4/10Exam 3 N. Inhaled (7) Flashcards by Linsay AugustinCRNA

Site of action of inhaled anesthetics

multiple sites of action and protein targets probably exist;

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When does loss of consciousness ensue?

Once a critical concentration of drug has entered the brain and spinal cord

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VA with a chloride ion

Isoflurane

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What are The primary factors that influence absorption of the inhalation anesthetics? (VUCSA)

Ventilation,
Uptake into the blood
Cardiac output,
Solubility of the anesthetic drug in the blood, and Alveolar-to-venous blood partial pressure difference.

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The concentration or partial pressure of anesthetic in the lungs is assumed to be

the same as in the brain, because the drugs are highly lipid soluble and diffusible, and they quickly and easily reach equilibrium among the highly perfused body compartments.

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Dose of an individual drug is expressed in terms of the

minimum alveolar concentration (MAC)

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MAC is the

Minimum alveolar concentration needed to produce anesthesia (lack of movement) upon surgical stimulation

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The faster the lung (and therefore brain) concentration rises, the_______Anesthesia is achieved

the faster

anesthesia is achieved.

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The faster the lung (brain) concentration falls after discontinuation of the drug, _________the patient emerges

the more quickly the patient emerges

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What do you do when preparing for a patient who is susceptible to malignant hyperthermia to avoid exposure resulting from residual trace amounts of gases *(TRI) ?

Thorough flush of the anesthesia machine with 100% oxygen at 10 L/min for at least 20minutes
Replacement of breathing circuits and the carbon dioxide canister, and draining, Inactivation or removal of vaporizers are
advised

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MAC of Sevoflurane

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Blood/Gas partition Coefficient of Sevo

0.6

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MAC of Isoflurane

1.15

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MAC of Nitrous oxide

105

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Blood/Gas partition Coefficient of N2O

0.47

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Desflurane MAC

5.8

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Blood/Gas partition Coefficient of N2O

0.42

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Is an indicator of the speed of uptake and elimination

The blood/gas solubility coefficient of an anesthetic

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Concentration effect

The higher the concentration of anesthetic delivered, the faster anesthesia is achieved; this is also referred to as over-pressuring; as with any drug, the larger the initial dose administered, the faster the onset of action

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Oil/gas Solubility coefficient

The blood/gas solubility coefficient is the indicator of an anesthetic’s speed of onset and emergence:
the higher the coefficient, the slower the anesthetic; conversely, the lower the coefficient, the faster
the anesthetic

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Second-gas effect

The second-gas effect is a phenomenon in which two anesthetics of varying onset speeds are administered
together: a high concentration of a fast anesthetic such as nitrous oxide is administered with a slower second anesthetic gas; the slower gas achieves anesthetic levels more quickly than if it had been given alone

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Diffusion Hypoxia

Diffusion hypoxia occurs when high concentrations of nitrous oxide are administered; at the end of the procedure, when nitrous oxide is discontinued, it leaves the body very rapidly, causing a transient
dilution of the oxygen and carbon dioxide in the lungs; hypocarbia and hypoxia may occur;

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How to prevent diffusion hypoxia?

administration of 100% oxygen for approximately 3-5 min when nitrous oxide is discontinued alleviates this problem

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Allow for an increase in deposition of anesthetics into fat and may prolong
recovery

Long procedures and morbid obesity

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The MAC or required dose of Anesthetics is

higher in infants and children and decreases with increasing age.

Infants MAC vs adult

Infants aged 6 months have a MAC 1.5 to 1.8 times higher than a 40-year-old adult.59

Diffusion of Nitrous Oxide into Closed Spaces

Nitrous oxide diffuses into air-containing cavities in the body during an anesthetic procedure.

These air-containing spaces are normally rich in nitrogen, which is_________Soluble than nitrous oxide.

34 times less soluble than nitrous | oxide.

NItrous oxide , If the space is expandable

it increases in volume.

