Hemodynamics - Putting the puzzle together

Haemodynamics Haemodynamics - putting the puzzle together.- putting the puzzle together.

Associate Professor Brendan E. Smith.Associate Professor Brendan E. Smith.School of Biomedical Science, Charles Sturt University,School of Biomedical Science, Charles Sturt University,

Specialist in Anaesthesia and Intensive Care,Specialist in Anaesthesia and Intensive Care,Bathurst Base Hospital,Bathurst Base Hospital,

Bathurst, NSW, Australia.Bathurst, NSW, Australia.

HRHR SVR SVR HbHb

SVSV DODO22 CVPCVP

COCO SpOSpO22 BPBP

Data Acquisition.Data Acquisition.Haemodynamic data can be acquired in many waysHaemodynamic data can be acquired in many ways

Trans-Thoracic EchocardiographyTrans-Thoracic EchocardiographyTrans-Oesphageal EchocardiographyTrans-Oesphageal Echocardiography

USCOM Doppler examinationUSCOM Doppler examinationImpedence PlethysmographyImpedence PlethysmographyPulmonary Artery CatheterPulmonary Artery Catheter

PiCCOPiCCOEtc etc….Etc etc….

Each has it’s own benefits and drawbacks,Each has it’s own benefits and drawbacks,

BUT….BUT….

However we obtain the raw data we still have a big However we obtain the raw data we still have a big problem…problem…

What do all these figures mean?What do all these figures mean?

How can we put it all together to help our patients?How can we put it all together to help our patients?

Cardiac OutputCardiac Output

Stroke VolumeStroke Volume

Blood PressureBlood Pressure

PreloadPreload Inotropy AfterloadInotropy Afterload

Hb SpOHb SpO22

Oxygen Delivery – DOOxygen Delivery – DO22

Heart RateHeart Rate

SVRSVR

X

X

To live we have to have…To live we have to have…

Blood pressure…Blood pressure…

and blood flow!and blood flow!

Blood pressure Blood pressure doesn’t tell us doesn’t tell us anything about anything about the heart’s ability the heart’s ability to deliver to deliver oxygen!oxygen!

Blood Pressure

Her blood pressure is normal.Her blood pressure is normal.

Anybody Anybody NOTNOT want to know her C.O. and DO want to know her C.O. and DO22?!!?!!(By permission of Dr Joe Brierley, GOSH, London.)

Haemodynamics used to beHaemodynamics used to be a highly invasive science…a highly invasive science…

Insertion of PA Catheter wasInsertion of PA Catheter was

Difficult (especially in children)Difficult (especially in children)

DangerousDangerous

Time consuming Time consuming

ExpensiveExpensive

Of doubtful value!Of doubtful value!

All the data provided by PAC All the data provided by PAC (and more) can be obtained non-invasively…(and more) can be obtained non-invasively…

Cardiac Output

Stroke Volume

Blood Pressure

Preload Inotropy Afterload

Hb SpO2

Oxygen Delivery – DO2

Heart Rate

SVR

The Ultrasonic Cardiac Output MonitorThe Ultrasonic Cardiac Output Monitor - USCOM- USCOM

Suprasternal CW Doppler

Parasternal CW DopplerParasternal CW Doppler

What other data do we get?What other data do we get?

Vpk = Peak Ejection Velocity

CO / CI = Cardiac Output / Index

Why Cardiac Index v Cardiac Output?Why Cardiac Index v Cardiac Output?

