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Pharmacology Test 3 > Pharmacology of inhaled anesthetics (Gatson) > Flashcards

Pharmacology of inhaled anesthetics (Gatson) Flashcards

1
Q

Pharmacokinetics

A

Uptake/Distribution

Elimination & Recovery

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2
Q

Pharmacodynamics

A

Effect of inhalants on the body

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3
Q

Physiochemical property affecting stability and potency

A

Chemical structure

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4
Q

Physiochemical property affecting amount of inhalant delivered to the patient

A

vapor pressure

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5
Q

physiochemical property affecting the kinetics within the body

A

Solubility

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6
Q

MAC

A

Minimum Alveolar Concentration

  • Determines dosing of an inhalant
  • Equivalent to ED50
  • Inversely related to potency
  • Can be altered by many factors
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7
Q

Uptake and Distribution

A

Delivery to sites of action => anesthesia

  • Movement along a partial pressure gradient
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8
Q

Gases move

A

Across a partial pressure gradient

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9
Q

Partial pressure…

1.

2.

3.

A
  1. Partial pressure in brain and not the concentration of anesthetic produces anesthesia
  2. Brain partial pressure equilibrates quickly with alveolar partial pressure
  3. Brain partial pressure always moves towards alveolar partial pressure
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10
Q

Partial pressure in alveoli

A

Balance between

  • Input to alveoli : delivery
  • Loss from alveoli: uptake

​Three factors influencing uptake

1. solubility of anesthetic

2. Patient’s cardiac output

3. Alveolar-venous anesthetic partial pressure difference

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11
Q

Inhalents removed from alveoli

A

by pulmonary blood: UPTAKE

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12
Q

Delivery depends on

A

Inspired anesthetic concentration

  • Vaporizer setting
  • Fresh gas flow
  • Volume of breathing circuit:
    • larger for a horse, slows delivery

Alveolar ventilation

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13
Q

Uptake and Distribution:

CO

A

INC CO = greater amount of blood carrying inhalant away from alveoli to tissue

DEC CO = less blood flow through lungs, less anesthetic removed

  • This patient will be induced much quicker
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14
Q

PA - PV

A

Venous blood returning to the lungs for re-oxygenation will retain some inhalant

PA - PV gradient must exist for uptake to occur

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15
Q

Elimination and Recovery

A

Decreasing the alveolar partial pressure

  • dec partial pressure in breathing circuit
  • Reverses gradient from blood to alveoli

Rate of elimination affected by

  • Inhalant solubility: low solubility recovers faster
  • Cardiac output
  • Duration of anesthesia
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16
Q

Elimination/recovery

Less soluble agents

A

Recover more quickly

17
Q

Less soluble agents

A

Sevoflurane

Desflurane

18
Q

If inhalant A is highly soluble in blood (high blood:gas partition coefficient) and inhalent B is not, this means that:

A

Inhalant B will cause a faster induction

19
Q

Which are Correct:

a. MAC is a measure of potency
b. MAC is a measure of speed of induction
c. MAC is additive among multiple inhalents

A

a. MAC is a measure of potency

b. MAC is additive among multiple inhalents

20
Q

MAC is additive

A

More inhalants you use, more MAC adds up

21
Q

MAC is JUST

A

Potency

22
Q

Fluorine is toxic to

A

Kidneys

23
Q

Toxic metabolites

A

Sevoflurane => Compound A

  • Kidney toxicity

Drugs causing production of carbon monoxide: change out Sodasorb every MONDAY

  • Isoflurane
  • Desflurane
  • Enflurane
24
Q

Pharmacodynamics

Desirable effects:

A

Reversible, dose dependent general anesthesia

Non-addictive

Decrease cerebral metabolic rate

Not dependent on hepatic and renal function

25
Q

Pharmacodynamics

CNS

A

Inhalants increase cerebral blood flow

  • Decreased ventilation => Inc CO2 => vasodilation
  • Decreased systemic vascular resistance => vasodilation of intracranial vessels
  • Related to inhalant dose
  • Detrimintal if ICP is elevated
26
Q

Cardiovascular and respiratory centers in ….

A

Medulla

27
Q

Inhalants increase intracranial pressure

A

Parallels increase in CBF

Space within calvarium is fixed

Pre-existing intracranial disease

  • cerebral damage
  • herniation of brain
28
Q

Pharmacodynamics:

Cardiovascular

A

All inhalants reduce cardiac output

  • negative inotropic effect
    • dec in stroke volume
  • decrease in peripheral vascular resistance
    • negative effect on B:
  • dose dependant
29
Q

Pharmacodynamics

Enhanced cardiovascular compromise

A

Mechanical ventilation

PaCO2 changes

Surgical stimulation

Lenth of inhalant administration

Concomitantly administered drugs

30
Q

Pharmacodynamics

Pulmonary System

A

Dose related decrease in ventilation

  • blunt the response to increased CO2
  • can act as a safety mechanism

Inc Pbrain => Dec ventilation => dec uptake => dec PBRAIN

*Monitor pulmonary function carefully of patient under anesthesia

  • Pulse Ox
  • Capnography
31
Q

Pulmonary system

Inc inhalant dose:

A

Depressed spontaneous ventilation

Depresses tidal volume followed by respiratory frequency

Inc arterial CO2

Medullary stimulation of respiration due to hypercapnia is reduced

Respiratory arrest occurs at 1.5-3 MAC

32
Q

Inc MAC = higher blood…

A

CO2

33
Q

Inhalant causing airway irritation

A

Desflurane

34
Q

Pharmacodynamics

Hepatic

A

Minimal hepatic metabolism

Prolongation of drug metabolism

  • Due to decreased CO leads to decreased hepatic blood flow
    • impact of hepatic metabolism of co-administered drugs
  • Isoflurane most likely to maintain hepatic blood flow
35
Q

Malignant Hyperthermia

A

White breed pigs

Greyhounds

Myopathy seondary to inhalant exposure

  • Muscle contracture => RYR1, Ca2+ channels
    • skeletal muscle oxidative metabolism
    • decreased oxygen supply and increased CO2
    • Circulatory collapse and death

Treatment

  • Discontinue inhalant administration
    • ​Also change rubber parts of circuit
  • Dantrolene sodium: muscle relaxant
    • acts on calcium channels to reverse this

Pharmacology Test 3 (12 decks)

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