Haemodynamics Haemodynamics - putting the puzzle - putting the puzzle together. together. Associate Professor Brendan E. Smith. Associate Professor Brendan E. Smith. School of Biomedical Science, Charles Sturt School of Biomedical Science, Charles Sturt University, 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. HR HR SVR SVR Hb Hb SV SV DO DO 2 CVP CVP CO CO SpO SpO 2 BP BP
Haemodynamic data can be acquired in many ways. However we obtain the raw data we still have a big problem… What do all these figures mean? How can we put it all together to help our patients?
Associate Professor Brendan E. Smith. School of Biomedical Science, Charles Sturt University, Specialist in Anaesthesia and Intensive Care, Bathurst Base Hospital, Bathurst, NSW, Australia
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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,
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…
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.
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 –
- 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)
- 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!...