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Author Topic: Mountain and Cold Weather Environments
Flight-ER-Doc
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Cold-Weather Medical Considerations

Flight-ER-Doc © 2018


Contents:

Introduction – The Mountain Environment
Section 1 – Hypothermia
Section 2 – Frostbite
Section 3 – Acute Mountain Sickness
Section 4 – High Altitude Cerebral Edema
Section 5 – High Altitude Pulmonary Edema
Section 6 – Solar Keratitis (Snow Blindness)
Section 7 – Considerations for First Aid Supplies
Bibliography

Introduction – The Mountain Environment

At 10,000 feet elevation (above sea level), the standard air pressure is 10.1 psi. This is 40% less than the air pressure at sea level of 14.7 psi. Because of this, the amount of oxygen available to your body is much less. At sea level, a normal amount of oxygen in oxygenated (arterial) blood is 97% of the maximum carrying capacity, at 10,000 feet it is only 90%. You have less oxygen to work with, so it is important to use it well, through cardiovascular conditioning. By the way, a pack-a-day cigarette smoker is already cruising at 10,000 feet, when they are at sea level, based on their bloods’ oxygen carrying capacity so smoking is not healthy for you in the mountains, either.
Because of less air above you and the highly reflective snow around you, the effects of sunlight are much higher – which can lead to sunburn. The reflections from the snow on the ground often lead to sunburn on normally protected areas (the lower portion of the nose and the entrance of the nostrils are often sunburned in these situations). Sunburn can occur even in dark-skinned people, and can become severe enough to lead to blistering (second-degree burns) in both light and dark skinned people. Lips can become sun and wind-burned, and this injury can lead to reduced desire to eat or drink – compounding other problems.
Mountain temperatures at altitude are also lower – especially in the winter. Low temperatures affect the body in different ways. It can both hurt you (via cold injuries like frostbite or hypothermia) and make life difficult for your body. Since cold air is usually dry air, you will lose more bodily fluids breathing than at normal elevations and humidity levels – but because of the low temperatures, you may not feel thirsty, and you can end up dehydrated. Water is heavy, and carrying enough of it to drink can be difficult. Melting snow for water to drink or cook with is time consuming, and you must carry fuel above tree line to use for melting. This can add to the dehydration. Because the various metabolic processes in the body (on the cellular level) are quite sensitive to the temperature and pH levels, these changes can affect the ability of the body to digest food, which can result in lowered energy availability – just when you need extra energy the most. Overall, the mountain environment is challenging.
Adaptation
The human body has a remarkable ability to adapt to various environmental conditions – which is why people live in the high arctic areas where winter temperatures can be below -40oF, and in Saharan Africa where the temperatures can reach over 120oF, or from high humidity locations (jungles) to very low (deserts), or high elevations (mountains) or low. Some adaptations happen quite rapidly, some take longer. Some of the normal adaptations that happen include:
Hyperventilation (deeper, faster breathing because there is less oxygen available per breath – so you need more breath.
Shortness of breath on exertion – which can include just standing or sitting around, since your body is working harder at altitude just keeping you alive. Breath patterns during sleep can be quite different, including “Cheyne-Stokes” respiration (breathing) which is cycles of increasingly deep breaths followed by a short period of no breathing at all (called apnea)…this is very noticeable in your tent partners and the periods of apnea can be enough to wake you up from sleep. While distressing, this is normal, and aside from preventing a good night’s sleep is not especially dangerous in the absence of other medical problems. This is not AMS – acute mountain sickness. Cheyne-Stokes respirations happen because deeper breaths changes the acidity of your blood (makes it more alkaline since you’re blowing off carbon dioxide in the form of carbonic acid) and the part of your brain that controls breathing says “wait a second, let’s let the acid build up again”.
Awakening frequently at night – this is annoying, but not serious, and is caused by disruptions in breathing, Cheyne-Stokes respirations, being cold or uncomfortable, or needing to urinate.
Finally, increased urination, especially at night. Your kidneys are responsible for keeping your bloods pH balance in a very narrow range, and one way it does this is by excreting bicarbonate ions – which needs to be flushed from the body. This is only dangerous if you become dehydrated, so it’s important to drink lots of water. Having a ‘pee bottle’ at night makes this frequent urination less onerous. Not having to urinate, especially at night, may be a sign that you are dehydrated, which can be dangerous.
Likelihood
Some people are more likely to have various forms of altitude or cold injuries than others are. Genetic background, past incidents of cold injuries, chronic diseases, and physical condition are all variables that can affect individual performance. However, some people, even those in very good cardiovascular condition can have difficulties in the cold/high altitude environments, and people who have done well previously can have difficulties apparently without an obvious reason. Only time will tell. One good marker for expecting difficulties from cold injuries is a previous cold injury: If you have had frostbite before you are much more likely than others in the same conditions to have it again. Likewise, if you have had altitude-related problems, you are more likely to have it again. Know your limitations.
Risks of chronic conditions in the mountain environment

