Induction Agents Flashcards
What organs utilize the most blood supply?
What organs utilize the least?
What organs are in between these two groups?
- Vessel-rich group = 75% CP (brain, heart, liver, kidneys)
- Skeletal muscles & skin = 18% CO
- Fat = 5% CO
- Bone, tendons, & cartilage = 2% CO
What are the one-word (ish) summaries of the four stages of anesthesia?
- Analgesia
- Delirium
- Surgical Anesthesia
- Medullary paralysis (death)
What reflexes are we suppressing during stage 1 anesthesia?
If stage 1 anesthesia is maintained, what is it called?
- Coughing, swallowing, and gagging reflexes (lower airway reflexes)
- Conscious sedation
During induction, when would one most likely see laryngospasm?
- Stage 2
During emergence, when would one most likely need to be re-intubated?
- Stage 2
For Propofol, what are the doses for:
1. Induction
2. Maintenance
3. Conscious sedation
- Induction = 1.5 - 2.5 mg/kg IV
- Maintenance = 100 - 300 μg/kg/min
- Conscious sedation = 25 - 100 μg/kg/min
What is the most common concentration of a 1% solution?
- 10mg/mL
What are the inactive ingredients in propofol? Why is one particularly important?
- 1.2% Lecithin (from egg yolks) can cause anaphylaxis with egg allergies.
- 2.25% glycerol
- 10% soybean oil
What are the disadvantages of propofol’s inactive ingredient composition?
- ↑ bacterial growth
- ↑ plasma triglycerides with prolonged infusions
- Pain on injection
What is the mechanism of action of propofol?
- GABA receptor modulator that increases Cl⁻ conductance.
How does propofol cause immobility through spinal cord-depression?
- Trick question. Immobility from propofol is not from drug-induced spinal cord depression.
What are the clearance characteristics of propofol?
The clearance of propofol is primarily through hepatic metabolism, with minor contributions from renal clearance and pulmonary elimination.
What metabolizes propofol?
- CYP450 and UGT1A9
What drug is the induction drug of choice?
Propofol
What is the induction dose of propofol in adults? Children?
- Adults: 1.5-2.5 mg/kg IV
- Pediatrics: higher doses due to larger central volume and clearance rate.
What plasma propofol levels would correlate with unconsciousness?
What about awakening?
- Unconscious: 2 - 6 μg/mL
- Awake: 1 - 1.5 μg/mL
What is the conscious sedation dose of propofol?
- 25 - 100 μg/kg/min
What is the sub-hypnotic dosing for propofol?
- 10 - 15 mg IV, followed by 10 mcg/kg/min
What is the anti-pruritic dosing of propofol?
- 10 mg IV
What are propofol’s effects on CMRO₂, CBF, and ICP?
- ↓ CMRO₂, CBF, and ICP
Large doses of propofol may ______ cerebral perfusion pressure.
decrease
Though propofol will not produce seizures, it will produce _______.
myoclonus
Between thiopental, propofol, and isoflurane, which is the least EEG suppressive?
- Propofol
What severe condition(s) can occur with prolonged propofol infusions?
- Hepatocellular injury or Propofol Infusion Syndrome.
What is the worst side effect in children who have propofol infusion syndrome?
- Severe, refractory, fatal bradycardia
What relatively benign condition(s) can occur from prolonged propofol infusions?
Why does this happen?
Green and cloudy urine from phenols and uric acid crystals.
Neither alters renal function.
What is Propofol Infusion Syndrome?
- Metabolic acidosis thought to occur from poisoning of electron transport chain and impaired oxidation of fatty acids.
What percentage of etomidate is propylene glycol? What is the result of this?
- 35% propylene glycol resulting in pain on injection.
Which induction agent can be given without an IV? How is this?
Etomidate - can be given sub-lingual.
Why does etomidate have a low incidence of myoclonus?
- Trick Question. Etomidate has a high incidence of myoclonus, just like all other induction agents.
What is the induction dosage for etomidate?
- 0.3 mg/kg
What is the best use for etomidate?
- Induction for unstable cardiac patients.
