ECG, Ventilation, Blood pressure Flashcards
Electrocardiography means
Is the graphic representation of the electrical activity of the heart as it travels through the cardiac conduction system and heart muscle
Sinoatrial node –> internodal tracts –> atrioventricular node –>
bundle of His –> bundle branches –> Purkinje fibers
Why are ECGs preformed
1.To determine a heart rate
2. Assess cardiac rhythm
◦ You need to differentiate normal from abnormal and dangerous from harmless rhythms
3. Show conduction abnormalities
4. Aids in the treatment of cardiac arrest
What does a complete complex in an ECG look like
This complete complex represents a single heartbeat
*How long the electrical impulse takes is shown on the horizontal axis in
seconds
*The “amount” of electricity is shown on the vertical axis
* It is measured in millivolts (mv)
* The baseline is 0 mv
What does a normal heartbeat look like in an ECG
Each part of the cardiac cycle is represented by a part of the normal ECG
reading and is described by the P- QRS-T complex
The P-QRS-T complex, as
demonstrated on lead II is as follows:
P-wave: depolarization
(contraction) of the atria
QRS complex: depolarization (contraction) of the ventricles
◦ Usually positive in small animals*
◦ Negative in large animals
T-wave: repolarization
(preparation for next contraction) of the ventricles
◦ Can have either a positive (pointing up) or a negative (pointing down) wave deflection as long as it doesn’t fluctuate on the same rhythm strip
What is the general route of the depolarizing wave in a heart
◦ Cranial to caudal
◦ Right to left
◦ Dorsal to ventral
How do you measure a depolarizing wave
If the depolarizing wave is moving in one direction relative to the way it is being measured, it may be measured as positive
*If the depolarizing wave is moving in the opposite direction relative to the way it is being measured, this may be measured as negative
What does the vet ECG have
Gives a positive deflection of the P and R waves in the normal small animal ECG
*Records the strongest positive reading because it looks at the electrical activity of the heart in the direction of the wave of depolarization
What does the vet tech do for the ECG
Heart rate and rhythm are the most valuable pieces of information that can be collected from an ECG
*As a VT, you will be responsible for hooking the animal up to the electrodes and the machine, calibrating the machine, and printing the record and/or putting it in the patient file
*Like a radiograph, you need to know enough to make a judgment about whether or not you have produced a record that is of diagnostic quality or whether you need to repeat the procedure
*You will obtain the paper tracings and record all relevant patient information on the tracing (the ECG rhythm strip is part of the legal medical record)
*You do need to know if abnormalities in the tracing are due to patient abnormalities or pathologies or due to patient positioning, movement, mechanical interference etc.
*If using the ECG to monitor a patient under anesthesia, you do need to be able to calculate heart rate and to recognize a normal rhythm
*You also need to know when there is an abnormal rhythm (arrhythmia) so appropriate treatment can be started to prevent death
How does a 50mm/sec paper work and for what species
Used for smaller animals as they have faster heart rates
Spreads the complexes out so more detail can be seen
Each small box is 0.02 seconds
Each large box is 0.1 seconds
How does 25mm/sec paper work and is used for what species
Used on larger animals with slower heart rates
Compresses the complexes
Half the speed so it takes twice as
long to cover the same distance
Each small box is 0.04 seconds
Each large box is 0.2 seconds
How to determine the HR with a 25mm/sec paper
Divide 1500 by the number of small boxes between two R’s to get beats per minute
* Small box = 0.04 seconds
How to determine a HR using 50mm/sec paper
- Divide 3000 by the number of small boxes between two R’s to get beats per minute
- Small box = 0.02 seconds
how to calculate irregular rhymes using ECG paper
- Calculate an average
- Count the number of QRS complexes in a predetermined time period and multiply by the factor
- Most common is 6 seconds
What is a normal HR of a dog
Small Dog: 80 – 140 bpm
◦ Large Dog: 60 – 120 bpm
What is a normal HR for felines
180 – 220 bpm
◦ Heart rate is usually lower at home
What is a normal HR for bovine
Bovine:
◦ Calf: 60 – 100 bpm
◦ Adult: 60 – 80 bpm
What is a normal HR for equine
Equine:
◦ Foal: 80 – 120 bpm
◦ Adult: 28 – 40 bpm
What should a normal rhythm look like
“Is there a P for every QRS and a QRS for every P?”