The same applies to Stroke Volume, SVR and The same applies to Stroke Volume, SVR and many other parameters in haemodynamicsmany other parameters in haemodynamics

so we useso we use

Stroke Volume Index - Stroke Volume Index - SVISVISVR index – SVR index – SVRISVRIDODO22 Index – Index – DODO22IIVOVO2 2 Index – Index – VOVO22II

Etc…Etc…

MD = Minute Distance = Aortic Velocity

SV = Stroke volume

Ejection Time + SV = Inotropy

SVR = Systemic Vascular Resistance

Cardiac Output

Stroke Volume

Blood Pressure

Preload Inotropy Afterload

Hb SpO2

Oxygen Delivery – DO2

Heart Rate

SVR

Pulse Oximeters

Pulse Oximetry + Hb

Central Venous Oxygen Saturation

Cardiac Output

Stroke Volume

Blood Pressure

Preload Inotropy Afterload

Hb SpO2

Oxygen Delivery – DO2

Heart Rate

SVR

AfterloadAfterload

Depends on:Depends on:

Degree of vasoconstriction / dilationDegree of vasoconstriction / dilationDensity & viscosity of bloodDensity & viscosity of bloodFlow rate of blood / surface tension forcesFlow rate of blood / surface tension forcesElasticity of arteriesElasticity of arteriesStroke volumeStroke volume…………

These are all the same factors These are all the same factors that determine mean aortic root that determine mean aortic root pressure…pressure…

So afterload is exactly the same as mean So afterload is exactly the same as mean aortic root pressure.aortic root pressure.

MAP = diastolic + MAP = diastolic + ⅓ (systolic – diastolic)⅓ (systolic – diastolic)

But can we use radial artery pressure?But can we use radial artery pressure?

Mean Pressure = Mean Pressure = ∫ ∫ P.dtP.dt = Pressure time integral = Pti= Pressure time integral = Pti

tΔΔtt

ΔΔPP

Integrated PressureIntegrated Pressure

time

P2P2

P1P1

P2P2

P1P1

Pti-A Pti-R

Pti-Aortic and Pti-Radial are close enoughPti-Aortic and Pti-Radial are close enough in clinical practice to make no significantin clinical practice to make no significantdifference to haemodynamic calculations.difference to haemodynamic calculations.

(error typically <5%)(error typically <5%)

Cardiac Output

Stroke Volume

Blood Pressure

Preload Inotropy Afterload

(Hb) SpO2

Oxygen Delivery – DO2

Heart Rate

SVR

Inotropy.Inotropy.

Inotropy (myocardial contractility) as a Inotropy (myocardial contractility) as a concept concept is well known to all clinicians but is well known to all clinicians but

not as a not as a discretediscrete quantity quantity..

Depressed inotropy is an important feature Depressed inotropy is an important feature of many ICU presentations –of many ICU presentations –

11oo Cardiac Conditions – Cardiac Conditions –

AMI, LVF, CardiomyopathyAMI, LVF, Cardiomyopathy

22oo Myocardial Depression – Myocardial Depression –

Septicaemia, Pancreatitis, Pneumonia, DKA, Burns, Septicaemia, Pancreatitis, Pneumonia, DKA, Burns, Hypoxia, Crush Injury, Hypovolaemia, Anaemia, Hypoxia, Crush Injury, Hypovolaemia, Anaemia, Thyroid Disorders, Hyper + Hypothermia, Thyroid Disorders, Hyper + Hypothermia, Poisoning, Evenomation, Poisoning, Evenomation,

IatrogenicIatrogenic e.g. Antihypertensives, chemotherapy, e.g. Antihypertensives, chemotherapy,

Electrolyte Disorders, Sedation, Steroids, ……Electrolyte Disorders, Sedation, Steroids, ……

Why is inotropy so important?Why is inotropy so important?

BP = SVR x HR x SV : SV x HR = CO.

Fluid loadingFluid loading

Power of the heartPower of the heart

Blood PressureBlood Pressure

Preload Inotropy Afterload

How do we assess inotropy?How do we assess inotropy?

- - We use surrogates of global cardiac functionWe use surrogates of global cardiac function

- BP, HR, urine output, skin perfusion, capillary - BP, HR, urine output, skin perfusion, capillary refill, skin temperature, bowel sounds, refill, skin temperature, bowel sounds, sweating, wind direction, mother’s seaweed…..sweating, wind direction, mother’s seaweed…..

- All of these are notoriously unreliable indicators - All of these are notoriously unreliable indicators of cardiac function even in the hands of senior of cardiac function even in the hands of senior clinicians.clinicians.

