Ketamine

Question 1

What is the brand/trade name for ketamine?

Answer 1

• Ketalar

UpToDate - Ketamine: Drug Information

Question 2

What is the pharmacologic category/class of ketamine?

Answer 2

• General Anesthetic
• Phecyclidine derivative

Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Question 3

What is the mechanism of action of ketamine?

Answer 3

NMDA receptor antagonist — antagonizes glutamate

• secondary receptor actions at opioid, MAO, serotonin, NE muscarinic, Na+ channels
• induces “catelepsy” - dissociates thalamus (sensory) from the limbic system (awareness)
  _{Afferent impulses transmitted to cortical regions but are not interpreted}

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), pp. 109-110

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Question 4

Ketamine has been shown to enhance opioid-induced ____________ and prevent _____________

Answer 4

• analgesia
• hyperalgesia

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), p. 110

Question 5

What is the adult/pediatric dosing of ketamine for induction?

Answer 5

• 1-2 mg/kg IV

This is the dose seen most commonly, but sources range from 0.5-4 mg/kg

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), p. 110 - Box 9.3

UpToDate - Ketamine: Drug Information

Question 6

What is the dosage range of ketamine for maintenance of anesthesia (continuous infusion)?

Answer 6

• 15-45 mcg/kg/min (1-3 mg/min)

Nagelhout (7th ed.), p. 110 - Box 9.3

Question 7

What is the onset of action for ketamine?

Answer 7

• 30-60 seconds

may take up to 5 minutes for peak effect (clinical anesthesia)

Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1

Nagelhout (7th ed.), p. 110

Question 8

What is the duration of action for ketamine?

Answer 8

• 10-30 minutes — awakening is related to redistribution from brain

may require 60-90 minutes to return to full orientation

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

UpToDate - Ketamine: Drug Information

Question 9

What organ(s) are responsible for ketamine’s clearance (metabolism/elimination)?

Answer 9

• Metabolism: Liver (P450)
• Elimination: Kidneys

Half-life: ~2-3 hours

Anesthesia Guidebook - Episode 17: Anesthesia Top Drawer Run Down - Part 1

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Question 10

Lingering effects of ketamine may be related to it’s active metabolite ______________, which has a potency of ~20-30% of ketamine

Answer 10

• Norketamine

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), p. 110

Question 11

BONUS

Chronic ketamine use induces the enzymes that metabolize __________

Answer 11

KETAMINE!

• this manifests as a rapid escalation in tolerance

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Question 12

Cardiovascular effects of ketamine include:

Answer 12

↑ SNS tone with subsequent increases in:

• HR & CO
• SVR
• PVR

Stimulates endogenous catecholamine release & inhibits reuptake

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Question 13

Name 3 scenarios where the cardiovascular effects of ketamine may be detrimental instead of advantageous and why

Answer 13

• Severe CAD — may alter oxygen supply/demand balance
• Severe RV failure — increases PVR
• Depletion of catecholamine stores/sympathectomy — direct myocardial depressant effects are unmasked when endogenous catecholamines are depleted (e.g. sepsis, sympathectomy)

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Question 14

What are the respiratory effects of ketamine?

Answer 14

• Bronchodilation
• Upper airway muscle tone and reflexes remain intact
• Maintains respiratory drive
  _{(may cause transient apnea with large doses/rapid administration)}
• ↑ oral and pulmonary secretions
  _{(use glyco or atropine)}

Agent of choice in any patient with reactive airway disease

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), pp. 111-112

Question 15

What effect does ketamine have on the CNS (e.g. CMRO₂, cerebral blood flow, ICP)

Answer 15

• ↑ CMRO₂
• ↑ CBF
• ↑ ICP
  _{minimal to nonexistent with normocarbia}
• ↑ EEG activity
  _{theoretical potential for causing seizures}

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), pp. 110-111

Question 16

Why should ketamine be avoided during eye surgery?

Answer 16

• Possibility for increased IOP
• Causes nystagmus and eye twitching

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), p. 112

Question 17

Emergence from anesthesia with ketamine is associated with ______________

Answer 17

• delirium/psychic disturbances

often presents as nightmares and hallucinations

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), p. 111

Question 18

What is the most effective way to prevent emergence delirium associated with ketamine?

Answer 18

• Coadministration with a benzodiazepine (midazolam > diazepam)

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

Nagelhout (7th ed.), p. 111

Question 19

Name several factors that increase the risk for emergence delirium with ketamine

Answer 19

• age between 16-65 years
• female gender
• large doses (>2 mg/kg)
• Hx of psychiatric disorders

Apex Unit 4: Pharmacology 1; Intravenous Anesthetics; Lesson 4. Ketamine

UpToDate - Ketamine: Drug Information

Question 20

What is the concentration (mg/mL) of ketamine vials?

Answer 20

• 10 mg/mL (20 mL)
• 50 mg/mL (10 mL)
• 100 mg/mL (5 mL)

UpToDate - Ketamine: Drug Information