Prof Şerban Bubenek MD 1 st Cardiovascular Anesthesia amp Intensive Care Dept CCIliescu Institute for Cardiovascular Diseases Bucharest ROMANIA TODAY we speak about ID: 785000
Download The PPT/PDF document "CLINICAL MEASUREMENT topics" is the property of its rightful owner. Permission is granted to download and print the materials on this web site for personal, non-commercial use only, and to display it on your personal computer provided you do not modify the materials and that you retain all copyright notices contained in the materials. By downloading content from our website, you accept the terms of this agreement.
Slide1
CLINICAL MEASUREMENT topics
Prof. Şerban Bubenek MD1-st. Cardiovascular Anesthesia & Intensive Care Dept« C.C.Iliescu » Institute for Cardiovascular DiseasesBucharest - ROMANIA
Slide2TODAY we speak about :Arterial Pressure Measurement
Cardiac Output Measurement
Slide3.
Every patient receiving general anesthesia shall have, in addition to the above, circulatory function continually evaluated by at least one of the following: - palpation of a pulse - auscultation of heart sounds - monitoring of a tracing of intra-arterial pressure - ultrasound peripheral pulse monitoring - pulse plethysmography or oximetry !
Slide4no universal ‘target blood pressure value’ to define intra-operative hypotension
but: - decreases >20% in MAP or for cumulative durations of > 30 minutes - MAP < 60 mmHg ↑ risk of post-op.: MI, stroke, and death. (104,245,246) IIb B Efforts should be made to prevent intra-operative arterial hypotension and inadequately deep anaesthesia.
Slide5Essential requiremets for CLINICAL MEASUREMENT
ACCURACYis the difference between: the measurements and the real biological signal - in practice, is Δ between: a certain technique vs. a superior 'gold standard‘ techniquePRECISION =
reproducibility
of repeated measurements of the same biological signal.
-
calibration is important
( against predetermined signals or for absolute measurements to zero)
Slide6.
MEASUREMENT of ARTERIAL PRESSURE a wide range of instruments are used to measure pressure :liquid column manometers : height, zero point, fluid densitymechanical pressure gauges : aneroid manometerdiafragm gauges (coupled to transducers)
Slide7MEASUREMENT OF ARTERIAL PRESSURE
INDIRECT measurement (non-invasive & not-continous ) - signals generated by the occlusion of a major artery using a cuff - gives not continous but intermittent measurements a. palpation method ( Riva Rocci)
b. auscultation of the Korotkoff
sounds
c.
oscilometry
method
DIRECT measurement (invasive and continuous)
Slide8Indirect Methods of BP measurement (1)
1. Riva Rocci: simplest method of BP measurement, estimating only the SBP, is by palpating the return of arterial pulse as cuff is deflated.2. Auscultation of the Korotkoff sounds : both SBP and DBPon deflation created by the turbulent blood flow in the artery
Mean Arterial Pressure (MAP) = (SBP + 2 DBP) / 3
Slide9Indirect Methods of BP measurement (2)
3. OSCCILOMETRY - a microprocessor controlled oscillometer: DINAMAP- a pressure transducer that digitalizes signals ( microprocesor). - rapid, accurate, measurements of SBP, DBP, MAP and HR - SAP = the onset of rapidly increasing oscillations
-
MAP
=
the
maximal oscillation
at the lowest cuff pressure
-
DAP
corresponds to
the onset of rapidly decreasing oscillations
LIMITATIONS:
tendency to:
overestimate at low pressures and underestimate at high pressures
errors :
movements, arrhythmias or rapid BP fluctuations
-
compressive peripheral nerve injuries
(repeated measurements )
Slide10Cuff Size !
Too small cuff will result in false high blood pressure readingToo large cuff will result in false low
blood pressure reading
Slide11DIRECT Measurement of the BP
invasive : a catheter into the artery METHODS 1. open Liquid column method : it is obsolete and it measures only MAP! 13.4 cm. H2O = 10 mm.Hg. !
2. Liquid manometers
(obsolete)
3.
