Are less Invasive Techniques

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Are less Invasive Techniques for Measuring
Cardiac Output as accurate as the Pulmonary
Artery Catheter ?
Frances Colreavy Mater Misercordiae Hospital
Intensive Care Society of Ireland Summer Meeting
2007
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Pulmonary Artery Catheter (PAC)

• Most commonly used device for measuring Cardiac
  Output
• in intensive care practice
• Reference method against which new methods are
  compared

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Pulmonary Artery Catheter Cardiac Output
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1990s The Pulmonary Artery Controversy
Non-randomized trials in critically ill
patients suggested the PAC is associated with
increased morbidity and mortality
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There followed a period of debate and soul
searching among Intensivists
Is this how Intensivists are viewed? Intense and
Deep thinkers
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Pulmonary Artery Catheter early 2000
RCTs

• Rhodes et al Intensive Care Medicine 2002 28
  256-264
• 201 patients
• renal failure (22/12), LOS hosp. (13/14), death
  (46/50)
• Sandham et al NEJM 2003 348 5-14
• 1994 patients
• death hosp. (78/77), death 360 d (163/155),
• Harvey et al Lancet 2005 366 472-477 (PAC-Man)
• 1041 patients
• LOS ICU (no diff), mortality (68/66)
• ESCAPE investigators JAMA 2005 294 1625-1633
• 433 patients NYHA IV,
• No difference in mortality or days
  hospitalized

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Why are we still tinkering with the same
question?
Is this how Intensivists are viewed?
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Conclusion The PAC is not associated with
increased mortality or mortality in critically
ill patients
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Increasing number of new technologies for
monitoring cardiac output
Clinical utility adults

• Track stroke volume from arterial waveform
• Track stroke volume using Doppler theory

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Arterial waveform tracking technologies
Stroke Volume
Universally measured variable in critically ill
patients
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PiCCO
Arterial Pulse Contour Analysis
LiDCO
Vigileo
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Each method requires a calibration system
mmHg
Pressure
Arterial compliance
Systole
Litres/min
Volume cardiac output
Diastole
In vivo calibration
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PiCCO plus
Calibration Thermodilution cardiac output

• Any standard central line
• A thermistor-tipped arterial PiCCO catheter,
  brachial, femoral,
• radial

Additional Extravascular Lung water

• Pulmonary oedema formation

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PiCCO plus
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Central venous injection cold or room temp.
saline bolus
CO calculated using modified Stewart-Hamilton
algorithm
Thermistor tip of arterial catheter measures the
downstream temperature change
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Extravascular Lung Water
ITTV
PTV
Bolus injection
Thermodilution curve
Lungs
RVEDV
LVEDV
RAEDV
The intrathoracic compartments a series of mixing
chambers for the distribution of the injected
indicator
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All volumetric parameters obtained advanced
analysis of thermodilution curve
Mean transit time ½ indicator thermistor MTt
down slope time DSt
Mean transit time x CO Intrathoracic thermal
volume Down slope time x CO Thermal volume of
the lungs
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Intrathoracic thermal volume
ITTV
Bolus injection
Thermodilution curve
Lungs
RVEDV
LVEDV
RAEDV
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Global End-diastolic Volume
Volume blood contained in 4 chambers of heart
ITTV minus PTV
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Intrathoracic Blood Volume
Volume of 4 chambers blood volume pulmonary
vessels
25 greater than GEDV
Pulmonary blood volume
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Extravascular Lung Water
The water content of the lungs,
bedside quantification of pulmonary oedema

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Comparision to pulmonary artery thermodilution
24 patients change in cardiac output gt 20 50
patients required vasopressor support 517
measurements CO
Bias -0.2 1.2 L/min
Bland Altman analysis
Godje et al, Crit Care Med 20023052
gt 250 articles PiCCO technology
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LiDCO plus
Calibration lithium transpulmonary
thermodilution

• peripheral lines/central line
• lithium sensor
• attached to arterial line

Additional Pulse pressure variation
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LiDCO
A bolus of Lithium Chloride is flushed through a
central or peripheral venous line
Contraindications to lithium
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LiDCO
Lithium Chloride sensitive sensor attached to a
peripheral arterial line
Detects the concentration of Lithium Chloride
ions in arterial blood
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LiDCO
Lithium Chloride indicator dilution
washout-curve provides accurate absolute CO
value
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Bulky additional equipment around bed
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Pulse Pressure Variation
Pulse Pressure Variation gt 13 sensitive and
specific preload responsiveness
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Comparision to pulmonary artery thermodilution
34 patients ICU gt 24 hours, mean CO 6L/min,
range 3.5 - 10.5 Bland Altman analysis Bias
-0.2 1.2 L/min
Pittman et al, Critical Care Med 2005 92015
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Vigelo/Flotrac

• Flotrac transducer incorporated into monitor
• Device does not require calbration
• Compliance and resistance are derived from
  analysis
• arterial waveform (shape of arterial waveform
  )
• Heart rate, BSA

Least validated, show reasonable bias and
precision Least number of critically ill
patients
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Oesophageal Doppler
Measures blood flow in descending aorta
doppler transducer, CO wt/height
Anaesthetized, mechanically ventilated patients
10 probe insertion transducer towards
aorta Interobserver variabilitylt
10 Intraobserver variability lt 8
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Oesophageal Doppler Flow Time Indices
VTI
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Cardiac Output
(1) Velocity time integral stroke distance (2)
Cross-sectional area aorta (3) Correcting
factor descending aortic flow to global CO
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Comparision to pulmonary artery thermodilution
Good correlation with Thermodilution CO Bias
-0.01, Limits of agreement -2.2 to 2.33L/min
Better in study conditions, than in busy ICU
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Echocardiography (Two dimensional doppler)
New Operators Intensive Care Physicians
New Technology Harmonic Imaging
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Echocardiography in Intensive Care
1990s TOE Intensive Care
gt 2000 Echocardiography Intensive Care
The use of Echocardiography in the critical care
setting Stamos TD. Critical Care Clinics 2001
Apr 17(2) 253 ICU Echocardiography, Should we
use it in a heartbeat? Ketzler t. Chest 2002 Oct
122 (4) 1370 Echocardiography a fundemental
part of the intensive care curriculum. Ribero J.
Critical Care 2002 Apr 6 175
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Fundamental
Near the skin, very few harmonics are produced
Harmonics
Signal strength
At usual imaging distances, harmonics are much
stronger
Distance (cm)
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Cardiac Output

• Cross-sectional area of aorta
• Stroke volume

• r2 x VTI stroke volume x HR Cardiac Output

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Ultrasound waves meet tissues!
Transducer
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Measurement of LVOT cross-sectional area
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Ultrasound waves meet red blood cells!
Doppler ultrasound determines the speed and
direction of blood
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Colour-flow doppler
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69
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69
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Stroke Volume
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Pulse wave doppler mitral inflow
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Estimation of cardiac preload
Mitral inflow
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Tissue doppler mitral annulus
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Colour M-mode
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Additional (First prize!) Ejection fraction,
right and left Two dimensional anatomy (Mitral
valve, LV function, VSD, aortic dissection
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Pulmonary Artery Catheter (PAC)

• Most commonly used device for measuring Cardiac
  Output
• in intensive care practice
• Reference method against which new methods are
  compared

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How I view Intensivists
I want to work with the top people, because
only they have the courage and the confidence
and the risk-seeking profile that you need
James Joyce 1882-1941
Bloomsday June 16th 20007
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