Examples of expandable air cavities, include

``` Air embolism Pneumothorax Acute intestinal obtruction Intraocular air bubles Pneumoperitoneum ```

Avoid nitrous during these procedures

tympanomastoid procedures | and intracranial air during diagnostic or surgical intracranial procedures.

Cuff and nitrous

endotracheal tube cuff, laryngeal mask airway, and balloon-tipped pulmonary artery catheters may expand during nitrous oxide anesthesia, and appropriate precautions and adjustments should be considered

The uptake of anesthetic drugs is faster in which population?

children than in adults. In other words, a child goes to sleep faster than an adult patient

Child goes to sleep faster than an adult, whY?

Child has higher alveolar ventilation per weight accounts for this effect.

The higher the cardiac output

the slower the onset.

Less soluble anesthetic work

faster

In general, the longer an anesthetic is administered,

the slower the patient emerges.

The least soluble | Exhibits the fastest clinical recovery, Least to fast order

desfluranewith sevoflurane and isoflurane following in that order.

Intraocular hexafluoride gas and N2O

2-18 mmHg increase in pressure in 20 minutes

Middle ear pressure and N2O

Increased 1-7 mmHg in 1 hour

Pneumothorax and Nitrous

2-3 times the volume in 5-20 | minutes

Intestinal gas and N2O

Double in 150 minutes

Air Bubble and N2O

Immediate increases in size occur

Least metabolize

nitrous

Least metabolize before nitrous

Desflurane Less than 0.1

Minimum alveolar concentration—BAR definition

block adrenergic responses (MAC-BAR)The alveolar concentration of anesthetic that blunts the autonomic response to noxious stimuli; approximately

MAC Bar level

1.6-2.0 MAC

The MAC suppressing appropriate response to commands in

50% of patients; memory is usually lost at MAC-awake; approximately 0.3-0.5 MAC

The MAC suppressing appropriate response to commands in

50% of patients; memory is usually lost at MAC-awake;

MAC awake level is

approximately 0.3-0.5 MAC

Are the least metabolized and do not result in metabolism-related toxicity.

Nitrous oxide, desflurane, and isoflurane

First, the majority of the blood leaving the lungs with anesthetic is normally distributed to the vital organs

Vessel rich group

The longer the anesthetic is given , the

Greater the saturation of all the body compartments.

During induction, increases in cardiac output effect on onset?

slow onset.

Hyperthermia and MAC

Increase

Drug induces increases in CNS and MAC

Increase

Hypernatremia and MAC

Increases

Chronic Alcohol abuse and MAC

Increase

Hypothermia and Increasing age and MAC

Decrease

Hyponatremia and MAC

Decrease

Hypoxia and MAC

Decrease MAC

Lidocaine and MAC

Decrease MAC

Lithium and MAC

decrease MAC

Cardiopulmonary bypass and MAC

Decrease

Hypotension and MAC

Decrease

Right to left shunt on induction of anesthesia

shunted blood mixed with blood coming from ventilated alveoli which results in reduction of alveolar partial pressure of the anesthetic. SLOW INDUCTION of anesthesia

Left to right shunt on induction of anesthesia

Left to right shunting causes the anesthetic partial pressure in mixed venous blood to increase more rapidly than it would in the absence of the shunts.

Cardiopulmonary bypass , it is necessary to administer a relative

Higher concentration of the volatile agent compared to that with normal lung inhalation.

The uptake of volatile agents administered by the oxygenator is dependent on 3 factors

Blood/gas solubility tissue/gas solubility Oxygenator intake

Blood gas solubility and temperature

Increases as temperature falls

Tissue/gas solubility and temperature

Increases as temperature falls.

Emergence Phase I : Resp

Transition from apnea to regular breathing

Emergence Phase II: Characteristics

``` Tearing, salivation Increase HR and BP Grimacing Response to Autonomic responsiveness Extubation possible Swallowing ```

Extubation possible in

Phase II and Phase III

Emergence Phase III characteristics: REEA

Eye opening Response to oral commons Awake patterns on EEG Extubation possible.

