N470: Perfusion (exam 2)

the process of nutrient delivery of arterial blood to a capillary bed

perfusion

what is the purpose of perfusion?

supply and organ or tissue with O2 and nutrients

noninvasive assessment of perfusion (7)

1) LOC

2) skin

3) urine output

4) color

5) BP

6)HR

7) capillary refill

perfusion scanning methods

- CT perfusion

- MRI perfusion- contrast injected and a series of fast images are taken

- nuclear medicine perfusion- uses radioactive isotopes

what are the two main factors of cardiac output?

HR and stroke volume

what are the three main determinants in stroke volume?

preload, afterload, contractility

what are the two main elements in preload?

CVP and PAWP

what are the two main elements in afterload?

SVR, PVR

what are the two main elements in contractility?

EF%, SV

the amount of volume/ blood ejected/ pumped from the heart in one minute

cardiac output

cardiac output formula

CO = HR x SV

Normal CO

4-8 L/min

The best indicator of cardiac function (vs CO) that corrects for body size?

CI

CI formula

CO/BSA (body surface area)

Normal CI

2.4-4 L/min

volume of blood pumped with each heartbeat

stroke volume (SV)

normal stroke volume

60-70 mL/beat

A severe increase in HR will cause the ______ ______ to decrease due to decreased _______ time, causing a _______ in CO

A severe increase in HR will cause the stroke volume to decrease due to decreased filling time, causing a decrease in CO

Influence of HR on CO*

- tachycardia

- afib

- bradycardia

- vtach

What are the four determinants of CO?

HR, preload, afterload, contractility

How does HR determine CO?

immediate increase in CO if SV constant

How does contractility determine CO?

it is the force of myocardial contraction and the pump function

amount of blood in the ventricle at the end of diastole (stretch); end diastolic ventricular volume*

preload

the resistance the ventricle must overcome to eject blood; ventricular pressure at the end of systole*

afterload

Factors affecting preload

- volume: venous return, total blood volume, atrial kick

- compliance: stiffness and thickness of ventricular wall

Symptoms of decreased preload (7)

1) tachycardia

2) decreased U/O

3) increased specific gravity

4) dry mucous membranes

5) tented skin

6) sunken eyes

7) orthostatic hypotension

Symptoms of increased preload (7)

1) JVD

2) pedal edema

3) S3, S4

4) crackles

5) dyspnea

6) pink, frothy sputum

7) ascites, hepatic engorgement

what is a reliable indicator of volume/pressure in the right side of the heart?

JVD

an increase in JVD tells us about the patient's ___

CVP (central venous pressure)

Steps to measure JVD

- HOB 45 degrees

- head turned right

- identify sternal angle

- locate superior sternal notch

- measure distance between top pulsation and sternum in cm

- 4cm or less is normal

Medications affecting preload

fluids, diuretics, venodilators (nitrates, morphine, ace inhibitors)

increasing venous return, and therefore the filling pressure of the ventricle will lead to increased force of contraction and stroke volume

frank starling law of the heart

afterload is affected by...? (4)

1) aortic impedance

2) blood viscosity

3) blood volume

4) vascular tone

resistance to ejection from the left side of the heart

SVR (systemic vascular resistance)

SVR formula

MAP-CVP/CO x 80

Normal SVR

800-1200

resistance to ejection from the right side of the heart

PVR (pulmonary vascular resistance)

normal PVR

50-250

Symptoms of increased afterload (6)

1) pale, cool, clammy skin

2) HTN

3) non-healing wounds

4) thick, brittle nails

5) slow cap refill

6) decreased U/O

Symptoms of decreased afterload (3)

1) warm, flushed skin

2) increased CO

3) decreased BP

the ability of a muscle to shorten when stimulated; the force of myocardial contraction; measured as EF

contractility

Normal EF% range

60-70%

Symptoms of decreased contractility (5)

1) hypotension

2) fatigue

3) SOB

4) dizziness

5) low U/O

Symptoms of increased contractility (1)

increased BP

indications for hemodynamic monitoring

1) alterations in CO

2) alterations in fluid volume

3) alterations in tissue perfusion

What is the purpose of a CVP central line?*

reflects filling pressures in the right ventricle (preload of right heart); guides overall fluid balance

