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Return to High Altitude After Altitude Illness

VIEWS: 3 PAGES: 48

									Military Sports Medicine Fellowship

“Every Warrior an Athlete”

Return to High Altitude Activity After High Altitude Illness
Kevin deWeber, MD, FAAFP Director, Primary Care Sports Medicine Fellowship

Objectives
• Review pathophysiology of high altitude illness (HAI) • Review the types of HAI and how they are treated • Review factors predisposing to HAI • Discuss preventive treatment for those with a remote history of HAI • Discuss factors in return-to-altitude decisions after recent HAI

Preview
• Little evidence for recommendations of return to altitude activity after HAI • Acclimatization and slow ascent are powerful
– Ascend < 600 m/day – Rest day every 600 – 1200 m

• Prophylactic meds advised if unable to comply • Consider neuro-psych deficits from moderate AMS/HACE and their effect on activity

Environment at high altitude (>1500 m or 4920 ft)
• Barometric pressure decreases • Partial pressure of oxygen decreases

• RESULT: ―Hypobaric Hypoxia‖
– Lower alveolar O2 leads to lower SaO2

Ft. Carson, CO, ~6500 ft Pikes Peak, 14,110 ft (4300 m)

US Air Force Academy, ~7,000 ft

Acclimatization = body’s adaptation to hypobaric hypoxia

Acclimatization
• Immediate (minutes to hours)
– ↑ Sympathetic tone  ↑ HR & CO – ↑ Ventilation  ↑ PaO2 and ↓ PaCO2  ↓ pH – Renal bicarbonate diuresis (to balance pH) – ↑ Pulmonary artery pressure  ↑ O2 absorption

• Delayed (days to weeks)
– Erythropoietin  ↑ RBC production – Remodeling of pulmonary arterioles

Altitude Illnesses
(Failure to Acclimatize)
• Cerebral Syndromes
– Acute Mountain Sickness (AMS) – High Altitude Cerebral Edema (HACE)
mild AMS moderate AMS HACE

• Pulmonary Syndrome
– High Altitude Pulmonary Edema (HAPE)

• Importance
– HACE and HAPE can be fatal

Acute Mountain Sickness (AMS)
• Defined as HEADACHE plus one or more symptom:
– Anorexia, nausea or vomiting – Fatigue or weakness – Dizziness or lightheadedness – Difficulty sleeping

Effects of AMS on performance
• Mild: annoyance only • Moderate: impaired concentration, memory, speech, and physical performance;
– Can be disabling – Subtle abnormalities visible on MRI – Effects can last weeks

High Altitude Cerebral Edema (HACE)
• • • • AMS symptoms plus ALTERED L.O.C. and ATAXIA Other neuro findings possible Coma develops Death results if untreated

• Pathophysiology
– altered cerebral vascular permeability leads to brain swelling – MRI: cerebral edema, lesions of corpus callosum

High Altitude Pulmonary Edema (HAPE)
• Defined by two pulmonary symptoms…
– Cough, dyspnea at rest, exercise intolerance, chest tightness/congestion…

• and two pulmonary signs…
– Crackles, wheezing, cyanosis, tachypnea, tachycardia

• Most common cause of death among HAI
– 50% mortality rate if not treated quickly

High Altitude Pulmonary Edema (HAPE)
• CXR findings
– Blotchy fluffy infiltrates

• Pathophysiology
Hypoxia  pulmonary artery hypertension alveolar damage  edema and hemorrhage into alveoli

Risk factors for HAI
• Rapid gain in altitude • Prior history of HAI
– genetic factors involved

• Alcohol, sedatives • HAPE: cold ambient temperature • Strenuous exercise

HAI Protective Factors
• Residence at elevation >900 m (2950 ft) • Slow gain in elevation
– <600 m (1970 ft) per day in sleeping elevation

• Genetic factors • Vigorous fluid intake • Physical fitness NOT protective

Treating HAI
• Rest, halt ascent • Descent
– Moderate AMS: >500 m (1640 ft) – HACE: > 1000 m (3280 ft) – HAPE: 500 – 1000 m

• Oxygen if available • Keep warm (esp. for HAPE) • Portable hyperbaric chambers

Portable Altitude Chamber® (PAC)

