*Induction Drugs (Etomidate & Ketamine) (Exam II) Flashcards by Krista Flores

In general, thiobarbiturates are much more _____ soluble and have a greater _______ than oxybarbiturates.

What atom do thiobarbiturates have in lieu of an oxygen in the second position (like oxybarbiturates)?

Lipid; potency
Sulfur

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What is unique about Etomidate’s organic chemical structure?

It is the only carboxylated imidazole containing compound.

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When is etomidate water-soluble vs lipid-soluble?

H₂O-soluble at acidic pH.
Lipid-soluble at physiologic pH.

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What percentage of etomidate is propylene glycol?
What is the result of this?

35% propylene glycol
resulting in pain on injection and venous irritation.

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Which induction agent can be given without an IV?
How is this?

Etomidate - can be given sub-lingual.

Only drug with direct systemic absorption in oral mucosa that bypasses hepatic metabolism

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Why does etomidate have a low incidence of myoclonus?

Trick Question. Etomidate has a high incidence of myoclonus, just like all other induction agents.

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What is the onset of Etomidate?

1 minute

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How much of Etomidate is protein bound?
What protein does it bind to?

76% albumin bound

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What is etomidate’s Vd?
How does clearance compare to thiopental?
What is the result of this clearance?

Large Vd
5x faster clearance than thiopental resulting in a prompt awakening.

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What metabolizes Etomidate?

Hydrolysis by hepatic microsomal enzymes and plasma esterases.

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What is the Elimination Half-time and profile of Etomidate?

Elimination 1/2 time: 2-5 hours

Elimination:
* 85% in urine
* 10% - 13% in bile

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What is the induction dosage range for Etomidate?

0.3 mg/kg IV

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What is Etomidate an alternative for IV induction?

Propofol or Barbituates

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Drug effects that Etomidate does not have?

No hangover or cumulative drug effect

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What is the best use for Etomidate?

Induction for unstable cardiac patients.

Especially with little or no cardiac reserve

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What needs to be used concurrently with etomidate when performing a laryngoscopy/tracheal intubation?
Why?

use with Opioids
etomidate has no analgesic effects.

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What is Etomidate’s most common side effect?
How often does this occur?

Involuntary Myoclonic Movements
that occurs with 50 - 80 % of administrations.

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What should be administered with Etomidate to prevent involuntary myoclonic movements?

Fentanyl 1-2 μg/kg IV

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Etomidate has a dose dependent inhibition of the conversion of cholesterol to _________________.

What does this mean clinically?

Cortisol
Etomidate decreases SNS capability to respond to stress (longer vent times, hypotension, etc.)

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How long does adrenocortical suppression with etomidate last?

4-8 hours.

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What two pathologies would cause you to hesitate before giving Etomidate?

Caution with sepsis and hemorrhage

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Compared to Thiopental, Etomidate will lower plasma concentrations of what substance?

Cortisol

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What are etomidate’s effects on CBF & CMRO₂ ?
Why is this and what does it do?

↓CBF & ↓CMRO₂ 35%-45% due to being
a potent direct cerebral vasoconstrictor.

Will also ↓ICP.

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CMRO₂ is couple with both CBF and _______.

CMRG (cerebral metabolic requirement of glucose)

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What is the EEG profile of etomidate?

- More excitatory than thiopental - May activate seizure foci - Augments SSEP amplitude.

positive side effects of Etomidate

* CV stable * minimal changes in HR, SV, CO, and contractility * No intra-arterial damage

Etomidate results in significant *hypotension* if _________not treated prior to induction?

- Hypovolemia esp. high 0.45 mg/kg IV

Histamine release via etomidate is mediated through what?

- Trick question. **Etomidate does not release histamine**.

What is the pulmonary profile of etomidate?

- **No change in minute ventilation**. d/t increase in respiratory rate compensate decrease in tidal volume - ***Less respiratory depression*** than barbiturates - Rapid IV produces ***apnea*** -***Stimulates CO**₂* medullary centers

What type of drug is ketamine?

