Exam 2 Dr. Castillo Key Points Flashcards
What are barbiturates known as in anesthesia?
The gold standard of anesthesia.
How do barbiturates affect GABA-A channel activity?
They potentiate GABA-A channel activity.
What can prolonged infusion of barbiturates lead to?
Lengthy context sensitive half time.
Barbiturates rapidly redistribute from brain to other tissues; VRG to tissues
What are the primary characteristics of thiopental?
- Rapid redistribution (Calculate based on IBW)
- significantly more lipid soluble then oxybarbiturates
What are the side effects associated with methohexital?
Myoclonus, hiccups.
What receptors does propofol act on?
GABA-A receptors to increase chloride conductance.
What is the metabolism pathway for propofol?
CYP450 metabolism.
What is a sub-hypnotic dose of propofol?
10-15mg IV followed by 10 mcg/kg/min.
What is a notable effect of propofol on respiratory resistance?
It acts as a bronchodilator and decreases respiratory resistance.
What happens to cerebral blood flow (CBF) and CMRO2 with large doses of propofol?
Decreases CBF and CMRO2 concurrently (coupled) and large doses may decrease cerebral perfusion pressure
- Make sure to support MAP.
While propofol does not induce seziures, it can cause ___, which might look like a seziure.
myoclonus
Compared to thiopental, what is propofol’s effect on BP?
SBP drop is greater than thiopental’s transient drop.
- Inhibition of SNS leads to vascular smooth muscle relaxation,↓ SVR, and ↓ ICF Ca++.
- Can modulate with laryngoscopy stimulus (cold blade=excitation)
- Hypovolemia is exaggerated in elderly and patients with LV compromise
What other issues occur with the decreases in SNS response after administering propofol?
- BRADYCARDIA
Blackbox warning for profound bradycardia and asystole with healthy adult patients (consider glyco administration before propofo, especiallyif giving to pedi)
Propofol causes a ____-dependent depression of ventilation but leaves patients with a(n) ___ hypoxic pulmonary vasoconstriction response
- dose
- intact
How are liver enzymes typically in patients on propofol?
Intact and creatanine is normal
- Prolonged infusion can cause hepatocellular injury and/or propofol infusion syndrome with NO CHANGE TO CREATININE, even with cloudy urine
What syndrome can prolonged infusion of propofol cause? What is the dosing/timing structure?
Propofol infusion syndrome (lactic acidosis, brady-dysrhythmias, rhabdo.
>75mcg/kg/min for more than 24hrs
- this is reversible in early stages but can lead to cardiogenic shock and require ECMO in later stages
What is a significant risk of propofol infusion syndrome in children?
Fatal bradycardia.
-Pre-treat with glyco to maintain their HR
What are common side effects of etomidate?
- High incidence of myoclonus.
- Pain on injection/venous irritation
Etomidate MOA
Indirectly opens GABA-A receptor Cl- channels
- cell hyperpolarization
How is etomidate metabolized? Excreted? What is the peak effect time for etomidate?
- Metabolized vis hepatic microsomal enzymes and plasma esterases (great for renal/liver patients?)
- Eliminate in urine (85%) and bile (10-13%
- Peaks in 2 minutes.
What is our favorite thing about etomidate? What don’t we like about it?
It is cardiac safe but does not produce analgesia.
What does etomidate suppress?
Stress response
- severe hypotension, use with caution in sepsis and hemorrhage due to need of catecholamines and stress response for bp
Etomidate is a potent cerebral vaso____. This leads to ____ ICP. It can also decrease CBF and CMRO2 by ____%.
- constrictor
- decreased
- 35-45%
What type of pain does ketamine provide?
Profound analgesia (both the drug and the preservative, benzethonium chloride)
- no pain on injection either
What receptors does ketamine bind to?
- Non-competitively to NMDA receptors (decreases glutamate release).
- Also binds to opioid (μ, δ, and κ; weak σ)
- weak action at GABA-A receptors
What is the onset and duration of action for ketamine?
- 1 minute
- 15-20 minutes.
- 60-90min full orientation and amnestic effect
What can be used to manage ketamine-induced salivation?
Glycopyrrolate>atropine
What is the CAD cocktail?
- Diazepam 0.5 mg/kg IV
- Ketamine 0.5 mg/kg IV
- Continuous Ketamine infusion: 15 to 30 μg/kg/minute IV
What are the four processes involved in pain pathways?
- Transduction (Nerve/electrical impulses/signal start at the nerve endings)
- Transmission (Travel of nerve/electrical impulses to the nerve body connecting to the dorsal horn of the spinal cord.)
- Modulation (Process of altering (inhibitory/excitatory) pain transmission mechanisms at the dorsal horn to the PNS and CNS.)
- Perception (Thalamus acting as the central relay station for incoming pain signals & the primary somatosensory cortex serving for discrimination of specific sensory stimuli.)
What is the role of the thalamus in pain perception?
Acts as the central relay station for incoming pain signals.
What types of fibers are involved in nociceptive signaling?
- Unmyelinated - C fibers
- Myelinated - A fibers
What are some chemical mediators involved in pain?
- Peptides (Substance P, Calcitonin, Bradykinin)
- Lipids (Prostaglandins, Thromboxanes, Leukotrienes, Endocannabinoids)
What does the Gate Control Theory describe?
The opening and closing of gates in the spinal cord that affect pain perception.
What types of impulses can modulate pain?
- Excitatory Impulses (Glutamate, Calcitonin, Neuropeptide Y, Aspartate, Substance P)
- Inhibitory Impulse (Glycine, GABA, Enkephalins, Norepinehrine, Dopamine)
What are the types of ascending pathways involved in pain?
- Spinothalamic
- Spinomedullary
- Spinobulbar
- Spinohypothalamic
What is the mechanism of action for opioids?
Presynaptic inhibition of neurotransmitters and increased K conductance.
What is the gold standard of opioids?
Morphine.
What is a significant side effect of opioids?
Constipation.
What is the context-sensitive half-time of fentanyl?
Greater than sufentanil.
What do opioid agonist-antagonists do?
Bind to Mu, kappa, delta receptors with partial effects.
- These partial effects act like an antagonist to other opioids
What is the primary use of buprenorphine?
Post-operative pain management.
What is the effect of multimodal drugs like gabapentin?
Enhances descending inhibition and inhibits excitatory transmitter release.
What are the types of NSAIDs mentioned?
- Non-Specific (Ibuprofen, Naproxen, Aspirin)
- COX-2 selective (Celecoxib, Rofecoxib, Valdecoxib)
What is the effect of magnesium in pain management?
NMDA receptor antagonist.