Noninvasive hemodynamic technologies (2)

1) impedance cardiography

2) doppler ultrasound

what noninvasive hemodynamic technology assesses cardiac function by measuring resistance to the blow of high frequency, low-amplitude current and measures SV, CO, SVR, and contractility?

impedance cardiography

what noninvasive hemodynamic technology measures blood flow velocity in the vessel and helps to determine CO, preload, afterload, and contractility

doppler ultrasound

Minimally invasive hemodynamic technologies (3)

1) CVPs- transducer/computer based and visual

2) arterial access line

3) MAP

MAP formula

(SBP + 2(DBP))/3

Locations for arterial line placement (5)

1) radial

2) DP

3) femoral

4) axillary

5) brachial

indications for an art line (3)

1) monitoring BP

2) frequent ABGs

3) if low CO or shock cuff is unreliable

Difference between an art line and a BP cuff

- art line- measures flow inside artery

- cuff- measures flow from outside artery

- may measure 5-10 mmHg differently

Vigileo FloTrac Benefits

- Minimally invasive; Connects to existing arterial line.

- Requires no manual calibration.

- Automatically calculates hemodynamic values every 20 seconds.

- Accurate when validated against Swan catheter

Which data does Vigileo produce?

- CO

- CI

- central venous oxygen saturation

- SV

- SV variation

- SVR

central venous oxygen saturation

determines oxygen extraction vs demand (O2 utilization)

Which hemodynamic parameter assesses ventricular performance?

SV

What is stroke volume variation?

variation in SV given as %; >15% may indicate hypovolemia

Which hemodynamic parameter is an indicator of afterload?

SVR

SWAN/PA catheter measurements

- PAP (pulmonary artery pressure) - systolic, diastolic, mean

- PAWP (pulmonary artery wedge pressure)

- CVP (central venous pressure)

- CO

- CI

- SVR

- PVR

PA catheter advantages

- real-time data

- simultaneously measures a variety of hemodynamic parameters

- able to rapidly assess pt response to interventions

PA catheter disadvantages

- infection

- insertion complications (pneumothorax, bleeding, damage to blood vessels, or heart dysrhythmias)

- air emboli, exsanguination

- balloon rupture (rare)

- pulmonary artery rupture (rare)

What does PAWP reflect?

left sided preload

normal PAWP

4-12 mm Hg

What does CVP reflect?

right sided preload

normal CVP

2-6 mmHg

What does PAP measure?

blood pressure in the lungs

normal PAP

20-30/ 10s mmHg

What does CO/CI measure?

volume ejected/min with each beat

Normal CO and CI

CO = 4-8L/min

CI = 2.5-4 L/min

What does PVR reflect?

right sided afterload

What does SVR reflect?

left sided afterload

Normal PVR

50-250 dynes/sec/cm-5

Normal SVR

800-1200 50-250 dynes/sec/cm-5

conditions that elevate PA pressures (2)

1) pulmonic valve stenosis/calcification

2) pulmonary HTN

a condition elevating PA pressures; insidious process that happens over time with increased afterload on right ventricle

pulmonic valve stenosis/calcification

a condition elevating PA pressures; increased afterload on right ventricle which impacts right ventricular emptying (incomplete emptying)

pulmonary hypertension

Interventions for elevated PA pressures

- find cause

- reduce preload (circulating volume)

- decrease venous return to the right side

- increase/improve contractility

- meds

- Na and fluid restriction

- valve replacement/repair

meds for increased PA pressures

1) vasodilators (viagra)

2) diuretics

The degree of stretch in myocardial fibers at the end of diastole *

preload/ventricular filling

According to the Frank Sterling law, the more you stretch the ventricle during , the stronger the contraction in *

According to the Frank Sterling law, the more you stretch the ventricle during diastole, the stronger the contraction in systole

The most common cause of pulmonary HTN*

aortic valve disease/stenosis