Download Non Invasive Haemodynamic Monitoring

Non Invasive Haemodynamic
Monitoring
Nick Harrison
BACCN May 2015
• Hemodynamic monitoring is a cornerstone of care
for the hemodynamically unstable patient, but it
requires a manifold approach and its use is both
context and disease specific.
• One of the primary goals of hemodynamic
monitoring is to alert the health care team to
impending cardiovascular crisis before organ injury
ensues.
Does it matter which haemodynamic
monitor to use?
• “Finally, no monitoring tool, no matter how
accurate, by itself has improved patient
outcome”….
Pinskey et al (2005)
Adolf Fick
The principle:
" the total uptake of (or release of) a substance
by the peripheral tissues is equal to the product
of the blood flow to the peripheral tissues and
the arterial-venous concentration difference
(gradient) of the substance."
It is the blood flow we are interested in: this is
cardiac output…….
Fick – The True Gold Standard
VO2, the oxygen consumption, is simply the difference between the inspired and expired O2. You
can measure it with an exhaled gas collection bag.
You can also estimate it. Conventionally, resting metabolic consumption of oxygen is
3.5 ml of O2 per kg per minute,
or
125ml O2 per square meter of body surface area per minute.
Lets say the meaty pinkish lump below is the patient.
http://www.derangedphysiology.com/php/PAC/
Fick teaches us that VO2 (oxygen extraction) is determined by the following equation:
We can rearrange that to form an equation which calculates cardiac output on the basis of
oxygen extraction:
So, in a normal person, with a body surface area of 2m2 and thus with a VO2 of 250ml per
minute,
CO = 250ml / (200ml – 150ml)
= 250 / 50
= 5 L/min
Where are we Now?
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Bolus thermodilution
Transpulmonary thermodilution
Lithium dilution
Doppler technique
Pulse contour analysis
Carbon dioxide rebreathing
Bioimpedence / Bioreactance
Echocradiography
Peripheral pulse variation
Choices, Choices……
Things to consider……
Theoretical considerations for choosing among
hemodynamic monitoring tools
Hardware considerations for choosing among
hemodynamic monitoring tools
Patient-bound considerations for tailoring
hemodynamic monitoring
Slagt et al. Critical Care 2010, 14:208
The New Gold Standard
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Problems
Extreme level invasiveness
Advanced training for placement
Incorrect parameter interpretation
Complications
• Arrhythmias
• Pulmonary rupture
• Air embolism
Most studies focusing on the PAC and outcome have shown no positive association
between PAC use for fluid management and survival in the ICU.
Wheeler et al. N Engl J Med 2006, 354:2213-2224
Doppler Technology
Prof Mervyn Singer is Professor of Intensive Care Medicine at University College
• First described in mid 1970’s and gained popularity in
(Gan and Arrowsmith)
the 1990’s
• Measures blood flow velocity in the descending
aorta using flexible ultrasound probe ( 4-5MHz).
• Measurement combined with estimated cross
sectional area of aorta, age, height and weight give
haemodynamic variables
Values
• Stroke Distance:
• Distance in cm column of blood moves along
aorta with every ventricular beat
• Changes in SD directly related to stroke volume
• Stroke Volume
• Amount of blood ejected by heart each beat
• Flow time Corrected (FTc)
• Is the duration of flow during systole corrected for the heart rate (330 – 360ms)
• Peak Velocity
• Highest blood velocity during systole
• Age dependent PV
Age
20yrs
90-120cm/s
50yrs
70-100cm/s
70yrs
50-80cm/s
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Minimally invasive
Minimal technical skill required for insertion
Good correlation with PAC.
Recommended for use in high risk surgery (NICE)
Remember
• Cross section must be accurate
• Ultrasound beam must be directed parallel to the blood flow
• Beam direction must NOT undergo any major alterations between
measurements
(King and Lim (2004), Kauffamn (2000), Prentice and Sonna (2006), Lavdaniti (2008), Tomlin (1975), NICE 2011)
Transpulmonary Thermodilution and Pulse Contour
Cardiac Output
Systems can be divided into 3 categories:
• Pulse contour analysis requiring and an indicator dilution
CO measurement to calibrate the pulse contour (LiDCO™,
PiCCO™, Volumeview™)
• Pulse contour analysis requiring patient demographic and
physical characteristics for arterial impudence estimation
(FloTrac, NextFin, Radical 7).
• Pulse contour analysis that does not require calibration or
preloaded data (Most Care System)
Pulse Contour Analysis
The origin of the pulse contour method of measuring cardiac output is derived from
variations in the pulse pressure waveform.
In general, the greater the stroke volume, the greater is the amount of blood that
must be accommodated in the arterial tree with each heartbeat and, therefore, the
greater the pressure rise and fall during systole and diastole, thus causing a greater
pulse pressure.
The pulse pressure is proportional to stroke volume and inversely related to vascular
compliance.
“Aortic pulse pressure is proportional to SV and is inversely related to aortic
compliance.”
