Cardiac Output MonitoringCardiac Output Monitoring

Dr Peter SherrenDr Peter Sherren

BackgroundBackground• While goal-directed therapy in severe Sepsis/septic shock has shown to While goal-directed therapy in severe Sepsis/septic shock has shown to

improve outcome, CO and DO2 is only part of the goal directed improve outcome, CO and DO2 is only part of the goal directed therapy, there are many others. Rivers et al NEJM 2001; 345.therapy, there are many others. Rivers et al NEJM 2001; 345.

• PACs are regarded amongst many as the GOLD standard for PACs are regarded amongst many as the GOLD standard for measuring CO/LVEDP and even whilst using our GOLD standard we measuring CO/LVEDP and even whilst using our GOLD standard we have no conclusive data for improvement in patient outcome. Shah et have no conclusive data for improvement in patient outcome. Shah et al, JAMA 2005 (5051 patients) and PAC-man study, Harvey et al, Lancet al, JAMA 2005 (5051 patients) and PAC-man study, Harvey et al, Lancet 2005. Given this, one does question the benefit of any CO monitoring, 2005. Given this, one does question the benefit of any CO monitoring, no matter how close the correlation to our GOLD standard.no matter how close the correlation to our GOLD standard.

• Infact Edwards Lifesciences at the beginning of all their Infact Edwards Lifesciences at the beginning of all their sales/presentation always have a disclaimer ‘sales/presentation always have a disclaimer ‘There is NO data to There is NO data to suggest that care is improved or outcomes differ with the utilization of suggest that care is improved or outcomes differ with the utilization of monitors that assess cardiac function’.monitors that assess cardiac function’.

• Is it worth continuing then?Is it worth continuing then?

Techniques for monitoring COTechniques for monitoring CO

• InvasiveInvasive• PA catheter (Dye, thermodilution intermittent/continuous) PA catheter (Dye, thermodilution intermittent/continuous) • Fick PrincipleFick Principle

• Low-invasiveLow-invasive• TOETOE• Oesophageal dopplerOesophageal doppler• Arterial pulse contour analysis (PiCCO, LiDCO, Computer Arterial pulse contour analysis (PiCCO, LiDCO, Computer

algorithm)algorithm)

• True Non-InvasiveTrue Non-Invasive• TTETTE• Transthoracic bio-impedenceTransthoracic bio-impedence• Clinical Examination!!Clinical Examination!!

Pulmonary Artery CatheterPulmonary Artery CatheterQuick summaryQuick summary

PAC is designed to measure:PAC is designed to measure:• Intra-cardiac pressuresIntra-cardiac pressures

RAP/RVP/PAP/PAOPRAP/RVP/PAP/PAOP

• CO/SV and indirectly many CO/SV and indirectly many SVR/LVSW etcSVR/LVSW etc

• True SvO2True SvO2

Contra-indications:Contra-indications:• Tricuspid or pulmonary valve Tricuspid or pulmonary valve

mechanical prosthesis mechanical prosthesis

• Right heart mass (thrombus Right heart mass (thrombus and/or tumor) and/or tumor)

• Tricuspid or pulmonary valve Tricuspid or pulmonary valve endocarditisendocarditis

• Many relative Many relative contraindications reducing contraindications reducing accuracyaccuracy

PAC cont.PAC cont.

PA Catheter ComplicationsPA Catheter Complications

• InfectionInfection

• Air emboliAir emboli

• ThrombosisThrombosis

• PA infarctionPA infarction

• PA rupturePA rupture

• Balloon ruptureBalloon rupture

• ThrombocytopeniaThrombocytopenia

• Catheter knottingCatheter knotting

• Ventricular Ventricular DysrhythmiasDysrhythmias

• HemothoraxHemothorax

• PneumothoraxPneumothorax

• Cardiac TamponadeCardiac Tamponade

Fick PrincipleFick Principle

• Fick Principle: measure volume Fick Principle: measure volume displacementdisplacement

• First proposed in 1870First proposed in 1870

• ““The total uptake or release of a substance by The total uptake or release of a substance by an organ is the product of the blood flow an organ is the product of the blood flow through that organ and the arteriovenous through that organ and the arteriovenous concentration difference of the substance.”concentration difference of the substance.”

