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Anesthesiology > What is anesthesia > Flashcards

What is anesthesia Flashcards

1
Q

Ether historically:

A
  • First publicly used in 1846 by William TG Morton

* Standard of care until 1960s

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2
Q

Chloroform historically:

A

Effective, but reports of arrhythmias, resp. depression, and hepatotoxicity

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3
Q

Nitrous oxide historically:

A

Still used today, but low potency; “second gas effect”  N2O use can decrease amount of anesthetic needed

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4
Q

Flourinated hydrocarbons historically:

A

Halothane (1956)
Isoflurane (1981)
Desflurane (1992)
Sevoflurane (1994)

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5
Q

Father of Anesthesia

A

John Snow - british . Anesthesiology came into being mid-1900s.

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6
Q

Cocaine historically

A

Cocaine from coca plants used topically (for eye surgery) in 1884
Later that year, cocaine was injected intradermally for local nerve blocks
1898: first spinal (cocaine)

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7
Q

IV Induction agents historically

A

• Barbs used first in 1920s (barbital > hexobarbital > thiopental >methohexital)
• Benzos: used for induction, but also pre-medication, supplementation of anesthesia, and IV sedation
• Ketamine (1970)
o Minimal cardiac and respiratory depression
• Etomidate (1972)
• Propofol (1989)

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8
Q

Meyer-Overton Rule

A

the potency of inhalation agents directly correlates with their lipid solubility

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9
Q

Anesthesia is 4 things:

A
  1. Analgesia
  2. Amnesia
  3. Reversible loss of consciousness
  4. +/- Muscle relaxation
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10
Q

FGF =?

A

Fresh Gas Flow - determined by vaporizer and flowmeter settings

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11
Q

Inspired gas determined by?

A

Fi - determined by: FGF rate+circuit volume+ circuit absorption.

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12
Q

Alveolar gas determined by?

A

FA - determined by uptake+ventilation+concentration effect+ 2nd gas effect. FA/Fi

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13
Q

Arterial gas determined by?

A

Fa - determined by V/Q mismatching

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14
Q

High solubility?

A

High solubility (ex: halothane) so quickly taken up by blood so takes longer for FA to rise so slower induction

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15
Q

Low solubility?

A

Insoluble (ex: nitrous oxide) so slowly taken up by the blood so FA rises quicker so faster induction

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16
Q

Partition coefficients of 5 volatile agents, starting at most insoluble (i.e fastest)

A

Partition coefficients:

Desflurane (0.42)

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17
Q

How does high CO affect induction speed?

A

High CO –> higher uptake of anesthetic –> takes longer for FA to rise –> slower induction

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18
Q

How does low CO affect induction speed?

A

Low CO can cause overdose of soluble agents because fast induction

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19
Q

Factors determining transfer of anesthetic gas from machine to alveoli

A
  • Inspired partial pressure

* Alveolar ventilation

20
Q

Factors determining transfer of inhaled anesthetic from alveoli to arterial blood

A
  • Blood-gas partial coefficient
  • Cardiac output
  • Alveolar-to-venous partial pressure difference
21
Q

Factors determining transfer of inhaled anesthetic from arterial blood to brain

A
  • Brain-blood partition coefficient
  • Cerebral blood flow
  • Arterial-to-venous partial pressure difference
22
Q

Factors that that speed recovery from anesthetic (also speed up induction):

A
  • Elimination of rebreathing
  • High FGF
  • Low circuit volume
  • Low circuit absorption
  • Decreased solubility
  • High cerebral blood flow
  • Increased ventilation
23
Q

MAC =?

A

MAC = the alveolar concentration that prevents movement in 50% of patients in response to a surgical incision

24
Q

3 facts about MAC

A

o MAC mirrors brain partial pressure
o MAC allows comparisons of potency between agents
o MAC values for different anesthetic agents are roughly additive
0.5 MAC Nitrous oxide (53%) + 0.5 MAC Halothane (0.37%) = 1.0 MAC Isoflurane

25
Q

Nitrous Oxide: MAC, potency, smell…?

