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 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
What are the oxybarbituates?
Methohexital
Phemobarbital
Pentobarbital
What are the thiobarbituates?
Thiopental
Thiamylal
Induction dose (IV and per rectum) for Mathohexital (Brevital)?
1.5mg/kg IV
20 - 30 mg/kg rectally
Induction dose for Thiopental?
4mg/kg IV
If a continuous infusion of Brevital is given there can be post-op ____ in 1 out of 3 patients
Seizures
For Propofol, what are the doses for:
1. Induction
2. Maintenance
3. Conscious sedation
4. Sub-hypnotic dose
- Induction = 1.5 - 2.5 mg/kg IV
- Maintenance = 100 - 300 μg/kg/min
- Conscious sedation = 25 - 100 μg/kg/min
- Sub-hypnotic = 10-15 mg IV followed by 10mcg/kg/min
If using propofol as an anti-pruritic, what dose would you give? What about an anti-convulsant?
Anti-pruritic - 10 mg IV
Anti-convulsant - 1 mg/kg IV
Et1/2 of Propofol?
0.5 - 1.5 hrs
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 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
What severe condition(s) can occur with prolonged propofol infusions?
- Hepatocellular injury or Propofol Infusion Syndrome.
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, onset and Et1/2 for etomidate?
- 0.3 mg/kg
- Onset: within 1 min
- Et1/2: 2 - 5 hours
What is the best use for etomidate?
- Induction for unstable cardiac patients.
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.)
Also can have adrenal suppression
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).
What are ketamine’s two greatest advantages over propofol or etomidate?
- No pain at injection (no propylene glycol)
- Analgesia at sub-anesthetic doses.
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 Induction dose (IV and IM), time of onset? (IV & IM)
When would this drug be utilized IM?
- 0.5 - 1.5 mg/kg IV
- 4-8 mg/kg IM
- IV onset: 1 min
- IM onset: 5 min (mostly for pediatric patients)
In what patient population is ketamine tolerance most often seen?
Burn patients
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 post-op sedation and analgesia dose
1 - 2 mg/kg/hr
Ketamine neuraxial analgesia dose…
30 mg - Epidural
5-50 mg in 1mL of NS - Spinal/Intrathecal/Subarachnoid
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 - also a bronchodialator.
- Sialagogue.
What should be administered with etomidate to prevent involuntary myoclonic movements?
Fentanyl 1-2 μg/kg IV
CAD cocktail
Diazepam 0.5 mg/kg IV
Ketamine 0.5 mg/kg IV
Continuous Ketamine Infusion - 15 to 30 mcg/kg/min 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)
