Accidental hypothermia in recreational activities in the mountains: A narrative review.

The popularity of recreational activities in the mountains worldwide has led to an increase in the total number of persons exposed to cold and extreme environments through recreation. There is little conclusive evidence about the risk of hypothermia for specific activities or populations, nor is it clear which activities are represented in the literature. This is a non-systematic review of accidental hypothermia in different recreational activities in the mountains, with a specific focus on outdoor or winter activities that potentially involve cold exposure. Cases of hypothermia have been reported in the literature in mountaineering, trekking, hiking, skiing, activities performed in the backcountry, ultra-endurance events, and databases from search and rescue services that include various types of recreation. Of these activities, hypothermia as a primary illness occurs most commonly during mountaineering in the highest elevation areas in the world and during recreation practiced in more northern or remote areas. Hypothermia in skiers, snowboarders, and glacier-based activities is most often associated with accidents occurring off-piste or in the backcountry (crevasse, avalanche). Organizers of outdoor events also have a role in reducing the incidence of hypothermia through medical screening and other preparedness measures. More complete collection and reporting of data on mild hypothermia and temperature measurement would improve our understanding of the incidence of hypothermia in outdoor recreation in future.

Risk of Avalanche Involvement in Winter Backcountry Recreation: The Advantage of Small Groups.

OBJECTIVE: Avalanches are the primary hazard for winter backcountry recreationists and cause numerous deaths and injuries annually. Although recreationists usually travel in groups, there is little empirical knowledge on group-related risk factors. This study aims to explore the relative risk of avalanche accidents with respect to group size and to discuss underlying reasons for different risk levels. METHODS: We compared backcountry usage data in regions in Switzerland and Italy with avalanche accident data in these regions. RESULTS: We found higher avalanche risk for groups of 4 or more people and lower risk for people traveling alone and in groups of 2. The relative risk of group size 4, 5, and 6 was higher compared with the reference group size of 2 in the Swiss and Italian dataset. The relative risk for people traveling alone was not significantly different compared with the reference group size of 2 in the Italian dataset but was lower in the Swiss dataset. CONCLUSIONS: These findings are in accordance with avalanche safety recommendations regarding the higher risk of large groups but not regarding lower risks of people traveling alone in avalanche terrain, which is not recommended and requires great caution. Further studies on backcountry usage are necessary to improve our understanding of human behavior and risk factors. New techniques (eg, video monitoring) may be useful for acquiring reliable data on backcountry usage.

Avalanche Survival After Rescue With the RECCO Rescue System: A Case Report.

We report a case of survival of a completely buried avalanche victim after being located with the radar-based RECCO Rescue System. In the winter of 2015, 2 off-piste skiers were completely buried in an avalanche near the secured ski area in Baqueira Beret, Spain. The first victim was located with the RECCO Rescue System in less than 35 minutes and was alive and conscious at extrication. This system emits radio waves and requires a specific reflector. It is a portable device that is used by more than 600 rescue organizations worldwide, especially in secured ski areas. The device should be brought to the avalanche site together with electronic avalanche transceivers, a probing team, and avalanche dogs. In the hands of experienced professionals, the device may allow rapid location of victims not carrying an electronic avalanche transceiver. Although it is not the first successful extrication of a victim with the RECCO Rescue System, it is the first case published in the medical literature and is intended to encourage data collection and to increase our understanding of the effectiveness of this device in avalanche rescue.

Search and rescue response to a large-scale rockfall disaster.

