Acute mountain sickness on Jade Mountain: Results from the real-world practice (2018-2019).

Acute mountain sickness (AMS) is initiated in response to a hypoxic and hypobaric environment at a high altitude. The precise prevalence of AMS in Jade Mountain climbers remained largely unknown, particularly data obtained from real medical consultations. An overnight stay at the Pai-Yun Lodge (3402 m) is usually required before an ascent of the Jade Mountain. Since 2004, a Pai-Yun Clinic has been established in the Pai-Yun Lodge. The Pai-Yun Clinic provided regular and emergency medical service every weekend. We conducted a retrospective study by using medical records from the Pai-Yun Clinic between 2018 and 2019. A total of 1021 patients were enrolled, with 56.2 % males. Different age groups were 3.2 %, 54.5 %, 37.9 %, and 4.4 % in <20, 20-39, 40-59, and ≥60 years, respectively. There were 582 (57.0 %) patients diagnosed to have AMS (230 [39.5 %] were mild type and 352 [60.5 %] were severe type). The factors associated with AMS development included young age, absence of climbing history (>3000 m) within the last 3 months, first climbing (>3000 m) experience, taking preventive medication, low oxygen saturation, and a high Lake Louise AMS score (LLAMSS). The factors associated with AMS severity included absence of taking preventive medication, low oxygen saturation, and a high LLAMSS. Approximately 15 % of Jade Mountain climbers needed medical service, of which 60 % had AMS. 60 % of patients with AMS must require oxygen supply or medication prescription. Oxygen saturation measure and LLAMSS evaluation are reasonable tools to predict the occurrence and severity of AMS on Jade Mountain.

A Season at the Himalayan Rescue Association Aid Post in Manang.

The Himalayan Rescue Association (HRA) has operated high altitude clinics in Nepal for 50 years, with rising visitor numbers, especially from India, China, and Nepal. New roads have eased access and increased the speed of ascent in some areas. Our aim was to provide a description of the activities, clinical problems, and lecture attendees of the HRA aid post in Manang over one season. We also highlight the evolving challenges of providing healthcare and education in the high Himalayan region. We describe the clinical and educational activities of the HRA aid post in Manang from September 24 to December 1, 2023. Prospective clinical data collection included anonymized patient demographics and diagnoses. Lecture data were taken from the attendee register and by daily manual counts of lecture attendees. We saw 376 patients, 62% of whom were Nepalis. Infectious diseases (42%) and altitude illness (16%) were the most common problems. A total of 846 people from 47 countries attended the daily altitude lectures. Only 5% of attendees were Nepali. Electrical supply interruptions and limitations in medical evacuation options were among the challenges of providing care at a high altitude clinic and preventing altitude illness using educational lectures. Altitude illness remains a common and potentially life-threatening problem, with risks increased by rapid ascent enabled by new road access and by ignorance of risks of altitude among travelers, especially Nepalis. Language barriers in educational outreach call for novel approaches and interventions that will ensure the effectiveness of altitude education.

Inappropriate Acetazolamide Use for a Hiker Who Developed Acute Kidney Injury.

Prophylactic use of acetazolamide (ACZ) to prevent acute mountain sickness (AMS) is a common practice among high altitude travelers and mountaineers. With its use comes a possible risk of acute kidney injury (AKI). We present a case in which a 56-year-old male hiker in Grand Canyon National Park developed acute exertional rhabdomyolysis and subsequent AKI while taking prophylactic ACZ to prevent AMS. This medication was prescribed despite the hiker encountering only moderate altitude at Grand Canyon with a planned descent within <24 h. The resulting AKI was determined to be the combined result of acute exertional rhabdomyolysis and dehydration/hypovolemia, with the ACZ, a diuretic, as a contributing factor. Medical providers need to recognize the risks/benefits with ACZ use for AMS prophylaxis and avoid prescribing it to individuals whose altitude exposure and activity fall outside the clinical practice guidelines recommended for use.

A Randomized Phase 2 Study to Evaluate Efficacy and Safety of AR36 for Prevention of Acute Mountain Sickness.

