The principles of anaesthesia - ExeSS

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The principles of anaesthesia - ExeSS

  1. 1. The Principles of Anaesthesia(…..and some other bits too) Dr David Hutchins CT2 ACCS Anaesthetics RD&E d.hutchins@nhs.net 19/10/2012
  2. 2. What we will cover• Definition of Anaesthesia• Why is it important?• Mechanism & stages• Planning & pre-op• Fasting• Airway assessment quiz• Equipment used quiz• Analgaesia• Blood pressure physiology
  3. 3. What is anaesthetics?
  4. 4. What is Anaesthesia?“Without sensation”1846 by Wendell Holmes to describe ‘state of sleep from ether’.Early drugs: opium, alcohol, cocaineN2O (1844) & CO2Ether (1846, Morton in Boston)Chloroform (1847, Simpson)NMBDs (1942)Halothane (1956)ThiopentalPropofolIso/Sevo/Des-flurane
  5. 5. Early demonstration of surgical anaesthesia, Boston 1846
  6. 6. Re-enactment of first ether use in London, Dec 1846
  7. 7. Morton using Ether for dental surgery 1846
  8. 8. Mechanism of AnaesthesiaNo one really knowsAnatomical:• BRAIN: Ascending reticular activating system +/- cerebral & olfactory cortex, hippocampus, & limbic system• SPINAL CORD• SYNAPSES – pre & post• CELL MEMBRANES & apparatus – lipid soluble
  9. 9. Stages of anaesthesia• STAGE 1 – analgaesia. Normal reflexes. End is loss of eyelash reflex.• STAGE 2 – excitement. Irreg breathing/struggling. Pupil dilation. Vomit/cough/laryngospasm. Ends with return of spontaneous breathing & loss eyelid reflex.• STAGE 3 – various depth planes. Central fixed pupils, intercoastal paralysis, light reflex depressed, diaphragmatic paralysis.• STAGE 4 – overdose. Apnoea, dilated pupils.
  10. 10. Proper planning prevents p***poor performancePre-op:• Assessment• Optimisation• Induction of anaesthesiaIntra-op:• Maintenance of anaesthesia• Patient positioning• Maintenance of physiologyPost op:Care (day case/in Pt on ward or ICU)Medications – analgaesia, Abx, reg meds
  11. 11. Airway assessment quiz
  12. 12. Airway assessment quiz
  13. 13. Airway assessment quiz
  14. 14. General considerations – pre op testsOnly if they improve patient outcomes• CXR• ECG• Bloods• Random glucose• Urine• ABG
  15. 15. FastingPulmonary aspirationSignificant morbidity & mortality with 30mls gastric contents• Clear liquids – 2 hrs• Breast milk - 4 hrs• Light meal/formula – 6 hrs• Heavy meal (high fat/meatcontent) – 8 hrs
  16. 16. Mendelson syndrome
  17. 17. Causes of delayed gastric emptying• Medical: DM (poorly controlled), renal failure, sepsis, anxiety• Traumatic: Head injury, pain• Congenital: pyloric stenosis• Physiological: pregnancy, obesity• Pharmacological: Opioids
  18. 18. How can you give an anaesthetic?General Regional• Inhalational • Spinal• Intravenous • Epidural • CSE • Peripheral nerve blocksLocal• Wound
  19. 19. Quiz?
  20. 20. Doing well! Take a break
  21. 21. What we have covered so far• Definition of Anaesthesia• Why is it important?• Mechanism & stages• Planning & pre-op• Fasting• Airway assessment• Equipment used
  22. 22. What we will now go over• Anaesthetic induction• Analgaesia• Cardiovascular physiology• Beer o’clock
  23. 23. Anaesthetic induction• Hypnosis = unconsciousness, with Propofol / Thiopentone / Ketamine / Etomodate / or vapours• Analgaesia = WHO analgaesic ladder• Muscle relaxation = paralysis, block NMJ with NMBDs (Sux) or (Atracurium/Rocuronium/Mivacurium etc)
  24. 24. WHOanalgaesic ladder
  25. 25. Cardiovascular physiologyBP = CO x SVRCO = HR x SVSV depends on• Preload (volume status)• Contractility (Frank Starling curve)• Afterload (SVR)
  26. 26. Frank Starling Curve Ability of heart to vary SV according to filling volume
  27. 27. Blood pressure control – 2 waysBaroreceptors: carotid sinus, aortic archCN IX & X, medullaHormonal control: circulating adrenaline/noradrenaline/Vasopressin & Renin/Angiotensin II.
  28. 28. Its all over!!!Well done …….. or wakey wakey.
  29. 29. Summary• Definition of Anaesthesia• Why is it important?• Mechanism & stages• Planning & pre-op• Fasting• Airway assessment quiz• Equipment used quiz• Analgaesia• Blood pressure physiology
  30. 30. Any questions?Please complete my feedback form. Thank you!

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