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Neuro Block 5 > Anesthesia > Flashcards

Anesthesia Flashcards

0
Q

Why is it difficult to uncover the precise cellular mechanisms of anesthetic action?

A

Because they don’t act on any receptors (inhalation)

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1
Q

What are the four stages of anesthesia?

A
  1. Analgesia and amnesia
    - starts with induction and ends with loss of consciousness
    - Px can still respond, may include voluntary resistance (good)
  2. Delirium
    - agitation, combative, REM, breath holding, vomiting, and laryngospasm
    - BP and respiration fluctuate (bad)
  3. Surgical anesthesia
    - respiration levels, autonomic reflexes my depress depending on concentrations
    - 4 plans of anesthesia based on: eye movements depth of respiration, and molecular relaxation: light, moderate, deep, excessive (good)
  4. Medullary depression
    - stage of relative overdose
    - maintenance of this stage may result in CV collapse and severe respiratory depression
    (Bad)
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2
Q

What are some theories used to describe the mechanism of anesthetics?

A

Inhalation - very lipid soluble, change the membrane –> all receptors are altered –> neurotransmitters don’t fit anymore

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3
Q

What is meant by balanced anesthesia?

A

Combined use of drugs to get:

  • Loss of awareness or consciousness (general a)
  • amnesia (benzodiazepine)
  • analgesia, BANS (opioid)
  • skeletal muscle relaxation (skeletal muscle relax)
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4
Q

What are some general pharmacological characteristics of inhalation anesthetics?

A
  • Diverse chemical structure
  • Do not interact with pharmacologically defined receptors
  • impact all physiological systems
  • cause physical changes (cell membrane fluidity)
  • all alter membrane fluidity
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5
Q

Why is the partial pressure of an inhalation anesthetic more important in producing an effect than blood concentrations of the agent?

A

Because amount of undissolved drug in the blood is related to clinical effect

The more anesthetic in the blood the longer it takes to reach eq, and the greater the concentration and eq

Analogous to free and protein bound drugs in blood

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6
Q

What is the basis of the MAC value and why is it a useful index in anesthesiology?

A 
Equivalent of ED50
Dose of a anesthetic by volume % that produces surgical anesthesia in 50% of Pxs 
Lowest MAC is most potent
Usually need 1.3-1.5
Deep anesthesia ensues at about 2MAC
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7
Q

Why can’t you produce surgical anesthesia with nitrous oxide?

A

The MAC is 104 so you would need 104% of the drug to produce the effect in only 50% of Pxs

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8
Q

Compare what the blood:gas and oil:gas partition coefficients tell you about the characteristics of an anesthetic agent and discuss why the rate of anesthesia induction is slower when you use agents that are more soluble in blood.

A

More blood soluble the drug is the slower it gets to eq and therefore the slower the induction

The more lipid soluble a drug is the greater it’s potency

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9
Q

What are the variables that influence anesthetic recovery and anesthetic elimination from the body?

A

The second gas effect, can pull or push a drug in/out

Fat-soluble anesthetics leave the body fat slowest

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10
Q

Which properties make some anesthetics more useful than others?

A

Higher lipid solubility
Low blood solubility
Higher vapor point

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11
Q

What is BANS?

A

Blunting of the autonomic nervous system (BANS)

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12
Q

What is the second gas effect?

A

Rapid uptake of the first anesthetic creates negative pressure and pulls in another drug

(Can be crap, maybe just analgesic effects of nitrous)

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13
Q

What is diffusion hypoxia?

A

Not able to get oxygen because the nitrous rapidly goes into the alveoli leaving now room for oxygen

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14
Q

What is MAC

A

Minimum alveolar concentration

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15
Q

What are characteristics of an ideal inhalation anesthetic?

A 
Low solubility of the anesthetic in blood
Inexpensive
Nonflammable or explosive
Easily vaporized
Potent
No cardiopulmonary depression
No airway irritation
No interaction with catecholamines
Good muscle relaxation
Minimal metabolism 
Not toxic to kidneys, liver, or gut
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16
Q

What are common aspects of all halogenated anesthetics?

A
  • Increase ICP
  • Decrease brain metabolic rate
  • Increase cerebral blood flow
  • CV: decreased myocardial contractile try and stroke volume leading to lower atrial BP. Sensitize myocardium to catecholamines
  • respiratory depression (isoflurane first)
  • muscle relaxant at high doses
  • malignant hyperthermia (except nitrous oxide, most seen with halothane)
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17
Q

What are advantages and disadvantages of using halothane to produce general anesthetics?

A

Advantage: potent, rapid induction/recovery, least expensive volatile, no laryngospasm
Disadvantage:
-Inadequate analgesia and muscle relaxant
-Depresses myocardium and Baroreceptor reflexes
(Low cardiac output and BP)
-sensitizes myocardium to catecholamines
(Up automaticity, particularly with epinephrine, increased cerebral blood flow and ICP)
-respiratory depression
-Hepatic toxicity
-malignant hyperthermia (treat with dantrolene to block calcium release from sarcoplasm)

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18
Q

Compare effects of halothane with isoflurane, methoxyflurane, and desflurane.