(Chest 2002)
• Stroke Volume (Pulse pressure ~ Stroke Volume)
• Aortic Compliance (As the compliance of the vasculature is difficult to measure
directly, this is calculated based on age, sex, ethnicity and body mass index
(BMI)) Brumfield AMPhysiol Meas 2005;26:599–608
• Vascular Tone (clinical condition and therapeutic approach)
LiDCO
• First described in 1993
http://www.ebay.com/itm/LiDCO-Plus-Hemodynamic
• Combines pulse power analysis with lithium dilution
technique
• Requires a venous line and arterial catheter
• Lithium is injected via vein and arterial concentration
sampled across a lithium electrode at a rate of 4mls/min.
• Provides an accurate calibration and corrects for arterial
compliance and variation among individuals.
Power pulse analysis – the magnitude in change of pressure is equal to the
magnitude of change in stroke volume
The heart rate is calculated by drawing an imaginary line through the
arterial waveform.
Cardiac output in PulseCo is an estimated figure due to assumption of
aortic compliance (Remington et al 1948) – uses accepted figure of 250mls.
People vary so necessary to calibrate:
ΔV / Δbp = calibration x 250 x e –k.bp
Advantages
• Any arterial site can be used.
• Damping effects of the transducer system is
reduced.
• Safe and accurate (Hett & Jones 2003)
• Can be calibrated with any form of CO
measurement
• Good correlation with PAC (Costa et al 2008)
• Calibration can be time consuming
• Expense
• Not recommended
• in first trimester of pregnancy
• Under 40kgs
• Patients receiving NMB can cause delay
• Aortic valve regurgitation
Transpulmonary Thermodilution and Pulse
Contour Analysis (TPCO)
PiCCO and VolumeView
• Requires a central vein catheterisation and arterial catheter
(femoral preferable)
• Continuous pulse contour SV is calculated from the area
under systolic portion of the arterial waveform
• Shape of arterial waveform, arterial compliance, SVR
• These devices use the same basic principles of dilution to
estimate the cardiac output as with PAC thermodilution
VolumeView sensor
VolumeView femoral arterial catheter
VolumeView thermistor manifold
CVC standard
TruWave pressure transducer
EV1000 clinical platform
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MICROSITE
•CO - Calibrated Cardiac Output
•SV - Calibrated Stroke Volume
•SVR - Systemic Vascular Resistance
•SVV - Stroke Volume Variation
•SVI - Stroke Volume Index
Volumetric Parameters
•EVLW - Extravascular Lung Water
•PVPI - Pulmonary Vascular Permeability
Index
•GEDV - Global End Diastolic Volume
•GEF - Global Ejection Fraction
• Advantages
• Continuous cardiac output monitoring
• Good accuracy
• Disadvantages
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Can be complicated to set up
Needs specific femoral artery catheter
Remains significantly invasive
Can be effected by arrhythmias
Vigileo™
• Each of these systems contains a proprietary algorithm for
converting a pressure-based signal into a flow
measurement.
• Needs no external calibration
• Use the equation SV = SDAP x (Khi)ᵡ
• Analyses the area under the systolic portion of the arterial
pressure waveform from the end diastole phase to the end
of the ejection phase – corresponds to SV.
The pulse pressure is obtained by the complete analysis of the arterial waveform and
through the calculation of the standard deviation (sd) at each sample points.
(sampling rate of 100Hz results in 2000 data points)
•sd(AP) ~ Pulse Pressure ~ Stroke Volume
•The SV value is updated every 20 seconds
APCO
algorithm
The variations or changes in the vascular tone are integrated in a continuous
calibration factor (Khi “x”) obtained from a multivariate equation of two major
elements :
Biometric variables : age, sex, height (Langewouters et al.)
Shape variables : analysis of the different characteristics of the arterial pressure
waveform.
Skewness (Dissymmetry coefficient)
Kurtosis (Flattening coefficient)
Pulsatility
Advantages
• Easy to set up
• Needs no external calibration
Areas of Concern
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Outdated and superseded…
Over the past 5 years and many
software updates much research
has identified the Vigileo as
inaccurate at determining
haemodynamic variables within
a host of critical care patients.
Poor accuracy with arrhythmia.
SVV only reliable in mechanically
ventilated patients
Requires specific arterial
pressure sensor
Cannot track changes in large
vasomotor swings..
Partial CO2 Rebreathing
• Uses the Fick principle with CO2 as the marker gas
• System distributed is called NICO (Philips)
(Berton & Chorley 2002)
• The CO2 partial rebreathing technique compares end-tidal
carbon dioxide partial pressure obtained during a nonrebreathing period with that obtained during a subsequent
rebreathing period.
• The ratio of the change in end-tidal carbon dioxide and CO2
elimination after a brief period of partial rebreathing
(usually 50 seconds) provides a non-invasive estimate of
the CO.
Partial CO2 rebreathing (NICO™)
*minimal tidal volume = 200ml
There are several limitations to this device including:
• The need for intubation and mechanical ventilation with fixed
ventilator settings and minimal gas exchange abnormalities.