Gamow® bag

Certec® bag

Treating HAI (cont.)
• Acetazolamide
– Speeds acclimatization – 75% effective in preventing AMS – Treats moderate AMS & HACE – Dose: 125-250 mg BID

Treating HAI (cont.)
• Dexamethasone
– Decreases cerebral edema – Treats moderate AMS and HACE – Prevents AMS, ? HACE – Dose
• 2 mg po/IM/IV QID • 4 mg BID

Treating HAI (cont.)
• Nifedipine
– Decreases pulmonary artery pressure – Prevents and treats HAPE – Dose: 20 – 30 mg extended release BID

Treating HAI (cont.)
• Salmeterol
– Decreases alveolar fluid transport – Prevents and treats HAPE – Dose: 125 mcg inhaled BID

Considerations for Return to Altitude Activity after HAI
• Severity and type of prior HAI • Future ascent requirements • Feasibility of descent/extra rest days if needed • Availability of medical treatments

Two scenarios for Return to Altitude Activity after HAI

1. Remote history of HAI, fully recovered 2. Recent HAI, with/without recovery

1. Remote history of HAI, fully recovered
• Proper acclimatization protocols are paramount
– Ascend no more than 600 m (1970 ft) per day in sleeping altitude when >2500 m (8200 ft) – Spend one extra night every 600-1200 m (1970 – 3937 ft) – Avoid abrupt ascent to >3000 m (9843 ft) – Spend 2-3 nights at 2500-3000 m before ascending further

―Acute mountain sickness: influence of susceptibility, preexposure, and ascent rate‖
Incidence of AMS (%) during ascent to 4559 m in persons with a prior history of AMS
60 50 40 30 20 10 0 7 Pre-exposure AND slow ascent 33 29 Pre-exposure 58 Normal ascent rate and no pre-exposure Slow ascent

Schneider M et al. Med Sci Sports Exerc 2002

Prevention of recurrent AMS
• Proper acclimatization, slow ascent.
If not possible…

• Acetazolamide 125-250 mg po BID starting 1 day prior to ascent, continuing until at max altitude for 2 days. If not possible… • Alternate: Dexamethasone 2 mg po QID or 4 mg BID, starting 1 day prior, cont. until at max altitude 2 days • Unknown which is better or if combination therapy is indicated

Prevention of recurrent HACE
(No evidence-based recommendations) • Strong recommendation for acclimatization and slow ascent.
If not possible, or descent/medical treatment not possible…

• Prophylaxis with acetazolamide or dexamethasone, as for AMS

Prevention of recurrent HAPE
• The power of slow ascent: case series
– 4 climbers with history of 2-4 prior cases of HAPE each – Made a collective 7 ascents to > 5000 m (16,400 ft) – Acclimatized fully – Ascended only 330-350 m (984-1150 ft) a day – RESULT: no cases of HAPE (100% effective)
Bärtsch P et al. High altitude pulmonary edema. Respiration 1997

Prevention of recurrent HAPE (cont.)
• The power of meds: 1 R, DB, PC trial comparing prophylactic meds
– Dex 8 mg bid – Tadalafil 10 mg bid
80 70 60 50 40 30 20 10 0 Placebo Tadalafil % w/ HAPE

• Dex & tad vs placebo:
– P < 0.001 & < 0.007 – Dex vs tab: not sig

• Both dex & tad reduced pulmonary artery pressure

Prophylaxis for recurrent HAPE
• Strong recommendation for acclimatization and slow ascent.
If not possible, or descent/medical treatment not possible…

• Prophylactic options:
– – – – – Tadalafil 10 mg po bid Dexamethasone 8 mg po bid Acetazolamide 125-250 mg po BID Salmeterol 125 mcg inhaled BID Nifedipine 20-30 mg XR BID
– All beginning 1 day before ascent

No evidence of superiority of one agent or risks/benefits of combination therapy

2. Return to Altitude Activity after Recent HAI
• Considerations (same as remote HAI hx)
– – – – Severity and type of prior HAI Future ascent requirements Feasibility of descent/extra rest days if needed Availability of medical treatments

• Additional considerations for recent HAI
– Should the patient fully recover before returning to altitude/activity? – How safe is continued activity at altitude? – Should activities be limited?

