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Neurology 2 > General Anesthetics - Kruse > Flashcards

General Anesthetics - Kruse Flashcards

1
Q

5 goals of general anesthesia

How do you get all 5?

A

Unconscious
Amnesia
Analgesia
Attenuation of autonomic reflexes (to noxious stimuli)
Skeletal muscle relaxation (to noxious stimuli)

MUST combine 2 or more anesthetic drugs

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2
Q

Monitored anesthesia care

Drugs used (+ effects)

A

For: diagnostic/minor therapeutic surgical procedures
WITHOUT general anesthesia

Midazolam (amnesia, mild sedation) –> Propofol (deep sedation)
Ketamine/opioid (analgesia for injection/surgery)

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3
Q

Conscious sedation

Drugs used

Reversal?

A

Nonanesthesiologists (ex. dentist)
Pt can retain patent airway and respond to verbal cues

Benzo’s (diazepam/lorazepam) + opioid (fentanyl)

Receptor antagonists (Flumazenil, Naloxone)

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4
Q

Deep sedation

Drugs used (+ effects)

A

Low consiousness, not easily aroused
- Very similar to general anesthesia (fluid transition)
Loss of protective reflexes and verbal responses

Propofol/midazolam (sedative) + opioid/ketamine (analgesia)

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5
Q

Where do general anesthetics function?

A

CNS

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6
Q

2 functional groups of general anesthetics

A
  1. Cl- channel (GABA-A, Glycine) and K+ channel agonists

2. ACh receptor (nAChR, mAChR), EAA receptor (NMDA, AMPA), and 5-HT receptor (2 and 3) antagonists

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7
Q

2 groups of INHALED anesthetics (w/ members of each)

A

Volatile = low vapor pressure, liquid at normal pressure
- Halothane, Enflurane, Isoflurane, Desflurane, Sevoflurane)

Gaseous = high vapor pressure, gas normal pressure
- NITROUS OXIDE (N.O.)

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8
Q

How do inhaled anesthetics get into the blood?

A

Alveoli –> blood stream

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9
Q

Driving force for uptake from alveoli is ______

A

Alveolar concentration

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10
Q

2 factors that determine alveolar concentration

Relationship w/ anesthetic induction

A 
Inspired concentration (dose)
Alveolar ventilation (gas exchange rate w/ blood)

Increase in EITHER = faster induction/fxn of drug

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11
Q

Equation for determining inhaled induction rate

Meaning of value?

A

Fa (alveolar [ ]) / Fi (inspired [ ])

Closer to 1 = faster induction

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12
Q

3 factors that affect drug uptake

A

Solubility (in gas vs. blood vs. brain)
Cardiac output
Rate of tissue uptake

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13
Q

Important factor related to overall solubility of an inhaled drug

A

Blood:gas partition coefficient

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14
Q

Blood:gas partition coefficient

Meaning?

A

Affinity for blood vs. gas

HIGH solubility (blood) = SLOW onset and recovery
LOW solubility (blood) = FAST onset and recovery
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15
Q

Drugs w/ HIGH blood solubility

SO, what about these drugs?

A

Halothane, Enflurane, Isoflurane

Slower rate of onset and recovery

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16
Q

Drugs w/ LOW blood solubility

SO, what about these drugs?

A

Nitrous oxide, Desflurane, Sevoflurane

Rapid onset and recovery

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17
Q

Describe why high blood solubility leads to slower onset

A

High solubility = more ability to “spread out” throughout the blood stream, w/ less desire to “get out”

Won’t be taken up by the tissues as rapidly if it’s comfortable floating in the blood for a while

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18
Q

Rank the 6 inhalation anesthetics for rate of onset from FASTEST to SLOWEST

A
  1. N.O.
  2. Desflurane
  3. Sevoflurane
  4. Isoflurane
  5. Enflurane
  6. Halothane
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19
Q

Higher cardiac output correlates with a (faster or slower) rate on onset?

A

SLOWER

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20
Q

How do opioids for analgesia affect the rate of action, etc. of the inhaled anesthetics?

A

Opioid –> respiratory depression –> slowed onset of anesthesia (inhaled)

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21
Q

Clearance of inhaled anesthetics

A

MAJOR = lungs

Some hepatic enzyme metabolism

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22
Q

Rate the 6 inhaled anesthetic drugs in terms of metabolism in the liver (MOST to LEAST)

A
  1. Halothane
  2. Enflurane
  3. Sevoflurane
  4. Isoflurane
  5. Desflurane

N.O. = NONE

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23
Q

Effects of BMI on anesthetics

A

Accumulation in muscle, skin, and fat can cause prolonged duration of action (slower recovery) as the drugs are slowly eliminated from these tissues

HIGHER WEIGHT = SLOWER RECOVERY

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24
Q

Inhalted anesthetic potency is measured by what?

A

MAC (minimal alveolar concentration/percentage) required to produce an anesthetic effect

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25
Q

Rank the 6 inhalation anesthetics in terms of potency (inverse of MAC) from MOST to LEAST potent

A
  1. Halothane
  2. Isoflurane
  3. Enflurane
  4. Sevoflurane
  5. Desflurane
  6. Nitrous oxide (VERY NOT POTENT)
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26
Q

Important of NITROUS OXIDE in regards to potency

A

MAC > 100
THUS, it is IMPOSSIBLE to achieve full surgical anesthesia on nitrous oxide alone

MUST supplement with another agent

27
Q

How does MAC/potency relate to solubility?

