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what is blood pressure

the force that the flow of blood puts on the wall of the vessels


what is blood pressure measured in?



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



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