Minimal risk Some documented risk – consider medical monitoring, availability of oxygen Substantial risk –
ascent not advised
Children and elderly Carotid surgery or irradiation COPD, severe
Physically fit and unfit Sleep-disordered breathing and apnea Coronary artery disease, with poorly controlled angina
Obesity COPD, moderate CHF, uncompensated
Chronic obstructive pulmonary disease (COPD), mild Cystic fibrosis Congenital heart disease ASD, PDA, Down’s syndrome
Asthma Hypertension, poorly controlled Pulmonary hypertension
Hypertension, controlled Coronary artery disease, with stable angina Pulmonary vascular abnormalities
Coronary artery bypass grafting, angioplasty, or stenting (without angina) Arrhythmias, high-grade Sickle cell anemia (with history of crises)
Anemia, stable Congestive heart failure (CHF), compensated Pregnancy, high-risk
Migraine Sickle cell trait
Seizure disorder, on medication Cerebrovascular disorders
Diabetes mellitus Seizure disorder, not on medication
LASIK, PRK Radial keratotomy
Oral contraceptives Diabetic retinopathy
Pregnancy, low-risk
Psychiatric disorders
Neoplastic diseases
Inflammatory conditions
From table 38-5, Travel Medicine 1st Ed.

Prevention
Most medical problems due to the mountain environment are preventable.
Be aware of your own condition, and the condition of your partners. The onset of most problems is insidious and the victim may not be aware of them – both visible problems like frostbite and problems that may result in behavioral changes, for instance due to less oxygen in the air.
Having the correct equipment (clothing, shelter, water, sunglasses, etc) is critical to preventing injuries – but you have to carry all that gear! Take what you need, but try not to overdo it.
Structure
Definitions are normally explained when a technical or medical term is first used. Generally, however, the distinction between a sign and a symptom is important: (symptoms are what the patient reports, signs are what the physician can see, touch, or measure). In other words, you complain about symptoms, the doctor sees signs.

Each section is set up with a
• Definition of the condition; the keys to differentiating conditions with similar signs/symptoms between serious and non-serious conditions
• Identifying the condition (signs and symptoms, and if necessary how to tell a serious condition from a less serious one with similar signs and symptoms
• Treatment both immediate and intermediate
• Prognosis, or how the victim can be expected to fare with the condition, and most importantly
• Prevention. Prevention is easy for all of these conditions, and is much preferred over treatment.