INTRODUCTION: AR36 is a pharmaceutical-grade plant extract used to support cardiovascular health in traditional Chinese medicine. Studies suggest that AR36 may prevent acute mountain sickness (AMS) during gradual ascent to high altitude. This randomized, placebo-controlled Phase 2 trial aimed to evaluate dosing regimens and assess efficacy and safety of AR36 for AMS prevention during rapid ascent. METHODS: Participants received placebo, low-dose AR36 (225 mg twice daily for 14 d prior and 5 d at altitude), or high-dose AR36 (12 d placebo, 300 mg twice daily for 2 d prior and 5 d at altitude). The primary efficacy outcome was 1993 Lake Louise Scoring System (LLSS) score on the morning after ascent. Safety was assessed through the proportion of treatment-emergent adverse events (TEAEs). RESULTS: One hundred thirty-two participants were randomized. Mean±SD age was 31.4±8.6 (range, 19-54) y. Baseline characteristics did not differ across groups. Lake Louise Scoring System scores on Day 16 in the placebo, low-dose, and high-dose groups were 4.03 (2.88), 4.42 (3.17), and 3.5 (2.31), respectively (placebo versus low-dose, P=0.462; placebo versus high-dose, P=0.574; n=110). The incidence of AMS on Day 16 was 66.7% in the placebo, 61.1% in the low-dose, and 55.3% in the high-dose group (P=0.66). The proportion of TEAEs in the placebo, low-dose, and high-dose groups was 38.4% (81), 28.4% (60), and 33.2% (70), respectively (P=0.205; n=127). There was no statistical difference between groups in LLSS, incidence of AMS, or TEAEs. CONCLUSIONS: AR36 did not improve LLSS or AMS incidence using the current regimens. AR36 was well tolerated.

Respiratory physiology at high altitude and considerations for pediatric patients.

Over 150 million people, including many children, live at high altitude (>2500 m) with the majority residing in Asia and South America. With increases in elevation, the partial pressure of oxygen (pO2) is reduced, resulting in a hypobaric hypoxic environment. Fortunately, humans have evolved adaptive processes which serve to acclimate the body to such conditions. These mechanisms, occurring along a specific time course, result in tachypnea, tachycardia, diuresis, and hematopoiesis, and a shift in the oxygen dissociation curve favoring an increased affinity for oxygen. These, along with other physiological effects, including increased pulmonary vascular resistance, alterations in cerebral blood flow, and changes in sensitivity to opioids, must be considered when administering anesthesia at high altitudes. Susceptible individuals or those who ascend too quickly may outpace the body's ability to acclimate resulting in one or more forms of high-altitude sickness ranging from the milder acute mountain sickness to the more serious conditions of high-altitude pulmonary edema and cerebral edema, either of which can be life-threatening if not promptly recognized and treated. Since the adaptive mechanisms for acclimatization greatly affect the cardiopulmonary systems, patients with underlying health issues such as sleep apnea, congenital heart disease, and asthma may have susceptibilities and warrant special consideration. Clinicians should have an understanding of the physiologic adaptations, anesthetic considerations, and special concerns in these populations in order to offer the best care possible.

Poor Knowledge of Acute Mountain Sickness in Latin American Medical Students.

INTRODUCTION: Acute altitude exposure is a common event in Latin America that can result in mild to severe altitude illness. Medical students from some Latin American countries receive little information on this topic. Our aim was to determine the knowledge and incidence of acute mountain sickness (AMS), as well as the methods used to prevent AMS among medical students attending the Pan-American Student Meeting in Cusco, Peru, a city at high altitude (3400 m). METHODS: We conducted a cross-sectional study on medical students attending a conference. Participants completed a questionnaire on the day of registration that collected demographic data and investigated students' knowledge of AMS, its prophylaxis, and their personal experience of symptoms. RESULTS: A total of 840 students attended the meeting. Two hundred eighty-eight returned surveys, 51 from high altitude locations. Respondent age was 23±3 y (mean±SD), and 72% were female. Thirty-two percent had basic knowledge about symptoms of AMS. Headache was recognized as a symptom by 79%. Knowledge of AMS prophylaxis was reported by 70%. Coca leaf products and dimenhydrinate were mentioned by 30 and 16%, respectively, whereas acetazolamide was recognized by only 10% of participants. AMS incidence was 42%. Prophylactic measures were adopted by 47% of the participants in our study. Thirty-six percent used dimenhydrinate and 27% used coca tea. Less than 1% used acetazolamide as recommended. CONCLUSIONS: We found poor knowledge of AMS and effective prophylaxis among medical students from several South American countries traveling to 3400 m.

