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Drugs

An Introduction to Anaesthesia 2019. Drugs. Dr Anita McCarron Consultant in Anaesthesia UCL Hospitals. TODAYS TALK. Basic Principle s of drugs What we hope to achieve with anaesthesia Maintenance of anaesthesia Muscle relaxants Reversal agents for muscle relaxants

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Drugs

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  1. An Introduction to Anaesthesia 2019 Drugs Dr Anita McCarron Consultant in Anaesthesia UCL Hospitals

  2. TODAYS TALK • Basic Principles of drugs • What we hope to achieve with anaesthesia • Maintenance of anaesthesia • Muscle relaxants • Reversal agents for muscle relaxants • Uppers and Downers • Analgesia • Antiemetic- anti nausea/vomiting • How to look cool

  3. Options… • General Anaesthesia • Regional • Sedation • Local Anaesthesia • ……often a combination

  4. Introduction - Principles • Pharmacokinetics • Pharmacodynamics • - What the body does to the drug • Absorption, distribution, metabolism, elimination • -What the drug does to the body • - ie it’s effects / side effects • -CVS, RS, GI, NS, Other

  5. Introduction – Principles AKA how to look cool • Give a little and wait- • Our drugs work fast…. • You can always give more- but once it’s in, it’s in • Especially in elderly, septic, ICU, hypovolaemia • Have uppers ready drawn up • Think about why / what you want to achieve

  6. What do we want to Achieve with Anaesthesia ? • •Basics • Higher level

  7. What do we want to Achieve with Anaesthesia ? Basics • • Loss of awareness / amnesia - so the patient doesn’t know what’s going on • Try to make the whole horrible, horrible thing OK…… • Plus • • Secure Airway • Analgesia • • Suppression reflex /no movement in response to stimuli • • Minimize autonomic responses to surgical stimuli • • Skeletal Muscle relaxation

  8. What do we want to Achieve with Anaesthesia ? Higher CVS: CO/ blood pressure / organ perfusion, less bleeding RS: Lung protection, etc GI: No Nausia & Vomiting GU: No renal injury NS: No postoperative confusion Pain: No/little postop pain aiming for 3/10 Immune: ? Cancer recurrence / Immune supression?? Unknown: discovered by your generation, not mine!

  9. TRIAD

  10. What is Balanced Anesthesia? “Balanced Anaesthesia” - A combination of agents, to limit the dose and toxicity of each drug No single drug is capable of achieving all of the desired goals of anesthesia. SIDE EFFECTS TOXICITY

  11. General Anaesthesia General anesthesia (GA) -uses intravenous and inhaled agents to allow adequate surgical access to the operative site. GA may not always be the best choice; depending on a patient’s clinical presentation!

  12. THE GENERAL FLOW …of surgery with a GA • Short acting opioid - e.g. fentanyl • Intravenous induction- e.g. propofol • Muscle paralysis may be needed • Airway device- secure • Set up of anaesthetic maintenance – inhaled gasses (e.g. sevofluranevapour in oxygen and air) • Others: Analgesia: IV, local anaesthesia, Anti-emetic

  13. IV INDUCTION AGENT • Used alone or with other drugs to: • • Achieve general anesthesia • • As components of balanced anesthesia • • To sedate patients • Examples: • •Propofol • Thiopentone • • Ketamine • • Etomidate

  14. PROPOFOL • INDUCTION and MAINTENANCE of anaesthesia • Sedative, anaesthetic, amnesic, anticonvulsant, • Solvent :10% soyabean oil, 2.25%glycerol, 1.2% egg phosphatide • Rapid onset (45s) and short duration- (2-3 min) • SIDE EFFECTS • Airway Obstruction • Apnoea • Hypotension due to vasodilatation. • Pain on injection especially small hand veins

  15. PROPOFOL • INDUCTION of Anaesthesia • Add 2 ml 1% Lignocaine to 20ml 1% Propofol • Give 3-5 ml, flush and wait 45s-60s • Give more • Be ready to open airway • Be ready to ventilate • Be ready with ‘Uppers’

