Lecture 12 (Exam 3) - Inhaled Anesthetics II Flashcards
In regards to CNS activity, volatile anesthetics decrease what two things?
CMRO2 and cerebral activity
Slide 15
The dose-dependent decrease in CMRO2 and cerebral activity associated with inhaled anesthetics begins at approximately what MAC value?
0.4 MAC
Slide 15
Burst suppression occurs at what MAC? What about electrical silence?
Burst Suppression = 1.5 MAC
Electrical Silence = 2 MAC
Slide 15
Which inhaled anesthetic decreases CMRO2 and cerebral activity the most?
Trick question
Isoflurane = Sevoflurane = Desflurane
Slide 15
Which inhaled anesthetic has proconvulsant activity?
Enflurane - Especially above 2 MAC or PaCO2 < 30 mmHg
Slide 16
What is it called when we stimulate the periphery and measure the response in the brain, evaluating transmission UP the spinal cord?
Somatosensory Evoked Potentials (SSEPs)
Slide 16
What is it called when we stimulate the brain and measuring the response in the periphery, evaluating transmission DOWN the spinal cord?
Motor Evoked Potentials (MEPs)
Slide 16
Inhaled anesthetics have a dose-related __________ in amplitude and ____________ latency of evoked potentials at values of 0.5-1.5 MAC
Decrease amplitude
Increase latency (Occur less frequently)
Slide 16
How do inhaled anesthetics affect cerebral blood flow?
Increase cerebral blood flow due to decreased cerebral vascular resistance - Leads to increased ICP
Slide 17
Dose-dependent increases in cerebral blood flow occur at what MAC value?
> 0.6 MAC
Slide 17
Which volatile has less vasodilatory effects, leading to less cerebral blood flow increases?
Sevoflurane
Slide 17
Which volatile has the worst increase in cerebral blood flow and should definitely NOT be used in patients with increased ICP?
Halothane
Slide 17
Per lecture, autoregulation is normally good between what values?
60-160 mmHg
Slide 18
Autoregulation is lost with the use of Halothane by what MAC value?
0.5 MAC
Slide 18
Sevo preserves autoregulation up until ____ MAC?
1 MAC
Slide 18
Increases in _____ parallels increases in CBF?
ICP
Slide 19
Increases in ICP are opposed by what?
Hyperventilation
Slide 19
Typically, ICP increases occur at MAC values > 0.8 MAC and increase by how much?
7 mmHg
Slide 19
Who is more at risk for increases in ICP when administering volatile anesthetics?
Patients with space-occupying lesions or tumors
Apnea occurs at _________ MAC
1.5-2.0 MAC
Slide 20
Volatile anesthetics produce a dose-dependent __________ in respiratory rate and ___________ in tidal volume
Increased rate
Decreased tidal volume
Slide 20
Inhaled anesthetics not only depress the medullary ventilatory center but also interfere with…
Intercostal muscles - They lose their coordination
Slide 20
True or False?
The rate change associated with inhaled anesthetics is insufficient to maintain minute ventilation or PaCO2
True
Slide 20
The price of anesthetics are based on what 3 things?
- Cost of liquid/mL
- Volume % of anesthetic delivered (based on potency)
- FGF rate (high vs low rate of fresh gas flow)
(slide 8)
Is Desflurane 6.6% or Sevoflurane 1.8% more potent?
Sevo
(slide 8)
Is Ethrane used anymore in the US?
nope
(slide 9)
Volatile Anesthetics cause Bronchodilation by how?
And what is required for optimal bronchodilation?
By blocking voltage-gated Ca++ channels and depleting ca++ in SR
Requires intact epithelium (so any conditions with inflammatory processes or epithelial damages can alter the bronchodilation effects- i.e. Astham pts)
(slide 10)
To have bronchodilation with inhaled anesthetics without bronchospasms due to:
- Baseline Pulmonary resistance unchanged by 1-2 MAC
- Need histamine release or vagal afferent stimulation… (idk what this means and couldn’t find a good answer in the book)
(slide 10)
Risk factors for Bronchospasm with inhaled anesthetics include: (4)
And which anesthetic drug can cause bronchospasm?
- COPD
- cough response with ETT
- Age <10
- URI (upper resp infection)
Desflurane may worsen bronchospasm (esp. in smokers due to pungency/irritation)
(slide 10)
Is Sevoflurane or Isoflurane better at causing bronchodilation?
Sevoflurane
(slide 10)
Which inhaled anesthetic is BEST at bronchodilation but is not used anymore in US?
Halothane
(slide 10)
For respiratory resistance comparison, Which inhaled drug would be worst to give and which drug is best?
worst= Desflurane
best= sevoflurane > Isoflurane
(slide 11- diagram)
Neuromuscular wise, does inhaled anesthetics cause muscle relaxation? And what is it dependant upon?
Yes! But dose-dependant
(slide 12)
Inhaled Anesthetics potentiate depolarizing and nondepolarizing NMBDs how?
Through the nACh receptors at the NMJ
They enhance **glycine **(an inhibitory NT) at the spinal cord
(slide 12)
Does Nitrous Oxide have any relaxant effects on skeletal muscle?
NOPE!
(slide 12)
What is “ischemic preconditioning” with inhaled anesthetics?
“Brief episodes of myocardial ischemia occurring before a subsequent longer period of myocardial ischemia providing protection against myocardial dysfunction and necrosis”-pg. 273
Per Dr. Kane: “the heart recognizes brief periods of ischemia before it is subjected to a longer period of ischemia, it can set itself up for that long period to be less of an effect”
(slide 13)
What is the MOA towards “Ischemic preconditioning” with inhaled anesthetics?
Mediated by adenosine
- Increases protein kinase C activity
- Phosphorylates ATP sensitive K+ channels
- Production of reactive oxygen species (ROS)
end result: Better regulates vascular tone
(slide 13)
“Ischemic preconditioning” with inhaled anesthetics can occur as low as what MAC?
Also, this helps to prevent “reperfusion injury how?
0.25 MAC (so very low) - (So just a little exposure of the volatile anesthetic during this brief ischemic period, can help the heart be resistant (or not as susceptible) during those long ischemic periods)
(slide 13)
“Ischemic preconditioning” with inhaled anesthetics helps prevent “reperfusion Injury.” What would these be?
What procedures is this best used in?
- Cardiac dysrhythmias
- Contractile dysfunction
Clinically apparent in delaying MI for: PTCA, CABG
(giving the VA during these times can help pre-condition the heart)
(slide 13)
What kind of effect does VA have on Cardiac output?
Dose-dependent ↓ in CO offsets by mild ↑ in HR
(↓ CO is also due to ↓ SVR)
Slide 26
What kind of cardiac effect do you see in Nitrous?
Sympathomimetic, we will see mild increase in CO if we just give nitrous.
Slide 26
Some study suggests VA can cause _______ d/t coronary vasodilation.
Coronary steal
Slide 26
What kind of vessels does coronary steal occur?
Preferentially in 20-50 micrometer vessels
(not clinically significant)
Slide 26
What kind of cardiac dysrhythmias does VA cause?
Prolonged QT with potential risk of Torsades.
(with inhibition of K+ current)
Slide 27
Nitrous has ______proarrhythmic effect.
minimal
Slide 27