Week 10 MAC and Inhalation Agents Flashcards
What is MAC?
Minimum Alveolar Concentration= the minimum concentration necessary to prevent movement in 50% of patients in response to skin incision
MAC amnesia is
25% MAC = concentration that blocks anterograde memory in 50% of awake patients
MAC intubation is
130% MAC= concentration required to prevent movement and coughing during endotracheal intubation
Factors that increases MAC include
Age: term infant to 6 months= highest MAC requirement
Chronic ETOH abuse
Factors that decrease MAC
Pregnancy
Lithium
Cardiopulmonary Bypass
Factors that have no effect on MAC
Thyroid gland dysfunction
MAC Values:
Sevo 1.1
Iso 2.2
Des 6.6
N2O 105
A high inspired concentration of an agent speeds/slows induction
speeds
Increased alveolar ventilation increases/decreases rate of rise of agent and speeds/slows induction
increases
speeds
The anesthetic system alveolar uptake of agents depends on
volume, solubility of components, gas flow rates- higher rates speed induction
Uptake from alveolar space depends on
solubility, cardiac output, and alveolar/ venous partial pressure difference
_______ is the important single factor in determining the speed of induction and the rate of emergence
Solubility
Blood Gas Coefficients
Sevo 0.69 Iso 1.43 Des .42 N20 .47 Enflurane 1.8 Halothane 2.3
an increased ratio wants to stay in the blood
a decreased ratio wants to be in the gas phase
A poorly soluble agent has a faster/slower inhalation induction and a faster/slower emergence
faster
faster
A high cardiac output speeds/slows induction
slows
A low cardiac output speeds/slows induction
speeds
A large alveolar / venous partial pressure difference with an agent enhances uptake and speeds/slows inhalation induction
speeds
The ______________ is the ability of a large volume uptake of a first gas (N2O) to accelerate the rate of rise of the alveolar partial pressure of a concurrently administered companion gas (agent) thus speeding induction
second gas law
__________ results from the dilution of alveolar O2 concentration by a large amount of N2O “outgasing” or leaving the pulmonary capillary blood at the conclusion of N20 administration
Rapid desaturation can be seen
Diffusion Hypoxia
WHy would you not want to extubate while on 70% N2O?
Diffusion Hypoxia
This is avoided by administering 100% O2 following N2O use
N2O is a good ______ that can increase ________. Avoid use of N2O with ________________________. N2O increases PVR especially in patients with __________.
good analgesic
increases PONV
avoid in closed gas spaces, PTX, complete bowel obstruction, inner ear, pneumocephalus, air embolism, intraocular bubbles
pulmonary htn
N2O is nonflammable but is an _______ source that __________.
O2
supports combustion
In rat experiments with N2O given to pregnant rats for greater than 24 hours, N2O inhibited _________, needed for DNA synthesis. Long term use can lead to __________.
Methionine Synthesis
Peripheral neuropathy and megaloblastic anemia
Halothane causes a dose dependent decrease in __________. Halothane contains a ____________ preservative, used for inhalation induction in children which may cause a __________ stimulation, and may see ___________ with a MAC>1, pretreat with __________. Halothane sensitizes the heart to ___________. Use _________ with caution.
contractility thymol preservative vagal stimulation bradycardia atropine catecholamines, dysrhythmogenic use epinephrine with caution
