Mt Everest Base Camp Medical Clinic “Everest ER”: Epidemiology of Medical Events During the First 10 Years of Operation

Night-Time Heart Rate Variability during an Expedition to Mt Everest: A Case Report

Mt Everest has been gaining popularity from casual hiking athletes, climbers, and ultra-endurance marathon runners. However, living and sleeping at altitude increases the risk of injury and illness. This is because travel to high altitudes adversely affects human physiology and performance, with unfavourable changes in body composition, exercise capacity, and mental function. This is a case report of a climber who reached the summit of Mt Everest from the north side. During his 40-day expedition, we collected sleep quality data and night-time heart rate variability. During the night inside the tent, the air temperature ranged from -12.9 to 1.8 °C (-5.8 ± 4.9 °C) and the relative humidity ranged from 26.1 to 78.9% (50.7 ± 16.9%). Awake time was 17.1 ± 6.0% of every sleep-time hour and increased with altitude (r = 0.42). Sleep time (r = -0.51) and subjective quality (r = 0.89) deteriorated with altitude. Resting heart rate increased (r = 0.70) and oxygen saturation decreased (r = -0.94) with altitude. The mean NN, RMSSD, total power, LF/HF, and SD1 and SD2 were computed using the NN time series. Altitude reduced the mean ΝΝ (r = -0.73), RMSSD (r = -0.31), total power (r = -0.60), LF/HF ratio (r = -0.40), SD1 (r = -0.31), and SD2 (r = -0.70). In conclusion, this case report shows that sleeping at high altitudes above 5500 m results in progressively reduced HRV, increased awakenings, as well as deteriorated sleep duration and subjective sleep quality. These findings provide further insight into the effects of high altitude on cardiac autonomic function and sleep quality and may have implications for individuals who frequently spend time at high altitudes, such as climbers.

Companion Rescue and Risk Management of Trekkers on the Everest Trek, Solo Khumbu Region, Nepal

BACKGROUND

Trekking to high-altitude locations presents inherent health-related hazards, many of which can managed with specific first aid (FA) training. This study evaluates the trip preparation, FA knowledge, and FA self-assessment of trekkers (organized by tour operators vs. individually planned tours). Data obtained shall be used for specific FA trip preparation and management of emergencies en route for this population.

METHODS

A total of 366 trekkers on the Everest Base Camp Trek, Nepal, were interviewed using a questionnaire specifically designed to evaluate their FA knowledge and management of emergencies. Data evaluation was performed using descriptive statistics.

RESULTS

A total of 40.5% of trekkers experienced at least one medical incident during their trip, of which almost 50% were due to acute mountain sickness (AMS). There was more AMS in commercially organized groups than in individually planned ones (55% vs. 40%). For more than 50%, no medical care was available during their trip. A total of 80% could answer only 3/21 FA questions completely correctly. Only 1% showed adequate knowledge concerning FA strategies. A total of 70% were willing to enroll in an FA class specialized towards the needs of trekkers.

CONCLUSIONS

The importance of high-altitude FA knowledge and trip preparation is widely underestimated. There is an unmet demand amongst trekkers for specific wilderness FA classes.

Surviving a 400 m Fall on Mount Everest

Mountaineering is a dangerous recreational activity with falls causing severe injuries and deaths. Survival from falls longer than 100 m is uncommon. We present a case of a high-altitude porter on Mount Everest who fell 400 m and survived. He slipped from a ridge at 7000 m (22,900 ft). A rescue party found him above Camp 2 (6600 m, 21,600 ft) and arranged a helicopter rescue. The Everest ER medical team at Everest Base Camp (5400 m, 17,700 ft) received the climber. They identified a head injury without signs of other serious trauma. A doctor provided manual inline stabilization of the cervical spine, airway support, and ventilation for the patient during the helicopter and ground transport to a tertiary hospital in Kathmandu. The time from the fall to definitive hospital care was 2.5 h. The hospital emergency team diagnosed an epidural hematoma and subarachnoid hemorrhage without midline shift and right parietal, orbital, and maxillary fractures. The neurosurgical team evacuated the intracranial bleed. The patient spent 6 d in the hospital. He had a positive neurological outcome. He had mild cognitive impairment and vision loss in his left eye but could perform activities of daily living. He returned to physical work, but not to climbing. This case report provides evidence that survival is possible after falls from extreme heights and sheds light on the challenges of an evacuation from austere environments.

