Barbiturates Flashcards
(42 cards)
Do Barbiturates cause areflexia?
No! Little to no effects on any muscles
Name the uses of barbiturates (6)
Seizure treatment, short painless procedures, induction, increased ICP, cardio version, ECT
What determines the effects of the barbiturates?
The molecule substitutions
Do oxybarbiturates have a long or short duration of action?
Long
Comment on thiobarbiturates lipophilicity, onset, duration of action
Lipophilic, rapid onset, shorter DOA
Methohexital has a longer or shorter DOA?
shorter
Phenobarbital has what key use?
Anticonvulsant
Which 4 receptors can barbiturates act on? What is the primary receptor?
GABA (primary), adenosine, nicotinic Ach, glutamate
Are barbiturates appropriate in patients with increased ICP?
Yes - decrease CBV, CBF, CMRO2, and ICP. Neuroprotective due to reverse steal (ischemic areas still get BF), free radical scavenging, liposomal membrane stabilizing, excitatory amino acid blockade
Dose required may cause significant hypotension
Contraindication of barbiturates? Why?
Acute intermittent porphyria
due to accelerated heme production
What happens and what do you do if a barbiturate is accidentally administered into an artery?
Area vasoconstricts -> blanching -> cyanosis -> gangrene -> necrosis -> permanent nerve damage
Dilute with lidocaine, give heparin, give papaverine, peripheral nerve block
Are barbiturates lipophilic?
Yes - rapid distribution, rapid termination after re-distribution
Do barbiturates undergo phase I or phase II metabolism?
Phase I - liver oxidation
Why is thiopental’s half life ten fold of that of propofol?
Thiopental has an active metabolite - pentobarbital (oxybarbiturate) - that is very long-acting
In what patients would half-time of barbiturates be affected?
Pediatrics - shorter half-time due to rapid hepatic clearance
Pregnancy - longer-half time due to protein binding
Do barbiturates cause pain on injection?
No - no additives
Do barbiturates cause an isoelectric EEG?
Yes - burst suppression
What are the CV effects of barbiturates?
Decreased SVR, MAP, CO, direct myocardial depression
What are the respiratory effects of barbiturates?
Cause central apnea (1 min) with return to baseline in 6 minutes which is shorter than with prop
some anti-bronchospastic effects with thiopental, but not as much as with prop
not as much bronchodilaton (airway reflexes maintained)
large doses can depress laryngeal/cough reflexes
Dose dependent depression of medullary and pontine ventilatory centers
Enzyme induction from which barbiturate causes accelerated metabolism of which other drugs?
Phenobarbital.
Causes accelerated metabolism of tricyclics, anticoagulants, phenytoin, endogenous substances (vitamin K, bile salts, corticosteroids)
What are the 4 stages of anesthesia that are produced with the induction of IV anesthetics?
There are no 4 stages with induction of IV anesthetics
Is thiopental used for long-term sedation?
Not commonly - accumulation, prolonged half time, slow recovery
How are the effects of thiopental terminated?
Very lipophilic - fast onset - quick re-distribution*
What is thiopental’s hepatocyte? Does it cross the BBB?
hydroxythiopental - no, it is water soluble so it can be really excreted quickly