General Anesthesia

Arousal not possible, unresponsive, eyes closed, reactive pupils

What is the Meyer-Overton rule

The more lipid soluble the anesthetic, the higher the potency.

What favors the genesis of cardiac dysrhythmias?

Increasing the number of halogen atoms.

2 Key players in the mechanism of anesthesia

Neurotransmitter gated-ion channels | 2 pore K+ channels

The lipid solubility is

Directly proportional to potency

Gender on MAC

No effect

Metabolic alkalosis on MAC

No effect

VA causes immune suppresion

Nitrous oxide

Triggers for malignant Hyperthermia

Iso, des, sevo

Support combustion: VA

Nitrous

Gas likely to evaporate when left in an open container in the OR?

Desflurane

VP of desflurane

669 mmHg

VP of enflurane

172 mmHg

VP of Halothane

243 mmHg

VP of isoflurane

238 mmHg

VP of sevo

157 mmHg

Boiling point of Desflurane

22.8

Boiling point of Isoflurane

48.5

Boiling point of Sevoflurane

58.5

Which of the following physical properties best correlates with VA potency?

Lipid solubility

Nitrous can also inhibit this receptor

NDMA ; they are excitatory receptors, and their inhibition leads to decrease neuronal activity/

What is the boiling point of a liquid?

It is the temperature at which VP equals atmospheric pressure.

What VP and boiling point favors evaporation of the liquid phase into a vapor phase?

HIgh VP and low boiling point.

VA effects on the neuro physiology and metabolism

Increase CBF, decrease in CMRO2./

Nitrous on CMRO2

Increases CMRO2, CBF, and ICP

Gas most likely to produce seizure like activity on the EEG

Enflurane.

Causes a reflex increase in HR (gas favor)

Isoflurane

Nitrous oxide has a direct

negative inotropic effect despite this, it has the lest effect on the CV

NITROUS and SNS

Sympathetic stimulator, and increases level of catecholamines, present during nitrous anesthesia produces a slight compensatory increase in arterial BP and HR so that CO remains same.

Sevoflurane, Desflurane and isoflurane are all

Vasodilators and decrease the SVR.

Sensitize the myocardium

Halothane.

C1H2CIF5O.

Isoflurane

C3H2F6O

Desflurane

Desflurane and sevoflurane are halogenated exclusively with

fluorine

Halogenated exclusively with fluorine are

less soluble in blood.

Halogenated exclusively with fluorine are

less soluble in blood.

Which modern volatile agent differs from isoflurane only in the replacement of the chlorine with fluorine?

Desflurane differs from isoflurane only by the substitution of a fluorine atom for the chlorine atom. This one change increases the vapor pressure dramatically

Methyl ethyl ethers.

Enflurane, isoflurane, and desflurane

Fluorinated methyl isopropyl ether.

Sevoflurane

Is the only brominated modern volatile anesthetic agent

Halothane

4 contraindications to the use of N2O

Closed pneumothorax Tympanoplasty or middle ear surgery Pneumocephalus Venous Air embolism

May promote aplastic anemia

Nitrous oxide

N20 can cause a decrease in blood pressure and cardiac output when added to high dose of what intravenous anesthetics?

Opioids

Does ETC02 increase, decrease, or remain unchanged when N 10 is turned off? Why? What law applies?

ETC02 decreases. When N2O is discontinued, N20 rushes into the alveoli from the blood. The alveoli enlarge and gases that are present, including C02, are diluted. Fick's law of diffusion applies.

Does nitrous oxide administered alone increase cerebral blood flow and intracranial pressure?

