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Pharmacology I > Inhaled Agents II > Flashcards

Inhaled Agents II Flashcards

1
Q

What is (Fi)?

A

Gas moving into the lungs caused by ventilation.

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2
Q

What is “wash in”?

A

High flows of (O2, N2O/O2) in 5-10L, can precisely control partial pressure of anesthetic inspired.

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3
Q

Concentration Effect

A

> gas concentrations inspired, > inspired volumes, > minute ventilation.

> inspired volumes, > alveolar PP (PA) and > gradient gap.

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4
Q

What 2 factors effect the rate of uptake of the inspired anesthetic from the delivery system.

A

1: Inspired Concentration
2: Alveolar Ventilation

When alveolar vent. Is high, pp of anesthetic in the alveoli > rapidly.

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5
Q

2nd Gas Effect

A

When there are 2 anesthetic gasses present in the lungs.

When N20 is used, rapid crossing of N20 into blood pulls the second gas along with it. So, the arterial pressure of 2nd gas > more rapidly than it would if it were alone.

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6
Q

3 factors determine how fast anesthetics pass from the inspired gas to to the blood.

A

1 Solubility of the agent
2 Rate of BF through lungs
3 PP of the agents in the arterial/venous blood (Pa).

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7
Q

Solubility of Agent in Blood

A

Blood:Gas partition coefficient
Ratio of anesthetic concentration in the blood : to anesthetic concentration in a gas (alveolar) when two are in state of equilibrium.

Solubility of Agent in Blood = Pa/PA

(Anesthetic Blood Concentration) / (Anesthetic Alveolar Concentration)

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8
Q

Rate of Pulmonary Blood Flow (CO)

A

Rate of blood passing through pulmonary tissue influences how fast the anesthetic agent will be picked up from the alveoli.

> BF, > blood exposed to the agent, faster agent in picked up from alveoli and delivered to tissues.

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9
Q

PP of Arterial/Mixed Venous Blood

A

PP is low after circulation throughout the body when at the lungs after being delivered to tissues.

As venous PP rises there is less picked up less from the alveoli and uptake decreases.

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10
Q

Solubility of Gas in Tissues

A

Tissue: Blood coefficient

Most agents are equally solvable in lean tissue and blood, PP are very similar at equilibrium.

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11
Q

Tissue Blood Flow

A

The > blood flow to a particular tissue, the faster the anesthetic is delivered and the faster the PP and concentration will rise in that area.

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12
Q

4 Categories of Tissue Groups

A

1: Vessel Rich
2: Muscle and Skin
3: Fat
4: Vessel Poor

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13
Q

PP in Arterial Blood/Tissues

A

As tissues take up the agent, PP of agent > toward that of blood and uptake in alveolar (FA) anesthetic con. Toward inspired (Fi) con. is most rapid with the least solvable agents (N2O, Des, and Sevo)

Moderate soluble (Hal and ISO) have slower rate of FA to Fi ratio rise.

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14
Q

Stage I of Anesthesia

A

(Stage of Analgesia)

< Brain tension
< Dorsal horn activity
< synaptic transmission in Spinothalamic tract.

Begins with administration and ends with LOC.

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15
Q

Stage II of Anesthesia

A

(Stage of Delirium or Excitement)

> PP of brain (Pbr), blocks inhibitory neurons, > synaptic transmission.

> Muscle tone, irregular breathing, jaw clenching, involuntary activity, pupils dilate, >BP and HR. Likely to spasm. Don’t extubate.

Beginning from LOC to beginning of surgical anesthesia.

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16
Q

Stage III of Anesthesia

A

(Stage of Surgical Anesthesia)

> PP of Brain (Pbr) > depression of ascending (sensory) pathways of RAS = < spinal reflex or > muscle relaxation.

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17
Q

Stage IV of Anesthesia

A

(Stage of Depression)

> PP of brain (Pbr) < of vital medullary centers < profound respiratory and cardiac depression.

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18
Q

Reflexes Present

A 
Irregular respirations
Cough
Swallow
Gag
Surgical anesthesia not present
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19
Q

Loss of Reflexes

A

Rhythmic respirations

Surgical anesthesia present

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20
Q

Signs of “Light” anesthesia

A 
> Respiration’s
> BP + HR
> Muscle tone
Swallowing and coughing
Tear formation
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21
Q

Signs of “Deep” anesthesia

A

< BP + HR
Diaphragmatic breathing
Pupils dilate, lack luster

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22
Q

Where is MAC measured?

A

Alveoli

23
Q

MAC is a reliable indicator of …

A

Dose and Potency of an anesthetic

24
Q

< MAC = > or < Blood:Gas partition coefficient

A

> blood:gas partition coefficient

25
Q

Factors that < MAC

A 
Hypoxia (< 40 mmHg)
Anemia (Hct < 10%)
Hypotension (MAP <40)
Hypothermia
Pregnancy
> Age (< CMBRO2, 
> Ca
< Na

Drugs: (acute)
Lithium, narcotics, sedatives, CC blockers, Local anesthetic, Opiods, Kertamine, Barb/Benz, Vermpril, acute alcohol, Sympatholytics (methyldopa, reserpine, clonidine), Sympathomimetics (amephetamine)

26
Q

Factors that > MAC

A

< Age
Hyperthermia (if >42 C)
Female Red-Heads
> Na

Drugs: (chronic)
Cocaine, Ephedrine, Alcohol, Barbiturates, Narcotics

27
Q

What is the Standard Deviation of MAC?

