UCL Hospitals Drugs An Introduction to Anaesthesia 2019 TODAYS TALK Basic Principle s of drugs What we hope to achieve with anaesthesia Maintenance of anaesthesia Muscle relaxants Reversal agents ID: 914326
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Slide1
Dr Anita McCarron
Consultant in AnaesthesiaUCL Hospitals
Drugs
An Introduction to Anaesthesia
2019
Slide2TODAYS TALK
Basic Principles of drugs What we hope to achieve with anaesthesiaMaintenance of anaesthesiaMuscle relaxantsReversal agents for muscle relaxants
Uppers and DownersAnalgesiaAntiemetic- anti nausea/vomiting
How to look cool
Slide3Options…
General AnaesthesiaRegionalSedationLocal Anaesthesia……often a combination
Slide4Introduction - Principles
PharmacokineticsPharmacodynamics
- What
the body does to the drugAbsorption
, distribution, metabolism, elimination
-What
the drug does to the
body - ie it’s
effects / side effects
-CVS
, RS, GI, NS,
Other
Slide5Introduction – Principles AKA how to look cool
Give a little and wait- Our drugs work fast….You can always give more- but once it’s in, it’s in
Especially in elderly, septic, ICU, hypovolaemiaHave uppers ready drawn upThink about why / what you want to achieve
Slide6What do we want to Achieve with Anaesthesia ?
•BasicsHigher level
Slide7What do we want to Achieve with Anaesthesia ? Basics
• Loss of awareness / amnesia - so the patient doesn’t know what’s going on Try to make the whole horrible, horrible thing OK……Plus• Secure Airway
Analgesia • Suppression reflex /no movement in response to stimuli• Minimize autonomic responses to surgical stimuli
• Skeletal Muscle relaxation
Slide8What do we want to Achieve with Anaesthesia ? Higher
CVS: CO/ blood pressure / organ perfusion, less bleedingRS: Lung protection, etc GI: No Nausia & VomitingGU: No renal injury
NS: No postoperative confusionPain: No/little postop
pain aiming for 3/10Immune: ? Cancer recurrence / Immune supression??
Unknown: discovered by your generation, not mine!
Slide9TRIAD
Slide10What 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, tolimit the dose and toxicity of each drug
Slide11General Anaesthesia
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!
Slide12THE GENERAL FLOW …of surgery with a GA
Short acting opioid - e.g. fentanylIntravenous induction- e.g.
propofolMuscle paralysis may be needed
Airway device- secureSet up of anaesthetic maintenance
– inhaled gasses (e.g. sevoflurane vapour
in oxygen and air)
Others: Analgesia: IV, local
anaesthesia, Anti-
emetic
Slide13IV INDUCTION AGENT
Used alone or with other drugs to:• Achieve general anesthesia• As components of balanced anesthesia• To sedate patientsExamples:• Propofol
Thiopentone• Ketamine• Etomidate
Slide14PROPOFOL
INDUCTION and MAINTENANCE of anaesthesiaSedative, anaesthetic, amnesic, anticonvulsant,Solvent :10% soyabean oil, 2.25% glycerol, 1.2% egg
phosphatideRapid onset (45s) and short duration- (2-3 min)SIDE EFFECTS
Airway ObstructionApnoeaHypotension due to vasodilatation.
Pain on injection especially small hand veins
Slide15PROPOFOL
INDUCTION of AnaesthesiaAdd 2 ml 1% Lignocaine to 20ml 1% Propofol Give 3-5 ml, flush and wait 45s-60sGive more
Be ready to open airwayBe ready to ventilateBe ready with ‘Uppers’
Slide16MAINTANENCE of ANAESTHESIA
Minimum alveolar concentration (MAC) = Measure of POTENCY1 MAC= the concentration that results in immobility in 50% of patients when exposed to standardized skin incision
Most Commonly : Inhalation Agents (vs IV agents) ie: SEVOflurane DESflurane
ISOflurane,
Inhaled and Exhaled gases
Alveoli
Blood
CNS
Path of Equilibrium of inhaled agents
Slide17In combination with:
AirOxygen
Slide18MUSCLE RELAXANTS
Indication-Tracheal intubation-Surgical relaxation-Control of ventilation
Does NOT provide
ANALGESIA, SEDATION/UNCONSCIOUNESS
Slide19Muscle RelaxantsDepolarizing
•SuxamethoniumRapid sequence Intubation2x Ach molecules
Side Effects
-
bradycardia
-muscle ache
-nausea
-increase K+ level
-
suxamethonium
apnoea
-MH
• one off dose
can’t reverse
Slide20Muscle RelaxantsNon-Depolarizing
•Intermediate acting:
Rocuronium
,
Atracurium
,
Cisatracurium
,
Vecuronium
,
•Long acting:
Pancuronium
•Short acting:
Mivacurium
Slide21Reversal ofNon-Depolarizing Muscle Relaxants
Neostigmine
Increase Ach concentration
SE:
Slows HR, peristalsis
Given with an
anticholinergic
Sugammadex
-different doses based on indication: routine vs emergency
-amazing drug!
Slide22ANALGESIC
General Psychological etcSystemic
(PO/IV/ PR/ SC)Simple-
Paracetamol
NSAID – Diclofenac, IbuprofenOpioids -
Dihydrocodeine, Morphine
Others –
Ketamine, clonidine
Regional
– spinal / epidural /
peripheral nerve blocks
Local
– infiltration of local anaesthesia
Slide23ANALGESIC LADDER
NSAIDS= nonsteroidal anti-inflammatory drugs(ie: ibuprofen, coxibs, mefenamic acid)
Slide24UPPERS AND DOWNERS
Change blood pressureManipulating the CVSDirectly or indirectly
MAP = CO x SVR
DO2 = CO x
SaO2 x Hb
Slide25UPPERS
INCREASE BP Fluid ChallengeSurgery- stimulatesα
adreno-receptor agonists: Metaraminol,
PhenylephrineMixed α and β adreno
agonist: EphedrineMAP = CO
x SVR
Draw up20ml saline with 10mg
MetaraminolGive 0.5ml, flush in
Slide26DOWNERS
LOWER BP more anaesthetic agent or opioid adequate paralysis and analgesia
- short acting β-blockers-
labetalol, esmololGTN
α2 agonist: clonidine
Make sure MAC 1.1
?Paralysis warn offGive 10-25 microgrammes Fentanyl
Slide27ANTI-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
Slide28ANTI-EMETIC
cyclizine
Slide29ANTI-EMETIC
What do I do?Ondansetron 4mg (SE) IV andDexamethasone 6.6mg unless elderly/ DM / SepticAlternative Cyclizine
slowly 50mg IVWrite up postop alternative PRN
Slide30ANTIBIOTICS
Use your local policyCheck allergy30-60 minutes before surgery / tourniquetRepeat after 6 hours if still in surgery?
Slide31Problem 1: Hypertension
Slide32Problem 2: Hypotension
Slide33Problem 3: Patient moving
Slide34SUMMARY
TITRATION is key!!Can always give more – cannot take awayCaution in
Unwell/ Elderly/ HypovolaemicLots of ways to
anaesthetise- don’t worry
Ask for HELP
Slide35Pocket references
Drugs in Anaesthesia and Intensive Care Smith/ Scarth / Sasada
Slide36Slide37Pocket references
Slide38THANK YOU