Conscious sedation (IVS, IHS, ORAL) Flashcards
1
Q
Define conscious sedation
A
Technique in which the use of drug produces a state of depression of the CNS but maintains protective reflexes and verbal contact throughout the period of sedation
2
Q
Why is loss of consciousness prevented in conscious sedation?
A
Drugs with a wide margin of safety are used to render loss of consciousness unlikely
3
Q
What are the main indications of CS
A
- Anxiety
- Reduction of potentially harmful physiological effects due to anxiety in those with existing medical conditions
- Unpleasant procedures
- Leaning disabilities
- Where GA should be avoided
4
Q
What should be assessed before you decide to use CS?
A
- Treatment required and what method of CS is suitable
- Degree of anxiety
- Patient expectations
- MH, SH and DH
- Written, informed consent
5
Q
What can the MH tell us about the patient regarding suitability for CS
A
- ASA grade
- Existing medical conditions
6
Q
Importance of SH for CS
A
- Ability to provide an escort
- If they have children
- Where they live/how they will get home from appt
- Occupation
- Alcohol and smoking
7
Q
What can DH tell us regarding suitability for CS
A
Previous sedation and dental treatment - success, recovery etc
8
Q
How does ASA grade reflect suitability for CS
A
ASA I and II - CS safe in practice
ASA III - CS in hospital setting only
ASA IV - GA with anaesthetist
9
Q
How is the airway assessed (for suitability for CS)
A
LEMON
- Look externally
- Evaluate 3:3:2 rule
- Mallampati score
- Obstruction
- Neck mobility
10
Q
Why does the airway need to be assessed before prescription of CS
A
- IVS causes depression of resp system
- Risk assessment for medical emergencies where the airway needs to remain patent
11
Q
What external features indicate poor airway
A
Obsese
High arched palate
Short neck
Facial or neck trauma
12
Q
What is the 3:3:2 rule in airway assessment
A
3cm (3 fingers) of mouth opening
3cm hyoid-mental distance indicates airway adjunct can be placed safely
2cm thyroid cartilage to to hyoid bone
13
Q
What Mallampati score indicates difficult airway
A
IV is associated with >10% change of difficult airway
14
Q
What are the Mallampati scores
A
Class 1 - full visibility of tonsils, soft vulva and SP
Class 2 - partial visiblity of T, SV and SP
Class 3 - soft and hard palate visible
Class 4 - only hard palate
15
Q
List ways anxiety can be measured in a patient
A
Self report questionnaires
Visual signs
Physiological signs
16
Q
What are visual signs of anxiety
A
Fidgeting, avoiding eye contact, talking too much/too little
Pale, sweaty or shaking
17
Q
What are physiological signs of anxiety
A
High BP (palpitations)
Increased pulse
Oxygen saturation reduced
18
Q
What are medical conditions which may benefit from CS
A
- Angina
- Controlled hypertension
- Asthma
- Epilepsy
- Movement disorders e.g. Huntingtons
19
Q
Which medical conditions will CS technique have to be modified
A
Controlled heart failure or airway disease
Chronic anaemia
Well controlled diabetics
20
Q
Which medical conditions requires caution for use of CS?