OBJECTIVE: To describe the prehospital management and safety of search and rescue (SAR) teams involved in a large-scale rockfall disaster and monitor the acute and chronic health effects on personnel with severe dolomitic dust exposure. METHODS: SAR personnel underwent on-site medical screening and lung function testing 3 months and 3 years after the event. RESULTS: The emergency dispatch center was responsible for central coordination of resources. One hundred fifty SAR members from multidisciplinary air- and ground-based teams as well as geotechnical experts were dispatched to a provisionary operation center. Acute exposure to dolomite dust with detectable silicon and magnesium concentrations was not associated with (sub)acute or chronic sequelae or a clinically significant impairment in lung function in exposed personnel. CONCLUSIONS: The risk for personnel involved in mountain SAR operations is rarely reported and not easily investigated or quantified. This case exemplifies the importance of a multiskilled team and additional considerations for prehospital management during natural hazard events. Safety plans should include compulsory protective measures and medical monitoring of personnel.

Defibrillation in rural areas.

AIM OF THE STUDY: Automated external defibrillation (AED) and public access defibrillation (PAD) have become cornerstones in the chain of survival in modern cardiopulmonary resuscitation. Most studies of AED and PAD have been performed in urban areas, and evidence is scarce for sparsely populated rural areas. The aim of this review was to review the literature and discuss treatment strategies for out-of-hospital cardiac arrest in rural areas. METHODS: A Medline search was performed with the keywords automated external defibrillation (617 hits), public access defibrillation (256), and automated external defibrillator public (542). Of these 1415 abstracts and additional articles found by manually searching references, 92 articles were included in this nonsystematic review. RESULTS: Early defibrillation is crucial for survival with good neurological outcome after cardiac arrest. Rapid defibrillation can be a challenge in sparsely populated and remote areas, where the incidence of cardiac arrest is low and rescuer response times can be long. The few studies performed in rural areas showed that the introduction of AED programs based on a 2-tier emergency medical system, consisting of Basic Life Support and Advanced Life Support teams, resulted in a decrease in collapse-to-defibrillation times and better survival of patients with out-of-hospital cardiac arrest. CONCLUSIONS: In rural areas, introducing AED programs and a 2-tier emergency medical system may increase survival of out-of-hospital cardiac arrest patients. More studies on AED and PAD in rural areas are required.

Changes in Factors Regulating Serum Sodium Homeostasis During Two Ultra-Endurance Mountain Races of Different Distances: 69km vs. 121km.

Overdrinking and non-osmotic arginine vasopressin release are the main risk factors for exercise-associated hyponatremia (EAH) in ultra-marathon events. However, particularly during ultra-marathon running in mountainous regions, eccentric exercise and hypoxia, which have been shown to modulate inflammation, hormones regulating fluid homeostasis (hypoxia), and oxidative stress, could contribute to serum sodium changes in a dose-dependent manner. To the best of our knowledge, the contribution of these factors, the extent of which depends on the duration and geographical location of the race, has not been well studied. Twelve male participants (11 finishers) of the short (69km, 4,260m elevation-gain) and 15 male participants (seven finishers) of the long (121km, 7,554m elevation-gain) single-stage Südtirol Ultra Sky-Race took part in this observational field study. Venous blood was drawn immediately before and after the race. Analyses included serum sodium concentration, copeptin (a stable marker for vasopressin), markers of inflammation, muscle damage and oxidative stress. Heart rate was measured during the race and race time was obtained from the race office. During the short and the long competition two and one finishers, respectively showed serum sodium concentrations >145mmol/L. During the long competition, one athlete showed serum sodium concentrations <135mmol/L. Only during the short competition percent changes in serum sodium concentrations of the finishers were related to percent changes in body mass (r=-0.812, p=0.002), total time (r=-0.608, p=0.047) and training impulse (TRIMP) (r=-0.653, p=0.030). Data show a curvilinear (quadratic) relationship between percent changes in serum sodium concentration and body mass with race time when including all runners (short, long, finishers and non-finishers). The observed prevalence of hypo- and hypernatremia is comparable to literature reports, as is the relationship between serum sodium changes and race time, race intensity and body mass changes of the finishers of the short race. The curvilinear relationship indicates that there might be a turning point of changes in serum sodium and body mass changes after a race time of approximately 20h. Since the turning point is represented mainly by non-finishers, regardless of race duration slight decrease in body mass and a slight increase in serum sodium concentration should be targeted to complete the race. Drinking to the dictate of thirst seems an adequate approach to achieve this goal.