Long-Term Sequelae of Frostbite-A Scoping Review

Frostbite is tissue damage caused by freezing temperatures and constitutes an important cause of morbidity in cold climate zones and high altitude. The direct effects of sub-zero temperatures lead to tissue freezing, electrolyte shifts and pH alterations, microvascular damage, and eventually to cell death. Upon rewarming, inflammatory reperfusion injury and thrombosis may lead to further tissue damage. Several studies and various case reports show that many patients suffer from long-term sequelae such as vasomotor disturbances (associated with susceptibility to refreezing), and neuropathic and nociceptive pain, as well as damage to skeletal structures. There are still many uncertainties regarding the pathophysiology of these sequelae. It has been shown that the transient receptor potential channel (TRP) family plays a role in cold allodynia. Botulinum Toxin type A (BTX-A) injections have been reported to be beneficial in vasomotor and neuropathic disturbances secondary to frostbite. Epidural sympathetic block has been used for short-term treatment of frostbite induced chronic pain. Furthermore, amitriptyline, gabapentinoids, and duloxetine may have some benefits. Frostbite arthritis clinically resembles regular osteoarthritis. In children there is a risk of epiphyseal cartilage damage leading to bone deformities. Despite some promising therapeutic concepts, the scarcity of data on frostbite long-term sequelae in the literature indicates the need of more in-depth studies of this pathology in all its aspects.

Manifestation of Intracranial Lesions at High Altitude: Case Report and Review of the Literature

Speidel, Victor, Jan Christoph Purrucker, and Katarína Klobučníková. Manifestation of intracranial lesions at high altitude: case report and review of the literature. High Alt Med Biol. 22:87-89, 2021.-A 32-year-old man trekked to the South Everest Base Camp (5,364 m) in Nepal. On the last day of the ascent, he noticed some dysesthesia in his right leg and descended by helicopter. He suffered a generalized seizure shortly after his descent, followed by right-sided hemiparesis and speech arrest. Without the possibility of cerebral imaging, the patient was given dexamethasone intravenously who showed a marked improvement and regained the ability to speak. Magnetic resonance imaging later revealed a lesion in the left frontotemporal region with compression of brain parenchyma and minimal paralesional edema. A meningioma was later surgically resected. Although seizures are a common first manifestation of meningioma, we argue that the exposure to high altitude may have contributed to his symptoms, either by increasing the peritumoral edema by pathophysiology similar to high-altitude cerebral edema (HACE) or lowering the seizure threshold otherwise. This case shows a before unknown pre-existing condition becoming symptomatic at high altitude and illustrates the necessity for careful and immediate evaluation of every patient with new onset of unexplained focal neurological deficits or seizures at high altitude in addition to unspecific neurological symptoms commonly associated with HACE such as headaches, dizziness, lightheadedness, or ataxia.

Mountaineers on Mount Everest: Effects of age, sex, experience, and crowding on rates of success and death

Mount Everest is an extreme environment for humans. Nevertheless, hundreds of mountaineers attempt to summit Everest each year. In a previous study we analyzed interview data for all climbers (2,211) making their first attempt on Everest during 1990–2005. Probabilities of summiting were similar for men and women, declined progressively for climbers about 40 and older, but were elevated for climbers with experience climbing in Nepal. Probabilities of dying were also similar for men and women, increased for climbers about 60 and older (especially for the few that had summited), and were independent of experience. Since 2005, many more climbers (3,620) have attempted Everest. Here our primary goal is to quantify recent patterns of success and death and to evaluate changes over time. Also, we investigate whether patterns relate to key socio-demographic covariates (age, sex, host country, prior experience). Recent climbers were more diverse both in gender (women = 14.6% vs. 9.1% for 1990–2005) and in age (climbers ≥ 40 = 54.1% vs. 38.7%). Strikingly, recent climbers of both sexes were almost twice as likely to summit–and slightly less likely to die–than were comparable climbers in the previous survey. Temporal shifts may reflect improved weather forecasting, installation of fixed ropes on much of the route, and accumulative logistic equipment and experience. We add two new analyses. The probability of dying from illness or non-traumas (e.g., high-altitude illness, hypothermia), relative to dying from falling or from ‘objective hazards’ (avalanche, rock or ice fall), increased marginally with age. Recent crowding during summit bids was four-fold greater than in the prior sample, but surprisingly crowding has no evident effect on success or death during summit bids. Our results inform prospective climbers as to their current odds of success and of death, as well as inform governments of Nepal and China of the safety consequences and economic impacts of periodically debated restrictions based on climber age and experience.