Yes

``` Which inhaled agent is most associated with postoperative nausea and vomiting (PONY). Rank the inhaled agents, from greatest to least. with respect causing PONY. ```

Nitrous oxide has the greatest capacity to cause postoperative nausea and vomiting (PONY). From greatest to least, the likelihood of an inhaled agent • causing PONV is: nitrous oxide > desflurane;; isoflurane = sevoflurane.

Nitrous oxide is turned on and held at the same concentration for 6 hours. At 6 hours, is the uptake of nitrous oxide increasing, decreasing, or remaining unchanged?

Nitrous oxide equilibrates with all tissues within 6 hours, so uptake of nitrous oxide remains unchanged at this time; the amount of nitrous oxide inhaled essentially equals the amount of nitrous oxide exhaled

In general, how much does N20 reduce | the MAC of a volatile agent?

There is approximately a I% reduction in MAC for every 1% of nitrous oxide delivery.

Which two volatile anesthetics most decrease systemic vascular resistance (SVR)?

Isoflurane and desflurane.

By what mechanism does isoflurane cause hypothermia?

Depresses the temperature regulating centers of the hypothalamus, there is heat loss, because no shivering occurs.

How may an increase in ICP with isoflurane can be prevented?

Hyperventilate the patient during isoflurane administration

Which volatile agent is LEAST likely to produce potentially dangerous increases in intracranial pressure if modest hypocapnian is present?

lsoflurane.

These agents have similar effects on cerebral blood flow.

Iso, sevo, enflurane and desflurane

How do VA alter the ventilatory response to CO2? to hypoxia>

Dose dependent decrease in ventilatory response to CO2/

What MAC completely blocked at low concentration of volatile agent?

0.1 MAC

Have volatile inhalational agents been shown to inhibit hypoxic pulmonary vasoconstriction (HPV) in patients?

HPV is inhibited by a high concentration of a volatile agent, possibly at 1.0-1.5 MAC, or higher.

You are providing LMA anesthetic delivery during maintenance anesthesia and the patient begins to cough. What volatile agent has the highest incidence of causing the patient to cough?

Isojlurane has a slightly higher incidence of causing cough during anesthetic delivery through LMA

Several minutes after induction, during mechanical ventilation, the vaporizer is delivering 2% isoflurane but the gas analyzer is only reading end-tidal concentration at 0.5%. Why

the alveolar uptake of isoflurane is relatively slow because of its reasonably high blood solubility. This argument holds for enflurane and halothane as well. The greater the blood solubility of an inhalational agent, the slower the increase in partial pressure in the alveoli

Which volatile agents most depress ventilation? | Least depress ventilation?

Desflurane and enflurane most depress ventilation. Halothane least depresses ventilation

Which volatile agents most depress the baroreceptor reflex, and which least depress it?

Halothane and sevoflurane most depress the baroreceptor reflex(there are no increases in heart rate despite decreases in blood pressure with these agents).

Which volatile agents least depress the baroreceptor reflex,

Heart rate tends to increase reflexly with the decreases | in blood pressure produced by these agents

Which volatile agent is most degraded | by soda lime? Which is least degraded?

Sevoflurane is most degraded by soda lime and desflurane least.

What volatile inhalational agent least potentiates muscle relaxants?

All, but halothane does it the least.

What volatile agent produces the greatest | increase in cerebral blood flow

Halothane

What effect does acute alcohol intoxication | have on MAC

MAC is decreased in the patient who is acutely intoxicated

Which inhalational agent has no halogen

N2O

Clinically, what is the most important Fluoride ions. Inorganic fluoride ions cause nephrotoxicity? Why?

Fluoride ions. Inorganic fluoride ions cause nephrotoxicity

Are isoflurane, enflurane, sevoflurane and desflurane metabolized by oxidative or reductive processes

Oxidative.

The modern inhaled anesthetics are primarily excreted via the

lungs

The minimal amount of biotransformation ( 0.02% to 5%) of modern volatile anesthetics takes place in the liver by the

cytochrome P450 enzyme system

Desflurane how many atoms

6 fluorine atoms

Sevoflurane how many atoms

7 fluorine atoms

Vapor pressure is directly proportional to

Temperature