Performance Determinants in Short (68 km) and Long (121 km) Mountain Ultra-Marathon Races.

BACKGROUND: Standard performance parameters measured during a laboratory test have been shown to be related to mountain ultra-marathon performance up to a competition length of 75 km. It is not known if a similar relationship exists for longer races. OBJECTIVE: This study aimed to investigate the association between laboratory-based performance parameters and performance times in a short (68 km) and a long (121 km) mountain ultra-marathon. MATERIALS AND METHODS: Eleven male finishers of the short race and seven male finishers of the long race were investigated. Participants performed an incremental exercise test to exhaustion in the 2 weeks prior to the event. During the event, the heart rate was monitored and finishing times were registered. RESULTS: The maximal oxygen consumption and the oxygen uptake at the ventilatory thresholds 1 and 2 were related to performance time during the short run (~12h; r = -0.764 up to r = -0.782; p < 0.05), but there was no correlation during the long race (~28h; r = -0.107 to 0.357; p > 0.05). CONCLUSIONS: This study shows that physical fitness parameters established in a laboratory setting determine competition completion times in ultra-mountain marathon events lasting for ~12 h. During longer races, i. e. ~28 h, other factors not established in the present investigation, such as experience, race strategy, coping with pain and fatigue resistance, may be important for performance.

Total Body Water Dynamics Estimated with Bioelectrical Impedance Vector Analysis and B-Type Natriuretic Peptide After Exposure to Hypobaric Hypoxia: A Field Study.

Strapazzon, Giacomo, Matiram Pun, Tomas Dal Cappello, Emily Procter, Piergiorgio Lochner, Hermann Brugger, and Antonio Piccoli. Total body water dynamics estimated with bioelectrical impedance vector analysis and B-type natriuretic peptide after exposure to hypobaric hypoxia: A field study. High Alt Med Biol. 18:384-391, 2017.-The relationship between total body water (TBW) dynamics and N-terminal pro-B-type natriuretic peptide (NT-proBNP), a stable metabolite of B-type natriuretic peptide, during acute high altitude exposure is not known. To investigate this, we transported 19 healthy lowland subjects to 3830 m with a helicopter after baseline measurements (262 m). The physiological measurements and clinical assessments were taken at 9, 24, 48, and 72 hours and on the eighth day of altitude exposure. A bioelectrical impedance vector analysis (BIVA) from height corrected Resistance-Reactance (R-Xc graph) was used to estimate TBW status. NT-proBNP was measured from venous blood samples. The changes in impedance vector were lengthened at 9 (p = 0.011), 48 (p = 0.033), and 72 hours (p = 0.015) indicating dehydration compared to baseline. However, there was no dehydration at 24 hours (p > 0.05) from the baseline and the subjects trended to get euhydrated from 9 to 24 hours (p = 0.097). The maximum percent changes in vector length from the baseline were within 10%-15%. There was a significant increase of natural logarithm (ln)(NT-proBNP) after ascent with a peak at 24 hours, although similarly to BIVA values, ln(NT-proBNP) returned to baseline after 8 days of altitude exposure. The changes in impedance vector length were not correlated with the changes in ln(NT-proBNP) (r = -0.101, p = 0.656). In conclusion, the dehydration at high altitude as reflected by 10%-15% vector lengthening falls within "appropriate dehydration" in healthy lowland subjects. NT-proBNP does not simply reflect the TBW status during acute high altitude exposure and needs further investigation.

Prehospital management and outcome of avalanche patients with out-of-hospital cardiac arrest: a retrospective study in Tyrol, Austria.