A
- Severe cardio-resp disease
- Hepatic disease
- Severe psychological illness
- Drug or alcohol abuse
21
Q
What are the options for pain management from simplest to most advanced
A
- LA alone
- LA and IVS
- LA and IHS
- LA and OS or INS (possibly before IVS)
- GA
22
Q
What is the age requirement for IVS and why
A
16+
Children show resistance and even paradoxical reaction to benzodiazepines
23
Q
What is the benefit of midazolam over diazepam in IVS
A
- Double the strength
- Shorter half life
- No significant metabolites allowing smoother and quicker recovery
- More amensic effect
24
Q
What technique is midazolam given in IVS
A
Titration technique
25
What are the properties of midazolam
- Water soluble benzodiazepine
- Clear liquid
- Non-irritant
- 5ml ampoules containing 5mg
26
Define pharmacokinetics
What the body does to the drug
27
Define pharmacodynamics
What the drug does to the body
28
List pharmacodynamics of midazolam in IVS
- Rapid onset
- Acute detachment for 20-30 mins then approx 1 hour relaxation
- Anxiolysis
- Hypnosis
- Amnesia
- Muscle relaxation (thus anticonvulsant)
- Respiratory depression
29
What is the significance of respiratory depression in iVS
It is the most important adverse effect, which can be enhanced by oversedation or rapid injection and requires monitoring via pulse oximeter (mandatory)
30
List pharmacokinetics of midazolam
- Initial recovery via redistribution
- Metabolised in liver
- Metabolites excreted through kidneys
31
What is the half life and recovery of midazolam
Approx 4 hours half life
| 8 hours to recovery
32
Contraindications for IVS with midazolam
- Allergy to benzos
- Pregnancy or breastfeeding
- Severe psychoses
- Alcohol or drug abuse
- Liver or kidney impairment
- Needle phobia
- Doubts about escort
- Poor sedation history (poor compliance or response)
33
What drug interactions occur with midazolam
- Other sedatives or narcotic analgesics
- Antiepileptics
- Antihypertensives
- Anti parkinson
- Cimetidine (gord)
- Disulfiram (alcoholism)
34
How is respiration controlled and why is sedation safe?
- Driven by CO2 (ph) and is GABA-mediated
| - Controlled by higher centres which are maintained in CS
35
What is GABA
- Main NT in the CNS that works on postsynaptic receptors by opening chloride ion channels and preventing depolarisation of propagation of action potentials
36
How do benzodiazepines affect GABA
They increase the effect of GABA
37
What is the reversal agent for midazolam?
Flumazenil
38
How does flumazenil reverse midazolam
It is a competitive inhibitor for GABA
39
Indications for flumazenil
Emergency e.g. overdose of idiosyncratic response
Slow recovery
Difficult journey home
40
Why does the pt need to be monitored even after giving flumazenil
- Flumazenil has a short life 50mins less than midazolam and re-sedation is possible *but no real risk with this
41
Why does the IV remain until the moment of discharge
In case we need to administer flumazenil
42
What is the pre op checklist for iVS
Escort and transport home
| Patient eaten
43
What are the pre-sedation records required
Equipment checklist
MH checked
Second stage written consent
BP and O2 saturation
44
What location is venepuncture common in
Dorsum of hand
| Antecubital fossa
45
Describe venepuncture sequence
Approach best vein at shallow angle
Reduce angle as you advance and push whole needle in gently
Observe flashback and vial fills with blood
Secure
46
What is the titration sequence for healthy patients
2mg over 30s
Wait 60-90s
1mg every 30s until sedated
47
What is the titration sequence for elderly patients
1mg very slowly
Wait 4 mins
0.5mg every 2 minutes until sedated
48
What are signs of sedation
Muscle relaxation
Relief of anxiety - maybe acceptance of mouth prop, LA
Slurred speech and slowed responses
49
What are signs of extravascular injection
Pain on injection
| Swelling at cannulation site
50
Why do we flush with saline before midazolam?
Ensure correct position of cannula
51
Management of extravascular injection
Reposition needle
| If not possible, remove cannulae and pick site mesial to the previous site
52
Management of poorly visible veins
Torniquet, hold hand below heart and pump fist
Ask another clinician
Consider alternative site or technique (IHS)
53
What do we monitor during IVS
- Pulse oximeter for O2 saturation and pulse rate and regularity
- Visually - colour, breathing, airway
54
Management of a drop in oxygen saturation
Ask patient to take deep breaths
| Repeat = use supplemental oxygen
55
What do we assess before discharging patient from IVS
Ability to walk in a straight line
Appear orientated
Able to talk coherently
56
How long is recovery for IVS
Initial recovery in chair
| 30-40 mins in recovery aea
57
What 3 things are mandatory before discharge?
