Inhalantion Anesthetics

Question 1

Temperature Changes

Answer 1

Hypothermia D/t less blood flow, causes slower induction but enlargement of tissue capacity which weigh each other out. Go to sleep slower and wake up slower because everything is slowed down

Hyperthermia usually causes increased anesthetic requirement and CO which leads to slower induction

Question 2

CMRO2

Answer 2

Dose dependent decrease in cerebral metabolic rate of O2 consumption

Question 3

Cerebral blood flow

Answer 3

Dose dependent increase in cerebral blood flow (increased vasodilation of cerebral arteries)

Question 4

Increase Gas flow rates

Answer 4

Faster the anesthetic will reach the patient and faster patient will fall asleep

Question 5

MAC

Answer 5

Minimum alveolar concentration required to achieve surgical Anesthesia

More soluble, higher the number
Less soluble=lower number=fast on/off

Require lowest dose: 
Halothane: 0.75
Iso: 1.15
Sevo: 2
Des: 5.8
Nitrous: 105

Question 6

Blood/Gas Partition Coefficient

Answer 6

Speed of induction and emergence

Lower the number=less soluble=faster on/off

I.e. for every 0.6 molecules of second that stay in the blood, 1 molecule is released into brain tissue

Faster induction/emergence:
Des: 0.42
Nitrous: 0.47 (ends up being faster than des because of high concentrations used)
Sevo: 0.6
Iso: 1.4
Halo: 2.3

Question 7

Oil/gas partition coefficient

Answer 7

Tells you the potency (higher lipid solubility)

Higher the number the more potent the anesthetic

I.e. 50 molecules of secondary will knock pt out for every one that doesn’t

More potent:
Halo: 224
Iso: 99
Sevo: 50
Des: 18.7
Nitrous: 1.4

Question 8

Reduce MAC (need lower dose)

Answer 8

Increased age
Hypothermia
Sedatives
Other anesthetic
A2 agonist
Opioids
Pregnancy
Anemia
Hypotension
Hypoxia
Hyponatremia
Lithium

Question 9

Increase MAC (need higher dose)

Answer 9

Young age
Hyperthermia
Hyperthyroid
Hypernat.
CNS stimulant drugs
Chronic alcohol abuse
Red-headed females

Question 10

Solubility effect

Answer 10

Low=fast on/fast off
High: slow in/slow out

Not as soluble in blood so it does not get redistributed as fast

Question 11

Second Gas Effect

Answer 11

When you give two anesthetic at the same time one has to be very insoluble/fast

I.e. administer nitrous with other—> nitrous draws other gas in faster than it would normally go

More rapid rise in Fa(alveolar fraction)/Fi (inhalation fraction)

Question 12

Nitrous Oxide Effects

Answer 12

Expands closed gas spaces (nitrous enters faster than nitrogen can exit)

Monitor in: pneuma bowel obstruction, inner ear surgery, neuro procedure, air embolism, ocular surgery, laparoscopy, middle ear grafts (increase inner ear pressure)

Question 13

Tissue Equilibration

Answer 13

Vessel rich—>muscle—>fat—>vessel poor

Question 14

Increased CO

Answer 14

Slows the onset of all anesthetic with the highest BG agents most affected

Draws anesthetic out of lungs faster so lung concentration decreases (lung concentration=brain concentration)

Question 15

Increased speed of induction

Answer 15

Low solubility
Low CO
High fresh gas flow
High minute ventilation
High concentration
Second gas effect

Question 16

Decreased Speed of Induction

Answer 16

High solubility
High CO
Low fresh gas flow
Low minute ventilation
Hypothermia
V/Q deficit

Question 17

Obesity

Answer 17

Does not affect induction but causes slower emergence d/t the anesthetic accumulating in fat (reservoir/depot effect)

Question 18

Effect of Nitrous on emergence

Answer 18

Take mask off face, nitrous rushes out of lungs pulling oxygen with it. Once nitrous goes away, O2 goes back up.

Prevent this from happening by giving 100% O2 at the end of a case (turn of anesthetic, O2 for 5 minutes)

Question 19

Children and Induction Speed

Answer 19

Kids go to sleep faster because they breath faster

Question 20

Anesthetic Effect on CNS/ANS

Answer 20

Dose dependent depression

Question 21

Anesthetic Effect on IOP

Answer 21

Decreased (except for succ and ketamine)

Question 22

Anesthetic Effect on ICP

Answer 22

CPP=MAP-ICP

Put person to sleep, cerebral vessels relax, increased CBF/volume/ICP

Neuroprotective effects

Question 23

Anesthetic Effect on CV

Answer 23

CNS depression
Direct cardiac depression (decreased BP—> decreased RBF—>decreased GFR)
Decreased SVR
Baro-receptor depression
Hormonal changes (decreased renin/vasopressin release)

Nitrous does not do these (not strong enough)

Does many of the same things as ischemic preconditioning—> when the heart suffers an insult, several molecular changes occur in area of ischemia such as blood flow, electrolyte, FR to protect the heart from further damage

Question 24

Cause tachycardia on induction

Answer 24

Des and lesser Iso
Most likely d/t respiratory irritation
More common in young healthy pets

(All anesthetic cause dose dependent tachycardia)

Question 25

Anesthetic Effect on Respiratory System

Answer 25

Bronchodilation
Dose dependent respiratory depression
Depress TV before RR
Depress hypoxemia pulm vasoconstriction (when there is V/Q mismatch)

EXCEPT NITROUS

Question 26

Malignant Hyperthermia

Answer 26

Triggered by all inhalation anesthetic except nitrous

Question 27

Nitrous and immune function

Answer 27

Nitrous inhibits Vit B12 and methionine synthetase which blocks DNA and RNA production

Irreversible

*note: nitrous contraindicated in pregnancy

Question 28

Emergence Delirium

Answer 28

After the use of Sevo and Des in younger children causes restless behavior and child usually requires sedative

Question 29

Sevo and CO2 absorbants

Answer 29

Produce compound A and can cause renal issues

Question 30

SE of Volatile Anesthetics

Answer 30

Development neurotoxicity (<3)
Supraspinal analgesia
Vasodilation
Bronchodilation
Skeletal muscle relaxation
Malignant hyperthermia
decreased CMRO2
LOC
Postop N/V
Respiratory depression
Myocardial depression
Cardiac dysrhythmias
Anesthetic precondition
Depressed cellular immunity
Hepatic toxicity (halothane)

Question 31

Nitrous SE

Answer 31

Developmental neurotoxin
Supraspinal analgesia
NO vasodilation
Decreased RR increased TV
Decreased CMRO2
LOC
NO myocardial depression