IV anesthetics
Terms
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- Thiopental (Pentothal)
-
ultra-short acting barbiturate (induction 10-15 sec.)
highly lipid soluble - distribution of thiopental
- initially distributes into brain well (high blood flow), then redistributes into fatty tissues (accounts for it's rapid but short effects)
- use of thiopental
- used mainly for induction, or very short procedures
- thiopental metabolized by what?
- by P-450 system in the liver
- half-life of thiopental
- 6 hrs
- repeated administration of thiopental will cause?
- will fill the body's storage sites (fats) and can lead to long duration of action
- thiopental : pain threshold
- thiopental lowers pain threshold, thus increasing sensitivity to pain
- Does thiopental have good skeletal muscle relaxtant effects?
- NO! very poor skeletal muscle relaxant effects
- effects of thiopental
-
1) potent resp. depressant - lead to a period of apnea during induction
2) depresses myocardium
3) relaxes vascular smooth muscle - cause hypotension - Methohexital (Brevital)
- similar to thiopental, but 3 times as potent
- metabolism of Methohexital
- metabolized faster (due to less lipid solubility) mainly via P-450 oxidation
- Methohexital
-
1) loss of effect still mainly due to redistribution
2) recovery is faster than thiopental with multiple doses - Propofol (Diprivan) acts by?
- acts by interaction with GABA receptor, decreasing the rate of GABA dissociation from the receptor
- other actions of propofol
-
1) antiemetic
2) antipruritic
3) anticonvulsant - distribution of propofol
-
1) rapidly distributes to brain
2) induction in 15-30 sec. - give slowly due to vessel irritation - termination of anesthesia of propofol is due to?
- redistribution to fatty tissues
- duration of propofol
- 5-10 min.
- metabolization of propofol
-
highly metabolized in liver
half life 2-3 hrs (does not accumulate as much as Thiopental) - propofol
-
1) does not increase pain sensitivity
2) decrease BP due to < CO and < vascular resistance
3) does not trigger malignant hyperthermic crisis - Etomidate (Amidate)
-
1) structure unlike any other anesthetics
2) large Vd (tissue distribution) - mechanism of etomidate
- via GABA interaction like barbs and benzos
- etomidate mixed with?
- propylene glycol for injection
- etomidate is metabolized via?
- via hydroxylation by plasma esterases and HMES
- induction of etomidate
- induction as rapid as Thiopental, with emergence in 5-10 min.
- effects of etomidate
-
1) minimal CV effects
2) resp. depression
3) depresses steroid synthesis in adrenals (not used long term) - Dexmedetomidine (Precedex)
-
1) a novel agent for the control of stress, anxiety, and pain
2) alpha-2 agonist - Dexmedetomidine used with?
- used in combination with agents such as propofol, opioids, and benzo.
- when used Dexmedetomidine alone, it produces what?
- sedation with the ability to rouse the pt
-
Dexmedetomidine
Vd, t1/2, Cl? -
1) Vd = ~118 L
2) t1/2 = ~2hrs
3) Cl = ~39L/hr
administer via continuous IV infusion - metabolism of Dexmedetomidine via
-
1) glucuronidation
2) P450 hydroxylation (dosage adjustment in hepatic dz) - Midazolam (Versed)
-
1) a benzodiazepine with strong hypnotic properties
2) good amnesic
3) minimal CV effects - duration of effects of Midazolam
- 15 min.
- use of Midazolam
-
1) usally used as an adjunct, but it can be used for induction (60 sec.) and maintenance
2) usually used with opioid for longer duration - Ketamine (Ketaject)
-
1) similar to PCP
2) IV or IM
3) rapid induction with IV dudration of ~15 min. - Ketamine stimulates?
-
the CV system: increase HR, CO, and BP
2) good analgesic and amnesic - Ketamine blocks?
- glutamate excitatory NMDA receptors in CNS
- Ketamine triggers?
- catalepsy (dissociation anesthesia), which is the appearance of being awake, even though they do not respond
- recovery from Ketamine
- recovery phase characterized by CNS stimulation, so keep pt. in quiet area