General anesthesia Flashcards
Role of GA
to produce unconsciousness and lack of responsiveness to noxious stimuli
What are the stages of GA
Pre-assessment Induction of anesthesia Airway management Maintenance of anesthesia Reversal Post operative care
Properties of ideal anaesthetic drug?
MUDBAMMA Unconsciousness Analgesia Muscle relaxation Amnesia Brief and pleasant Depth of anesthesia can be raised/lowered with ease Minimal adverse effects Margin of safety is large
What is balanced anesthesia?
Must have unconsciousness, pain relief, inhibition of reflexes
What are the types of GA?
Inhalation and IV anesthetics
Types of inhalation anesthetics
Volatile liquids (halogenated hydrocarbons) and gases (NO)
What level of solubility would give a faster onset
Low solubility will lead to faster onset
High solubility → will stay in blood and doesn’t get to the brain
What are the proposed mechanisms of inhalant GA?
Enhance neurotransmission at inhibitory synapses via allosterically increasing GABA receptor sensitivity to GABA
Depressing neurotransmission at excitatory synapses via blocking glutamate neurotransmitter acting on NMDA receptor
What is MAC an index of?
Index of inhalation anesthetic potency
The lower the MAC, the more potent it is
It is defined as the minimum concentration of drug in alveolar air that will produce immobility in 50% of patients
How can MAC values be altered?
Age, condition, concomitant administration of other drugs
What are the factors affecting absorption of inhalant anesthetic?
Concentration of anesthetic in inspired air
Solubility of GA
Blood flow through lungs
How are inhalant anesthetics eliminated?
Almost entirely via the lungs
Which metabolites are nephrotoxic?
Isoflurane, enflurane, sevoflurane
Which metabolites are hepatotoxic?
Halothane
Which GA leads to bradycardia and arrythmia leading to hypotension?
Halothane (due to depression of CO)
Which GA leads to hypotension due to decrease in systemic vascular resistance?
Isoflurane
Which GA have medium onset and recovery?
Isoflurane and halothane
Which GA cannot be used with carbon dioxide absorbents in vaporiser machines?
Sevoflurane
What is nitrous oxide used for?
Analgesia when don’t need unconsciousness
Adjunct for patient before going unconscious to reduce pain
Side effects of nitrous oxide?
Post operative NV
What is an induction agent?
A substance that induces unconsciousness, does not necessarily keep you unconscious for a long time
Types of IV GA
Thiopentone, midazolam, propofol, ketamine
What are the advantages of using inhaled + IV anesthetics
Permit dosage of inhalation agent to be reduced (high dose needed to induce anesthesia)
Produce effects that cannot be achieved with inhalation alone (such as analgesia, anxiolytic, fast)
What type of IV GA is thiopental? Is tolerance and dependency a concern?
Short acting barbiturate
No, because it is used once only
MOA of thiopental
Causes CNS depression by potentiating the action of GABA on GABA a receptors, leading to hyperpolarisation
Which IV GA is used for day surgery?
Propofol - continuous low dose infusion
Which IV GA has similar side effects as halothane?
Propofol (hypotension and bradycardia)
What is the MOA of ketamine?
glutamate NMDA receptor antagonist
Does ketamine produce full unconsciousness?
No, produces dissociative anesthesia
Which IV GA has psychologic adverse reactions?
Ketamine - hallucination, delirium, distrubing dreams
Can be minimised using diazepam or midazolam premedication
Which IV anesthetic has analgesic property?
Ketamine
What do anesthetic adjuncts do?
Provide sedation, amnesia, analgesia
Types of anesthetic adjuncts
Midazolam (anxiolysis, amnesia, sedation)
Dexmedetomidine (sedation and analgesic)
NSAIDs (analgesics)
Succinylcholine (relax muscles)
What is succinycholine used for?
Administered during induction of anesthesia to relax muscles of jaw, neck and airway → facilitate laryngoscopy and endotracheal intubation
