Monitoring the Anesthetized Patient

Question 1

What is analgesia?

Answer 1

The absence of pain

Question 2

What is hypnosis?

Answer 2

Artificially induced sleep or a trance resembling sleep from which an animal can be aroused by a stimulus

Question 3

How are oxygenation and ventilation assessed subjectively?

Answer 3

Reflex activity
Eye position
Muscle relaxation
Heart rate, pulse quality and strength
Respiratory rate, volume, character
Mucous membrane color and refill time
Response to noxious stimulus

Question 4

How are oxygenation and ventilation assessed objectively?

Answer 4

ECG
Blood pressure
Hemoglobin saturation
CO2 production/elimination
Inhaled anesthetic concentration
Neuromuscular responses
EEG
Temporally processed data

Question 5

What types of equipment is used to measure oxygenation and ventilation objectively?

Answer 5

Doppler (indirect), oscillometric (indirect), or arterial catheter (direct) for blood pressure
Pulse oximeter for Hgb saturation
Capnograph for CO2 production/elimination
Train-of-four, tetanic fade for neuromuscular responses
Bispectral index from EEG, heart rate variability from ECG for temporally processed data

Question 6

What types of equipment is used to measure oxygenation and ventilation subjectively?

Answer 6

Does not require specialized monitoring

Question 7

What are the normal parameters for heart rate?

Answer 7

Dog: 60-160
Cat: 120-220
Horse: 25-45
Cow, sheep, goat: 60-80
Pig: 60-110

Question 8

What are the normal parameters for respiratory rate?

Answer 8

Dog: 20-40
Cat: 20-40
Horse: 8-10
Cow: 10-30
Pig: 12-20
Sheep, goat: 15-30

Question 9

What is the normal parameter for systolic pressure?

Answer 9

100-160 mmHg

Question 10

What is the normal parameter for diastolic pressure?

Answer 10

60-90 mmHg

Question 11

What is the normal parameter for mean arterial pressure?

Answer 11

60-80 mmHg

Question 12

Is it possible to be well oxygenated but poorly ventilated?

Answer 12

Yes, due to poor perfusion, delivery of oxygen to tissues is dependent on CO2 and arterial CO2 content. Ventilation is defined by the level of CO2.

Question 13

What are causes of pulse oximeter artifact?

Answer 13

Vasoconstriction
Probe motion
Hypotension
Large number of false alarms (probe slips out of position)
Limited placement locations
Misleading results in the face of severe anemia

Question 14

What does the ECG represent?

Answer 14

ECG produces a continuous waveform representing the summation of electrical ativity of the heart for a given axis or plane

Question 15

Is ECG a good stand-alone monitor?

Answer 15

No, it does not provide assessment of perfusion, information on cardiac pumping activity, and it is limited to its assessment of the conduction speed

Question 16

What are the differences between direct and indirect methods to measure blood pressure?

Answer 16

Indirect is non-invasive and direct is invasive

Question 17

What are the 2 methods to indirectly measure blood pressure?

Answer 17

Doppler and oscillometric

Question 18

How are doppler and oscillometric similar?

Answer 18

The both proved systolic BP and HR, they do not measure flow or perfusion

Question 19

How are doppler and oscillometric different?

Answer 19

Oscillometric also gives diastolic and mean arterial pressures, doppler does not

Question 20

What is the accuracy of any indirect blood pressure method directly related to?

Answer 20

Cuff fit

Question 21

What are the differentials for absence of a CO2 waveform following endotracheal intubation?

Answer 21

Improper ET tube placement and patency: depressed or absent capnogram may be due to a dislodged ET tube
Misplaced ET tube (place it in esophagus)
Obstructed ET tube or airway, a leak around ET tube cuff, or disconnection of the ET tube from the anesthetic machine

Question 22

What objective parameter solely defines the adequacy of ventilation?

Answer 22

Capnography

Question 23

What is the most useful subjective sign for assessing the depth of anesthesia?

Answer 23

Respiratory rate, volume, and character (gives the best indicator of ventilation)

Question 24

What are the 4 guidelines for monitoring veterinary patients advocated by the ACVA?

Answer 24

Assessment of circulation
Assessment of ventilation
Maintenance of an anesthetic record of events
Assignment of a responsible person to be aware of the patient’s status and prepared to intervene, if necessary

Question 25

What are Guedel's 4 stages of anesthesia?

Answer 25

Stage 1: Stage of voluntary movement Stage 2: stage of delirium or involuntary excitement Stage 3: Stage of surgical anesthesia Stage 4: stage of medullary depression

Question 26

Describe stage 1 of anesthesia

Answer 26

Patient is awake or asleep but arousable | This stage lasts until ataxia and the loss of righting reflex

Question 27

Describe stage 2 of anesthesia

Answer 27

Lasts from the loss of unconsciousness to the onset of regular breathing CNS is depressed Patient shows signs of exaggerated reflex activity, vocalization, swallowing, urination/defecation, dilated pupils, breath holding and/or hyperpnea, tachypnea, palpebral reflexes will be prominent, and vomiting These patients are not conscious and are not aware of what they are doing

Question 28

Describe stage 3 of anesthesia

Answer 28

Light, medium, and deep | Medium is where we want patients for surgery

Question 29

Describe light stage 3 of anesthesia

Answer 29

Spontaneous eyeball movement, may respond to toe pinch, brisk palpebral reflex present, strong jaw tone, eye rotated ventrally in ruminants

Question 30

Describe medium stage 3 of anesthesia

Answer 30

Stable respiration and pulse, abolished laryngeal reflexes, response to toe pinch, sluggish palpebral reflex, strong corneal reflex, adequate muscle relaxation, pupil is central but not dilated in ruminants, no purposeful response to noxious stimuli

Question 31

Describe deep stage 3 of anesthesia

Answer 31

Decreased intercostal muscle function, reduced tidal volume, increased respiratory rate, diaphragmatic breathing, profound muscle relaxation, weak corneal reflex, ventrally rotate pupil in ruminants, pupil sluggish or non-responsive to light

Question 32

Describe stage 4 of anesthesia

Answer 32

Do not want patients here CNS is extremely depressed and spontaneous respiration ceases The heart continues to beat for only a short time Blood pressure is low, CRT is delayed, pupils are widely dilated and nonresponsive to light, sphincter tone is lost

Question 33

What is a differential list for a tachycardic anesthetized patient?

Answer 33

``` Sympathetic stimulation Hypotension Hypovolemia Hypoxemia (early) or anemia Hypercarbia Hyperthermia Acute anaphylactoid response Drugs Electrolyte disturbances ```

Question 34

What is a differential list for a bradycardic anesthetized patient?

Answer 34

``` Excessive sympathetic depression Increased vagal tone Hypothermia Hyperkalemia Elevated intracranial pressure Hypoxemia (late) Drugs ```

Question 35

What is a differential list for a tachypneic anesthetized patient?

Answer 35

``` Sympathetic stimulation or pain Hypoxemia Hypercarbia Hyperthermia CSF acidosis Drug effects ```

Question 36

What is a differential list for a bradypneic/apneic anesthetized patient?

Answer 36

Excessive respiratory depression Recent hyperventilation Hypothermia Musculoskeletal weakness or paralysis

Question 37

Do anesthetized animals feel pain? Justify your answer based on your knowledge of neurophysiology and anesthetic action.

Answer 37

No, pain is a conscious experience and the anesthetized animal is unconscious. However, adequate analgesia will reduce physiologic and autonomic response (non-purposeful movement) to noxious stimuli (movement occurring at the level of the spinal cord not brain) which anesthesia does not have control over