Anaesthesia

Anaesthesia

13.30 - 14.30 Dr Rob Stephens Physiological and Pharmacological principles

14.30 - 15.30 Dr Andy Badacsonyi Anaesthesia in the 21st century

15.30 - 15.45 BREAK15.45 - 16.45 Dr Brigitta Brandner

Acute Pain Management

Dr Rob StephensThanks to Drs James Holding and Maryam Jadidi

Physiology and …

Contents Introduction Physiology

CVS, RS, NS, Other Pharmacolgy

Anaesthetic/ Hypnotic Agents Neuromuscular Paralysis & Reversal Analgesia Others, CVS, Gasses, Fluids

Introduction

General word: website, documents, coming to theatre

Introduction

Anaesthesia is more than Physiology and Pharmacology!

Surgery vs Anaesthesia Outside theatre

CVS physiology

O2 + C6H12O6 CO2 + H2O

ATP

O2 delivery =Amount of O2 to tissues per minute=Cardiac Output x O2 content of blood x

HR x SV Hb x Sa02 x constant

CVS physiology

MAP = CO x SVRHR x SV Vaso-? constricted ? dilated

CVS physiology: Heart Heart

pumps blood (02) from lungs to tissues then back to heart / lungs (C02)

Work =02 needs rate pre / afterload contractility

Lungs

Brain

Heart

Gastrointestinal

Muscles

Skin

Bones fat

Kidneys

100%

4-5%

13-15%

20-25%

20%

15-20%

3-6%

10-15%

100%

3-4%

4-5%

3-5%

2-4%

1-2%

80-85%

COAT REST5 l/min

RIGHTHEART

LEFTHEART

9%

7%

CO DURINGHARD WORK25 l/MIN

CO INSEPSIS10-15 l/min

Anaesthesia and CVS

CVS effects.. Anxiety, illness, walking to theatre, pain Induction of general anaesthesia

or onset of epidural/ spinal anaesthesia Cardiovascular - active drugs Intubation Surgical stimulation / trauma Haemorrhage Extubation ?Recovery or complication

Cardiovascular changes ‘artists impression’ version often filled in!

Induction of anaesthesiaPr

eope

rativ

e

Surgical stimulation

Inci

sion

Cardiovascular BleedingLess oxygen in bloodLess pressure at Atrial and Aortic stretch

Sympathetic ++ response (+renal, adrenal) Blood pressure maintained …

CO x SVR

↑HR x ↑SVvasocontricts

↑ ↑

+ve inotrope +ve chronotropevasocontricts

Respiratory

Upper – Airway

Lower- Trachea, lungs, muscles

Respiratory- Airway

Anaesthesia ‘Obtunds’ airway=“Airway obstruction’ = no airflow= no 02 = Badness

Keep Airway open: Airway manoeuvres (chin lift etc) Airway devices- above vs blow cords

Above Vocal Cords eg , gudel, LMA

Below Vocal Cords - Into trachea = intubation, paralysis

Respiratory- Airway

Guedel / Oro-Pharyngeal

Adult male

Adult female

Guedel

size 4

size 3

Laryngeal Mask Airway

Respiratory- Airway

Respiratory- Lower/ Lungs

Spontaneous vs Ventilated Lungs smaller depth Drugs respiratory rate Small airways / Alveolar collapse Can’t cough – secretions

= ‘pulmonary shunt (vs deadspace) Hypoxaemia, persists postoperatively

CT scan of Diaphragm duringawake spontaneous breathing

CT scan of Diaphragm duringanaesthesia: Atelectasis

GastrointestinalGeneral Anaesthesia

relaxes gastro-oesophageal sphincterFluid up oesophagus?into lungs

starvationpostoperative vomiting

Other drugs (eg analgesia)

Neurology

Many Effects GA drug induced

reversable unconsciousness

Many reflexes (airway, gag, CN) Awareness +/- NMJ paralysis

Physiology

2(3) factors determining blood pressure How does GA affect these? 3 words about GA on resp system

Contents

Introduction – the classical triad

Introduction – general principles

Hypnotic Agents

Neuromuscular Paralysis + Reversal

Analgesia

Cardiovascular Drugs – up and down

Fluids and Gasses are drugs too!

the centre forAnaesthesia UCL

Pharmacology Introduction Anaesthesia ‘classical triad’

Hypnotic agent- unconsciousness Gas or IV

Analgesia Neuromuscular Paralysis

Induction, Maintenance, Emergence, Recovery

Basics of anaesthesia: diagrams, handout & lecture

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

Typical Anaesthesia Intravenous induction Propofol 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

Hypnosis: Propofol (and others)

IVRedistributed out of CNSmetabolised

CVS - CO x SVR = MAP RS airway and lungsNS pain on injection

Maintenance: Volatiles

AirOxygen

Sevoflurane

Maintenance

Sevoflurane (‘SEVO’) Used for gaseous induction.

Desflurane Isoflurane

Gases, inhaled, little metabolised, exhaled CVS: CO x SVR = MAP RS- irritant, bronchodilate NS

Given with Oxygen /Air /Nitrous Oxide

CO x SVR = MAP

MAC = minimum alveolar concentration

Muscle Paralysis

Neuromuscular blockers

Depolarising Suxamethonium

Non-depolarising Atracurium Vecuronium Rocuronium

Neuromuscular blockers

Depolarising Suxamethonium 2x Ach molecules Activates receptor

Non-depolarising – competitive vs ACh Atracurium Vecuronium Rocuronium

Nicotinic ACh Receptor

Reversal of Paralysis

Neostigmine Blocks cholinesterase Stimulates nicotinic and

muscarinic Given with an

anticholinergic

Sugammadex

Analgesia – Dr B Systemic

Simple- paracetamol 1g NSAID – Diclofenac etc Opioids eg morphine 2mg bolus Others – Ketamine

Regional – spinal / epidural / blocks Local - infiltration

Opiates

MorphineDiamorphineFentanylAlfentanilRemifentanilTramadol

Uppers Anticholinergics

Atropine Glycopyrulate 200-600μg

Symatheto-mimetics 1 agonists

Phenylepherine Metaraminol 0.25-0.5 mg

Ephedrine mixed and adreno agonist

MAP = CO x SVR

1 21

Downers

More anaesthetic or opiate / analgesia

Short acting -blockers (labetalol, esmolol)

Short acting blockers

GTN

Clonidine - 2 agonist clonidine

MAP = CO x SVR

Antiemetics

Antiemetics General- Hydrate, anxiety, gastric decompress Cyclizine anti-histamine

S/E – tachycardia and other anti-cholinergic effects Ondansatron 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 Gasses are drugs too!

Oxygen is a ‘drug’ Intravenous fluids

Colloids Crystalloids Blood and products

Articles on website / youtube

General Advice

Can always give more – can’t take away Caution in

Unwell Elderly Hypovolaemic

Lots of ways to anaesthetise- don’t worry