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Pharmacology > Anaesthesia > Flashcards

Anaesthesia Flashcards

1
Q

what do general anesthetics do?

A

depress the CNS to produce loss of consciousness, loss of responsiveness to sensory stimuli, including pain and relaxation of muscles

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2
Q

how are general anesthetics administered?

A

either volatile liquids or gases vaporized in oxygen and administered by inhalation or non-volatile liquids applied by injection

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3
Q

general anesthesia involves:

A

1-analgesia (opioids)

2- amnesia (barbiturates)

3- inhibition of reflexes (a variety of drugs)

4- skeletal muscle relaxation (NMJ blocking agents)

5- rapid hypnosis (barbiturates and other drugs)

***no drug can currently produce all 5 responses thus combinations of drugs are used to produce a balanced anesthesia

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4
Q

combination of drugs can:

A

reduce the requirement for inhaled anesthetics
minimize their side effects
increase their safety

in addition, the doses of barbiturates, opioids, NMJ blocking agents, etc can be reduced, also increasing safety

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5
Q

what are barbiturates?

A

depress the CNS

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6
Q

what are the stages of general anesthesia?

A

stage I: analgesia

stage II: excitement

stage III: surgical anesthesia

stage IV: imminent death

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7
Q

stage I of general anesthesia:

A

analgesia: inability to feel pain

normal respiration
voluntary control of ocular movement
normal pupil size
normal eye reflexes
normal muscle tone
normal reps response to skin incision
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8
Q

stage II of general anesthesia:

A

excitement and hyperactivity

dilated pupils
eyelid reflexes
tense muscle tone

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9
Q

stage III of general anesthesia:

A

surgical anesthesia
4 planes

respiration gradually decreases
eye motion decreases
pupils constrict in planes 1& 2 then dilate
eye reflexes decrease
muscle tone decreases
in plane 3 no respiratory response to skin incision

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10
Q

stage IV of general anesthesia:

A

imminent death; paralysis of the medulla

apnea
dilated pupils
flaccid muscle tone
no reps response

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11
Q

what are the 2 types of inhaled general anesthetics?

A

1- gas
-nitrous oxide

2- volatile liquid

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12
Q

general adverse effects of gas inhaled general anesthetics:

A 
COMMON
dizziness
drowsiness
nausea
euphoria
vomiting

SERIOUS
malignant hyperthermia
apnea
cyanosis

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13
Q

general adverse effects of volatile liquid general anesthetics:

A

COMMON
drowsiness
nausea
vomiting

SERIOUS
myocardial depression
marked hypotension
pulmonary vasocontriction
heptotoxicity
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14
Q

dosages of gas inhaled general anesthetics are expressed as:

A

alveolar concentrations such as the minimum alveolar concentration (MAC)

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15
Q

what is MAC?

A

Minimum Alveolar Concentration=

concentration at which 50% of the patients do not move during surgery. This is the percent of the gas mixture or percent of 760 mm Hg pressure

MAC is an index of the potency of an inhaled anesthetic

MAC has a very steep dose-response curve and is inversely proportional to anesthetic potency

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16
Q

how does age affect MAC?

A

lower in the elderly

  • not affected by sex, height or weight
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17
Q

the higher the % of MAC required, the ______the drug

A

less potent

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18
Q

what is lipophilicity?

A

the ability of a chemical compound to dissolve in fats, lipid, oils, etc

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19
Q

what is lipophilicity mechanism of action?

A

extremely lipophilic, therefore, their solubility disrupts the membrane lipid bilayer of cells, thus increasing the threshold to fire

the more lipid soluble an agent is, the more potent anesthetic it becomes = Myer-Overton Principle

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20
Q

what is MAC influenced by?

A

1- PULMONARY VENTILATION

2- PULMONARY BLOOD FLOW

3- WATER SOLUBILITY

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21
Q

how does pulmonary ventilation affect MAC?

A

can affect speed of induction- thus the more rapidly air is exchanged, the more rapidly anesthesia will be achieved

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22
Q

how does pulmonary blood flow affect MAC?

A

affects how quickly an anesthetic leaves the alveolus and enters the blood. the faster blood flows by the alveolus, the longer it takes to increase blood concentration of anesthetic.

Conversely, the more slowly blood passes the alveolus (due to decreased BP or decreased blood volume), the more rapidly anesthesia is induced

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23
Q

how does water solubility affect MAC?

A

anesthetics which are not very water soluble (lipid soluble) build up rapidly in the alveolus and approach the concentration required to produce unconscious.

A more water soluble drug will first mix in the large watery blood reservoir before sufficient concentrations are achieved in the alveolus to induce unconsciousness

24
Q

what are the pharmacological effects of anesthesia?

A

1- block flow of sodium into neurons

2- enhance the inhibitory action of GABA

3- delays impulses and reduces neural activity

4- produces unconsciousness

5- produces lack of responsiveness to painful stimuli

25
Q

when and why are intravenous anesthetics used?

A

used in situations that require short duration anesthesia (outpatient surgery)

used to supplement inhalation anesthetics

primarily used as adjuncts to inhalation agents

administered first

rapidly induce unconsciousness

26
Q

what are some types of IV anesthetics?