Section 1 : Hypothermia
Definition
Hypothermia is the lowering of the bodies core temperature, which is normally around 37oC (98.6oF), below the normal range (that is, to a temperature below 35oC or 95oF). While hypothermia is often deliberately induced (for certain kinds of surgery, for example) we are only concerned with accidental hypothermia.
Accidental hypothermia can occur slowly and insidiously because of inadequate clothing in cold temperatures, or suddenly and catastrophically, from falling through a frozen lake surface. Either way, lowering the bodies’ temperature is dangerous. The various chemical processes that occur in your body are very sensitive to slight changes in conditions, including temperature, and lowering their temperature can stop them from happening.
Identification – Signs, symptoms
The classic sign of hypothermia is a 2oC (or more) lower than normal body temperature. So, the best way to identify hypothermia is with a thermometer. Special, low-range thermometers are available for hypothermia use, most oral digital thermometers will read low enough as well.
Hypothermia can be categorized by the effect that lower temperatures cause, and differentiated into four distinct ranges that can be estimated by their signs:
Stage Core Temp Characteristics
Mild 99.6 Normal rectal temperature
98.6 Normal oral temperature
96.8 Increase in metabolic rates, pre-shivering muscle tone
95.0 Maximum shivering (to generate heat from muscle movement)
93.2 Development of poor judgment and amnesia
91.4 Development of ataxia (staggering gate) and apathy, faster breathing (tachypnea)
Moderate 89.6 Stupor
87.8 Shivering stops (DANGER)
86.0 Atrial fibrillation and other heart arrhythmias begin
85.2 Progressive decrease in level of consciousness, pulse, and respiration; pupils dilated; paradoxical undressing (the victim is cold but removes clothing)
Severe 82.4 Ventricular fibrillation begins, hypoventilation (breathing nearly stops)
80.6 Loss of reflexes and voluntary motion
78.8 Major blood acid-base disturbances, no pain response or reflexes
Profound 68.0 Pulse 20% of normal
64.4 Asystole (heart stops, flat lines)
59.2 Lowest infant accidental hypothermia recovery
58.6 Lowest adult accidental hypothermia recovery

Treatment – initial, intermediate
For a mild to moderately hypothermic person, the most important step is to first stop their heat loss. Get them into warmer surroundings, dry or warm clothes, and/or get them out of the wind. Even a slight windbreak created by digging a small depression in snow is better than continuing to expose the patient to the effects of wind chill, a tent, or a more formal structure is better.

For moderately (or more) hypothermic patients, expect their hearts to be irritable – don’t handle them roughly while attempting to warm them because the rough handling may cause a heart arrhythmia.
For patients found who appear to have severe to profound hypothermia, consider postponing CPR. A rigid chest wall will prevent chest compressions, and blood pH changes can themselves cause heart arrhythmias, especially when cold peripheral blood moves to the core by mechanical compressions.
Moderately or more hypothermic patients should be transported to medical care for evaluation. Warming can occur with gentle hot water bottles in the groin and axilla, if the victim is able to grasp a container and drink from it on his own, warm fluids (non-alcoholic) can be taken in small sips – but make certain the fluids aren’t too warm, since reflexes and temperature sensation may be missing.

If a victim is found cold, pulseless, and unresponsive, treat them as a profoundly hypothermic victim: Handle gently, package for transport (see below), and get them to definitive medical care as rapidly as possible. It is impossible to tell in the field if a patient is suffering from a heart attack, or profound hypothermia, both can easily mimic conditions of death. There is a saying “The patient isn’t dead, until they’re warm and dead”, because of this…give the victim the chance, if possible.

Preparing the hypothermic patient for Transport


Prognosis

The prognosis is dependent on the degree of hypothermia that the victim sustained. It can vary from full recovery with no sequelae to being in a persistent vegetative state from prolonged hypoxia.

Prevention
Stay warm and dry. Avoid overheating and consequential perspiration, which will result in rapid cooling once your exertions stop. Wearing wicking undergarments to move moisture away from your skin will help keep you dry, but you must control your perspiration and ventilation to stay dry.

Vascular dilators (blood pressure medication) may increase the risk of hypothermia. Discuss using them with your physician prior to cold exposure.


Section 2 : Frostbite
Definition
While hypothermia is a reduction in the body’s core temperatures, frostbite, frosting, chilblains and trenchfoot are hypothermia related injuries to peripheral (extremity) tissues.
Identification – Signs, symptoms
Frostbite injuries are categorized into degrees of damage, similarly to burns.
First- and second-degree frostbites are superficial injuries that present with edema (swelling), burning, erythema (redness), and in second-degree, blistering.

Third-degree frostbite is a deeper injury involving the full-thickness skin and the subdermal tissue. The tissue’s appearance will be on a continuum from the redness of first-degree frostbite to the pale, hard tissue of fourth degree. Like burns, various areas of the affected tissue will have different levels of frostbite.

Fourth-degree injury includes subcutaneous tissue, muscle, tendon, and bone. Patients present with cyanotic and insensate tissue that may have hemorrhagic blisters and skin necrosis. Subsequently, this tissue appears mummified.

