Anaesthesia

Question 1

what do general anesthetics do?

Answer 1

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

Question 2

how are general anesthetics administered?

Answer 2

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

Question 3

general anesthesia involves:

Answer 3

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

Question 4

combination of drugs can:

Answer 4

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

Question 5

what are barbiturates?

Answer 5

depress the CNS

Question 6

what are the stages of general anesthesia?

Answer 6

stage I: analgesia

stage II: excitement

stage III: surgical anesthesia

stage IV: imminent death

Question 7

stage I of general anesthesia:

Answer 7

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

Question 8

stage II of general anesthesia:

Answer 8

excitement and hyperactivity

dilated pupils
eyelid reflexes
tense muscle tone

Question 9

stage III of general anesthesia:

Answer 9

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

Question 10

stage IV of general anesthesia:

Answer 10

imminent death; paralysis of the medulla

apnea
dilated pupils
flaccid muscle tone
no reps response

Question 11

what are the 2 types of inhaled general anesthetics?

Answer 11

1- gas
-nitrous oxide

2- volatile liquid

Question 12

general adverse effects of gas inhaled general anesthetics:

Answer 12

COMMON
dizziness
drowsiness
nausea
euphoria
vomiting

SERIOUS
malignant hyperthermia
apnea
cyanosis

Question 13

general adverse effects of volatile liquid general anesthetics:

Answer 13

COMMON
drowsiness
nausea
vomiting

SERIOUS
myocardial depression
marked hypotension
pulmonary vasocontriction
heptotoxicity

Question 14

dosages of gas inhaled general anesthetics are expressed as:

Answer 14

alveolar concentrations such as the minimum alveolar concentration (MAC)

Question 15

what is MAC?

Answer 15

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

Question 16

how does age affect MAC?

Answer 16

lower in the elderly

• not affected by sex, height or weight

Question 17

the higher the % of MAC required, the ______the drug

Answer 17

less potent

Question 18

what is lipophilicity?

Answer 18

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

Question 19

what is lipophilicity mechanism of action?

Answer 19

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

Question 20

what is MAC influenced by?

Answer 20

1- PULMONARY VENTILATION

2- PULMONARY BLOOD FLOW

3- WATER SOLUBILITY

Question 21

how does pulmonary ventilation affect MAC?

Answer 21

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

Question 22

how does pulmonary blood flow affect MAC?

Answer 22

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

Question 23

how does water solubility affect MAC?

Answer 23

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

Question 24

what are the pharmacological effects of anesthesia?

Answer 24

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

Question 25

when and why are intravenous anesthetics used?

Answer 25

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

Question 26

what are some types of IV anesthetics?

Answer 26

Barbiturate Benzodiazepines Opioids Propofol Ketamine

Question 27

Barbiturates:

Answer 27

Thiopental Methohexital *rapid onset and potent, but no analgesia

Question 28

benzodiazepines:

Answer 28

Diazepam Lorazepam Midazolam *produce sedation but not analgesia; produce amnesia

Question 29

Opioids:

Answer 29

Fentanyl *good analgesia; for intro-operative pain

Question 30

Propofol:

Answer 30

commonly used for sedation during procedures or in the ICU

Question 31

Ketamine:

Answer 31

rarely used in adults, good analgesia, produces delusions

Question 32

adjuncts to anesthesia:

Answer 32

barbiturates opioids anticholinergic dopamine blocker phenothiazine neuromuscular blocker

Question 33

what are the 5 techniques for applying local anesthesia?

Answer 33

``` topical nerve block infiltration spinal epidural ```

Question 34

what are local anesthetics?

Answer 34

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

Question 35

local anesthetics reversibly block:

Answer 35

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

Question 36

local anesthetics may be contraindicated in patients with:

Answer 36

cardiovascular conditions because they have anti arrhythmic properties

Question 37

types of local anesthetics:

Answer 37

short acting procaine (1 hour) intermediate acting lidocaine (1-2.5 hours) long acting tetracaine (3-9 hours)

Question 38

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

Answer 38

to limit absorption and concentrate them at the site of injection

Question 39

how are topical anesthetics applied?

Answer 39

directly to the skin or mucous membranes

Question 40

what is the major topical anesthetic?

Answer 40

Benzocaine Lidocaine and tetracaine can also be used topically

Question 41

topical anesthetics are used to:

Answer 41

relieve or prevent pain from minor burns, irritation, itching also used to numb an area before an injection is given

Question 42

what are expected adverse effects of topical anesthetics?

Answer 42

skin irritation | hypersensitivity reactions

Question 43

what are muscle relaxants?

Answer 43

drugs that affect skeletal muscle function

Question 44

what are the 2 groups of muscle relaxants?

Answer 44

Neuromuscular blockers (NMJ) Spasmolytics

Question 45

what are NMJ blockers used for?

Answer 45

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

Question 46

what are spasmolytics used for?

Answer 46

used to reduce spasticity in a variety of neurologic disorders

Question 47

what are non depolarizing agents?

Answer 47

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

Question 48

what are depolarizing agents ?

Answer 48

(succinylcholine) cause excessive depolarization which desensitizes muscles and renders them UNREPSONSIVE (depolarization-- increased permeability to Na+ and K+)???

Question 49

what is spasticity?

Answer 49

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

Question 50

what are spasmolytics?

Answer 50

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

Question 51

types of spasmolytics (central)?

Answer 51

Carisoprodol Baclofen Diazepam Tizanidine

Question 52

carisoprodol is primarily used to:

Answer 52

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 ```

Question 53

Baclofen is a:

Answer 53

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

Question 54

diazepam is effective for:

Answer 54

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)

Question 55

Tizanidine is related to:

Answer 55

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

Question 56

what are spasmolytics (peripheral)?

Answer 56

Dantrolene

Question 57

what is dantrolene?

Answer 57

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)