Trulearn

Question 1

Which volatile associated with decreasing seizure threshold?

Answer 1

Enflurane

Question 2

Volatile associated with megaloblastic anemia

Answer 2

Nitrous oxide inhibits the vitamin B12-dependent enzymes, methionine synthetase and thymidylate synthetase. This may lead to subclinical problems in relatively healthy patients, but may cause neurologic and hematologic sequelae in critically ill and vitamin B12-deficient patients

Question 3

V/Q mismatch affect on induction? And the effect depends on …. of the volatile

Answer 3

All V/Q mismatch has two effects: 1) increases the alveolar anesthetic partial pressure, 2) decreases the arterial anesthetic partial pressure. The degree of change that occurs is dependent on the solubility of the inhalational agent.

When perfusion is affected (reduced cardiac output, pulmonary embolism), the speed of induction of inhalational agents is increased. The impact is more significant with soluble agents such as isoflurane. The rise of FA/FI is steeper with lower perfusion of the lungs.

When ventilation is affected (intrapulmonary shunt), the speed of induction of inhalational agents is decreased. This occurs to a greater degree with insoluble agents (desflurane, sevoflurane). The rise of FA/FI is less steep.

Question 4

The solubility of an inhaled anesthetic is based on its ….

Answer 4

blood-gas coefficient and it is affected by temperature.

Question 5

The anesthetic effect of nitrous oxide are mediated via multiple receptors types or neurotransmitters including … and many other that still not fully understood.

But one receptor that not known to exhibit any effect on is …

Answer 5

Alpha adrenergic: analgesic via alpha 1 and symptomimietic effect via alpha 2

NMDA: analgesia and CNS depression

Dopamine: analgesic via release of endogenous opioids within CNS

NOT GABA receptors

Question 6

The only volatile decreases BP by directly affecting CO is …. where the rest through decreasing SVR.

Answer 6

Halothane

NO has no change or can increase ABP.

Question 7

Volatiles effect on CBF and CMRO2?

Answer 7

Term called “uncoupling” the decrease in CMRO2 while increasing CBF via a direct cerebral vasodilation effect.

Nitrous oxide is an exception, it causes both increase in CMRO2 and CBF

Question 8

Most volatile undergoes extensive metabolism?

Answer 8

Sevoflurane undergoes the most extensive metabolism (5-8%) followed by isoflurane (0.2%) then desflurane (< 0.2%).

Question 9

Reduced CO promotes … rate of inhalation induction. This phenomena is more pronounced in …. anesthetics

Answer 9

A faster rate, especially in more soluble anesthetics ( higher blood:gas partition coefficient >1)

Des (0.42) < NO (0.46) < Sevo (0.69) < Iso (1.46) < Halothane (2.54)

Question 10

A right to left intracardiac shunt slows the rate of …. induction but however it speeds the rate of … induction

Answer 10

Inhalational, but speeds IV induction anesthetics (because a portion of the drug bypasses the lung and quickly delivered to brain).

Question 11

How Volatile anesthetics potentiate neuromuscular blockade?

Answer 11

by DECREASING sensitivity of the postjunctional membrane to depolarization and INCREASING skeletal muscle blood flow which both augment neuromuscular blockade.

In addition, potentiation of neuromuscular blockade occurs by depression of upper motor neurons.

Question 12

Shunts and their affect on IV vs gas anesthetic

Answer 12

Intrapulmonary (Right To Left)

• Gas: Decreased Induction Speed
• IV; Minimal / No Effect

Intracardiac (Right To Left)

• Gas: Decreased Induction Speed
• IV: Increased Induction Speed

Intracardiac (Left To Right)

• Gas: Minimal / No Effect
• IV Minimal / No Effect

Question 13

Right to left shunt slows the speed of inhalational induction. This is more obvious in … soluble agents.

Answer 13

Less soluble

In the presence of an intrapulmonary shunt, the speed of induction will affect (most to least): Nitrous Oxide > Desflurane > Sevoflurane > Isoflurane > Halothane

Question 14

whats the product of desflurane and sevo degradation occurs with a desiccated carbon dioxide absorbent?

Answer 14

Carbon monoxide and heat are produced from the degradation of anesthetic agents in the presence of desiccated carbon dioxide absorbent in general. Among today’s volatile anesthetics, degradation of desflurane produces the most carbon monoxide, while sevoflurane produces the most heat.

There are rare cases of carbon monoxide poisoning and thermal injury to patients, usually associated with the first case on a Monday morning after the anesthetic machine has been left on all weekend with high gas flows, which dried out the absorbent

Question 15

The most volatile that risk to produce fluoride production is …? and its side effect is ..?

Answer 15

Normally the halogenated agents undergo oxidative metabolism in the liver with the cytochrome P450 system. Depending on the inhalational agent, varying amounts of fluoride are produced during metabolism, which can lead to nephrotoxicity; though with today’s newer agents, this is a theoretical risk.

The order of fluoride production for volatile anesthetics is methoxyflurane&raquo_space; sevoflurane > isoflurane > desflurane.