Management and Outcome of Feet Deep Frostbite Injury (III and IV Degrees): A Series Report of 36 Cases

Deep feet frostbite is a severe trauma and often leads to amputation due to full-thickness skin necrosis and subcutaneous tissue damage. A retrospective analysis was performed between June 2013 and June 2019 to review the management measures and outcomes of clinical treatment, and available data had been collected including demographic characteristics, risk factors, and injury environment record. Treatment protocols, wound management, and outcomes were also presented. There were 36 patients diagnosed with deep feet frostbite with a mean age of 51.5 years; the ratio for male to female is 5:1. Drunk and mental disorders were the main risk behaviors for frostbite occurrence. As for the injury environment, mean temperature and wind speed were -20.5 °C and 3.3 m/s, respectively. Fourteen cases achieved wound healing without surgery intervention, 5 cases received skin graft, and 17 cases received amputation. Most amputations (12 cases) were restricted at toe level; only 1 case received whole feet amputation. Our finding indicated that feet deep frostbite in our hospital showed a male predominant and older age including various risk behaviors and coexistence risk factors. Clinical management based on pathology mechanism needs further improvement, as the amputation rate was still high. How to avoid amputation and lower the amputation level are the focus of future efforts.

Effects of dietary nitrate supplementation on microvascular physiology at 4559 m altitude - A randomised controlled trial (Xtreme Alps)

Native highlanders (e.g. Sherpa) demonstrate remarkable hypoxic tolerance, possibly secondary to higher levels of circulating nitric oxide (NO) and increased microcirculatory blood flow. As part of the Xtreme Alps study (a randomised placebo-controlled trial of dietary nitrate supplementation under field conditions of hypobaric hypoxia), we investigated whether dietary supplementation with nitrate could improve NO availability and microvascular blood flow in lowlanders. Plasma measurements of nitrate, nitrite and nitroso species were performed together with measurements of sublingual (sidestream dark-field camera) and forearm blood flow (venous occlusion plethysmography) in 28 healthy adult volunteers resident at 4559 m for 1 week; half receiving a beetroot-based high-nitrate supplement and half receiving an identically-tasting low nitrate ‘placebo’. Dietary supplementation increased plasma nitrate concentrations 4-fold compared to the placebo group, both at sea level (SL; 19.2 vs 76.9 μM) and at day 5 (D5) of high altitude (22.9 vs 84.3 μM, p < 0.001). Dietary nitrate supplementation also significantly increased both plasma nitrite (0.78 vs. 0.86 μM SL, 0.31 vs. 0.41 μM D5, p = 0.03) and total nitroso product (11.3 vs. 19.7 nM SL, 9.7 vs. 12.3 nM D5, p < 0.001) levels both at sea level and at 4559 m. However, plasma nitrite concentrations were more than 50% lower at 4559 m compared to sea level in both treatment groups. Despite these significant changes, dietary nitrate supplementation had no effect on any measured read-outs of sublingual or forearm blood flow, even when environmental hypoxia was experimentally reversed using supplemental oxygen. In conclusion, dietary nitrate supplementation does not improve microcirculatory function at 4559 m.

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Xtreme Alps is a randomised controlled field study of dietary nitrate at altitude.

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Dietary nitrate significantly increased plasma nitrate, nitrite & nitroso species.

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No changes in sublingual blood flow were seen in response to high dietary nitrate.

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Dietary nitrate did not alter forearm blood flow under any experimental condition.

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Dietary nitrate supplementation did not improve microcirculatory function at 4559 m

Cold Susceptibility of Digit Stumps Resulting from Amputation After Freezing Cold Injury in Elite Alpinists

Gorjanc, Jurij, Shawnda A. Morrison, Rok Blagus, and Igor B. Mekjavic. Cold susceptibility of digit stumps resulting from amputation after freezing cold injury in elite alpinists. High Alt Med Biol. 19:185-192, 2018.

AIM

The aim of the study was to assess whether previous freezing cold injury in fingers and/or toes might predispose alpinists to greater risk of further freezing cold injury, primarily due to a greater vasoconstrictor response to cold, resulting in a lower perfusion, reflected in lower skin temperature.

METHODS

Ten elite alpinists (N = 10; 8 male and 2 female) with amputations after freezing cold injury participated in a cold-water (8°C) immersion stress test of the hands and feet. Digit skin temperatures of amputated digits, their noninjured counterparts, noninjured digits of the affected side and noninjured digits of the corresponding side were measured. The skin temperatures were compared during three consecutive phases of the cold stress test: prewarming, cold water immersion, and passive heating.

RESULTS

Amputated toes cooled much faster compared to their uninjured counterparts (n = 26, p < 0.001), and attained lower skin temperatures during the cold exposure test (n = 26, p < 0.001). Higher cooling rate was observed in all the toes on the injured limb compared with the toes on the uninjured limb (n = 40, p < 0.001). In contrast to the toes, the fingers on the injured limb after freezing cold injury were warmer during cooling phase compared to uninjured fingers (n = 15, p < 0.001).

