Anaesthetics and Analgesia Flashcards
What is anaesthesia?
- any lipid-soluble agent the causes depression of the brain in a predictable order
- Cortex
- Midbrain
- Spinal cord
- Medulla
How do anaesthetics work?
- Increase tonic inhibition
- increased action of GABA receptors
- Glycine
- Inhibit excitatory synaptic transmission
- inhibiting ligand-gated ion-channels
- NMDA receptors
- opening K+ channels
- Nicotinic
- Serotonin
How is anaesthesia administered?
- Inhale
- Oxygen
- NO
- Isoflurane
- Injected
- Propofol
- Thiopental
- Etomidate
- Ketamine
Oxygen as an anaesthetic agent
- action
- side- effects
- generally good for you
Side- effects
- O2 free radicals
- CNS convulsions
- Pulmonary oxygen toxicity
- Retrolental fibroplasia
- CO2 narcosis
Nitrous oxide as an anaesthetic agent
- action
- side-effects/ contraindications
- good analgesia but usually combined with other inhaled drugs for a good anaesthetic effect
- Fast induction/ recovery
Side-effects
- Cardio-respiratory depressant: diffusional hypoxia during recovery
- risk of bone marrow depression with prolonged use
- avoided in anaemic and 12 deficient patients
- can causes expansion in gaseous cavities
- contraindicated in pneumothorax, vascular air embolus or in an obstructed intestines
What chemical properties of inhalation need to be considered?
- Non-irritant
- Low blood-gas solubility
- High potency (Minimum alveolar conc. | MAC)
- Minimal side effects
- bio-transmission
- non-toxic
Desflurane as a general anaesthetic agent
- Fast induction/ recovery
- used for day-case surgery
- moderately expensive and environmentally damaging
- Sevoflurane is similar (expensive)
Side-effects
- respiratory tract irritation
- cough
- bronchospasm
Isoflurane as a general anaesthetic agent
- a relatively cheap stable non-flammable halogenated ether
- widely used and replaced halothane
- medium induction/recovery rate
Side-effects
- irritable to the airway
- possible risk of coronary Ischaemia in susceptible patients
Give an overview of Intravenous agents
- they are usually induction agents/ iv opiate
- rapid onset and pleasant sensations
- Lipid soluble
- short-acting, metabolised
- cause CVS/RS depression
Thiopentone as an anaesthetic agent
- Powder
- Smell of garlic
- Antiepileptic
- CVS/RS depression
- Anaphylaxis/ arterial
- Half-life 10 hours
Propofol as an anaesthetic agent
- Short-acting agent used for induction
- maintenance of GA and sedation
- onset within minutes of injection
2,6-diisopropylphenol as an anaesthetic agent
- Solvent
- Redistribution half-life - 4 minutes
- Elimination half-life - 4 hours
- Minimal accumulation - TIVA
- Antiemetic
- Antiepileptic
- Painful to inject
- Abnormal movements
- CVS/RS effects
Give an overview the use of muscle relaxants
- Dangerous drugs
- Muscle paralysis
- Facilitate intubation
- Maintain paralysis for surgery/ventilation
- Depolarising
- Non depolarising
- Anaesthetists only
Give an overview of depolarising agents
- Suxamethonium
- Post-synaptic membrane
- Mimics acetylcholine
- Rapid onset offset
- Short half life ~ 2min
- Plasma cholinesterase
- Multiple side effects
Give an overview of non-depolarising blockers
- Competitive with Ach
- Ach moiety blocks Na channel with size
- Duration is variable
- Slower onset and slower offset
- Steroid group: rocuronium
- Benzylisoquinoliniums: atracurium
Give an overview of the use of N-m blocking agents
- Intubation
- Surgery
- Ventilation
- Transfer
- Side effects
- Reversal
Gate theory - Pain
- C fibres lets pain through
- Ab fibres stimulate inhibitory neurons
- Descending pathways prevent the central passage
Give an overview of Opioids
- Act on opioid Receptor and antagonised by Naloxone
- Naturally occurring eg Morphine ,Codeine
- Semi-Synthetic eg Diamorphine
- Synthetic eg Fentanyl
- Weaker eg Codeine
What methods of administration are there for administration?
