Download The Importance of Cardiac Output Monitoring in Paediatric

The Importance of Cardiac
Output Monitoring in
Paediatric Management
Dr Joe Brierley
Paediatric and Neonatal Intensive Care Units
Great Ormond St Hospital
London, UK
Cardiac function
n
Systolic AND diastolic function
• Systolic function
• Diastolic function
n
n
rate and degree of ventricular relaxation
both active and passive components
Cardiac Function-Systolic
n
Systolic cardiac function
• interaction of four interdependent factors:
Heart rate
n Preload
n Contractility
n Afterload
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n
Heart rate measurable
Preload - invasive pressure - CVP/PA wedge
Contractility and afterload -difficult (FS/conductance/SVR)
n
ICU cardiac function - bedside cardiac output
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Cardiac function
Adequacy of cardiac output and oxygen delivery
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Global assessment
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n
n
MVO2
lactate
Regional assessment
n
n
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n
capillary refill
core-peripheral temperature gap
splanchnic oxygen delivery-gastric tonometry
secondary organ effects
• renal/hepatic/neurological failure
Assessing circulatory
disturbances
n
Clinical estimate of cardiac output poor (1)
n
‘Clinicians substitute BP for flow’
• no correlation between flow + pressure
n
Plethora of methods to estimate CO
• each potential for measurement errors
• requirement for technical expertise may limit utility
• degree of invasiveness required ⇒ incremental risk to pt
1) Tibby S et al. Clinicians’ abilities to estimate cardiac index in ventilated
children and infants. Arch Dis Child 1997;77:516–18
Caveat
n
Flow without Hb + art’ sats - ?misleading
n
Cellular viability depends
• O2 delivery (CO X arterial oxygen content)
• O2 extraction
n As well as CO
Cardiac output
n
Volume of blood ejected by heart per minute
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NB Interplay - HR preload contractility + afterload
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Manifestation of cardiac function measurable at bedside
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In children indexed to BSA-cardiac index
• same “normal” value
n -3.5–5.5 l/min/m2 regardless age/size
Why Measure CO in ICU
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n
n
n
n
CVS one of commonest organ failures in PICU (Wilkinson)
Other organ failure/support effects myocardial function
- eg ventilation/CVVH
Low flow state
• high mortality in certain diseases (Mercier JC et al)
Flow poorly estimated clinically (Tibby et al)
• Hence titrate treatment against BP!
Adequate organ perfusion pressure vital
• BUT BP affected by CO and SVR
•Wilkinson et al. Outcome of pediatric patients with MOSF. Crit Care Med 1986;14:271–4
•Mercier JC et al Hemodynamic patterns of meningococcal shock in children. CCM 1988;16:27
•Tibby et al Clinicians’ abilities to estimate CI in ventilated children and infants. Arch Dis Child 1997;77:516–18
When to measure CO
n
n
Not all children in ICU
Risk v benefit Risk
? children outside ICU
Patient selection
Method used
n
Benefit
Understand haemodynamics
Thompson A. Pulmonary artery catheterization in children. New horiz 1997;5:244–50
n
• Shock states
• Congenital and acquired heart disease
• Multiple organ failure
• Cardiopulmonary interactions during mechanical ventilation
Also
• Research
• Monitoring effects of drugs eg anaesthetic agents
• ? Role in early goal therapy prior to ICU
Accuracy vital as ultimate aim to change therapy
When to measure CO in ICU
n
Evidenced based medicine
• CO not (yet) convincingly shown to improve outcome
n
But same for many monitoring procedures
•
•
•
•
invasive arterial pressure
CVP measurement
blood gas analysis
pulse oximetry
• NB CVO2
Anyone like to NOT know
her cardiac output?
Flow more important
than pressure!
Goal Therapy-Adjustments in:Modality
Gold standard
ICU manipulation
Pre-load
LVEDP
fluids/CVP
Systolic function
Contractility (conductance)
Inotropes
Diastolic function Relaxation
(ino-)Dilators
Afterload
SVR
Ventriculo-arterial
coupling -Ees/Ea
Aim to balance O2 delivery with O2 demand
n
End points
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Normalized MVO2
Arterial lactate
Base deficit
pH
Goal Therapy
n
MVO2
• Good surrogate for cardiac index
(assuming constant
n
n
-O2 consumption, Hb concentration, arterial O2 saturation)
Gattinoni et al. A trial of goal-oriented hemodynamic therapy in critically ill
patients. N Engl J Med 1995;333:1025-32
CVO2
• Reasonable surrogate for MVO2
n
Reinhart et al. Comparison of CV to MV O2 sats during changes in O2
supply/demand.Chest 1989;95:1216-21
Paediatric Sepsis
n
? Manipulation other variables equally successful
n
n
Eg Cardiac output
? Any of this valid in children
Role of early fluid resuscitation in pediatric septic shock. Carcillo JA, Davis AL, Zaritsky A. JAMA
1991 4;266(9):1242-5
40 mL/kg in the first hour following ED presentation
associated with: improved survival
Early Reversal of PediatricPediatric-Neonatal Septic Shock by Community Physicians Is Associated With Improved
Outcome
Yong Y. Han, Joseph A. Carcillo,
Carcillo Michelle A. Dragotta, Debra M. Bills, R. Scott Watson, Mark E.
Westerman, and Richard A. Orr. Pediatrics, Oct 2003; 112: 793 - 799.
