ketamine Flashcards
(30 cards)
what is the classification of ketamine?
- dissociative
- non-barbiturate IV anesthetic
- disconnects brain from body; hallucinations
who can ketamine not be given to r/t job?
public transport personnel (pilots, bus drivers, etc.) d/t possible reoccurrence of symptoms, may be barred from job
what is the MOA of ketamine?
- binds non-competitively to N-methyl-D-aspartate (NMDA) receptors
- exert some effect on opioid receptors
what is the onset of ketamine?
- rapid, similar to thiopental
- within 1 min (30-60 sec) of IV injection, less than 5 min (2-4 min) IM
what is the duration of ketamine?
- short, similar to thiopental
- larger doses take longer to wear off
how does ketamine cross the BBB?
- rapid transfer across, greater than thiopental (4-5x faster)
- reason it is such a quick dissociative
what patients are more at risk for side effects of ketamine?
- < 15 y/o (kids already have nightmares)
- female (tend to have more vivid dreams)
- doses > 2 mg/kg
- history of frequent dreams/nightmares
- don’t give to PTSD
- don’t give to pts. with mental disorders with hallucinations (schizophrenia)
what drugs help reduce side effects of ketamine?
benzodiazepines reduce emergence delirium and increase seizure threshold
- midazolam
- diazepam
- lorazepam
what is observed with ketamine effects?
- open eyes (glazed over)
- behavior like catatonic state (seem really high)
- nystagmus (eye twitching)
- may move with no regard to surgical stimulation
- amnesia
- pain free
- 1.4 in 100,000 have bradycardia related death (glycopyrrolate and versed lessens)
- oculocardiac reflex is enhanced (certain nerves cause vagal decrease in HR, so pre treatment helps)
describe emergence delirium with ketamine
- 5-30% incidence
- visual, auditory, proprioceptive and confusing illusions/hallucinations
- dreams can occur up to 24 hrs after administration
- central misinterpretation of visual and verbal stimuli
- pt. may be combative
- pad bed, surrounding
- recover in quiet environment; not regular PACU
- abuse potential
what are anticholinergic effects of ketamine at muscarinic receptors?
- delirium
- bronchodilation
- sympathomimetic action
- give glycopyrrolate
what is action of ketamine terminated and how is it eliminated?
- redistributed form the brain to tissues that are highly perfused
- high hepatic clearance that prolongs elimination 1/2 life as much as 2-3 hrs (less than 4% excreted renally)
- chronic administration stimulates CP450
how is ketamine metabolized?
- hepatic microsomal enzymes
- CP450
- active metabolite: Norketamine
- liver disease not a good candidate for ketamine
what pts. may require an increased dose of ketamine?
pts. with induced CP450
- alcoholics
- smokers
- drug abusers
describe Norketamine
- active metabolite of ketamine
- onlyu 1/5 to 1/3 as potent
- provides analgesia
- contributes to prolonged analgesic effect of ketamine
what are clinical uses of ketamine for analgesia?
- unique drug that provides wonderful analgesia at subanesthetic doses
- provides prompt induction of anesthesia at higher doses
- hip fracture or replacement and need to do a spinal: hurts to sit up; 30-40mg ketamine allows to sit up to place spinal
- give antisialogogue like glycopyrrolate since atropine and scopolamine may cause emergence delirium also
describe ketamine use for analgesia
- intense analgesia can be accomplished with subanesthetic doses
- works in the thalamic and limbic systems to inhibit interpretation of painful stimuli
- used in conjunction with opioids as an adjuvant
what is the analgesic dose of ketamine?
0.2-0.5 mg/kg
when should ketamine be used in OB?
- emergent use only! (there is no time for an epidural, spinal, or other inductions and need to get baby out quick!)
- not good use in OB but better than thiopental
- neurobehavioral scores of infants born by vaginal delivery are lower with ketamine than those born with epidural anesthesia (crosses placental barrier)
what are neuraxial effects of ketamine?
- limited efficacy
- extradural dosages may be as weak as 10,000 fold weaker than morphine
- has additive or synergistic effect when given with opioids neuraxially (can give less opioid)
what are induction doses of ketamine?
IV: 1-4.5 mg/kg (avg. 2-3 mg/kg)
IM: 3-5 mg/kg OR 6-8 mg/kg
*0.25-1.0 mg produces minimal to mild effects
what should be considered with dosing and onset of ketamine in elderly?
- require lower induction mg d/t smaller central distribution volume
- allow for circulation time (onset may be slower)
what dose is typically used for maintenance after induction with ketamine?
half the initial dose usually every 10-20 min
when is ketamine especially good to use?
- induction of severely hypovolemic pts.
* CV stimulation (increased BP, HR, CO)
