Lecture 8 HEmodynamics Part 1 Student

8/4/2019 Lecture 8 HEmodynamics Part 1 Student

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Hemodynamics Part 1

Pressures


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Hemodynamics

Study of the movement of blood and itsrelationship with:

Cardiac function Pulmonary and systemic blood pressures Resistance throughout the entire

Cardiovascular system


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Lungs

Brain

Liver

Stomach

Pancreas

Intestines

Kidneys

Skin

Muscle

Arterioles

Pre-capillarySphincters

Veins(Flexible Compliant Pipes)

Arteries(Stiff Inflexible Pipes)

Circulation:

Blood flow fromhigh to low pressure(remind you of anything?)


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RA

RV

LUNGS LA

LV

AORTA

ARTERIOLES

SYSTEMICARTERIES

VEINS

(90)

(40)

low compliance

13% of blood volume

high compliance64% of blood volume

(2)

CAPILLARYBEDS

7% of blood volume

9% of blood volume

(7)

(13) (3)

Flow (Q) = upstream pressure downstream pressure

resistance

The CardiovascularHemodynamic System

Mean pressures in red

(20)

(8)

204


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Pressures we can measure

Arterial Blood Pressure

Central Venous Pressure

Pulmonary Artery Pressure

Left Atrial Pressure


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Arterial Blood Pressure

Pressure = Flow x Resistance Flow = how fast stroke volume exits heart Resistance =diameter of vessels (SVR)

Measurements can be Non-invasive

Invasive with indwelling catheter

Normal Values:


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Waveform from A-line

Ejection

If unable to see dicrotic notch may be dampened, pressure may be falsely low


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Arterial Pressure cont

Pulse Pressure Difference between Systolic and Diastolic

pressure NORMAL = 30-40

Depends on SV and arterial compliance Low SV = decreased pulse pressure

Mean Airway Pressure Average pressure NORMAL = 80-100mmHg

MAP = Systolic + (2 * Diastolic)

3


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Central Venous Pressure (CVP)

A Catheter is placed with the tip lying in theSuperior vena cava or Right Atrium

Measures mean Right Atrial Pressure (RAP)

Indications:

To assess circulatingblood volume and guide

fluid replacement

Other Benefits: blood draw &


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Factors affecting CVP

Blood Volume status Volume must be enough to fill vascular space If right heart pump is OK, CVP reflects

vascular volume

Heart capabilities how well can it pump?

Venous tone (which changes vascularResistance and space)


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RVLV

LUN

GS

Tissue

RA LA


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RVLV

LUN

GS

Tissue

RA LA


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CVP will Increase with: Fluid overload Right heart failure- Severe left heart failure- Large Pulmonary Emboli- Pulmonary hypertension PEEP - how much?

CVP will Decrease with:

Hypovolemia (dehydration, Blood loss) Vasodilation (Shock)

RV LV

LUNGS

Tissue

R

A

LA


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CVP waveform

Atrial

contr

action

Clo

sure

ofA

V

Valve V

entric

ular

systole


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CVP

Complications: Pneumothorax, bleeding, infection, thrombus,

air embolus


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PA Catheter

Balloon tipped catheter placed with the tiplying in the Pulmonary Artery

Can obtain both right and left heart pressures Used for CO determination Can obtain Mixed Venous samples Some have SvO2 and pacing capabilities


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Balloon Port

Proximal Port

Distal Port

Thermister


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Distal Port

Measures:

Proximal Port

Measures:


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Pressures obtainable: CVP (RAP) PA (Systolic, diastolic and mean) PCWP (PAOP) This reflects Left heart fuiinction


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PA Catheter Placementand Waveforms

(CVP)

CVP

2-6

RV

20-30

PAP20-306-15

PCWP4-12


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This is the Pulmonary BP Systole pressure depends on:

Stroke volume, rate of blood flow (force of contraction), andresistance of pulmonary vasculature