Electromechanical transducers
:
-
conversion of mechanic signal into an electric signal
-
and then electronically converted and displayed as :
SAP, DAP, MAP
Electromechanical
transducersThe diaphragm : - is moved by arterial pulsations which push the saline columnshould be thin, small and rigid !Transducer : - based upon strain gauge principle : stretching (by PRESSURE ) a wire or a silicone crystal changes its electrical resistance
- connected to a wheatstone
bridge circuit
the voltage output is proportionate to the pressure applied it
!
Slide13The 3 major problems may occur:
1. Improper zeroing and zero drift2. Improper transducer / monitor calibration 3. Inadequate dynamic response of system : a. RF ( resonant or natural frequency) b. damping
RF =
frequency at which a system oscillates when stimulated
- if the frequency of an input signal (
i.e.,
pressure waveform
) approaches the RF of a system : progressive amplification of the output signal occurs,
a phenomenon known as
ringing.
Slide14The ARTERIAL PRESSURE Waveform
ARTERIAL WAVEFORM is a complex sine-wave The fundamental frequency (FF) or the 1-st harmonic is equal to the HR ( ex: for HR 60 b/min = 1 beat / sec = 1 cycle/sec = 1Hz.)physiologic peripheral arterial waveforms have a FF = 3 to 5 Hz ( 180 – 300 beats / min)The MONITORING SYSTEM ( catheter + transducer + lines)
- RF of the monitoring system should be at least at least 5 times higher than the highest frequency in the input signal or better : approx.10 times the FF
at least RF > 20 – 25 Hz to avoid ringing and systolic overshoot
Slide15The ARTERIAL PRESSURE Waveform
,Damping Coefficient (DC): is a measure of how quickly an oscillating system comes to rest Testing DC: the fast-flush test (“square wave” test)
optimal damping
overdamping
= underestimates SAP and overestimates DAP
-
underdamping
= overestimates SAP and underestimates DAP
- in
both cases however,
MAP is relatively accurate !!!
Slide16REDUCING ARTIFACTS IN A-LINES
Lines free of kinks and clots avoid Air Bubbles : small amount may augment systolic pressure reading, while large amount cause an over-damped systemonly one stopcock per lineHeparinized saline flushed maintaining patency
Transducer should be electronically balanced or
re-zeroed
because the zero point may drift if
the room temperature changes
to have an adequate damping =
flushing TEST !
The catheter and lines
:
short and rigid
Slide17MEASUREMENT OF BLOOD FLOW:
CARDIAC OUTPUT
Slide18Potential Methods able to measure the
Cardiac Output Fick method Indicator dilution Pulse waveform (“pulse contour”) methods Ultrasounds ( 2D-Echo and Doppler techique) BioimpedanceANGIOGRAPHYMRI
Slide19Ideal Cardiac Output Monitoring Technique
Precise and No biasNon-invasiveContinous and instantaneousAutomaticOperator independentCheapEasy available in OR the ICULeads to treatment changes / improvement in outcome IT DOES NOT EXIST !
Use the Best Compromise : feasibility – precision – patient !
Slide20The FICK principle
defines flow by: the ratio of the uptake or clearance of a tracer within an organ to the arterio-venous difference in concentration CO = VO2 / ( CaO2 – CvO2)
VO2 is measured by: a
spirometer
+ a Douglas bag
CvO2 is taken from the pulmonary artery
CaO2 is taken from a catheter in a peripheral artery
Slide21The FICK method
considered to be the most accurate method for CO but : - invasive, time consuming - accurate VO2 samples are difficult to acquire discontinous CO : Deltatrac (Datex)
continous CO : possible, but no integrated system available
modified
Fick
equation :
continous
CO by NICO2 apparatus !
