Module 3b: specific IV anaesthetic agents

Question 1

Give 4 characteristics of propofol?

Answer 1

• 2,6 di-isopropylphenol
• NOT soluble in water-> prepared as emulsion (soya bean oil, egg yolk + glycerol)
• Problems with fat emulsion
• Multiple ampoule sizes: 20ml, 50ml, 100ml OR 1% or 2%

Question 2

What is the pharmacokinetics of propofol?

Answer 2

extremely lipid soluble

crosses BBB easily

extra hepatic metabolism->rapid plasma clearance->rapid emergence

Versatile agent: induction, maintenance, sedation at lower doses

Question 3

What are the induction dose for adults, elderly and children in propofol

Answer 3

Adults: 2-2.5mg/kg
Elderly: 1-1.5mg/kg
Children: 2.5-3mg/kg

Question 4

CNS effects of propofol?

Answer 4

Rapid LOC + recovery
less hangover effect
no excitatory effects
slight analgesic effect

Question 5

CVS effects of propofol?

Answer 5

dose dependent CVS depression

decreased systemic vasc resistance

Decreased BP

Slight increase in HR

Question 6

Respiratory effects of propofol?

Answer 6

dose-dependent depression
apnoea on induction close to 100%
inhibits laryngeal reflexes
NO histamine release

Question 7

Other effects of propofol?

Answer 7

anti-emetic (used in PONV)

Question 8

What is porpofol infusion syndrome (PRIS)

Answer 8

prolonged high dose infusion which presents with lipaemia, metabolic acidosis and myopathy

Question 9

In which patients should you be careful with giving propofol?

Answer 9

Elderly
Cardiac failure
hypovolaemia
Fixed cardiac output: AS/MS, HOCM

Question 10

In what scenario would propofol be ideal?

Answer 10

TIVA Total intravenous anesthesia (TIVA)
Conscious sedation
asthma
porphyria
hx of PONV
hx of malignant hyperthermia

Question 11

Give the physical properties of thiopentone?

Answer 11

yellow powder(mix with H2O or N/saline)
pH 10.5->precipitates with acides
Strength 2.5% (25mg/ml)
Solution stable 24-48hrs

Question 12

What is the dosage of thiopentone in adults, children and elderly?

Answer 12

Adults: 3-5mg/kg
Children: 5-6 mg/kg
Elderly: caution

Question 13

CNS effects of thiopentone?

Answer 13

LOC in 30 sec (used in rapid sequence induction)

Smooth, no reflex movements/coughing

Antanalgesic-> lowers pain threshold

Anti-convulsant

Neuroprotectove: decreased CMRO2 +ICP

Question 14

CVS effects of thiopentone?

Answer 14

Decreased CO (10-20%) by:
Vasodilation, negative inotropy, decreased central catecholamine release

Compensatory increase in HR

Question 15

Respiratory effects of thiopentone?

Answer 15

dose-dependent apnoea
no depression of laryngeal reflexes
histamine release

Question 16

Other effects of thiopentone

Answer 16

irritant to tissues: venous thrombosis with older 5% solutions

Intra-arterial injection precipataes solid crystals-> acute ischemia of limb

Question 17

What are the contraindication of thiopentone?

Answer 17

Absolute: porphyria, known allergy

Relative: asthma, CVS instability(cardiac failure, fixed CO, hypovoloaemia)

Question 18

Give the physical properties of etomidate?

Answer 18

10ml ampoules (2mg/ml=20mg in ampoule)
Clear solution with propylene glycol
Opaque with emulsion

Question 19

What is the dosage in etomidate

Answer 19

0.2-0.3mg/kg (adult 16-20mg)

Question 20

Pharmacokinetics of etomidate?

Answer 20

rapid recovery: 6-8 min
Repeated doses NOT cumulative

Question 21

True or false: etomidate can be used for induction only

Answer 21

True: it causes adrenocortical suppression in infused

Question 22

Etomidate effects on CNS?

Answer 22

rapid LOC
Myoclonus and involuntary movements

Question 23

Etomidate effects on CVS?

Answer 23

most stable: little change in BP/HR

Question 24

Etomidate effects of resp?

Answer 24

minimal resp depression, NO HISTAMINE RELEASE

Question 25

Etomidate effects on GIT?

Answer 25

PONV

Question 26

Etomidate effects on endocrine

Answer 26

inhibition of steroid synthesis

Question 27

Physical properties of ketamine

Answer 27

- Solutions of 1%(10mg/ml) - long shelf half life - no pain on injection - NMDA receptor antagonist

Question 28

4 characteristics of ketamine?

Answer 28

Unusual among induction agents NMDA receptor antagonist Causes LOC + analgesic Given IV, IM or orally

Question 29

CNS effects of ketamine?

Answer 29

dissociative anaesthetic Complete analgesia Increased ICP and IOP Psychiatric reactions such as hallucinations

Question 30

CVS effects of ketamine

Answer 30

central sympathetic stimulant: - Increased HR - Increased BP - Increased CO - Increased SVR

Question 31

Respiratory effects of ketamine?

Answer 31

minimal respiratory depression preserved pharyngeal reflexes maintains airway bronchodilator (sympathetic stimulation) Increased salivation

Question 32

Other considerations with ketamine

Answer 32

PONV Uterine contraction in 1st trimester drug of abuse

Question 33

Indications of ketamine

Answer 33

Sick and unstable adults and children  Burns surgery  Debridement  Change of dressings  Short diagnostic procedures  Analgesia  Battlefield anaesthesia  Status asthmaticus

Question 34

Contra indication of ketamine

Answer 34

CVS pathology  IHD, hypertension, AAA, CCF  ↑ ICP  ↑ IOP and “open eye”  Psychiatric patients  Epileptics  Thyrotoxicosis  Early pregnancy

Question 35

Give the characteristics of benzodiazepines

Answer 35

sedative act on GABA receptor given as premedication and intra-operative sedation

Question 36

What oral premedications form part of benzodiazepines

Answer 36

 Lorazepam, temazepam, diazepam, midazolam

Question 37

What medication forms part of IV sedation

Answer 37

midazolam

Question 38

Give the physical properties of midazolam

Answer 38

5mg ampoules (1mg/ml) / 15mg ampoules (5mg/ml)

Question 39

What is the dosage for midazolam

Answer 39

premed: 0.5mg/kg Adults 7.5-15 mg Children 0.25-0.5mg/kg PO Induction: 0.1-0.3 mg/kg Sedation 0.1mg/kg

Question 40

CNS effects of midazolam

Answer 40

does not occur in one arm-brain circulation time (55-140sec) anterograde amnesia anxiolysis sedation

Question 41

CVS, resp, uterus and git effects of midazolam

Answer 41

CVS: stable resp: little effect git: low incidence of PONV Uterus: crosses placenta casuing flopping neonate

Question 42

what is flumazenil

Answer 42

benzodiazepine antagonist

Question 43

What is the ideal drug for TIVA

Answer 43

propofol

Question 44

What are the indications of TIVA

Answer 44

Risk of malignant hyperthermia – Severe PONV in prior case – Day-case surgery – Cheaper than gases