David A. Connett, DO, FACOFP, dist

Transcription

1 David A. Connett, DO, FACOFP, dist

2 Disclosures Nothing to disclose including pharmaceuticals

3 High Altitude Syndromes Acute Mountain Sickness (AMS) High Altitude Cerebral Edema (HACE) High Altitude Pulmonary Edema (HAPE) Decompression Sickness (DCS)

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5 High Altitude High Altitude-5,000 feet to 11,500 feet ( m) Highest U.S. ski resorts Minor impairment of arterial oxygen transport arterialsao2> 90% AMS common with rapid ascent above 8000 feet Very High Altitude-11,500 feet to 18,000 feet ( m) High peaks in the lower 48, Europe Maximum arterial SaO2 < 90%, PAO2<60 torr Most common range for serious altitude sickness Extreme Altitude-over 18,000 feet (above 5500 m) Denali, Himalaya, Karakoram, Andes Marked hypoxemia and hypercapnia

6 Oxygen Levels at Altitude

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8 Environment at High Altitude Barometric pressure falls with increasing altitude in logarithmic fashion Partial pressure of oxygen decreases resulting in hypoxia Altitude changes with distance from equator, hypoxia worse at the poles. Pressure is lower in winter than in summer. Temperature decreases with altitude 1000 feet for every 3.56 F Ultraviolet light increases by 4% every thousand feet

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10 Pathophysiology Acute Mountain Sickness

11 Hypoxic Ventilatory Response (HVR)

12 Pathophysiology Acute Mountain Sickness

13 Pathophysiology of HAPE

14 Pathophysiology of HAPE Components of endothelial activation/dysfunction in acute lung injury (ALI). This schematic cartoon illustrates the components of endothelial activation including 1) Endothelial cell-leukocyte interactions, 2) Endothelial cell-platelet-neutrophil interactions, and 3) Structural changes between endothelial cells. RBC, red blood cell; MLCK, myosin light chain kinases; PASMC, pulmonary artery smooth muscle cell.

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16 Pathophysiology of HAPE

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18 Factors Increased by Acclimatization Acute Ventilation Heart rate Cerebral blood flow Diuresis increased hematocrit Chronic Increase in pulmonary ventilation Increase and diffusing capacity in the lung Red blood cell count due to erythropoietin Metabolism (tissue changes over years) Increase in the number of mitochondria Augmentation of the cytochrome oxidase system

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20 Acclimatization to High Altitude Rapid ascent and exposure to the altitude at the summit of Mount Everest 29,028 feet results in loss of consciousness in a few minutes and death shortly thereafter. Acclimatization occurs over time Ability to acclimatize varies from individuals Just a few days at sea level may make one susceptible to AMS or HAPE

21 Other Aids to Acclimatization Climb high. Sleep low. High carbohydrate diet Mild exercise-avoid exertion Avoid alcohol and sleeping medications

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23 Lake Louis Consensus definitions of High Altitude Acute Mountain Sickness In the setting of a recent gain in altitude, there is precedence of headache and at least one of the following: Gastrointestinal (anorexia, nausea or vomiting) Fatigue or weakness Dizziness or lightheadedness Difficulty sleeping

24 Acute Mountain Sickness Rapid ascent to 8200 feet from altitudes below 5000 feet for unacclimatized Headache Throbbing, by temporal or occipital worse at night Fatigue Dizziness/lightheadedness Anorexia and nausea Difficulty sleeping

25 Mild Acute Mountain Sickness Mild Headache Insomnia Shortness of Breath while Exercising May continue climbing More time for acclimatization

26 Moderate Acute Mountain Sickness Headache may be severe Some lassitude Weakness Loss of appetite Nausea Beginning to lose coordination - ataxia Begin to descend

27 Acute Mountain Sickness Differential Diagnosis Viral illness Hangover Exhaustion Dehydration Hypothermia Sedatives/hypnotic medications Carbon monoxide

28 Acute Mountain Sickness Usually self-limited If untreated may persist for weeks May precede HACE or HAPE Responds well to treatment

29 Lake Louis Consensus definitions of High Altitude High Altitude Pulmonary Edema (HAPE) In the presence of a recent gain in altitude, the presence of the following: Two of the following symptoms: Dyspnea at rest Cough Chest tightness or congestion At least two of the following signs: Crackles or wheezing and at least one lung field Central cyanosis Tachypnea Tachycardia

30 High Altitude Pulmonary Edema The most common cause of death from high-altitude illness. Most often after second night at new altitude Apparent abrupt onset May occur in the absence of Acute Mountain Sickness

31 HAPE Symptoms and Signs Early symptoms: fatigue, weakness, dyspnea on exertion, dry cough Progression to tachycardia, tachypnea, and orthopnea and dyspnea at rest marked shortness of breath even at rest Pink or blood-tinged sputum is a very late finding Crackles usually start in right axilla May also have headache, lassitude, reduced urine output, peripheral edema and ataxia.

