Lecture 5 Induction: Barbiturates and Propofol Test 2 Flashcards
A drug that induces a state of calm or sleep.
Sedative
A drug that induces hypnosis or sleep.
Hypnotic
A drug that reduces anxiety and that has sedation as a side effect.
Anxiolytic
A drug that reversibly depresses the activity of the CNS.
Sedative-Hypnotics
State of drug-induced unconsciousness.
General Anesthesia
What is MAC?
Monitored Anesthesia Care- administration of a combination of sedatives and analgesics to induce a depressed level of consciousness, allowing patients to tolerate unpleasant procedures and enabling clinicians to perform procedures effectively.
AKA Procedure Sedation/ Conscious Sedation
What four groups will medication be distributed to?
What is the CO% of each group?
Vessel rich group (75%)
Muscle group (18%)
Fat (5%)
Vessel poor group (2%)
What makes up the Vessel-rich group?
Brain
Heart
Kidney
Liver
What makes up the Muscle group?
Skeletal muscle
Skin
What makes up the Vessel-poor group?
Bone
Tendon
Cartilage
What are the 5 components of General Anesthesia?
Hypnosis
Analgesia
Muscle Relaxation
Sympatholysis (hemodynamic stability)
Amnesia
What are the 4 stages of General Anesthesia?
Stage 1: Analgesia
Stage 2: Delirium
Stage 3: Surgical Anesthesia
Stage 4: Medullary Paralysis
What stage can cause death?
Stage 4
What stage consist of the lightest level of anesthesia?
Stage 1
(This is the stage of conscious sedation, the patient can still open their eyes on command, breathe normally, and protective reflexes maintained.)
Stage 1 begins with the initiation of an anesthetic agent and ends with ___________.
The patient will experience __________ and _________ depression.
Loss of consciousness
Sensory and mental
What are the 3 lower airway reflexes?
Coughing
Gagging
Swallowing
What is the upper airway reflex?
Sneezing
Stage 2 starts with the loss of consciousness to the onset of automatic rhythmicity of vital signs. This stage is characterized by excitement in what areas?
Undesired CV instability excitation
Dysconjugate ocular movements
Laryngospasm
Emesis.
What is the response to stimulation in Stage 2 like?
Exaggerated and violent
What stage will have an absence of response to surgical incision and depression in all elements of the nervous system?
Stage 3
Will have all 5 components of anesthesia hypnosis, analgesia, muscle relaxation, sympatholysis, and amnesia
What stage is associated with cessation of spontaneous respiration and medullary cardiac reflex? What are the symptoms of this stage?
Stage 4 (over anesthesia)
All reflexes are absent
Flaccid Paralysis
Marked Hypotension with w/ irregular pulse.
May lead to death
How can you tell if a patient is out from stage 2 to stage 1 for an awake extubation?
Patient is about to follow commands
What is the benefit of using a barbiturate (thiopental) vs. diethyl ether?
Diethyl ether is slow, unpleasant, and more dangerous for induction of general anesthesia. Barbiturates can cover stages 1 to stage 3 in as little as 2 minutes.
Why are barbiturates no longer used in the U.S.?
Thiopental is now part of the lethal injection cocktail for capital punishment.
Why are we still talking about barbiturates?
This drug is still used in other countries.
Critical to understand properties of barbiturates (gold standard) as comparison with other drugs.
What is the MOA of Barbituates?
Potentiates GABA-A channel activity; directly mimics GABA.
Acts on glutamate, adenosine, and neuronal nicotinic acetylcholine receptors
Barbiturates are a cerebral _____________.
What will be the effect on CBF?
What will be the effect on CMRO2?
Cerebral vasoconstrictor
CBF decreases
CMRO2 decreases by 55%
How do barbiturates help with seizures?
The decrease in CBF and CMRO2 will decrease the metabolic activity of the brain
Do barbiturates cause analgesic effects?
No Analgesia
What is the onset time of barbiturates?
Barbiturates have a rapid redistribution at 5 minutes __________ of the total dose in the blood.
How much of the total dose will be in the blood after 30 minutes?
30 seconds
50%
10%
What will result from a prolonged infusion time of barbiturates?
Lengthy context-sensitive half-time
Where is thiopental rapidly distributed to?
The rate of metabolism of thiopental is equal to what?
Thiopental goes to the brain and viscera in about 1 minute.
Metabolism of thiopental is equal to thiopental accumulation in the fat.
During emergence, the medication that was stored in the _________ and __________ will be reabsorbed in the blood and affect mentation.
fat and lean tissues
What is the site of the initial redistribution for barbiturates?
Equilibrium at __________ minutes to plasma.
When will perfusion decrease?
Who has mass decrease?
Skeletal muscles
15 minutes
Perfusion decrease d/t shock
The elderly will have a mass decrease
Why is the context-sensitive half-time for barbituates so long?
The fat is a reservoir site for the drug, redosing/large dosing will yield cumulative effects.
Usually, barbituates are dosed on ________ body weight.
lean
How are Barbituates metabolized?
How are they excreted?
Elimination half-time consideration for pediatrics?
Hepatocytes 99%
Renal
Shorter half-time (higher metabolism)
Protein binding percentage of barbiturates?
Is the barbiturate active or inactive?
Binds to albumin 70 to 85%
Inactive, most of the drug will be bound to the protein. Once the drug becomes unbound and goes the VRG and crosses the BBB, that is when the drug will affect mentation.
When the barbiturate is non-ionized it will be ____________ soluble and _________ favors.
more lipid soluble and acidosis favors
Wants to stay in muscle and fat
When the barbiturate is ionized, it will be _________ soluble and _________ favors.
less lipid soluble and alkalosis favors
What are previous uses of barbiturates?
Premedication for Hangover
Grand mal seizures (now uses benzos)
Rectal administration with uncooperative/young patients
Increased ICP, cerebral protection
Induction
___ isomer is much more potent than ________ isomer, but the barbiturates are only marketed as _________ mixtures.
S- isomer
R- isomer
Racemic Mixture
What are examples of oxybarbiturates?
Methohexital
Phenobarbital
Pentobarbital
What are examples of thiobarbiturates?
Thiopental
Thiamylal