1. Blood Pressure Monitoring Flashcards
What is the veterinary nurses role?
Have technical skills to accurately asses BP
understand the advantages and disadvantages of diff monitoring techniques
recog abnormal values and understand their implications
know when to alert the clinician who is managing the patient
What is blood pressure?
Part of minimum baseline, emergency care, ICU, and anesthesia
We use it for patients w/ known or suspected hypertension or hypotension
BP is the product of systemic vascular resistance (the smooth muscle tone of the blood vessels)
Cardiac output (pumping action of the heart)
Circulating arterial blood volume (body water volume)
Required to drive tissue perfusion -> oxygenation
What is systolic arterial pressure?
SAP - when L ventrical contracts, blood is pushed into aorta and this creates SAP
What is diastolic arterial pressure?
DAP - as the L ventricle fills again, the aortic pressure falls; the residual (resting) pressure in the aorta is the DAP
What is the mean arterial pressure?
MAP - is calculated from systolic and diastolic pressures
MAP = DAP + 1/3(SAP-DAP)
80+1/3 (120-80)
80+1/3 (40)
80 + 13.33
=93
What is the normal VP values in dogs?
SAP 80-140mmHg
DAP 45-80mmHg
MAP 60-100mmHg
Low end is ABSOLUTE cut off. Risk of shock below these values
What is the normal BP of cats?
SAP - 80-140mmHg
DAP 55-75mmHg
MAP 60-100mmHg
What is the window allowed to respond with a low BP?
10mmHg
Report is systolid <90mmHg
Diastolic <55mmHg
Mean <90mmHg
Acceptable pressures under general anes are lower due to the nature of drugs that cause vasodilation and cardiac depression
How is hypotension diagnosed?
Is made based on the patient’s presentation, PE, and BP measurement
In K9/cats, MAP is preferred value used for making dx of hypotension
Patient is hypotensive when MAP is <60mmHg, SAP is <80-100mmHg
Follow with brief physical assessment of patient
notify clinician of patient status
Note: renal perfusion is compromised with MAP <65mmHg
at what lvl is renal perfusion compromised?
With MAP <65 mmHg
How do we diagnose hypertension?
Can be primary or secondary
There are many 2ndary causes including underlying dz (kidney dz, cushing’s, heart dz, drugs)
dx based on sustained high BP readings on 3 separate occasions
DOGS: SAP/DAP >150/90mmHg
CATS: SAP >150 mmHg
Follow with brief physical assessment of patient
notify clinician of patients status
What is false hypertension? How is it diagnoses?
White coat syndrome
Caused by stress, anxiety, fear ex the car ride, vet office scents, “white coat”(doctors get rid of lab coats), handling
This results in sympathetic response
Can result in a false diagnosis of hypertension, elevated HR and RR
How can we eliminate false hypertension?
- Calm patient in a quiet exam room for 5-10min
- Get pet to become familiar w/ you by treats and GENTLE play
- Only measure BP after patient is acclimatized to clinic setting
- Measure HR at same time as BP reading - presence of tachycardia in association w/ hypertension should prompt consideration of white coat hypertension
- once ready, take 3 readings and average them
- repeat 3 more readings if possible
What are the 2 types of BP monitoring
Direct arterial BP monitoring and indirection arterial BP monitoring
What are some things to know about direct arterial BP monitoring
gold standard, most accurate, much more invasive, higher risk, specialized equipment and training needed
What are some things about indirect arterial blood pressure monitoring to know?
Non-invasive BP (NIBP)
Measure pressures in a peripheral artery
doppler or oscillometric
less accurate
tends to understimate actual BP
What is Direct arterial BP?
DABP measurement is most accurate method
Place cath into an artery (palpate for pule, common places are dorsal pedal artery and femoral artery)
cath is connected to monitor via transducer equipment (saline filled tubing) transducer converts mechanical fluctuations in the fluid to an electrical signal
Monitors displays pulse waveform as well as SAP, DAP, and MAP
cath needs to be flushed slowly and regularly to prevent clot formation
Need to be careful detachment of equipment does not occur (rapid and severe blood loss)
What are the limitations of DABP monitoring?
technically difficult
specialized equipment required
requires sedation/anesthesia to place arterial cath
constant monitoring
Risk - infection, thromboembolic, serious hemorrhage if cath dislodged
What is the doppler method of measuring BP?
indirect method (NIBP)
relies on detecting blood flow past a pressurized cuff
doppler crystal is placed over artery and used to detect blood flow distal to pressure cuff
How do we use a doppler?
- Clip fur over artery (ventral digital artery or tail artery) MUST be distal to cuff
- Ultrasound gel placed on coupling surface of crystal
- Gel and crystal are placed over artery - crystal taped in place
- Crystal converts pulsatile flow signal to an audible sound delivered via doppler speaker - listen 4 sound of blood moving against blood vessel
- Add sphygmomanometer and cuff - place cuff prox to carpus/tarsus/base of tail
- inflate cuff so pressure in cuff is greater than SAP - flow signal will be lost (no sound)
- As pressure in cuff slowly released, flow signal returns (first audbile sound corresponds with SAP)
can also count pulses, should match manual pulse
What are the limitations of doppler?
Accurate SAP readings >100mmHg
If SAP <100 mmHg, the readings may correlate better with MAP
Very poor estimate for DAP (or readings <80mmHg)
hair and poor surface contact interferes with coupling
can be difficult to place over artery
can be errors if tachycardia or arrhythmia
more labor intensive
What is oscillometric BP?
indirect (NIBP)
hands free device so less labor intensive
accurate for MAP, DAP but may underestimate SAP
How do we use an oscillometric BP device?
- cuff placed on limb or tail over artery + connected to monitor
- Cuff inflates/deflates, oscillation of arterial pulse in cuff detected electronically
- Monitor then calculates and displayed HR, systolic BP, diastolic BP, and calculates MAP
- Always compare HR reading w/ auscultation - if two similar, BP readings more accurate
- Use average of 5 readings - eliminate highest/lowest, use mean of remaining 3 readings.
NOTE: if there is more than 40 mmHG variation, its not correct
What are the limitations of oscillometry
less accurate than doppler if hypotensive
Time (takes several minutes per measurement)
inc margin of error as BP increases
easily affected by arrhythmia and motion (including shiver)
more reliable in dogs than in cats