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33 Distribution of Symptoms and signs in 154 Trekkers Nepal with AMS Severity Percent Symptoms Mild 65 Headache, anorexia, nausea and malaise Moderate 30 Unrelieved headache, vomiting, reduced urine output Severe 5 Altered consciousness, ataxia, rales, cyanosis, dyspepsia at rest, possible papilledema

34 Incidents of Altitude Illness in Various Groups Study Group Number at Risk per Year Sleeping Altitude (feet) Maximum Altitude Reached (feet) Average Rate of Assent (days low altitude) Percent with AMS Percent with HAPE and/or HACE Western State Visitors 30 million 6500 ft ft. >9800 ft. 11,500 ft Mount Everest ,000 ft. 1-2 (fly in) 10-13(walk) Mount Denali ,321 feet Mount Rainier ,409 ft Indian soldiers Unknown 18,000 ft

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36 Lake Louis Consensus definitions of High Altitude High Altitude Cerebral Edema (HACE) Can be considered end-stage or severe acute Mountain sickness. In the setting of a recent gaining altitude there is either: The presence of a change in mental status and/or ataxia in a person with Acute Mountain Sickness Or the presence of both mental status changes and ataxia any person without Acute Mountain Sickness

37 High Altitude Cerebral Edema Progression of cerebral signs and symptoms of Acute Mountain Sickness Headache, vomiting Truncal ataxia (other focal neurologic deficits may also occur) Severe lassitude Altered consciousness or coma Weakness or paralysis on one side of the body Amnesia or hallucinations Especially common with High Altitude Pulmonary Edema - Shortness of breath, dry cough

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40 High Altitude Cerebral Edema Early Symptoms Headache Anorexia Nausea Emesis Photophobia Fatigue Irritability Decrease socialization Late Symptoms Ataxia (appendicular to truncal) Irrationality Hallucinations Visual disturbances Focal neurological deficits Abnormal reflexes

41 Other Altitude Related Disorders High-altitude retinopathy maintain good fluid intake to reduce hemoconcentration, spontaneously resolves Peripheral edema treat with a diuretic in the absence of AMS, HACE or HAPE; condition spontaneously resolves on descent Venous stasis and thrombotic complications stay active keep well hydrated and descend if needed Altitude pharyngitis and bronchitis suck on hard candy, brie through a facemask and drink plenty of fluids Ultraviolet keratitis ( snow blindness) remove contact lenses, patch affected eye, use oral analgesics to decrease pain; prevented by wearing sunglasses

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43 Acute Mountain Sickness Management The Golden Rules # 1 AMS symptoms at altitude are AMS until proven otherwise # 2 Don t ascend further if you have symptoms # 3 Descend if very ill or not improving. Descend immediately for ataxia or decreased consciousness #4 Don t let anyone with AMS descend alone

44 Prevention Acute Mountain Sickness Prevention Acetazolamide (Diamox) 125 mg twice a day (or 500 mg slow release daily) Start 12 hours before assent Continue first day at altitude Sleep Acetazolamide (Diamox) mg at dinner time

45 Treating Acute Mountain Sickness The mainstay of treatment of AMS is rest, fluids, and mild analgesics: acetaminophen (Tylenol), aspirin, or ibuprofen. These medications will not cover up worsening symptoms. The natural progression for AMS is to get better, and often simply resting at the altitude at which you became ill is adequate treatment. Improvement usually occurs in one or two days, but may take as long as three or four days. Dehydration is a common cause of headache at altitude. Drink one liter of fluid, and take acetaminophen or aspirin. If the headache resolves quickly and totally (and you have no other symptoms of AMS) it is very unlikely to have been due to AMS. Descent is also an option, and recovery will be quite rapid.

46 Treatment Mild Acute Mountain Sickness Stop ascent, rest, acclimatize at same altitude Acetazolamide, 125 to 150 mg twice a day, to speed acclimatization Symptomatic treatment as necessary with analgesics and anti-medics or Descend 1500 feet or more

47 Treatment Moderate Acute Mountain Sickness Low-flow oxygen, if available Acetazolamide, 125 two 250 mg twice a day with or without Dexamethasone, 4 mg PO,IM, IV q 6hr Hyperbaric therapy or Immediate descent

48 Instant Descent Inside a Bag 0.14 atmosphere (102 torr) above ambient pressure 14,000 feet simulates 8000 feet CO2 buildup minimal if used properly (and maybe helpful)

49 Treatment HAPE Minimize exertion and keep warm Oxygen, 4 to 6 L/min until improving it, then 2 to 4 L/min Dexamethasone, 4 mg PO,IM, IV q 6hr

50 HAPE Prevention Graded ascent Nifedipine for HAPE susceptibles 20 mg orally every eight hours or 30 mg every 12 hours-starting 24 hours before arrival and continuing for three days

51 HAPE Prevention Tadalafil and Sildenafil Phosphodiesterase-5 (PDE-5) inhibitors that augment the pulmonary vasodilatory effects of nitric oxide by blocking the degradation of cyclic guanosine monophosphate (cgmp), the intracellular mediator of nitric oxide. Nitric oxide is a potent pulmonary vasodilator and reduces hypoxic pulmonary vasoconstriction (HPV) and pulmonary hypertension in HAPE. Both Tadalafil and sildenafil have been shown to be effective as prophylaxis for HAPE, but neither has been studied as treatment. Nevertheless, based upon their mechanism of action, both Tadalafil and sildenafil may be effective adjunct treatments for established HAPE when neither oxygen nor descent is available options. These drugs may have advantages over nifedipine because they lower PA pressure with less risk of lowering systemic blood pressure. The appropriate dose for treatment is unknown but might be similar to that used for prophylaxis (Tadalafil 10 mg by mouth every 12 hours; sildenafil 50 mg by mouth every eight hours).