*Determines that the heart is:
* Depolarizing normally
* Controlled by the sinoatrial (SA) node
This is referred to as:
normal sinus rhythm
What does sinus arrhythmia look like
- Heart rate coordinated with respirations
- Decreases during expiration
- Increases during inspiration
- Normal in dogs, horses, and cattle
- Abnormal in cats
Sinus bradycardia is
Abnormally slow HR
Sinus tachycardia is
Abnormally fast HR
AV block looks like
Delay or interruption in conduction of the electrical impulse –results in slower than normal heart rate
Three types
What does a first degree AV block look like
prolonged PR interval
◦ Can be normal in resting horses or in animals under anesthesia
◦ Also seen in animals with hyperkalemia or cardiac disease
What does a second degree AV block look like
occasional missing QRS complexes
◦ Can be normal in resting horses or in animals under anesthesia
◦ Also seen in animals with hyperkalemia or cardiac disease
What does a third degree AV block look like
random PR intervals
◦ NOT NORMAL, requires treatment
What are premature complexes
Complexes that appear earlier than they should if normal conduction paths are followed
What does a premature supraventricular complexes look like
One or more normal QRS complexes closely following the previous QRS complex
◦ Usually have narrower, more normal-looking complexes
◦ P wave abnormalities or absent P waves
https://www.youtube.com/watch?v=I1lyBZR82dQ
What does a premature ventricular contraction/complexes look like
Usually appear as a very wide complex closely following the previous QRS complex
What does atrial fibrillation look like and what causes it
Irregularly irregular ventricular rhythm
* Irregular R-R intervals with no predictable pattern
* QRS morphology is normal
*Atria beat irregularly
* Extremely rapid contraction of the atria in various small portions of the
atrial wall at any one time
* Normal to fast rate
*Seen as fine undulations
of the baseline
*No P waves
What does ventricular fibrillation look like
Extremely rapid contraction of the ventricles in various small portions of the ventricular wall at any one time
*Results in a very rapid but ineffective ventricular rate that produces NO PULSE
*Will die very quickly if CPR or electrical defibrillation is not attempted immediately
*Undulating baseline
*Absence of QRS complexes
What are the common industry standards for performing an ECG on a SA
Place patient in right lateral recumbency on a non-metallic surface/mat and in a quiet room
When using the ECG to monitor during surgery, procedure may dictate positioning
Cats and dogs can also be placed in sternal
Nearby electrical equipment should be unplugged
This is to reduce 60-cycle electrical interference
Limbs should be separated by a non-conductive material like a towel or paper towel
Connect alligator clips to the skin
Place a small amount of electrode gel or alcohol at the connection sites
For long-term monitoring
Clip fur and use sticky pads
As in human ECGs
OR
Pass electrode wire directly through the skin
Push a 20 G needle through skin, pass the electrode wire through needle, remove needle and secure wire with tape
Where should you clip each ECG lead
Clip leads to the skin in 4 places
Red – left hind leg
Green – right hind leg*
White or Yellow – right foreleg
Black – left foreleg
Forelimb clips:
- Attach just proximal to the olecranon
Hindlimb clips:
- Attach just cranial and proximal to the stifle
What are the most commonly placed leads and where
Although there are 6 leads, Lead II, is the most commonly used in veterinary medicine
Performed in a standing position
Lead placement:
Many variations depending on clinician, geographical location, equipment available
Most commonly used:
Left arm electrode (+) – near left ventricular apex (left thorax, near elbow)
Right are electrode (-) – in the lower third of right jugular furrow or over the right shoulder
Ground electrode (N) – anywhere removed from the heart (ex: left shoulder, right dorsal neck area)
Importance of Respiratory Ventilation in Anesthesia and the Technologist
Typically, the normal alveolar respiratory ventilation is done unconsciously to maintain constant arterial blood gas tension (particularly CO2)
Anesthesia and drugs can interfere with this unconscious mechanism. It is the responsibility of the person who is monitoring the patient to be able to recognise these changes and act accordingly. With a good understanding of respiratory physiology and knowledge on how the machines/systems being used work, then handling the issues interfering with the body’s unconscious mechanism can be controlled.
What is the Physiology of Respiration
Takes place in the medulla oblongata or “respiratory center”
2 main systems that control breathing are:
Mechanical Control
Chemical Control
What is the mechanical control of respiration
Nerve impulses that respond when the lungs are fully inflated and deflated
These are autonomic pre-set levels
Prevent over-inflation
Ensure proper amounts of exhalation
This system’s control is to maintain a normal, rhythmic, resting breathing pattern
What is the chemical control for respiration
There are chemical receptors within blood vessels that monitor physical and chemical characteristics of the blood
The 3 characteristics that affect breathing processes are
CO2 content
Blood pH
O2 content
CO2 and blood pH work together to notify the control center
Note: severe hypoxia can cause the respiratory center to fail due to neuron depression and may cause a decrease or arrest of breathing
What are some common resp monitors for anesthesia
Capnography
Side stream Sampling
Mainstream Sampling
Pulse Oximetry