- Phenycyclidine derivative; NMDA receptor antagonist (PCP; "angel dust")

What type of anesthesia does Ketamine produce?

Dissociative anesthesia

What two properties does Ketamine possess?

Amnestic & intense analgesia

What signs and symptoms does dissociative anesthesia (ketamine) produce?

**"Zonked" state** - Non-communicative but awake - Hyptonus & purposeful movements - *Cataleptic stat*e: eyes open with a slow nystagmic gaze ("no one's home")

What are Ketamine's two greatest advantages over Propofol or Etomidate?

- No pain at injection (no propylene glycol) - Profound analgesia at sub-anesthetic doses.

What are the two greatest disadvantages of ketamine?

- Emergence delirium - Abuse potential

What is Benzethonium Chloride?

Ketamine preservative that inhibits ACh receptors

Differentiate **S(+)Ketamine** vs **R(-)Ketamine**.

S-Ketamine (left-handed isomer) is essentially better. - More intense analgesia - ↑ metabolism & recovery - Less salivation - Lower emergence delirium

What benefits does a racemic ketamine mixture offer?

- Less fatigue & cognitive impairment - Inhibits catecholamine reuptake at nerve endings (like cocaine).

What is Ketamine's main mechanism of action?

- Non-competitive **inhibition of NMDA** (N-methyl-D-aspartate) receptors by inhibiting pre-synaptic release of **glutamate.** Glutamate is most abundant excitatory NT in CNS

What are Ketamine's secondary receptor sites?

- Weak GABA-A effects. - Opioid (μ, δ, and κ)

What is Ketamine's *time of onse*t? (IV & IM) When would this drug be utilized IM?

- IV: **1 min** - IM: **5 min** (mostly for ***pediatric patients***)

What is Ketamine's duration of action?

10-20 min

What is Ketamine's lipid solubility? What is the result of this?

- **Highly lipid soluble** (5-10x greater than thiopental). - Results: **Brain** →** non plasma bound** → **peripheral tissue**.

What is the Vd of ketamine?

3L/kg (large) ## Footnote S20

What is the Elimination 1/2 time of Ketamine?

2-3 hours

Name the pharmacokinetic profile of ketamine: - Clearance: - Metabolism: - Excretion:

- Clearance: **high hepatic clearance** (1L/min) - Metabolism: **CYP450's** - Excretion: **kidneys** ## Footnote S21

What is the primary metabolite of ketamine and what its its significance?

**Norketamine** is metabolite (⅓ potency and prolongs analgesia). ## Footnote S21

In what patient population is ketamine tolerance most often seen?

Burn patients ## Footnote S21

What is the *induction dose* of ketamine IV? What if it is given intramuscularly?

- 0.5 - 1.5 mg/kg **IV** - 4 - 8 mg/kg **IM** ## Footnote S22

What is the *maintenance dosing* of ketamine?

- 0.2 - 0.5 mg/kg **IV** - 4 - 8 mg/kg **IM** ## Footnote S22

What is the s*ubanesthetic/analgesic dose* of ketamine?

0.2 - 0.5 mg/kg IV ## Footnote S22

What is the *post-operative sedation and analgesia dosing* for ketamine in pediatric cardiac surgery cases?

1-2 mg/kg/**hour** ## Footnote S22

What is the *neuraxial epidural analgesia dosing* of ketamine? What about intrathecal route?

- 30mg **epidural** - 5 - 50 mg via **intrathecal/spinal/subarachnoid** ## Footnote S22

Ketamine is a potent sialagogue. What does this mean for your clinical practice?

- Manage **excessive salivary secretions** during intubation & watch for coughing/laryngospasm.

What *drug and dosing to treat excessive salivary secretions* from ketamine administration?

**Glycopyrrolate: 0.2mg** ## Footnote S23

You gave ketamine and the patient fell asleep within 30 seconds. If you gave no more doses when would you expect the patient to: - Wake up? - Be fully conscious? - Start remembering things?

