Mountain Health Awareness Surg Cdr Andy Brown, Lt Col Pete Davis and Surg Cdr A Mellor

1. Mountain Health AwarenessSurg Cdr Andy Brown, Lt Col Pete Davis and Surg Cdr A Mellor

2. Definitions Intermediate Altitude (1500m – 2500m)Physiolgical changes occur, SpO2>90%, altitude illness possible but rare High Altitude (2500m – 3500m) Altitude illness common with rapid ascent Very High Altitude (3500m – 5800m)Altitude illness common, SpO2<90%, marked hypoxia with exercise Extreme Altitude (>5800m)Marked hypoxia at rest, progressive deterioration, permanent survival not possible

3. General • Physical Fitness • The fitter an individual, the easier it is to perform in a mountainous environment (but will not prevent altitude illness) • Nutrition • More than at sea level • Water Intake • 6 to 8 litres of water per day • Good Attitude

4. Heat Generation • 25% of food that we eat is used by body to rebuild itself and 75% is used to produce heat • Diet • Caloric intake • 4,500 calories per day • Carbohydrate intake • Simple carbs like sugars, bread, rice and pasta are more easily converted into energy and taste good • Hot meals and hot wets

5. The body at rest produces heat at a specific rate • Moderate exercise • Increases heat production 5 to 6 times normal rate and can be tolerated for long periods of time • Moderate shivering • Increases heat by 20 times normal rate but only for a few minutes. This quickly leads to exhaustion. • Intense shivering • Increases heat production by 50 times normal rate but exhaustion follows within 30 seconds

6. 5 Ways the Body Loses Heat • Radiation • Heat loss from the body to it’s surroundings • Conduction • Heat transfer from one object in contact with a colder object • Convection • Heat loss to a gas or liquid running over the body

7. Evaporation • Heat loss when water (sweat) on the surface of the skin in turned into water vapour • Respiration • Heat loss when you inhale in cold air and your body warms it up • Heat loss when you exhale warm air from your body

9. Physical Responses to Heat • Blood vessels in the skin open up or dilate • Allows more blood to the surface where the heat can more easily be transferred to the surroundings (Radiation) • Sweating begins • Heat loss through convection and evaporation • Heart rate and breathing increases • Pushes blood to the skin surface and brings more air in to which more heat can be added

10. Physical Responses to Cold • Blood vessels at the skin surface close down or constrict • Occurs so that body loses less heat to the surroundings • More blood goes to the core of the body leaving the extremities with a higher tendency to get cold

11. Shivering • Body is trying to warm itself up • Body produces more urine • Kidneys are fooled into thinking the body has more blood than it really does due to the fact that the body is bringing in the blood to the core of the body. • Kidneys respond by producing more urine which can contribute to dehydration

12. Dehydration • Defined as a deficit of total body water • Causes • Excessive loss • Urination • Cold, dry air • Strenuous activity • Coffee and tea?? • Inadequate intake • Thirst • Water inaccessibility

13. Symptoms of Dehydration • Headache • Nausea • Dizziness • Fainting • Constipation • Dry mouth • Weakness • Lethargy • Stomach cramps • Leg and arm cramps

14. Signs of Severe Dehydration • Only show when severe!!! • Swollen tongue • Dark urine • Low blood pressure • Rapid heart rate • Greater than 100 per minute

15. Prevention of Dehydration • Adequate intake • Drink 6 – 8 litres of water per day • Try to keep your urine light coloured • Do not rely on thirst as an indicator

16. Heat Cramps • Painful spasms of skeletal muscle as a result of excessive loss of body salt • Cause • Salt imbalance within the body • Symptoms • Muscle cramps in the arms, legs, or abdomen

17. Heat Cramps • Prevention • Avoid overheating • Eat correctly • No need for salt tablets as normal diet contains more than enough salt • Field Management • Have victim stop moving • Gentle massage of effected area • Add 1 tablespoon of table salt to a litre of water and drink. Repeat as necessary.

18. Heat Exhaustion • Occurs when body salt losses and dehydration from sweating are so severe that a person can no longer maintain an adequate blood pressure. • Causes are sweating and dehydration combined with strenuous physical activity

19. Symptoms of Heat Exhaustion • Headache • Nausea • Dizziness • Fatigue • Fainting

20. Heat Exhaustion • Prevention • Same for heat cramps • Dress properly with adequate ventilation • Dress comfortably cool • Frequent ventilation stops • Field Management • Lay patient down with feet higher than his head • Keep patient well ventilated • Give plenty of water to drink, or via iv if severe

21. Heat Stroke • Failure of the body’s cooling mechanism that rids the body of excessive heat • Lethal in up to 40% of cases • Those who live may suffer permanent brain damage

22. Symptoms of Heat Stroke • Headache • Nausea • Dizziness • Fatigue

23. Signs of Heat Stroke • Patients are delirious or comatose • Pupils may be pinpoint • Flushed skin may or may not be present • Rectal temperature of 39 oC • Sweating is often present. It is often taught that sweating is absent. THIS IS UNTRUE.

24. Preventive Measures for Heat Stroke • Same principles as heat exhaustion • Drink plenty of water • Stay well ventilated • When temperature and humidity are high, physical activity must be reduced.