  16. MAINTANENCE of ANAESTHESIA Most Commonly : Inhalation Agents (vs IV agents) ie: SEVOfluraneDESfluraneISOflurane, Minimum alveolar concentration (MAC) = Measure of POTENCY 1 MAC= theconcentrationthat results in immobility in 50% of patients when exposed to standardized skin incision Inhaled and Exhaled gases Alveoli Blood CNS Path of Equilibrium of inhaled agents

  17. In combination with: • Air • Oxygen

  18. MUSCLE RELAXANTS Indication -Tracheal intubation -Surgical relaxation -Control of ventilation Does NOT provide ANALGESIA, SEDATION/UNCONSCIOUNESS

  19. Muscle RelaxantsDepolarizing Side Effects -bradycardia -muscle ache -nausea -increase K+ level -suxamethoniumapnoea -MH • one off dose • can’t reverse •Suxamethonium Rapid sequence Intubation 2x Ach molecules

  20. Muscle RelaxantsNon-Depolarizing •Intermediate acting: Rocuronium, Atracurium, Cisatracurium, Vecuronium, •Long acting: Pancuronium •Short acting: Mivacurium

  21. Reversal ofNon-Depolarizing Muscle Relaxants • Neostigmine • Increase Ach concentration • SE: Slows HR, peristalsis • Given with an anticholinergic • Sugammadex -different doses based on indication: routine vs emergency -amazing drug!

  22. ANALGESIC General Psychological etcSystemic (PO/IV/ PR/ SC) • Simple-Paracetamol • NSAID – Diclofenac, Ibuprofen • Opioids - Dihydrocodeine, Morphine • Others – Ketamine, clonidine Regional– spinal / epidural / peripheral nerve blocksLocal – infiltration of local anaesthesia

  23. ANALGESIC LADDER NSAIDS= nonsteroidal anti-inflammatory drugs(ie: ibuprofen, coxibs, mefenamic acid)

  24. UPPERS AND DOWNERS • Change blood pressure • Manipulating the CVS • Directly or indirectly • MAP = CO x SVR • DO2 = CO x SaO2xHb

  25. UPPERS • INCREASE BP • Fluid Challenge • Surgery- stimulates • α adreno-receptor agonists: Metaraminol, Phenylephrine • Mixed α and βadreno agonist: Ephedrine MAP = CO x SVR Draw up 20ml saline with 10mg Metaraminol Give 0.5ml, flush in

  26. DOWNERS • LOWER BP • more anaesthetic agent or opioid • adequate paralysis and analgesia • - short acting β-blockers- labetalol, esmolol • GTN • α2agonist: clonidine Make sure MAC 1.1 ?Paralysis warn off Give 10-25 microgrammes Fentanyl

  27. ANTI-EMETIC • Postoperative nausea and vomiting (PONV- any nausea, retching, or vomiting occurring during the first 24–48 h after surgery • INCIDENCE: 30% in all post-surgical patients, up to 80% in high-risk patients

  28. ANTI-EMETIC cyclizine

  29. ANTI-EMETIC What do I do? • Ondansetron 4mg (SE) IV and • Dexamethasone 6.6mg unless elderly/ DM / Septic • Alternative Cyclizine slowly 50mg IV • Write up postop alternative PRN

  30. ANTIBIOTICS • Use your local policy • Check allergy • 30-60 minutes before surgery / tourniquet • Repeat after 6 hours if still in surgery?

  31. Problem 1: Hypertension

  32. Problem 2: Hypotension

  33. Problem 3: Patient moving

  34. SUMMARY • TITRATION is key!! Can always give more – cannot take away • Caution in • Unwell/ Elderly/ Hypovolaemic • Lots of ways to anaesthetise- don’t worry • Ask for HELP

  35. Pocket references Drugs in Anaesthesia and Intensive Care Smith/ Scarth / Sasada

  36. Pocket references

  37. THANK YOU

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