Lecture 8: Pulmonary Intraop Monitoring/Difficult Airway Algorithm

Question 1

940 nm

Answer 1

Infrared light, oxyhemoglobin absorbs more of this light, corresponds to 100% saturation

Question 2

660 nm

Answer 2

Red light, deoxyhemoglobin absorbs more of this light, corresponds to 50% saturation

Question 3

Very rough rule—PaO2 40, 50, 60 for sat ___, ___, ___

Answer 3

70, 80, 90

Question 4

Sat 100, PaO2 ___

Answer 4

100

Question 5

Sat 95, PaO2 ___

Answer 5

75

Question 6

Sat 90, PaO2 ___

Answer 6

60

Question 7

Sat 75, PaO2 ___

Answer 7

40 (mixed venous blood in pulmonary artery)

Question 8

Sat 60, PaO2 ___

Answer 8

30

Question 9

Sat 50, PaO2 ___

Answer 9

27

Question 10

Can a standard pulse ox. Be used in MRI?

Answer 10

No—may burn patient, dedicated MRI probe needed

Question 11

Endobronchial intubation will usually go undetected by pulse ox. In…

Answer 11

The absence of lung disease or low FiO2

Question 12

Limitations of pulse ox—hemoglobin variants

Answer 12

Carboxyhemoglobin (COHb)

Methemoglobin (MetHb)

Question 13

Carboxyhemoglobin

Answer 13

• From CO poisoning

- CO is viewed as oxyhemoglobin by pulse ox. And shows a SPO2 of 100% (overestimation of oxygenation)

Question 14

What is used to distinguish between oxyhemoglobin and carboxyhemoglobin?

Answer 14

A co-oximeter

Question 15

Methemoglobin

Answer 15

Fe 2+ (ferrous) in Hb is oxidized to Fe 3+ (ferric) form and cannot transport O2

Question 16

Methemoglobin—Cyanosis seen when ___ of Hb is in methemoglobin form

Answer 16

15%

Question 17

Methemoglobin is caused by…

Answer 17

• Nitrates
• Nitrites
• Sulfonamides
• Benzocaine (hurricane spray)
• Nitroglycerine (NTG)
• Nitroprusside (SNP)

Question 18

Methemoglobin—does it absorb equally at both wavelengths?

Answer 18

Yes—1:1

Question 19

Methemoglobin—shows a SPO2 of ___ regardless of true oxygen saturation

Answer 19

85%

Question 20

Treatment for methemoglobin

Answer 20

Methylene blue or ascorbic acid

Question 21

What two things do not affect pulse oximetry?

Answer 21

Fetal hemoglobin and bilirubin

Question 22

Severe hypoxemia—poor accuracy at SPO2 < ___

Answer 22

30%

Question 23

Pulse ox won’t function well if Hb < ___

Answer 23

3-4 gm/dL

Question 24

Pulse ox is designed to assume pulsation are ___

Answer 24

Arterial—why right heart failure (for pulmonale) or tricuspid regurgitation disturb SPO2, seen in dependent (down) limb

Question 25

What dyes interfere with SPO2?

Answer 25

Methylene blue and idocyanine green—will drop SPO2 for 5-10 minutes

Question 26

Malpositioned sensor effect on SPO2

Answer 26

Penumbra effect, shows SPO2 of 90-95%

Question 27

Capnography rapidly and reliably indicates ___ but does not reliably detect ___

Answer 27

Esophageal intubation, endobronchial intubation

Question 28

What is the gold standard for tracheal intubation?

