Mod1: Monitoring for Cardiac Surgery - PULSE OXIMETRY - TEMPERATURE

Question 1

_{Pulse Oximetry}

What are the overall characteristics of pulse oximetry?

Answer 1

Measurement of oxygen saturation

Uses a sensor containing light source

Great monitoring tool that can tell you something about each of the other monitors

Measure oxygenation, tissue perfusion (via pulse amplitude)

Measures heart rate and rhythm to a degree

Can tell you about rhythm that are not necessarily perfused because the pulse ox will loose its volume

Question 2

_{Pulse Oximetry - INDICATIONS}

What are pre-op indications for pulse oximetry?

Answer 2

Baseline O2 saturation

Detect unsuspected hypoxemia during line placement after sedation

Question 3

_{Pulse Oximetry - INDICATIONS}

What’s the purpose of using pulse oximetry intra-op?

Answer 3

Assessment of oxygenation intraoperatively

Question 4

_{Pulse Oximetry - INDICATIONS}

Why is the use of pulse oximetry very important in cardiac pt?

Answer 4

Hypoxemia = decreased O2 supply

=> contributes to ischemia

Question 5

_{Pulse Oximetry - INDICATIONS}

How can perfusion be assessed using pulse oximetry?

Answer 5

Adequacy of perfusion likely when pulse oximeter shows reading/waveform

Question 6

_{Pulse Oximetry - INDICATIONS}

During arrhythmias, how can non perfused beat be detected via pulse oximetry?

Answer 6

Pulse oximetry will loose its volume

Question 7

_{Pulse Oximetry}

What are advantages of Pulse Oximetry?

Answer 7

Ease of use

Continuous monitoring

Noninvasive

Variable pitch correlates with degree of saturation

Accurate

Question 8

_{Pulse Oximetry}

What are disadvantages of Pulse Oximetry?

Answer 8

Saturation unobtainable in poor perfusion states

Interference with use of electrocautery

Interference with other monitors

Requires pulsatile flow to operate

In these situations, it becomes increasingly important to assess the pt while using the pulse ox as an assisted device

Question 9

_{Pulse Oximetry}

Which poor perfusion states could make saturation unobtainable?

Answer 9

Poor perfusion to limbs (e.g., CV disease)

Hypothermia common during CV surgery

Administration vasoconstrictors

_{<em>In these situations, it becomes increasingly important to assess the pt while using the pulse ox as an assisted device</em>}

Question 10

_{TEMPERATURE - INDICATIONS}

Why is adequate temperature monitoring extremely important during CPB?

Answer 10

Intentional Systemic hypothermia essential component during CPB

Temperatures may be reduced to 20-32˚C

Question 11

_{TEMPERATURE - INDICATIONS}

What’s the purpose of Intentional Systemic hypothermia during CPB

Answer 11

Protect organs with high metabolic rate

Cerebral protection and Myocardial protection via reduction of oxygen demand

Question 12

_{TEMPERATURE - INDICATIONS}

What could happen if the body temperature was not reduced during CPB?

Answer 12

Cells will begin to make energy via anaerobic metabolism

And because of the reduced oxygen, sufficient energy will not be available

Toxic metabolites like lactate will be released

Question 13

_{TEMPERATURE - INDICATIONS}

For every 1˚C reduction in body temperature, metabolic rate reduced by

Answer 13

8%

Question 14

_{TEMPERATURE - INDICATIONS}

At what body temperature would the metabolic rate be Half the body’s normal metabolic rate?

Answer 14

at 28˚C

Question 15

_{TEMPERATURE - INDICATIONS}

True or False: Normothermia through active rewarming must be achieved prior to separation from CPB

Answer 15

True

Question 16

_{TEMPERATURE - INDICATIONS}

What are the effects of Temperatures <28˚C on the SA node?

Answer 16

Increase in erratic SA node pacing and

Ventricular irritability

Question 17

_{TEMPERATURE - INDICATIONS}

At which temperature could cardiac Fibrillation occur?

Answer 17

Between 28-30˚C

Question 18

_{TEMPERATURE - INDICATIONS}

True or False: Cardiac fibrillation that result from hypothermia (28-30C) can easily be treated with defibrillation

Answer 18

False

Fibrillation that result from hypothermia (28-30C) is often unaffected by defibrillation

Question 19

_{TEMPERATURE - INDICATIONS}

What is a possible neurologic consequence of Inadequate brain cooling during circulatory arrest

Answer 19

Neurologic injury

Question 20

_{TEMPERATURE - INDICATIONS}

What is a possible adverse neurologic consequence of cerebral hyperthermia (overshooting > 41˚ C) during rewarming phase following CPB?

Answer 20

Worsens neurologic damage

Question 21

_{TEMPERATURE - SITES OF MEASUREMENT}

Why is it important to measure “core”, “central” or “brain temperature”?

Answer 21

Brain is most vital organ

Brain easily susceptible to ischemia during low oxygen flow states

Question 22

_{TEMPERATURE - SITES OF MEASUREMENT}

Where does core temperature comes from? How can it be monitored?

Answer 22

From tissues that are highly perfused

Whose temperature is uniform and can be highly compared to the brain

Can be monitored via nasopharyngeal, pulmorary atery, esophageal or tympanic membrane

Question 23

_{TEMPERATURE - SITES OF MEASUREMENT}

What characteristize the locations where peripheral or shell temperatures are measured?

Answer 23

Represent majority body but

Receive smaller proportion blood flow

This is a reason why peripheral temperatures are significantly lower than core temperature

Do not accurately reflect brain temperature

Peripheral temperatures could be measured at Muscle, Fat, or Bone

Question 24

_{TEMPERATURE - SITES OF MEASUREMENT}

During bypass, why is it important to ensure that the temperature is at closed to brain temperature as possible?