AIM: The aim of this study is to describe the prehospital management and outcome of avalanche patients with out-of-hospital cardiac arrest in Tyrol, Austria, for the first time since the introduction of international guidelines in 1996. PATIENTS AND METHODS: This study involved a retrospective analysis of all avalanche accidents involving out-of-hospital cardiac arrest between 1996 and 2009 in Tyrol, Austria. RESULTS: A total of 170 completely buried avalanche patients were included. Twenty-eight victims were declared dead at the scene. Of 34 patients with short burial, cardiopulmonary resuscitation (CPR) was performed in 27 (79%); 15 of these patients (56%) were transported to hospital with ongoing CPR and four patients were rewarmed with extracorporeal circulation; no patient survived. Of 108 patients with long burial, 49 patients had patent or unknown airway status; CPR was performed in 25 of these patients (51%) and 14 patients (29%) were transported to hospital. Four patients were rewarmed, but only one patient with witnessed cardiac arrest survived. Since the introduction of guidelines in 1996, there has been a marginally significant increase in the rate of documenting airway assessment, but no change in documenting the duration of burial or CPR. CONCLUSION: CPR is continued to hospital admission in patients with short burial and asphyxial cardiac arrest, but withheld or terminated at the scene in patients with long burial and possible hypothermic cardiac arrest. Insufficient transfer of information from the accident site to the hospital may partially explain the poor outcome of avalanche victims with out-of-hospital cardiac arrest treated with emergency cardiac care.

Burial duration, depth and air pocket explain avalanche survival patterns in Austria and Switzerland.

AIM: To calculate the first Austrian avalanche survival curve and update a Swiss survival curve to explore survival patterns in the Alps. METHODS: Avalanche accidents occurring between 2005/06 and 2012/13 in Austria and Switzerland were collected. Completely buried victims (i.e. burial of the head and chest) in open terrain with known outcome (survived or not survived) were included in the analysis. Extrication and survival curves were calculated using the Turnbull algorithm, as in previous studies. RESULTS: 633 of the 796 completely buried victims were included (Austria n=333, Switzerland n=300). Overall survival was 56% (Austria 59%; Switzerland 52%; p=0.065). Time to extrication was shorter in Austria for victims buried ≤60min (p<0.001). The survival curves were similar and showed a rapid initial drop in survival probability and a second drop to 25-28% survival probability after burial duration of ca. 35min, where an inflection point exists and the curve levels off. In a logistic regression analysis, both duration of burial and burial depth had an independent effect on survival. Victims with an air pocket were more likely to survive, especially if buried >15min. CONCLUSION: The survival curves resembled those previously published and support the idea that underlying survival patterns are reproducible. The results are in accordance with current recommendations for management of avalanche victims and serve as a reminder that expedient companion rescue within a few minutes is critical for survival. An air pocket was shown to be a positive prognostic factor for survival.

Oxidative stress response to acute hypobaric hypoxia and its association with indirect measurement of increased intracranial pressure: a field study.

High altitude is the most intriguing natural laboratory to study human physiological response to hypoxic conditions. In this study, we investigated changes in reactive oxygen species (ROS) and oxidative stress biomarkers during exposure to hypobaric hypoxia in 16 lowlanders. Moreover, we looked at the potential relationship between ROS related cellular damage and optic nerve sheath diameter (ONSD) as an indirect measurement of intracranial pressure. Baseline measurement of clinical signs and symptoms, biological samples and ultrasonography were assessed at 262 m and after passive ascent to 3830 m (9, 24 and 72 h). After 24 h the imbalance between ROS production (+141%) and scavenging (-41%) reflected an increase in oxidative stress related damage of 50-85%. ONSD concurrently increased, but regression analysis did not infer a causal relationship between oxidative stress biomarkers and changes in ONSD. These results provide new insight regarding ROS homeostasis and potential pathophysiological mechanisms of acute exposure to hypobaric hypoxia, plus other disease states associated with oxidative-stress damage as a result of tissue hypoxia.

Apparent Cooling Rate of 7°C per Hour in an Avalanche Victim.