25. Field Management for Heat Stroke • Reduce heat immediately • Maintain an open airway • Remove as much of the patient’s clothing as possible • You may immerse the victim in a cold stream as long as the airway is clear • Give him nothing by mouth

26. Field Management for Heat Stroke • When rectal temperature is below 38 oC, you may discontinue cooling. Recheck temperature every 10 minutes. If temperature rises above 39 oC again, begin re-cooling again • Casevac ASAP

27. Altitude related issues

28. What’s the problem? At high altitude atmospheric pressure reduces The % oxygen stays the same The pressure of oxygen is less This leads to hypoxia – reduced oxygen levels

29. Measuring hypoxia Pulse oximtery Measures how much haemoglobin is carrying oxygen Usual reading about 96%- 99% At sea level readings under 94% associated with illness Readings less than 90% in a fit healthy person would result in ICU admission

30. Measuring hypoxia Pulse oximtery Measures how much haemoglobin is carrying oxygen Usual reading about 96%- 99% At sea level readings under 94% associated with illness Readings less than 90% in a fit healthy person would result in ICU admission

31. Pulse oximeter

32. Effect of Altitude of SpO2 5 Apr 20 Apr 3 Apr 16 Apr 8 Apr

33. Sleep at altitude • Sleep is disturbed! • There is an increased rate of breathing then a pause • Pauses in breathing can last up to 9s • Improved with acetazolamide • This will be noticed in tent partners but is not, in itself, dangerous!

34. Other changes Breathing rate increases – a lot Heart rate increases at rest There is an increased need to pass urine ALL THESE ARE NORMAL CHANGES AND PART OF ACCLIMATISING

35. Altitude Related Illness • Acute Mountain Sickness (AMS) • High Altitude Cerebral Oedema (HACE) • High Altitude Pulmonary Oedema (HAPE)

36. Global Incidence of AMS Barry, P W et al. BMJ 2003;326:915-919

37. Predicting AMS Positive predictors Previous history of high altitude illness Exertion Co-existing infections e.g. ‘flu’ Permanent residence below 900 m altitude No influence Gender Age Physical fitness Coronary artery disease Chest disease such as asthma Diabetes Pregnancy

38. Acute Mountain SicknessWhat is its normal course? Symptoms typically appear 6-12 hours after arrival at altitudes >2500 m Gradual onset Resolves over 1-3 days if further ascent does not occur

39. Lake Louise Diagnostic Criteria for Acute Mountain Sickness • Recent gain in altitude • At least several hours at the new altitude • Presence of headache plus at least one of the following symptoms: • poor appetite, nausea, vomiting • fatigue or weakness • dizziness or lightheadedness • difficulty sleeping

41. Acute Mountain SicknessWhat else could it be? • Viral illness • Carbon monoxide poisoning • Hangover • Exhaustion • Dehydration • Migraine • Brain tumour!!!

42. Principles Of Treatment Of AMS Rest • Most cases of AMS will get better in 1-2 days without specific treatment • Rest alone often relieves symptoms of AMS • Ascent in the presence of symptoms of AMS is contraindicated Descent • The only definitive treatment for altitude illness • Descent to an altitude lower than where symptoms began reliably reverses AMS Increase Oxygenation

43. Ways of improving oxygenation (1) Stop ascent (2) Descend if no improvement or condition worsens (3) Descend immediately if: - signs/symptoms of pulmonary oedema - loss of coordination - changes in level of consciousness (4) Sick persons must not be left or sent down alone

44. Acute Mountain SicknessSummary • Common at altitudes >2500 m • Descent is the only definitive treatment • Further ascent is contraindicated in the presence of symptoms of acute mountain sickness • Symptoms are shared with many other medical conditions • May progress to HACE or HAPE • Prevention includes graded ascent and drug prophylaxis • Rest, drugs and the portable hyperbaric chamber may be beneficial

45. Usually preceded by AMS Symptoms of AMS leading to confusion, hallucinations and decreased consciousness Can progress to cause death over a few hours High Altitude Cerebral Oedema

46. Occurs 2 or 3 days after arrival at altitude Dry cough Poor exercise tolerance Frothy blood stained sputum Coma Death PathophysiologyProbably related to capillary damage due to hypoxia and pulmonary hypertension High Altitude Pulmonary Oedema

47. Prevention of altitude illness • Slow ascent rate • Above 3000m - increase sleeping altitude by only 300-600m per day- take one rest day for every 1000m gained • Avoid unnecessary exertion • “Climb high sleep low”

48. How Can I Make Myself Feel Better When I’ve Got AMS? • Aspirin and Paracetamol • May relieve headache, but often ineffective • Ibuprofen • Reduces headache severity and speeds recovery time (400 mg recommended dose) • Sumatriptan – an anti-migraine drug • Anti-nausea drugs

49. Drug prophylaxis • Acetazolamide – only proven intervention • Dose – Good evidence for 500mg bd but smaller doses 125mg bd have been shown to work • Should be continued for 10-14 days at altitude • Side effects – paraesthesia, mild diuresis

50. Acetazolamide • Carbonic anhydrase inhibitor • Stimulates increased rate of breathing • Improves oxygenation • Reduces formation of fluid around brain and spinal cord Dexamethasone • Relieves symptoms of AMS • May reduce fluid leaking around brain • Exact mechanisms unknown