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An Introduction to Anaesthesia 2016
ANAESTHESIA DRUGS
Dr. Su Cheen Ng
Consultant in Anaesthesia
UCLH
the centre for
Anaesthesia
UCL
TODAYS TALK
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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
- What the body does to the drug
- Absorption, distribution, metabolism, elimination
 Pharmacodynamics
-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, Antiemetic
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
Most Commonly : Inhalation Agents (OR IV agents)
Ie: SEVOflurane, ISOflurane, DESflurane
Inhaled and
Exhaled gases
Alveoli
Blood
CNS
Path of Equilibrium of inhaled agents
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
In combination with:
- Air
- Oxygen
MUSCLE RELAXANTS
Indication
-Tracheal intubation
-Surgical relaxation
-Control of ventilation
Muscle Relaxants-Types
Side Effects
Depolarizing muscle
relaxant
-bradycardia
-muscle ache
•Suxamethonium
-nausea
Rapid sequence Intubation
-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 β adreno agonist:Ephedrine
LOWER BP
- more anaesthetic agent or opiate,
- short acting β-blockers- labetalol,esmolol
- GTN
- α2 agonist: 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