Introduction Flashcards by Iona Davies

What are the indications for IV sedation?

Dental anxiety/phobia
Need for prolonged or traumatic dental procedures
Medical conditions potentially aggravated by stress (angina/ sickle cell)
Medical/behavioural conditions affecting pt’s ability to cooperate (parkinsons)
Special care requirements (learning disavility/autism/dementia/mental health ect)
Gag reflex

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What drug is used in IV sedation?

Midazolam

Benzodiazepines, also known as “benzos”, are a class of depressant drugs used to treat anxiety, insomnia, and seizures- depress CNS

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What are the contraindications of IVS?

Allergy !!
Other concerns which can complicate tx
No escort
Pregnancy and breast feeding
Psychiatric disorders
Respiratory disease
Hepatic disease
Renal disease
Needle phobia (cannulation)
Obstructive sleep apnoea (OSA) or other airway concerns

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Why is respiratory disease a contraindication for IVS?

IVS causes respiratory depression, if respiratory disease already exists it can push them to respiratory stress

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Why is hepatic/renal disease a contraindication for IVS?

Midazolam is metabolised in the liver and excreted in the kidney
If these organs are not working properly then it can affect sedation

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What can be done to enable a needle phobic pt to undergo tx, prior to cannulation for IVS?

Give these patients premeds
Oral/ intra-nasal midazolam

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How does OSA work

Relaxation of the soft tissues of the upper airway/ pharynx causing airway narrowing/closure, can lead to respiratory depression

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What medications are involved in IH sedation

Nitrous oxide and oxygen

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What are the indications for IH sedation

Children
Mild/moderate anxiety
Long cases (no sedation window)
Needle phobia
Where other sedation is contraindicated (liver/kidney)
Medical conditions
Gag reflex

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What are the contraindications for IH sedation

Acute/chronic nasal obstructions
1st trimester of pregnancy, esp ideally not they should not be preggas at all
Inability to cooperate or understand
Where equipment interferes with operating site
Chronic obstructive pulmonary disease/any respiratory disease
Nasal or facial deformity- have to ensure good seal of mask
Movement disorders- effects good seal of mask
Psychological disease
Nasal hood phobia
Recent eye surgery

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Give an example of an acute and a chronic nasal obstruction

Acute: flu/ blocked nose
Chronic: nasal polyp

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Why is recent eye surgery contra-indicated in IH sedation?

Eye surgery can create a pocket of gas within soft tissues in the eye, if nitrous oxide gets in this pocket it will expand, and damage the tissue
Rare but important

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In spirometry what is the tidal volume

Average air breathed in during aspiration

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In spirometry what is the minute volume

Tidal volume x amount of breaths per min

(amount of litres breathed in & out per min)
This is on the flow meter on inhalation machine

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What is the average minute volume?

5 (-6) L

This is where we start on inhalation machine, and adjusted up and down according to pt

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Where does our respiratory drive come from?

This is the strength of the signal from the respiratory centres that controls breathing

Main factors
Higher centres (conscious control of breathing)
Central chemoreceptors (amount of CO2 in blood and change breathing accordingly)
Drugs (eg midazolam lowers respiratory drive)

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How is oxygen carried around the blood?

In red blood cells
Contains hemoglobin which carry oxygen
Each hemoglobin can contain 4 oxygen molecules

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How many oxygen molecules will a fully saturated haemoglobin molecule carry?

4 molecules

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What does the oxygen saturation machine actually measure?

The saturation of haemoglobin in the blood

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What does the x axis mean in this oxygen desaturation curve

Partial pressure of oxygen
Ensures enough pressure of oxygen in blood vessels to push oxygen into brain and tissues around body where needed

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What does it mean if you have a low partial pressure of O2?

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Hypoxia/hypoxemia

Why is the % O2 saturation measured instead of pO2?

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It is easier to measure

Due to the nature of the oxygen desaturation curve, what does a small drop in % O2 sat under 90% mean

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Even a small drop will cause a large decrease in pO2

What should the % O2 sat be prior to starting dental tx?

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At least over 90%

What is the reversal agent for midazolam?