A

Barbiturate

Benzodiazepines

Opioids

Propofol

Ketamine

27
Q

Barbiturates:

A

Thiopental
Methohexital

*rapid onset and potent, but no analgesia

28
Q

benzodiazepines:

A

Diazepam
Lorazepam
Midazolam

*produce sedation but not analgesia; produce amnesia

29
Q

Opioids:

A

Fentanyl

*good analgesia; for intro-operative pain

30
Q

Propofol:

A

commonly used for sedation during procedures or in the ICU

31
Q

Ketamine:

A

rarely used in adults, good analgesia, produces delusions

32
Q

adjuncts to anesthesia:

A

barbiturates

opioids

anticholinergic

dopamine blocker

phenothiazine

neuromuscular blocker

33
Q

what are the 5 techniques for applying local anesthesia?

A 
topical
nerve block
infiltration
spinal
epidural
34
Q

what are local anesthetics?

A

amides and esters

stop axonal conduction
block sodium channels
causes rapid loss of sensation in limited part of body

35
Q

local anesthetics reversibly block:

A

impulse conduction along nerve axons that utilize sodium channels to generate an AP

cocaine was the first such agent used but then abandoned due to its addictive properties

36
Q

local anesthetics may be contraindicated in patients with:

A

cardiovascular conditions because they have anti arrhythmic properties

37
Q

types of local anesthetics:

A

short acting procaine (1 hour)

intermediate acting lidocaine (1-2.5 hours)

long acting tetracaine (3-9 hours)

38
Q

why are vasoconstrictor substances (such as NE) co-administered with local anesthetics?

A

to limit absorption and concentrate them at the site of injection

39
Q

how are topical anesthetics applied?

A

directly to the skin or mucous membranes

40
Q

what is the major topical anesthetic?

A

Benzocaine

Lidocaine and tetracaine can also be used topically

41
Q

topical anesthetics are used to:

A

relieve or prevent pain from minor burns, irritation, itching

also used to numb an area before an injection is given

42
Q

what are expected adverse effects of topical anesthetics?

A

skin irritation

hypersensitivity reactions

43
Q

what are muscle relaxants?

A

drugs that affect skeletal muscle function

44
Q

what are the 2 groups of muscle relaxants?

A

Neuromuscular blockers (NMJ)

Spasmolytics

45
Q

what are NMJ blockers used for?

A

used in intensive care units to cause paralysis and as an adjunctive to anesthesia

indicated to relax skeletal muscles during surgery

to reduce the intensity of muscle spasms in electrically-induced convulsions

to manage patients who are fighting mechanical ventilation

nondepolarizing vs. depolarizing agents

46
Q

what are spasmolytics used for?

A

used to reduce spasticity in a variety of neurologic disorders

47
Q

what are non depolarizing agents?

A

curare alkaloids such as tubocurarine, pancuronium bromide, pipecuronium and vecuronium.

they block neurotransmitter action of ACh. NMJ agents do not cross the BBB and have no action on the CNS. For this reason, anesthesia is induced before neuromuscular blockade is started.

The neuromuscular blocking actions of tubocurarine may be revered with anticholinesterases such as neostigmine, pyridostigmine and edrophonium

48
Q

what are depolarizing agents ?

A

(succinylcholine) cause excessive depolarization which desensitizes muscles and renders them UNREPSONSIVE

(depolarization– increased permeability to Na+ and K+)???

49
Q

what is spasticity?

A

increase in tonic stretch reflexes

increased flexor muscle spasm

muscle weakness

reflex arc involvement

higher center involvement (“UMND”) affects descending pathways leading to alpha motor neurons hyper-excitability

50
Q

what are spasmolytics?

A

skeletal muscle relaxing agents that relieve acute musculoskeletal pain, spasm or spasticity

51
Q

types of spasmolytics (central)?

A

Carisoprodol

Baclofen

Diazepam

Tizanidine

52
Q

carisoprodol is primarily used to:

A

used to treat acute, painful musculoskeletal conditions due to trauma, inflammation, and anxiety.

other drugs used for acute spasticity include:
Chlorphenesin
Chlorzoxazone
Cyclobenzaprine
Metaxalone
Methocarbamol
Orphenadrine
53
Q

Baclofen is a:

A

GABA analog acting at GABAb receptors which depresses neuronal activity, decreasing the frequency and degree of muscle spasms and reduces muscle tone.

It is the drug of choice bc it produces less sedation than diazepam and less peripheral muscle weakness that dantrolene.

used for paraplegic or quadriplegic patients with SC lesions caused by either MS or trauma

Intrathecal Baclofen used for management of severe spasticity/pain when non responsive to medication by other routes of administration

54
Q

diazepam is effective for:

A

both acute spasms and chronic spasticity.

indicated for patients with SC lesions or those with Cerebral palsy

anti-spasmolytic effect in part due to action in the SC (effective in patients with cord transection)

55
Q

Tizanidine is related to:

A

clonidine

enhances both pre and postsynaptic inhibition in the SC. also inhibits nociceptive transmission (dorsal horn)

56
Q

what are spasmolytics (peripheral)?

A

Dantrolene

57
Q

what is dantrolene?

A

has similar effects to other central drugs but it works directly on the muscle by inhibiting calcium release necessary for muscle relaxation.

it is most effective for spasticity with cerebral origin (MS, Cerebral palsy)

Pharmacology (8 decks)

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