*- Wake up *in **10-20 minutes** *- Full consciousness* in **60 - 90 min** - Amnestic effects should also *wear off* in **60 - 90 min.** ## Footnote S23

What patient populations is ketamine best used for?

- Acutely hypovolemic patients - Asthmatics - Mental health patients ## Footnote S25

When would you do an IM induction of a patient?

Uncooperative and difficult-to-manage mentally challenged patients. ## Footnote S25

Though ketamine has many indications, when should it be avoided?

- Patients with **pulmonary HTN and ↑ICP**. ## Footnote S26

What are Ketamine's Clinical Uses?

* Burn dressing changes * debridement * skin grafting procedures * Reversal of opioid tolerance * Improvement of psych disorders * Restless leg syndrome ## Footnote S26

What are Ketamine's effects on ICP? Why?

- ↑ICP via ↑CBF by 60% - **Potent cerebral vasodilator**. ## Footnote S27

At what dosing will the ICP increasing effects of ketamine plateau?

2mg/kg IV ## Footnote S27

Due to ketamine's increased excitatory EEG activity, how much does seizure potential increase with administration?

Trick question. **No increase in seizure potential with ketamine**. | Increased amplitude with SSEP is reduced by N20 ## Footnote S27

What does the cardiovascular profile of ketamine look like? How can this side effect profile be blunted?

- SNS stimulation ( ↑ in sBP, PAP, HR, CO, etc.) - Blunted via pre-med with benzo's, volatiles, or nitrous. ## Footnote S28

Say you just gave ketamine and you have an unexpected drop in systolic BP and CO. What happened? How do you treat it?

- *Depleted catecholamine stores* - **Treat with direct-acting SNS agents (ex. phenylephrine)** vs indirect (ex. ephedrine). ## Footnote S28

What is the Pulmonary profile of ketamine?

- No depression of ventilation - CO₂ response maintained. - ↑ salivary excretion - Intact upper airway tone & reflexes. - Bronchodilator with no histamine release. ## Footnote S30

What does emergence delirium present like with ketamine? | aka Psychedelic Effects

- Visual, auditory, proprioceptive illusions. Morbid & vivid dreams up to 24 hours. ## Footnote S31

What is the proposed physiologic mechanism of action for emergence delirium occurrence with ketamine?

Depression of inferior colliculus & medial geniculate nucleus. ## Footnote S31

What percentage of patients will develop ketamine induced emergence delirium? How can it be prevented?

- Psychedelic effects in **5 - 30%** of patients. - **Pre-med with midazolam & glycopyrrolate**. ## Footnote S31

What "other systems" effects does ketamine have?

- Non-depolarizing *NMBs enhancement*. - Succinylcholine prolongation via p*lasma cholinesterase inhibition.* - *PLT aggregation inhibition* ## Footnote S32

What are ketamine's most common drug interactions?

- **Volatiles**→ hypotension - **Non-depolarizing NMBs** → enhancement - **Succinylcholine** → prolongation ## Footnote S33

Why does ketamine prolong succinylcholine's effects?

Ketamine is a plasma cholinesterase inhibitor. ## Footnote S32

Which induction agent has the highest analgesic properties?

- Ketamine ## Footnote S35

Why would ketamine be a decent induction drug for an OSA patient? Why not?

- Preservation of upper airway reflexes & ventilatory function . - Risks: Sialagogue, Psych effects, SNS activation ## Footnote S34

What is Ketafol?

Ketamine and Propofol mix ## Footnote S37

What is combining, admixing, diluting, pooling, reconstituting, repackaging, or otherwise altering a drug or bulk drug substance to create a sterile preparation?

Sterile compounding ## Footnote S37

What are the rules for Pharmaceuctical Compounding?

* Immediate use: **1 hr** to 4 hr **rule** * Single dose * Aseptic process maintained ## Footnote S37

*Induction Drugs (Etomidate & Ketamine) (Exam II) Flashcards

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