• CO = CO = OO22 consumption (ml/min) consumption (ml/min) art – mixed venous Oart – mixed venous O22 conc. (ml/l) conc. (ml/l)

• Limited by cumbersome equipment, sampling Limited by cumbersome equipment, sampling errors, need for invasive monitoring and steady-errors, need for invasive monitoring and steady-state haemodynamic and metabolic conditionsstate haemodynamic and metabolic conditions

Low Invasive MonitoringLow Invasive Monitoring

TOETOE

• CO can be obtained via either:CO can be obtained via either:• SV= CSA x VTI, VTI= Vmean x t SV= CSA x VTI, VTI= Vmean x t (using PW doppler flow through either AV/PV/LVOT)(using PW doppler flow through either AV/PV/LVOT)• SV= EDV – ESVSV= EDV – ESV

• CO measurements using CW doppler have been validated CO measurements using CW doppler have been validated as a clinical alternative to thermodilution.as a clinical alternative to thermodilution.

• Useful tool for regional as well as overall cardiac function. Useful tool for regional as well as overall cardiac function. RV and LV discrepancies. Visual tool as well as quantative. RV and LV discrepancies. Visual tool as well as quantative.

• Recent data to suggest management benefit in general ICU Recent data to suggest management benefit in general ICU setting, L.E. Orme et al, Br. J. Anaesth., March 2009; 102: setting, L.E. Orme et al, Br. J. Anaesth., March 2009; 102: 340 – 344340 – 344..

• Operator dependent; time consuming; no beat to beat Operator dependent; time consuming; no beat to beat reactivity; accuracy in tachycardias; training required; cost reactivity; accuracy in tachycardias; training required; cost of equipment.of equipment.

Oesophageal DopplerOesophageal Doppler

• Ultrasonic doppler –Continuous or pulse wave dopplerUltrasonic doppler –Continuous or pulse wave doppler

• Placed parallel to direction of blood flow Placed parallel to direction of blood flow

• Velocity of blood measured by change in frequency of of Velocity of blood measured by change in frequency of of the reflected ultrasound wavethe reflected ultrasound wave

• 4 MHz continuous or 5 MHz pulsed wave4 MHz continuous or 5 MHz pulsed wave

• Transoesphageal dopplerTransoesphageal doppler• Measures descending thoracic blood flowMeasures descending thoracic blood flow• User dependent, requires anaesthetised pt currentlyUser dependent, requires anaesthetised pt currently• Makes certain anatomical and mathematical assumptionsMakes certain anatomical and mathematical assumptions

• Suprasternal doppler Suprasternal doppler • non-invasively measures asc. Aorta flownon-invasively measures asc. Aorta flow• Limited by probe position, aortic valve abnormalites & Limited by probe position, aortic valve abnormalites &

median sternotomymedian sternotomy

Oesophageal Doppler principlesOesophageal Doppler principles

• Principle of stroke Principle of stroke volume calculation from volume calculation from aortic velocity (VAo) aortic velocity (VAo) measurements. measurements.

• The area under the The area under the maximum aortic velocity maximum aortic velocity envelope (VTI) envelope (VTI) represents the stroke represents the stroke distance distance

Cardio QCardio Q

Cardio Q cont.Cardio Q cont.