Frostbite – In feet and toes
Fig a Fig b Fig c

Fig a and b Before thawing, the clinical appearance of the frozen part is cold, white, or bloodless. The outer shell of skin is rigid, and the depth of freezing is difficult to determine. (c) After rapid thawing, the part is flushed red or pink, or has a violaceous hue. Blebs appear 1 to 24 hours after the thaw and rupture spontaneously in 4 to 10 days. The cast-like eschar forms after the blebs rupture, and the eschar sheds after 21 to 30 days. Photos from Medical Aspects of Harsh Environments, vol 1.


Frostbite – Outer Ear

Figure a Figure b Figure c

Warming techniques and tissue loss. (a) Frostbite of an ear without tissue loss after rapid rewarming. Frostbite of ear in (b) a young man and (c) an elderly patient; each had tissue loss after spontaneous thawing. Photos from Medical Aspects of Harsh Environments, vol 1.

Frostbite – In Hands and Fingers
Figure a Figure b Figure c Figure d


Figure e Figure f


Rapid rewarming in a water bath at 42°C (108°F). (a) First day. The patient sustained freezing of hands and feet on the Arctic Slope when marooned in the open as a result of a vehicle accident. Winds were 80 knots, ambient temperature between –20°C and –26°C. The patient lost his overboots and gloves in the accident. His entire exposure time, he states, was 15 to 20 minutes, followed by 45 minutes in the wrecked vehicle awaiting rescue. On rescue, he was warmed in water at 42°C (106°F); the warming and care were directed by radio from Anchorage, Alaska. The patient was then transferred from the Arctic Ocean shore to Anchorage by air travel at 24 hours. On arrival, the hands demonstrated large, clear, pink blebs extending to fingertips; these are excellent prognostic signs, especially that the blebs are distal and extend to the nailbeds. NOTE: Only after rapid rewarming in warm water is there return of sensation in the fingertips; this remains until blebs appear in the dermis and epidermis and separate those tissues from the deep structures. (b) Fourth day. Constant, twice-daily whirlpool is prescribed with digital exercises, using surgical soaps such as pHisoHex,* Hibiclens,† or Betadine.‡ (c) Twenty-first day. By the third week, epidermal eschar has formed, preventing joint motion. (d) Fourth week. Periodically, when the tissue permits, the eschar is incised to allow joint motion. Escharotomy usually is performed from the 14th to the 31st day. (e) Fifth week. Digital exercises are done at frequent intervals at least four times daily, as with whirlpool and biofeedback training. By this time, loss of volar fat pad and loss of nails have occurred and hypesthesia is resolving. (f) Seventh week. The anatomical result is good, but volar fat pad loss and intrinsic muscle loss are obvious. The patient has considerable atrophy of the first dorsal interosseus, and of the abductor digiti quinti. Photos from Medical Aspects of Harsh Environments, vol 1.

Treatment – initial, intermediate

Rapidly rewarm frostbite over a period of 20 minutes in water ranging from 40° to 42°C (104-107oF). Be careful the water is not too hot – normal tap hot water is too hot, it can cause serious damage that the victim may not be able to sense due to the loss of sensation from the frostbite.

Do not massage or rub the frozen part – it might increase tissue damage. Rewarming will be painful; use an analgesic a needed. Ibuprofen (Motrin™) is preferred in this application since its prostaglandin-e and thromboxane-inhibiting role assists in preventing further tissue damage by preventing vasoconstriction and platelet aggregation.

Prognosis
Prognosis of frostbite injury depends on the degree and location of the injury, but can be severe, especially if not treated correctly, or if the affected part is allowed to refreeze. If there is any doubt that the affected part can be kept from refreezing, consider delaying the initial thawing until there is assurance that the part will remain warm.

Administration (by a medical professional in the appropriate setting) of tissue plasminogen activator (tPa) given intravenously within 24 hours of injury and within 6 hours of rewarming significantly decreased the extent of amputation in severe frostbite.
Prevention
Frostbite is usually preventable by proper clothing – including face shields or masks. Observe partners or use a mirror to check your own nose and ears for frostbite if necessary. In extreme conditions, consider spare gloves, hats, scarves, etc, in case you lose yours or they become wet. In particular, keeping gloves and socks dry can be problematic, having spares to change into can be important.

