1. MD. DA. DNB., Dip.diab. MD(acu) , DCA, Dip. Software-statistics.
Ether to sevoflurane
Dr . S. Parthasarathy
MD. DA. DNB., Dip.diab. MD(acu) , DCA, Dip. Software-statistics.
Ph D ( physiology)
Mahatma Gandhi medical college and research institute , puducherry – India

2. 19th century to 21st century

3. Why this ether to sevo In search of the almighty
Or the ideal anaesthetic

4. The topic in one slide

5. What is ideal anaesthetic ?
Physical
Boiling point above ambient temperature
Simple apparatus
Chemically stable
Long shelf-life, compatible with soda-lime, metals and plastics
Not inflammable
Cheap

6. What is ideal anaesthetic ?
Pharmacodynamic
High potency
Allows high FiO2
High therapeutic index
Analgesic

7. What is ideal anaesthetic ?
Pharmacokinetic
Low solubility
Rapid onset, rapid offset, adjustable depth
Minimal metabolism
Predictable in all age groups

8. What is ideal anaesthetic ?
Adverse actions
Minimal toxicity
Minimal unwanted effects
Nausea, vomiting, cardiac arrhythmogenicity
No toxicity with chronic low-level exposure of staff

9. We – rare doctors to use drugs through lungs
completely painless induction
No IV (intravenous) access needed.
Most rapid entry and exit
Most efficient choice in patient with difficult IV access.
So easily and safely
administered by modern
anesthesia machines

10. Ether
CH3– O – CH3
Dimethyl ether
C2H5 – O -- C2H5
Diethyl ether

11. WTG morton and his demo

12. ETHER Blood gas PC – 12 MW = 74.1 Boiling point = 34.6 SVP = 440
MAC = 1.92
Simple safe - used for centuries

13. Problems with ether It attacks plastic and rubber
Vomiting is quite common
Inflammable
Dense than air
Flames along the floor
B/G = 12 ??

14. Simpson and snow Chloroform
Snow gave analgesic doses of chloroform on a folded handkerchief. This technique was soon termed chloroform à la reine. Victoria enjoyed the relief from labour pain
She wrote in her journal,
“Dr. Snow gave that blessed chloroform and the effect was soothing, quieting, and delightful beyond measure.”

15. Chloroform was OK but
Liver and
Cardiac toxicity

16. Ethyl chloride and ethylene
Spray
Freeze and painless
Ethylene – high doses needed – explosive
Propylene in steel cylinder produced toxic substances – one was cyclopropane
It anaesthetized WHOM ??

17. Explosion

18. TRILENE Oh This does not explode But phosgene was produced in sodalime
Cannot use

19. Halogens and alkanes convulsant properties
complete halogenation, or complete end-methyl halogenation on alkanes & ethers results in decreased anaesthetic potency and the appearance of convulsant activity
the "cutoff effect"
increasing homologues of alkane series display cutoff point, beyond which anaesthetic potency sharply decreases

20. Fluorine No explosion No flammability
Resist separation by thermal and chemical means
Less toxic
The answer was

21. Fluroxene First flourinated anaesthetic
But a metabolite is toxic to animals
Suckling created halothane in 1953
Halogenated ethane

22. Halothane

23. Advantages least expensive volatile anesthetic agent SVP - 240
B/G = 2.1
O/G = 224
MAC = 0.75

24. Halothane No flammability Fast induction Sweet smell Thymol needed
BUT
Thymol needed
Uv rays instability
Arrhythmia
Hepatotoxic
Metabolism 20 %

25. So the search was on and on
Methoxyflurane
BP = 104 and SVP of 22
B/G = 11
O/G = 950 and hence MAC = 0.16
But metabolism and flouride induced nephro toxicity - dangerous

26. So came enflurane and isoflurane

27. Enflurane a nonflammable fluorinated ethyl methyl ether BP = 56
B/G = 1.9
O/G = 97
MAC = 1.6
Scientists came back to ethers to avoid arrythmogenicity