Accessory Climbing Routes Associated With More Rescue Operations Than the Main Climbing Route: A Retrospective 12-Year Report of Yushan National Park.

INTRODUCTION: This study compared the casualties and types of rescues conducted on the main climbing route (MCR) and accessory climbing routes (ACRs) in Yushan National Park (YSNP) between 2008 and 2019. METHODS: We collected the following information for all documented mountain rescue operations conducted on the MCRs and ACRs in YSNP between 2008 and 2019: accident location, casualty type, victim number, and type of rescue. The victims were categorized as to injury, illness, mortality, or no medical problem (NMP) groups according to their condition at the time of rescue. RESULTS: Two-hundred forty-four rescue operations involving 329 victims were conducted during the 12-y study period. Among them, 105 (32%) did not require medical treatment, 102 (31%) were injured, 82 (25%) were ill, and 40 (12%) were deceased. Of the 82 individuals with illness, 69 (84%) had acute altitude sickness. The accident and mortality rates on the ACRs were significantly higher than those on the MCR (P<0.001; χ2). The ACR incidents involved significantly higher percentages of helicopter-based rescues and victims in the NMP group (P<0.001). CONCLUSIONS: Acute altitude sickness accounted for most of the rescues. ACRs had higher injury and mortality rates and required more helicopter-based rescues for patients who did not have medical problems. This study may serve as a reference to reduce casualties and overuse of helicopters by educating tourists on the appropriate use of maps and the evaluation of trails in relation to weather conditions.

Marching to the Beet: The effect of dietary nitrate supplementation on high altitude exercise performance and adaptation during a military trekking expedition.

PURPOSE: The aim was to investigate the effect of dietary nitrate supplementation (in the form of beetroot juice, BRJ) for 20 days on salivary nitrite (a potential precursor of bioactive nitric oxide), exercise performance and high altitude (HA) acclimatisation in field conditions (hypobaric hypoxia). METHODS: This was a single-blinded randomised control study of 22 healthy adult participants (12 men, 10 women, mean age 28 ± 12 years) across a HA military expedition. Participants were randomised pre-ascent to receive two 70 ml dose per day of either BRJ (~12.5 mmol nitrate per day; n = 11) or non-nitrate calorie matched control (n = 11). Participants ingested supplement doses daily, beginning 3 days prior to departure and continued until the highest sleeping altitude (4800 m) reached on day 17 of the expedition. Data were collected at baseline (44 m altitude), at 2350 m (day 9), 3400 m (day 12) and 4800 m (day 17). RESULTS: BRJ enhanced the salivary levels of nitrite (p = 0.007). There was a significant decrease in peripheral oxygen saturation and there were increases in heart rate, diastolic blood pressure, and rating of perceived exertion with increasing altitude (p=<0.001). Harvard Step Test fitness scores significantly declined at 4800 m in the control group (p = 0.003) compared with baseline. In contrast, there was no decline in fitness scores at 4800 m compared with baseline (p = 0.26) in the BRJ group. Heart rate recovery speed following exercise at 4800 m was significantly prolonged in the control group (p=<0.01) but was unchanged in the BRJ group (p = 0.61). BRJ did not affect the burden of HA illness (p = 1.00). CONCLUSIONS: BRJ increases salivary nitrite levels and ameliorates the decline in fitness at altitude but does not affect the occurrence of HA illness.

Altered cardiac repolarisation in highlanders with high-altitude pulmonary hypertension during wakefulness and sleep.