Use of ergot alkaloid drugs (sometimes used for migraine treatment) can increase the chances of developing frostbite – discuss using or stopping the drugs with your physician prior to travelling to cold locations.

Non-freezing cold induced injuries

Chilblains - Chilblains (pernio) presents with painful and inflamed skin lesions caused by chronic, intermittent exposure to damp, nonfreezing ambient temperatures.

Frostnip - is a less severe form of frostbite that resolves with rewarming and involves no tissue loss.

Trench foot - Trench foot results from cooling of tissue in a wet environment at above-freezing temperatures over several hours to days. Long-term hyperhidrosis (increased perspiration) and cold insensitivity are common results. Prevention is by keeping feet dry by changing socks as needed.
Once affected by chilblains, frostnip, or frostbite, the involved body part becomes more susceptible to reinjury.

Section 3 : Acute Mountain Sickness

Definition
AMS is a constellation of symptoms that represents your body not being acclimated to the current altitude. As you ascend (by walking, driving, flying, or any other method) your body attempts to adjust to the hypoxia (reduced oxygen available at that altitude).
At any given altitude, there is a ‘sweet spot’ that your body tries to achieve between breathing, blood pressure, metabolism, etc. AMS occurs when your body is not in that sweet spot.
The actual cause of AMS is not understood, it is thought that slight brain swelling caused by a change in blood pH may be involved.
Identification – Signs, symptoms
As defined by the ‘Lake Louise Consensus on the Definitions of Altitude Sickness’, AMS is a grouping of symptoms that in the setting of recent altitude gain, any one or more of the following symptoms constitutes AMS: In the setting of a recent gain in altitude, the presence of headache and at least one of the following symptoms -
- Gastrointestinal distress (anorexia (loss of appetite), nausea or vomiting);
- Fatigue or weakness;
- Dizziness or lightheadedness, ataxia (unsteady gait);
- Difficulty sleeping; constitutes AMS.

Clearly, these common symptoms may result from any number of unrelated conditions. More specifically, AMS can be considered a severe headache (often in the area above the eyes) that is not caused by dehydration (see below), and severe indications of these other criteria.

Differentiating AMS and severe headache.
Severe headaches can be common in the mountain environment, due to cold, dehydration, and stress but this is not the same as AMS. While it is impossible to totally differentiate between these two causes, if a person complains of a headache first have them drink a liter of fluid, and take a mild analgesic (ibuprofen (Motrin™), acetaminophen (Tylenol™), aspirin) and have them rest a bit: If their headache resolves completely in a short time (30-60 minutes) it is probably not AMS related. AMS symptoms don’t resolve with these treatments, nor are they made worse by them.
Treatment – initial, intermediate
If symptoms are caused by AMS, descending is the best treatment. A descent of only 1000-2000 feet may be sufficient to resolve the symptoms. Because of the unsteady gait, the victim must have assistance during the descent – usually at least two persons to help steady them.
A prescription drug, acetazolamide (Diamox™) can be given orally (250mg, bid) if available, and the individual is not allergic to sulfa-type drugs. Acetazolamide does not prevent all symptoms of AMS, does not mask the symptoms of AMS, and is not a replacement for slow, steady acclimatization.
Supplemental oxygen therapy is usually not indicated for AMS, descent is a far better treatment.
Hyperbaric chamber therapy (Gamow ™ bag or similar) is not indicated for AMS therapy at intermediate altitudes.
Recently, some interest in gingko biloba as a cure or preventative for AMS has been discussed. Extensive double-blind investigations have shown that gingko is no better than a placebo in preventing AMS, so its use is not recommended.
Prognosis
The prognosis following AMS is generally good. With rapid descent, the patient usually recovers without any sequelae. It generally won’t kill you (although the headache can be so severe that at first you’re worried it will kill you, then you’re worried it won’t), but it can develop into HACE – high altitude cerebral edema (see below), which is quite serious.
Prevention
Slow, steady acclimatization is the key to avoiding most altitude related conditions. The typical individuals travel from near sea level to trailheads at some considerable elevation, just to jump off to a higher elevation on foot is a sure prescription for AMS and other altitude related disorders.
For longer ascents a good strategy to follow for climbing is to climb high each day, but return to a lower altitude to sleep for the night. This is more applicable to expedition climbs such as in the Himalayas, but if possible, it works at lower altitudes.

