1. Anesthesia at high altitude Dr. S. Parthasarathy MD. , DA
Anesthesia at high altitude Dr. S. Parthasarathy MD., DA., DNB, MD (Acu), Dip. Diab. Dip. Software statistics PhD ( physiology), IDRA , FICA

2. Greene was the expedition anesthetist
The first use of general anaesthesia in Tibet was during the 1904 Anglo–Tibetan War, when British military doctors administered chloroform at altitudes of > 4000 m
Greene was the expedition anesthetist

3. Lobsang Tsering, a Tibetan employed as the team’s messenger, fell from his pony and fractured his clavicle on 6th April 1933
Greene administered chloroform
Surgery was over but the recovery was very delayed
coramine

4. Emergency and accidents
So cases may be more !
Transport and conditions are better
More number of people live
More number of tourists
Acclimatized and NonAcclimatized
Emergency and accidents
Illness

5. Two schools of thought !!
1500 meters !

6. Darjeeling 2050 Ooty - 2250 Amarnath – 5100m Everest – 8850 m 6650
Golden mount kailash

7. Respiration Recall the alveolar gas equation:
PAO2=FiO2(PB-PH2O)-PaCO2/RQ
At 5000ft elevation, PB is 632 mmHg, PaO2 is 81 mmHg with SaO2 95%.
At 10,000ft elevation, PB is 522 mmHg, PAO2 is 59 mmHg, SaO2 84%.

8. Hypoxic drive
Hyperventilation
PaCO2 decrease
But kidneys preserve
acid
pH not much change
A new comer may show alkalosis !

9. That’s the safety !!

10. What happens ? Decreased demands ! 240 ml may come down to 210 ml !
at sq feet , the pp is low that he needs 48 % to achieve sea level conditions

11. What does hypoxia do ? Hyperventilation May increase by 25-30 %
2,3-DPG levels rise due to hypoxic stress, shifting O2-Hgb dissociation curve back toward the right. This facilitates O2 unloading into tissues
The normal diffusion capacity for oxygen through the pulmonary membrane is 21 ml / mmHg/ minute
May increase three times
Pulmonary blood flow increase
The drive ( pulmonary pressure} increase

12. Circulatory changes Bone marrow stimulated
15 grams Hb can become 22 gm
(Hypoxia and erythropoietin)
Muscle myoglobin appears to be increased at
altitude improving oxygen diffusion
Hypoxia of tissues induced
vasodilation can increase cardiac output !
May take three weeks

13. Hypothermia
marked irritability of AV Bundle leading to atrial and ventricular fibrillation
Can it bring down MAC of agents !

14. Circulatory system
On exposure to altitudes of 3,500 to 4,000 m, plasma volume is reduced by 3 to 5 mL/kg.
This occurs relatively rapidly after arrival at altitude, and the deficit would appear to persist for at least 3 or 4 months before starting to return toward normal

15. Miscellaneous changes !
exercise and hypoxia stimulate rennin release
but aldosterone release is decreased at high altitude
Sodium potassium – no change
Capillary density in muscle is unchanged, although the average diameter of muscle fibers appears to be reduced – oxygen to travel less

16. The normal pulmonary arterial pressure at sea level is 12mm Hg
high altitude is 28 mm Hg.
Principal etiology is hypoxia
Is it like that

17. High Altitude Illness
High Altitude Illness can take several forms that often overlap
Pathophysiology may be the same !
Acute Mountain Sickness (AMS)
High Altitude Pulmonary Oedema (HAPO)
High Altitude Cerebral Edema (HACO)

18. Acute Mountain Sickness
Anyone can be affected
Exertion,
poor hydration,
young age may contribute.
Fitness or gender ?? No use

19. Acute Mountain Sickness
Symptoms:
Early symptoms (12-24 hours):
Headache - standard analgesics may be useless
nausea, anorexia,, sleep disturbances.
Can progress to shortness of breath, g, vomiting, hallucinations, and impaired cognitive function,
Can go upto frank cyanosis

20. Acute Mountain Sickness
Rest, hydration, analgesics, oxygen can help.
Acetazolamide 250 mg q 8-12 hours may improve symptoms and SaO2 (especially during sleep)
Definitive treatment is only descent.
Come down by 500 to 1000m - we are fine !

