Pharmacological Behavior Guidance Pt. 1: LA and Nitrous Oxide

Question 1

Geudels Stages of Anesthesia (4) *know

Answer 1

* Know 
Stage 1 - ANALGESIA 
- Pt relaxed, follows instructions 
- Some pain reduction 
- Four planes (from analgesia to hallucinations and loss of consciousness)

• avoid deeper planes w/ lower concentration Nitrous oxide

Stage 2 - EXCITEMENT/ DELERIUM (violent)

• Deepened CNS depression
• Excitement/Delirium/ Violent/ Jerky movements
• Laryngospasm may occur

Stage 3 - SURGICAL ANESTHESIA

• UNCONCIOUS
• No Laryngeal and pharyngeal reflexes
• Major surgeries
• Four planes

Stage 4 - MEDULLARY PARALYSIS

• Medullary paralysis: Respiratory centers of the medulla oblongata of the brain that control breathing and other vital functions stop.
• DEATH

Question 2

What is the concentration effect? *know

Answer 2

• Know
  Concentration effect: the higher conc. of nitrous oxide, the FASTER the alveolar conc. approaches inspired conc. (Give more gas on pedal, get there quicker)

HIGHER CONC. INCREASES ALVEOLAR CONC.
SIMPLY = HIGHER CONC. GAS GIVEN, THE FASTER ALVEOLAR CONC OF THE GAS APPROACHES INSPIRED CONC.

50% Nitrous will approach 50% alveolar conc. faster
than 30% nitrous

Question 3

What is the second gas effect? * know

Answer 3

Other conc. of gases given with high conc. nitrous RUSH INWARDS to REPLACE NITROUS OXIDE that is absorbed by pulmonary blood.

SIMPLY: OXYGEN delivery is enhanced!

remember nitrous: minor depression in cardiac output + slight increase in peripheral resistance = little change in BP

Question 4

MAC of Nitrous?

Answer 4

104% (incapable of full anesthesia by itself)

Low blood solubility (rapid induction rapid awakening )

Question 5

T/F Is there CVS effects with the use of nitrous?

Answer 5

TRUE - mild cardiovascular depressant

Minor depression in CO and slight increase in PR (peripheral resistance) = little change in BP

Question 6

What % oxygen and % nitrogen is the air we breath?

Answer 6

78% NitroGEN
21% OXYGEN 
v. little 02
- Machines cannot administer under 20% O2 (that's under RA) 
RA oxygen = 21

Question 7

Nitrous Mechanism of action (2 receptors)

Answer 7

STIMULATES GABA (feel good R, reduces anxiety)
INHIBITS NMDA ( excitatory glutamate receptor) 
Promotes release endogenous opioid NT (endorphins/dynorphins) 

GABA = reduces fear and anxiety that’s why Benzodiazepines stimulate Gaba! (makes sense)

Question 8

Name 2 Adverse effects of nitrous?

Answer 8

1) Increases volume of any closed air pocket in the body! that’s why you can’t do it with acute otitis media!
2) Nausea and vomiting (.5%-1.2% pts)

Question 9

4 reasons nitrous causes nausea and vomiting

Answer 9

1) Longer duration
2) Fluctuation in conc.
3) Lack of titration
4) Increased conc.

Question 10

Indications for nitrous (6) QE

Answer 10

1) Fearful/ Anxious
2) Long tx
3) Painful
4) Simple restorations, can’t tolerate LA
5) Gag reflex
6) Difficulty getting LA

Question 11

Objective Nitrous (Reference manual) (8)

Answer 11

1) Reduce anxiety
2) Reduce untoward movement and rxn to dental tx
3) Enhance communication and cooperation
4) Raise pain reaction threshold
5) Increase tolerance for longer tx
6) Aid in tx of mentally/physically disabled or medicaly compromised pt
7) reduce gagging
8) Potentiate effects of sedatives

Question 12

Recommendations: Indications (Reference Manual) Nitrous oxide

Answer 12

1) Fearful/Anxious/ Obstreperous pt
2) SHCN
3) Gag reflex interferes w/ tx
4) Profound LA cannot be obtained
5) COOPERATIVE child LENGTHY dental tx

Question 13

Contraindications Nitrous (Reference Manual) ! (8)

Answer 13

1) some COPD
2) Current URT infection
3) Recurrent MIDDLE EAR infection (increases volume of closed spaces!)
4) SEVERE EMOTIONAL DISTURBANCES or DRUG RELATED DEPENDENCIES
5) 1st trimester!
6) Tx Bleomycin sulfate! (cancer drug)
7) Methylenetetrahydrofolate reductase deficiency AKA MTHFR Deficiency (a lot of autistic children have this!) MTHFR enzyme plays an important role in processing amino acids, specifically, the conversion of homocysteine to methionine
8) Cobalamin (B12) deficiency (this deficiency is in vegetarians!)

Question 14

Indications for med consult with nitrous! (6)

Answer 14

1) Severe COPD (chronic hypercarbia)
2) CHF
3) Sickle cell disease (need to maintain ox saturation)
4) Recent tympanic membrane graft
5) Acute otitis media (increased pressure in closed spaces)
6) Acute severe head injury (intracranial pressure! increased pressure in closed spaces)

Question 15

Can you use nitrous with sickle cell disease?

Answer 15

Yes! Just need med consult!

Question 16

Methylenetetrahydrofolate reductase deficiency MTHFR deficiency - AR or AD?

Answer 16

AR
Common in AUTISM
MTHFR - responsible FOLATE metabolism + homocysteine regulation
Nitrous oxide INHIBITS homocysteine conversion to methionine –> accumulation of unconverted homocysteine in kids

Question 17

PSI Nitrous tank

Answer 17

750 PSI ( will always be at 750 PSI until empty)

Question 18

PSI oxygen

Answer 18

2000 PSI (Pounds per square inch)

Question 19

Safety features of nitrous machine (2)

Answer 19

1) FAIL SAFE mechanism - Automatic shut off if 02 level under 25% (remember machines won’t work if 02 below 25% b/c RA gives 21%)
2) Pin- index yoke system to prevent crossover of cylinders

Question 20

Diffusion Hypoxia

Answer 20

N20 given is stopped, large quantities of N20 diffuse from blood into alveoli and dilute O2.

Question 21

Ways to prevent Diffusion Hypoxia (3)

Answer 21

1) 100% O2 after N20
2) Important to scavenge EXPIRED nitrous and reduce nitrous pollution
3) Raise chair and allow pt to recalibrate

Question 22

Test Q: Emergency O2 - Positive pressure O2 delivery system: what is the L/min flow recommended for bag-valve mask to deliver positive pressure O2?

Answer 22

15 L/Min recommended when using bag valve mask to delivery PP02

Question 23

Test Q: Emergency O2 Positive pressure O2 delivery system: Capable of administering ___ %O2 for at least ___ min (650 L “E” cylinder)

Answer 23

Capable of administering > 90 %O2 for at least 60 min (650 L “E” cylinder)