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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
Rank the 6 inhalation anesthetics in terms of potency (inverse of MAC) from MOST to LEAST potent
1. Halothane 2. Isoflurane 3. Enflurane 4. Sevoflurane 5. Desflurane 6. Nitrous oxide (VERY NOT POTENT)
26
Important of NITROUS OXIDE in regards to potency
MAC > 100 THUS, it is IMPOSSIBLE to achieve full surgical anesthesia on nitrous oxide alone MUST supplement with another agent
27
How does MAC/potency relate to solubility?
Higher solubility = lower MAC = higher potency
28
4 states of CNS depression
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
Which stage of CNS depression is required for surgery? What is special about this?
Stage 3 DEATH without respiratory support
30
What is special about Stage 4?
DEATH without circulatory AND respiratory support
31
Signs that the patient is successfully in stage 3
1. Loss of response to pain (squeezing traps) | 2. Regular breathing re-established
32
Potentially dangerous side effect of inhaled anesthetics Dangerous when?
Increase cerebral blood flow Do NOT use in patient w/ increased ICP
33
Effects of different inhaled anesthetics on CV system (4)
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
General toxicity of inhaled anesthetics
Nausea and vomiting
35
Toxicity of Halothane
Hepatitis (anorexia, nausea, myalgias, arthralgias, rash, jaundice, hepatomegaly)
36
Toxicity of Enflurane/Sevoflurane
Renal toxicity (due to fluoride ion metabolites)
37
``` Rapid onset tachycardia Hypertension Severe muscle rigidity Rhabdomyolysis Hyperthermia Hyperkalemia Acidosis ```
Malignant hyperthermia Volatile (inhaled) anesthetic + succinylcholine
38
Antidote to malignant hyperthermia
Dantrolene
39
When are inhalation anesthetics mostly used now (rather than IV)
Pediatrics
40
Why do IV anesthetics have such quick CNS action?
Lipophilic --> prefer lipophilic tissues (brain, spinal cord)
41
Propofol function
GABA-A receptor (Cl-) potentiation
42
Patient has egg allergy. What not to give?
Propofol
43
Benefits of Propofol (3)
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
Side effects of Propofol (2)
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
A doctor is going to use Propofol. What else must be administered?
Analgesic (Propofol has no analgesic effect)
46
Fospropofol (vs. Propofol) Side effects
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
Etomidate function
Enhance GABA action on GABA-A
48
Benefit of Etomidate
Minimal CV and respiratory depression | - Great for patients w/ impaired CV/resp. systems
49
Side effect of Etomidate So?
Adrenocortical/cortisol suppression (inhibits 11-hydroxylase) - Limits use from continuous infusion
50
Ketamine function
NMDA (Glutamate) receptor antagonist
51
Key signs of ketamine use
Patient's eyes remain open w/ slow nystagmic gaze | Increased lacrimation and salivation
52
Function of ketamine NOT in propofol or etomidate
Analgesia AS WELL AS catatonia and amnesia
53
Before use of ketamine, what may be indicated as a pre-med?
Anticholinergic (for the lacrimation and salivation)
54
Caveat to ketamine use
Increases cerebral blood flow DO NOT use in patient w/ intracranial pathology
55
Limiting factor for ketamine use
Emergence reactions (vivid dreams, hallucinations, out-of-body experiences, distored/increased sensations)
56
Why is ketamine special? (4)
ONLY IV anesthetic to... - Produce PROFOUND analgesia - Stimulate sympathetic nervous system - Bronchodilate - LITTLE respiratory depression
57
Functions of Dexmedetomidine Used for what?
Alpha-2 agonist --> hypnosis (physiologic sleep state) Analgesia w/in spinal cord Short-term sedation of intubated/ventilated ICU patients
58
To use Dexmedetomidine, what may be indicated as well?
Treatment for bradycardia (beta-1 agonist?)
59
What is often used to provide analgesia during operation? Examples?
Opioids Fentanyl, Sufentanil, Remifentanil, Morphine
60
Function of barbituates 2 examples?
Enhance GABA-A Cl- channel opening Thiopental (slower elim.), Methohexital (faster elim.)
61
Function of benzodiazepines 3 examples?
GABA-A receptor increased sensitivity to GABA Diazepam, Lorazepam, Midazolam
62
Use of benzodiazepines in anesthetics?
Anxiolysis (anti-anxiety) and amnesia
63
Antagonism of benzodiazepines?
Flumazenil

Neurology 2 (22 decks)

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