Dr. Su Cheen Ng Consultant in Anaesthesia UCLH ANAESTHESIA DRUGS An Introduction to Anaesthesia 2016

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  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

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, Anti- emetic

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 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 Most Commonly : Inhalation Agents (OR IV agents) Ie: SEVOflurane, ISOflurane, DESflurane Inhaled and Exhaled gases AlveoliBlood CNS Path of Equilibrium of inhaled agents

In combination with: -Air -Oxygen

MUSCLE RELAXANTS Indication -Tracheal intubation -Surgical relaxation -Control of ventilation

Muscle Relaxants-Types Depolarizing muscle relaxant Suxamethonium Rapid sequence Intubation Side Effects -bradycardia -muscle ache -nausea -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 βadreno agonist:Ephedrine LOWER BP - more anaesthetic agent or opiate, - short acting β-blockers- labetalol,esmolol -GTN -α2agonist: 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