Transcript Drugs
An Introduction to Anaesthesia 2016 ANAESTHESIA DRUGS Dr. Su Cheen Ng Consultant in Anaesthesia UCLH the centre for Anaesthesia UCL TODAYS TALK • • • • • • • • Principles to 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 Introduction - Principles Pharmacokinetics - What the body does to the drug - Absorption, distribution, metabolism, elimination Pharmacodynamics -What the drug does to the body – ie it’s effects / Side effects -CVS, RS, GI, NS, Other Objectives of Anaesthesia •Loss of awareness / Amnesia If Warranted: • Analgesia • Suppression reflex /Reduce movement in response to stimuli • Minimize autonomic responses to surgical stimuli • Skeletal Muscle relaxation TRIAD What is Balanced Anesthesia? No single drug is capable of achieving all of the desired goals of anesthesia. SIDE EFFECTS TOXICITY “Balanced Anaesthesia” - A combination of agents, to limit the dose and toxicity of each drug NOTE 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! THE GENERAL FLOW of GA Intravenous induction- e.g. propofol, thiopentone Short acting opiate - e.g. fentanyl Muscle paralysis may be needed Airway device Set up of anaesthetic maintenance – inhaled or gasses (e.g. sevoflurane vapour in oxygen and air) Others: Analgesia: IV, local anaesthesia, Antiemetic IV INDUCTION AGENT Used alone or with other drugs to: • Achieve general anesthesia • As components of balanced anesthesia • To sedate patients Examples: • Barbiturates : thiopentone • Propofol • Ketamine • Etomidate PROPOFOL - INDUCTION and MAINTENANCE of anaesthesia - Sedative, anaesthetic, amnesic, anticonvulsant, - Solvent :10% soyabean oil, 2.25% glycerol, 1.2% egg phosphatide - Rapid onset and short duration - Causes hypotension due to vasodilatation. - Pain on injection common especially small hand veins MAINTANENCE of ANAESTHESIA Most Commonly : Inhalation Agents (OR IV agents) Ie: SEVOflurane, ISOflurane, DESflurane Inhaled and Exhaled gases Alveoli Blood CNS Path of Equilibrium of inhaled agents Minimum alveolar concentration (MAC) = Measure of POTENCY 1 MAC= the concentration that results in immobility in 50% of patients when exposed to standardized skin incision In combination with: - Air - Oxygen MUSCLE RELAXANTS Indication -Tracheal intubation -Surgical relaxation -Control of ventilation Muscle Relaxants-Types Side Effects Depolarizing muscle relaxant -bradycardia -muscle ache •Suxamethonium -nausea Rapid sequence Intubation -increase K+ level -suxamethonium apnoea Does NOT provide ANALGESIA or SEDATION/UNCONSCIOUNESS Muscle Relaxants-Types Nondepolarizing muscle relaxants •Short acting: Mivacurium •Intermediate acting: Atracurium, Cisatracurium, Vecuronium, Rocuronium •Long acting: Pancuronium Does NOT provide ANALGESIA or SEDATION/UNCONSCIOUNESS Reversal of NDMB Neostigmine Increase Ach concentration SE: Slows HR, paristalsis Given with an anticholinergic Sugammadex -different doses based on indication: routine versus emergency UPPERS AND DOWNERS INCREASE BP - α adreno-receptor agonists: Metaraminol, Phenylephrine - Mixed α and β adreno agonist:Ephedrine LOWER BP - more anaesthetic agent or opiate, - short acting β-blockers- labetalol,esmolol - GTN - α2 agonist: clonidine ANALGESIC Systemic (PO/IV/ PR/ SC) Simple- Acetaminophen NSAID – Diclofenac, Ibuprofen,coxibs Opioids - Codeine, Morphine Others – Ketamine, clonidine Regional – spinal / epidural / peripheral nerve blocks Local – infiltration of local anaesthesia ANALGESIC LADDER NSAIDS= nonsteroidal anti-inflammatory drugs(ie: ibuprofen, coxibs, mefenamic acid) 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 ANTI-EMETIC cyclizine 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 Pocket references THANK YOU