23. Ax principles Flashcards
two methods used to initiate and maintain a state state concentration of drug at the level of the brain
- loading dose (usually higher than target dose), followed by a CRI (lower dose maintenance dose)2. start maintenance dose CRI allowing it to accumulate over time (~ 5 half lives)
administration of any drug in the the body is balanced by what two factors
- redistribution2. metabolism/excretion
T/Fdrugs that are more lipid soluble take longer to achieve stead state
TRUEDrugs that are more lipid soluble take longer to achieve stead state because they readily redistribute to many areas of the body
Can diazepam be given as a CRI
NO it is unable to be diluted bc it is water insoluble
what are anesthetic drug delivery and redistribution dependent on
- cardiac output (CO = SV x HR)
the time necessary to to achieve steady state of an anesthetic depends on what
- minute ventilation2. cardiac output3. speed of redistribution4. amount of drug that is eliminated5. with inhalants, speed on inhalant action depends on gas solubility
low flow (closed circuit) anesthesia
at equilibrium, only enough inhalant must be supplied to make up for that lost from the system during redistribution/metabolism only enough oxygen must be supplied to meet metabolic needs (5 ml/kg/m)
methods of vaporization
vaporizers are designed and calibrated to deliver a constant concentration of anesthetic vapor1. flow over ** most common**2. bubble through3. direct injection
most common vaporizer output
variable bypass vaporizersthe incoming gas is split to direction some into the vaporizing chamber to pick up inhalant and other part through the bypass champed straight to the outlet
T/FIN circuit vaporizers have highly variable output
TRUEIN circuit vaporizers have variable output based on ambient temp, patient ventilation, and volatility of agentvet med uses OUT of circuit vaporizers; not part of patients breathing circuit; deliver a constant dose regardless of the patient’s minute volume
what happens if an incorrect inhalant agent is placed in an agent specific vaporizer
higher or lower concentrations will be usedout of circuit vaporizes are designed and calibrated for use with a single agent only
two types of anesthesia patient circuits
- rebreathing/circle circuit (uses CO2 absorbent to remove CO2; one way valves)2. nonrebreathing (use high gas flow rates to decr CO2–Bain)
CO2 absorbent in rebreathing systems
SODA LIME–strong base–granular–changes color upon saturation and interaction with acid(ethyl violet)
T/FDilution of inhalant gas occurs with rebreathing circle circuits
TRUEDilution of inhalant gas occurs with rebreathing circle circuits. Thus, inspired concentration may be less than vaporizer setting initially.nonrebreathing circuits, no dilution occurs, thus the inhalant concentration on the vaporizer indicates the inspired concentration by the patient
How to adjust for dilution gas entering the circuit at the beginning of anesthesia in a rebreathing circuit
increase vaporizer settingor increase the carrier gas flow
minimum oxygen flow for rebreathing circuit
Rebreathing/circle circuitmin O2 flow = patient’s metabolic O2 demand = 10 x kg
why do you want to minimize dead space in a circuit
to minimize rebreathing of CO2
recommended fresh gas flow rate for a nonrebreathing circuit
min flow = 3 x MV = 3 x (RR x TV)TV= tidal volume = 15 ml/kg~ 200-500 ml/kg
rebreathing circuits are reserved for patients larger than _____kg
5 kgbc nonrebreathing systems cannot eliminate CO2 readily enough for large patients
4 benefits of an endotracheal tube
- maintains patent airway2. ensures delivery of gas to lungs3. protects against aspiration4. minimizes personal exposure to inhalants