High-altitude pulmonary hypertension (HAPH) is an altitude-related illness associated with hypoxaemia that may promote sympathetic excitation and prolongation of the QT interval. The present case-control study tests whether QT intervals, markers of malignant cardiac arrhythmias, are prolonged in highlanders with HAPH (HAPH+) compared to healthy highlanders (HH) and healthy lowlanders (LL). The mean pulmonary artery pressure (mPAP) was measured by echocardiography in 18 HAPH+ (mPAP, 34 mmHg) and 18 HH (mPAP, 23 mmHg) at 3,250 m, and 18 LL (mPAP, 18 mmHg) at 760 m, Kyrgyzstan (p < .05 all mPAP comparisons). Groups were matched for age, sex and body mass index. Electrocardiography and pulse oximetry were continuously recorded during nocturnal polysomnography. The heart rate-adjusted QT interval, QTc, was averaged over consecutive 1-min periods. Overall, a total of 26,855 averaged 1-min beat-by-beat periods were semi-automatically analysed. In HAPH+, maximum nocturnal QTc was longer during sleep (median 456 ms) than wakefulness (432 ms, p < .05) and exceeded corresponding values in HH (437 and 419 ms) and LL (430 and 406 ms), p < .05, respectively. The duration of night-time QTc >440 ms was longer in HAPH+ (median 144 min) than HH and LL (46 and 14 min, p < .05, respectively). HAPH+ had higher night-time heart rate (median 78 beats/min) than HH and LL (66 and 65 beats/min, p < .05, respectively), lower mean nocturnal oxygen saturation than LL (88% versus 95%, p < .05) and more cyclic oxygen desaturations (median 24/hr) than HH and LL (13 and 3/hr, p < .05, respectively). In conclusion, HAPH was associated with higher night-time heart rate, hypoxaemia and longer QTc versus HH and LL, and may represent a substrate for increased risk of malignant cardiac arrhythmias.

Efficacy and safety of inhaled budesonide on prevention of acute mountain sickness during emergent ascent: a meta-analysis of randomized controlled trials.

BACKGROUND: Acute Mountain Sickness (AMS) is a pathophysiologic process that occurs in non-acclimated susceptible individuals rapidly ascending to high-altitude. Barometric pressure falls at high altitude and it translates to a decreased partial pressure of alveolar oxygen (PAO2) and arterial oxygen (PaO2). A gradual staged ascent with sufficient acclimatization can prevent AMS but emergent circumstances requiring exposure to rapid atmospheric pressure changes - such as for climbers, disaster or rescue team procedures, and military operations - establishes a need for effective prophylactic medications. This systematic review and meta-analysis aim to analyze the incidence of AMS during emergent ascent of non-acclimatized individuals receiving inhaled budesonide compared to placebo. METHODS: This current meta-analysis was conducted according to the guidance of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. We searched PubMed, Google Scholar and Embase for relevant studies. The efficacy of budesonide in reducing incidence of AMS was evaluated by calculating the pooled ORs and 95% CIs. The efficacy of budesonide in maintaining hemoglobin-oxygen saturation was evaluated by calculating standard mean difference (SMD) and 95% confidence intervals. RESULTS: We found that at high altitude, inhaled budesonide was effective in reducing the incidence of mild AMS [OR: 0.37; 95% CI, 0.14 to 0.9, p = 0.042] but was ineffective in reducing the incidence of severe AMS [OR: 0.46; 95% CI, 0.14 to 1.41, p = 0.17]. Inhaled budesonide was also effective in maintaining SpO2 (SMD: 0.47; 95% CI, 0.09 to 0.84, p = 0.014) at high altitude. However, it was not effective in maintaining or improving pulmonary function at high altitude. Systematic-review found no adverse effects of budesoide in the dose used for prophylaxis of AMS. CONCLUSIONS: Our systematic review showed that prophylactic inhaled budesonide is effective in preventing mild AMS during emergency ascent but not effective in preventing severe AMS. Though statistically significant, authors recommend caution in interpretation of data and questions for further well designed randomized studies to evaluate the role of budesonide in prophylaxis of AMS during an emergent ascent.

Prospective Double-Blinded Randomized Field-Based Clinical Trial of Metoclopramide and Ibuprofen for the Treatment of High Altitude Headache and Acute Mountain Sickness.

