PRACTICING MEDICINE AT EXTREME HIGH ALTITUDE: Statistics, heuristics and logistics
Emily E. Johnston, MD, FACEP, DiMM WMS Winter Conference 2021 We will cover:
The most commonly encountered medical problems at extreme altitude A brief review of pertinent pathophysiology Extreme altitude statistics (as available) Decision making and practical logistics Heuristics
A heuristic technique is any approach to problem solving or self-discovery that employs a practical method that is not guaranteed to be optimal, perfect, or rational, but is nevertheless sufficient for reaching an immediate, short-term goal or approximation. Medical problems at extreme altitude
Cold injury Pre-existing medical conditions AMS/HAPE/HACE Exhaustion, Trauma dehydration Stress and anxiety Respiratory GI Skin Sudden cardiac Eyes death Cold injury – Hypothermia
MS/LOC, shivering, performance, CV(blood pressure/rhythm) never for SEALs . . . ~32 C/89.6 F – exogenous heat needed ~30 C/95 F – cardiac changes WMS guidelines Figure 3
Wilderness & Environmental Medicine 2019 30S47-S69DOI: (10.1016/j.wem.2019.10.002) Copyright © 2019 Marketing EDGE.org. Cold injury – Hypothermia
31 yo OTW healthy male s/p ascent to 8848m/29,000+’, shortroping/lowering client from the yellow band attaches personal gear to ice screw,eventually taps out due to exhaustion and descends to 7200’/22,000’ alone. discovered hours later by teammate in tent at C3, AMS, not shivering. pt receives meds, rewarmed for hours. ultimately descends under his own power. Cold injury – Frostbite
30-35% of climbers at extreme altitude mostly face, fingers, toes. often delayed diagnosis due to: hypoxia sleep deprivation distraction Cold injury – Frostbite
“I knew something was amiss with my left foot before reaching the summit - chose to ignore it and do as everyone else does and continue on up.”
“by the time I finished messing around, achieving nothing, my hands were a tad chilly!”
“Didn't think a big deal and made it back to C2 exhausted.”
“Prior to heading to Everest I bought a set of heated (foot)warmers. . . carried them up to the South Col, still not using them. I didn't make the smart decision to actually connect them up. I left for the summit.... still without them installed.” Cold injury – Frostbite
Frostbite management a variety of grading systems to rewarm or not? blister management oxygen Cold injury – Frostbite Day 3
Day 2
Day 6 Day 1 Cold injury – Frostbite
Day 79
Day 10 Day 16 Day 83
Day 139 AMS/HAPE/HACE
AMS – Acute Mountain Sickness don’t worry, it’s just brain swelling 15-40%+ of CO skiers (2500-4000m/8100-13,000’) 40% of Denali climbers about 70% above 3000m/10,000’ higher for those flown directly to 4200m/14,000’ decreased incidence in > 50 yo AMS/HAPE/HACE
AMS diagnosis quandry exhaustion, dehydration, CO, stress, Covid-19 vitals/exam are not helpful oxygen? acetazolamide? ondansetron? graded trial of treatment depending on timeframe and resources AMS/HAPE/HACE
HAPE – High Altitude Pulmonary Edema non-cardiogenic pulmonary edema hypoxic pulmonary vasoconstriction increased pressure risks: anything increasing risk of pulmonary hypertension prior HAPE, genetic predisposition pulmonary infection exertion and cold temps unusual below 3000m/9850’ AMS/HAPE/HACE
HAPE 2% of Denali climbers 6190m/20,320’ 16% of Kilimanjaro climbers 5895m/19341’ 15% of people flown directly to 5500m/18,000’ 60% recurrence rate at 4500m/14,700’ 4500m – 0.2-6% 5500m – 2-15% AMS/HAPE/HACE
HAPE SOB, cough is common at altitude 38% of medical pts at Everest ER - how do you know? oxygen is diagnostic and therapeutic orthopnea, dyspnea at rest, decreased exercise capacity frothy sputum is for Hollywood full court press ASAP descent and O2 and nifedipine, Gamow bag as needed AMS/HAPE/HACE
HACE – High Altitude Cerebral Edema the vast majority with HACE have HAPE HAPE increases intra-thoracic pressure which contributes to cerebral venous congestion. on continuum with AMS vasogenic edema death by herniation AMS/HAPE/HACE
HACE 0.5-1+% of travelers to high altitude 3-4% of AMS patients progress to HACE 13-20% of those with HAPE unusual below 3000m/9800ft mean altitude of onset 4730m/15,500ft Trauma
