We provide a variety of high altitude medicine, critical care, and remote expedition healthcare services. This includes both clinic and mobile medical care, diagnostics, imaging, surgical interventions, intensive care, wound care, suturing, casting, search and rescue, and other forms of urgent care.
High altitude medicine is a vast and interesting field with much to still learn and explore. Rather than be entirely comprehensive, this page is intended to be a condensation of useful information, ideas, insights, research, experience, advice, and references.
Fluid Management at High Altitude:
- Too much hydration can lead to hyponatremia and worsen pulmonary and cerebral edema of AMS. Hypovolemia, on the other hand, can concentrate red blood cells and put kidneys into a fluid conservation state, but hypovolemia can also contribute to poor tissue perfusion, increased work, and alkalosis (which feeds back on high altitude fluid loss), so try to aim for normovolemia. 3 L/day is the base daily loss at altitude (respiration, urine, sweat, etc.), and recommended rehydration rate under high-altitude hypoxic exertion is 5L/day (with a goal to maintain urine color around ~2, urine specific gravity <1.015, and urine osmolality <400mosm/kg). The reality, however, is that in most cases high-altitude climbers drink very little and maintain an extreme resorptive hypovolemic state for a variety of reasons (urgency, lack of time, minimizing carrying weight of water and fuel for melting water, etc.).
High Altitude Medications:
- Acetazolamide (Diamox): primarily for prophylaxis, start the day before ascent, minimum effective dose is ~125mg BID, can go up to 125mg i-ii PO q6-12h (typically not more than 750mg/day). Several mechanisms, including carbonic anhydrase inhibition, renal bicarb excretion to induce a metabolic acidosis, thereby compensating for the altitude-induced respiratory alkalosis (plus inhibition of the kidney’s attempted correction of the metabolic acidosis), and ventilatory stimulation, which can improve SaO2 and periodic breathing in sleep, but kidneys are already losing fluid and electrolytes from the alkalosis (since alkalosis, hypovolemia, and hypokalemia can each induce each other, thus promoting a hypovolemic state in adaptation to altitude), and normally this hypovolemia is good because it concentrates the RBCs and balances out to where the kidneys stabilize in a sodium retention state with minimal water needs… but acetazolamide also acts as a diuretic, which further dehydrates with losses of sodium and bicarb, so must use rehydration strategies to avoid too much dehydration. There is also the danger of stopping/losing/forgetting it during ascents, which when ill-adapted can result in decompensation. Some reports say there is no “rebound effect” when stopping acetazolamide, and although it is true that starting then discontinuing acetazolamide will not typically make an AMS patient worse, discontinuing it later at a higher altitude leaves you vulnerable without certain physiologic and metabolic adaptations, thus making you more prone to quickly be affected by the altitude gain. However, acetazolamide does not “mask” symptoms of AMS. (1) (2) (3) (4)
- Aspirin: may help protect against hypercoagulable/hyperviscous states that can lead to thromboembolic, vasospastic, or ischemic events that can occur in the vasculature at high altitude or prolonged travel, but it should also be noted that retinal and cerebral hemorrhages have also been observed in high-altitude climbers, meaning caution should be taken with any anticoagulation or antiplatelet agents. Aspirin may also prevent or treat headache symptoms of acute mountain sickness (while ibuprofen is not particularly effective): the likelihood of developing headache was reduced from 90% SaO2 with placebo down to 86% with ASA (5) (6).
- Nifedipine 10mg PO q8h prophylactic or treatment of HAPE. There is also some early evidence that propagators of nitric oxide may be benefiticial.
- Tadalafil 10 mg PO q12h or Sildenafil 50 mg PO q8h prn for preventing HAPE, lowering pulmonary hyptertension, and increasing performance and increased cardiac output under hypoxia (not for HACE, may increase AMS).
- Dexamethasone 4mg i-ii PO q12h prn or Dexamethasone 4mg/ml Inject 4-8mg IM prn.
- Other steroids and B2-agonists (bronchodilators like albuterol) do not have great data or conflicting data and thus their use should only be situation-dependent.
Hormones at High Altitude:
- Decreased testosterone appears to be an adaptive response to ultra-endurance events and high altitude, which is likely beneficial. Evidence suggests that testosterone supplementation, while increasing muscle mass and red blood cell production (hemoglobin and hematocrit), may be associated with susceptibility to acute mountain sickness (7). Elevated levels of testosterone, free testosterone, T:E2 ratio, and/or EPO all appear to increase the likelihood of developing altitude sickness. These adaptive changes to high altitude include altered hormonal functions of the adrenal, thyroid, and gonadal axis, typically resulting in lower testosterone with either lower or higher estrogen (E2 or 17-β-estradiol) as well as increased cortisol and free T4 (depending on the rapidity of ascent and whether acclimatization had occurred), and it appears that estrogen functions through its receptors ESR1 & ESR2 to increase circulating nitric oxide and facilitate high altitude adaptations. (8) (9) (10) (11) (12) (13) (14).
