Ex2 IA System Effects Flashcards
Effect on MAP
IAs:
Dose-dependent decrease (increasing concentrations)
N2O: no change or increase
N2O + Iso = less of a decrease in BP
Effect on HR
Iso/Des: dose dependent increase
Sevo at <1.5 MAC: decrease; >2 = normal
Effect on rhythm
Prolonged QT
Sevo should be avoided in prolonged QT
Effect on ventilation
Dose dependent depression of ventilation (Dec. response to increased CO2/decreasedO2)
Shallow breathing, increased rate, Bronchodilation
Inhibit HPV (esp > 1-2 MAC)
HPV
Hypoxic Pulmonary Vasoconstriction
Effect on chest wall
Decreased FRC, atelectasis in dependent areas
Effect on CNS
N2O: increased CBF, modest increase in CMRO2
IAs: decreased CMRO2, increased CBF
All volatiles cause a cerebral ______ in a dose dependent manner
dilation
All volatiles _______ ICP at concentrations exceeding _____ MAC
increase; 1 MAC
What is impaired at concentrations > 1 MAC?
Autoregulation
Cerebrovascular response to ______ is maintained
PaCO2
Which type of procedure would avoid IAs?
Spinal
CNS Effects
Dose dependent depression of amplitude/increase latency of SSEPs (& AEPs)
EPs may be abolished at _____ MAC
1
At what concentration do volatiles reduce the reliability of MEPs?
Low concentrations
Effect on EEG
Increased amplitude, burst suppression > MAC 1.5
Which IAs are epileptogenic?
Enf > Sevo
Volatiles ____ NDMRs (and DMR)
potentiate
Which volatiles trigger MH?
All
NOT N2O
Effect on Liver
Dose dependent reductions in hepatic blood flow, mild LFT elevations
Severe liver injury may occur with _____
Iso, Des
Effect of VAs on CO result in
Positive feedback —> VAs depress CO, decreased CO = more Pa; excessive depth of anesthesia may occur
Anesthetic preconditioning
All VAs produce biphasic preconditioning on myocardium that rivals ischemic preconditioning (myocardial injury is limited after insult, fxn is preserved)
Which IAs are pungent?
ISO, Des
Pungency of an IA causes
Bronchoconstriction, airway irritation
How to avoid effects of pungency
Small doses of opioids attenuate this effect
Which VA potentiates roc most?
Des
Liver effect from VAs is a result of
CYP450 metabolism results in trifluoroacetate — binds covalently to hepatocytes which triggers an immune response
hepatic necrosis*
Do VAs effect the renal system?
Yes - Dose dependent decrease in renal blood flow, GFR, UO
d/t dec. BP/CO
Nephrotoxicity is characterized by
Polyuria, hypernatremia, hyperosmolality, increased serum creat., poorly concentrated urine
Renal Toxin _____ at levels _____
Inorganic F > 50 mmol/L
Which VA may concern anesthetist with renal toxicity?
Sevo — metabolized to inorganic F
Prolonged Sevo anesthesia ______ impair renal function
Does not
How is compound A formed?
CO2 absorbents (K/Na hydroxide) react with Sevo
Compound A
Nephrotoxin — proximal renal tubular injury
Dose at which Compound A causes nephrotoxicity
50 ppm
How do VAs effect skeletal muscles
Relaxation
N2O = rigidity at high concentration s
When does MH manifest?
Not always immediate - Des: 3 hours post VA
Effect of VAs on OB
Dose dependent decrease in uterine contractility/blood flow
Effect of VAs on OB - modest vs substantial
Modest: 0.5 MAC
Substantial: >1 MAC
Effect of VAs on Immune system
Depressed PMLs inhibited (inflammation)
N2O effect on genetics
Teratogenic d/t inhibition of DNA synthesis (avoid in pregnancy; esp 1st trimester)
Effects on Bone marrow function
N2O causes megaloblastic changes/agranulocytosis
D/t effects on Vit B — production of DNA/erythrocytes
Chronic administration of N2O can lead to
Peripheral neuropathy - d/t vitamin B12 enzyme dysfunction, peripheral/spinal cord nerve degeneration (prolonged administration 15 days); and symptoms of pernicious anemia
Effects of IAs on systemic O2 requirements
Decreased
Des > ISO produces?
Carbon monoxide from degradation by CO2 absorbants
Cost considerations of IAs
- vapor pressure (mL vapor from each mL fluid)
- potency
- solubility
- FGF (open or closed)