A

Higher solubility = lower MAC = higher potency

28
Q

4 states of CNS depression

A
  1. Analgesia only –> amnesia at end of STAGE 1
  2. Delirious, irregular respirations, vomiting w/ stimuli –> regular breathing at end of STAGE 2
  3. Regular breathing –> complete cessation of spontaneous respiration at end of STAGE 3
  4. Depression of vasomotor (lungs, heart) centers in medulla
29
Q

Which stage of CNS depression is required for surgery?

What is special about this?

A

Stage 3

DEATH without respiratory support

30
Q

What is special about Stage 4?

A

DEATH without circulatory AND respiratory support

31
Q

Signs that the patient is successfully in stage 3

A
  1. Loss of response to pain (squeezing traps)

2. Regular breathing re-established

32
Q

Potentially dangerous side effect of inhaled anesthetics

Dangerous when?

A

Increase cerebral blood flow

Do NOT use in patient w/ increased ICP

33
Q

Effects of different inhaled anesthetics on CV system (4)

A
  1. Volatile ones (5/6) –> decreased M.A.P. (dose-dependent)
  2. Halothane –> bradycardia
  3. Desflurane/Isoflurane –> tachycardia
  4. ALL –> increased R atrial pressure (depress myocardium)
34
Q

General toxicity of inhaled anesthetics

A

Nausea and vomiting

35
Q

Toxicity of Halothane

A

Hepatitis (anorexia, nausea, myalgias, arthralgias, rash, jaundice, hepatomegaly)

36
Q

Toxicity of Enflurane/Sevoflurane

A

Renal toxicity (due to fluoride ion metabolites)

37
Q 
Rapid onset tachycardia
Hypertension
Severe muscle rigidity
Rhabdomyolysis
Hyperthermia
Hyperkalemia
Acidosis
A

Malignant hyperthermia

Volatile (inhaled) anesthetic + succinylcholine

38
Q

Antidote to malignant hyperthermia

A

Dantrolene

39
Q

When are inhalation anesthetics mostly used now (rather than IV)

A

Pediatrics

40
Q

Why do IV anesthetics have such quick CNS action?

A

Lipophilic –> prefer lipophilic tissues (brain, spinal cord)

41
Q

Propofol function

A

GABA-A receptor (Cl-) potentiation

42
Q

Patient has egg allergy. What not to give?

A

Propofol

43
Q

Benefits of Propofol (3)

A

Rapid onset (15-30 sec), rapid recovery
- Great for short duration (outpatient) procedures
Half-life hardly changes w/ time or long-term use
- Great for anesthesia maintenance
Reduction in upper airway reflexes
- Great for airway instrumentation (laryngeal mask airway)

44
Q

Side effects of Propofol (2)

A
  1. VERY PRONOUNCED vasodilation –> decreased BP + inhibition of normal baroreflex response
    • Treat w/ alpha-agonist?
  2. Pain on injection (requires opioid/lidocaine pre-med)
45
Q

A doctor is going to use Propofol. What else must be administered?

A

Analgesic (Propofol has no analgesic effect)

46
Q

Fospropofol (vs. Propofol)

Side effects

A
  1. Pro-drug of Propofol –> prolonged onset and recovery
    (requires conversion into active form)
  2. Less pain on administration

Paresthesias (burning/tingling) and pruritis (itching) w/in FIRST 5 MINUTES

47
Q

Etomidate function

A

Enhance GABA action on GABA-A

48
Q

Benefit of Etomidate

A

Minimal CV and respiratory depression

- Great for patients w/ impaired CV/resp. systems

49
Q

Side effect of Etomidate

So?

A

Adrenocortical/cortisol suppression (inhibits 11-hydroxylase)
- Limits use from continuous infusion

50
Q

Ketamine function

A

NMDA (Glutamate) receptor antagonist

51
Q

Key signs of ketamine use

A

Patient’s eyes remain open w/ slow nystagmic gaze

Increased lacrimation and salivation

52
Q

Function of ketamine NOT in propofol or etomidate

A

Analgesia AS WELL AS catatonia and amnesia

53
Q

Before use of ketamine, what may be indicated as a pre-med?

A

Anticholinergic (for the lacrimation and salivation)

54
Q

Caveat to ketamine use

A

Increases cerebral blood flow

DO NOT use in patient w/ intracranial pathology

55
Q

Limiting factor for ketamine use

A

Emergence reactions (vivid dreams, hallucinations, out-of-body experiences, distored/increased sensations)

56
Q

Why is ketamine special? (4)

A

ONLY IV anesthetic to…

- Produce PROFOUND analgesia
- Stimulate sympathetic nervous system
- Bronchodilate
- LITTLE respiratory depression
57
Q

Functions of Dexmedetomidine

Used for what?

A

Alpha-2 agonist –> hypnosis (physiologic sleep state)
Analgesia w/in spinal cord

Short-term sedation of intubated/ventilated ICU patients

58
Q

To use Dexmedetomidine, what may be indicated as well?

A

Treatment for bradycardia (beta-1 agonist?)

59
Q

What is often used to provide analgesia during operation?

Examples?

A

Opioids

Fentanyl, Sufentanil, Remifentanil, Morphine

60
Q

Function of barbituates

2 examples?

A

Enhance GABA-A Cl- channel opening

Thiopental (slower elim.), Methohexital (faster elim.)

61
Q

Function of benzodiazepines

3 examples?

A

GABA-A receptor increased sensitivity to GABA

Diazepam, Lorazepam, Midazolam

62
Q

Use of benzodiazepines in anesthetics?

A

Anxiolysis (anti-anxiety) and amnesia

63
Q

Antagonism of benzodiazepines?

A

Flumazenil

Neurology 2 (22 decks)

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