23. Ax principles

Question 1

two methods used to initiate and maintain a state state concentration of drug at the level of the brain

Answer 1

1. 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)

Question 2

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

Answer 2

1. redistribution2. metabolism/excretion

Question 3

T/Fdrugs that are more lipid soluble take longer to achieve stead state

Answer 3

TRUEDrugs that are more lipid soluble take longer to achieve stead state because they readily redistribute to many areas of the body

Question 4

Can diazepam be given as a CRI

Answer 4

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

Question 5

what are anesthetic drug delivery and redistribution dependent on

Answer 5

1. cardiac output (CO = SV x HR)

Question 6

the time necessary to to achieve steady state of an anesthetic depends on what

Answer 6

1. minute ventilation2. cardiac output3. speed of redistribution4. amount of drug that is eliminated5. with inhalants, speed on inhalant action depends on gas solubility

Question 7

low flow (closed circuit) anesthesia

Answer 7

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)

Question 8

methods of vaporization

Answer 8

vaporizers are designed and calibrated to deliver a constant concentration of anesthetic vapor1. flow over ** most common**2. bubble through3. direct injection

Question 9

most common vaporizer output

Answer 9

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

Question 10

T/FIN circuit vaporizers have highly variable output

Answer 10

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

Question 11

what happens if an incorrect inhalant agent is placed in an agent specific vaporizer

Answer 11

higher or lower concentrations will be usedout of circuit vaporizes are designed and calibrated for use with a single agent only

Question 12

two types of anesthesia patient circuits

Answer 12

1. rebreathing/circle circuit (uses CO2 absorbent to remove CO2; one way valves)2. nonrebreathing (use high gas flow rates to decr CO2–Bain)

Question 13

CO2 absorbent in rebreathing systems

Answer 13

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

Question 14

T/FDilution of inhalant gas occurs with rebreathing circle circuits

Answer 14

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

Question 15

How to adjust for dilution gas entering the circuit at the beginning of anesthesia in a rebreathing circuit

Answer 15

increase vaporizer settingor increase the carrier gas flow

Question 16

minimum oxygen flow for rebreathing circuit

Answer 16

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

Question 17

why do you want to minimize dead space in a circuit

Answer 17

to minimize rebreathing of CO2

Question 18

recommended fresh gas flow rate for a nonrebreathing circuit

Answer 18

min flow = 3 x MV = 3 x (RR x TV)TV= tidal volume = 15 ml/kg~ 200-500 ml/kg

Question 19

rebreathing circuits are reserved for patients larger than _____kg

Answer 19

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

Question 20

4 benefits of an endotracheal tube

Answer 20

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

Question 21

2 disadvantages of endotracheal tube

Answer 21

1. increases airway resistance2. increases dead space

Question 22

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

Answer 22

allows air passage should the end of the tube get occluded

Question 23

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

Answer 23

30 s

Question 24

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

Answer 24

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

Question 25

most common carrier gas for inhalant anesthesia

Answer 25

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

Question 26

T/FNitrogen causes structural support of alveoli

Answer 26

TRUE

Question 27

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

Answer 27

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

Question 28

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

Answer 28

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

Question 29

when is a leak more noticeable under positive pressure mechanical ventilation

Answer 29

leaks are more noticeable during expiration when bellows are ascended

Question 30

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

Answer 30

Peak inspiratory pressurescats 12 mm Hgdogs 15 mm Hg

Question 31

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

Answer 31

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)

Question 32

The heart spends more of its time in what phase

Answer 32

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

Question 33

Doppler MOA

Answer 33

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

Question 34

cats and doppler measurements

Answer 34

in catsdoppler UNDERestimates SAP up to 25 mm Hg

Question 35

dogs and doppler measurements

Answer 35

in dogsdoppler correlates well with direct ABP in anesthetized patients

Question 36

cats and oscillometric BP monitoring

Answer 36

in catsoscillometric UNDERestimates SAP but precise for MAP, DAP

Question 37

dogs and oscillometric BP monitoring

Answer 37

in dogsoscillometric UNDERestimates SAP, DAP, MAP

Question 38

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

Answer 38

Oscillometric

Question 39

what does hypercarbia lead to

Answer 39

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

Question 40

what does hypocarbia lead to

Answer 40

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

Question 41

T/Falveolar CO2 closely approximates arterial CO2

Answer 41

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

Question 42

end tidal CO2 readings and nonrebreathing circuit

Answer 42

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

Question 43

normal capnograph reading and phases

Answer 43

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)

Question 44

abN CO2 readings indicate

Answer 44

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

Question 45

Pulse oximetry MOA

Answer 45

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

Question 46

T/Fcarboxyhemoglobin and methemoglobin can affect pulse oximetry readings

Answer 46

TRUE

Question 47

two types of pulse oximetry probes

Answer 47

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

Question 48

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

Answer 48

90%

Question 49

what are inaccuracies in pulse oximetry due to

Answer 49

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

Question 50

end tidal inhalant monitoring closely parallels what?

Answer 50

brain concentrations of inhalantbasis for determination of minimum alveolar concentration values

Question 51

normal CVP values

Answer 51

0-5 mm Hg0-8 cm H20