A

A

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19
Q

Why or why not is sevoflurane the perfect anesthetic?

A

High potency
Low blood solubility
Rapid onset (5-10)
Same day surgery

20
Q

How does nitrous oxide compare to other inhalation anesthetics?

A

It sucks, well fast effect but it takes way to much to produce an analgesic effect

21
Q

Why are injectable anesthetics often used for anesthesia induction as well as for short-duration anesthesia?

A

Act faster,

22
Q

How does drug distribution, redistribution, and drug accumulation influence the administration and use of injectable anesthetics?

A

A

23
Q

What is meant by dissociative anesthetic, give an example and discuss when it might best be used for anesthesia?

A

Not necessarily unconscious
Px appears to be awake - eyes open
Unaware of enviornment feels no pain

Ketamine - used with Pxs who have unstable CV, actually ups HR and BP
1-2 min IM or IV induction
Short procedures (20min)

24
Q

What is the rationale for use of opioids as anesthetics?

A
  • High potency and short acting
  • Analgesia + anesthesia
  • Hemodynamic stability - good for Pxs with compromised myocardial function
  • respiration must be maintained however
  • usually supplemented with inhalation, benzodiazepine or propofol
25
Q

What is meant by general anesthesia?

A

General state of CNS depression

Complete absence of sensations and unconscious
Controlled and reversible

26
Q

What are the two types of general anesthesia?

A

Inhalation - gaseous

Injection

27
Q

What is Dalton’s law?

A

Total pressure of a gas mixture equals the sum of partial pressures of each gas.

In inhalation anesthetics O2 (20.9) and the anesthetics

28
Q

What is Henry’s law?

A

Number of gas molecules that enter a liquid before eq has been reached is determined by the solubility of the gas in the liquid

Drugs dissolved in fluid do not raise the partial pressure in that fluid

29
Q

What is the most potent inhalation anesthetic?

A

Halothane (most lipid soluble)

30
Q

What are MAC related factors?

A

Age
Pre-existing diseases
Effects of other CNS depressants
Ambient temp (need cold)

31
Q

What is potency a function of and what does it mean?

A

Function of lipid solubility (oil:gas)

The more lipid soluble an anesthetic the greater its potency

32
Q

How is lipid solubility expressed?

A

In oil:gas partition coefficient

33
Q

Why must you do surgery with anesthetics in a well ventilated room?

A

Only a little leaves through the lungs, most leaves through the Pxs skin and mucous membranes

From there it can enter you! And produce anesthetic effects

Also biotransformation: halogenated anesthetics can give off bromide, chloride, and fluoride ions and lead to: kidney, liver, and reproductive organ harm

34
Q

What is the slowest inhalation anesthetic to be metabolized?

A

Methoxyflurane

35
Q

What do you do to facilitate an endotracheal intubation before a surgery?

A

Give a short acting neuromuscular blocker

36
Q

What are the halogenated hydrocarbon inhalation anesthetics?

A 
Halothane
Isoflurane
Methoxyflurane 
Sevoflurane 
Desflurane
37
Q

When are The CV effects of inhalation halogenated hydrocarbon anesthetics most seen?

A

In the presence of adrenergic agonists

38
Q

What are advantages and disadvantages to isoflurane?

A 
Advantages: potent, induction < 10min, NO catecholamine sensitization, less heptic and renal toxicity than halothane (lower rate of metabolism)
Disadvantages:
Rarely arrhythmias
Bad Oder
Malignant hyperthermia
39
Q

What are advantages and disadvantages to nitrous oxide?

A

Ad: low blood solubility, low CV, second gas effect, mild to moderate analgesic effect

Dis: MAC 104, no muscle relaxing, diffusion hypoxia is rapidly discontinued

40
Q

What are the two barbiturates used most commonly for anesthetics?

A

Thiopental and Pentobarbital

41
Q

What is characteristic of Barbiturates as used for anesthetics?

A

Rapid onset and short action

Toxic, dose is between 50-75% of LD50

42
Q

How do the mechanisms of barbiturates and benzodiazepines differ?

A

Both facilitate GABA induced Cl entry into neurons (CNS depression)

Barbs - up the duration the channel is open
Benzos - up frequency of channel opening

43
Q

What is the main benzodiazepine used for anesthetics?

A

Midazolam

44
Q

What is characteristic for benzodiazepines as used for anesthetics?

A

Less CV and respiratory depression than barb

Most important is amnestic action (forget)

Insufficient for anesthesia alone (induction agent)

45
Q

What is Propofol?

A
  • 50sec induction and 4-8min recovery
  • May be given alone to maintain anesthesia of balanced
  • Anti-emetic action
  • May result in injection site pain
  • Respiratory effect –> apnea
  • how MJ died
46
Q

What is ketamine?

A
  • PCP close
  • Dissociative anesthetic
  • Anesthetic, analgesic, amnestic, sedative
  • Airway relflexes and respiration maintained
  • NMDA receptor antagonist
  • rapid onset
  • bad delirium and hallucinations
  • abuse
47
Q

What are the two main opioids used as anesthetics?

A

Fentanyl

Sufentanyl

Neuro Block 5 (20 decks)

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