Induction Agents and Opioids ☺️

Question 1

What is the definition of

• analgesia
• anaesthesia
• sedative
• onset
• offset

Answer 1

Analgesia = Pain relief
Anaesthesia = unconsciousness
Sedative = Anxiolytic
Onset = Time taken for drug to start acting
Offset = Time taken for drug to stop being effective

Question 2

Describe the function and properties of GABA

Describe the function and properties of NMDA

Answer 2

GABA

• reduce neuronal activity
• sedative, anxiolytic, anticonvulsant, muscle relaxant

NMDA
-increase neuronal activity => cascade leads to sensitization of DH

Question 3

Propofol

• positives
• negatives and SE
• metabolism and onset/offset

Answer 3

GABA agonist => IV induction

• antiemetic, itch, convulsant
• BD
• pleasant dreams
• low ICP
• cardiac, resp depression
• no malignant hyperpyrexia risk

SE

• anaphylaxis
• pancreatitis from increased TAG
• thrombophlebitis

Rapid onset and recovery
Metabolised by liver, kidney

Question 4

Barbiturates vs benzodiazepines

• common properties
• differences

Answer 4

GABA agonists

• anticonvulsants and sedatives
• low ICP
• amnesia
• respiratory depression
• fall in BP, HR
• accumulates in fat
• fast onset, offset
• liver met => kidney excretion

Barbiturates (-pental, -barbital)

• CYP interactions
• v narrow therapeutic index
• NOT ANALGESIC

Benzodiazepines (-am)

• Antidote => flumenazil infusion antidote
• drowsiness, confusion
• paradoxical reactions

Question 5

Etomidate

• positives
• negatives
• metabolism and excretion

Answer 5

GABA agonist

• NOT ANALGESIC
• low ICP
• no BP, HR fall so can be used in haemodynamic instability
• resp depression
• rapid onset, offset
• liver met => kidney excretion

11b hydroxlyase inhbition => GC, MC adrenal insufficiency

Question 6

Ketamine

• positives
• negatives
• metabolism and excretion

Answer 6

NMDA antagonist

• analgesic
• sedative
• SNS stimulation, suitable for haemodynamically unstable
• minimal resp depression
• BD
• increased ICP
• liver met => kidney excretion

-nightmares

Question 7

Morphine

• positives
• negatives
• antidote

Answer 7

MOP agonist, long T1/2

• Liver met => kidney excretion
• analgesia
• N+V
• cough suppression
• resp, cardiac depression

Naloxone infusion due to short T1/2

Question 8

Fentanyl properties
Codeine properties
Tramadol properties 
Remifentanyl properties
compared to morphine

Answer 8

Fentanyl - MOP, DOP, short T1/2

• T1/2 increases as infusion time increases
• more potent than morphine

Codeine - MOP, KOP
-less potent than morphine

Tramadol - MOP, SNRI inh

• less potent than morphine
• risk of seretonin syndrome

Remifentanyl - MOP

• vvv short T1/2
• metabolised by blood/tissue esterases (enzymes are everywhere)
• SEDATIVE and ANALGESIA

Question 9

What is the antidote to opioids

• what are the pharmacokinetics
• what are the SE

Answer 9

Naloxone
-due to short half life, needs infusion

May cause

• rebound agonist
• HTN
• pulmonary edema
• arrythmia

Question 10

TIVA

• mixture
• pros and cons

Answer 10

Total IV anesthesia
-propofol + remifentanyl

Pros

• no gas
• stable CV
• decreased N+V
• increased tube tolerance

Cons

• based on algorithms
• risk of patient awareness