Induction Meds: Ketamine Flashcards
What type of drug is ketamine?
- Phenycyclidine derivative;
NMDA receptor antagonist (PCP; “angel dust”)
What signs and symptoms does dissociative anesthesia (ketamine) produce?
“Zonked” state
- Non-communicative but awake
- Hyptonus & purposeful movements
- Cataleptic state: 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 onset? (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 the Vd of ketamine?
3L/kg (large)
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Name the pharmacokinetic profile of ketamine:
- Clearance:
- Metabolism:
- Excretion:
- Clearance: high hepatic clearance (1L/min)
- Metabolism: CYP450’s
- Excretion: kidneys
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What is the primary metabolite of ketamine and what its its significance?
Norketamine is metabolite (⅓ potency and prolongs analgesia).
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In what patient population is ketamine tolerance most often seen?
Burn patients
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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
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What is the maintenance dosing of ketamine?
- 0.2 - 0.5 mg/kg IV
- 4 - 8 mg/kg IM
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What is the subanesthetic/analgesic dose of ketamine?
0.2 - 0.5 mg/kg IV
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What is the post-operative sedation and analgesia dosing for ketamine in pediatric cardiac surgery cases?
1-2 mg/kg/hour
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What is the neuraxial epidural analgesia dosing of ketamine?
What about intrathecal route?
- 30mg epidural
- 5 - 50 mg via intrathecal/spinal/subarachnoid
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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
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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.
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What patient populations is ketamine best used for?
- Acutely hypovolemic patients
- Asthmatics
- Mental health patients
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When would you do an IM induction of a patient?
Uncooperative and difficult-to-manage mentally challenged patients.
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Though ketamine has many indications, when should it be avoided?
- Patients with pulmonary HTN and ↑ICP.
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What are Ketamine’s effects on ICP? Why?
- ↑ICP via ↑CBF by 60%
- Potent cerebral vasodilator.
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At what dosing will the ICP increasing effects of ketamine plateau?
2mg/kg IV
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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
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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.
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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).
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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.
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What does emergence delirium present like with ketamine?
aka Psychedelic Effects
- Visual, auditory, proprioceptive illusions. Morbid & vivid dreams up to 24 hours.
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What is the proposed physiologic mechanism of action for emergence delirium occurrence with ketamine?
Depression of inferior colliculus & medial geniculate nucleus.
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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.
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What “other systems” effects does ketamine have?
- Non-depolarizing NMBs enhancement.
- Succinylcholine prolongation via plasma cholinesterase inhibition.
- PLT aggregation inhibition
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What are ketamine’s most common drug interactions?
- Volatiles→ hypotension
- Non-depolarizing NMBs → enhancement
- Succinylcholine → prolongation
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Why does ketamine prolong succinylcholine’s effects?
Ketamine is a plasma cholinesterase inhibitor.
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Which induction agent has the highest analgesic properties?
- Ketamine
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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
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What type of anesthesia does Ketamine produce?
Dissociative anesthesia
What two properties does Ketamine possess?
Amnestic & intense analgesia
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 Elimination 1/2 time of Ketamine?
2-3 hours
What are Ketamine’s Clinical Uses?
- Burn dressing changes
- debridement
- skin grafting procedures
- Reversal of opioid tolerance
- Improvement of psych disorders
- Restless leg syndrome
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