% (12/32), head trauma in 31% (10/32), and spinal injuries in 19% (6/32). Of the victims who died of asphyxia and had autopsy, only 10% (4/42) also had significant trauma, defined as an injury severity score greater than 15. There were 6 fatalities from other causes, including hypothermia, drowning, and primary cardiac arrest. There was no correlation between trauma and mode of travel, avalanche type, or starting zone elevation.CONCLUSIONS:Asphyxia was the primary cause of death in avalanche fatalities in Colorado during our study period. The incidence of fatal trauma was 29% and did not correlate with user group demographics or avalanche characteristics.

Keyes, Linda E., Thomas Douglas Sallade, Charles Duke, Jennifer Starling, Alison Sheets, Sushil Pant, David S. Young, David Twillman, Nirajan Regmi, Benoit Phelan, Purshotam Paudel, Matthew McElwee, Luke Mather, Devlin Cole, Theodore McConnell, and Buddha Basnyat. Blood pressure and altitude: an observational cohort study of hypertensive and nonhypertensive Himalayan trekkers in Nepal. High Alt Med Biol. 18: 267- 277, 2017.Objectives: To determine how blood pressure (BP) changes with altitude in normotensive versus hypertensive trekkers. Secondary aims were to evaluate the prevalence of severe hypertension (BP 180/100mmHg) and efficacy of different antihypertensive agents at high altitude.Methods: This was an observational cohort study of resting and 24- hour ambulatory BP in normotensive and hypertensive trekkers at 2860, 3400, and 4300m in Nepal. Results: We enrolled 672 trekkers age 18 years and older, 60 with a prior diagnosis of hypertension. Mean systolic and diastolic BP did not change between altitudes in normotensive or hypertensive trekkers, but was higher in those with hypertension. However, there was large interindividual variability. At 3400 m, the majority (60%, n = 284) of normotensive participants had a BP within 10mmHg of their BP at 2860 m, while 21% (n = 102) increased and 19% (n = 91) decreased. The pattern was similar between 3400 and 4300m (64% [n = 202] no change, 21% [n = 65] increased, 15% [n = 46] decreased). BP decreased in a greater proportion of hypertensive trekkers versus normotensives (36% [n = 15] vs. 21% at 3400 m, p = 0.01 and 30% [n = 7] vs. 15% at 4300 m, p = 0.05). Severe hypertension occurred in both groups, but was asymptomatic. In a small subset of participants, 24- hour ambulatory BP monitoring showed that nocturnal BP decreased in normotensive (n = 4) and increased in hypertensive trekkers (n = 4).Conclusions: Most travelers, including those with well-controlled hypertension, can be reassured that their BP will remain relatively stable at high altitude. Although extremely elevated BP may be observed at high altitude in normotensive and hypertensive people, it is unlikely to be symptomatic. The ideal antihypertensive regimen at high altitude remains unclear.

P 4 .05)but was higher in HTN vs NTN subjects at each altitude (P o .05).However, we observed large interindividual variability.Between 2860 m and 3400 m, the majority (60%, n ¼ 284) of NTN SBPs did not change, while 21% (n ¼ 102) increased 410 mm Hg and 19% (n ¼ 91) decreased 410 mm Hg.The pattern was similar in NTNs between 3400 m and 4300 m: (65% [n ¼ 202] no change, 21% [n ¼ 65] increased, 15% [n ¼ 46] decreased).A greater proportion of HTN trekkers had SBP decreases between 2860 m and 3400 m (45% [n ¼ 19] no change, 19% [n ¼ 8] increased, 36% [n ¼ 15] decreased) and between 3400 m and 4300 m (44% [n ¼ 10], 26% [n ¼ 6], 30% [n ¼ 7]), respectively.Conclusions.-Inmost individuals, with and without HTN, BP is likely to change less than 10 mm Hg at altitudes up to 4300 m.In general, travelers, including those with well-controlled HTN, may be reassured that their blood pressure will remain relatively stable at high altitude.

BACKGROUND The number of tourists in Nepal doubled between 2003 and 2013 is nearly 800 000. With the increased popularity of trekking, the number of those with pre-existing medical conditions requiring access to healthcare is likely to increase. We therefore sought to characterize the demographics and health status of trekkers on the Everest Base Camp route in the Solukhumbu Valley. In addition, we report cases that illustrate the potential complications of an ageing and medicated population of trekkers with underlying diseases. METHODS Trekkers over 18 years were enrolled in a larger observational cohort study on blood pressure at high altitude at 2860 m. They answered a questionnaire regarding demographics, medical history and current medications. Acute medical problems relating to medication use that were brought to the attention of investigators were documented and are presented as case reports. RESULTS We enrolled 670 trekkers, 394 (59%) male, with a mean age of 48 years (range 18-76). Pre-existing medical conditions were reported by 223 participants (33%). The most frequent conditions included hypertension, hypercholesterolemia, migraines and thyroid dysfunction. A total of 276 participants (41%) reported taking one or more medications. The most common medications were acetazolamide (79, 12%), antihypertensives (50, 8%) and NSAIDs (47, 7%), with 30 classes of drugs represented. Excluding acetazolamide, older trekkers (age >50 years) were more likely than younger ones to take medications (OR = 2.17; 95% CI 1.57-3.00; P <0.05). Acetazolamide use was not related to age. CONCLUSIONS Our findings illustrate a wide variety of medical conditions present in trekkers in Nepal with wide-ranging potential complications that could pose difficulties in areas where medical care is scarce and evacuation difficult. Our cases illustrate the potential problems polypharmacy poses in trekkers, and the need for local and expedition healthcare workers to be aware of, and prepared for the common medical conditions present.

Severe and uncontrolled hypertension have been reported in high altitude sojourners but have not been studied systematically. Additionally, few studies have evaluated the efficacy of antihypertensive medications at high altitude. We documented the prevalence of severe hypertension and efficacy of antihypertensive medications in high-altitude trekkers in Nepal. Observational cohort study in Nepal's Solukhumbu Valley. We recruited trekkers 18 years of age and older. Subjects reported demographics, medical history, and medications. Resting blood pressure (BP) was recorded at 2860 m, 3400 m, and 4300 m on ascent and descent. Severe hypertension was defined as systolic BP ≥180 and/or diastolic BP ≥100. We enrolled 60 self-reported hypertensive (HTN) trekkers and 606 normotensive (NTN) trekkers. Out of 2158 BP measurements at all altitudes, 109 (5%) were severe. Of these, 39 occurred in 22 (37%) HTN trekkers and 70 were distributed among 51 (8%) NTN trekkers. Occurrence of severe hypertension was similar across altitudes (P < .05). No subject was symptomatic. Among HTN trekkers, 10 took no antihypertensives and 5 of those had one or more severe BP measurements, accounting for 21% of all severe BPs in HTN trekkers. Seven out of 14 subjects on angiotensin converting enzyme inhibitors (ACEI) accounted for another one-third of all severe BPs. No subject taking a beta-blocker (BB), thiazide, ACEI + calcium channel blocker (CCB), ACEI + BB, or angiotensin receptor blocker (ARB) + alpha-1 antagonist had severe hypertension. Severe hypertension occurred in a smaller proportion of trekkers on combinations of CCB plus either ACEIs (0/3) or ARBs (1/3), and those taking more than 3 antihypertensives (1/3). Asymptomatic severe hypertension occurred at high altitude in normotensive and hypertensive subjects, but was more common in those with underlying hypertension. The clinical importance of these episodes is unclear. Our preliminary results suggest some antihypertensives may be more effective at high altitude than others.