- Intravenous pca/infusion
- Intramuscualr
- Oral
- Intra nasal/aersol
- EPidural/spinal
Where are Opioid receptors found?
- POns and the Midbrain
- Periaqueductal Grey Matter
- Nucleus Raphe Magnus
- Spinal COrd Posterior Horn 1 and 2
- G.I.T
- Peripheral tissues
Subtypes
- Mu 1 and 2: OP3
- Delta: OP1
- Kappa: OP2
Give an overview of the use and effects of morphine
Effects: significantly reduces pain
Side effects
- Resp. depression/ airway loss
- N&V
- Constipation/Pruritis
- Miosis
What is Naloxone?
- drug used to treat opioid overdose
- needs to be regularly monitored and regulated
Give an overview of Ketamine and it’s effects
- acts on NMDA Receptors
- Kappa and delta receptors
- Not GABA
- Analgesic local/general
- Anaesthetic
- Sedative
- SIDE EFFECTS: emergence phenomena
Give an overview of NSAIDS and their effects
- Act by inhibiting Cyclooxygenase 1 and 2
- Analgesic, Antipyretic, Anti-inflammatory
- Side Effects
- Gastric Irritation
- Bronchospasm
- Renal Impairment
- Platelet function ASPIRIN
What is the effect of Aspirin in the body?
- Acetylsalycilic acid
- causes Oxidative phosphorylation
- causes Air Hunger
- Reyes Syndrome
Give an overview of the effect Paracetamol has on the body?
- Mechanism of Action: Central prostaglandin effect/unknown
- Side effectsOVERDOSE Hepatotoxicity/glutathione depletion
- N acetylcysteine
Give examples of other Analgesia?
- Anxiolysis
- Local anaesthetics
- Antidepressants,antiepileptics
- Guanethidine, ketamine, clonidine
- Acupuncture
- Inhalational Nitrous oxide/penthrane
- Tramadol
What are anti-emetics give examples?
- drug used to treat nausea and vomiting
- Cyclizine
- Ondansetron
- hyoscine
- Metoclopramide
- Steroids
- Prochlorperazine
- cannabinoids
The tiers of the Ramsay Sedation scale
- Patient Anxious
- Cooperative
- Responds only to commands
- Brisk response to Glabellar Tap/Shout
- Sluggish Response
- No response
Give an overview of Benzodiazepines
- Midazolam, Diazepam, Lorazepam
- Routes of administration
- suppositories, IV injection(triazolam, flunitrazepam, and diazepam emulsion)
- PHYSIOLOGY
- Gabba- aminobutyric Acid
- Inhibitory Neurotransmitter
- Receptors A and B
What are the side effects of Benzodiazepines
used for
- loss of airways
- respiratory depression
- ABC
- Flumazenil can reverse the effects of benzodiazepines
Give examples of other sedatives
- Low dose vapours
- Ketamine
- Hyoscine
- Propofol Low dose
- Major Tranquilisers
What are the classifications of local anaesthetics?
- Amides
- Lignocaine, Prilocaine, Bupivacaine
- Esters
- Cocaine, Amethocaine
Explain the mechanism of action of local anaesthetics
- Na channel blockade
- Un-ionized drug through the membrane into the axoplasm
- Protonated
- Blocks channel–> blocking the action potential
How are local anaesthetics administered?
- Anatomy Local Blocks /Ultrasound
- Spinal Epidural Caudal
- Skin
- Aerosol/Nebulised
- Combination with GA Part of Triad
How do side effects of local anaesthetics present?
- restlessness, disorientation, tremors, drowsiness
- lightheadedness circumoral numbness, dizziness visual changes
- respiratory depression
What effect does the toxicity of local anaesthetics cause in the
- cardiovascular and
- central nervous system
Cardiovascular
- dysrhythmias, Cardiac depression
CNS
- fitting/ anxiety/ loss of consciousness
- circumoral numbness
How is local anaesthetic toxicity treated?
- ABC
- Oxygen
- Lipid 20%
- Dysrhythmias/fitting