21. Acute Mountain Sickness
Can we prevent !
Ascend slowly, but in army operations possible !
Daily altitude gain of no more than 300m above 3000m.
Rest for two nights
Hydration and less exercise !
Acetazolamide 250mg 8 hourly prophylaxis and treatment !! .CA inhibitors – unknown benefits

22. High Altitude Pulmonary Oedema (HAPO)
A Life threatening form of AMS with similar early symptoms.
May occur in any healthy individual after rapid ascent above 2500 m (8200 ft)
Dyspnea, chest pain,crepitations , tachycardia, dry cough, pink frothy sputum
Respiratory failure and death can ensue.
Protein rich exudates in hyaline membranes
Form of ARDS !

23. High Altitude Pulmonary Oedema (HAPO)
CXR - patchy infiltrates,
Bases may not be affected !
Elevated pulmonary artery pressure secondary to hypoxia.
ECG shows right heart strain
But with normal LV function

24. High Altitude Pulmonary Oedema (HAPO)
Treatment

25. High Altitude Cerebral Oedema (HACO)
One more danger !
Increased BBB permeability and increased cerebral vascular blood flow !
Hypoxia is the cause !

26. High Altitude Cerebral Oedema (HACO)
Early symptoms
Headache
Anorexia
Nausea, Emesis
Photophobia
Fatigue
Irritability
Late symptoms
Ataxia
Hallucinations
Visual disturbances
( retinal dots can also be there ! )
Focal neurological deficits
Abnormal reflexes
Cerebral edema in CT

27. HACO and HAPO may co exist !
Dexa and oxygen may help but diuretics may worsen dehydration !

28. The Gamow Bag

29. The Gamow Bag Portable, lightweight, fabric hyperbaric chamber.
Can generate 103 mm Hg of pressure above ambient pressure.
Artificial descent of 4000 to 9000 ft at moderate altitudes.

30. ANAESTHESIA AT HIGH ALTITUDE General Principles
Prone for perioperative hypoxemia
Non acclimatized person more important
Hb may not be high !
Volume Resuscitation
Bleeding : high venous pressure, increased blood volume, venous dilatation increased capillary density

31. Infection
pollution
Fire
? Kerosene lamp operations !

32. Vaporizer !! VO= (CGxSVP) / (Pb-SVP) Where VO=vapor output (ml),
CG= carrier gas flow(mL.min),
SVP=saturated vapor pressure (mm Hg) at room temp, and
Pb- barometric pressure

33. Vaporizer !
At a higher altitude where the barometric pressure is ½ that at sea level, the amount of isoflurane vapor output increases due to the lower barometric pressure.
Therefore, the settings that delivered 2% isoflurane now deliver 4% isoflurane.

34. What we need is partial pressure !!
partial pressure of isoflurane delivered would be approximately the same at both altitudes since 2% isoflurane at 760mm Hg (15.2 mm Hg) is the same as 4% isoflurane at 380mm Hg (15.2 mm Hg).

35. Shafer says ! our vaporizer, set for 1.1%, We need 1.5 %
is actually producing 1.7%,
Some overcompensation

36. But !!
Desflurane vaporizer is electrically heated to 39 degrees centigrade, which creates a vapor pressure of 2 atmospheres inside the vaporizer, regardless of ambient pressure.
The number on the dial reflects the percentage that will be delivered.
So at any altitude, when you dial 5%, it will give us 5%

38. Flow meters
At a simulated altitude of 10,000 ft (3048 m), both nitrous oxide and O2 flow meters under-read the actual flow rate.
May be upto 20 %
O2 analyser !!
Actual
Reading

39. TIVA

40. May be with less total flow
Venturi-type gas-mixing devices tend to deliver higher concentrations of O2 at altitude than they do at sea level
at an altitude of 10,000 ft (3048 m),
mask designed to deliver 35% O2 at sea level actually delivered 41% O2
41 %
May be with less total flow

41. GA - considerations Titrated premedication Good preoxygenation
Increased FiO2
Sedatives and opioids – titrated
Nitrous may dilute oxygen – may be avoided
70% may actually be 50% nitrous !
agents same percentage
Muscle relaxation OK - ? Hypothermia !
Postoperative oxygen

42. Miscellaneous Wait till acclimatization
Temperature of OT and the patient
Postoperative oxygen for atleast one hour
Pain killers – less narcotics
Watch for respiratory depression in the post op

43. Nepal in 1940s

44. Regional OK But spinal headache is more common
Bladder bowel distension is more !
Local anesthetic duration may be shortened
Cause ?

45. Summary Definition Changes AMS, HAPO , HACO Anesthesia – RA
GA – narcotics
FiO2, agents ,
Temperature ,
TIVA
Himalayan task

46. Thank you all