28. Enflurane
Negative inotropy
seizures

29. Isoflurane vapor pressure = 240 mmHg at 20 deg C pungent ethereal odor
chemical isomer of enflurane
minimal cardiac depression
carotid baroreflexes relatively intact
heart rate increases 10-20%
mild beta-adrenergic stimulation

30. Isoflurane BP = 48.5 SVP = 240 B/G = 1.4 O/G = 91 MAC = 1.1
Metabolism – 2% , no hepatotoxic, no nephrotoxic fears

31. Then came sevo and des

32. En, iso Vs sevo, des - only fluorine

33. Sevoflurane Seven fluorine atoms and hence the name
Sweet smell to allow smooth induction
Fast induction and recovery
Green house effect
global warming potential of 345.

34. Sevoflurane BP= 58.5 B/G = 0.6 O/G = 55 MAC = 2
Degradation with soda lime – compound A and compound B
Numerous evidence showed its safety of prolong ed use in hypothermic patients with low flows

35. DESFLURANE
BP = 22
SVP = 660
B/G = 0.42
O/G = 18.7
MAC = 6

36. DESFLURANE Irritant to airways No to inh. Induction
Paediatric emergence delirium
Cost excessive
Carbonmonoxide formation risk -as with all present- but insignificant

37. Des Vs Sevo
switching from isoflurane to desflurane toward the end of anesthesia does not significantly accelerate recovery nor does faster emergence
Desflurane emergence has been associated with delirium in some pediatric patients.
Rapid increases in desflurane concentration lead to transient but sometimes worrisome elevations in heart rate, blood pressure, and catecholamine levels

38. Sevo and des- cardiac output – ok even in 2 MAC

39. UV light stability
Enf
Iso
Sevo
Des OK

40. Actions of all anaesthetics
general anesthesia,
slightly increases CBF and ICP
decreases CMRO2
Increases nondepolarizers
depresses respiration
bronchodilator
Hypoxic response, ventilatory response to CO2
Negative inotropy and vasodilation
Uterine relaxant

41. Relative Contraindications of all inhaled anaesthetics
Malignant hyperthermia
Increased ICT
Severe hypovolumia

42. We don’t know when he will come
XENON

43. Xenon Greek for stranger
First used in 1951 by Cullen on an 81yr old man having an orchidectomy
B/G = 0.115
O/G = 20
MAC = 60 – 70 %

44. XENON Fast in and fast out No metabolism
inert gas that is nonexplosive, nonpungent odorless, chemically inert, some analgesia
Cardiac safety
No fink hypoxia
not to trigger malignant hyperthermia
Stability – good
But

45. The cost Use of semiclosed systems cost £1200/hr. Rs. 90,000/ hour
Very low flow e.g. 0,3 l/min will cost £ /hr.
Rs. 15,000 / hour

46. Anaesthetic Agent Blood:Gas coefficient at 37°C
Ether
Methoxyflurane
Halothane
Enflurane
Isoflurane
Sevoflurane
Desflurane
Nitrous Oxide

47. This is what the blood gas PC means

48. Oil gas and MAC Ether = O/G = 65 MAC = 1.92
Halothane O/G = MAC = 0.75
Methoxy flu. O/G = MAC = 0.16
Isoflurane O/G = MAC = 1.1
Sevoflurane O/G = MAC =2.6
Desflurane O/G = MAC = 6

49. Molecular weight
Non ionized and low molecular weight enables inhalational agents to go to tissues without
Processes like
Active transport
Facilitated diffusion
MW = VAPOUR PRESSURE
ETHER =
HALOTHANE =
NOT UNIVERSAL

50. BRAIN BLOOD COEFFICIENT
Halo = 1.9
Iso = 1.6
Sevo = 1.7
Des = 1.3

51. METABOLISM Halothane: 20% Enflurane: 2.5% Isoflurane: 0.2%
Desflurane: %
Sevoflurane:5%

52. SUMMARY Ether , fire Halo – rhythm disturbance Go back to ethers
Flourine – stability
Metabolism
Safety

53. CARRY HOME MESSAGE

54. Letter from my 5 year old daughter on my birthday

55. Enjoy life’s precious moments thank you all