- Hypoxic pre-conditioning results in weight loss, stabilization of dietary desire of fat around 28% of diet, and less desire for carb intake (dropping from ~62% down to ~53% of diet)… nevertheless, try to maintain carb intake around 60% of diet to maintain glycogen stores and for optimal performance (preferably >600g of carbs dialy under extreme conditions as tolerated). In one study (Benso), nine elite alpinists who reached at least 7500m altitude and subsisted on a diet of 58% carbs, 30% lipid, and 12% protein all showed no acute mountain sickness, lost an average of 5kg, exhibited increased GH/IGF-1, prolactin, progesterone, insulin-sensitivity, and glucose-dependence (hypoxia-induced), while also exhibiting decreased T3 and testosterone, with no change in cortisol, leptin, or ghrelin despite body weight loss (15). Interestingly, brain natriuretic peptide (BNP) correlates with pulmonary artery systolic pressure and may be a potential marker of the development of altitude illness (16).
High Altitude Training & Adaptation:
- The ideal protocols for high-altitude training are still debated, but in general the optimal protocol should balance peak adaptations without inducing catabolic breakdown and further exhaustion in the body prior to its greatest needs. A good rule of thumb is to work your way up to sleeping at a goal altitude simulation in a way that keeps your nightly oxygen saturation in the range of ~75-85%. If O2 Sat remains higher than this, it’s not enough to induce erythropoiesis and other adaptations, but if it’s lower than this, the body cannot gain sufficient rest and adaptation without suffering other rapid catabolic changes (17). Hypoxia can starve cells of energy, change metabolic and epigenetic profiles, increase erythropoiesis, promote stem cell renewal, perpetuate stem cell niches, favor glyolytic metabolism, and induce weight loss (18).
- Another protocol for elite running optimization from lower altitudes is to aim for at least 12 hours of hypoxic exposure per day for best hematologic adaptations-- stimulating erythropoiesis requires about 2500m equivalent altitude for 12h/day, which induces accelerated erythropoiesis and improvements in economy, muscle buffering capacity, hypoxic ventilatory response and Na(+)/K(+)-ATPase activity. Along with this, one should sleep or live at high altitude simulation for 5 nights out of 7. Most training can actually be done at baseline altitude, but at least 2 days of the week should be higher intensity workouts under hypoxic conditions (19).
- We rent out a High Altitude Hypoxia Training Simulator and Hypoxic Sleep Tent Chamber (MAG-30 Total Altitude System Generator & Tent) for just $25 per night. Hypoxic chambers are not against WADA rules.
Nutrition for High Altitude:
- Optimizing iron levels seems to impart benefits to performance and prevention of high-altitude sickness, whether by diet, oral supplementation, or IV infusions (20) (21).
- 200mg Vitamin E BID (decreases detrimental lipid peroxidation) – may prevent decrease in Protein C at altitude and stabilize protein degradation and endothelial cell structure (22).
- High-Altitude Cerebral Edema [HACE]: Descend immediately, as this is primarily a hypoxic metabolic failure within the cell resulting in both cytotoxic and vasogenic edema. Use medications as listed above.
- High-Altitude Pulmonary Edema [HAPE]: Descend immediately, as this is primarily a hypoxic metabolic failure within the cell resulting in both cytotoxic and vasogenic edema. Use medications as listed above. This can be visualized on ultrasound imaging with better sensitivity and specificity than CXR, typically seen as 3 comet features per level along with O2 sats in the 60-70% range (23).
- Grade 2-4: Iloprost (within 72h) diluted to 0.2mcg/ml infused at 10ml/h IV to weight-based dose (over 6h) – Dose 0.5-2.0ng/kg/min [meaning infusion rate for 70kg man is 10.5-42ml/h]… usually use the higher end of this, meaning infuse 2ng/kg/min for 6h/d x5days.
- Grade 4: After Iloprost, can add Alteplase (15mg IV over 2min then 0.75mg/kg [max 50mg] over 30min, then 0.5mg/kg [max 35mg] over 60min + Heparin 60U/kg IV then 12U/kg/h for 6h, then adjust to PTT.
- Prostaglandin E1 and even ASA can also be used as alternatives when Iloprost not available.
- Ibuprofen and morphine for pain (plus lidocaine LA without epi to vasodilate).
- LMWH (or dextran 40) daily for 5-7d.
- Cefazolin 1g IV x 3 doses for apparent infections.
- Pentoxifylline (decrease viscosity) 400mg PO 2-3x daily.
- Bencyclane-fumarate (vasodilator) 100mg PO TID (up to 200mg PO TID, can also give IV).
- Gauze pads, needle/syringe and/or scalpel to debride clear blisters and necrotic tissue.
- Rewarm only once you can ensure no re-freezing (e.g., rewarm in 10% iodine at 40degC for 20min) (24).
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