Section 4 : High Altitude Cerebral Edema (HACE)
Definition
HACE can be considered a serious continuation of the constellation of symptoms of AMS. At the "severely ill" end of this spectrum is High Altitude Cerebral Edema; this is when the brain swells and ceases to function properly. Since the skull is rigid in adults any swelling compresses the brain tissue, obstructing blood flow, and in serious cases can cause the brain stem to herniate (squeeze through) the opening in the bottom of the skull that the spinal cord passes through, the ‘foramen magnum’.

Persons with this illness are often confused, and may not recognize that they are ill. They are, and proper treatment is critical.

HACE can progress rapidly, and can be fatal in a matter of a few hours to one or two days. It can rapidly become a medical emergency, requiring treatment or the victim may die.

Identification – Signs, symptoms
Can be considered "end stage" or severe AMS. In the setting of a recent gain in altitude, either:
- The presence of a change in mental status and/or ataxia in a person with AMS
- Or, the presence of both mental status changes and ataxia in a person without AMS

The hallmark of HACE is a change in mentation, or the ability to think. There may be confusion, changes in behavior, or lethargy. There is also a characteristic loss of coordination called ataxia. This staggering walk is similar to the way a person walks when very intoxicated on alcohol. This loss of coordination may be subtle, and must be specifically tested for. Have the sick person do a straight-line walk (the "tandem gait test").

Draw a straight line on the ground, and have them walk along the line, placing one foot immediately in front of the other, so that the heel of the forward foot is right in front of the toes behind. Try this yourself. You should be able to do it without difficulty. If they struggle to stay on the line (the high-wire balancing act), cannot stay on it, fall down, or cannot even stand up without assistance, they fail the test and should be presumed to have HACE.


Treatment – initial, intermediate

Immediate descent to lower elevations is the preferred treatment for HACE. This is critically important, it must be done immediately, – it can’t wait until morning even though HACE symptoms become apparent or worse at night. The moment HACE is recognized, begin evacuating the victim, with assistance, (at least two people assisting), to at least the lowest elevation the victim last felt well.

Other treatments, including supplemental oxygen therapy, hyperbaric chambers (Gamow bags or similar), etc are less effective in treating HACE.

Pharmaceutical therapy with systemic corticosteroids may be used as well. Dexamethasone (4mg, two doses 6 hours apart) may be given orally or intramuscularly if the patient is vomiting. These supplemental therapies should not be used in cases where descent and evacuation are possible.


Prognosis
The prognosis from HACE is generally good, with full recovery – however the ataxic gate may continue for several days following descent to normal elevation. Once full recovery occurs, the victim may attempt re-ascent with proper acclimatization.



Section 5 : High Altitude Pulmonary Edema (HAPE)
Definition
Another form of severe altitude illness is High Altitude Pulmonary Edema (HAPE), or fluid in the lungs. Though it often occurs with AMS, it is not felt to be related and the classic signs of AMS may be absent. HAPE may also be mistaken for other diseases (see below).

Identification – Signs, symptoms

In the setting of a recent gain in altitude, the presence of the following:
Symptoms: at least two of the following:
- Dyspnea (difficulty in breathing) at rest;
- cough;
- weakness or decreased exercise performance;
- chest tightness or congestion;

Signs: at least two of the following:
- crackles or wheezing in at least one lung field;
- central cyanosis (blue tinge to skin on central body – chest, lips, throat, etc…a blue tinge on lips, fingers, etc may be cold related);
- tachypnea (rapid breathing, faster than 30 breaths per minute);
- Tachycardia (rapid heartbeat, greater than 100 beats per minute in a resting individual);

Other signs and symptoms include:
- Extreme fatigue
- Breathlessness at rest
- Fast, shallow breathing
- Cough, possibly productive of frothy or pink sputum
- Gurgling or rattling breaths
- Chest tightness, fullness, or congestion
- Blue or gray lips or fingernails
- Drowsiness

HAPE usually occurs on the second night after an ascent, and is more frequent in young, fit climbers or trekkers. In some persons, the hypoxia of high altitude causes constriction of some of the blood vessels in the lungs, shunting all of the blood through a limited number of vessels that are not constricted. This dramatically elevates the blood pressure in these vessels and results in a high-pressure leak of fluid from the blood vessels into the lungs. Exertion and cold exposure can also raise the pulmonary blood pressure and may contribute to either the onset or worsening of HAPE.

