Inhalation II Flashcards
This IA can suppress baroreceptors.
If you supress baroreceptors what can happen?
N2O suppresses baroreceptors and this in turn can attenuate the HR response to hypotension.
What is the MAC of SEVO when we can see a decrease in HR?
HR decreases with Sevo <1.5 MAC
VA that slows SA discharge and prolongs ventricular conduction time
ISOFLURANE
IA that you may opt to avoid in patients with pulmonary hypertension due to its effect on pulmonary vascular resistance
NITROUS OXIDE
- N2O produces increased RAP
- This reflects increases in pulmonary vascular resistance
- Some prefer to avoid N2O in patients with pulmonary hypertension
- produces modestly increased CO
- This represents a mild sympathomimetic effect
- N2O produces a cardiac depression which is offset by this sympathomimetic effect
What can happen if you overpressure desflurane?
rapid rise in HR can be observed
–>Rapid increase in desflurane rapid increase in HR, MAP, and nerve activity (due to SNS activity)
This VA should be avoided in patients with congenital prolonged QT syndrome
SEVOFLURANE
- i.All IAs prolong the QT
- ii.Sevo should be avoided in patients with congenital prolonged QT syndrome
- Sevo could prolong even more if they already have prolonged QT
- Increased risk for R on T
Arrange the VA according to their effects on CMRO2 AND CBF
Iso, Sevo, Des decrease CMRO2 and increase CBF
- Iso > Sevo > Des
How can the increase of ICP be attenuated?
Increases in ICP parallel increases in CBF, dose-dependent
Offset with hyperventilation
When do you see increase in ICP with deflurane?
Desflurane does not increase ICP at <0.8 MAC, starts at > 1.1 MAC
All volatiles increase ICP at concentrations exceeding 1 MAC
When is autoregulation impaired?
Autoregulation is lost with volatiles at > 1 MAC
- Once MAPs >150, your brain can’t regulate so as BP increases CBF increases
- However cerebrovascular response to PaCO2 is maintained
What are the effects of IA on evoked potentials?
All IAs depresses amplitude and increase latency of SSEPs (and AEPs) in a dose-dependent manner
Makes it hard to interpret SSEPs
Signals are depressed
When can you abolish EP?
1 MAC
–>Low concentrations of volatiles reduce the reliability of MEPs
Often TIVA with Propofol and opioid(s) is used when SSEPs and/or MEPs are employed.
What is the effect of Nitrous on evoke potentials?
N20 decreases amplitude
What are the effects of volatiles on EEG?
Volatiles cause dose-dependent EEG changes
- <0.4 MAC: increases in voltage and frequency
- ~0.4 MAC: amnesia occurs, CMRO2 begins to decrease
- 1 MAC: decreased frequency, max voltage achieved
- Iso** produces **burst suppression at 1.5 MAC, isoelectric EEG at 2 MAC
- Increased amplitude
- Burst suppression at concentrations exceeding 1.5 MAC
VA that has anticonvulsant property
VA that is epileptogenic
- Iso has anticonvulsant properties
- Enf > Sevo are epileptogenic
What effect does VA have of NDMRs?
how about N2O?
i.Volatile anesthetics produce dose-dependent skeletal muscle relaxation
ii.Volatiles potentiate NDMRs (and DMR)
Des potentiates roc more than sevo or iso
N2O does not enhance NMBAs
iii.N2O produces skeletal muscle rigidity at high concentrations
Severe hepatic injury may occur in Iso and Des why?
Hepatic injury may be mild or severe (Iso and Des)
- Involves hepatic necrosis and is immunologic in origin
- CYP 450 metabolism of these agents results in trifluoroacetate which binds covalently to hepatocytes
- The trifluoroacetate-hepatocyte complex triggers an immune response –> hepatic necrosis
The effects of N20 on bone marrow
- Prolonged administration (>24 hours) of N2O causes megaloblastic changes and agranulocytosis
- Interference with activity of Vit B12 dependent enzymes, that are necessary for the synthesis of DNA and formation of erythrocytes
What produces carbon monoxide?
Carbon Monoxide
- Produced during degradation by *CO2 absorbents*
- Des > Enf > Iso
- Hard to detect intraoperatively, because carbon monoxide binds to iron
- Increases CO2 production
What are the factors that increase CO2 production/ carbon monoxide?
Increases CO2 production
- If the CO2 absorbent in the system is dry, that would accelerate the production of carbon monoxide
- If the temp of the CO2 absorbent is high = increase carbon monoxide
- Low gas flows = increase carbon monoxide
- Increased metabolic production of CO2 = increase carbon monoxide
- High gas flows for long period of time = dryness/desiccation of CO2 absorbed = increase carbon monoxide
- Different brands of absorber can affect amount of carbon monoxide produced