A

~10%

28
Q

95% of pts should not move at ____ MAC

A

1.2 MAC

29
Q

99% of pts should not move at ____ MAC.

A

1.3 MAC

30
Q

MAC - Awake

A

The minimum alveolar con. at which 50% will respond to the command, “open you eyes”.

End Tidal (best indicator) 1/3 MAC is when pts wakes up.

31
Q

MAC - BAR

A

MAC necessary to Block Adrenergic Response to surgical incision (1.5 MAC).

32
Q

MAC - Intubation

A

Similar to MAC BAR.

Different stimuli require different end tidal con. of volatile anesthetic.

33
Q

MAC Values of Hal, Iso, Sevo, Des

A 
Hal: 0.77
Iso: 1.15-1.2
Sevo: 1.75-2.2
Des: 6.0-6.6
N2O: 104
34
Q

MAC values are _____ with other inhaled anesthetics.

A

Additive

50% Nitro + 50% Sevo = 1 MAC

(If at 4L of N20, 50% = 2L of N20)

(Slide #36 Listen and Understand)

35
Q

What is anesthetic depth based on?

A

Many variables:

VS, stage, knowledge, age, etc…

36
Q

____ is the absorption from alveoli into systemic circulation

A

Uptake

37
Q

____ is the cardiac output and blood flow.

A

Distribtuion

38
Q

_____ is done mostly by the lungs (unchanged) then metabolized by liver.

A

Elimination

39
Q

PA {} Pa {} Pbr Relationship & Primary Objective.

A

To achieve a constant and optimal brain PP (Pbr) of anesthetic.

Brain and all other tissues equilibrate with PP of inhaled anesthetic delivered to them by the arterial blood (Pa).

By controlling inspired PP (PI), a gradient is created from AGM to the brain.

PA: Alveolar
Pa: Arterial
Pbr: Brain

40
Q

Chart order
FA/Fi - x-axis
Time - y-axis

A 
N20 Fastest to climb (less soluble)
Des
Sevo
Iso
Halo Slowest to climb (more soluble)

Fi - inspired concentration
FA - alveolar?

41
Q

What is the Concentration Effect (PI)?

A

> difference in gradient PP > movement of anesthetic into blood. (Faster)

Necessary for accelerated uptake into blood = > rate of induction. Optimal.

42
Q

Does Hyperventilating > or < induction?

A

>

43
Q

How do you > rate of induction?

A

> concentrations (flows of gasses) and > ventilation.

44
Q

Is Low CO > or < rate of induction? Why?

A

> CO > uptake, rate of rise of PP in alveoli (PA) = SLOWS rate of induction.

Low CO speeds rate of induction, > PA alveoli PP bc there is less uptake into the bool to oppose input. > induction rate.

45
Q

Does a right to left shunt > or < induction?

A

Slows rate of induction. Gas bypasses lung.

Right to left < rate of induction.

46
Q

How long for equilibrium of tissue (brain)?

A

10-15 min

3 time constants.

Keep PA (Alveolar PP) gas high for this length.

47
Q

Alveolar - To - Venous PP differences.

A

PA-PV reflects tissue uptake of inhaled anesthetics.

Venous system (End tidal) tells us level of anesthetic saturation.

Venous = Arterial Blood saturations

3 time constants.

48
Q

Emergence of Anesthesia

A

Emergence in the inverse of induction.

To > rate of emergence, hyperventilate

Use High Gas flows to wash out system.

49
Q

What is Diffusion Hypoxia?

A

Occurs when N2O is stopped abruptly.

Alveoli fills with N20 instead of O2.

Must give N20 with O2

Hypoxic guard

Give 100% O2 for 5-10 mins post N2O administration.

50
Q

Factors that influence rate of Emergence.

A

Duration
Temperature of Pt
Physical Condition of Pt
Obesity. (Can fall back asleep) (Be careful)

51
Q

Can Inspiratory PP (Pi) be less than Zero?

A

No

52
Q

How does emergence differ from induction?

A

Absence of concentration effect during recovery. (Can’t be < than 0)

Tissue serve as a reservoir

Metabolism is very Low, most is expelled from body by the lungs.

53
Q

What Anesthetic Gasses take the longest to Wake Up?

A

Halo (most)

Iso (recovery greatly > after 1 hour of running anesthesia)

Sevo

Des (Least)

54
Q

Context Sensitive 1/2 time.

A

Elimination of inhaled anesthetics depends on length of administration (context).

Longer gas runs the longer it takes for the patient top wake up.

Then pt can swallow and have effective respiratory effort.

Pharmacology I (6 decks)

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