- Discharge blood pressure
- Written and verbal post op instructions to pt and escort
- Remove cannulae and apply dressing
58
How do you record IVS prescription
5mg in 5ml, IV in titration
| re-write it for the number of ampoules given
59
What do we use for inhalational sedation in dentistry
Nitrous oxide and oxygen in sub-anaesthetic concenrations
60
What are the aims of IHS
Produce a comfortable, relaxed, awake pt who is able to cooperate without interference, but remains conscious and retains laryngeal reflexes
61
Indications for inhalation sedation
- CHILDREN
- Anxiety
- Needle phobic
- Gag reflex
- Unpleasant procedures
- Medically compromised
- Where other sedation methods are CI (pregnancy) or if GA CI
62
What are absolute contraindications for IHS
- Acute and chronic nasal obstruction
- 1st trimester pregnancy
- Inability to cooperate or understand (young or psychoses)
- Vitamin b12 deficiency
63
What are the cautions for IHS
- Severe respiratory disease - COPD
- Severe psychotic disorders
- Nasal or facial deformity or recent eye surgery
- Nasal hood fear
64
Why is COPD a CI for iHS
They rely on low concentrations of oxygen to breathe, therefore high o2 during procedures may cause difficulty breathing
65
Pharmacology of nitrous oxide
```
Colourless
Slightly sweet odour and taste
Heavier than air
Non-flammable
Non-irritant
Low potency (wide margin of safety)
```
66
Pharmcodynamics of nitrous oxide
```
Anxiolytic
Sedative
Weak analgesic
Small depression in myocardial function or vasodilation
Euphoria and mood alteration
```
67
What is the onset of nitrous oxide
Rapid - 5mins
68
Why is onset and elimination of nitrous oxide so rapid
It does not enter metabolic pathways and it is poorly soluble allowing rapid distribution
69
How long does it take for nitrous oxide to be eliminated
90% at 10 mins
70
How is nitrous oxide excreted
Via respiratory system
71
List advantages of using nitrous oxide
- Rapid onset and recovery
- No needles (until LA used)
- Easily altered or discontinued drug levels
- Suppresses gag reflex
- Continuous, constant sedation for duration required
- Effective in children
- Some level of analgesia
72
List disadvantages of nitrous oxide
- Support needed throughout for it to work
- Mask may limit access of upper anteriors
- Pollution of NO (greenhouse gas)
- May not work in severe anxiety/phobia
- Diffusion hypoxia
73
What is the equipment required for IHS
- Gases (o2 and no) - can be piped or cylinders
- Nasal hood
- Tubing
- Reservoir bags
- Emergency equipment and drugs
- Scavenging unit
- Instruments for the procedure
74
What are the safety mechanisms for IHS
- Pin index system
- Oxygen fail safe
- Max NO allowed is 70% (means you cannot give 100% NO)
75
What is the pin index system
- Oxygen and NO cylinders have different sized holes for tubing to ensure the right one is attached (prevents giving 100% NO rather than o2)
76
What is the oxygen fail safe?
If oxygen stops working, the NO cuts off
77
How so we adjust the reservoir bag?
- According to patient breathing
| - Usually tidal volume x breaths per minute
78
Define mixture control (IHS)
How much % oxygen and % NO given
79
Define flow control (IHS)
How much gas is given
80
Pre-op checklist for IHS
- Pt can breathe well
- Eaten
- Escort
- BP
- Consent
81
How should the nasal hood fit?
