Wilderness & Environmental Medicine

Limited evidence exists to guide travelers about blood pressure (BP) changes at high altitude (HA). Our primary objective compared 24-h ambulatory BP at low altitude (LA) vs HA in a cohort of tourists. Exploratory analyses compared results by sex and history of underlying hypertension.

This prospective observational cohort study measured ambulatory BP with Welch-Allyn ABPM 6100 monitors at LA (<1000 m) and HA (median 2751 m). Measurements included heart rate/BP every 30 min while awake and hourly overnight, BP≥180/100 mm Hg, sleep quality, and Lake Louise score (acute mountain sickness).

Among 33 participants (median age 61 y, 17 with hypertension, 12 on BP medication), 25 completed LA and HA measurements. Average 24-h mean arterial pressure (MAP) increased at HA by 6 mm Hg (95% CI, 2–10 mm Hg; P=0.04). When analyzed by the presence of preexisting hypertension, 24-h MAP was similar between LA and HA in those with underlying hypertension (mean difference, 4 mm Hg; 95% CI, –4 to 11 mm Hg; P=0.3) but rose at HA in those without (mean difference, 9 mm Hg; 95% CI, 5–14 mm Hg; P=0.001). At HA, 24-h MAP was similar in both groups (mean difference, 9 mm Hg; 95% CI, 0–19 mm Hg; P=0.05). Results did not differ by sex. Severe-range BP was common in all groups and asymptomatic.

Among this tourist cohort, we observed an increase in average 24-h MAP at HA. Altitude-related changes in BP varied greatly between individuals. This variation was related in part to underlying hypertension but not sex. Our data suggest that BP changes are not of clinical concern in HA travelers.

Accidental hypothermia increases mortality in patients with traumatic injury, making hypothermia management essential in prehospital trauma care. Chemical heat blankets are commonly used for this purpose. These blankets require time to get warm, with agitation often used to accelerate the exothermic reaction. Many search and rescue teams use chemical heat blankets, but optimal activation of the blankets remains uncertain. This study investigated how varying oxygen exposure durations affect the thermal performance of these blankets to guide their optimal use in search and rescue scenarios.

In room-temperature conditions, a full-body manikin was wrapped in a standardized hypothermia model, including a chemical heat blanket, and evaluated under 3 conditions: 1) no shaking, 2) shaking for 2 min, and 3) shaking for 15 min before wrapping. Thermometers were placed inside the heating panel pockets and secured in place with tape to ensure consistent measurements. Temperature data were collected over 6 h, and each scenario was performed 4 times.

Blankets shaken for 2 min achieved higher initial temperatures than those not shaken, with a significant difference sustained for 88 min. Shaking for 15 min resulted in higher initial temperatures than 2-min shaking, with no long-term difference. All scenarios converged to the same temperature (36°C) after 6 h.

Shaking the blanket for 2 min significantly improved early heating performance, whereas longer shaking offered minimal benefit. These findings suggest that short preparation time may be adequate in optimizing thermal delivery and reducing the time to treatment for patients with prehospital accidental hypothermia.

Climbing chalk is widely used by rock climbers and athletes to improve grip. It has been observed that climbers sometimes apply magnesium carbonate chalk to small wounds to stop bleeding, suggesting that climbing chalk may exhibit hemostatic properties useful for small cuts and scrapes. This study aimed to investigate and compare the effects of different types of climbing chalk on prothrombin time (PT) and activated partial thromboplastin time (aPTT).

Three types of climbing chalk were randomly selected for comparative analysis of hemostatic properties, with talcum powder used as a negative control. PT and aPTT testing were conducted on normal plasma samples containing varying concentrations of climbing chalk (from 0.125 mg/mL to 4 mg/mL). Statistical analyses of the results were performed using two-tailed t-tests, Welch's analysis of variance (ANOVA), and Games-Howell post-hoc analysis.

