11 INHALATION ANAESTHETICS/ IV ANASTHETICS Flashcards
What is one understood mechanism of action of volatile anaesthetics
Possibly due its lipophilic properties. Causing non-specific expansion of lipid bilayer and consequent disruption of receptors/ ion channels
Describe the current thinking on mechanism of action of volatile anaesthetics
Though to enhance GABA activity (inhibitory NT). Multisite vs. unifying hypothesis.
Define ‘MAC’
A means of describing potency and dose. 1 MAC = minimum alveolar concentration to produce immobility on standard surgical stimuli (forearm incision) in 50% of patients. The more potent the drug the lower the MAC. Usually described as a percentage of alveolar gas.
What are some covariates that increase MAC
Young age, hyperthermia, heavy alcohol, hyperthyroid, drugs that are stimulants (amphetamines)
What are some covariates that decrease your MAC
Old age, hypothermia, hypothyroid, drugs such as opioids/ depressants, pregnancy, Low 02
Describe the pharmacodynamics of volatile anaesthetics
Hypnosis, immobility, amnesia, decrease cerebral metabolic rate for 02, increase cerebral blood flow and intracranial pressure, lower bp, vasodilation, resp depression, bronchodilation. Also reduce portal blood flow and renal blood flow.
Describe NO
Nitrous oxide. Rapid onset, low potency, analgesic, many adverse effects.
What are the modern agents
Methyl ethyl ethers
Describe isoflurane
Pungent, potent, medium onset, cardiac stability
Describe sevoflurane
Good for induction of children, non pungent, intermediate potency.
Describe desflurane
Pungent, intermediate potency, ideal for long surgeries.
Name three methyl ethyl ethers
Isoflurane, sevoflurane, desflurane.
Describe the concept of balanced anaesthesia and the components/ drugs that encompass it
Hypnosis/ amnesia (iv/ inhalation anaesthetics)
Autonomic areflexia (opioids)
Immobility (NMB)
Name five types of IV anaesthetics
Barbituates, phenols, imidazoles, phenycyclidine derivatives, benzodiazepines
Describe the mechanism of action of IV anaesthetics
Like inhalation anaesthetics mechanism not well understood. Thought to a) enhance GABA–> prolong Cl- current, hyper polarisation.
b) bind to PCP receptor and antagonise glutamate/ suppress excitation.