Nitrous Oxide (Liu and Desai) Flashcards
What is a colorless gas with a faint, sweetish odor that does not break down in the body, but is excreted unchanged by the lungs?
Nitrous oxide
Can nitrous oxide be a general anesthetic on its own?
No
What is the primary site of action for nitrous oxide?
Cerebral cortex
What percentage nitrous oxide will cause slight cardiac depression?
Less than 80 percent
What is “concentration effect”?
The greater the concentration of gas, the more rapid the induction
What is “second gas effect”?
When a less potent gas is added in high concentration to a more potent gas in a low concentration, the potent gas will have a more rapid uptake
What is a side effect of nitrous oxide if not given 100% oxygen post-procedure 3-5 minutes?
Nitrous diffuses rapidly out of blood and into alveoli causing diffusion hypoxia
What is the primary complaint in a majority of dental patients?
Fear of pain
What is the diminution or partial elimination of pain in the conscious patient?
Analgesia
What is the term for the minimally depressed level of consciousness, produced by a pharmacological method, that retains the patient’s ability to independently and continuously maintain an airway and respond normally to tactile simulation and verbal command?
Minimal sedation
Though cognitive function and coordination can be impaired during minimal sedation, what must be unaffected?
Ventilator and cardiovascular functions
Nitrous oxide can be used with only 1 enteral drug for minimal sedation only if that drug is prescribed how?
No more than maximum recommended dose of drug for unmonitored home use
When could nitrous oxide be used to produce minimal, moderate, deep sedation or general anesthesia?
When it is used in combination with other sedation agents
What is the term for drug-induced depression of consciousness during which patients cannot be easily aroused but respond purposefully following repeated or painful stimulations, and their ability to maintain ventilatory function may be impaired?
Deep sedation
What is the term for the drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation?
General anesthesia
What are 3 types of tanks?
E cylinder
G tank = 5300 L
H tank 6000L
Green tanks have what gas?
Oxygen
Blue tanks have what gas?
Nitrous oxide
Why can you not go above 70% nitrous with a nitrous unit?
21% oxygen in room air and system is not closed
What is a sign that you are getting second hand nitrous?
Fingers start tingling
What is the first safety mechanism to ensure that you don’t hook up the hoses wrong between oxygen and nitrous?
Diamter index safety system (DISS)
What is a second safety mechanism to ensure that you don’t hook up the hoses wrong between oxygen and nitrous?
Pin index safety system (PISS)
NItrous connector pins are offset while oxygen connector has centered pins
What is the most important level to check before a procedure with respect to gases?
Oxygen levels. Do not begin if below 500psi
Will the nitrous tank gauge indicate anything until it is empty? Why or why not?
No. It will only be full or empty. Nitrous is primarily liquid in the tank.
The main knob on the nitrous machine sets the flow/concentration of which gas: oxygen or nitrous?
Oxygen
Counterclockwise will increase flow
What is a normal pulse oximeter reading?
94-99%
What is the average liter flow of oxygen for nitrous cases?
5-6L/min
Should the patient be immediately started on nitrous when the nasal hood is placed?
No. Start on 100% O2.
What is the initial dosage of nitrous and titration?
Start at 30% and increase by 10% at 2 min
What is the goal of a nitrous case?
A relaxed, cooperative patient who can respond to simple commands
What should you tell the patient to expect with the onset of nitrous?
LIght-headedness, numb or tingling fingers, spinning room, feeling like they are sinking into their chair, sounds are more distant
Prior to releasing the patient after nitrous, what must be done?
100% oxygen 3-5 minutes
Room air 5 minutes
Post op vitals
Modified Romberg Test (e.g. field sobriety test)
What are 3 planes of stage 1 anesthesia?
Plane 1 - no analgesia
Plane 2 - partial analgesia
Plane 3 - partial amnesia, analgesia
What are the characteristics of stage 2 anesthesia and why?
Excitement and delirium because the inhibitory CNS is inhibited first
What anesthesia stage is surgery performed in?
Stage 3
A patient with a hard angry stare, sweating, disoriented, or uncooperative are all signs of what with nitrous oxide?
Nitrous overdose
What are 5 expected effects from nitrous oxide?
- Diminish anxiety and normal fears
- Analgesia
- Dulling unpleasant stimuli
- Decreased gagging
- Partial amnesia
An overdose of nitrous resulting in nausea, amnesia, snoring, and clenching mouth shut, correspond to what Guedel Stage of anesthesia?
Guedel Stage II
A flushed face, decreased muscle tone, lightheadedness, tingling, warmth, euphoria of Nitrous Sedation/analgesia correspond to what Guedel stage of anesthesia?
Guedel Stage I
What nitrous concentration corresponds to the Guedel Stage I?
10-30%
What occular sign do you see at a nitrous concentration of 55% and higher?
Divergent eyes (Nystagmus) and dilated pupils
The national institute of occupation safety and health (NIOSH) defines Chronic exposure as what? (Dr Desai said to know this)
Exceeds 50 ppm of nitrous as an 8 hr weighted average
Acceptable nitrous exposure by NIOSH standards? (Dr Desai said to know this)
Less than 25 ppm in ambient air
What are the risks of chronic nitrous exposure?
- Spontaneous abortion
- Reduced fertility
- Birth defects
- Liver, kidney and general neurologic disease
What is the greatest source of contamination for the dental staff and why?
Patient exhaling from mouth because nitrous is exhaled unchanged
What are some absolute contraindications to nitrous use?
- Acute upper respiratory infection or nasal obstruction
- Active infective bronchitis
- First trimester pregnancy
- Myasthenia gravis
- Muscular dystrophy
Why are pneumothorax, bowel obstructions, and inner ear infections absolute contraindications for nitrous?
Have air pockets where nitrous can sequester
What are some relative contraindications for nitrous use?
- Second and third trimester
- Psychiatric instability
- Acute asthma
- Severe COPD
- Recent eye surgery (risk of expanding bubble in eye)
Never administer nitrous without what?
An assistant present due to medico-legal
Does a patient have to be NPO or require an escort to drive home after a procedure involving nitrous?
No