A 
MAC ~105% -> cant ever get 1 MAC. Low potency.
The only inorganic gas used.
Gas at room temp. (liquid with pressure)
Nonflammable
Colorless/odorless
Low solubility -> rapid onset 
Eliminated via exhalation, irreversibly oxidizes vit B12 (Inhibits enzymes that need B12)
BM suppression with prolonged exposure
Teratogen
26
Q

Isoflurane: MAC, potency, smell…?

A

MAC 1.2%, second most potent. Pungent. Vasodilator: lower BP, increase CBF and ICP.
Nonflammable. Metabolized to trifluroacetic acid. Isomer of enflurane.

27
Q

Sevoflurane: MAC, potency, smell…?

A

MAC 1.8%, about half as potent as Iso. Sweet smell. Bronchodilator.
Metabolized by P450
Potential for nephrotoxicity because of increased fluoride ions

28
Q

Desflurane: MAC, potency, smell…?

A

MAC ~6.6%, low potency, very pungent. Increases sympathetics: HTN if rapid.
Boils at room temp because high vapor pressure, so requires special vaporizor.
Low solubility so fastest in/out.
Degraded by desiccated carbon dioxide to carbon monoxide so check ABG for carbohemoglobin.

29
Q

Variables Decreasing MAC

A
  1. Hypo or Hyper thermia
  2. Elderly
  3. Acute EtOH
  4. Anemia
  5. Hypoxia/Hypercarbia
  6. Hypotension
  7. Hypercalcemia
  8. Hyponatremia
  9. Pregnancy
30
Q

Variables Increasing MAC

A
  1. young age
  2. chronic EtOH
  3. Hypernatremia
  4. acute amphetamines
  5. Cocaine
  6. Ephedrine
31
Q

Halothane MAC, potency…?

A

MAC 0.75, most potent.
Liquid at room temp.
Nonflammable
Alkane derivative
Oxidized by P450 in liver - trifluoroacetic acid.
Rare halothane hepatitis (in middle age obese women)

32
Q

Stages of anesthesia

A

Stage 1. Analgesia: pt loses pain sensation but remains conscious
Stage 2. Excitement: pt may experience delirium, become violent.
BP: increased and irregular
RR: increased
Stage 3. Surgical Anesthesia: point at which surgery can begin.
 Relaxed skeletal muscles
 Regular breathing
 Eye movements slow then stop
Stage 4. Medullary Paralysis: occurs if primordial brainstem functions stop working

33
Q

How can Stage 2 of anesthesia be bipassed?

A

STAGE 2’s effects can be bypassed by giving a barbiturate!

34
Q

When should stage 4 of anesthesia be reached?

A

NEVER - it can cause death!

35
Q

What do inhaled anesthetics do to BP and SVR?

A

decrease BP (nothing for NO)

36
Q

What do inhaled anesthetics do to CO?

A

Decrease, or nothing for NO, Iso, sometimes Des.

37
Q

What do inhaled anesthetics do to HR?

A

Halothane - decrease.
Isoflurane - increase.
Desflurane - increase or nothing.
Else- nothing

38
Q

What do inhaled anesthetics do to RR, PaCO2, and TV?

A

Increase RR and PaCO2.

Decrease TV.

39
Q

What do inhaled anesthetics do to CBF, ICP, and seizure threshold.

A

Increase CBF and ICP.

Decrease seizure threshold.

40
Q

What do inhaled anesthetics do to metabolic rate?

A

Decrease metabolic rate.

Except NO which increases metabolic rate.

41
Q

What do inhaled anesthetics do to renal blood flow, GFR, UOP?

A

Decrease all

42
Q

What do inhaled anesthetics do to hepatic blood flow?

A

decrease

43
Q

3 factors that affect anesthetic uptake?

A
  1. blood solubility (less solubility means faster induction)
  2. alveolar blood flow
  3. diff in partial pressure b/w alveolar gas and venous blood
44
Q

Which inhaled anesthetic can cause BM depression?

A

NO

45
Q

Which states predispose patients to overdosage with soluble agents?

A

Low output states. Rise in alveolar concentration is increased.

46
Q

Greater uptake of an agent means…?

A

The greater the uptake of agent: the greater the diff between inspired and alveolar concentartions and slower rate of induction

47
Q

Which inhaled anesthetic has the least effect on BP?

A

NO. but sevo also has small decrease in BP.

Anesthesiology (9 decks)

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