Question 16

Nitrous oxide should be avoided in situations where …

Answer 16

bowel distention could be particularly hazardous. Both the length of time administered and the concentration of nitrous oxide lead to increasing bowel distention.

There is a linear relationship with time administered to increase in bowel distension with up to a 200% increases in volume after 4 hours. A 50% concentration of nitrous oxide can double bowel gas (200% increase in bowel gas after 4 hours), a 75% concentration can quadruple the volume (400%), whereas an 80% mixture can lead to a fivefold increase (500%) after several hours of administration

Question 17

NO is it contraindicated in lap chole or appy?

Answer 17

Nitrous oxide is not contraindicated for short abdominal operations such as a laparoscopic cholecystectomy or appendectomy.

One study found that nitrous oxide had no clinically apparent deleterious effects during laparoscopic cholecystectomy. Another study found that nitrous oxide did not cause noticeable bowel distention during laparoscopic bariatric procedures of relatively short duration. The amount of time using nitrous oxide during abdominal surgery is more important than the type of surgery being performed.

Question 18

Why NO has faster rate of absorption than desflurande despite their similar blood gas partition coefficients?

Answer 18

The rate of rise of the FA/FI ratio is more rapid with nitrous oxide due to the concentration effect.

Question 19

Fluoride ion production by volatile from largest to smallest?

Answer 19

methoxyflurane > sevoflurane > enflurane > isoflurane > desflurane.

Methoxyflurane created the largest concentrations of inorganic fluoride ions and fluoride-induced nephrotoxicity.

Enflurane was related to renal concentration effects of fluoride ions causing nephrotoxicity.

Sevoflurane produces more fluoride ions than enflurane while being administered, but the concentration of fluoride rapidly declines with cessation of administration, owing to its low blood and tissue solubility.

Question 20

What are the nephrotoxicity levels of fluoride produced by volatile?

Answer 20

Nephrotoxicity occurs when fluoride levels are >50 µmol/L.

Moderate renal injury occurs between 50-80 µmol/L and severe injury occurs at >80 µmol/L.

Question 21

what is the factor that produce rapid increase HR induced by desflurane? is it the high MAC?

Answer 21

The increase in heart rate at 1.0 MAC is comparable to that seen with isoflurane use at 1.0 MAC, though rapid changes of desflurane over 1.0 MAC tend to cause a more dramatic increase in heart rate. This change in heart rate is thought to be reflexively mediated via baroreceptors in response to decreased blood pressure. It is the rapid change in desflurane concentration that leads to increased heart rate, not the absolutely MAC value. Again, at 1.0 MAC the heart rate change is similar between desflurane and isoflurane.

Question 22

HD changes seen with desflurane?

Answer 22

1) Increases heart rate (particularly when the concentration is quickly increased)
2) Decreases both mean arterial pressure and systemic vascular resistance (decreasing BP primarily by decreasing afterload)
3) while maintaining cardiac output (Desflurane causes a dose-dependent depression of myocardial function, but due a reflexive increase in heart rate, cardiac output is maintained.)

Question 23

Most potent volatile?

Answer 23

Chloroform and methoxyflurane are both more potent than halothane, Isoflurane is a potent volatile anesthetic, but not as potent as halothane (D).

Question 24

The most pungent of the volatile anesthetics is …

Answer 24

Desflurane

It may cause coughing, salivation, breath holding, and laryngospasm if administered via face mask or LMA.

Question 25

The order of non-depolarizing muscle relaxant potentiation by volatile is …

Answer 25

desflurane > sevoflurane > isoflurane > halothane > TIVA (e.g. propofol).

Question 26

Why NO has more rapid rise of FA/Fi than desflurane despite its lower blood:gas coefficient?

Answer 26

The concentration effect occurs when a high concentration of anesthetic can be used. Currently the only anesthetic in clinical use in which the concentration effect can be demonstrated is nitrous oxide. This effect explains why nitrous oxide has a more rapid onset than desflurane.

Question 27

What determines the anesthetic potency and minimum alveolar concentration (MAC)?

Answer 27

The oil:gas coefficient which measures the lipophilicity. The higher the oil:gas coefficient the lower the MAC. Isoflurane has an oil:gas coefficient of 99 and a MAC of about 1. Whereas desflurane has an oil:gas coefficient of 19 and a MAC of about 6.

Question 28

What determines the speed of inhalational induction?

Answer 28

The rate of rise of FA/FI which is related to the solubility or blood:gas coefficient of the anesthetic agent.

Solubility of commonly used anesthetics is: desflurane > nitrous oxide > sevoflurane > isoflurane from least soluble to most soluble.

Question 29

St. John’s Wort effects on common medications?

Answer 29

St. John’s Wort is an herbal antidepressant that induces the CYP enzymes and can alter drug responses with anti-rejection medications (increases risk of postransplant rejection), warfarin (increases risk of DVT, PE), and intraoperative anesthetics. It should be stopped at least 5 days prior to any surgical operation

Question 30

Shunts effects on induction;

• Intrapulmonary shunt
• Intracaediac shunt (Rt -> Lt)
• Intracardiac shunt (Lt -> Rt)

Answer 30

• Decreases only inhalation agents
• Decreases inhalational and increases IV agents
• No effect