Results indicated that climbing chalk had no significant effect on PT but did significantly reduce aPTT compared to the negative control. Additional analyses revealed significant differences in aPTT results between different types of chalk and between higher and lower concentrations of chalk.

Magnesium carbonate-based climbing chalks appear to have a procoagulant effect on hemostasis, likely by affecting the intrinsic pathway of the coagulation cascade. While further research is needed to better understand its coagulative properties, climbing chalk shows potential as a hemostatic agent for minor wounds in wilderness medicine.

The Texas coral snake, Micrurus tener, is one of three elapid species native to the continental United States. The purpose of the study was to describe the clinical features of their envenomation.

We reviewed all human coral snake bites reported to the Texas Poison Center Network between January 2000 and December 2023. We excluded informational calls and cases in which the snake responsible for the bite was not confirmed as M. tener. Finally, we excluded bite victims who did not seek medical attention and those for whom no clinical information was available. The data collected included patient demographics, the county in which the patient was treated, clinical features, and treatment.

There were 501 human bites. In 472 (94.2%) cases, symptoms were limited to pain and paresthesias. Systemic toxicity, for example, weakness, dysphagia, and ptosis, was observed in 18 (3.6%) patients. Eleven (2.2%) patients had no clinical findings. Antivenom was administered in 126 (25.1%) cases. Antivenom use decreased over time; in the 5-year period from 2000–2007, antivenom was administered to 74 (55.6%) patients. Conversely, only 8 (4.1%) of patients from 2016–2023 received antivenom. Systemic findings were observed in 13 (6.5%) cases in Northeast and Central Texas compared to 5 (1.6%) in Southeast and South Texas.

Micrurus tener envenomations were characterized primarily by pain and paresthesias. Additional systemic findings may be observed, particularly in Northeast and Central Texas. Antivenom was administered to a minority of Texas coral snake envenomation victims.

Mount Aconcagua (6961 m) is the highest peak in the Americas, and thousands of climbers attempt to climb it annually. This study aimed to characterize recent climber mortality on Aconcagua to aid in future safety efforts.

Climber fatalities from Aconcagua for the 10 most recent climbing seasons (2013–2024) were retrospectively reviewed.

Over the study period, 21 of 29,397 climbers died, yielding a fatality rate of 0.071% (0.71 per 1000). Most fatalities occurred at over 6000 m (90%) and were of unspecified medical cause (71%). Trauma represented 19% of deaths. Climbers older than 50 y were more than 5 times more likely to die on Aconcagua than those younger than 50 y (odds ratio = 5.11). Climbers from the United States were found to have a higher incidence of fatality (odds ratio = 2.56). Compared with 2001-2012, fatalities from 2013-2024 occurred with similar incidence overall but more frequently at elevations over 6000 m, and victims were older and more frequently from North America.

Despite the fatality rate on Aconcagua remaining unchanged at 0.071% during 2013-2024, the percentages of deaths at over 6000 m and from medical causes increased from a prior study. Climbers older than 50 y and climbers from the United States were found to be at higher risk of death on Aconcagua. This information can provide a basis for education to reduce future mortality.

Cold-water immersion is the standard of care for treating exertional heatstroke (EHS). The Polar Life Pod (PLP; Polar Products Inc, Stow, OH), a body-bag-like device, is a novel, portable cold-water immersion device with excellent cooling rates (>0.18°C·min^–1) when 151 to 208 L of water are used to treat hyperthermia. Unfortunately, these water volumes are not always available to treat EHS (eg, wilderness firefighting). Little research has examined whether the PLP with small water volumes meets expert recommendations for acceptable (ie, 0.08–0.15°C·min^–1) or ideal cooling rates (ie, >0.16°C·min^–1).

