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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 BREAK
15.45 - 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 anaesthesiaP
reo
per
ati
ve
Surgical stimulation
Inci
sio
n
Cardiovascular BleedingLess oxygen in blood
Less pressure at Atrial and Aortic stretch
Sympathetic ++ response (+renal, adrenal)
Blood pressure maintained …
CO x SVR
↑HR x ↑SV
vasocontricts
↑ ↑
+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
Gastrointestinal
General Anaesthesia
relaxes gastro-oesophageal sphincter
Fluid up oesophagus?into lungs
starvation
postoperative 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 SVR1 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