Oesophageal Doppler Oesophageal Doppler

• DisadvantagesDisadvantages• Interference by NG tube / diathermyInterference by NG tube / diathermy• Dislodged by movementDislodged by movement• Contraindicated in oesophageal surgeryContraindicated in oesophageal surgery

• AdvantagesAdvantages• Min invasiveMin invasive• Real time measurementReal time measurement• Rapid insertionRapid insertion• Minimal skill levelMinimal skill level• Good trend monitorGood trend monitor

Pulse contour analysisPulse contour analysis

• 3 main types:3 main types:• Transpulmonary thermodilution + pulse Transpulmonary thermodilution + pulse

contour analysis (PiCCO)contour analysis (PiCCO)

• Lithium dilution (LiDCO)Lithium dilution (LiDCO)

• Pure Pulse contour analysis using computer Pure Pulse contour analysis using computer algorithm (Flowtrac/Vigileo)algorithm (Flowtrac/Vigileo)

PiCCOPiCCO

• Pulse contour analysis with intermittent Pulse contour analysis with intermittent thermodilution measurement.thermodilution measurement.

• Enables continuous hemodynamic monitoring using: Enables continuous hemodynamic monitoring using: – femoral or brachial artery catheter femoral or brachial artery catheter – central venous catheter central venous catheter

• Adult or pediatric patients who have or may develop Adult or pediatric patients who have or may develop pulmonary edema or ARDS are likely candidates pulmonary edema or ARDS are likely candidates

PiCCOPiCCO

• Thermodilution Parameters• Cardiac Output - CO• Global Enddiastolic Volume - GEDV• Intrathoracic Blood Volume - ITBV• Extravascular Lung Water - EVLW

• Pulse Contour Parameters• Continuous Cardiac Output - CCO• Systemic Vascular Resistance - SVR• Stroke Volume Variation - SVV

t

-∆T

t

-∆T

PiCCOPiCCO

• AdvantagesAdvantages• CCOCCO• Continuous Volume responsivenessContinuous Volume responsiveness• Short response time 12 secsShort response time 12 secs• Paediatric application >2kgPaediatric application >2kg

• DisadvantagesDisadvantages• Needs CVP and proximal arterial lineNeeds CVP and proximal arterial line• Needs calibrationNeeds calibration

LiDCOLiDCO

• Minimally invasiveMinimally invasive

• Safe, non-toxic rapidly redistributed and no 1Safe, non-toxic rapidly redistributed and no 1stst pass pass effecteffect

• LiCl: 0.002mmol/l injected into central vein LiCl: 0.002mmol/l injected into central vein (peripheral administration possible as well)(peripheral administration possible as well)

• Arterial plasma conc. measured by withdrawing Arterial plasma conc. measured by withdrawing blood across lithium selective electrode at 4ml/minblood across lithium selective electrode at 4ml/min

• CO calculated from Li dose and area under primary CO calculated from Li dose and area under primary concentration-time curve before re-circulationconcentration-time curve before re-circulation

LiDCOLiDCO

Cardiac Output = (Lithium Dose x 60)/(Area x (1-PCV))

AdvantagesAdvantages

• SAFESAFE• Central/peripheral venous and arterial catheters• Injectate is an isotonic (150 mM) solution of lithium

chloride• 0.15 -0.30 mmol for an average adult• patient weight (>40kg) and absence of renal

dysfunction or dialysis

• ACCURATEACCURATE

• SIMPLE TO USESIMPLE TO USE

DisadvantagesDisadvantages

• NMBA interfer with calibrationNMBA interfer with calibration

• AFAF

• iABP iABP

• People on lithium therapyPeople on lithium therapy

• Renal impairmentRenal impairment

• Weight <40kgWeight <40kg

• Pregnancy 1Pregnancy 1stst trimester trimester

• Intra cardiac shuntsIntra cardiac shunts

Flowtrac/VigilleoFlowtrac/Vigilleo

• Continuously computes stroke volume from arterial Continuously computes stroke volume from arterial pressure signalpressure signal

• Requires NO manual calibrationRequires NO manual calibration• Demographic DataDemographic Data• Arterial waveform analysisArterial waveform analysis

• Quantification of SVVQuantification of SVV• Aortic pulse pressure is proportional to SV and is inversely Aortic pulse pressure is proportional to SV and is inversely

related to aortic compliance.related to aortic compliance.• If compliance (and resistance) is constant a bigger SV will mean a If compliance (and resistance) is constant a bigger SV will mean a

greater PP.greater PP.

