Induction Drugs - Ketamine Exam 2 Flashcards
What type of drug is ketamine?
- Phenycyclidine derivative
- NMDA receptor antagonist (PCP; “angel dust”)
- amnestic and intense analgesic
What type of anesthesia does ketamine produce?
- Dissociative anesthesia (psychedelic)
- cataleptic state
- slow nystagmus
What two properties does ketamine possess?
- Amnestic
- intense analgesia
What signs and symptoms does dissociative anesthesia (ketamine) produce?
- “Zonked” state
- Non-communicative but awake,
- Hypertonus & purposeful movements
- Eyes open but “no one’s home”
What are ketamine’s two greatest advantages over propofol and 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? What is its relevance?
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
which ketamine isomer has cocaine like effects?
Racemic ketamine
inhibits reuptake of catecholamines in nerve endings
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
- decreases pre-synaptic release of glutamate
What are Ketamine’s secondary receptor sites?
- Weak GABA_A effects
- Opioid (Mu μ, Delta δ, and Kappa κ, weak gamma σ)
what is the most abundant excitatory neurotransmitter in the CNS?
Glutamate
What is Ketamine’s time of onset? (IV & IM)
IV: 1 min
IM: 5 min (mostly for pediatric patients)
What is Ketamine’s duration of action?
10-20 min
What about ketamine’s lipid solubility?
Highly lipid soluble (5-10x greater than thiopental)
What is the result of ketamine’s lipid solubility?
Brain → non plasma bound → peripheral tissue
What is the Vd and E½ time of ketamine?
Vd = 3L/kg, E ½ = 2-3 hours
Name the pharmacokinetic profile of ketamine: Clearance, Metabolism, Excretion.
Clearance: high hepatic clearance (1L/min), Metabolism: CYP450’s, Excretion: kidneys
What is the primary metabolite of ketamine and what is its significance?
Norketamine is metabolite (⅓ potency and prolongs analgesia)
In what patient population is ketamine tolerance most often seen?
Burn patients
What is the induction dose of ketamine IV? What if it is given IM?
0.5 - 1.5 mg/kg IV, 4 - 8 mg/kg IM
What is the maintenance dosing of ketamine?
0.2 - 0.5 mg/kg IV, 4 - 8 mg/kg IM
What is the subanesthetic/analgesic dose of ketamine?
0.2 - 0.5 mg/kg IV