Assessment of CRS Function

Question 1

What is the function of the cardiovascular system?

Answer 1

-To deliver oxygenated blood to the tissues
-and to remove carbon dioxide

Question 2

Identify the benefits of monitoring earlier in the cardiorespiratory system

Answer 2

Accurate measures of blood pressure, heart function (contractility & HR), lung function and breathing

Question 3

Identify the benefits of monitoring later in the cardiorespiratory system, and outline some limitations of this

Answer 3

Advantages of monitoring late in the chain
Tells us the whether the whole system is working

Disadvantages
If not working, where has it gone wrong?

Question 4

List the methods of measurement of oxygen delivery

Answer 4

Tissue perfusion
Blood oxygen content

Question 5

Outline the methods of measurement of tissue methods

Answer 5

It is driven by MAP

MAP measured by:
Pulse
Invasive measurement
Non invasive measurement

Question 6

Outline the invasive measurement of arteriole blood pressure (measuring tissue perfusion)

Answer 6

AKA direct

-Insert a cannula into a peripheral artery
-Connect cannula to transducer
-Reported as systolic/diastolic (mean)

Real time - beat by beat
Gives more information from trace
More accurate

Question 7

Outline the non-invasive measurement of arteriole blood pressure

(measuring tissue perfusion)

Answer 7

Sphygmomanometry
-inflation of a cuff
Oscillometric
- blood pressure cuff around its leg,
Doppler
-probe placed on clipped area of where we can feel pulse (paw/tail) we get a whooshing sound out of microphone

Question 8

Outline the importance of measuring Central Venous Pressure (CVP)

(measuring tissue perfusion)

Answer 8

CVP measures pressure of blood returning to the right side of the heart

Usually reflects the volume of blood returning – i.e. is circulating volume OK?

Often used in critical care patients

Not common in small animal practice

Question 9

Outline the methods of measuring cardiac output

(measuring tissue perfusion)

Answer 9

Rarely used in veterinary medicine (except research settings). Can use Fick method, dye, thermodilution, bioimpedance, pulse contour analysis, lithium

Cardiac output is product of stroke volume and heart rate

Question 10

Outline how ECG is used to evaluate cardiac function

(measuring tissue perfusion)

Answer 10

Heart rate and rhythm
Continuous ECG

-Paper trace – measure complex sizes
-Holter monitor (type of device an animal can wear for sustained period of time where data can then be downloaded)
-Multiparameter monitor (GA/ICU)
Measures other parameters at same time

Question 11

Explain the concept of blood oxygen content and how it is assessed

Answer 11

Shows effective lung function

Shows effective ventilation

Assessed globally by:
1. Mucous membrane colour
reflection of colours within the practice can alter colour of mucus mebranes / drugs can cause change of colour

2. Pulse oximetry
3. Blood gas analysis

Question 12

Outline the methods o which oxygen is carried throughout the body and how this links to overall oxygen content

Answer 12

Oxy in haem - pulse oximeter to measure
Oxy in solution - blood gas analysis to measure

Can take values of both and add into the equation to work out overall content

Oxygen content = (O2 carried by Hb) + (O2 in solution)

Question 13

Outline how a pulse oximeter is used to measure oxygen content in haemoglobin

Answer 13

use 2 wavelengths of light to measure oxygenate haemoglobin, measures pulse rate/strength too

Tells us how well the haemoglobin is saturated with oxygen

Sends two different wavelengths of light across the pulsatile bed and the amount of oxyhaemoglobin is calculated at those two different wave lengths and presents percentage saturation on our device

Question 14

Discuss some of the limitations of using a pulse oximeter

Answer 14

Measure saturation of Hb with oxygen

Oxygen carrying capacity
Doesn’t indicate anaemia
How many red cells are there?

Assisted oxygenation

Smoke inhalation

Question 15

Explain how oxygen in blood content is estimated from the mucous membrane colour

Answer 15

CYANOSIS (blue/cyan colour = serious problem)

-Indicates deoxygenated haemoglobin (NB light type and intensity & observer skill)

-NB importance of anaemia – need 5mg/dl unoxygenated Hb for cyanosis to be observed

-Normal animal (15g/dl Hb, shows cyanosis at 67% saturation)

-If animal is anaemic – cyanosis is not reliable sign of hypoxamia
(PO2 driving pressure will have fallen to lethal levels before Hb is sufficiently desaturated to show cyanosis)

Question 16

Explain how blood gas analysis is used to measure oxygen found within a solution

Answer 16

Measure the pp of oxygen in a solution

Cannula in an artery removing some of the blood and measure the pressure asserted by molecules in solution

Machine evaluates:
pH
HCO3
PaCO2
PaO

Question 17

How does a blood gas analyser help with diagnosis?

Answer 17

Arterial blood pressure can prove to be acidemia or alkalemia.

With acidemia an increase in the partial pressure of CO2 links to respiratory acidosis. A decrease in hydrogen carbonate ion links to metabolic acidosis.

With alkalemia a decrease in the partial pressure of CO2 links to respiratory acidosis. An increase in hydrogen carbonate ion links to metabolic acidosis.

Question 18

Explain how oxygen and carbon dioxides are linked with regards to transportation around the body

Answer 18

O2 & CO2 transport are integrated

Acidity of the tissues encourages O2 unloading

Release of CO2 in lungs facilitates O2 uptake (Bohr)

Release of O2 favours CO2 uptake in carbamino mechanisms (Hb becomes a weaker acid and better buffer) (Haldane)

Hb acid forms flip flop from one form to another

Question 19

Describe how CO2 is measured

Answer 19

In normal circumstances metabolic rate doesn’t alter much, so ventilation determines arterial CO2

Arterial CO2 therefore tells us about ventilation

CO2 is very soluble so the CO2 in the alveolar space is a good approximation of arterial CO2

CO2 in the exhaled breath can be measured by capnography

Normal should be 35-45 mmHg

Relates ventilation and cardiac output

Question 20

List other methods of monitoring pulmonary systems

Answer 20

○ Monitor breathing rate, rhythm, nature and effort

○ Observe rebreathing bag (anaesthetic circuit) and chest excursions

○ Watch patient closely

○ Ventilometer or respirometer available

Question 21

List the areas of the patient which will provide indication of pulmonary issues

Answer 21

Mucous membrane colour (grey/white, congested/red, purple)
Capillary refill time (CRT)
Toe-web/core temperature
Urine output