INTRODUCTION: High altitude headache (HAH) and acute mountain sickness (AMS) are common pathologies at high altitudes. There are similarities between AMS and migraine headaches, with nausea being a common symptom. Several studies have shown ibuprofen can be effective for AMS prophylaxis, but few have addressed treatment. Metoclopramide is commonly administered for migraine headaches but has not been evaluated for HAH or AMS. We aimed to evaluate metoclopramide and ibuprofen for treatment of HAH and AMS. METHODS: We performed a prospective, double-blinded, randomized, field-based clinical trial of metoclopramide and ibuprofen for the treatment of HAH and AMS in 47 adult subjects in the Mount Everest region of Nepal. Subjects received either 400 mg ibuprofen or 10 mg metoclopramide in a 1-time dose. Lake Louise Score (LLS) and visual analog scale of symptoms were measured before and at 30, 60, and 120 min after treatment. RESULTS: Subjects in both the metoclopramide and ibuprofen arms reported reduced headache severity and nausea compared to pretreatment values at 120 min. The ibuprofen group reported 22 mm reduction in headache and 6 mm reduction in nausea on a 100 mm visual analog scale at 120 min. The metoclopramide group reported 23 mm reduction in headache and 14 mm reduction in nausea. The ibuprofen group reported an average 3.5-point decrease on LLS, whereas the metoclopramide group reported an average 2.0-point decrease on LLS at 120 min. CONCLUSIONS: Metoclopramide and ibuprofen may be effective alternative treatment options in HAH and AMS, especially for those patients who additionally report nausea.

The correct measurement of oxygen saturation at high altitude.

BACKGROUND: Compared to measurements at sea level, measurement of oxygen saturation by pulse oximetry (SpO2) at altitude differs fundamentally because of the cyclical course of SpO2, caused by periodic breathing. Therefore, the determination of a representative SpO2 value is difficult. In the literature, recommendations for a standardized measurement procedure are missing; different studies measure SpO2 in different ways. KEY QUESTION: Does the visually determined SpO2 value correlate with the actual average of the measurement interval? METHODS: Four participants of an expedition (6013 m; Pakistan), familiar with pulse oximetry at altitude, wrote down the representative value of the measurement interval of 3 min (SpO2visual) according to their individual observation. The used pulse oximeter saved the value for SpO2 every 4 s. Based on this, the calculated mean (SpO2memory) was compared to SpO2visual after finishing the expedition (128 measurements > 2500 m). RESULTS: The spread of the single values within the measurement interval is high (in single cases up to 17%-points) in case of insufficient acclimatization. With increasing acclimatization, the measured values stabilize. SpO2visual differs only marginally (- 0.4%-points; ± 0.8) compared to SpO2memory. CONCLUSIONS: The correct pulse oximetric determination of SpO2 at high altitude requires a standardized measurement procedure; the investigator is familiar and trained. Anyway, the measurements have to be done in the continuous mode of the pulse oximeter over a sufficient timeframe (3 SpO2-fluctuation cycles; 2-3 min). We recommend to record the maximum and the minimum value of the measurement interval and to use a pulse oximeter device with memory function.

Successful Summit of Two 8000 m Peaks After Recent High Altitude Pulmonary Edema.

There is little information in the literature on the safety of reascent to high altitude shortly after resolution of severe acute altitude illness, including high altitude pulmonary or cerebral edema. We present a case of a 52-y-old male climber who was diagnosed with high altitude pulmonary edema during the 2018 Everest spring climbing season, descended to low altitude for 9 d, received treatment, and returned to continue climbing with a very rapid ascent rate. Despite a very recent history of high altitude pulmonary edema and not using pharmacologic prophylaxis over a very rapid reascent profile, the climber successfully summited Mt. Everest (8848 m) and Lhotse (8516 m) without any problems.

Delayed-Onset High Altitude Pulmonary Edema: A Case Report.

High altitude pulmonary edema (HAPE) is a life-threatening altitude illness that usually occurs in insufficiently acclimatized climbers in the first few days at altitudes above 2500 m. Acetazolamide is recommended for prophylaxis of acute mountain sickness, but a role for acetazolamide in the prevention of HAPE has not been established. We report a case of a trekker with previous high altitude experience who developed HAPE 8 d after arrival to altitude despite what was believed to be a conservative ascent profile.

Pediatric High Altitude Cerebral Edema in the Nepal Himalayas.

