High Altitude Medical Problems

Transcription

1 High Altitude Medical Problems Wilderness Basics Course Jeffrey H. Gertsch, MD Assistant Professor of Neurosciences UCSD School of Medicine

2 Definition/Site ISMM Definitions Altitude in Meters Altitude in Feet High Altitude 1,500-3,500 5,000-11,500 Very High Altitude 3,500-5,500 11,500-18,000 Extreme Altitude >5,500 >18,000 Laguna Mountains 2,000s 6,200s Top of most ski lifts (aka moderate alt) 2,500-3,500 8,000-11,500 Mt. Whitney Summit 4,421 14,505 Mt. Everest Base Camp 5,380 17,700 Mt. Everest Summit 8,848 29,029

3 Why Is Altitude Illness Important? >30 million in US & 100 million worldwide recreate above 2000m annually Skiing/snowboarding Hiking/Climbing Military (2 conflicts/decade from 40s) Medicine/physiology Aerospace/aviation/space flight Geology/astronomy

4 Why Is Altitude Restrictive? Low Pressure: O2 a consistent 20.93% of atmosphere atmospheric pressure decreases w/ altitude Environmental extremes: coldest climes Radical terrain highest winds solar radiation (UV) Decreased resources (cal)

5 Blood Oxygen At Altitude JB West. Respiratory System Under Stress. In Respiratory Physiology; The Essentials. 6 th Edition, Lippincott Williams and Wilkins, Philadelphia, 1999, p 119.

6 What happens with half the available oxygen? Normal sea level blood oxygen: % Normal SaO2 on Mt. Whitney: 85-92% Strategy: increase efficiency of delivering oxygen to the tissues = acclimatization What tissues at highest risk of malfunction, w/highest metabolic demand/least reserve?

7 Acute General Acclimatization 2-5 minutes: Stress HR/BP increase minutes: Hyperventilation (HVR) Hours: 1. Pulmonary/cerebral blood flow increase 2. Blood chemistry changes Increased urination 3. Increased urine prod Polycythemia (thicker blood)

8 Chronic General Acclimatization Day 1: Renal Epoetin release Increase red blood cell production Week 1: Changes in respiratory/blood factors equal contribution to acclimatization Week 6-8: New blood vessels in musculature endurance/resilience End week 6: Climb 8000m peaks!

9 Conceptualizing Altitude Sickness Acclimatization vs. Illness: When balance fails, illness results Good acclimatization = hyperventilate/urinate Health Poor acclimatization = hypoventilate & decreased urination (fluid retention) vascular injury/ waterlogged tissue Illness Neurological syndromes most common forms of illness by far Severe forms include swelling of brain/lung

10 Acclimatization Incomplete at high altitude and does not occur at extreme altitude. Over 18,000 ft, gradual decrease in physical conditioning and a progressive mental deterioration.

11 Brain Acclimatization Nervous tissue the most sensitive to low oxygen. Minutes: Oxygen-starved brain swells w/blood. Cerebral blood flow increases >50%, tense vessels. All mechanisms must improve efficiency of oxygen delivery to brain over time. Cerebral dysfunction what mainly limits aggressive ascent profiles.

12 The Spectrum of Altitude-associated Neurological Disease (SAAND) By far the most common form of altitude illness (100% incidence above 8000m) S A A N D High Altitude Headache (HAH) Acute Mountain Sickness (AMS) High Altitude Cerebral Edema (HACE) Don t forget High Altitude Pulmonary Edema!

13 Risk Factors for Altitude Sickness Genetic susceptibility ELGN/HIF-1 EPAS1/HIF-2 PPAR Altitude of residence (<3000 ft) Hydration status Activity level/exertion Illness: Colds, heart/ lung/blood/brain Dz

14 Risk Factors for Altitude Sickness Rate of ascent: #1 cause of altitude sickness. Above 10K ft sleep no higher than 1000 ft above previous camp Maximum altitude achieved. 100% with altitude sickness at 8000 m Sleeping altitude. Climb high, sleep low Olympic training

15 High Altitude Headache Among most common complaints at altitude, & most common neurological Symptoms. Often a benign isolated syndrome. Sentinel symptom of acute mountain sickness (SAAND).

