DM1 Pt5-2 Monitoring the Cardiovascular System

Question 1

Why is manual assessment of the patient still important despite using automated monitoring equipment?

Answer 1

Manual assessment confirms the accuracy of the data from the monitoring equipment and ensures a double-check on the patient’s status.

Question 2

Why is a graphical monitoring record recommended during anesthesia?

Answer 2

A graphical record makes it easier to observe trends in monitored variables over time, allowing for earlier detection of potential problems.

Question 3

What can manual measurement of pulse rate and quality indicate during anesthesia?

Answer 3

Elevated heart rate can indicate inadequate anesthesia, hypotension, sympathetic stimulation, or drug effects, while a decrease in heart rate can indicate deep anesthesia, parasympathetic stimulation, or hypoxia.

Question 4

Why is palpation of peripheral pulses helpful in assessing cardiovascular status during anesthesia?

Answer 4

Changes in pulse quality due to hypotension are detected earlier in peripheral pulses, such as the lingual or dorsal pedal artery, allowing for earlier intervention.

Question 5

What is an oesophageal stethoscope, and how is it used during anesthesia?

Answer 5

An oesophageal stethoscope allows remote monitoring of heart and respiratory sounds. It is inserted into the esophagus after intubation and advanced to the base of the heart to detect heart and respiratory rates.

Question 6

What are the advantages of using an oesophageal stethoscope?

Answer 6

• Cheap to buy
• Easy to place
• Soft tube unlikely to cause damage
• Allows remote monitoring of heart and respiratory rate

Question 7

What are the limitations of an oesophageal stethoscope?

Answer 7

It does not provide information on cardiac output and can increase the risk of regurgitation if inserted into the stomach.

Question 8

What does electrocardiography (ECG) monitor during anesthesia?

Answer 8

ECG monitors the electrical activity of the heart, allowing detection of abnormalities in heart rate and rhythm.

Question 9

How is a three-lead ECG set up in cats during anesthesia?

Answer 9

Electrodes are placed on the pads of the left and right forelimbs and the left hind limb, with ECG channels generated by the difference in voltage between these electrodes.

Question 10

Why should pulse monitoring be done in addition to ECG monitoring?

Answer 10

A normal ECG does not guarantee normal heart contraction, as electrical activity can continue after the heart stops beating. Pulse monitoring ensures the heart is still pumping blood.

Question 11

What does pulse oximetry measure in veterinary anesthesia?

Answer 11

Pulse oximetry measures the haemoglobin saturation with oxygen in arterial blood, providing information about oxygenation and detecting hypoxaemia.

Question 12

How does a pulse oximeter work?

Answer 12

A pulse oximeter uses LEDs that emit red and infrared light to measure the absorption of oxygenated and deoxygenated haemoglobin. The ratio of light absorption is used to calculate the oxygen saturation of haemoglobin, and it requires detection of a pulse to work accurately.

Question 13

What is the significance of a haemoglobin saturation below 90%?

Answer 13

Saturation below 90% indicates a problem with oxygen delivery to the tissues, as there is a steep decline in the oxygen carried in the blood once saturation falls below this level, increasing the risk of hypoxia.

Question 14

At what haemoglobin saturation level should action be taken to prevent hypoxia?

Answer 14

Action should be taken when saturation falls to 94-95% to prevent hypoxia.

Question 15

What are the advantages of using pulse oximetry during anesthesia?

Answer 15

• Non-invasive tool
• Easy to use
• Inexpensive
• Provides valuable information on oxygenation status, helping detect physiological disturbances leading to hypoxaemia

Question 16

What are the disadvantages of pulse oximetry?

Answer 16

• Frequent alarms can be ignored
• Probes work best on the tongue and may give unreliable readings on thick or hairy tissues
• Probe pressure can reduce blood flow, causing inaccurate readings
• Hypotension and pigmented tissues can affect accuracy
• Not useful in anaemic cats

Question 17

Why might a pulse oximeter fail to give an accurate reading if the probe is placed improperly?

Answer 17

Excessive pressure from the probe can reduce arterial blood flow, leading to falsely low readings or no reading. Moving the probe to a different site can solve this issue.

Question 18

Where are common sites for placing pulse oximeter probes in cats?

Answer 18

The most common site is the tongue, but other sites include the ear, prepuce, vulva, nipple, or flank skin fold.

Question 19

What are reflectance probes, and where are they used?

Answer 19

Reflectance probes contain both LEDs and a photodiode and are designed for placement in anatomical canals such as the esophagus or rectum.

Question 20

How does a plethysmograph in some pulse oximeters help monitor cardiac output?

Answer 20

A plethysmograph shows changes in arterial pulse volume with each pulse beat. A flattening of the plethysmograph trace can indicate a reduction in cardiac output.

Question 21

What are the three values obtained during blood pressure measurement?

Answer 21

• Mean blood pressure: Reflects blood flow at the tissue level.
• Systolic blood pressure: Peak pressure during ventricular contraction (systole).
• Diastolic blood pressure: Lowest pressure during heart filling (diastole).

Question 22

What is direct arterial blood pressure measurement, and why is it the gold standard?

Answer 22

Direct measurement involves placing a catheter in a peripheral artery connected to a transducer. It is the gold standard due to its accuracy and continuous, automatic monitoring of systolic, diastolic, and mean arterial pressure.

Question 23

What are the challenges of direct blood pressure measurement in cats?

Answer 23

Placing an arterial catheter is technically difficult due to the small size of peripheral arteries, and the catheter can easily become dislodged or blocked.

Question 24

What is Doppler ultrasonographic blood pressure measurement?

Answer 24

Doppler ultrasound uses a probe to detect blood flow in a peripheral artery, combined with a cuff to occlude blood flow. The pressure at which blood flow is first heard during cuff deflation equals the systolic blood pressure.

Question 25

Where can the Doppler probe and cuff be placed for blood pressure measurement in cats?

Answer 25

• Forelimb: Doppler probe on the common digital artery, cuff on the radius.
• Hindlimb: Probe on the tarsal artery, cuff above the hock.
• Tail: Probe on coccygeal artery, cuff at the base of the tail.

Question 26

How does oscillometric blood pressure measurement work?

Answer 26

Oscillometric devices use a cuff that is inflated and deflated automatically. Pulsations in the artery cause oscillations in cuff pressure, which are used to determine systolic, mean, and diastolic pressures.

Question 27

What is the ideal cuff size for blood pressure measurement in cats?

Answer 27

The width of the cuff should be 40% of the limb’s circumference at the site of placement.

Question 28

What is the main advantage of oscillometric blood pressure measurement compared to Doppler?

Answer 28

Oscillometric devices are automated and can measure systolic, diastolic, and mean blood pressure, making them easy to use and convenient during anesthesia.

Question 29

What is a disadvantage of Doppler blood pressure measurement compared to oscillometric methods?

Answer 29

Doppler only measures systolic blood pressure, and it is labor-intensive, requiring manual operation by the anesthetist.

Question 30

Why is cuff placement important in both Doppler and oscillometric blood pressure measurements?

Answer 30

Proper cuff placement (40% of limb circumference) is essential for accurate readings; a cuff that is too wide will underestimate blood pressure, while a cuff that is too narrow will overestimate it.