52 HAPE Prevention Dexamethasone 8 mg every 12 hours (also helps to prevent Acute Mountain Sickness) Tadalafil 10 mg every 12 hours (no benefit for Acute Mountain Sickness) Salmeterol 125 µg every 12 hours (some benefit for Acute Mountain Sickness) All regimes start 24 hours prior to assent and continue at altitude

53 Other Drugs to Prevent Acute Mountain Sickness Dexamethasone Indicated with contraindication to Acetazolamide Also used in conjunction with acetazolamide for rapid ascent above 10,000 feet (rescue) Dosage 4 mg every six hours

54 Treatment HACE Immediate descent or evacuation Oxygen, 2 to 4 L/min Dexamethasone, 4 mg PO,IM, IV q 6hr Hyperbaric therapy

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56 Indications for Acetazolamide Rapid ascent to altitudes over 10,000 feet Past history of recurrent Acute Mountain Sickness Treatment of Acute Mountain Sickness Periodic breathing or poor sleep

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58 High Altitude Medical Contraindications/Cautions Contraindications Uncompensated left heart failure Pulmonary hypertension Sickle cell anemia Moderate-severe COPD Seizure disorders Cautions History of left heart failure Cardiac arrhythmias Cerebral vascular disease Sleep apnea Sickle Trait

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60 Distribution of DCS

61 Decompression Sickness Decompression sickness (DCS) results from the formation of nitrogen bubbles in the tissues or circulation as a result of inadequate elimination of nitrogen after a dive. The formation of nitrogen bubbles may occur following a dive and ascending to high altitudes in a short period of time to include a pressurized commercial aircraft. Bubbles that form are trapped in the joints called the bends. Bubbles that are formed in circulation may become trapped in the brain or spinal cord resulting in serious neurological compromise or death. DCS may also occur in very high altitudes with aircraft or spacecraft without a dive to precipitate the response.

62 Decompression Sickness Limb Bends Central Nervous System (CNS) DCS Cerebral Decompression Sickness Pulmonary DCS Skin Bends Inner Ear Decompression Sickness

63 Gas Laws - Dalton and Henry Dalton s Law - in a mixture of nonreacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases. Henry s Law - the amount of dissolved gas is proportional to its partial pressure in the gas phase. In diving more gas is dissolved in solution when at pressure.

64 Decompression Sickness

65 Boyles Law - Air Embolism vs Bends

66 Air Embolism Gas (air) entry into the circulation from ruptured pulmonary veins or patent foramen ovale Air bubbles travel in the arterial blood supply and the tissues Air bubbles become lodged in tissues blocking blood flow

67 Air Embolism Occurs within 2-3 minutes Cardiac arrest or arrhythmias Neurological focal paralysis, sensory disturbance, seizures, altered mental status

68 Physiological Atmospheric Divisions

69 Pathophysiology of Bubbles in DCS

70 Dive Table Pushing Your Tables

71 Altitude Decompression Risk Assessment

72 Altitude Decompression Risk Assessment

73 Classification DCS

74 Principle Factors for DCS Two principal factors control the risk of a diver suffering DCS: 1.The rate and duration of gas absorption under pressure the deeper or longer the dive the more gas is absorbed into body tissue in higher concentrations than normal (Henry's Law); 2.The rate and duration of outgassing on depressurization the faster the ascent and the shorter the interval between dives the less time there is for absorbed gas to be offloaded safely through the lungs, causing these gases to come out of solution and form "micro bubbles" in the blood. Even when the change in pressure causes no immediate symptoms, rapid pressure change can cause permanent bone injury called dysbaric osteonecrosis (DON). DON can develop from a single exposure to rapid decompression. Risks at Altitude 1. Can happen over 18k ft, especially repeated ascents 2. Is a substantial risk over 30k ft. 3. Is a much greater risk after diving. 4. Risk is related to altitude and rate of ascent. 5. In gliders, is a risk in wave flights. 6. In pressurized aircraft, is likely in depressurization accidents. 7. Can results in permanent injury. 1. Must seek a bariatric physician ASAP % oxygen rebreathing

75 Symptoms Frequency and Onset

76 Skin Bends

77 Spinal Cord Bends Infarction of Cord

78 Bends Prevention

79 DCS Management

80 DCS Management US Navy Table 6

81 DCS Management

82 Important Safety Tip

83 Questions