4. Nitrous I

Question 1

What are the conducting airways

Answer 1

larynx, trachea, bronchi, bronchioles

Question 2

What are the respiratory airways

Answer 2

respiratory bronchioles
alveolar ducts
alveoli

Question 3

Blood supply to lungs

Answer 3

• To the alveolar= bronchial circulation

- Participating in gas exchange= pulmonary arteries

Question 4

Muscles that partake in inspiration and expiration

Answer 4

Inspiration- diaphragm and intercostals (accessory mm= SCM, scalenes and abdominal mm.)

Exhalation= passive elastic recoil

Question 5

Autonomic and Voluntary control centers of the brain for respiration

Answer 5

• Autonomic- medullary reticular formation in pons

- Voluntary= cerebral cortex

Question 6

Central and peropheral chemoreceptors that stimulate breathing

Answer 6

Central= H+ conc. and Partial pressure CO2
Peripheral= Carotid and aortic bodies (Partial pressure O2)

Question 7

Me chanoreceptors that modulate the rate and depth of respiraiton

Answer 7

• J receptors
• In lung periphery
• Simulate ventilation in response to pulmonary vascular engorgement

Question 8

Rate of gas diffusion is directly proportional to

Answer 8

the partial pressure created by the gas

Question 9

How does gas exchange between alveoli and capillaries occur

Answer 9

simple diffusion down a partial pressure gradient (rate of gas exchange primarily depends on the difference in partial pressures)

Question 10

Factors that increase the alveolar partial pressure (tension)

Answer 10

• Increased delivery (increase ventilation)

- Decreased removal (decreased solubility or CO)

Question 11

Gasses with (high/low) solubility have a faster rate of equilibrization

Answer 11

low

Question 12

The lower the solubility of a gas the (faster/slower) the onset and the (faster/slower) the recovery

Answer 12

faster… faster

Question 13

Solubility of a gas in blood is expressed how

Answer 13

• Blood: gas or tissue: blood coefficient

- Oil:gas partition coefficient

Question 14

Define MAC

Answer 14

Minimal alveoalr concentration- concentration of anesthetic needed to produce immobility in 50% pateints

Question 15

What is the MAC of Nitrous

Answer 15

105

Question 16

Nitrous has a (high/low) blood: gas partition coefficient

Answer 16

low (lowest of all the gases

Question 17

General anesthesia is defined how

Answer 17

drug-induced state by absence of perception to all sensations

Question 18

MAC is a measure of the drugs (what property?)

Answer 18

potency

Question 19

Factors that lead to a decrease in MAC

Answer 19

• Hypoxia
• Increased hypercarbia (increased CO2)
• Anemia (less O2 carrying ability)
• Old age
• Hypotension
• Hypothermia
• CNS depressants
• LAs
• Pregnancy

Question 20

Factors that increase the MAC s

Answer 20

• Hyperthermia
• Infants and adolescents
• Microsomal inducing agent (chronic EtOH and Drug use)

Question 21

What is the most commonly used inhalation anesthetic in dentistry

Answer 21

nitrous oxide

Question 22

Four properties of N2O that can be beneficial or harmful

Answer 22

• Expands the colume of gas filled spaces- not beneficial
• Concentration effect- beneficial
• Second gas effect- beneficial
• Diffusion hypoxia- not beneficial

Question 23

Describe why N2O has the tendency to fill gas spaces

Answer 23

-N2O is more soluble in blood than N2 –> spaces fill more rapidly than the gas can diffuse out

Question 24

Areas where gas accumulation can lead to issues

Answer 24

• Middle ear
• Eye (post- retinal surgery)
• Pneumothorax
• GI in case of bowel obstruction
• Air emboli enlargement
• Emphysema blebs

Question 25

Describe diffusion hypoxia

Answer 25

Rapid outflow of N2O from the alveoli --> dilution of O2 (hypoxic conditions)

Question 26

Describe the concentration effect of n2O

Answer 26

the higher the conc. of anesthetic gas the greater the uptake and augmentation of inspired volume of that gase

Question 27

Describe the second gas effect

Answer 27

The use of one gas potentiates the sedative effects of a second gas

Question 28

N2O gas is mainly eliminated how? Minorly eliminated how?

Answer 28

Majorly= through lungs unchanged | -Minorly via gut flora ( pseudomonas dentrificans --< free radical formaiton)

Question 29

MOA of N2O causing analgesia

Answer 29

Direct interaction with opiod receptors and indirect increase in bodies endogenous opioids

Question 30

MOA of N2O in producing anxiolysis

Answer 30

-Bind GABA A receptors at the benzo site

Question 31

Chronic exposure to N2O can lead to

Answer 31

MS like symptoms (Irreversible inhibition of the cobalt atom on VitB12). Reduces the activity of VitB12 enzymes (methionine and thymidylate synthetase) vital in the synthesis of myelin and nucleic acids

Question 32

N2O exposure leads to (sympathetic/parasynpathetic) stimulation

Answer 32

sympathetic (offsets the myocardia depressive effects)

Question 33

Main side effect of N2O .

Answer 33

nausea (depression of the reflexes and GE sphincter muscles)

Question 34

Effect of N2O on airway resistance

Answer 34

increased airway resistance and decreased mucociliary activity (issue for asthmatics)

Question 35

What percent N2O is needed for Amnesia, Anxiolysis and analgesia

Answer 35

``` Amnesia= 70% (not recommended) Anxiolysis= 20-30% Analgesia= 10-40% ```

Question 36

Absolute contraindications of nitrous

Answer 36

- Pregnant - Bowel obstruction - Cranial injury with pneumocephalus - Neurosurgical procedure (craniotomy) - Open chest surgery - Pneumothorax - Bullous emphysema - Ocular surgery (recent) - Recent tympanic surgery - Air embolus

Question 37

Acute toxicity of N2O

Answer 37

bone marrow suppression

Question 38

Chronic toxicity of N2O

Answer 38

- Inhibition of the cobalt atom of VitB12 (neurologic changes- ataxia and paresthesia) - Mutagenicity (changes in DNA) - Carcinogenicity (increased cervical cancer) - Teratogenic (spontaneous abortions)