Avalanche victims can become hypothermic within 35 minutes of snow burial. However, reported cooling rates for avalanche victims are highly variable and it is poorly understood how much cooling is influenced by general factors (body composition, clothing, ambient conditions, duration of burial, and metabolism), unknown inter-individual factors or other phenomena (e.g., afterdrop). We report an apparent cooling rate of ∼7°C in ∼60 minutes in a healthy backcountry skier who was rewarmed with forced air and warm fluids and was discharged after 2 weeks without neurological sequelae.

Influence of low ambient temperature on epitympanic temperature measurement: a prospective randomized clinical study.

BACKGROUND: Epitympanic temperature (Tty) measured with thermistor probes correlates with core body temperature (Tcore), but the reliability of measurements at low ambient temperature is unknown. The aim of this study was to determine if commercially-available thermistor-based Tty reflects Tcore in low ambient temperature and if Tty is influenced by insulation of the ear. METHODS: Thirty-one participants (two females) were exposed to room (23.2 ± 0.4 °C) and low (-18.7 ± 1.0 °C) ambient temperature for 10 min using a randomized cross-over design. Tty was measured using an epitympanic probe (M1024233, GE Healthcare Finland Oy) and oesophageal temperature (Tes) with an oesophageal probe (M1024229, GE Healthcare Finland Oy) inserted into the lower third of the oesophagus. Ten participants wore ear protectors (Arton 2200, Emil Lux GmbH & Co. KG, Wermelskirchen, Switzerland) to insulate the ear from ambient air. RESULTS: During exposure to room temperature, mean Tty increased from 33.4 ± 1.5 to 34.2 ± 0.8 °C without insulation of the ear and from 35.0 ± 0.8 to 35.5 ± 0.7 °C with insulation. During exposure to low ambient temperature, mean Tty decreased from 32.4 ± 1.6 to 28.5 ± 2.0 °C without insulation and from 35.6 ± 0.6 to 35.2 ± 0.9 °C with insulation. The difference between Tty and Tes at low ambient temperature was reduced by 82% (from 7.2 to 1.3 °C) with insulation of the ear. CONCLUSIONS: Epitympanic temperature measurements are influenced by ambient temperature and deviate from Tes at room and low ambient temperature. Insulating the ear with ear protectors markedly reduced the difference between Tty and Tes and improved the stability of measurements. The use of models to correct Tty may be possible, but results should be validated in larger studies.

Factors associated with B-lines after exposure to hypobaric hypoxia.

AIMS: Increased extravascular lung water (EVLW) is seen as B-lines on chest ultrasonography. In lowlanders ascending to altitude the time course, relationship with the patient's clinical status and factors affecting B-lines are still unclear. The aim was to monitor B-lines, clinical status and N-terminal B-type natriuretic peptide (NT-proBNP) during exposure to high altitude. METHODS AND RESULTS: Chest ultrasonography, blood samples, cardiovascular parameters, and signs and symptoms of high altitude pulmonary oedema (HAPE) were prospectively assessed in 19 participants at baseline and after ascent to 3830 m (9, 24, 48, 72 h, and 8 days) by blinded investigators. Potential confounding factors (e.g. altitude variations, physical effort) were minimized. Generalized estimating equations were used to analyse factors associated with B-lines. B-lines changed with exposure to altitude (P = 0.006) in a parabolic-like pattern within the first 72 h; 10 of 18 participants (55.6%) had >5 B-lines at 24 h. B-lines were correlated with the number of signs and symptoms (partial coefficient = 0.372, P = 0.001). B-lines were associated with time (P = 0.038), sex (P = 0.013), and SpO2 (P = 0.042), but not with NT-proBNP (P = 0.546). The participant with a clinical diagnosis of HAPE had 23 B-lines. CONCLUSION: B-lines during exposure to altitude seem to reflect the individual response to hypobaric hypoxia and represent clinically relevant alterations at high altitude, also in patients with HAPE. Similar to previous studies, our results support a non-cardiogenic aetiology of B-lines.