When should we use inotropes?When should we use inotropes?

In >95% of cases this is done by In >95% of cases this is done by

clinical judgment alone!clinical judgment alone!

Which inotrope and how much?Which inotrope and how much?

What are our therapeutic targets?What are our therapeutic targets?

How do we know we’ve reached them?How do we know we’ve reached them?

If only we could If only we could measuremeasure inotropy!! inotropy!!

How Can We Measure Inotropy?How Can We Measure Inotropy?

Conservation of EnergyConservation of Energy

The energy produced by cardiac contraction The energy produced by cardiac contraction must be converted to either Potential Energy must be converted to either Potential Energy (PE) in the form of blood (PE) in the form of blood pressurepressure or Kinetic or Kinetic

Energy (KE) in the form of blood Energy (KE) in the form of blood flowflow..

But can we measure PE & KE?But can we measure PE & KE?Is the measurement reliable?Is the measurement reliable?

How long does it take?How long does it take?Can we monitor Rx with it?Can we monitor Rx with it?

Potential EnergyPotential EnergyPE developed by the heart appears in the form of the energy PE developed by the heart appears in the form of the energy

needed to raise the stroke volume up to arterial pressure needed to raise the stroke volume up to arterial pressure in a given systolic time, the Flow Time.in a given systolic time, the Flow Time.

Work Done = Work Done = ΔΔP x P x ΔΔVV

PE = MAP x SVPE = MAP x SVFlow TimeFlow Time

ΔΔP = Mean Arterial Pressure - CVPP = Mean Arterial Pressure - CVPSV and Flow Time are measured directly using SV and Flow Time are measured directly using

CW Doppler. CW Doppler.

PE = BPm x SV x 10PE = BPm x SV x 10-3-3

7.5 x FT7.5 x FT

Potential EnergyPotential Energy

7.5 and 107.5 and 10-3-3 are required to convert BP in mmHgare required to convert BP in mmHg

to kPa and SV in ml to mto kPa and SV in ml to m33 to conform with SI units. to conform with SI units.The unit for PE is therefore Joules/second, or The unit for PE is therefore Joules/second, or WattsWatts. .

Kinetic EnergyKinetic EnergyThe KE of any moving mass is given by –The KE of any moving mass is given by –

KE = KE = ½½mVmV22

The mass of blood ejected per Stroke Volume is - The mass of blood ejected per Stroke Volume is - SV(ml) x 10SV(ml) x 10-6-6 x Density of blood, x Density of blood, ρρ (1,055 kg/m (1,055 kg/m33))

The KE developed by the heart in a given flow time is –The KE developed by the heart in a given flow time is –

KE = KE = 11 x SV x 10 x SV x 10-6-6 x x ρρ x V x V22

2 x Flow Time2 x Flow Time

(V is measured directly by CW Doppler)(V is measured directly by CW Doppler)

Total Inotropy = PE + KE Total Inotropy = PE + KE

( = blood pressure + blood flow)( = blood pressure + blood flow)

Inotropy = BPm x SV x 10Inotropy = BPm x SV x 10-3 -3 ++ 1 x SV x 101 x SV x 10-6-6 x x ρρ x V x V22

7.5 x FT7.5 x FT 2 x FT2 x FT

(The Smith-Madigan Formula)(The Smith-Madigan Formula)

The SI unit of inotropy is therefore the The SI unit of inotropy is therefore the WattWatt..

Inotropy IndexInotropy Index

But how do we judge inotropy in patients of varying size, e.g. large and small adults, children, infants?