Slide22INDICATOR DILUTION
CO measurement by indicator dilution has 3 phases :(a) an indicator is brought into the circulation (injection)(b) the indicator mixes with the bloodstream (mixing and dilution)
(c) the concentration of the indicator is measured
downstream
(detection)
Slide23INDICATOR DILUTION
Chemical indicator dilution (dye)Thermal indicator dilution ( Thermodilution ) the widest used : PAC = Swan-Ganz
Slide24Chemical indicator dilution
The Stewart-Hamilton formula (time-concentration curve) using indocyanine green was the conventional indicator dilution method used to measure CO in ICU until the 1970’s.Indocyanine green : - nontoxic, inert, safe - short half-life
- not affected by arterial saturation
Slide25The Thermodilution
(TD) method Thermodilution = the indicator is the change in blood temperature a known volume of
injectate at low temperature
is injected into the
right atrium
and the cooled blood
traverses
a
thermistor
in a major vessel branch
downstream over a duration of time.
TD Methods :
1.
PULMONARY
Thermodilution
(P-TD) : PAC
2.
TRANSPULMONARY
Thermodiution
(TP-TD)
Slide26The CLINICAL STANDARD
is the PAC !Pulmonary -TD
Slide27PAC-Thermodilution
The change of the blood’s temperature in is measured in the pulmonary artery using the PAC thermistor and then,the monitor electronically displays a temperature/time curve.
The CO is inversely proportional to :
-
the temperature change
- the area under the curve
PAC measures the Pulm.CO = Global CO if no intra-cardiac shunt exists!
Slide28Sources of
error for P-TDLoss of indicator Variation of injectate temperature and volumeRecirculation - IC shunts : false high CO valuesTricuspid regurgitation : false low CO valuesFluctuations in baseline temperature
Slide29...........................
10 ml.cold saline (4 °- 6° C)optimal < 4 sec.> 4-5 sec. false low CO during the same respiratory phase-at least 3 measurements with ∆ less than < 10 % between them !
Slide30Advantages of P-TD
the standard method for clinical CO measurementsimple and repeated measurements possibleThe modified PAC may provide CCOthermal indicator : intermitent heating of a resistance44°C for 1-4 sec, each 30-60 secNot really continuous : mean of 3-4 min ! expensive
The PAC provides not only CO, SV, ..
but also PA pressures, PCWP,
SvO2,
and optionally RVEF
and RVEDV.
but: IT IS INVASIVE!
Slide31TRANSPULMONARY Thermodiution
(TPTD) The TPTD femoral artery curve appears later and has a lower
peak temperature than the
pulmonary artery TD
curve.
The TPTD was shown to be as accurate and precise as P-TD is !
TP-TD is less invasive than P-TD,
but does not offer:
SvO2, PCWP and PAP values
,
TD
TD
Slide32The Clinical USE of TP-TD
Mainly : as a “ calibration method” for other systems : PiCCO, EV-1000PiCCO and EV-1000 are able after the initial calibration by TPTD, to measure in a continuous manner ( beat by beat ) the C.C.O, using the Pulse Contour method !
Slide33CCO by the P
ulse contour methodThe area under the systolic part of the AP waveform correlates : - directly with Left Ventricular STROKE VOLUME - inversely with aortic impedance (Z)SV = Systolic Area / Z
Slide34The Pulse Contour methods
CALIBRATED techniques PiCCO EV-1000 LiDCO – Pulse CO (TP- Lithium dilution)
NON-CALIBRATED techniques
Flow-Track – VIGILEO
Pro-AQT
Nexfin
( Clear-Sight): totally non-invasive
TPTD
C.C.O
.
mini-invasive
Slide35PiCCO & EV-1000are “calibrated” C.C.O.( mean 5 -15 sec.) with intermittent TP-TD calibration. Enables continuous hemodynamic monitoring using: - a femoral / axilary artery catheter
+
- a central venous catheter (CVC)
Slide36LiDCO – Pulse CO
the calibration technique is : Lithium indicator Dilutionsafe and minimally invasive : peripheral venous and arterial cathetersthe PulseCO algorithm used by LiDCO is based on pulse power analysis !Continuous, real-time cardiovascular monitoring
Slide37Pulse Contour NON-CALIBRATED
techniques Flow-Track VIGILEOPulsioFlex- ProAQTLiDCO-rapid - demographics - only an arterial line + a proprietary sensor in line
NEXFIN (Clear-Sight)
- totally non-invasive !