The mean PAP is the average pressure in the pulmonary system Its used to help determine Pulmonary Vascular Resistance (PVR)

and is used to assess how much work the R ventricle must pushagainst (Afterload)

Normal value is: 20-306-15

Mean : 10-20mmHg


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Indications Hemodynamically unstable patients Cardiogenic shock, sepsis Unstable thoracic surgery patients

Complications Same as CVP but with the additional:

Dys-rhythmia (mostly during placement) Pulmonary infarct if it wedged in PA

Pulmonary Artery PressureMeasurement


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PA Pressures will Increase with: Increased Pulmonary resistance

PE, pulm hypertension, COPD (cor pulmonale)

Increased contractility of heart PEEP how much?

PA pressures will Decrease with: Decreased resistance Decreased Stroke volume


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Pulmonary Capillary Wedge Pressure(PCWP, PAOP, Wedge)

Represents mean Left Atrial Pressure (LAP) Indicates Left ventricular function

With the balloon inflated, the wedged PACcreates a channel with no blood flow from thecatheter tip to the left atrium, thus allowingindirect measurement of the leftatrial pressure.

Normal:

2-12 mmHg


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Preload -Ventricular end diastolic volume / Pressure - the amount of stretch ofventricle

RV preload indicator is =____________(pressure)

LV preload indicator is = ____________ (pressure)

Afterload - resistance to ventricular emptying during systole or

the amount of pressure the left ventricle must generate to squeeze blood into theaorta.RV afterload = ____________ (Pressure)LV afterload = _____________(Pressure)

Definitions


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Starlings Law of the Heart and Contractility

SV

(left ventricularperformance)

Preload

(venous return or EDV)

ucontractility

normalcontractility

d contractility(heart failure)

Preload X

SV at Preload X - u contractility

SV at Preload X - N contractility

SV at Preload X - d contractility

Starlings Law:The greater the EDV (preload), the more blood comes out of the heart until

State of Myocardial Contractility:Determines the amount of blood(SV) that comes out of the heart at agiven preload


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SVR and PVR

Resistance - the sum of all forces that opposeblood flowdue to:

Length of vasculature (L) Blood viscosity (V) Vessel radius (r)

Systemic Vascular Resistance (SVR):

(MAP RAP) * 80 / CO

Pulmonary Vascular Resistance (PVR)(Mean PAP LAP) * 80 / CO

The largest variable is Vessel RADIUS


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Similarities

How do you calculate Resistance on aventilator?

Change in airway pressure / flow

Same thing here: change in vascular pressure / CO (flow)

The Cardiovascular


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RA

RV

LUNGS LA

LV

AORTA

ARTERIOLES

SYSTEMICARTERIES

VEINS

(90)

low compliance

13% of blood volume

high compliance64% of blood volume

(2)

CAPILLARYBEDS

7% of blood volume

9% of blood volume

(13) (3)

Flow (Q) = upstream pressure downstream pressure

resistance

The CardiovascularHemodynamic System

Mean pressures in red


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SVR

(95-5)mmHg*80 /5L

=1440 dyne-sec/cm5

Normal = 800-1200

(15-5)mmHg*80 / 5

=160 dyne-sec/cm5

Normal =


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End Diastolic Volume (EDV)

Volume at the end of diastole(end of ventricular filling). In ahealthy heart this is directlyproportional to venous return

Stroke Volume (SV) = CO / HR

Ejection Fraction (EF) = SVEDV

Ventricular Volumes - Definitions

SystoleED

V


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Homework state whether the pressures in eachwill go up, down or stay the same.

CVP PAP PCWP

Normal =

Right ventricular failure

Left ventricular failure

Pulmonary hypertension

Non-cardiogenic pulmonaryedema (ARDS)

Mitral valve stenosis orinsufficiency

Pulmonary Embolism

Lecture 8 HEmodynamics Part 1 Student

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