Everest ER 14% trauma you fall off the mountain you fall into the mountain the mountain falls on you rockfall/people/objects avalanche/icefall extreme weather Stress and anxiety
exacerbate other disorders precipitate formal and informal evacuations self-medication is not uncommon daily plan, structured time frequent one-on-one interactions eventually must let them go Gastrointestinal
second most common complaint at Everest ER enteritis, gastroenteritis Nepal, Pakistan, Tibet, Ecuador, Mexico, Bolivia, Chile, Argentina, Canada, Alaska almost 30% of Denali climbers about 40% of med pts at EER, incidence likely 80%+ the fantastic combined effects of ondansetron! anorexia, malabsorption fat absorption decreases by up to 50% Sudden cardiac death
etiology is often unknown stress on cardiovascular system due to physiology of altitude hypercoagulability hypoxic arrythmias pre-existing conditions Sudden cardiac death – CV stress Effect of altitude on VO₂ max
Aviat Space Environ Med. 1998 Aug;69(8):793-801.Maximal and submaximal exercise performance at altitude C S Fulco , P B Rock, A Cymerman PMID: 971597 Sudden cardiac death - hypercoagulability risk of spontaneous vascular thrombosis increases 30 times with long stays at high and extreme altitude. DVT, PE, CVA, TIA, portal, splenic and superior mesenteric veins, arterial clots. hemoconcentration, vasoconstriction, stasis, possible changes in clotting cascade may unmask congenital predisposition typically above 4500m ASA use is not uncommon Sudden cardiac death – arrhythmias and pre-existing conditions many climbers chose to not disclose pre-existing conditions. hypoxia is arrhythmogenic, but what type of arrhythmias? significant increase in brady and tachyarrhythmias unclear data on ventricular arrhythmias overuse of azithromycin, ondansetron, other medications without medical oversight, is common. Sudden cardiac death
-53 yo male, no known medical history at 6800m/22,300’ on Aconcagua -sits down at break, slumps over unresponsive. -CPR initiated, sat call. -climber had witheld hx of bovine aortic valve replacement.
Logistics Resuscitation Decision-making Pre-existing medical conditions
Dave Hahn: “Everything is worse at altitude” inherent physiologic stress, decreased buffer frequent nondisclosure awareness of subclinical disease asthma improvement is a silver lining no wheezing but everyone is breathless at altitude. Exhaustion, dehydration
very, very common contribute to CV, pulmonary, emotional stress decreased immune function prevention is crucial nutrition morale clear intake goals Respiratory
diagnostic quandry khumbu cough 38% of medical pts at Everest ER antibiotic stewardship stress and anxiety pulse oximetry Skin
56% of trauma at Everest ER was derm long periods of time in the same clothes poor hygiene dry and cold repetitive motion anorexia Eyes
retinal hemorrhage ubiquitous but rarely symptomatic canary in the coal mine? snow blindness (UV uveitis) proparacaine
Clarke C Neurology at high altitude Practical Neurology 2006;6:230-237. Logistics - medications
the temperature inside tents is extreme difficult to tell if meds got too hot many meds are UV sensitive if capsules freeze they may crack and crumble if medication vials freeze: check for hairline cracks contain and gently melt many meds will lose efficacy Logistics - medications
transporting medications split up and place in carry on bring twice as much as needed always have: a prescription in YOUR name a letter from the expedition physician (which may be you) on expedition letterhead Logistics – insulin
insulin dependent diabetes: go low tech (syringes not pens) antiperspirant/sticky stuff/vet wrap at cannula site have a back-up cannula in place on high risk days keep insulin/strips at appropriate temp 14-30C (good for about 1 month) – carry a cold pack not too warm, not right next to the skin check/purge out air every 1000m be sure several people understand the system Logistics - general
batteries will always die at the most inopportune moment anything ruined by water will get wet old transceiver bags wear well for temperature sensitive items be ready for creative problem solving under pressure understand the environment and resources at hand References
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