HAPE can be confused with a number of other respiratory conditions:
High Altitude Cough and Bronchitis both are characterized by a persistent cough, with or without sputum production. There is no shortness of breath at rest, and no severe fatigue. Normal oxygen saturations (for the altitude) are seen if a pulse oximeter is available.

Pneumonia can be difficult to distinguish from HAPE. Fever is common with HAPE and does not prove the patient has pneumonia. Coughing up green or yellow sputum may occur with HAPE, and both can cause low blood levels of oxygen. The diagnostic test (and treatment) is descent – HAPE will improve rapidly. If the patient does not improve with descent, then consider antibiotics. HAPE is much more common at altitude than pneumonia, and more dangerous; many climbers have died of HAPE when they were treated for pneumonia.

Asthma might also be confused with HAPE. Fortunately, asthmatics seem to do better at altitude than at sea level. If you think its asthma, try asthma medications, but if the person does not improve fairly quickly assume it is HAPE and treat it accordingly.


Treatment – initial, intermediate

Minimize exertion and keep warm. Like HACE, rapid descent is the best treatment. Other treatments include:
Oxygen, 4 to 6L/min until improving, then 2 to 4L/min
If oxygen is not available:
• Nifedipine, 10 mg PO q4h by titration to response, or 10 mg PO once, followed by 30 mg extended release q12 to 24h
• Inhaled beta-agonist (albuterol, Ventolin ™)
• Consider sildenafil (Viagra ™) 50 mg every 8hrs
• Hyperbaric therapy via Gamow bag or similar

Prognosis
It is common for persons with severe HAPE to also develop HACE, presumably due to the extremely low levels of oxygen in their blood (equivalent to a continued rapid ascent). HAPE resolves rapidly with descent, and one or two days of rest at a lower elevation may be adequate for complete recovery. Once the symptoms have fully resolved, cautious re-ascent is acceptable.
Prevention
While careful ascent with acclimatization is preferred, some people are predisposed to altitude illnesses even with good physical conditioning and careful acclimatization.

Section 6: UV / Solar Keratitis (Snow Blindness)

Definition

Because of less atmosphere above you filtering light, and the highly reflective snowfields around you, the eye can receive 10-15 times as much light, especially ultraviolet light, as is healthy. This extra light can result in temporary damage to the outer layer of the eye.

Identification – Signs, symptoms

Intense pain and a feeling of ‘grit’ or sand in the eyes, felt when blinking. The eyes are painful and the victim may have a nearly uncontrollable urge to rub them.


Treatment – initial, intermediate

Treatment consists of antibiotic ointment (if available, and only optic formulations), mild analgesics (NSAIDS like ibuprofen) and perhaps eye patching. If the victim’s eyes are patched, they are unable to assist in their own evacuation; if only one eye is patched, they will still require assistance because of the loss of depth of vision.

Prognosis

The prognosis for solar keratitis is good – while the condition is painful and annoying it will normally resolve within a day or two without any follow-on problems.

Prevention

Wearing high quality tinted glasses or goggles will help prevent snow blindness – and having a spare pair in case you lose or break your primary pair is a good idea.

Good goggles or glasses have the following characteristics:
- 99-100% UV absorption
- Polycarbonate or CR-39 lens (lighter, more comfortable than glass)
- 5-10% visible light transmittance
- Large lenses that fit close to the face
- Wraparound or side shielded to prevent incidental light exposure

The actual color is more a matter of personal preference – some people prefer neutral gray lenses to minimize color changes, others find that various shades of yellow or amber help with ‘flat’ light conditions.

If sunglasses are not available, a replacement can be made from fabric, wood or plastic tied across the face (as glasses are) with a small horizontal slit cut in it over the eye position, to provide vision. While wearing a hat is necessary, a brimmed hat will provide minimal protection against snow blindness because light will be reflected up from the snow on the ground.