Thirty-two subjects (20 males and 12 females aged 21±2 y with a mass of 72.2±11.0 kg and a height of 170.4±7.2 cm) were assigned to 1 of 4 groups in this matched-pairs laboratory study. Participants wore a uniform and 9.5-kg rucksack and marched in the heat (wet-bulb globe temperature=26.1±0.1°C) until their rectal temperature (T_REC) was 39.5°C. Then they removed the uniform and sat in the heat (0 L) or lay in a PLP filled with 19, 38, or 76 L of ∼8°C water until T_REC was 38°C.

By design, all groups had comparable physical characteristics: body fat percentage (P=0.39), lean body mass (P=0.86), fat mass (P=0.13), body surface area (P=0.36), body surface area–lean body mass ratio (P=0.98), and body mass index (P=0.63). Subjects exercised for similar durations (P=0.66), and pre-immersion water temperatures were consistent between groups (P>0.05). T_REC cooling rates differed (0 L=0.03±0.01°C·min^–1, 19 L=0.13±0.08°C·min^–1, 38 L=0.10±0.03°C·min^–1, and 76 L=0.17±0.09°C·min^–1; P=0.002). No cooling-rate differences occurred between 19, 38, and 76 L (P<0.05).

PLP with 76 L met expert recommendations for ideal cooling rates; 19 and 38 L demonstrated acceptable cooling rates. PLP may help save lives from EHS when water access is limited.

Ski patrollers face unique occupational risks and may be exposed to traumatic events. This study aimed to determine the relationship between traumatic event exposures and wellbeing among a cohort of U.S. ski patrollers.

A non-experimental, descriptive, longitudinal design was followed to complete a pilot study. An online survey was employed with repeated measures (1, 2, & 3 months). Participants were conveniently sampled from one ski resort in the Western United States. This study was informed by the stress continuum model.

A total of 29 participants completed at least one follow-up survey and were included as the analytic sample. Participants were primarily White (n = 27, 93.10%), non-Hispanic or Latino (n = 27, 93.10%), and male (n = 19, 65.52%), aged 39.07 on average. Three-quarters of participants reported exposure to traumatic events at Survey 1 (n = 22, 75.86%), and the frequency ranged from 1 to 20 events. Increased frequency of traumatic events by each one event was significantly related to decreased wellbeing levels over 3 months (β = −0.0253, p < .0001, 95% CI: [−0.0364, −0.0141]), after controlling for age, sex, race, ethnicity, marital status, and working hours. When included as an interaction term, resilience was found to buffer the negative effect of traumatic event exposure on wellbeing (β = −0.0068, p < .0001, 95% CI: [−0.0099, −0.0038]).

Findings underscore the need for additional research to identify the most effective ways to support the wellbeing and resilience of ski patrollers.

Avalanches and tree-wells (TW) are causes of snow immersion death in skiers and snowboarders. TW burials may have different victim physiology profiles and rescue considerations than avalanche-related burials due to snow density, burial position, and compensatory physiologic responses. This study aimed to compare the physiological responses between avalanche and TW burials through a prospective controlled trial of simulated avalanche burial to simulated TW burial.

Eleven volunteers participated in two paired 60-min snow burials: Avalanche and TW simulations, controlling for position and snowpack densities. We monitored core temperature, respiratory rate, minute ventilation, end-tidal carbon dioxide, oxygen saturation, partial pressure of inspired carbon dioxide, and heart rate.

The average cooling rate for the avalanche simulation was −0.017(Δ°C/min) versus −0.012(Δ°C/min) for the TW simulation (p = 0.014*), 1.42 times faster cooling rate than TW burial. SpO2 decreased 10.9 times faster on average in TW burial than in avalanche conditions when normalized by burial time as a rate (avalanche −0.011 vs TW −0.12 (Δ%/min), p = 0.033*). More participants requested early study termination in the TW scenario.

Simulated TW burial resulted in a statistically significant slower rate of core temperature cooling and earlier hypoxemia. Inverted body position in TW burials may lead to increased physiologic distress and contribute to earlier hypoxia. These findings may have important implications for search and rescue as well as resuscitation efforts for snow burial victims.