Good seal without gaps around eyes and nose
82
Describe the sequence for IHS
- 100% oxygen
- 10% NO for one minute and engage pt
- 20% NO for one minute and engage pt
- 5% increments until sedated
83
What is adequate sedation for iHS
Pt aware of operative procedure and is accepting it without being fearful
84
What is the normal flow rate for oxygen in IHS
3-10 litres/minute
85
What is the usual % of NO in IHS
20-50%
86
How do we monitor pts during IHS
- Breathing rate (chest and reservoir bag)
- Airway patency
- Actions and responses
87
When is pulse oximetry used in IHS
- If severe medical conditions
| - It is not routine
88
What do we do in IHS after we finish the procedure
Flush with 100% oxygen for 5 mins
89
List symptoms of IHS
- Sensory disturbance
- Tingling or light headed
- Visual or auditory changes
- Temp changes
- Floating
- Day dreaming
- Euphoria
90
What are signs of effective IHS
- Reduced body and facial tension
- Laughing
- Slowed response
- Acceptance of tx
- Reduced hr and resp rate
- Reduced frequency of blinking
91
What are signs of oversedation with NO
- Nausea
- Rigid muscles
- Mouth closure
- Disorientated or apprehensive
- Hallucinations
- Irritable
- Unresponsive
92
How do we manage oversedation of NO
- Reduce dose and monitor
| - If you cannot control then abandon
93
How can we enhance the effects of IHS
- Calm monotone voice for hypnotic effect
- Imagery and visualisation
- Ceiling pictures
- Lighting and music
- No disturbances e.g. others entering room
94
What are the types of scavenging for NO
- Passive - open windows and doors, using fans
| - Active - suctions or scavenging units
95
What are the effects of nitrous oxide pollution/toxicity
- Distal renal tubule calcification
- CNS - neuropathy
- Reduced sperm count
- Bone marrow depression and decreased leukocyte functioning
96
What is the weighted maximum dose suggested by HSE for NO?
Max 100ppm NO in a working environment over 8 hours
97
When do we use oral or intranasal sedation
- Unable to accept venepuncture
| - Used before venepuncture to reduce anxiety
98
What is the most common drug for oral and intranasal sedation
Midazolam
99
Why is OS and intranasal sedation avoided
Less predictable as the dose is not titrated according to response
100
Instructions for patients before procedure (CS)
- Take routine medication
- Light meal
- No alcohol or drugs
- Bring escort
101
What is a suitable escort
Over 18 who can physically support the patient, and has no other responsibilities with them e.g. children, can understand English (For post op instructions)
102
What are post op instructions for CS
- FOR 24 HOURS -
- Do not travel alone - with escort only, ideally by car
- Do not drive or ride a bike
- Do not operate machinery
- Do not drink alcohol
- Do not return to work or sign legal documents
103
Venous assessment before IVS
- Check quantity, quality and position of veins suitable for access (on hands and antecubital fossa)
- Ask patient where they usually get bloods taken from
104
Role of diazepam as a premedication for IVS
- Low dose used to relax the patient the night before the appointment to allow a good night's rest (or the day of the appointment)
105
Dose of premedication diazepam for IVS
2mg, 5mg or 10mg
| Usually start at 2mg to assess the response
106
How is respiratory depression enhanced in IVS?
- Administrating an excessively rapid 'bolus'
- Overdosage
- Those with existing respiratory conditions
- Patients who have taken other depressants e.g. opiates or alcohol
107
When do you have to be careful with fluamazenil?
If you suspect allergy to the midazolam (as flumazenil is also a benzodiazepine)
108
How to administer flumazenil
- IV
- 1ml increments at 30s intervals until 5ml given
- Observe the patient
109
Advantages of IVS as a CS technique
- Site of administration away from operating site
- Single dose
- Rapid onset
- Mouth breathing is not important
- No NO pollution or occupational risk
110
Disadvantages of IVS as a CS technique
- Needs an escort and must rest for the rest of the day
- May increase anxiety by disinhibition effect
- Intravascular injection may damage vessels
- Cannot be discontinued or removed once given
- Profound respiratory depression with overdose
111
How much should the reservoir bag inflate and deflate?
Collapse gently by 1/4 and then inflate by 1/4
| If the balloon is too inflated then reduce the flow rate
112
How many breathes per minute is common?
12-20
113
How much air is inhaled with eat breath
500ml
