05 - Clinical Pharm of Inhalationals Flashcards
MAC is the concentration that prevent movement in ___ of patients in response to a certain stimulus
50%
Minimal alveolar concentration is really a
Median
MAC is best used to compare
Different agents
What are the other MACs?
MACawake (0.1 x MAC)
MACbar (1.7-2.0 x MAC)
MACrecall (0.3-0.5 x MAC)
T or F. MAC is additive.
True
Factors that increase MAC
Younger age Chronic alcoholism Anxiety? Acute sympathetic increase - COCAINE Hyper metabolic state (thyroid? High fever)
Factors that decrease MAC
Premedication Older age Pregnancy Acute alcohol usage Hypothermia Hypercarbia/hypoxia Sympathetic blockade
How much does MAC decrease with age?
Six percent per decade after age 40
Look at that chart
LOOK AT IT
Nitrous oxide is inorganic, _______, sweet smelling! and relatively insoluble
Non volatile
NO2 is non flammable but supports
Combustion
Nitrous cause CV _____ but stimulates
Depression
Catecholamines
Respiratory effects of NO2
Increased RR
Decreased TV
No change in MV
Very decreased hypoxic drive
Has analgesic properties but is not complete anesthesia?
Nitrous Increased ICP (CBF, CBV, CMRO2)
Which inhalational has no muscle relaxant properties?
Nitrous
T or F. NO2 can induce malignant hyperthermia.
False
Renal effects of NO2
Decreased GFR
Decreased urine output (due to decreased RBF)
Hepatic effects of NO2
Slightly decreased hepatic blood flow
GI effects of NO2
PONV (activates CTZ)
Elimination of NO2 is almost
100% exhalation
How does NO2 inactivate methionine synthetase?
It oxidizes the Co atom in B12
What are the toxicities of NO2?
Inactivates methionine synthetase Affects myelin formation Homocysteine accumulation Inhibits thymidylate synthetase (DNA synthesis) Bone marrow depression
What effects are seen with disturbed myelin formation?
Peripheral neuropathies
Neurotoxicity
Teratogenicity is caused by
Inhibition of thymidylate synthetase (DNA synthesis) which is one of the effects of NO2
Teratogenicities are abnormalities of physiological development
What results from the bone marrow depression seen with NO2?
Megoloblastic anemia (anemia that results from DNA synthesis)
Specifically, pernicious anemia which causes alteration to the secretion of intrinsic factor, a protein essential for the absorption of B12 in the ileum
How long does it take to recover from NO2?
> 4 days
T or F. It is OK to harvest bone marrow from someone with megaloblastic anemia.
True???
_______ exposure to NO2 is particularly harmful
Serial
Other problems with NO2
Added cost of installation/management of pipeline
Added complexity to anesthesia machine
Concerns about exposure to workers
Risks of low FiO2 and catastrophic hypoxia
NO2 is ____ more soluble in the blood than N2
35x
NO2 diffuses out of blood and into ________ faster than air can diffuse into blood which can cause
Closed airspaces
Pneumothorax, trauma, venous air embolism, intracranial air, acute GI obstruction, intraocular air, tympanic membrane, blebs/bullae
Some other contraindications to NO2
Inborn errors of single carbon metabolism (and untested family members), antifolate chemotherapeutics, pernicious anemia, megaloblastic anemia, serial anesthetics
NO2 is recommended to be avoided for maintenance, especially in the ______ pregnancy and
First trimester
Extremes of age
Consider? Avoiding in patients with cardiac, vascular, neurogenerative disease
A halogenated alkane
Halothane
Halothane is cheap, safe, used worldwide. It is
Sweet
Non pungent odor
CV effects of halothane
Myocardial depression
By how much can halothane decrease blood pressure and cardiac output?
Up to 50%
Halothane ______ electrical conduction of the heart. It is sensitive to
Slows
catecholamines
Respiratory effects of halothane
Increased RR Very decreased TV Decreased MV Very decreased hypercapnic drive Potent bronchodilator
Why does halothane cause blunted autoregulation?
It dilates vessels and increases cerebral blood flow but decreases CMRO2
What must be done before starting halothane?
Hyperventilate
Neuromuscular effects of halothane
Muscle relaxation
Potentiates NMB
Triggers MH