By analogy to cardiac index which is –

Cardiac Index = Cardiac Output

Body Surface Area

Smith-Madigan Inotropy Index = Inotropy

BSA

The SI unit of SMII is thereforeThe SI unit of SMII is therefore W/mW/m22

Smith-Madigan Inotropy IndexSmith-Madigan Inotropy Index

Normal ControlsNormal Controls

1.6 – 2.2 W/m1.6 – 2.2 W/m22

Left Ventricular FailureLeft Ventricular Failure

0.4 – 1.1 W/m0.4 – 1.1 W/m22

Septicaemic ShockSepticaemic Shock

0.6 – 1.2 W/m0.6 – 1.2 W/m22

Cardiogenic ShockCardiogenic Shock

74 year old man with STEMI74 year old man with STEMI

BP 84/44, pulse 114, SpOBP 84/44, pulse 114, SpO22 84% on 10L/min O 84% on 10L/min O22

Pulmonary Oedema +++Pulmonary Oedema +++

No urine outputNo urine output

PaOPaO22 64mmHg, PaCO 64mmHg, PaCO22 28mmHg 28mmHg

Lactate 8.4Lactate 8.4

8 12 14

>2.4

60-75

<90

800-1200

0.62 0.97 1.13 1.38 SMII W/m2

Dobutamine mcg/kg/min

Cardiac Output

Stroke Volume

Blood Pressure

Preload Inotropy Afterload

(Hb) SpO2

Oxygen Delivery – DO2

Heart Rate

SVR

PreloadPreloadJVP / CVP

- Only looking at the right side of the heart.- Only looking at the right side of the heart.

- Tells us little about left heart preload.- Tells us little about left heart preload.

- Tricuspid valve integrity? Stenosis and - Tricuspid valve integrity? Stenosis and regurgitation both lead to errors.regurgitation both lead to errors.

- Arrythmias lead to error. - Arrythmias lead to error.

- Even right ventricular - Even right ventricular pressurepressure tells us little tells us little about right ventricular about right ventricular volumevolume..

Pulmonary artery catheter

What pressure should we use?What pressure should we use?

PA Diastolic Pressure (PADP)? PA Diastolic Pressure (PADP)? PA Wedge Pressure (PAWP)? PA Wedge Pressure (PAWP)? PA mean Pressure (PAPm)?PA mean Pressure (PAPm)?

Is the catheter in the right place?Is the catheter in the right place?What about IPPV, PEEP, pulmonary What about IPPV, PEEP, pulmonary vascular patency, vasoconstriction, shunts, vascular patency, vasoconstriction, shunts, arrythmias, mitral valve problems….etc.arrythmias, mitral valve problems….etc.

PACPAC

Attempts to measure left ventricular end Attempts to measure left ventricular end diastolic diastolic pressure pressure - - LVEDPLVEDP

Left ventricular preload is strictly the left Left ventricular preload is strictly the left ventricular end diastolic ventricular end diastolic volumevolume – – LVEDVLVEDV

Ventricular end diastolic pressure only acts Ventricular end diastolic pressure only acts as an acceptable surrogate if we know the as an acceptable surrogate if we know the ventricular ventricular compliancecompliance..

Can basic physiology help us?

Inotropy

SV

LVEDV

Passive Leg Raising - Passive Leg Raising - ↑↑SVSV

Stroke volume increases from Stroke volume increases from 26ml to 32ml = 26ml to 32ml = 23%23%

Patient still on left side of Starling Curve.Patient still on left side of Starling Curve.

Patient will respond to volume loading.Patient will respond to volume loading.

Passive Leg Raising test can be repeatedPassive Leg Raising test can be repeatedafter fluid bolus.after fluid bolus.

Cardiac Output

Stroke Volume

Blood Pressure

Preload Inotropy Afterload

(Hb) SpO2

Oxygen Delivery – DO2

Heart Rate

SVR

OK, this is all very clever stuff but OK, this is all very clever stuff but does it make any difference todoes it make any difference to

patient outcomes?patient outcomes?

Haemodynamic strategy – June 2005Haemodynamic strategy – June 2005

MortalityMortality

20

16

12

8

4

ConclusionsConclusions

• The haemodynamic jigsaw can be solved.The haemodynamic jigsaw can be solved.

• It can be done non-invasively.It can be done non-invasively.

• It can be painless, simple and cheap.It can be painless, simple and cheap.

• It can be done anywhere, anytime.It can be done anywhere, anytime.

• Can, with practice, be very quick!...Can, with practice, be very quick!...

Thank you!Thank you!