CONCLUSIONS

The lower digit temperatures observed in affected toe stumps during the cold stress test compared to the nonamputated toes may indicate a heightened risk of future freezing cold injury with subsequent cold exposures, as a consequence of less perfusion, reflected in the lower skin temperature. This relationship was not confirmed in the fingers.

Field Wound Care: Prophylactic Antibiotics

Adequate management of wounds requires numerous interventions, one of which is the appropriate use of antimicrobials to attempt to minimize the risk of excess morbidity or mortality without increasing toxicity or multidrug resistant bacterial acquisition. There are numerous recommendations and opinions for not only the use of systemic prophylactic antimicrobials, but also the agent, dose, route, and duration. To best address the implementation of systemic antimicrobials in a field scenario, one must weigh the factors that go into that decision and then determine the best agents possible. The epidemiologic triangle (ie, the host, the agent, and the environment) forms the basis for selecting the correct prophylactic antibiotic for field wound care. Extreme conditions can be encountered in both military and nonmilitary systems, requiring a unique selection process to make the right antibiotic choice. A modifiable weighted matrix, recommended previously for point of injury combat casualty care, assists in selecting the best oral and intravenous/intramuscular agent based on the epidemiologic risk determination.

Effects of dietary nitrate on respiratory physiology at high altitude - Results from the Xtreme Alps study

Nitric oxide (NO) production plays a central role in conferring tolerance to hypoxia. Tibetan highlanders, successful high-altitude dwellers for millennia, have higher circulating nitrate and exhaled NO (ENO) levels than native lowlanders. Since nitrate itself can reduce the oxygen cost of exercise in normoxia it may confer additional benefits at high altitude. Xtreme Alps was a double-blinded randomised placebo-controlled trial to investigate how dietary nitrate supplementation affects physiological responses to hypoxia in 28 healthy adult volunteers resident at 4559 m for 1 week; 14 receiving a beetroot-based high-nitrate supplement and 14 receiving a low-nitrate 'placebo' of matching appearance/taste. ENO, vital signs and acute mountain sickness (AMS) severity were recorded at sea level (SL) and daily at altitude. Moreover, standard spirometric values were recorded, and saliva and exhaled breath condensate (EBC) collected. There was no significant difference in resting cardiorespiratory variables, peripheral oxygen saturation or AMS score with nitrate supplementation at SL or altitude. Median ENO levels increased from 1.5/3.0  mPa at SL, to 3.5/7.4 mPa after 5 days at altitude (D5) in the low and high-nitrate groups, respectively (p = 0.02). EBC nitrite also rose significantly with dietary nitrate (p = 0.004), 1.7-5.1  μM at SL and 1.6-6.3 μM at D5, and this rise appeared to be associated with increased levels of ENO. However, no significant changes occurred to levels of EBC nitrate or nitrosation products (RXNO). Median salivary nitrite/nitrate concentrations increased from 56.5/786 μM to 333/5,194  μM  with nitrate supplementation at SL, and changed to 85.6/641 μM and 341/4,553 μM on D5. Salivary RXNO rose markedly with treatment at SL from 0.55 μM to 5.70 μM. At D5 placebo salivary RXNO had increased to 1.90 μM whilst treatment RXNO decreased to 3.26 μM. There was no association with changes in any observation variables or AMS score. In conclusion, dietary nitrate supplementation is well tolerated at altitude and significantly increases pulmonary NO availability and both salivary and EBC NO metabolite concentrations. Surprisingly, this is not associated with changes in hemodynamics, oxygen saturation or AMS development.

Practical Tips for Working as an Expedition Doctor on High-Altitude Expeditions

Brants, Anne, and Tracee Metcalfe. Practical tips for working as an expedition doctor on high-altitude expeditions. High Alt Med Biol. 18:193-198, 2017.-With the explosion of adventure travel over the past decade, there has been a concurrent increase in mountaineering expeditions to extreme elevations, including many of the 8000-m peaks. This trend has created an increased demand for qualified expedition doctors to provide specialized medical advice and care to climbers and expedition staff. This review is intended to help physicians prepare for work on such expeditions. The authors rely heavily on their own experience and discuss the types of work available on high-altitude expeditions; how to identify a safe and reputable guiding company; personal and medical preparation; priorities in selecting or building an appropriate medical kit; and medical conditions commonly encountered on expeditions. The review concludes by considering ethical dilemmas and other difficult issues unique to this work.

A trekker in Nepal with painful skin blisters

The authors present a case of a 27-year-old woman trekker with painful, slightly itchy eruptions on the dorsum of both hands for 5 days. On examination, she had a papulovesicular rash with some haemorrhagic vesicles over the dorsum of her hands and thumbs.