Section 7 : Considerations for First Aid Kits

Because of the cold temperatures, avoid (as much as possible) any liquids or gels including ointments. Drugs that freeze may separate, and when they thaw not recombine correctly, rendering them dangerous or useless. In particular, protein-containing drugs (such as insulin) must not be allowed to freeze, or NOT USED if frozen – the proteins will precipitate from the solution and can cause a thrombosis.

Solid pills or tablets can be frozen if needed. Capsules (which are made from gelatin) will deteriorate rapidly when frozen and should be avoided.

If liquids or gels are necessary and unavoidable, pack them with good insulation. A small chemical heat pack may help keep them from freezing; or keep them close to your body.


Hyperbaric chamber therapy
For high-altitude (> 15,000 feet) a transportable, fabric, hyperbaric chamber such as the Gamow Bag ™ is commercially available, for use when evacuation to lower elevations are not possible because of distance or weather conditions. The victim is placed in the bag, which is then zipped closed, and a foot-operated air pump increases the atmospheric pressure inside the bag by a pound or two, which can be the equivalent (at high altitude) of a 5,000-foot descent. With sufficient resources the patient can be evacuated while in the chamber, using a basket stretcher or similar device.


Gamow bag (picture from Wikipedia)
Gamow and similar bags are heavy, and somewhat expensive. They can be rented for specific expeditions from various sources if desired.

Bibliography:
Auerbach, et al. Field Guide to Wilderness Medicine, 3rd Ed. New York, NY Mosby, 2008
Auerback, et al. Wilderness Medicine, 5th Ed, Philadelphia, PA Mosby, 2006
Fauci, et al, ed. Harrisons Principals of Internal Medicine, 17th Ed, New York, NY. McGraw Hill, 2008
Forgey, William. Wilderness Medicine, Beyond First Aid, 5th Ed. Guilford, CT Globe Pequod Press, 1999
Guyton, Arthur C, Hall, John E, Textbook of Medical Physiology, 11th Ed. Philadelphia, PA, Elsevier Saunders. 2006.
High Altitude Medical Guide, Lake Louise Consensus on the Definition of Altitude Sickness, http://www.high-altitude-medicine.com/AMS-LakeLouise.html, last accessed 2 Feb 2010.
Keystone, et al. Travel Medicine, 1st Ed, Philadelphia, PA Mosby 2004
Kumar, et al. Robbins and Cotran Pathological Basis of Disease, 7th Ed. Philadelphia, PA. Elsevier Saunders, 2005.
Ma, et al. Tintinallis Emergency Medicine Manual, 6th Ed, New York, NY. McGraw Hill, 2003
Marx, Rosen’s Emergency Medicine, 6th Ed, Philadelphia, PA, Mosby, 2002
Montgomery and Kotwal, Ranger Medic Handbook, 75th Ranger Regiment Trauma Management Team (Tactical), US Army Special Operations Command, 2007
National Association of Emergency Medical Technicians. Prehospital Trauma Life Support – Military Edition, 6th Ed. Philadelphia, PA. Mosby/Jems, 2006
Pandolf, Burr (eds), Medical Aspects of Harsh Environments vols 1 and 2, Borden Institute, Office of the Surgeon General, US Army, Falls Church, VA 2002
The International Mountaineering And Climbing Federation / Union Internationale Des Associations D’alpinisme (UIAA), Consensus Statement Of The UIUAA Medical Commission Vol: 10 The Effect Of Extremes Of Temperature On Drugs, Berne, Switzerland, 2008

Yevich, et al. Special Operations Forces Medical Handbook 1st Ed, Jackson, WY Teton Press, 2001

--------------------
Emergency Medicine - saving the world from themselves, one at a time.

"Thou shalt not be a victim, thou shalt not be a perpetrator, but, above all, thou shalt not be a bystander."

I make the ADL soil themselves. And that makes me very happy :)

Posts: 1935 | From: Slipping the surly bonds of earth | Registered: Dec 2004  | Report this post to a Moderator
airforce
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I had never heard of Viagra as a treatment for HAPE, but it makes sense. Increasing blood flow should increase the amount of oxygen circulating through the body.

Good stuff!

Onward and upward,
airforce

Posts: 17337 | From: Tulsa | Registered: Jan 2002  | Report this post to a Moderator
   

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