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Ether to sevoflurane

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. 19 th century to 21 st century . Why this ether to sevo.

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Ether to sevoflurane

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  1. 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 flourinatedanaesthetic • 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 • 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, isoVs 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 £160-180/hr. • Rs. 15,000 / hour

  46. Anaesthetic Agent Blood:Gas coefficient at 37°C • Ether 12.1 • Methoxyflurane 15 • Halothane 2.4 • Enflurane 1.8 • Isoflurane 1.4 • Sevoflurane 0.69 • Desflurane 0.42 • Nitrous Oxide 0.47

  47. This is what the blood gas PC means

  48. Oil gas and MAC • Ether = O/G = 65 MAC = 1.92 • Halothane O/G = 220 MAC = 0.75 • Methoxy flu. O/G = 950 MAC = 0.16 • Isoflurane O/G = 91 MAC = 1.1 • Sevoflurane O/G = 55 MAC =2.6 • Desflurane O/G = 18 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 = 74 440 HALOTHANE = 197 240 NOT UNIVERSAL

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

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