nitrous oxide pt. 1

who was known as the father of anesthesia?

horace wells

never go above ____% nitrous. never go below ____% oxygen

70 ; 30

what is michigan’s practice act state law?

direct supervision: the dentist must be present (ages 18+)

• we CANNOT administer more than 50% nitrous oxide

what is minimal sedation (anxiolysis)?

a drug-induced state during which patients respond normally to verbal commands

• accomplished when concentrations are less than 50%

what is moderate sedation / analgesia?

a drug-induced depression of consciousness during which patients respond purposefully to verbal commands (reflex withdrawal from a painful stimulus is NOT considered a purposeful response), either alone or accompanied by light tactile stimulation

• N2O concentrations are greater than 50% or when concentrations less than 50% are given concomitantly with another sedative

what is deep sedation / analgesia?

patients have to be aroused after repeated or painful stimulation

what is general anesthesia?

a drug-induced loss of consciousness during which patients are not arousable, even by painful stimulation

in ambulatory settings, N2O is used for _______ periods of time with _____ percentage concentrations

minimal ; lower

when the patient is mildly sedated, they can…

• reply to verbal commands

• cough and gag

nitrous oxide _________ the patient’s pain threshold

increases

The number of deaths associated with N2/O2 sedation in a dental office as the sole sedative agent and using appropriate equipment and technique is

A. none.

B. approximately 10.

C. approximately 100.

D. approximately 1000.

A. none

mixture of 20% N2O and 80% O2 has the analgesic equipotency of…

15 mg of morphine

T/F: level of pain control will vary due to individual biovariability

true

painful stimuli can be ___________ in an anxious patient

exaggerated

T/F: pediatric patients have shown positive behavior and lowered anxiety levels on sequential visits

TRUE

does N2O/O2 have a rapid onset of action?

yes

how long is the onset of action?

less than 30 seconds

• peak usually in less than 5 mins

what is titration and why is it important?

• the process of administering a drug incrementally to a specific level or endpoint of sedation

• it allows for the exact amount of the drug necessary to be delivered to every patient

is N2O metabolized in the liver?

no ; it is rapidly eliminated from the body after discontinuation of use

for complete elimination, the hygienist should…

use 100% oxygen for a minimum of 5 minutes after termination of the drug

does the patient need an escort following dismissal?

no

should nitrous be administered alone?

no

The rapid onset of action with N2O/O2 sedation is

advantageous. Effects are usually first seen within how

many minutes?

A. 5

B. 15

C. 30

D. 45

A. 5

define pharmacokinetics

the activity or fate of drugs in the body over a period of time, including the processes of absorption, distribution, localization in tissues, biotransformation, and excretion

define pharmacodynamics

the study of the biochemical and physiological effects of drugs and the mechanisms of their actions, including the correlation of actions and effects of drugs with their chemical structure, and the effects on the actions of a drug or drugs

which gas is sweet smelling, colorless, and becomes a liquid when compressed into a cylinder?

dinitrogen monoxide (N2O)

USDOT classifies N2O as a non-flammable, BUT…

it supports combustion

what should NOT be used on any N2O storage or distribution equipment?

no hydrocarbons (lubricants, grease or oil)

• do NOT store by flammables either

opening the tanks valves too quickly could cause a rapid pressure increase, raising the temperature which can cause…

a fire or explosion (think of opening a gas grill)

what kind of pressure gradient does nitrous move by?

from higher to lower

what is blood-gas coefficient?

how quickly the agent crosses the pulmonary membrane and enters the bloodstream

• nitrous easily crosses the alveolar membrane

why can nitrous oxide increase pressure in closed body spaces?

nitrous enters spaces 34x faster than nitrogen leaves, increasing pressure and volume

N2O is the _____ potent of all inhalation general anesthetics

least

what is drug potency determined by?

minimum alveolar concentration (MAC)

• MAC is the amount of drug necessary to prevent movement in 50% of subjects responding to surgical incision

what is MAC for N2O?

104% to 105%

what is the MAC for inhalation anesthetics halothane and isoflurane?

halothane: 0.75%

isoflurane: 1.2%

All are reasons why N2O is not used as a sole anesthetic agent for surgery in the operating room at a hospital except one. Which one is this exception?