Treatment of Mild AMS
• Descend > 500 m (1640 ft) OR • Rest 1-2 days at same altitude • Oxygen 12-24 hours, if available • Consider acetazolamide 125250 mg po BID • Symptomatic treatment with analgesics, anti-emetics

Return to Altitude Activity during/after Mild AMS
(No evidence-based recommendations) • Common practice: continue activity despite symptoms • Risks
• Impaired cognition/performance • Progression to moderate AMS or HACE

• Consider acetazolamide

―To air is human: altitude illness during an expedition length adventure race‖
• 10-day, 238-mile race at elevations of 9,500 – 13,500 ft • No prophylaxis allowed • 33 cases of AMS treated during race
– 88% were returned to race – 58% finished race (compared to 74% overall)

• CONCLUSION: untreated AMS probably reduces athletic performance
Talbot TS et al. Wilderness Environ Med 2004

Treatment of Moderate AMS
• Descend >500 m • Rest 1-2 days • Do not allow continued ascent/activity
– Significant performance/cognition decrement – Risk of progression to HACE

• Oxygen 1-2 days, if available • Acetazolamide; dex as alternate

Return to Altitude Activity after recovery from Moderate AMS
(No evidence-based recommendations) • Strict adherence to acclimatization and slow ascent protocols
– Ascend no more than 600 m/day – Rest day every 600 – 1200 m

• Consider acetazolamide (or dex) • Counsel on recognition and rapid treatment of HACE/HAPE

Treatment of HACE
• Immediate descent > 1000 m and hospitalize • Oxygen to maintain SaO2 >90% • Dexamethasone—8 mg PO/IM/IV initially followed by 4 mg QID • Portable hyperbaric therapy if descent impossible

Treatment of HACE (cont.)
• Management of coma
– Bladder catheterization – Airway control

• Diagnostic studies
– CXR to rule out concurrent HAPE – MRI to rule out other conditions

Recovery from HACE: highly variable
• 1-3 days for symptoms to resolve • Days to 12 weeks for neuropsychological function to normalize • 3-4 weeks for papilledema to resolve • Days to 5 weeks for MRI to normalize

Return to Altitude Activity after recovery from HACE
(No evidence based recommendations) • Full recovery highly advised • Strict adherence to acclimatization and slow ascent protocols
– Ascend < 600 m/day – Rest day every 600 – 1200 m

• Consider prophylaxis
– Acetazolamide; dex as alternate

Treatment of HAPE
• Immediate descent 500-1000 m

• Oxygen to keep SaO2 >90%. • If descent/O2 not immediately available…
– Portable hyperbaric therapy – Nifedipine 20-30 mg extended release BID (avoid if concomitant HACE) and/or… – Salmeterol 125 mcg inhaled

Treatment of HAPE (cont.)
• Admit if:
– >4L/min O2 requirement – Elderly, very young – Concomitant HACE or co-morbid cardiopulmonary disease
• Dexamethasone if concomitant HACE

• Low-flow outpatient O2 for others; check daily

Recovery from HAPE
• Variable; little evidence in literature • May take 2 weeks to recover strength • Resume some activity when SaO2 > 90% without supplemental O2 • Remaining at some altitude fosters acclimatization via pulmonary arteriolar remodeling

―Reascent following resolution of high altitude pulmonary edema (HAPE).‖
• Case reports of 3 mountaineers with HAPE • Treated with…
– descent to lower altitude – oxygen – rest 2-3 days

• Resumed ascent; no prophylaxis
– < 600 m/day ascent; several rest days

• RESULT: all reached peaks w/o HAPE
– One reached summit of Mt. Everest at 8850 m (29,035 ft)
Litch JA, Bishop R. High Alt Med Biol 2001 Spring;2(1):53-5

Return to Altitude Activity after recovery from HAPE
(No evidence based recommendations) • Strict adherence to acclimatization and slow ascent protocols
– Ascend < 300 - 600 m/day – Rest day every 600 – 1200 m

• Consider prophylaxis:
– acetazolamide and/or – nifedipine or salmeterol (especially if ascent will be > 600 m/day)

Review
• Little evidence for recommendations of Return to Altitude Activity after HAI • Acclimatization and slow ascent are powerful
– Ascend < 600 m/day – Rest day every 600 – 1200 m

• Prophylactic meds advised if unable to comply • Consider neuro-psych deficits from moderate AMS/HACE and their effect on activity

Thank you!


								
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