Answer 28

+ ETCO2

Question 29

Capnometer

Answer 29

Measures CO2

Question 30

Capnograph

Answer 30

Records and displays CO2

Question 31

Not all capnometers display a ___

Answer 31

Capnogram

Question 32

All capnographs are in part ___

Answer 32

A capnometer

Question 33

CO2 is depicted graphically as a ___

Answer 33

Capnogram

Question 34

CO2 is recorded by a ___

Answer 34

Capnograph

Question 35

CO2 is measured by a ___

Answer 35

Capnometer

Question 36

Normal capnograph components

Answer 36

``` AB segment BC segment CD segment D point DE segment ```

Question 37

AB segment =

Answer 37

Beginning exhalation, dead space gas

Question 38

BC segment =

Answer 38

Upstroke | Exhalation, mixing of gases (dead space + alveolar gas)

Question 39

CD segment =

Answer 39

Alveolar plateau, alveolar rich gas

Question 40

D point =

Answer 40

Highest CO2–end tidal CO2 measurement

Question 41

DE segment =

Answer 41

Start inspiration

Question 42

Shark fin ETCO2

Answer 42

Obstructive pattern—COPD, bronchospasm

Question 43

Curare cleft

Answer 43

Early spontaneous breath

Question 44

Normal end-tidal CO2 to arterial CO2 gradient (dCO2) is ___

Answer 44

2-5 mm Hg

Question 45

ETCO2/arterial CO2 (dCO2) gradient reflects...

Answer 45

Alveolar dead space—alveoli ventilated but not perfused

Question 46

What increases dCO2?

Answer 46

Any significant reduction in lung perfusion/increases in alveolar dead space

Question 47

PaCO2 will always be ___ than ETCO2 due to ___

Answer 47

Higher, d/t mixing and dilution with the dead space gases

Question 48

Causes of increased dCO2 (7):

Answer 48

- Decreased pulmonary artery pressure - Upright posture - Pulmonary emboli (PE)—air, fat, thrombus, amniotic fluid - COPD—causes no vascular air spaces at alveolar level - Mechanical obstruction of pulmonary artery - Ventilated gas leaving normal pathway—cuff leak, tracheal disruption, bronchopleural fistula - Decreased CO or hypotension

Question 49

Causes of increased ETCO2 (9):

Answer 49

- Malignant hyperthermia - Hypoventilation - Bicarbonate - Laparoscopy (CO2 inflation) - Hyperthermia - Improved blood flow to lungs after hypotension or resuscitation - Tourniquet released - Water in capnograph sensor - Breathing circuit error—CO2 absorber exhausted, rebreathing, inadequate fresh gas flow, faulty valves in circuit

Question 50

Causes of decreased ETCO2 (9):

Answer 50

- Hyperventilation - Airway leak, leak around cuff - Decreased blood flow to lungs - Pulmonary embolism - Decreased CO, arrhythmia - Incipient pulmonary edema - Hypothermia - Inadequate sample volume - Sample catheter misplaced

Question 51

What is malignant hyperthermia?

Answer 51

Rare, inherited skeletal muscle syndrome

Question 52

MH presents as a ___

Answer 52

Hypermetabolic reaction

Question 53

MH is triggered by...

Answer 53

Exposure to volatile anesthetic gases or depolarizing muscle relaxant (succinylcholine)

Question 54

Incidence of MH

Answer 54

1/5,000-1/100,000

Question 55

Early signs of MH (11):

Answer 55

- Abrupt increase in ETCO2 - Cardiac arrhythmias - Generalized muscle rigidity - Hypoxia - Profuse sweating - Trismus/masseter muscle rigidity (MMR) - Metabolic-respiratory acidosis - Mottling of the skin - Tachycardia - Tachypnea in spontaneously breathing patients - Unstable arterial pressure

Question 56

Late signs of MH (11):

Answer 56

- Acute renal failure - Circulatory failure - Dark colored urine due to myoglobinuria - Disseminated intravascular coagulation - Elevated blood creative phosphokinase (CPK) levels - Elevated blood myoglobin levels - Hyperkalemia - Hyperthermia (> 38.8 degrees Celsius)*** - Hypotension - Rhabdomyolysis - Severe cardiac arrhythmias and cardiac arrest

Question 57

Treatment of MH

Answer 57

Dantrolene

Question 58

Initial dose of dantrolene

Answer 58

2.5 mg/kg

Question 59

Alternative to dantrolene

Answer 59

Ryanodex 2.5 mg/kg—expensive