Gueret G et al Eur J Anaesthesiology (2006), 23:848–854
• Variations in ventilator settings, mechanically assisted spontaneous
breathing, the presence of increased pulmonary shunt fraction, and
hemodynamic instability have been associated with decreased
Tachibana K et al Anaesthesiology (2003), 98:830–837
accuracy.
• Considering the limitations of this technology and the potential
inaccuracies, the routine use of the CO2 rebreathing technique to
guide fluid and vasopressor therapy cannot be recommended.
Thoracic Electrical Bioimpedance
impedance = measure of opposition to alternating
current (AC)
How it works:
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superficial electrodes applied to chest that
both measure and apply voltage
current is transmitted through the chest via
the path of least resistance (aorta)
portion of initial (known) voltage that
reaches a distant sensing electrode is
measured
baseline impedance to the current is
recorded
with each heartbeat, blood volume and
velocity in the aorta change 
corresponding change in impedance
change in impedance used to calculate
stroke volume and cardiac output according
to algorithm based on changes in thoracic
blood volume
http://www.microtronics-nc.com
Bioimpedance / Bioreactance
• Developed since the 1960’s (NASA)
• 4 electrodes in pairs – each pair comprises transmitting and
sensing properties
• High frequency current of known amplitude and frequency
across the chest measures changes in voltage.
• Ratios between voltage and current amplitudes =
impedance (Zo), and varies in proportion of amount of fluid
in the chest.
• Changes in impedance correlates with SV:
Cheetah NICOM
CAPTURES (14 ) PARAMETERS
“In Real Time”
CO
Cardiac Output
SV
Stoke Volume
CI
Cardiac Index
SVV Stroke Volume Variance
SVI
HR
Stroke Volume Index
Heart Rate
TPR Total Peripheral Resistance
VET
Ventricular Ejection Time
MAP Mean Arterial Pressure
NIBP Non Invasive Blood Pressure
TPR :
TPR :
TFCd :
CP:
CPI:
SVR
Dynes – (MAP / CO)*80
mmHg * min./liters – (MAP / CO)
% Change in TFC over 15 mins. Vs. baseline TFC
MAP*CO/451
CP/BSA
MAP-CVP / CO
TFC
Thoracic Fluid Content
CP
Cardiac Power
TFCd % Directional Change in
TFC/Time
CPI
Cardiac Power Index
Limitations
• However, a poor correlation between derived CO and that determined by
thermodilution in the setting of a cardiac catheterization laboratory was reported.
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In the Bioimpedance CardioGraphy (BIG) substudy of the ESCAPE heart failure
study, there was a poor agreement among TEB and invasively measured
Kamath et al (2009) Heart J 158:217-223.
hemodynamic profiles.
• Bioimpedance has been found to be inaccurate in the intensive care unit and other
settings in which significant electric noise and body motion exist and in patients
with increased lung water.
Gujjar et al (2008) J Clin Monit Comput 22:175-180.
• Furthermore, this technique is sensitive to the placement of the electrodes on the
body, variations in patient body size, and other physical factors that impact on
electric conductivity between the electrodes and the skin (eg, temperature and
humidity)
This device provides a non-invasive estimation
of cardiac output in two steps
For this purpose, the device includes an inflatable cuff that is wrapped
around a finger. It also includes a photoplethysmographic device that
measures the diameter of the finger arteries.
At each systole, the photoplethysmographic device senses
the increase of the finger arteries’ diameter. A fast servo controlled system
immediately inflates the cuff in order to keep the arteries’ diameter
constant. Therefore, cuff pressure reflects the arterial pressure. Its
continuous measurement allows estimation of the arterial pressure curve.
The second step is to estimate cardiac output from the non-invasive arterial
pressure curve. For this purpose, the Nexfin device includes pulse contour
analysis software that computes cardiac output from the arterial
pressure curve
Stroke
Volume
10 %
Lower PVI = Less likely to respond
to fluid administration
24 %
0
0
Maxime Cannesson, MD, PhD
Preload
Pleth variability index (PVI) is a new algorithm allowing automated and
continuous monitoring of respiratory variations in the pulse oximetry
plethysmographic waveform amplitude.
PVI can predict fluid responsiveness noninvasively in mechanically
ventilated patients during general anesthesia
http://anesthesiology.queensu.ca/assets/LAB4583B_Technical_Bulletin_Pleth_Variability_Index.pdf
Echocardiogram
• Although echocardiography traditionally is not
considered a monitoring device, both
transthoracic and transesophageal
echocardiography provide invaluable information
on both left and right ventricular function, which
is crucial in the management of hemodynamically
unstable patients.
Levitov et al (2012) Cardiol Res Pract:819-696
Salem et al (2008) Curr Opin Crit Care 14:561-568
Choose wisely….
Algorithms …
Remember….
Treat the patient… Don’t treat the
monitors…
Depending on the clinical setting, adequate
monitoring can definitely help the
clinician to better treat his patient and
improve the final outcome.
Maybe in the Future our patients will
look like this!!
• Oxygenation
• Perfusion
Any Questions