blood pressure monitoring Flashcards
what is blood pressure
the force that the flow of blood puts on the wall of the vessels
what is blood pressure measured in?
mmHg
when was blood pressure first performed
1733 - horse jugular
what are the 3 numbers of arterial BP
top - SAP - Systolic Arterial Pressure
bottom - DAP - Diastolic A. P
overall number - MAP - Mean A. P.
what is systolic arterial pressure
pressure against the arteries - generated when the left ventricle is fully contracted
what is diastolic arterial pressure
minimum pressure maintained between contractions - pressure measured when the left ventricle relaxes or at rest
what is mean arterial pressure
equates to overall pressure throughout the cardiac cycle
what is the formula to calculate MAP
= (SAP-DAP)/3 + DAP
when considering perfusion pressure on an organ was is more important of the 3 measurements
MAP
what is the formula for BP
Cardiac Output (CO) x Systemic Vascular Resistance (how much resistance/elasticity the blood vessels are)(SVR)
what is the formula for cardiac output
Heart rate x Stroke Volume (volume in the circulation)
what are the 2 mechanisms that control the response to changes in BP
short-duration and long-duration systems
what is the short- duration system for blood pressure regulation
Mediated through changes in HR and SVR (regulated blood pressure minute by minute)
what is the long duration system for blood pressure regulation
Acts primary via changes in blood volume and ↑ SV
where are the main areas to find baroreceptors
o Left Atrium
o Aortic arch
o Carotid sinus
what happens in the rapid-responding short duration system
- increase parasympathetic stimulation of the heart
o Decrease HR - decrease sympathetic stimulation of the heart
o Decrease HR and SV - decrease sympathetic stimulation of the vasomotor center
o vasodilation of the blood vessels
what is the renin-angiotensin-aldosterone system
hormone system that regulates BP and fluid balance
Triggered by baroreceptors and by direct effects of hypotension on the kidneys
what can activate the RAAS (renin-angiotensin-aldosterone system)
o Profound vasoconstriction
o Water and sodium retention
o ↑ thirst
o Net result = expansion of blood volume to maintain BP
what patients might we do for BP measurement
All hospitalized patients – baseline data Geriatric patients Patients receiving cardiac meds ICU patients Peri and post-op monitoring Trauma Renal failure Hypertension/hypotension
what is direct BP measurement
Arterial catheterization (dorsopedal or femoral artery)
Connected to a pressure transducer →convert mechanical fluctuations in the fluid into an electrical signal
Continuous measurement of BP
what is indirect BP measurement
Less expensive, less time consuming and less technically demanding
Detect blood flow under or past a pressurized cuff
2 most popular systems:
o Doppler Sphygmomanometric method
o Oscillometric System
what is the doppler system
“Korotkoff” sounds are inaudible in veterinary patients
Piezoelectric crystal on a peripheral artery to determine flow throughout that artery
A BP cuff is placed proximal to the probe and connected to a syphgmomanometer
Inflate cuff until artery is fully occluded → loss of sound
Reduce cuff pressure slowly until the sound returns → SAP in dogs and ~ MAP in cats
why might you not hear anything for the doppler system
Weakly/absent audible signals: o Insufficient coupling gel o Hair interference o Crystal placement o Hypothermia o Vasoconstriction Inability to determine DAP and MAP(dogs)
what is the Oscillometric System
Detects oscillation produced by changes in artery wall diameter during blood flow
Inflating the cuff collapses the artery
As the cuff is deflated, Amplitude of oscillation:
o Increases at SAP
o Reaches a maximum at MAP
o Decreases at DAP
where is the site for cuff placements
o Forelimbs and Hindlimbs, proximal to carpus/tarsus
o Tail
what happens if the cuff is too big
o False low BP
o Wide cuff spreads pressure over a larger area, delaying return of the distal pulse
what happens if the cuff is too small
o Falsely high BP
o Insufficient pressure and allow early return of the pulse
what is the correct cuff width for dogs and cats
o 40% of limb circumference for dogs
o 30% of limb circumference for cats
what is the BP range for dogs (SAP?DAP?MAP?)
o SAP: 90-140
o DAP: 50-80
o MAP: 60-100
what is the BP range for cats (SAP?DAP?MAP?)
o SAP: 80-140
o DAP: 55-75
o MAP: 60-100
what is the in general BP range
o SAP of 120
o DAP of 80
o MAP of 90
what is the central venous pressure
Hydrostatic pressure in the intrathoraxic vena cava – approx = right ventricular pressure
Changes in blood volume → pressure changes in vena cava
Estimate right ventricular end-diastolic volume capacity
Estimate the cardiac function
what are the indications of central venous pressure
◦ Monitoring fluid therapy for hypovolemic patients
◦ At risk of volume overload
if you have a low CVP what does it mean
less than 0 cmH2O
◦ Hypovolemia (↓ SV), vasodilation
when do you not want to place a central line in an animal
Coagulopathies
Thromboembolic disease - Hyperadrenocorticism (cushing disease – prone to developing micro clots), Immune-mediated disease
Intracranial disease - Head trauma, Seizures
if you have a high CVP what does it mean
(Greater than 10cmH2O)
◦ Volume over load
◦ Right-sided heart failure
◦ Significant pleural effusion,
◦ Pericardial effusion (acculmation of fluid in the pericardial sac)
◦ Cardiac tamponade (a result of pericardial effusion)
what is the normal range for central venous pressure
◦ 0-10cmH2O TRENDS
