General Anaesthetics: Revised Flashcards
GA MOA?
- GA increase the sensitivity of GABA(A) receptors to the inhibitory neurotransmitter GABA=increases chloride ion influx hyperpolarisation of neurons
- Blockade of NMDA(Inhibt Glutamate)
- Blockade of ext post synaptic nicotinic receptors
Which GA is the execpetion when it comes to MOA?
Nitrous oxide & Ketamine
They work by inhibiting NMDA receptors. Selectively inhibit NMDA receptor to increase glutamate from increasing Calcium influx.
Inhaled volatile GA drugs?
SHINE
- Sevoflurane
- Halothane
- Isoflurane
- Nitrous Oxide
- Enflurane
- Desflurane
Halothane:
- MOA
- Admin.
3.Odour - Targert group in why?
- Hepatoxicity
- A/E
- Increases sensitivity to GABA(A) & Increases hyperpolarisation
- Inhaled or IM
- Pleasant odour therefore it does not induce respiratory reflexes
- Best in children because it is not hepatotoxic
- Not hepatotoxic
- A/E:
-Cardiotoxic: Bradycardia, Cardiac arrhythmias & concentration-dependent hypotension
-Malignant Hyperthermia
>Indiced by malignant hyperthermia or uncontrolled increased skeletal msucle oxidative metabolism
Why is halothane a drug of choice?
It has rapid induction and quick recovery
How do you avoid the toxic reaction of halothane?
Halothane is not administered at intervals of less than 2 to 3 weeks
Which property of halothane is responsible for some toxic reactions women develop post halothane anesthesia?
Halothane is metabolised in the body to tissue-toxic hydrocarbons and bromide ion and this makes it responsible for toxic reactions that some females develop after Halothane anaesthesia
What are the toxic reactions that people have post halothane?
Fever
Anorexia
Nausea
Vommiting
Hepatitis
Which patients are susceptible to Halothane-induced malignant hyperthermia?
Burn victims and individuals with muscular dystrophy, myopathy and osteogenesis imperfecta
What is the Tx Halothane-induced malignant hyperthermia?
Dantrolene (blocks release of Ca2+) from the sarcoplasmic reticulum of muscle cells,
reducing heat production and relaxing muscle tone. Monitored and supported
respiratory, circulatory, and renal systems
Stages of anaesthesia?
- Induction
- Maintenance
- Recovery
Depths of anaesthesia?
AESM
Stage I: Analgesia
Stage II: Excitement/Delirium
Stage III: Surgical Anaesthesia
Stage IV: Medullary Paralysis
Sevoflurane:
- Odour
- Target patients & their admin
- DOA & why
- Metabolised
- MOA
- Low pungency, allowing rapid induction without irritating the airways
- Suitable for inhalation induction in paediatric patients
- Has a rapid onset and recovery due to low blood solubility
- Metabolised by the liver → metabolites can be nephrotoxic
- Increases sensitivity of GABA(A) to Cl- & inhibit excitatory synaptic channel activity by binding nicotinic acetylcholine, serotonin, and glutamate receptors.
Isoflurane:
- MOA
- Odour
- Effect of kidney/liver/heart & why
- Admin
5.
- Increases sensitivity to GABA(A) & Increases hyperpolarisation
- It has a pungent odor and stimulates respiratory reflexes (irritation,
salivation, coughing, laryngospasm), therefore not used for inhalation
induction - This agent undergoes little metabolism and is, therefore, not toxic to
the liver or kidney, also, it does not induce cardiac arrhythmias - Inhalation but Not inhalation because of the pungent smell
Desflurane
- Onset of action & why?
- Frequency of use in patients?
3
- Provides very rapid onset and recovery due to low blood solubility
- A popular anesthetic for outpatient procedures
Why is desflurane administered via a special heated vaporizer?
It has a low volatility, requiring administration via a special heated
vaporizer
Desflurane relationship with vascular resistance and tissues?
It decreases vascular resistance and perfuses all major tissues very
well
Why is Desflurane not used for inhalation
It stimulates respiratory reflexes, not used for inhalation induction
Sevoflurane
- Odour
- Admin
- Use in pediatric patients
- Onset and recovery
- Metabolism
- Has low pungency, allowing rapid induction without irritating the
airways - Inhalation
- Suitable for inhalation induction in paediatric patients
- Has a rapid onset and recovery due to low blood solubility
- Metabolised by the liver → metabolites can be nephrotoxic
Nitrous oxide?
“laughing gas” is a non‐irritating potent analgesic but a weak general anaesthetic
How do we counter the effects of diffusion-hypoxia when administering nitrous oxide?
We administer with Oxygen
What allows nitrous oxide to move quickly in and out of the body?
Poorly soluble in blood and other tissues, allowing it to move very rapidly
in and out of the body
How does nitrous oxide cause pnemothroax?
Can increase the volume (pneumothorax) or pressure (sinuses), because it
replaces nitrogen in various air spaces faster than the nitrogen leaves
Nitrous oxide effects on:
- The respiratory system
- Muscle Relaxation
- CVS
- Cerebral
Does not depress respiration
Does not produce muscle relaxation.
When co‐administered with other anaesthetics, it has moderate to no effect on the CVS
Increasing cerebral blood flow, and it is the least hepatotoxic of the inhalation agents