L&J Chp 4 Monitoring Anesthetized Patients

Question 1

PaCO2

Answer 1

• Measure of the effective alveolar minute ventilation

- Normal: 35-45mm Hg

Question 2

How anesthesia changes PaCO2

Answer 2

Values may be higher in anesthetized patients with up to 60-80 mm Hg in horses and cattle

Question 3

PaCO2 >60mm Hg

Answer 3

• May be associated with excessive respiratory acidosis

- Usually considered to represent sufficient hypoventilation –> warrants PPV

Question 4

PaCO2 <20 mm Hg

Answer 4

• Associated with respiratory alkalosis

- Decreased cerebral blood flow –> may impair cerebral oxygenation

Question 5

Causes of hypocapnia/hyperventilation

Answer 5

1. Light level of anesthesia
2. Hypoxemia
3. Hyperthermia
4. Hypotension
5. Inappropriate ventilator settings
6. Early pulmonary parenchymal disease

Question 6

Postop Causes of Hypocapnia/Hyperventilation

Answer 6

1. Excitement stage of recovery
2. Delirium
3. Pain
4. Distended urinary bladder
5. Sepsis

Question 7

Causes of hypercapnia/hypoventilation

Answer 7

1. Excessive depth of anesthesia
2. NM disease
3. Airway obstruction
4. Pleural space-filling disorder
5. Late pulmonary parenchymal disease
6. Inappropriate ventilator settings
7. Malfunctioning anesthetic machine

Question 8

Malfunctioning/incorrectly used anesthetic machine causing hypercapnia/hypoventilation

Answer 8

• Unidirectional gas flows stuck
• Absorbent exhaustion
• Low FGF with non-rebreathing circuits

Question 9

What are the two types of capnometry?

Answer 9

1. Time capnometry (time:PCO2)

2. Volume capnometry (volume:PCO2)

Question 10

Capnometry

Answer 10

• Measure of CO2 in the respiratory gases

Question 11

Methods of measuring gaseous carbon dioxide

Answer 11

1. Infrared light absorption (most common)
2. Raman spectroscopy
3. Mass spectroscopy

Question 12

Infrared light absorption

Answer 12

Absorption is proportional to the partial pressure of the gas

Question 13

Raman spectroscopy

Answer 13

• Monochromatic argon light beam passed through the gas sample
• Light is absorbed, re-emitted at a different wavelength that is specific to the gas molecule that absorbed it

Question 14

Mass Spectroscopy

Answer 14

• Based on separation of various gas species by an electron beam in an magnetic field
• Expensive, bulky, not commonly used in clinical practice

Question 15

Time capnography

Answer 15

• PCO2 expressed as a function of time during the respiratory cycle
• Used to verify correct ETT placement, CPR, assess adequacy of ventilation

Question 16

Volumetric (Volume) capnography

Answer 16

• plots expired CO2 against time

Question 17

What can the volumetric capnography determine?

Answer 17

VT
Anatomic, alveolar, physiologic dead space 
Effective alveolar VT 
ETCO2, PaCO2 
eliminated CO2 volume 
Mixed-expired CO2

Question 18

Volumetric capnography: flattening of curve

Answer 18

AKA less steep phase II coupled with less plateaued phase III
Suggests increased physiologic deadspace either due to lower airway obstructive disease or to increased alveolar headspace ventilation (PTE, hypovolemia)

Question 19

What would cause the volumetric capnography waveform to drop to zero?

Answer 19

Accidental extubation

Cardiac arrest

Question 20

What effect does PPV have on the volumetric capnography waveform?

Answer 20

May either flatten the slope due to increased alveolar dead space ventilation or normalize the slope due to recruitment of collapsed lung units

Question 21

What are the four phases of a capnograph waveform?

Answer 21

Phase 1 - inspiratory baseline
Phase 2 - transitional phase/expiratory upstroke
Phase 3 - expiratory plateau/alveolar gas
Phase 0 - inspiratory down stroke

Question 22

Significance of the alpha angle

Answer 22

Change from airway gas to alveolar gas
Normal 100-110*
Increased angle - airway obstruction, VQ mismatch

Question 23

Significance of the beta angle

Answer 23

ETCO2/max alveolar CO2 concentration
Normal approx 90*
Increased by rebreathing

Question 24

Characteristics Light Plane Anesthesia

Answer 24

Central eye position
\+ Palpebral 
Medium to large pupil size 
\+ PLR
Moist corneas
Lots of eyelid/mandibular muscle tone 
\+/- reflex movement response to nociception
\+ physiologic response to nociception

Question 25

Characteristics Light-Medium Plane of Anesthesia

Answer 25

``` Rotated ventromedial position Absent palpebral Small to medium pupil size +PLR Moist corneas Some eyelid/mandibular muscle tone No reflex movement response to nociception +/- physiologic response to nociception ```

Question 26

Characteristics Deep-Medium Plane of Anesthesia

Answer 26

``` Rotated ventromedial position Absent palpebral Medium to large pupil size Absent PLR Intermediate corneas Little eyelid/mandibular muscle tone No reflex movement or physiologic response to nociception ```

Question 27

Characteristics Deep Plane of Anesthesia

Answer 27

``` Central eye position Absent palpebral Large pupil size Absent PLR Dry corneas No eyelid/mandibular muscle tone No reflex movement or physiologic response to nociception ```

Question 28

Physiologic response to nociception

Answer 28

Increase in HR, BP, respiratory rate

Question 29

Primary focus of monitoring anesthetized patients is the assessment of:

Answer 29

1. depth of anesthesia 2. CV, pulmonary consequences of the anesthetized state 3. Temperature

Question 30

Consequences of a too light level of anesthesia?

Answer 30

Failure to achieve all of the basic goals of anesthesia

Question 31

Consequences of too deep level of anesthesia?

Answer 31

May suffer from adverse cardiopulmonary consequences and death

Question 32

What are the cardiovascular system parameters subdivided into?

Answer 32

- Preload (is the pump being sufficiently primed?) - Heart parameters (is the pump pumping) - Forward flow parameters (are the tissues being perfused)

Question 33

How many stages of anesthetic depth are there?

Answer 33

Four planes