Answer 24

Because we are trying to ensure neuro protection

Question 25

_{TEMPERATURE - SITES OF MEASUREMENT}

Since direct brain temperature measurements are not possible how is brain temperature assessed?

Answer 25

Surrogate sites are used to “estimate” brain temperature

Question 26

_{TEMPERATURE - SITES OF MEASUREMENT}

What is the the most reasonable site for measurement of brain temperature? Why is that?

Answer 26

Jugular Venous Bulb

The Jugular bulb is part of the internal jugular vein and is located close to the inner ear

Receives deoxygenated blood from neck and brain

More widened/dilated than the rest of IJV

99% of the bulb blood is from intracerebral vasculatur

Question 27

_{TEMPERATURE - SITES OF MEASUREMENT}

True or False: Catheters may be inserted into the jugular vein bulb for the sole purpose of measuring temperature

Answer 27

False

Catheters are not inserted for the sole purpose of measuring temperature

Question 28

_{TEMPERATURE - SITES OF MEASUREMENT}

Why is the the Retrograde catheter used for Jugular bulb temperature measurement typically placed in the Right IJ (into the bulb)?

Answer 28

Because the Right IJ has a larger diameter

Question 29

_{CORE TEMPERATURE}

True or False: All core temperature sites are adequate for measuring temperature during bypass surgery, and all of them have some sort of lag time, but the arterial inflow line has the smallest amount of temperature discrepency of all of the other measurement sites when compared to jugular bulb temperature

Answer 29

True

Question 30

_{CORE TEMPERATURE​}

Which does research indicates is the best indicator of JVB temperature, and therefore “true” cerebral temperature

Answer 30

Arterial inflow line from CPB circuit

Question 31

_{CORE TEMPERATURE​}

What are other estimates of brain temperature?

Answer 31

Nasopharyngeal

Tympanic membrane

PA catheter

Esophageal

Question 32

_{CORE TEMPERATURE​}

Nasopharyngeal site provides Accurate estimate brain temp

But:

Answer 32

Lag time between it and actual brain temp during rewarming

Question 33

_{CORE TEMPERATURE​}

Tympanic membrane site reflects brain temperature, but:

Answer 33

Lag time

Question 34

_{CORE TEMPERATURE​}

PA catheter provides Accurate estimate of brain temp when pulmonary blood flow is present - before and after CPB, possibly not during, why?

Answer 34

… (slide 22)???

Question 35

_{CORE TEMPERATURE​}

Why should the Esophageal site not be routinely used for temperature measurement in cases involving CPB?

Answer 35

Mediastinal structure = greatly effected by blood returning from pump

Question 36

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

True or False: Monitoring arterial inflow temperature is a ClassI clinical recommendation

Answer 36

True

Shows evidence of being highly useful and effective

Question 37

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

Which is recommended to be utilized as a surrogate for cerebral temperature during CPB?

Answer 37

The oxygenator arterial outlet blood temperature

Question 38

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

Why should you limit arterial outlet blood temperature to 37 °C during rewarming?

Answer 38

To avoid brain hyperthermia, since

The arterial outlet blood temperature underestimates cerebral temperature

Question 39

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

Based on (Class IIa) Recommendations, which type of temperature measurement is reasonable for weaning and for immediate post-bypass?

Answer 39

Pulmonary artery or

Nasopharyngeal temperature recording

Question 40

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

True or False: Currently there is no recommendation concerning “optimal” temperature for weaning from bypass

Answer 40

True

Question 41

_{SHELL TEMPERATURE}

True or False: Monitoring bladder or rectal temperature continues to be standard of practice in many facilities

Answer 41

True

Question 42

_{SHELL TEMPERATURE}

How many degrees lower can bladder and rectal temperatures be compared to brain stem temperature when rewarming during bypass?

Answer 42

2 to 4 degrees lower

Question 43

_{SHELL TEMPERATURE}

Why is bladder temperature not considered core temperature?

Answer 43

Because it is inaccurate if renal blood flow and urine production is decreased

Question 44

_{SHELL TEMPERATURE}

Why is rectal temperature not considered core temperature?

Answer 44

Because it reflects muscular temperature

NOT CORE (traditionally thought as)

Question 45

_{SHELL TEMPERATURE}

According to Miller, which type of temperature monitors are bladder and rectal temperatures classified as?

Answer 45

Intermediate temperature monitors

Question 46

_{SHELL TEMPERATURE}

Why does skin temperature provide erroneous readings?

Answer 46

Because it is greatly affected by external factors, such as:

Cooling/warming blankets

Cool environment

Question 47

_{SHELL TEMPERATURE}

Which temperatures are considered “shell temperatures”

Answer 47

Bladder, Rectal, & Skin temperatures

Question 48

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

What could happen if “overheating”/Hyperthermia occurs during the rewarming phase of bypass?

Answer 48

Neurologic injury

Evidence supports extreme caution

Question 49

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

Increased rate of which conditions is associated with hypothermia during CPB

Answer 49

Mediastinitis & Acute kidney injury

Question 50

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

Why is it recommended to keep bypass machine outlet (or arterial line inflow) temperature below 37*C?

Answer 50

Because hyperthermia could cause neurologic injury, and

Hypothermia could cause Mediasinitis & Acute kidney injury

Question 51

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

Why is it recomended to use core temp sources over shell temp sources during CPB?

Answer 51

Core temps lag behind actual brain temperature during rewarming

Shell temps lag behind core during cooling & rewarming

Core > shell at separation of bypass (rewarming phase)

Question 52

_{WHICH ONES TO MONITOR DURING CARDIAC SURGERY??}

What is a possible neurological adverse effect of overshooting during the rewarming phase of CPB?

Answer 52

CEREBRAL HYPERTHERMIA