Transcript Anaesthetic Drugs

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
Physiology and …
Dr Rob Stephens
Thanks to Drs James Holding and Maryam Jadidi
Contents
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Introduction
Physiology
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CVS, RS, NS, Other
Pharmacolgy
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Anaesthetic/ Hypnotic Agents
Neuromuscular Paralysis & Reversal
Analgesia
Others, CVS, Gasses, Fluids
Introduction
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General word:
website, documents, coming to theatre
Introduction
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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
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MAP = CO x SVR
HR x SV
Vaso-? constricted ? dilated
AT REST
5 l/min
RIGHT
HEART
L
H
100%
CVS physiology: Heart
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Heart
pumps blood (02) from lungs to tissues
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then back to heart / lungs (C013-15%
2)
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rate
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pre / afterload
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contractility
7%
4-5%
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Work =02 needs 
Heart
Brain 9%
Gastrointestinal
20-25%
Kidneys
20%
15-20%
Muscles
Anaesthesia and CVS
CVS effects..
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Anxiety, illness, walking to theatre, pain
Induction of general anaesthesia
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or onset of epidural/ spinal anaesthesia
Cardiovascular - active drugs
Intubation
Surgical stimulation / trauma
Haemorrhage
Extubation
?Recovery or complication
Cardiovascular changes
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‘artists impression’ version often filled in!
Preopera
tive
Induction of anaesthesia
Incision
Surgical stimulation
Cardiovascular Bleeding
Less 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 chronotrope
vasocontricts
Respiratory
Upper – Airway
Lower- Trachea, lungs, muscles
Respiratory- Airway
Anaesthesia ‘Obtunds’ airway
=“Airway obstruction’
= no airflow
= no 02
= Badness
Respiratory- Airway
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
Guedel / Oro-Pharyngeal
size 4
size 3
Adult male
Adult
female
Guedel
Laryngeal Mask Airway
Respiratory- Airway
Respiratory- Lower/ Lungs
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Spontaneous vs Ventilated
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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 during
awake spontaneous breathing
CT scan of Diaphragm during
anaesthesia: Atelectasis
Gastrointestinal
General Anaesthesia
relaxes gastro-oesophageal sphincter
Fluid up oesophagus
?into lungs
starvation
postoperative vomiting
Other drugs (eg analgesia)
Neurology
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Many Effects
GA
drug induced
reversable
unconsciousness
Many reflexes  (airway, gag, CN)
Awareness
+/- NMJ paralysis
Physiology
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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!
Pharmacology Introduction
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Anaesthesia ‘classical triad’
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Hypnotic agent- unconsciousness
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Gas or IV
Analgesia
Neuromuscular Paralysis
Induction, Maintenance, Emergence,
Recovery
Basics of anaesthesia: diagrams, handout &
lecture
Introduction - Principles
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Pharmacokinetics
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What the body does to the drug
Absorption, distribution, metabolism, elimination
Pharmacodynamics
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What the drug does to the body – ie it’s effects
CVS, RS, GI, NS, Other , Side effects
Typical Anaesthesia
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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)
IV
Redistributed out of CNS
metabolised
CVS - CO x SVR = MAP
RS airway and lungs
NS pain on injection
Maintenance: Volatiles
Oxygen
Air
Sevoflurane
Maintenance
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Sevoflurane (‘SEVO’)
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Used for gaseous induction.
Desflurane
Isoflurane
CO x SVR = MAP
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Gases, inhaled, little metabolised, exhaled
CVS: CO x SVR = MAP
RS- irritant, bronchodilate NS
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Given with Oxygen /Air /Nitrous Oxide
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MAC = minimum alveolar concentration
Muscle Paralysis
Neuromuscular blockers
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Depolarising
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Suxamethonium
Non-depolarising
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Atracurium
Vecuronium
Rocuronium
Neuromuscular blockers
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Depolarising
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Suxamethonium 2x Ach molecules
Activates receptor
Non-depolarising – competitive vs ACh
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Atracurium
Vecuronium
Rocuronium
Nicotinic ACh Receptor
Reversal of Paralysis
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Neostigmine
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Blocks cholinesterase
Stimulates nicotinic and
muscarinic
Given with an
anticholinergic
Sugammadex
Analgesia – Dr B
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Systemic
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Simple- paracetamol 1g
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NSAID – Diclofenac etc
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Opioids eg morphine 2mg bolus
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Others – Ketamine
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Regional – spinal / epidural / blocks
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Local - infiltration
Uppers
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Anticholinergics
 Atropine
 Glycopyrulate 200-600μg
Symatheto-mimetics
 1 agonists
 Phenylepherine
 Metaraminol 0.25-0.5 mg
 Ephedrine
 mixed  and  adreno agonist
MAP = 1
1 2
CO x SVR
Downers
More anaesthetic or opiate / analgesia
Short acting -blockers (labetalol, esmolol)
Short acting  blockers
GTN
MAP =
CO x SVR
Clonidine - 2 agonist clonidine
Antiemetics
Antiemetics
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General- Hydrate, anxiety, gastric decompress
Cyclizine
anti-histamine
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Ondansatron 5-HT3 receptor antagonists
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S/E – constipation + long QT
Prochlorperazine (‘Stematil’) –
DA and mACh receptor antagonist
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S/E – tachycardia and other anti-cholinergic effects
S/E – extrapyramidal
Dexamethasone glucocorticoid
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S/E – deranged glucose control
Fluids and Gasses are drugs too!
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Oxygen is a ‘drug’
Intravenous fluids
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Colloids
Crystalloids
Blood and products
Articles on website / youtube
General Advice
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Can always give more – can’t take away
Caution in
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Unwell
Elderly
Hypovolaemic
Lots of ways to anaesthetise- don’t worry