Assessment of CRS Function Flashcards
What is the function of the cardiovascular system?
-To deliver oxygenated blood to the tissues
-and to remove carbon dioxide
Identify the benefits of monitoring earlier in the cardiorespiratory system
Accurate measures of blood pressure, heart function (contractility & HR), lung function and breathing
Identify the benefits of monitoring later in the cardiorespiratory system, and outline some limitations of this
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?
List the methods of measurement of oxygen delivery
Tissue perfusion
Blood oxygen content
Outline the methods of measurement of tissue methods
It is driven by MAP
MAP measured by:
Pulse
Invasive measurement
Non invasive measurement
Outline the invasive measurement of arteriole blood pressure (measuring tissue perfusion)
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
Outline the non-invasive measurement of arteriole blood pressure
(measuring tissue perfusion)
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
Outline the importance of measuring Central Venous Pressure (CVP)
(measuring tissue perfusion)
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
Outline the methods of measuring cardiac output
(measuring tissue perfusion)
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
Outline how ECG is used to evaluate cardiac function
(measuring tissue perfusion)
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
Explain the concept of blood oxygen content and how it is assessed
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
- Pulse oximetry
- Blood gas analysis
Outline the methods o which oxygen is carried throughout the body and how this links to overall oxygen content
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)
Outline how a pulse oximeter is used to measure oxygen content in haemoglobin
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
Discuss some of the limitations of using a pulse oximeter
Measure saturation of Hb with oxygen
Oxygen carrying capacity
Doesn’t indicate anaemia
How many red cells are there?
Assisted oxygenation
Smoke inhalation
Explain how oxygen in blood content is estimated from the mucous membrane colour
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)
Explain how blood gas analysis is used to measure oxygen found within a solution
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
How does a blood gas analyser help with diagnosis?
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.
Explain how oxygen and carbon dioxides are linked with regards to transportation around the body
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
Describe how CO2 is measured
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
List other methods of monitoring pulmonary systems
○ Monitor breathing rate, rhythm, nature and effort
○ Observe rebreathing bag (anaesthetic circuit) and chest excursions
○ Watch patient closely
○ Ventilometer or respirometer available
List the areas of the patient which will provide indication of pulmonary issues
Mucous membrane colour (grey/white, congested/red, purple)
Capillary refill time (CRT)
Toe-web/core temperature
Urine output