16 Acute Mountain Sickness Requires Headache in unacclimatized person recently arrived at >8K ft and one or more of: Fatigue/excessive exhaustion Dizziness/lightheaded Anorexia nausea vomiting Insomnia (not periodic breathing) Pearls: Think hangover Note rarely headache absent 1991 Lake Louise AMS Consensus Guideline

17 AMS and HAH Are Very Common How common is HAH? HAH: 8-10K ft, 47-62% incidence, EBC >90%. How about AMS? 15-30% Colorado resort skiers. 50% Mt. McKinley climbers. 70% Mt. Rainier climbers % Everest BC trekkers. Who gets AMS and HAH? Young, fit males. Think fast ascent rate to high altitude. Individual susceptibility widely varied. Vigorous exercise.

18 High Altitude Cerebral Edema (HACE) Think end-stage SAAND. Components: Severe headache (bad AMS) Confusion/disorientation Walking difficulties/clumsiness (widened gait) Unusual behavior Coma and death common if untreated!

19 Most common cause of death from altitude, 50% mortality rate % incidence. Tips: Very rare below 12K ft. Often hrs after onset of AMS. ALL have preceding AMS. Patient looks drunk. Frequently occurs with HAPE (up to 80%). HACE Is Rare

20 Hackett et al. JAMA 1998 Sea level to 5200m in 6 days confusion/ataxia T2 weighted MR on arrival T2 weighted MR 11 months later

21 High Altitude Pulmonary Edema (HAPE) Early HAPE: Exercise intolerance usually with a dry cough Continued shortness of breath at rest (low oxygen saturation) Rapid breathing and pulse Late-stage HAPE: Fluid in lungs (gurgling) Cyanosis (blue/dusky lips) Unconsciousness & death

22 HAPE Is Less Common Most common cause of dangerous altitude sickness. Affects 0.6-4% persons who rapidly ascend to greater than 12K ft and remain. Begins hrs after arrival. Prior history (20-60% risk).

23 Misc. Neurologic Problems at Altitude Retinal micro hemorrhages. approach 100% at 8000m. Decreased night vision. Periodic breathing (Cheyne-Stokes). Sleep disordered breathing. Behavioral changes. depression/anxiety. High altitude flatulence expulsion (HAFE). Gasses expand at altitude, neuroenteric dysfunction.

24 Best Prevention is A Staged Ascent Tested method by mountaineers on expeditions. Climb high sleep low. Above 10,000, sleep no higher than 1000 above the previous camp. Additionally, spend 2 nights at the same altitude every 3 nights.

25 Other Preventive Measures Avoid substances that depress respiration: Alcohol Narcotics Sleeping pills Hi carb diet (over 70%). Take it easy (talk & walk). Drink lots of fluids (2 L adult). Get older (brain shrinkage). Weak/no evidence: Gingko biloba Vitamin C/antioxidants Milk thistle, glutamine (?)

26 Treatment of Mild to Moderate AMS Rest and stop ascent. Treatment of Symptoms. Ibuprofen for headache. Acetazolamide/ Diamox: 250 mg 2-3/day (prescription) Compazine for nausea (prescription) Hydrate. Hi carb bland diet may help.

27 Role of acetazolamide (Diamox) Speeds up acclimatization by ~50%, fairly fast treat AMS as well. Preventive for rapid ascents (rescue, etc). Preventive for those w/ past AMS. Likely prevents HACE (HAPE?). Prevention: mg 2x/day begin 1 day prior to ascent and take till your high point achieved. Treatment for moderate AMS: 250 mg 3x/day for 2-3 days. Not for those allergic to sulfa. Many side effects: Paresthesias Dysgeusia (taste disturbance) Polyuria Trial dose prior to a big trip advisable.

28 Treatment Of Severe AMS, HACE, & HAPE RAPID DESCENT! Early recognition is key. Mandatory and immediate descent (2K ft or more if possible). Oxygen and/or Gamow bag. Dexamethasone/Decadron (steroid) if available. If nonambulatory, helicopter evacuation likely necessary. Viagra?? (worsens headaches).

29 The Gamow bag: a portable hyperbaric chamber Pump up around affected person. 15 lb, yield a 6000 drop in elevation with 2 psi. Observation windows. Now use portable oxygen concentrators.

30 Conclusion: 5 Golden Rules of Going to Altitude

31 1. It is ok to get altitude illness. It is Not ok to die from it.

32 2. Any illness at altitude is altitude illness until proven otherwise.

33 3. Never ascend with symptoms of AMS.

34 4. If you are getting worse, go down at once.

35 5. Never leave someone with AMS Alone.

36 Honorary Golden Rules: Be Prepared, and know when to back down

37 Thank you and climb safely