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E-lfh FRCA Primary: Pharmacology - IV Induction Agents > Ketamine > Flashcards

Ketamine Flashcards

1
Q

Is ketamine a weak acid or base, and what is its pKa?

A

Weak base with a pKa of 7.5

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2
Q

Which isomer of ketamine is the more useful one?

S (+) ketamine
R (-) ketamine

A

S (+) ketamine has a number of beneficial pharmacokinetic properties with clinical implications.

S(+) ketamine has greater affinity than R(-) ketamine at phencyclidine binding sites on the N-methyl-D-aspartate (NMDA) receptor, with a resultant doubling of potency compared to the racemic mixture (equal amounts of R(-) and S(+) isomers) in producing anaesthesia and analgesia.

S(+) ketamine also has a reduced recovery time and, since the incidence of psychological sequelae are equal at equal plasma concentrations, the lower dose required of S(+) ketamine results in fewer psychological side-effects.

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3
Q

What is the typical induction dose of ketamine (racemic mixture)? Give both IV and IM doses

A

0.5 - 2 mg/kg IV

4-10 mg/kg IM

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4
Q

What is the oral bioavailability of ketamine?

A

20-25%

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5
Q

What percentage of ketamine is protein bound?

A

20-50%

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6
Q

What is the volume of distribution of ketamine?

A

3 L/kg - it is increased in the critically ill

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7
Q

What is the elimination half life of ketamine?

A

2-3 hours

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8
Q

How is ketamine metabolised?

A

In the liver, by cytochrome P450, undergoing demethylation and hydroxylation of the cyclohexanone ring to metabolites norketamine (20% relative activity) and dehydronorketamine.

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9
Q

What is the clearance rate of ketamine metabolites?

A

The metabolites are conjugated and excreted in the urine with a relatively large clearance of 890-1227 ml/min. Elimination half-life is 2-3 hours.

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10
Q

An adult male is admitted to the ICU after an acute asthma attack. He is intubated, sedated and on full intermittent positive-pressure ventilation.

He has widespread expiratory wheezes on auscultation of his chest, saturations of 85%, high peak airway pressures and is sweating profusely. His BP is 180/80.

Which of the following are true statements regarding appropriate treatment options?

A. Administer 100% oxygen

B. Corticosteroid administration is inappropriate due to the slow onset of action

C. Atenolol should be safe to treat hypertension

D. Exclude a pneumothorax by doing a CXR

E. Ketamine is contraindicated due to the significant hypertension

F. Ketamine is a potent bronchodilator in status asthmaticus

A

A. True. Administer 100% oxygen to treat hypoxia.

B. False. Corticosteroids should be administered to treat the inflammatory component of asthma.

C. False. Β-blockers should be avoided in asthma as they may worsen bronchoconstriction.

D. True. An acute pneumothorax should be excluded.

E. False. Although ketamine stimulates the sympathetic nervous system it is not contraindicated since ketamine causes bronchodilatation.

F. True. Ketamine causes bronchodilatation.

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11
Q

Is the following a true reflection of the effect of ketamine on the respiratory system?

Respiratory drive remains relatively unaffected

A

True. Ketamine has minimal effects on respiratory drive.

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12
Q

Is the following a true reflection of the effect of ketamine on the respiratory system?

All doses of ketamine lead to respiratory depression

A

False. Low dose ketamine use does not depress respiration significantly.

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13
Q

Is the following a true reflection of the effect of ketamine on the respiratory system?

Ketamine causes tachypnoea

A

False. Ketamine has minimal effects on respiratory drive.

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14
Q

Is the following a true reflection of the effect of ketamine on the respiratory system?

Children are predisposed to laryngospasm and upper airways obstruction

A

True. Children may develop laryngospasm due to increased salivation

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15
Q

Is the following a true reflection of the effect of ketamine on the respiratory system?

Owing to bronchoconstriction, ketamine should not be used in patients with asthma

A

False. Ketamine causes bronchodilatation which is beneficial in treating acute asthma.

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16
Q

Is the following a true reflection of the effect of ketamine on the respiratory system?

Silent aspiration is a potential problem during anaesthesia

A

True. Depressed airway reflexes may lead to silent aspiration.

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17
Q

Is the following statement a true reflection of the effect of ketamine on the CNS?

There is an increase in cerebral metabolism

A

True. Ketamine leads to an increase in cerebral metabolism.

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18
Q

Is the following statement a true reflection of the effect of ketamine on the CNS?

Patients may appear to be in a cataleptic state

A

True. Ketamine leads to dissociative anaesthesia.

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19
Q

Is the following statement a true reflection of the effect of ketamine on the CNS?

There is a decrease in cerebral oxygen metabolism

A

False. Ketamine causes an increase in cerebral metabolism.

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20
Q

Is the following statement a true reflection of the effect of ketamine on the CNS?

Alpha rhythms are abolished

A

True. The EEG predominantly reveals theta activity.

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21
Q

Is the following statement a true reflection of the effect of ketamine on the CNS?

Cerebrovascular responsiveness to CO2 increases

A

False. Responsiveness to CO2 seems preserved.

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22
Q

Is the following statement a true reflection of the effect of ketamine on the CNS?

Hallucinations and other emergence reactions are heightened in the paediatric population

A

False. Emergence reactions are more common in adults.

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23
Q

Is the following statement a true reflection of the effect of ketamine on the CNS?