Each extra hour of shock: 2.3x risk of death
Ideal characteristics
-CO device
• Non-invasive
• Applicable to many patients
• Applicable over a wide range of flow
• Accurate (cf other techniques)
• Reproducible
• Easy to use
• Rapid data acquisition
• Cost effective
How to measure cardiac output
n
Invasive
• Dilution techniques
• Dye dilution
• Pulmonary artery
thermodilution
• Transpulmonary
thermodilution
• Lithium dilution
• Direct Fick
n
Non-Invasive
• Non-invasive Fick
using CO2
• Bioimpedance
• Echocardiography
• Trans-oesophageal
doppler
• Pulse contour analysis
• Supra-sternal/USCOM
PA catheter
Swan HJ et al. Catheterization of heart in man with flow-directed, balloon-tipped
catheter. N Engl J Med 283:477, 1970
n
Traditional ICU estimation CO
• cold dextrose ⇒ Rt atrium
⇒ PA temp’ change (thermistor)
• CO calculated- temperature time curve
• Disadvantages
n technical limitations
n catheter-related problems
n Usually on ICU
n skilled operator (1,2)
n
n
(1) Iberti T et al. A multicenter study of physicians’ knowledge of PA catheter. JAMA. 1990;264:2928–32
(2) Gnaegi A, Feihl F, Perret C. Intensive care physicians’ insufficient knowledge of Rt-heart catheterization at bedside: time to act? CCM
1997;25:213–20
Measuring Cardiac Output
Invasive
Adolph Fick 1870
Fick equation -‘gold standard’
CO calculated →
n
Art-Venous-O2 content difference & O2 consumption
• O2 consumption (spirometry) and O2 content (ABG)
• MVO2 needs PA catheter
•
•
technical skill -unfeasible as routine
several devices use variants
Measuring Cardiac Output- Invasive
Fick principle with CO2
n
Total Re-breathing Cardiac Output
CO2 not eliminated-exhaled CO2 approaches MVCO2
Et CO2 - non-invasive estimate of PaCO2
Pulse contour analysis
"Upon the amount of blood that is thrown out by the
heart during systole then, does the magnitude of
the pulse-pressure in the aorta depend“
1904 Erlanger and Hooker
• Relation CO and arterial pulse contour
Pulse contour analysis
PiCCO
•
•
•
•
Area under systolic portion of pulse pressure waveform
Calibration -transpulmonary thermodilution
4-Fr arterial probe -so older children
Now 1.3 Fr probe
PICCO-parameters obtained
Transpulmonary
Thermodilution
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n
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Transpulmonary CO
Intrathoracic blood volume
Global end-diastolic volume
Extravascular lung water
Pulmonary vascular
permeability index
Cardiac Function Index
Global Ejection Fraction
Continuous Pulse
Contour Analysis
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Continuous Pulse Contour CO
ABP
Heart Rate
Stroke Volume
Stroke volume variation
SVR
Index of left ventricular
contractility
Pulse pressure variation
Pulse contour analysis
PulseCO [LiDCO, UK)
Frequency analysis
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aortic impedance
aorta-radial transfer function
aortic flow
radial pressure
Need radial arterial line
+ calibration -lithium dilution
infants and children
Partial Rebreathing Cardiac Output
Indirect Fick (Non Invasive -NICO)
n
VCO2 = CO x (CvCO2 — CaCO2) But CvCO2 ‘invasive’
n
Assuming CvCO2 + CO constant 3 mins
• VCO2N-VCO2R = CO x (CaCO2R-CaCO2N)
→ CO = (VCO2N—VCO2R)/(CaCO2R-CaCO2N)
*Pulmonary shunt correction computed
Cardiac Output
Non-invasively -Doppler
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Suprasternal and pulmonary
Transgastric
Trans-oesophageal
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Oesophageal Doppler CO
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• described 1971, refined 1989
• validated in children
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Use of trans-oesophageal Doppler ultrasonography in ventilated pediatric
patients: Derivation of cardiac output. Tibby et al. Critical Care Medicine:
28(6) June 2000 pp 2045-2050
Technical basis for technique
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Concept
flow in cylinder = CSA of cylinder X velocity of fluid in cylinder
n
For aortic blood flow
• movement of blood pulsatile and velocity changes with time
⇒Velocity characterized by area under velocitytime curve between two points in time
Oesophageal Doppler
In ICU
Ideal characteristics continuous CO device
• Non-invasive
• Automatic and non-operator dependent
• Accurate (compared to other techniques)
• Continuous, real time data display
• Easy to use
• No calibration required
• Cost effective
USCOM-suprasternal aortic +
pulmonary
USCOM CARDIAC OUTPUT MONITORING
ON RETRIEVAL
JJ Brierley and MJ Peters. Paediatric Intensive Care unit. Great Ormond St Hospital, London, UK
0.3
0.2
0.1
Intermeasurement
Variability in
CI l/min/m2
0
0
1
2
3
4
5
6
7
Mean
CI
-0.1
-0.2
-0.3
-0.4
0.3
0.2
0.1
Intermeasurement
0
Variability in CI
0
l/min/m2
-0.1
-0.2
-0.3
-0.4
2
4
6
8
10
12
14
Age (ye ar s )
12 retrievals
Range of ages 6 months-12 years
Differing diagnosis
Results:
36 cardiac outputs performed
4 successful readings per case
Median time to obtain data 7 minutes
Cardiac index-low variability -across
range of ages and mean cardiac
index
When to measure CO with USCOM
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EARLY goal therapy AND
RETRIEVAL
• (-NB CvCO2 invasive in coagulopathic septic infant)
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ICU
• USCOM
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PORTABLE
ROBUST
Accurate in adults, paed study being done
The Future
Benefits of cardiac output
Early warning monitoring
Rational fluid and drug administration
Decreased procedural complications
e.g. bolus injections/vascular access
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Use for CVS physiology in well children
Smart resuscitation
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•
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ie Early Goal directed therapy
Prospect of outcome modification
? Questions