SPECIAL CARE pharmacology of conscious sedation

Question 1

what does the body do to a drug (4)?

Answer 1

absorption
distribution
metabolism
excretion

Question 2

explain the pathway of midazolam with IV sedation?

Answer 2

rapid rise in plasma levels
drug passes through RHS heart, pulmonary circulation and the LHS heart
goes to the brain via arterial system
effects start once crossed blood brain barrier

Question 3

what is the hand-heart-brain circulation time with IV midazolam?

Answer 3

25 seconds

Question 4

what are the 2 ways a pt recovers from sedation?

Answer 4

a. redistribution of drug from CNS into body fat
b. uptake and metabolism of the drug by the liver and elimination by kidneys

Question 5

what mechanism is responsible for the initial recovery from sedation?

Answer 5

redistrubition

Question 6

what is the alpha half life?

Answer 6

the time taken for the serum concentration to drop by 50%
redistribution is responsible for this

Question 7

what is the beta half life?

Answer 7

time taken to remove half the drug from the body
elimination of the remaining drug

Question 8

beta half life of midazolam?

Answer 8

2 hours

Question 9

what is used to compare the pharmacokinetic effects of sedation agents?

Answer 9

elimination half life (beta half life)

Question 10

what does the drug (conscious sedation drugs) do to the body?

Answer 10

sedation
analgesia
anxiolysis

Question 11

how are benzodiazepines differentiated?

Answer 11

affinity for receptors (potency)
half life
active metabolites

Question 12

describe action potentials and sedation?

Answer 12

AP starts when sodium and potassium start moving along concentration gradient

Potassium out and chloride in - drops below 70 = hyperpolarisation = sedation - short acting

Want to extend the hyperpolarisation state during sedation

Question 13

describe benzodiazepines mechanism of action?

Answer 13

GABA controlled synaptic flow of chloride ions
activation of benzodiazepine receptors enhances the flow of chloride ions

Chloride ions entering the cell make the resting membrane potential more negative - this makes it hard to fire APs which reduces:
- polysynaptic transmission
- depressing the uptake of sensory information

Question 14

according to AAPD, what are the indications for nitrous oxide?

Answer 14

pt who are fearful, anxious, or uncooperative
pt with special health care needs
pt with gag reflexes that interferes with dental care
pt who do not respond adequately to LA
younger pts who must undergo lengthy dental procedures

Question 15

describe the mechanism of action of nitrous oxide?

Answer 15

enhance the activity of GABA
biphasic effect: initially enhances neuronal activity, followed by period of inhibition
effects are dose dependant

Question 16

explain the effects of nitrous oxide at low and high doses?

Answer 16

low concentration: reduce anxiety and produce a sense of relaxation
high concentration: deeper level of sedation

Question 17

how much nitrous oxide is mixed with 02 for the desired level of sedation?

Answer 17

20-50%

Question 18

contraindications of nitrous oxide?

Answer 18

1st trimester pregnancy
history of COPD
vit B12 deficiency
substance abuse hx
history of mental health conditions

Question 19

why is diazepam no longer used for IV sedation?

Answer 19

causes vein damage: pain, thrombophlebitis, skin ulceration

Question 20

diazepam half life?

Answer 20

30 hours

Question 21

what is the max dose of midazolam for an adult pt?

Answer 21

10mg

Question 22

what is the max dose of midazolam for an elderly pt?

Answer 22

3.5mg

Question 23

what must a drug be to reach the brain?

Answer 23

lipid soluble

Question 24

elimination half life of midazolam?

Answer 24

1.9 hours

Question 25

what are the effects of midazolam

Answer 25

conscious sedation with acute detachment for 20-30 mins post administration a period of relaxation which may last another hour anterograde amnesia - loss of memory muscle relaxant anticonvulsant activity

Question 26

where is midazolam metabolised?

Answer 26

in the liver, some taking place in the bowel

Question 27

what metabolite does midazolam produce which is lipid soluble? and what is its half life?

Answer 27

alpha-hydroxymidazolam 1.2 hours half life

Question 28

what is the titrations measurements of midazolam for an adult?

Answer 28

2-2.5mg 5-10mins before procedure (2mg/min) increase in steps of 1mg if required usual total dose = 3.5-5mg

Question 29

what is the titration measurements for midazolam for an elderly pt?