Benzodiazepines are effective in reducing the emergence reactions in the adult population

A

True. Benzodiazepine co-administration reduce emergence reactions.

24
Q

Ketamine (true or false):

Is a phencyclidine derivative

A

True

25
Q

Ketamine (true or false):

Is a potent analgesic

A

True

26
Q

Ketamine (true or false):

Has two isomers S(+) and R(-)

A

True

27
Q

Regarding the physiochemical properties of ketamine (true or false):

It has a molecular weight of 300

A

False. Its molecular weight is 238, making it relatively small and easier to diffuse across membranes.

28
Q

Regarding the physiochemical properties of ketamine (true or false):

It has high lipid solubility

A

True

29
Q

Regarding the physiochemical properties of ketamine (true or false):

R(-) is more potent than S(+)

A

False. S(+) is 3 times more potent.

30
Q

Regarding the physiochemical properties of ketamine (true or false):

S(+) has greater affinity for the NMDA receptor

A

True

31
Q

Regarding mechanism of action and the NMDA receptor (true or false):

Ketamine’s main action is via interaction at NMDA receptors

A

True

32
Q

Regarding mechanism of action and the NMDA receptor (true or false):

Full activation of an NMDA receptor is only ligand-gated

A

False. It is ligand- and voltage-gated.

33
Q

Regarding mechanism of action and the NMDA receptor (true or false):

Magnesium also has an effect on the NMDA receptor

A

True

34
Q

Regarding mechanism of action and the NMDA receptor (true or false):

The NMDA receptor is a type of glutamate receptor

A

True

35
Q

Regarding the pharmacokinetic properties of ketamine (true or false):

It has a slow IV onset time

A

False. It is rapid, at ~30 seconds.

36
Q

Regarding the pharmacokinetic properties of ketamine (true or false):

It is 20-50% protein bound

A

True

37
Q

Regarding the pharmacokinetic properties of ketamine (true or false):

It has a large volume of distribution

A

True. Its volume of distribution is 3 L/kg.

38
Q

Regarding the pharmacokinetic properties of ketamine (true or false):

It has an elimination half-life of 100 mins

A

False. Its elimination half-life is 2-3 hours.

39
Q

Regarding the pharmacokinetic properties of ketamine (true or false):

It has a large clearance of 890-1227 ml/min

A

True

40
Q

Regarding the pharmacokinetic properties of ketamine (true or false):

It can be delivered as a TCI

A

True

41
Q

Regarding the pharmacokinetic properties of ketamine (true or false):

It follows a one-compartment model

A

False. It follows a three-compartment model.

42
Q

Regarding the pharmacokinetic properties of ketamine (true or false):

It is hepatically metabolised

A

True

43
Q

Regarding the pharmacodynamic effects of ketamine (true or false):

It produces a bradycardia

A

False. It produces a tachycardia.

44
Q

Regarding the pharmacodynamic effects of ketamine (true or false):

It increases BP and cardiac output

A

True

45
Q

Regarding the pharmacodynamic effects of ketamine (true or false):

It regularly produces apnoea

A

False. Only if a large rapid IV bolus is given. It is often used for procedural sedation due to its preservation of airway reflexes and minute ventilation.

46
Q

Regarding the pharmacodynamic effects of ketamine (true or false):

It increases cerebral blood flow and cerebral metabolism

A

True

47
Q

Regarding the pharmacodynamic effects of ketamine (true or false):

Emergence phenomena are common

A

True. 5-30% from mild to severe.

48
Q

Regarding the clinical applications of ketamine (true or false):

It is a useful adjunct analgesic at 1 mg/kg

A

False. It is useful at 0.15-0.25 mg/kg. It is also useful as part of an opioid-sparing anaesthetic technique.

49
Q

Regarding the clinical applications of ketamine (true or false):

It is contraindicated in traumatic brain injury

A

False. It is commonly used in RSI of critically injured and brain injured patients - preservation of MAP is likely more important and there have been to date no adverse clinical outcomes reported from its use. Its is standard practice in HEMS RSI.

50
Q

Regarding the clinical applications of ketamine (true or false):

It is a useful bronchodilator in severe bronchospasm

A

True

51
Q

Regarding the clinical applications of ketamine (true or false):

Its cardiovascular side-effects make it a suitable induction agent in the clinically shocked patient

A

True

52
Q

Regarding the clinical applications of ketamine (true or false):

Co-administration of glycopyrrolate can be a useful anti-sialogogue when used for procedural sedation

A

True

53
Q

Regarding the clinical applications of ketamine (true or false):

Co-administration of opiates helps mediate any emergence phenomena

A

False. Co-administration of benzodiazpines helps mediate any emergence phenomena.

54
Q

Regarding the clinical applications of ketamine (true or false):

It can be given IM as an induction agent, at 4-10 mg/kg

A

True

55
Q

Regarding the clinical applications of ketamine (true or false):

It should be avoided in patients with porphyria

A

True

56
Q

Regarding the clinical applications of ketamine (true or false):

It is useful in chronic pain due to its effect on NMDA receptors

A

True

57
Q

Regarding the clinical applications of ketamine (true or false):

It can be given as an infusion

A

True. For refractory bronchospasm in ICU, or as a maintenance agent during anaesthesia, especially in low resource settings.

E-lfh FRCA Primary: Pharmacology - IV Induction Agents (6 decks)

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