What needs to be used concurrently with etomidate when performing a laryngoscopy? Why?
- Opioids, etomidate has no analgesic effects.
What is Etomidate’s most common side effect?
How often does this occur?
- Involuntary Myoclonic Movements ( 50 - 80 %) of administrations.
- Also PONV (30%)
Etomidate has a dose dependent inhibition of the conversion of cholesterol to _________.
What does this mean clinically?
- Cortisol
- Etomidate decreases SNS capability to respond to stress (longer vent times, hypotension, etc.)
How long does adrenocortical suppression with etomidate last?
What two pathologies would cause you to hesitate before giving etomidate?
- 4-8 hours.
- Sepsis & hemorrhage (anything where you need an intact cortisol response).
Though etomidate is great for cardiac patients, what condition can result in significant hypotension if not treated prior to induction?
- Hypovolemia
Histamine release via etomidate is mediated through what?
- Trick question. Etomidate does not release histamine.
What type of drug is ketamine?
What type of anesthesia does it produce?
What two properties does it possess?
- Phenycyclidine derivative; NMDA receptor antagonist (PCP; “angel dust”)
- Dissociative anesthesia
- Amnestic & intense analgesia
What are ketamine’s two greatest advantages over propofol or etomidate?
- No pain at injection (no propylene glycol)
- Profound analgesia at sub-anesthetic doses.
What signs and symptoms does dissociative anesthesia (ketamine) produce?
“Zonked” state
- Non-communicative but awake
- Hyptonus & purposeful movements
- Eyes open but “no one’s home”.
What are the two greatest disadvantages of ketamine?
- Emergence delirium
- Abuse potential
What is Benzethonium Chloride? What is it’s relevance?
- Ketamine preservative that inhibits ACh receptors
Differentiate S(+)Ketamine vs R(-)Ketamine.
S-Ketamine (left-handed isomer) is essentially better.
- More intense analgesia
- ↑metabolism & recovery
- Less salivation
- Lower emergence delirium
What is Ketamine’s main mechanism of action?
- Non-competitive inhibition of NMDA (N-methyl-D-aspartate) receptors by inhibiting pre-synaptic release of glutamate.
What is Ketamine’s time of onset? (IV & IM)
When would this drug be utilized IM?
- IV: 1 min
- IM: 5 min (mostly for pediatric patients)
In what patient population is ketamine tolerance most often seen?
Burn patients
What is the induction dose of ketamine IV?
- 1.5 mg/kg IV
What is the maintenance dosing of ketamine?
Give both IM and IV dosings.
- 0.2 - 0.5 mg/kg IV
- 4 - 8 mg/kg IM
What is the subanesthetic/analgesic dose of ketamine?
- 0.2 - 0.5 mg/kg IV
Ketamine is a potent sialagogue. What does this mean for your clinical practice?
- Manage excessive secretions during intubation & watch for coughing/laryngospasm.
- Give Glycopyrrolate prior
What “other systems” effects does ketamine have?
- Non-depolarizing NMBs enhancement.
- Succinylcholine prolongation via plasma cholinesterase inhibition.
- PLT aggregation inhibition
Which induction agent has the highest analgesic properties?
- Ketamine
Why would ketamine be a decent induction drug for an OSA patient? Why not?
- Preservation of upper airway reflexes & ventilatory function.
- Sialagogue.
What should be administered with etomidate to prevent involuntary myoclonic movements?
Fentanyl 1-2 μg/kg IV
What drug and dosing of said drug should be used to treat excessive salivary secretions from ketamine administration?
Glycopyrrolate: 0.2mg
Why does ketamine prolong succinylcholine’s effects?
Ketamine is a plasma cholinesterase inhibitor.
What is the induction dose of succinylcholine?
1 - 1.5 mg/kg
What is the induction dose of rocuronium?
0.6 - 1.2 mg/kg
What is the induction dose of cisatracurium, vecuronium, and pancuronium?
0.1 mg/kg
What is the induction dose of Fentanyl?
1.5 - 3 mcg/kg
What is the induction dose of Lidocaine?
1 mg/kg (100 mg max)