• Disposable TransducerDisposable Transducer• Latex-FreeLatex-Free• c.£120 per set upc.£120 per set up

Trending Stroke VolumeTrending Stroke Volume

• Arterial pressure is sampled at 100 HzArterial pressure is sampled at 100 Hz

• Changes in stroke volume will result in corresponding Changes in stroke volume will result in corresponding changes in the pulse pressurechanges in the pulse pressure

• A robust “whole waveform” measure of the pulse pressure A robust “whole waveform” measure of the pulse pressure is achieved by taking the standard deviation of the sampled is achieved by taking the standard deviation of the sampled points of each beatpoints of each beat

• sd(sd(APAP) ) Pulse Pressure Pulse Pressure Stroke Volume Stroke Volume

• SV estimates are calculated every 20 secSV estimates are calculated every 20 sec

PP SV

Systolic press.

Diastolic press.

The effect of compliance on PP: The effect of compliance on PP: Age, gender and BSA factors Age, gender and BSA factors

For the same volume ➔

• Younger

• Male

• Higher BSA

• Older

• Female

• Lower BSA

• Compliance inversely affects PP

• The algorithm compensates for the effects of compliance on PP based on age, gender and BSA

vs.vs.vs.

Effect of vascular toneEffect of vascular tone• The algorithm looks for characteristic changes in the The algorithm looks for characteristic changes in the

arterial pressure waveform that reflect changes in tone arterial pressure waveform that reflect changes in tone (i.e., MAP, Skewness, Kurtosis)(i.e., MAP, Skewness, Kurtosis)

• Those changes are included in the continuous calculation.Those changes are included in the continuous calculation.

SkewnessMAP Kurtosis

Error SourcesError Sources

ICOICO CCOCCO FloTrac FloTrac sensorsensor

Comp constantComp constant ------------ Patient dataPatient dataAgeAgeHeight & weightHeight & weightGenderGender

Clinician techniqueClinician techniqueInjectate VolumeInjectate VolumeInjectate TemperatureInjectate TemperatureInjection TimingInjection Timing

------------ AS/AIAS/AI

DysrhythmiaDysrhythmia

Catheter migrationCatheter migration Catheter migrationCatheter migration Sensor heightSensor height

Ventilator timing Ventilator timing Sequential compression Sequential compression devicedevice

Aortic balloon pumpAortic balloon pump

Patient temperature shiftsPatient temperature shifts Patient temperature shiftsPatient temperature shifts Patient arm movementPatient arm movement

Infusions & dripsInfusions & drips Infusions & dripsInfusions & drips Line bubblesLine bubbles

catheter whip (fem)catheter whip (fem)

Valve regurgitationValve regurgitation Valve regurgitationValve regurgitation Pressure dampening Pressure dampening (extreme vasopressors)(extreme vasopressors)

Validation?Validation?

• ‘‘Cardiac Output Determination From the Arterial Pressure Wave: Clinical Testing of a Novel Cardiac Output Determination From the Arterial Pressure Wave: Clinical Testing of a Novel Algorithm That Does Not Require Calibration’ Algorithm That Does Not Require Calibration’ Journal of Cardiothorac and Vasc Anesth 2007. Journal of Cardiothorac and Vasc Anesth 2007.

• ‘‘Uncalibrated pulse contour-derived stoke volume variation predict fluid responsiveness in Uncalibrated pulse contour-derived stoke volume variation predict fluid responsiveness in mechanically ventilated patients undergoing liver transplantation’ mechanically ventilated patients undergoing liver transplantation’ BJA 2008.BJA 2008.

• Still awaiting rigorous validation studies.Still awaiting rigorous validation studies.