High altitude cerebral edema (HACE) is a rare complication of ascent to altitudes of over 2500 m (8200 ft). We are not aware of a previously published case report of HACE in a patient under the age of 18 y. We report on 2 cases of suspected HACE in 2 patients, aged 12 and 16 y, who presented to the Manang Himalayan Rescue Association clinic at 3500 m. The 16-y-old patient presented with severe headache, vomiting, and ataxia after rapid ascent to 3800 m. The 12-y-old patient presented with severe headache, vomiting, visual disturbances, and ataxia at 4500 m, which began to resolve with descent to the clinic at 3500 m. Our cases suggest that HACE can occur in children and adolescents. Because there are no specific guidelines for treatment of acute mountain sickness or HACE in patients under the age of 18 y, we recommend treatment as for adults: oxygen, immediate descent, and dexamethasone. Simulated descent in a portable hyperbaric chamber can be used if oxygen is not available and if actual descent is not possible.

[High altitude illness and related diseases - a review].

Upon reaching a height over 2500 m above seal level symptoms of altitude illness can develop over 1 - 5 days. The risk is mainly -determined by the altitude and rate of ascent and the symptoms vary. Most common are symptoms of acute mountain illness (AMS) but more dangerous high altitude cerebral edema (HACE) and high altitude pulmonary edema (HAPE) can also develop. The causes of AMS, HACE and HAPE are lack of oxygen and insufficient acclimatization, but the presenting form is determined by the responses of the body to the lack of oxygen. The most common symptoms of AMS include headache, fatique and nausea, but insomnia and nausea are also common. The most common symptoms of HAPE are breathlessness and lassitude whereas the cardinal sign of HACE is ataxia, but confusion and loss of consciousness can also develop. In this article all three main forms of altitude illness are reviewed. The emphasis is on preventive measures and treatment but new knowledge on pathogenesis is also addressed.

The Epidemiology and Medical Morbidity of Long-Distance Backpackers on the John Muir Trail in the Sierra Nevada.

INTRODUCTION: The baseline characteristics and medical morbidity of hikers on the 354 km (220 mi) John Muir Trail (JMT) have not been previously reported. METHODS: Using online and on-site recruitment, hikers completing the JMT in 2014 were directed to an online 83-question survey. Pearson correlations, regression models, and descriptive statistics were applied to data, reported as mean±SD (range). Statistical significance was set at P<0.05. RESULTS: Of 771 respondents, 57% were men aged 43±14 (13-76) y; they hiked 15.2±7.6 (5-34) days and traveled 272±129 (45-1207) km (169±80 [28-750] mi). Backpackers lost 3.5±2.6 (+3.6 to -18.2) kg (7.7±5.8 [+8 to -40] lbs). Over half (57%) of respondents reported illness or injury, with blisters (57%), sleep problems (57%), and pack strap pain (46%) most prevalent. Altitude illness affected 37%. Thirty hikers left the trail; of these, 4 required emergency medical services evacuations (3 by helicopter). Increasing age, base pack weight, and body mass index (BMI) were all associated with a decrease in the distance hiked per day. Higher base pack weight was associated with illness or injury, whereas older age was slightly protective. Increasing BMI was associated with a slight increase in medical illness or injury and a strong association with evacuation from the trail. CONCLUSIONS: JMT hikers experienced medical issues seen on other national trails. Weight loss was prevalent. Most hikers had medical complaints, with few seeking medical attention. Heavy packs and higher BMIs were associated with undesirable outcomes, while older hikers fared better.

Impact of a Newly Constructed Motor Vehicle Road on Altitude Illness in the Nepal Himalayas.

