Thanks to Drs Rob Stephens, James Holding and Maryam Jadidi Intro Handbook has more details Anaesthesia unusual - doctors give the drugs - and see the results, instant feedback No doses - titrate to effect Dr Claire Frith Thanks to Drs Rob Stephens, James Holding and Maryam Jadidi

Contents Introduction – the classical triad General principles Hypnotic Agents Neuromuscular Paralysis Reversal of Neuromuscular Paralysis Analgesia Cardiovascular Drugs – up and down Fluids and Gasses are drugs too!

Introduction ‘Anaesthesia’ classical triad: Hypnosis Analgesia Muscle relaxation Induction, Maintenance, Emergence, Recovery

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 CVS, RS, GI, NS, Other , Side effects

2015 Anaesthesia Intravenous induction Short acting opiate - e.g. fentanyl Hypnotic ‘anaesthetic’ - e.g. propofol Set up of anaesthetic maintenance - e.g. sevoflurane vapour in oxygen and air Specific muscle paralysis may be needed Definitive analgesia Anti-emetic Others

Hypnosis: Propofol

Maintenance Sevoflurane (SEVO) – MAC = 2.2 Concepts of partial pressure and MAC Sevoflurane (SEVO) – MAC = 2.2 Used for gaseous induction. Isoflurane (ISO) – MAC = 1.1 Desflurane (DES) – MAC = 6 The most insoluble – so the fastest to equilibrate – but a respiratory irritant, so unsuitable for gaseous induction. Nitrous Oxide – a gas. MAC = 105 Oxygen /Air Propofol and Remifentanil Inhalational agents are administered by concentration rather than dose, as the concentration equilibrates between alveolus, blood and brain it must achieve a sufficient concentration within the CNS to have an effect. Minimum alveolar concentration = that concentration of anaesthetic agent that will prevent reflex response to a skin incision in 50% population. It is therefore a useful measure of depth of anaesthesia. The concentration of the anaesthetic agent in the expired gases is used to display a MAC value. Partial pressure – is the driving force behind gas transfer, In a mixture of gases, each gas has a partial pressure which is the hypothetical pressure of that gas if it alone occupied the volume of the mixture at the same temperature Anaesthetic vapours are halogenated ethers, they have a carbon skeleton and changing the halogenation e.g. fluroide/chloride alters the pharmacological and physical properties.

Muscle Paralysis Curare, compleltely and irreversibly bind nicotinic AcH receptors causing death by asphyxiation due to paralsysis of the diaphragm

Neuromuscular blockers Depolarising Suxamethonium Non-depolarising Atracurium Vecuronium Rocuronium Non-depolarising can be further divided into aminosteroids – Vec/Roc, and benzylisoquinolinium compounds – like atracurium

Nicotinic ACh Receptor

Reversal of Paralysis Neostigmine Sugammadex Blocks cholinesterase Stimulates nicotinic and muscarinic Given with an anticholinergic Sugammadex Just have to wait for sux to wear off Non-depolarisers can be ‘reversed’

Analgesia Systemic Regional – spinal / epidural / blocks Simple- paracetamol 1g NSAID – Diclofenac etc Opioids eg morphine 2mg bolus Others – Ketamine Regional – spinal / epidural / blocks Local - infiltration

Opiates Morphine Diamorphine Fentanyl Alfentanil Remifentanil Tramadol

Uppers Anticholinergics Symatheto-mimetics Atropine Glycopyrrolate 200-600μg Symatheto-mimetics
 agonists Phenylepherine Metaraminol 0.25-0.5 mg Ephedrine A mixed  and  adreno agonist 3mg The anti-cholinergics atropine and glycopyrrolate are used to reduce vagaly mediated bradycardia, and to dry secretions. Unlike atropine, glycopyrulate does not cross the blood-brain barrier, and does not cause sedation.

Downers More anaesthetic or opiate / analgesia Short acting -blockers (labetalol, esmolol) GTN Clonidine - 2 agonist clonidine

Antiemetics High rates in anaesthesia - up to 30% Avoid triggers - N2O, opiates Complex system - various brain areas - various targets - H, mACh, 5HT, DA

Antiemetics Cyclizine anti-histamine S/E – tachycardia and other anti-cholinergic effects Ondansetron 5-HT3 receptor antagonists S/E – constipation + long QT Prochlorperazine (‘Stematil’) – DA and mACh receptor antagonist S/E – extrapyramidal Dexamethasone glucocorticoid S/E – deranged glucose control

Fluids and Gases are drugs too! Oxygen is a ‘drug’ Intravenous fluids Colloids Crystalloids Blood and products

General Advice Can always give more – can’t take away Caution in Unwell Elderly Hypovolaemic Lots of ways to anaesthetise- don’t worry

Summary Classical Triad Anaesthesia Temporal sequence Usual sequence