Answer 29

initially 0.5-1mg 5-10 mins before procedure (2mg/min) increase by 0.5-1mg if required

Question 30

at what time can you discharge a pt after IV midazolam?

Answer 30

2 hours (could be less than) after completion of tx

Question 31

what is the impact of liver dysfunction on midazolam pharmacokinetics during IV infusion for conscious sedation?

Answer 31

decreased metabolism; reduced hepatic clearance of midazolam, prolonging its half life increased plasma levels: with impaired metabolism, there is a high risk of midazolam accumulating in the bloodstream potential for prolonged sedative effects

Question 32

pre-cautions of midazolam?

Answer 32

- no analgesia - for a short time after injection, laryngeal reflexes may be dulled - too rapid injection can cause respiratory depression and apnoea - overdose may produce profound resp depression in pts with impaired respiratory function/ taking depressants i.e., alcohol - possibility of disinhibition (adverse reactions) - once reached end point do not give any more

Question 33

what are the drug drug interactions of benzodiazepines?

Answer 33

opioids - increase risk of resp depression, sedation and hypotension propofol - increase risk of resp depression and hypotension

Question 34

what are the drug drug interactions of nitrous oxide?

Answer 34

opioids - increase risk of resp depression and hypotension

Question 35

what medications may interfere with sedation?

Answer 35

antidepressants antibiotics antifungals anti-seizure blood pressure meds narcotic antagonists

Question 36

what foods interact with benzodiazepines?

Answer 36

grapefruit juice - increases the level of drug in the blood

Question 37

what is the effect of St Johns Wort on benzodiazepines?

Answer 37

plasma concentrations of BZD decreases by half reduce the effect of BZD

Question 38

side effects of BZDs?

Answer 38

resp depression hypotension ataxia and confusion (elderly) depression dizziness drowsiness and fatigue muscle weakness sleep disorder vision disorder tremor withdrawal syndrome

Question 39

side effects of midazolam?

Answer 39

vomiting (very common) skin reactions

Question 40

why is it mandatory for someone else to be in the room with dentist and pt during IV sedation?

Answer 40

sexual hallucinations

Question 41

contraindications of BZDs?

Answer 41

allergy/ hypersensitivity severe resp depression / obstructive sleep apnoea glaucoma pregnancy/ breastfeeding concurrent use of alcohol/ CNS depressants

Question 42

pre cautions for all BZDs?

Answer 42

avoid prolonged use and abrupt withdrawal elderly Hx of alcohol dependance/ abuse Hx of drug depednance and abuse personality disorder resp disease

Question 43

pre cautions for midazolam?

Answer 43

cardiac disease debilitated pt (in children) - reduce dose

Question 44

why is there a risk of potentially fatal resp depression when BZDs are used along side an opioid?

Answer 44

produce additive CNS depressant effects increasing risk of sedation, resp depression, coma and death

Question 45

what does MHRA/CHM advise in regards to BZDs and sedation?

Answer 45

1. BZD and opioid interaction 2. BZDs should only be administered by experiences person with training in anaesthesia and airway management 3. for conscious sedation always 1mg/ml preparation 4. flumazenil must be available

Question 46

what are the risks of taking BZDs when pregnant?

Answer 46

risk of neonatal withdrawal symptom high dose during late pregnancy/ labour = neonatal hypothermia, hypotonia, resp depression

Question 47

can you give BZDs to pts with hepatic/ renal impairment?

Answer 47

mild to moderate hepatic impairment - advised caution severe hepatic impairment - avoid renal impairment - caution

Question 48

what is the first choice of IV sedation for dentists?

Answer 48

Midazolam as a single drug

Question 49

why should IV agents be used with great caution in the elderly?

Answer 49

altered drug distribution due to: - decreased total body fat water - increased body fat - decreased serum albumin - altered hepatic metabolism - altered renal excretion

Question 50

why should IV agents be used with great caution in the young?

Answer 50

unpredictable and disinhibition

Question 51

what is flumazenil?

Answer 51

a BZD antagonist

Question 52

what are the effects of Flumazenil?

Answer 52

reverses the sedative, cardiovascular and resp depressant effects of midazolam

Question 53

half life of flumazenil?

Answer 53

50 mins half life