Flumazenil

What is the distribution half-life time of midazolam?

6-15 mins Warn pts will take a few mins to feel effects, not imediate

What is the elimination half-life time of midazolam?

1-3 hours 8-24 hours to be completely removed from system Important for recovery, why an escort is required, working/driving not allowed for 24 hours

what does distribution time mean?

Time taken for the drug to get from the blood vessels into tissues

what does elimination time mean?

Time taken for the drug to be removed the body through metabolism and excretion

What does midazolam metabolize into?

Relatively inactive metabolites, which also have short half-lives

What is midazolam's therapeutic index like?

Relatively high, so has a wide margin of safety This is a comparison of the amount of a therapeutic agent that causes toxicity to the amount that causes the therapeutic effect.

What effects does midazolam have?

Anxiolysis Sedation Muscle of relaxation Anterograde amnesia- useful for dental phobics

How do both midazolam and flumazenil work?

Benzodiazepines will have effects on the benzodiazepine (BZD) receptor The BZD receptor will act on the GABA receptor When GABA is activated it causes Cl- to flood in and cause inhibition of the cell Benzodiazepines potentiate (enable) the inhibitory effects of GABA (inhibit neural actions in brain where there is BZD receptors)

Why may there be a variation in effects of midazolam/ flumazenil when regarding the patients age

There are age related distributional changes, such as: Reduced number of receptors and slower circulation Paradoxical effects (Means v young/old pt may have different effects compared to middle age people; young ppl: more alert, old ppl more sedated)

Why may there be a variation in effects of midazolam/ flumazenil when regarding if the patient misuse CNS active drugs

These pts are often difficult to sedate, this may be due to altered activity at the receptor level

Flumazenil reverses all effects of midazolam except...

Retrograde amnesia

Compare half lives of flumazenil to midazolam

Flumazenil has a shorter half life than midazolam so theoretically will wear off become midazolam (but mainly re-sedation will not occur)

Name some properties of nitrous oxide

Colourless & odorless, non irritant Low blood solubility Ease of titration Rapid recovery

What is the mechanism of action of nitrous oxide?

Unknown Diffuses into blood (conc in tissues of high blood flow)

What is the titration regime in IV midazolam, for fit and healthy adults?

2mg injected over 30 secs Pause 60-90 secs Further increments of 1mg every 30 seconds until sedation is adequate

What is the mean dose of IV midazolam?

2-7.5mg

What effects does nitrous oxide have?

Anxiolysis Analgesia (not clinically significant) Nil effects on kidney or liver Bone marrow suppression (chronic use)

What is the titration regime in IV midazolam, for pts with a high BMI?

2mg over 30 secs Pause for 60-90 secs Further increments of 0.5mg every 30 seconds, paying close attention to noisy breath sounds and corresponding drops in O2 saturation

What is the titration regime in IV midazolam, for the elderly?

1mg over 30 secs Pause for 120-240 secs Further increments of 0.5mg every 30 secs until adequately sedated

What is the titration regime for inhaled NO2?

Flow rate 5-6L/min Start of with 100% O2 Two increments of 10% NO2 and then as many increments of 5% NO2 with 60 sec intervals between each increment Can titrate down, unlike IV

What is the mean dose of inhaled NO2?

25-55% NO2

What is sedation related desaturation?

O2 sats drop below 90-95% (depending on usual sats)

What do you do in sedation related desaturation?

Stop titrating if possible Check sats probe is on finger correctly Jaw thrust Nasal cannula and 2-4L/min O2 Flumazenil +/- guedel airway Crash team

State the flumazenil titrations when reversing sedation What is the usual dose?

Recommended initial dose is 0.2mg administered over 15 secs A further dose of 0.1mg can be injected and repeated at 60 second intervals, up to a max of 1mg Usual dose: 0.3-0.6mg

State the flumazenil titrations when there is a suspected overdose/oversedation What is the max dose?

Recommended initial dose: 0.3mg administered IV over 30 secs Followed by a series of 0.3mg injections, each administered over a 30 second period, at 60 sec intervals Max dose: 2.0mg

Introduction Flashcards

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