True Non-Invasive True Non-Invasive MonitoringMonitoring

TTETTE

• Non invasiveNon invasive

• Similar method of calculation of CO to TOESimilar method of calculation of CO to TOE

• In addition to the limitation of TOE, In addition to the limitation of TOE, obtaining echocardiographic windows in obtaining echocardiographic windows in mechanically ventilated patients can be mechanically ventilated patients can be difficult.difficult.

Transthoracic bio-impedence Transthoracic bio-impedence (Impedence (Impedence Cardiography/ Impedance plethysmograpghy)Cardiography/ Impedance plethysmograpghy)

• 4 dual sensors with 8 lead wires 4 dual sensors with 8 lead wires placed on neck and chestplaced on neck and chest

• Current transmitted and seeks Current transmitted and seeks path of least resistance: blood path of least resistance: blood filled aortafilled aorta

• Baseline impedance (resistance) Baseline impedance (resistance) to signal is measuredto signal is measured

• With each heartbeat, blood With each heartbeat, blood volume and velocity in the aorta volume and velocity in the aorta changechange

• Corresponding change in Corresponding change in impedance is measuredimpedance is measured

• Baseline and changes in Baseline and changes in impedance are used to measure impedance are used to measure and calculate hemodynamic and calculate hemodynamic parametersparameters

ParametersParameters

• MeasuredMeasured– Heart RateHeart Rate– Non Invasive BPNon Invasive BP– Velocity IndexVelocity Index– Acceleration IndexAcceleration Index– Thoracic Fluid Thoracic Fluid

ContentContent– Pre-Ejection TimePre-Ejection Time– LV Ejection TimeLV Ejection Time

• CalculatedCalculated– Stroke Volume / IndexStroke Volume / Index– Cardiac Output / IndexCardiac Output / Index– SVR / SVRISVR / SVRI– LCW / LCWILCW / LCWI– Systolic Time RatioSystolic Time Ratio– Heather Index Heather Index – Ejection Time Ratio Ejection Time Ratio

ICGICG

Validation?Validation?

• Ziegler D, et al. “Comparison of cardiac Ziegler D, et al. “Comparison of cardiac output measurements by TEB vs. output measurements by TEB vs. intermittent bolus thermodilution in intermittent bolus thermodilution in mechanically ventilated patients” mechanically ventilated patients” Chest. Chest. 1999; Vol. 16, No. 4 (suppl. 2):281S.1999; Vol. 16, No. 4 (suppl. 2):281S.

• Scott Sageman, et al. “Equivalence of Scott Sageman, et al. “Equivalence of Bioimpedance and Thermodilution in Bioimpedance and Thermodilution in Measuring Cardiac Index After Cardiac Measuring Cardiac Index After Cardiac Surgery”Surgery” J Cardiothoracic & Vasc. Anesth. 16:8-J Cardiothoracic & Vasc. Anesth. 16:8-14, 200214, 2002

ConclusionsConclusions

• Correctly powered and vigorous validation studies still Correctly powered and vigorous validation studies still awaited for ICG and Flotrac/vigileo.awaited for ICG and Flotrac/vigileo.

• PAC/LiDCO/PiCCO/Oesophageal doppler/TOE all validated PAC/LiDCO/PiCCO/Oesophageal doppler/TOE all validated for select patient groups. Knowing limitations of each for select patient groups. Knowing limitations of each monitoring system vital when deciding which to employ. monitoring system vital when deciding which to employ.

• Absolute numbers vs trends.Absolute numbers vs trends.

• No outcome improvement data with use of CO monitoring.No outcome improvement data with use of CO monitoring.

• Clinical examination.Clinical examination.

• The information obtained is only as useful as the person The information obtained is only as useful as the person interpreting it and using it to modify patient Rx.interpreting it and using it to modify patient Rx.

A fool with a tool is still a A fool with a tool is still a fool.fool.