Intravenous anesthetics 2 Flashcards
Ketamine: (select 3)
a. causes emergence delirium
b. agonizes the N-methyl-D-aspartate receptor
c. relieves somatic pain
d. increases the risk of depression
e. increases the cerebral metabolic rate of oxygen consumption
f. promotes bronchoconstriction
a. causes emergence delirium
c. relieves somatic pain
e. increases the cerebral metabolic rate of oxygen consumption
What is the primary mechanism of action of ketamine?
NMDA antagonist (creates a dissociated state)
What is the secondary mechanism of action of ketamine?
many secondary receptor targets including opioid, MAO, serotonin, NE, muscarinic, and Na+ channels
What is the onset of IV ketamine?
30-60 seconds
What is the onset of IM ketamine?
2-4 minutes
What is the onset of PO ketamine?
variable
What is the duration of action of ketamine?
10-20 minutes (may require 60-90 minutes to return to full orientation
What is the clearance of ketamine?
liver
What is the active metabolite of ketamine?
norketamine
What is the IV, IM, and PO induction doses of ketamine?
IV: 1-2 mg/kg
IM: 4-8 mg/kg
PO: 10 mg/kg
What is the opioid sparing dose of ketamine?
0.1-0.5 mg/kg or 1-3 mcg/kg/min.
What are the respiratory effects of ketamine?
maintains respiratory drive, increased oral secretions, bronchial dilation
What are the CV effects of ketamine?
Increased SNS tone, SVR, HR, and Cardiac output
increased pulmonary vascular resistance
What are the CNS effects of ketamine?
increased ICP, IOP, nystagmus, and analgesia
also causes emergence delirium & lowers the seizure threshold
Subhypnotic doses of ketamine may be used to
treat severe depression
Ketamine should be avoided with
acute intermittent porphyria
What is the pKa of ketamine?
7.5
Ketamine works by
dissociating the thalamus (sensory) from the limbic system (awareness)
Chronic ketamine use _______ the enzymes that metabolize it
induces
Ketamine is excreted via the
renal system
Because ketamine increases the SNS tone it is useful in ______ but harmful in
useful if the patient is hemodynamically unstable but harmful if severe CAD
Ketamine is a ________ myocardial depressant. The CV effects require an
direct; intact SNS
The myocardial depressant effects of ketamine will be unmasked in patients with
depleted catecholamine stores (sepsis) or sympathectomy
How does ketamine affect the CO2 response curve?
it does not significantly shift it
Emergence delirium presents as
nightmares and hallucinations
_______ are the most effective way to prevent emergence delirium
benzodiazepines
Risk factors for emergence delirium include
age >15 years, female gender, ketamine dose >2 mg/kg and hx of personality disorder
What kind of pain is ketamine good for?
somatic> visceral pain
The analgesic properties of ketamine make it good for
burn patients (frequent dressing changes) and those with pre-existing chronic pain syndromes
Chronic ketamine can cause
ulcerative cystitis
The S enantiomer (esketamine) is marketed as a nasal spray that’s indicated for
treatment-resistant depression in adults as well as depressive symptoms in adults with major depressive disorder with acute suicidal ideation or behavior
Describe ketamines protein binding.
smallest amount of plasma protein binding as compared to the other induction agents at 12%
Central nervous system effects of etomidate include (select 2):
a. cerebral vasodilation
b. myoclonus
c. analgesia
d. decreased intracranial pressure
b. myoclonus
d. decreased intracranial pressure
The mechanism of action of etomidate is
GABA-A agonist
The onset of action of etomidate is
30-60 seconds
The duration of action of etomidate is
5-15 minutes
The clearance of etomidate is
liver + plasma esterases
The active metabolite of etomidate is
none
The induction dose of etomidate is:
0.2-0.4 mg/kg IV
The respiratory effects of etomidate include
mild respiratory depression
The CV effects of etomidate include
minimal- cardiac stability
SVR is decreased which accounts for a small reduction in BP
The CNS effects of etomidate include
decreased ICP
decreased CMRO2
decreased CBF
no analgesia
Rapid awakening with etomidate is due to
redistribution (NOT metabolism)
Etomidate does not block the SNS response to
laryngoscopy; should consider an opioid or esmolol
Which anesthetic agent increases mortality in the patient with Addisonian crisis?
a. etomidate
b. propofol
c. dexmedetomidine
d. midazolam
a. etomidate
A single dose of etomidate suppresses adrenocortical function for
5-8 hours (some books say up to 24 hours)
Etomidate is a known inhibitor of
11-beta-hydroxylase
17-alpha-hydroxylase
Key side effects of etomidate include:
myoclonus (this is not a seizure)
etomidate does not cause seizures if the patient does not have a hx. of seizures
suppression of adrenocortical function for up to 24 hours
nausea & vomiting (greater than any other induction agent)
acute intermittent porphyria
