Test 2: 27 cardiovascular Flashcards
what range of blood pressure can organs autoregulate? and which organs do this?
brain, heart, kidney
601-160 MAP
how to measure HR
Stethoscope (external or esophageal)
* Direct measure of heart rate
* Arrhythmias and murmurs audible
Doppler monitor
* Direct measure pulse rate
Pulse Oximetry
* Pulse rate measured
Direct arterial pressure
* Pulse rate measured
ECG
* Electrical rate- may not correlate with generated pulses
DAP— mmHg needed for adequate cardiac perfusion
> 40
how to calculate MAP
Mean=diastolic + 1/3 (systolic-diastolic)
Pressure (mean)=Flow (CO) x —
resistance (SVR)
can have good pressure from constricting vessels but the resistance can be too high for actual flow, need a balance
Hypotension (MAP < —mmHg, SAP < — mmHg)
60
80
Ideally want to keep MAP> 80, SAP >100
two non invasive BP devices
- Doppler Ultrasound
- Oscillometric
two invasive ways to measure BP
- Pressure Transducer
- Simple Aneroid Gauge Method
how does doppler work
ultrasonic crystal probe has two crystals: one for transmitting ultrasonic waves and one for detecting reflected waves
Arterial blood flow is detected and reflected wave frequencies are converted to an audible signal
doppler readings in cats and dog where you should intervene
- Dogs doppler < 100mm Hg
- Cats doppler < 80 mm Hg
how does oscillometric determine BP
measures Mean and then calculates systolic and diastolic via an algorithm
S/D may be different then if you have a direct measurment
some factors that affect accuracy of non invasive BP
Cuff Size
Site-as cuff moves distally systolic increases and diastolic decreases
Arm position-cuff should be at level of heart
ARRHYTHMIAS?
Artifacts from motion are possible: shivering, trembling
Non invasive BP decreases in accuracy with
extremes of pressure: very hypo or hypertensive
very high or very low HR
what are some disadvantages of non invasive BP
not continous measurements- difficult to detect rapid changes
Clinical limitations:
* Decreased accuracy with extremes of BP and HR
* Not appropriate for critical patients
* Not appropriate when significant surgical complications are anticipated
(hemorrhage)
* Depending on brand may be less reliable in patients less than 10 kg (cats)?
benifits of invasive BP
- accurate
- directly measures systolic and diastolic- mean is calculated
- Wave form is produced which can provide additional information about CV function: pulse contour often correlates with CO
- continous real time readings
how does invasive BP work
- A column of fluid is directly connected between the arterial system and a pressure transducer
- Pressure waveform of arterial pulse is transmitted via the fluid to the transducer
- waveform is converted to electrical signal
- Signal is processed, amplified and converted into a visual display on a monitor
arterial pressure wave from invasive BP
what is damping of invasive BP
underdamping- gives you too high readings
overdamping- falsely low readings
simple aneroid gauge
inexpensive way to measure invasive BP
only gives MAP- no SAP or DAP
how does central venous pressure work
- way to measure preload
- assess response to fluid therapy
- pressure is measured in the cranial vena cava just proximal to the right atrium- estimates R atrial pressure
- makes a waveform that can provide additional info about cardiac function
what is the bottom line
CVP (central venous pressure) waveform
— can cause increased CVP valves
cardiac disease can cause falsely high CVP values
to measure CVP you need to consider cardiac output
what is pulse pressure variation
change between diastolic and systolic from beat to beat
measure of fluid responsiveness
Pulse Pressure Variation > 15 % can indicate decreased preload (volume responsive)
how to measure stroke volume
hard to do- need special imaging
echo, CT, MRI
what are some physical signs that show afterload
afterload = systemic vascular resistance
increased afterload will decrease SV
pale= constricted, red= dilated
CRT < 1 s vasodilated, >2s vasoconstricted
Temp: cold constricted, warm dilated
what are some ways to measure cardiac output
Fick- indirect NICO
thermodilution
Lithium dilution
arterial waveform analysis
echo
capnography
