23. Ax principles Flashcards by Krista Cioffi

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)

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administration of any drug in the the body is balanced by what two factors

redistribution2. metabolism/excretion

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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

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Can diazepam be given as a CRI

NO it is unable to be diluted bc it is water insoluble

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what are anesthetic drug delivery and redistribution dependent on

cardiac output (CO = SV x HR)

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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

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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)

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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

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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

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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

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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

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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)

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CO2 absorbent in rebreathing systems

SODA LIME–strong base–granular–changes color upon saturation and interaction with acid(ethyl violet)

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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

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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

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minimum oxygen flow for rebreathing circuit

Rebreathing/circle circuitmin O2 flow = patient’s metabolic O2 demand = 10 x kg

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why do you want to minimize dead space in a circuit

to minimize rebreathing of CO2

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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

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rebreathing circuits are reserved for patients larger than _____kg

5 kgbc nonrebreathing systems cannot eliminate CO2 readily enough for large patients

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4 benefits of an endotracheal tube

maintains patent airway2. ensures delivery of gas to lungs3. protects against aspiration4. minimizes personal exposure to inhalants

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2 disadvantages of endotracheal tube

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increases airway resistance2. increases dead space

what is the advantage to Murphy’s eye at the end of an endotracheal tube

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allows air passage should the end of the tube get occluded

In a patient breathing room air, hypoxemia will develop within _____________sec of apnea

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30 s

a patient breathing 100% oxygen may not become hyperemic for _______ minutes after onset of apnea

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5 minutesPREOXYGENATE 4-5 L min w 100% O2 for 5 minsaturates alveoli with oxygen, providing a reservoir of oxygen

most common carrier gas for inhalant anesthesia

oxygen!100% oxygen causes more alveolar collapse than 40% O2 bc of the nitrogen in mixed gas is not absorbed and keep alveoli open longerabsorption atelectasis

T/FNitrogen causes structural support of alveoli

TRUE

how to prevent surgical fire (high OXYGEN + laser sx)

protect endo tracheal tube (tape, moist gauze) orHe : O2 ratio 70 : 30

T/F the oxygen flowmeter should not be used with rebreathing circuits

FALSEthe oxygen flow meter should not be used with NONrebreathing circuits because of the significant risk of barotrauma

when is a leak more noticeable under positive pressure mechanical ventilation

leaks are more noticeable during expiration when bellows are ascended

initial pressure settings for dogs v cats on mechanical pressure cycled ventilation

Peak inspiratory pressurescats 12 mm Hgdogs 15 mm Hg

T/Foxygen content of the blood is largely dictated by [Hb]

TRUECaO2 = 1.34 x Hb x SaO2 + PaO2 x 0.003as Hb decr, CaCo2 decreases in a linear fashion (changes more radically with Hb than with PaO2)

The heart spends more of its time in what phase

DIASTOLEthus, it has more impact on MAPMAP = DAP + [(SAP-DAP)/3]

Doppler MOA

recognition of a sound change that is produced when blood passes under the doppler crystalonly detect SAP

cats and doppler measurements

in catsdoppler UNDERestimates SAP up to 25 mm Hg

dogs and doppler measurements

in dogsdoppler correlates well with direct ABP in anesthetized patients

cats and oscillometric BP monitoring

in catsoscillometric UNDERestimates SAP but precise for MAP, DAP

dogs and oscillometric BP monitoring

in dogsoscillometric UNDERestimates SAP, DAP, MAP

Oscillometric vs doppler BP readingswhich one is affected by irregular heart rates and rhythms?

Oscillometric

what does hypercarbia lead to

hypoventilation --> hypercarbia (PCO2 > 45 mm Hg)1. resp acidosis2. vasodilation3. incr intracranial P4. SNS stimulation5. anxiety, arrthymias

what does hypocarbia lead to

hyperventilation --> hypocarbia (PCO2 < 25 mm Hg)1. resp alkalosis2. vasoconstriction

T/Falveolar CO2 closely approximates arterial CO2

TRUEbc COs efficiently passes out of the blood stream and is exhaledmonitored by end tidal CO2 monitors as an accurate and reliable way to monitor PaCO2

end tidal CO2 readings and nonrebreathing circuit

bc high gas flow rates, end tidal CO2 will be diluted and read artificially lowcan be overcome with a side stream CO2 monitor that samples close to endotracheal tube

normal capnograph reading and phases

begins with inspiration of fresh gas = 0 (phase 0on expiration, CO2 should rapidly elevate (phase 1)due to mixing with dead space and gas it will plateau (phase 2)peaks at the end of expiration (phase 3)next inspiration = 0 (phase 4)

abN CO2 readings indicate

--confirms intubation--dx of impending cardiac arrest/cardiac arrest--rebreathing--malignant hyperthermia--disconnection of the circuit--dislodgment of endotracheal tube

Pulse oximetry MOA

Estimates the % of Hb that is saturated with O2; ARTERIAL; relies on pulsatile nature--emits 2 light frequencies (specific for oxyHb & deoxyHb) through the tissue and into the sensor--calculates the amt of OxyHb and deoxyHb based on the amount of light arriving at the sensor% = amount of oxyHb

T/Fcarboxyhemoglobin and methemoglobin can affect pulse oximetry readings

TRUE

two types of pulse oximetry probes

transmittance---light emits from one side and sensed on the other side; MOST COMMONreflectance--light is sent and reflected back to a sensor adjacent to the light source

60 mm Hg defines hypoxia and corresponds to what pulse oximetry reading

90%

what are inaccuracies in pulse oximetry due to

1. vasoconstriction,decr CO, poor perfusion2. movement3. pigment4. profound anemia < 10% HCT5. profound hypoxemia

end tidal inhalant monitoring closely parallels what?

brain concentrations of inhalantbasis for determination of minimum alveolar concentration values

normal CVP values

0-5 mm Hg0-8 cm H20

23. Ax principles Flashcards

(51 cards)