11 INHALATION ANAESTHETICS/ IV ANASTHETICS Flashcards

1
Q

What is one understood mechanism of action of volatile anaesthetics

A

Possibly due its lipophilic properties. Causing non-specific expansion of lipid bilayer and consequent disruption of receptors/ ion channels

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2
Q

Describe the current thinking on mechanism of action of volatile anaesthetics

A

Though to enhance GABA activity (inhibitory NT). Multisite vs. unifying hypothesis.

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3
Q

Define ‘MAC’

A

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.

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4
Q

What are some covariates that increase MAC

A

Young age, hyperthermia, heavy alcohol, hyperthyroid, drugs that are stimulants (amphetamines)

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5
Q

What are some covariates that decrease your MAC

A

Old age, hypothermia, hypothyroid, drugs such as opioids/ depressants, pregnancy, Low 02

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6
Q

Describe the pharmacodynamics of volatile anaesthetics

A

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.

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7
Q

Describe NO

A

Nitrous oxide. Rapid onset, low potency, analgesic, many adverse effects.

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8
Q

What are the modern agents

A

Methyl ethyl ethers

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9
Q

Describe isoflurane

A

Pungent, potent, medium onset, cardiac stability

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10
Q

Describe sevoflurane

A

Good for induction of children, non pungent, intermediate potency.

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11
Q

Describe desflurane

A

Pungent, intermediate potency, ideal for long surgeries.

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12
Q

Name three methyl ethyl ethers

A

Isoflurane, sevoflurane, desflurane.

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13
Q

Describe the concept of balanced anaesthesia and the components/ drugs that encompass it

A

Hypnosis/ amnesia (iv/ inhalation anaesthetics)

Autonomic areflexia (opioids)

Immobility (NMB)

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14
Q

Name five types of IV anaesthetics

A

Barbituates, phenols, imidazoles, phenycyclidine derivatives, benzodiazepines

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15
Q

Describe the mechanism of action of IV anaesthetics

A

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.

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16
Q

General pharmacokinetics of IV agents

A

highly lipid soluble and cross BBB. Acts on Vessel Rich Group organs. Then redistribute into fat and muscle. Metabolism slow.

17
Q

Describe and give and example of brabituates

A

Thiopentone. Rapid onset, slow clearance, metabolised in liver, some decrease in peripheral resistance and BP, res depression and loss of airway reflexes. Used in emCS

18
Q

Describe and give examples of phenols

A

Propofol. Rapid onset and offset. Fast clearance. Used in maintanence infusion. Causes resp depression and decreased BP.

19
Q

Imidazoles

A

Etomidate. Good cardiovascular stability, rapid clearnace, causes adreno cortical inhibition. Causes myoclonus, epileptogenic.

20
Q

Benzodiazapams

A

Midazolam. Anti epileptic. Slow onset and offset limits use.

21
Q

Phencyclidine

A

Ketamine. Outlier- instead of GABA agonist, supresses excitation (glutamate at NMDA receptors). Has analgesic effect. Maintains airway reflexes, and res drive. Increases cerebral metabolic rate o2, CBF and ICP. complicated by dysphoria/ nightmares.