OBJECTIVE: This study investigated the impact that motor vehicle travel along a newly constructed road has on altitude illness (including acute mountain sickness, high-altitude cerebral edema, and high-altitude pulmonary edema). The new road from Besisahar (760 m) to Manang (3540 m) in Nepal was completed in December 2014. METHODS: We enrolled all patients diagnosed with altitude illness at the Himalayan Rescue Association Manang clinic in fall 2016. Phi coefficients were calculated to test for an association between Nepali ethnicity and rapid ascent by motor vehicle. A retrospective review looked at all patients with altitude illness from fall (September-November) 2010 to spring (February-May) 2016. RESULTS: In fall 2016, more than half (54%) of patients with altitude illness traveled to Manang by motor vehicle, and one-third (33%) reached Manang from low altitude (Besisahar) in less than 48 hours. Nepali nationality had a significant association with motor vehicle travel (phi +0.69, P < .0001) as well as with rapid ascent to Manang (phi +0.72, P < .0001). Compared to previous seasons, fall 2016 saw the most patients diagnosed with altitude illness. The proportion of people with altitude illness who traveled by vehicle and reached Manang in less than 48 hours was significantly greater than the proportion prior to completion of the road (P < .0001 for both). CONCLUSIONS: Rapid ascent by the newly constructed road from Besisahar to Manang appears to be related to a significant increase in the number of patients with all forms of altitude illness, especially among Nepalis. The authors believe that educational interventions emphasizing prevention are urgently needed.

Prophylactic Acetaminophen or Ibuprofen Results in Equivalent Acute Mountain Sickness Incidence at High Altitude: A Prospective Randomized Trial.

OBJECTIVE: Recent trials have demonstrated the usefulness of ibuprofen in the prevention of acute mountain sickness (AMS), yet the proposed anti-inflammatory mechanism remains unconfirmed. Acetaminophen and ibuprofen were tested for AMS prevention. We hypothesized that a greater clinical effect would be seen from ibuprofen due to its anti-inflammatory effects compared with acetaminophen's mechanism of possible symptom reduction by predominantly mediating nociception in the brain. METHODS: A double-blind, randomized trial was conducted testing acetaminophen vs ibuprofen for the prevention of AMS. A total of 332 non-Nepali participants were recruited at Pheriche (4371 m) and Dingboche (4410 m) on the Everest Base Camp trek. The participants were randomized to either acetaminophen 1000 mg or ibuprofen 600 mg 3 times a day until they reached Lobuche (4940 m), where they were reassessed. The primary outcome was AMS incidence measured by the Lake Louise Questionnaire score. RESULTS: Data from 225 participants who met inclusion criteria were analyzed. Twenty-five participants (22.1%) in the acetaminophen group and 18 (16.1%) in the ibuprofen group developed AMS (P = .235). The combined AMS incidence was 19.1% (43 participants), 14 percentage points lower than the expected AMS incidence of untreated trekkers in prior studies at this location, suggesting that both interventions reduced the incidence of AMS. CONCLUSIONS: We found little evidence of any difference between acetaminophen and ibuprofen groups in AMS incidence. This suggests that AMS prevention may be multifactorial, affected by anti-inflammatory inhibition of the arachidonic-acid pathway as well as other analgesic mechanisms that mediate nociception. Additional study is needed.

Altitude-Induced Pulmonary Hypertension on One-Day Rapid Ascent of Mount Fuji: Incidence and Therapeutic Effects of Sildenafil.

AIMS: Exposure to high altitudes especially with rapid ascent may induce hypoxic pulmonary vasoconstriction (HPV) and pulmonary hypertension (PH) possibly leading to life-threatening high-altitude pulmonary edema (HAPE). The aim of the study was to evaluate the incidence of PH on a 1-day rapid ascent up Mount Fuji (3775 m) in recreational climbers and also to determine the effectiveness of sildenafil for this rapid ascent-induced PH as measured by echocardiography. METHODS AND RESULTS: Twenty-five subjects who climbed Mount Fuji showed significantly increased pulmonary artery systolic pressure (PASP) from 22.3 ± 5.3 mmHg at sea level to 29.4 ± 8.7 mmHg at 3775 m. Five subjects showed PASP >35 mmHg (35.6-46.2 mmHg, average 42.0 ± 3.9 mmHg) and took oral sildenafil 50 mg after which PASP decreased significantly to 24.5 ± 4.6 mmHg (18.7-31.0 mmHg) after 30 minutes. CONCLUSIONS: One-day rapid ascent of Mount Fuji may induce mild-to-moderate PH and intervention with sildenafil can reduce this PH, suggesting that the therapeutic use of sildenafil would be more reasonable for the relatively infrequent occurrence of altitude-induced PH than its prophylactic use.