Slide38BIOIMPEDANCEbio tissues (bone,
muscle,blood, etc) have different electric proprietiesblood is the most conductive tissue ( Na+ and Cl-)pulsatile modifications of ITBV → Δ TB Δ TB ~ Δ stroke volume SV = K x (dZ / dt
) / Zo
x TEV
Δ TB is measured by : producing and
transmiting
electricity
( high
υ
= 70 kHz low A = 2,5
mA
) between 2 pairs of electrodes
Slide39Echocardiography (ultrasounds)
for measuring the CO 2 D – methodDoppler - method
Slide40UltrasoundsUS techniques can detect :
the shape, size and movement of tissue interfaces, especially soft tissues and blood (RBC)US are defined by : - amplitude of oscillation (dB) - the wavelength (distance between successive peaks) - frequency (inversely proportional to wavelength) nr. of cycles / secondhuman ear can detect frequencies : 20-20,000 Hz.
US have frequencies > 20,000 cycles /sec ( 20 KHz)
diagnostic US uses frequencies in the range of 1-10
MHz.
!!!!!
Slide412-D
MethodSV = EDV – ESVLV volumes (Simpson’s method): the summation of the volume of stacked cylinders within the LV at end-diastole and end-systole
SV
= 150 ml - 52 ml = 98 ml
Doppler Effect
Doppler effect represented by: V = _ΔF . c _ 2 F0 cos θwhere V = velocity of object
Δ
F = frequency shift
c = speed of sound in medium (body tissue here)
F
0
= frequency of emitted sound
cos
θ
= angle between sound wave and flow (RBC)
cos
90◦ = 0 so the US beam should be parallel to RBC
Maximum angle = 20◦ !
Slide43Doppler Method for CO measurements
Principle SV =Area x VelocityArea of left ventricular outflow tractObtain LVOT dimension in
parasternal long axis view
Simplified
formula
= (2.1cm)
2
* 0.785
D=2.1
cm
SV = 3.46
cm
2
Flow Velocity at LVOT
PW
Doppler at LVOT in apical 5 chamber view
Velocity time integral 25 cm
25
cm
=
87
cm
3
X
Slide44OESOPHAGEAL DOPPLER
Measurement of blood flow velocity in the descending aorta at the tip of the flexible probe 4 MHz continuous or 5 MHz pulsed wave DAF FTc (corrected flow time)PV (peak velocity) MD (minute distance) HR (heart rate)
Slide45n
Methods: ESICM invited 12 experts to form a Task Force to update a previous consensus (Antonelli et al.: Intensive Care Med 33:575–590, 2007) Conclusions This consensus provides 44 statements that can be used at the bedside to diagnose, treat and monitor patients with shock.
Slide46Monitoring - KEY MESSAGES (1) NOT routine for measuring CO 1C
in non-responders to initial therapy
“
CO or SV should be measured”
to evaluate response to fluid or
inotropes
1 C
Serial measurements of
blood LACTATE
1 C
Not only lactate, but ScvO2 and CO2-gap 2 B
the commonly used preload measures (such as CVP, PAOP or
LVEDAi
or GEDV)
alone should not
be used to guide fluid resuscitation 1 B
use: dynamic over static variables
to predict fluid responsiveness
1B
Slide47Hemodynamic Monitoring
ECHO is first !In complex pts. we suggest to use additionally to ECHO: PAC or TPTD to determine type of shock 2 CWe suggest PAC in patients with refractory shock + RV dysfunction. 2 C
We suggest the use of PAC or TPTD with in pts
. severe shock especially in the case of associated ARDS
2 C
We recommend that less invasive devices are used, instead of more invasive devices, only when they have been validated in shock pts. UG-BP
We
do NOT recommend the routine use of
PAC
for patients in shock.
1
A
Slide48THANKS for your attention !
&GOOD LUCK !