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Supp Neuro 5 > Anesthesia > Flashcards

Anesthesia Flashcards

1
Q

Definition of general anesthesia:

A

State of CNS depression

  • patient has complete absence of sensations and is unconscious
  • controlled AND reversible
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2
Q

Five goals of general anesthesia:

A
  1. loss of awareness or consciousness
  2. amnesia
  3. analgesia
  4. blunting of the autonomic nervous system (BANS)
  5. skeletal muscle relaxation
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3
Q

Two types of anesthetics:

A

Inhalation-gaseous

Injection

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4
Q

Dalton’s law as it applies to inhaled anesthetics:

A

P(total)=P(anesthetic) + P(oxygen)

**need oxygen pressure of 20.9% to survive so most you can have for the other gases is ~79% (usually need waaayyy less)

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5
Q

Henry’s Law as it applies to inhaled anesthetics:

A

Drug dissolved in fluid (blood) does NOT raise the partial pressure of the drug in that fluid

**clinical effect of drug is related to the amount of UNDISSOLVED drug in the blood

***analogous to the relationship between free and protein bound drugs in the blood

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6
Q

More anesthetic dissolved in blood means….

A

**takes longer to attain equilibrium (when undissolved drug can begin to have desired clinical effect)

**greater concentration of anesthetic at equilibrium

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7
Q

Compare drug partial pressure in delivered gas, inspired air, alveoli, arteries, and brain during:

Induction

At anesthesia

Recovery

A

Induction:
delivered gas > inspired air > alveoli > arteries > brain

At anesthesia:
inspired air = alveolar = arterial = brain

Recovery:
delivered gas < EXpired air < alveoli < VENOUS < brain

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8
Q

Describe drug solubility with respect to speed of onset for nitrous oxide, desflurane, sevoflurane, isoflurane, halothane:

A

Lease soluble Fastest onset
Nitrous oxide

                        desflurane

                          sevoflurane

                            isoflurane

                             halothane most soluble                                             slowest onset
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9
Q

Where in the body does anesthesia take place?

A

brain

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10
Q

All inhaled anesthetics share which characteristic (could be called only known mechanism of action)?

A

they all cause changes in membrane fluidity

**no know specific site of action

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11
Q

What is the dose of anesthetic (vol %) that produces surgical anesthesia in 50% of patients?

A

Minimum Alveolar Concentration (MAC)

**surgical anesthesia usually achieved around 1.3-1.5 MACs

deep anesthesia ensues around 2 MACs

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12
Q

Lowest MAC = ?

A

most potent

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13
Q

4 factors affecting MACs:

A

age

pre-existing disease

effects of other CNS depressants

ambient temp (ORs are COLD)

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14
Q

Amount of drug necessary to produce effect of specified intensity:

A

Potency

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15
Q

What does lipid solubility have to do with potency?

A

more lipid soluble = greater potency

**expressed as oil:gas partition coefficient

***don’t confuse with water (blood) solubility which deals with speed of onset (blood:gas partition coefficient)

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16
Q

Most potent inhaled anesthetic?

A

Halothane (oil:gas partition coefficient = 224)

17
Q

Fastest onset inhaled anesthetic?

A

Nitrous oxide (blood:gas partition coefficient = 0.5)

18
Q

Type of anesthetics that leave body most slowly?

A

fat soluble

19
Q

Three routes of elimination (inhaled anesthetics):

A

Lungs (primary)

skin and mucous membranes

can enter atmosphere (OR needs good ventilation!!)

20
Q

Only toxicologically important aspect of clearing inhaled anesthetics:

A

liberation of chemically reactive halides (bromide, chloride, and fluoride) can harm kidneys, liver, and reproductive organs

21
Q

CNS side effects of inhaled anesthetics:

A

decreased brain metabolic rate

increased cerebral blood flow

increased intracranial pressure

22
Q

CV side effects of inhaled anesthetics:

A

decreased myocardial contractility and stroke volume –> lower arterial pressure

sensitizes myocardium to catecholamines–>increased automaticity (adding epi could cause fatal arrhythmia!!)

23
Q

NON CNS or CV side effects of inhaled anesthetics?

A

respiratory depression (isoflurane, desflurane, sevoflurane > halothane > nitrous oxide)

muscle relaxation at high doses

Malignant hyperthermia (except nitrous), most common with halothane

24
Q

how do you treat malignant hyperthermia

pharmacologically?

physically?

A

dantrolene to block Ca+ release from sarcoplasmic reticulum

cool patient with ice bags/cold water

25
Q

Most potent inhaled anesthetic (MAC 0.7-0.9)

least expensive

no laryngeal irritation

higher risk for malignant hyperthermia

inadequate analgesia and muscle relaxation

A

Halothane

26
Q

Potent inhaled anesthetic

DOES not sensitize myocardium to catecholamines

Less hepatotoxicity

rare arrhythmias

pungent odor

potential for malignant hyperthermia

A

Isoflurane

27
Q

New inhaled anesthetic approved in 1996

high potency

low blood solubility (rapid onset, rapid recovery, almost perfect anesthetic)

A

Sevoflurane

28
Q

Only inhaled anesthetic that is actually a gas

low blood solubility–> rapid onset

little effect on CV function

mild to moderate analgesia

MAC = 104%, can’t use alone!!!!

no muscle relaxing effect

diffusion hypoxia if rapidly discontinued

A

Nitrous oxide

29
Q

Three advantages of injectable anesthetics:

A

act faster

best suited for INDUCTION of anesthesia

useful for short operations

30
Q

disadvantage of injectable anesthetics

A

muscle relaxation after IV is poor

-unsuitable as a single drug anesthetic

31
Q

5 injectable anesthetics:

A

barbiturates

benzodiazepines

propofol

ketamine

opiods

32
Q

Facilitates GABA induced Cl- entry into neurons leading to hyperpolerization and CNS depression

rapid onset (very lipid soluble)

short action (quick recovery)

Danger: toxicity, anesthetic dose is between 50-70% of LD50

A

Barbiturates

Thiopental and Methohexital

33
Q

Facilitates GABA induced Cl- entry into neurons leading to CNS depression

less CV suppression than barbiturates

most important for AMNESTIC action

insufficient for anesthesia when given alone

used as induction agent prior to anesthesia

A

benzodiazepines

Midazolam (Versed) and Diazepam (Valium)

34
Q

Rapid induction and recovery from anesthesia

May be given alone to maintain anesthesia or used for induction as part of balanced anesthesia technique

Must be given as emulsion patients generally awaken from anesthesia feeling more “clear headed” and are not nauseous (anti-emetic action)

Most significant respiratory effect is apnea (22-45%)

May result in injection site pain

A

Propofol (Diprivan)

**abused among providers “cat nap” deaths

35
Q

related to PCP

has dissociative effect

anesthetic, analgesic, amnestic, and sedative

airway reflexes and respiration maintained

may actually stimulate CV sys

drawback: may induce hallucination

abused at raves

possible depression tx

A

ketamine

36
Q

high potency, short acting

analgesia

anesthesia

hemodynamic stability- good for pts w compromised myocardial function

respiration must be maintained artificially

usually supplemented with inhaled anesthetic, benzos, or propofol

A

opiods

  • fentanyl
  • sufentanyl
  • alfentanil

Supp Neuro 5 (9 decks)

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