Module B-2

Question 1

Induces the least cerebral vasodilation of inhaled anesthetics making it preferred agent for neurosurgical patients with elevated ICP

Answer 1

Sevoflurane

Question 2

Coronary steal

Answer 2

Blood flow distal to a fixed, atherosclerotic lesion would decrease when the surrounding, normal vasculature dilated in response to Isoflurane, triggering ischemia

Question 3

Inhalation consideration with pregnancy

Answer 3

Nitrous oxide is teratogenic

Volatile agents decrease smooth muscle tone-maintaining uterine tone is critical for postpartum hemostasis so volatile agents are minimized0 less than 0.5 MAC Sevoflurane and 1.0 Desflurane

Question 4

Relationship between CMRO2 and CBF and impact of inhaled anesthetics

Answer 4

Cerebral metabolic rate of oxygen consumption and cerebral blood flow are typically coupled, as one increases the other increases.

However, IAs induced a dose dependent cerebral vasodilation (increase CBF) and a decrease in the CMRO2- we call this an uncoupling

-nitrous increases CMRO2 and CBF

Question 5

Cerebral hypocapnia

Answer 5

Vasoconstrict

Question 6

Cerebral vasculature hypercarbia

Answer 6

Vasodilate

Question 7

Calcium and Inhaled anesthetics

Answer 7

Reduce intracellular free calcium in cardiac and vascular smooth muscle!!

End result is depression of contractile state of the myocardium and peripheral vasodilation

This is probably why giving calcium is cardio protective

Mechanism pg 88 Nagelhout

Question 8

Explain increase in HR with inhaled anesthetics

Answer 8

1. Trigger sympathetic response
2. Baroreceptor reflex
3. Antagonism of SA node automaticity

Question 9

Arrhythmias and Inhaled Anesthetics

Answer 9

All three can lead to Bradycardia(Sevoflurane) and prolonged QTc, which can lead to torsades which is a polymorphic ventricular tachycardia

Bonus: Likely due to interruption of cardiomyocyte repolarization via inhibition of K+ through hERG channels

Question 10

Cardiovascular effect of Nitrous oxide

Answer 10

Increase in SVR and HR but a decrease in CO

Question 11

IA impact on Respiratory system

Answer 11

Lower tidal volumes
Higher Respiratory Rate

not enough to prevent elevations in CO2 but surgical stimulation aids with this

Question 12

IA biotransformation rates:

Answer 12

Sevoflurane 5-8% —initially caused concern for
Everything else in trace amounts

Primarily hepatic etabolism via P450 oxidation

Question 13

Problems with Nitrous

Answer 13

Inactivation of B12 cofactor for methionine synthase which may inhibit DNA synthesis and have teratogenic & immunosuppressive effects

Watch for cobalamin deficiency!!

DO NOT USE IN PULM HTN

Question 14

Number of fluorine atoms on modern IA’s

Answer 14

Isoflurane- 5
Desflurane- 6
Sevoflurane- 7

Question 15

Impact of Halogenation

Answer 15

-Flammability-reduced
-Chemical Stability-enhanced
-Arrhythmogenic potential- increased
-Potency- increased
-Biotransformation

Question 16

Vapor Pressure, which has the highest?

Answer 16

Desflurane
The pressure were your liquid is in equilibrium with the surrounding gas in a given volume at an established pressure.
Molecules that want to evaporate with have a higher vapor pressure- due to low molecular weight/high kinetic energy/low intermolecular forces

Question 17

Modern “MOA” for Inhaled Anesthetics

Answer 17

Multiple and diverse targets that contribute to unconsciousness, amnesia, analgesia, and immobility,
-impact brain and spinal cord in a dose dependent manner

Question 18

Area of action and impact of IA’s in general

Answer 18

Immobility- spinal cord
Analgesia- spinothalamic tract
Unconsciousness- Cortex, thalamus, brainstem
Amnesia- Amygdala, hippocampus

Question 19

Common values for MAC-Awake and MAC-BAR

Answer 19

0.3
1.6

Question 20

What increases MAC??

Answer 20

High CNS Metabolic activity
Neurotransmission
Red hair lol

Question 21

What decreases MAC

Answer 21

CNS metabolic activity and neurotransmission
Concurrent administration of other drugs
Age

Question 22

Advantages/concerns of Nitrous

Answer 22

Rapid uptake/elimination
Odorless
Mild analgesic-NMDA

Air filled spaces
Toxic effects
PONV/environmental effects

Question 23

Why is NItrous a problem in air filled spaces

Answer 23

More soluble than N2- both attracted to gas phase and accumulate in cavities but N2O diffuses in faster than N2can be displaced out (34xfaster)

Question 24

N2O problematic air spaces:

Answer 24

Pneumothorax
Air emboli
Bowel
Pneumoperitoneum
Intraocular air bubbles
Equipment cuffs

Question 25

Why do we avoid IA’s while monitoring evoke potentials

Answer 25

They decrease amplitude and increase latency

Amplitude-strength of nerve response
Latency- speed of conduction

Question 26

Nitrous cardiovascular impact

Answer 26

Increase in SVR and HR due to SNS activation
-can be given with other agents to support MAP

Question 27

Preconditioning (cardiovascular)

Answer 27

Mimics myocardial injury which triggers cascade of intracellular events that ends up being cardio protective for future events

Question 28

Goal of HPV

Answer 28

Hypoxia pulmonary vasoconstriction diverts blood flow to areas of lung with greater ventilation in order to improve arterial oxygenation

-inhibited by volatile agents

Question 29

What do we avoid in Pulmonary hypertension?

Answer 29

Nitrous Oxide- it increases pulmonary vascular resistance

Question 30

Inhaled Anesthetics impact on Ventilation

Answer 30

Decrease Tidal Volume
Increase Respiratory rate
Impairs hypercarbia ventilatory response
Impairs hypoxic ventilatory drive

Question 31

What contributes to Formation of compound A??

Answer 31

Low flow of Sevoflurane (less than 2L)
Older/early generation CO2 absorbents
Desiccated CO2 Absorbents

Question 32

What is safe for Malignant Hyperthermia?

Answer 32

Nitrous Oxide and complete IV anesthetic

Minus Succ?

Question 33

Neuromuscular considerations

Answer 33

-Additive effect with muscle relaxants
-Dosages of muscle relaxants are decreased by 25-50%
-Prolonged recovered compared to TIVA (Total IV anesthetic)

Question 34

Why do we not run low flow sevo (<1-2L/min)

Answer 34

Compound A- nephrotoxicity