A. Because it is the least potent (weakest) of all inhalation general anesthetics.

B. Because it has a MAC value of 104% to 105%.

C. Because profound surgical anesthesia is unattainable unless it is used under hyperbaric conditions.

D. Because it is much more expensive than halothane or sevoflurane, which are agents commonly used.

D. Because it is much more expensive than halothane or sevoflurane, which are agents commonly used.

Hydrocarbons such as oil, grease, or other lubricants should not be used near valves, gauges, regulators, or any fittings on N2O/O2 equipment because they may cause

A. leaking of the gas cylinder.

B. malfunctioning of the regulator.

C. a catastrophic explosion.

D. rusting inside the gauges.

C. a catastrophic explosion.

which two structures aid in respiratory function?

driven automatically by the brain stem (medulla oblongata) and voluntarily by the cerebral cortex

why are swollen tonsils or a deviated septum concerns for nitrous oxide sedation?

the patient must be able to breathe comfortably through the nose for nitrous oxide to work properly

if the larynx is irritated, what reflex is initiated?

cough reflex

what structure marks the bifurcation to the right and left bronchi, and initiates an even stronger cough reflex?

the carina

which bronchi is shorter?

right side

• more aspirations into right side

what are bronchioles?

continuous division of the bronchi but w/o cartilage

which generation begins the respiratory zone?

17

T/F: it is the 300 million alveoli that the exchange between air and blood takes place

TRUE

which 2 structures aid in active respiration, and how do they move?

diaphragm: moves downward

external intercostal muscles: move outward

what is minute ventilation?

the amount of gas brought into the lungs each minute

why do we begin nitrous administration with 6 L/min of oxygen?

to determine the patient's tidal volume (minute ventilation) before titration

atmospheric air is composed of…

~79% nitrogen, ~21% oxygen, and 0.04% carbon dioxoide

• combined, the gases produce a pressure of 760 mm Hg at sea level

where is N2O eliminated through?

99% is eliminated through the lungs

a healthy patient with no pulmonary or CVD, O2 saturation should be between what?

96% and 100%

oxygen below ___% is dangerous

90

what is diffusion hypoxia?

decreased oxygen saturation levels in the blood caused by the rapid exit of nitrous on its termination

what are some side effects of diffusion hypoxia?

• postoperative headache

• lethargy

• nausea

what should you do to prevent diffusion hypoxia?

administer 100% pure oxygen for the first 3 to 5 minutes

• continue oxygen until patient fully recovers

if choking occurs:

• abdominal thrusts, chest thrusts and/or back blows until the foreign object is expelled

• if patient becomes unconscious, call 911 and perform chest thrusts and attempt to ventilate the lungs

• head tilt-chin lift

• full face mask filled with oxygen can provide positive pressurized oxygen

• pulse oximeter must be on

what should you do if vomiting occurs?

roll the patient on their side and use suction to remove any vomitus

general guidelines pediatrics (can they eat before sedation, etc.?)

suggest a light meal with no fried or fatty foods be consumed at least 6 hours before sedation procedures and that no liquids be consumed within 2 hours of the procedure

• fasting is not required before minimal sedation

The term used to define the decrease in blood oxygen saturation caused by the rapid exit of nitrous oxide upon its discontinuation is called:

A. diffusion hypoxia

B. pulmonary effusion

C. arterial anoxia

D. aortic stenosis

A. diffusion hypoxia

The pulse oximeter uses light wavelengths to measure the amount of oxygen saturation of arterial blood. Which values would be considered normal for a healthy individual?

A. 68

B. 78

C. 88

D. 98

D. 98

where does air (gas) exchange occur in the body with the use of nitrous oxide?

alveoli

a COMMON area of spasm etalsdenced by significant cough and gag reflex occurs at the:

A. larynx

B. trachea

C. carina

D. nasopharynx

A. larynx
(carina is the last resort)

flushing around the patient’s face and neck indicates what?

vasodilation

currently, how many conditions involving the cardiovascular system should indicate medical consultation or postponement of N2O/O2 use?

zero

the sinuses are non-expansive which leads to an ________ in pressure when N2O is administered

increase

• may be uncomfortable for the patient

T/F: patient is NOT susceptible to hypoxia due to airway resistance, impaired function, or movement

FALSE ; they are susceptible

has there ever been an allergy reported to N2O?

no

what respiratory condition is positively influenced by nitrous oxide?

asthma

what respiratory disease is a contraindication to nitrous oxide?