Pre-hospital core temperature measurement in accidental and therapeutic hypothermia.

Core temperature (T core) measurement is the only diagnostic tool to accurately assess the severity of hypothermia. International recommendations for management of accidental hypothermia encourage T core measurement for triage, treatment, and transport decisions, but they also recognize that lack of equipment may be a limiting factor, particularly in the field. The aim of this nonsystematic review is to highlight the importance of field measurement of T core and to provide practical guidance for clinicians on pre-hospital temperature measurement in accidental and therapeutic hypothermia. Clinicians should recognize the difference between alternative measurement locations and available thermometers, tailoring their decision to the purpose of the measurement (i.e., intermittent vs. continual measurement), and the impact on management decisions. The importance of T core measurement in therapeutic hypothermia protocols during early cooling and monitoring of target temperature is discussed.

Basic life support trained nurses ventilate more efficiently with laryngeal mask supreme than with facemask or laryngeal tube suction-disposable--a prospective, randomized clinical trial.

OBJECTIVE: In some emergency situations resuscitation and ventilation may have to be performed by basic life support trained personnel, especially in rural areas where arrival of advanced life support teams can be delayed. The use of advanced airway devices such as endotracheal intubation has been deemphasized for basically-trained personnel, but it is unclear whether supraglottic airway devices are advisable over traditional mask-ventilation. METHODS: In this prospective, randomized clinical single-centre trial we compared airway management and ventilation performed by nurses using facemask, laryngeal mask Supreme (LMA-S) and laryngeal tube suction-disposable (LTS-D). Basic life support trained nurses (n=20) received one-hour practical training with each device. ASA 1-2 patients scheduled for elective surgery were included (n=150). After induction of anaesthesia and neuromuscular block nurses had two 90-second attempts to manage the airway and ventilate the patient with volume-controlled ventilation. RESULTS: Ventilation failed in 34% of patients with facemask, 2% with LMA-S and 22% with LTS-D (P<0.001). In patients who could be ventilated successfully mean tidal volume was 240±210 ml with facemask, 470±120 ml with LMA-S and 470±140 ml with LTS-D (P<0.001). Leak pressure was lower with LMA-S (23.3±10.8 cm H2O, 95% CI 20.2-26.4) than with LTS-D (28.9±13.9 cm·H2O, 95% CI 24.4-33.4; P=0.047). CONCLUSIONS: After one hour of introductory training, nurses were able to use LMA-S more effectively than facemask and LTS-D. High ventilation failure rates with facemask and LTS-D may indicate that additional training is required to perform airway management adequately with these devices. High-level trials are needed to confirm these results in cardiac arrest patients.

Factors associated with optic nerve sheath diameter during exposure to hypobaric hypoxia.

OBJECTIVE: To monitor the changes in optic nerve sheath diameter (ONSD) induced by acute exposure to hypobaric hypoxia and to investigate factors associated with these changes, including development of acute mountain sickness. METHODS: In this cohort study, neurologic signs and symptoms, cardiovascular parameters, and ultrasonography of ONSD were prospectively assessed in 19 healthy lowlanders at baseline and after ascent to 3,830 m (3 hours, 9 hours, 24 hours, 48 hours, 72 hours, and 8 days) by blinded investigators. Potential confounding factors (e.g., altitude variations, physical effort) were minimized. A multivariate analysis of factors associated with ONSD was performed by means of generalized estimating equations. RESULTS: ONSD increased with exposure to altitude in all participants (p < 0.001). The increase between 9 and 24 hours was larger in patients who developed acute mountain sickness (p = 0.001). There was no influence of sex, oxygen saturation, or acclimatization on ONSD. CONCLUSION: Both physiologic and pathologic responses to hypobaric hypoxia were independently associated with changes in ONSD. Studies on a larger cohort, at a range of altitudes, and with baseline neuroimaging techniques are necessary to further understand the clinical significance of increased ONSD during exposure to hypobaric hypoxia.