COPD

how does nitrous oxide affect the central nervous system?

it depresses the CNS

chronic exposure to N2O can lead to…

numbness and weakness in the extremities

why is vitamin B12 deficiency a contraindication?

nitrous interferes with vitamin B12-dependent reactions (can potentially worsen it). avoid use or obtain medical consultation

during which trimester of pregnancy is nitrous contraindicated?

first trimester

what cancer therapy is a contraindication to nitrous oxide?

bleomycin sulfate therapy

is nitrous oxide a trigger for malignant hyperthermia?

no. it may be safely administered to MH-susceptible individuals

when is nitrous appropriate for patients with cognitive impairments?

only if the patient can understand the procedure and communicate discomfort

which patients should NOT receive nitrous because of mental status concerns?

patients with:

• psychological impairment

• current psychotropic drug use

• current/recovering addiction

• inability to understand or consent to treatment

what ear-related condition is a contraindication?

middle ear disturbance or surgery

what eye-related condition is a contraindication?

recent eye surgery involving perfluoropropane or sulfur hexafluoride gas

what are the major nitrous oxide contraindications?

• COPD

• B12 deficiency/pernicious anemia

• Bowel obstruction

• First trimester pregnancy

• Psychological impairment

• Current psychotropic drug use

• Current/recovering addiction

• Unable to understand/consent

• Middle ear surgery

• Recent eye surgery

• Pneumothorax

• Acute sinusitis/URI

• Cystic fibrosis (some cases)

• Abusers of N2O

which condition is NOT a contraindication to nitrous oxide?

hepatits C

Each are relative contraindications to the use of N2O/O2 sedation except one. Which one is the exception?

A. Patient with psychotic illness taking several medications

B. Patient who does not have the mental capacity to understand the procedure

C. Operator who cannot communicate with the patient because of a language barrier

D. Patient has undiagnosed anorexia with nutritional deficiencies

E. Patient is being treated for hepatitis C

E. Patient is being treated for hepatitis C

An indication for use of N2O/O2 sedation is a patient who

A. has a hypersensitive gag reflex.

B. has severe claustrophobia.

C. has current upper respiratory tract infection.

D. is in the first trimester of pregnancy.

E. is currently intoxicated or high.

A. has a hypersensitive gag reflex

what are the signs and symptoms of appropriate sedation?

• patient is comfortable and relaxed

• reduced fear and anxiety

• aware of surroundings

• responds to directions and conversation

• eyes become less active and glazed look appears

what physical sensations may occur during appropriate sedation?

• tingling in fingers, toes, or around mouth

• heaviness in arms/legs

• light feeling

• body warmth

• vasodilation in face and neck

• circumoral (around the mouth) numbness

how does facial expression change during appropriate sedation?

• expression becomes flat/relaxed

• no forehead tension

• patient may smile or giggle easily

during appropriate sedation, can the patient follow directions?

yes. the patient remains aware of surroundings and can maintain conversation and follow directions

what should you stress the patient refrain from?

talking

what should you ask a patient during nitrous sedation?

ask HOW they are feeling, not WHAT they are feeling

what should you do if a patient becomes uncomfortable?

immediately decrease the nitrous concentration

what are common signs of oversedation?

• floating or flying sensation

• detachment from surroundings

• dreamlike state

• hallucinations/fantasizing

• out-of-body experiences

• humming or vibrating sounds that progressively worsen

• uncontrolled laughter

what physical symptoms may occur with oversedation?

• drowsiness

• dizziness

• nausea

• light-headedness

• diaphoresis (sweating)

• feeling too warm/hot

• fixed eyes

what signs can oversedation progress to?

• sluggish, delayed responses

• slurred words or no verbal sense

• agitated or combative behavior

• vomiting

• unconsciousness

Each are signs of administering too much N2O except one. Which one is this exception?

A. Slow blink rate

B. Dizziness

C. Nausea

D. Slurred speech

E. Floating sensation

A. Slow blink rate

Monitoring a patient’s signs and symptoms throughout the entire sedation experience is vital to success. Which indicates an appropriate sequence of events leading to a relaxed and comfortable patient?

A. Awareness of surroundings to detachment of environment

B. Active eyes to slowed blink rate to inability to keep eyes open

C. Appropriate verbal response to conversation to slurred, inaudible speech

D. Slight tingling in extremities to vasodilation in face and neck

D. Slight tingling in extremities to vasodilation in face and neck