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EsophagealDoppler Monitoring

Jennifer Monier, RN Clinical Education

Problem

Optimal fluid management may not be being achieved for all patients

70% of patients will be hypovolemic at the time of incision! Buungaard-Nielson

• Absolute Hypovolemia is a reduction in circulating blood volume• Relative Hypovolemia is caused by vasodilation and the extra space

remaining under filled

Solution:

Individualized Fluid Management

• Has to involve hemodynamic monitoring• What does blood pressure tell you about flow? • Pressure x Flow = CO

Standard fluid amounts: not right for everyone

Tool

CardioQ-EDM+

• Non invasive • Strong evidence base• It improves outcomes

Aims of hemodynamic monitoring

• Achieve optimal cardiac output for that patient in order to prevent tissue hypoxia

• Anticipation of hemodynamic decline to avert hemodynamic crisis• Ensure treatment is appropriate and assess its effectiveness

Fluid Distribution Model

5L

30L

10L

Three “boxes”… Vascular

Interstitial

Intracellular

Filling-in ‘holes’- Daniel Chappell 2008, Crystalloid and Colloid

Right fluid, right amount, at the right time

Colloid

Hartmanns orRingers Lactate

Glucosesolution

Vascular

Interstitial

Intracellular

Vascular System

Red bloodcells

Plasma

A 1L hole is a lot even without bleeding

3L2L

Effect of a 1L “hole”

Vascular system - 33.3%

Interstitial/cellular - 2.5%

Compensation

The human body compensates well for a drop in blood volume by diverting blood away from the gut and splanchnic organs, and by increasing resistance to blood flow.

• This ensures that blood pressure is kept within normal limits until the loss of blood is severe.

• Controlled Hemorrhage, Hamilton – Davies, 1997

Doppler Background

First described by Christian Doppler in 1842

• The frequency of sound emitted by a moving object appears to change according to the velocity of the object relative to the listener.

The Doppler Principal in EDM

EDM uses the Doppler Principal to measure the velocity of blood as it passes through the descending aorta:

The shift in frequency of the reflected ultrasound waves caused by the moving blood cells, are translated by the Cardio Q into a waveform that looks at the velocity of the blood against time

What is Esophageal Doppler Monitoring?

• A virtually non invasive method of assessing cardiac function. No cuts, no lines.

• A probe is inserted into the oesophagus at approx. T5/T6.• By ultrasound, it measures the velocity of blood flow as it passes in

the descending aorta.

Esophageal Doppler Monitoring

The only hemodynamic monitor proven to reduce major complications, total complications and lengths of stay in multiple RCTs

CardioQ-EDM accuracy

• The key parameters are SD, PV, HR, FTc • All are physical time based measurements made by the quartz

crystals contained in the CardioQ-EDM. • The accuracy of measurement of these parameters is dependent on

two factors; the probe position and the accuracy of the quartz crystals.

• The crystals are accurate to ± 0.005%. Time measurements are accurate to ± 6 milliseconds.

• Repeatability on one waveform is better than ± 1% for the measurements of SD, PV, HR, FTc

Flow versus Pressure measurements

Measuring just cardiac output or just pressure is notoriouslyinaccurate

Flow gives a truer picture of cardiac function and circulation• It tells more about volume• Static pressure recordings are often poor determinants of intravascular

volume

Blalock 1943, says:“It is well known by those interested in this subject that the blood volume and cardiac output are usually diminished in traumatic shock before the arterial blood pressure declines significantly” Blalock A, (1943) Surgery 14: 487-508

Equipment Required

• Probe• The CardioQ• Power Supply• Water Based Lubricating Jelly• Gloves

Probe Insertion

- Place probe right after intubation

- Liberal amount of water based lubricant

- Insert orally or nasally to 3rd marker, turning left to right and then

pulling slowly…. repeating until aortic signal is located• Do not use force

Optimizing the Signal

Adjust the probe until you find a signal with• Loudest, sharpest sound• Tallest peaks• Brightest colours along edge with dark centre

The Waveform - SPAG

• CHECK:• Loudest sharpest sound, tallest and brightest peak

• Plus:• Dark centre with no spectral dispersion• Tidy green line enveloping the waveform• 3 white arrows are placed in appropriate places

Ve

loci

ty (

cm/s

) l

Time (ms)

Peak Velocity

Flow Time (FT)

The Nomogram

Converts linear measurements into volumetric. • Enter patient details :

• Age: needed for stroke volume and cardiac output calculations

– accurate age is required

• Weight and Height: In order to index cardiac output, stroke volume and systemic vascular resistance

– estimated weight and height is OK.

Nomogram limits

Adult nomogram limits;• AGE: 16 to 99 years.• WEIGHT: 30 to 150 kg (66 to 330 lbs).• HEIGHT: 149 to 212 cm (59 to 83 in).

The Waveform

Ve

loci

ty (

cm/s

) l

Time (ms)

Peak Velocity

Flow Time (FT)

Parameter Interpretation

Flow Time Corrected (FTc) 330-360ms• Inversely affected by afterload. Is also sensitive to changes in preload.

– Commonest cause of low FTc (<330) is Hypovolemia with compensation (SVR increasing).

• Then consider other causes:• Hypothermia• Vasoconstricting drugs• Pain

– Long FTc (>360) is seen when SVR decreasing such as • Anaesthetic drugs• Vasodilating drugs• sepsis,

Flow Time Corrected

Flow Time is corrected to heart rate of 60, but takes into account the current heart rate so that normal values are always 330 – 360 ms.

If Heart Rate = 60 bpm then each Cardiac Cycle will last for 1 sec or 1000ms

For a Cardiac Cycle of 1 sec, then Systolic Flow should last for 330 ms provided there is adequate preload

Systole Diastole1/3 2/3

1 Cardiac Cycle

Parameter Interpretation

Peak Velocity (PV)• An index of contractility

– Changes with age– Also affected by load

Frank-Starling Curve

End Diastolic Volume

Stroke Volume

> 10%

< 10%

0%

“Within limits, the greater the heart muscle is stretched during filling, the greater the quantity of blood pumped into the receiving vessels.”

Algorithms

Afterload Increase Afterload Reduction

Positive InotropyMyocardial Depression

Preload Reduction Preload Increase Predominant Change

Considerations

• Intra-aortic balloon pumping• Severe coarctation of the aorta• Thoracic aneurysm• Known pharyngo-esophago-gastric pathology• Severe bleeding diatheses• MRI scan• DC cardioversion

Summary of EDM

Achieve optimal descending aortic waveform signal• Clearest sound• Tallest peaks• Spectrum of colours

Interpret the waveform• Look, listen, analyse the data and relate to the clinical picture

• FTc is inversely affected by afterload but is sensitive to changes in preload

• PV is an index of contractility and also affected by load

Summary of EDM

• Less invasive.• No cuts, no lines.

• Safe and accurate• Proven positive outcomes• Less risk of infection• Cost effective• Estimates contractility as well as preload and afterload • Excellent for fluid management.

• Bolus can be given to assess SV response• Useful for titration of inotropes• Can be nurse led in ICU.

• Treatment need not be delayed

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Poor focus. Do not use results until focus is rechecked.

Green envelope is not tidy around waveform.

Poor quality signal

Arrows not placed at triangle points

Gain too high. Valve noises present. Reduce gain. Turn filter on if valve noises cannot be resolved. Filter only for these low frequency noises, not diathermy.

Valve noise

Patient 1.Possible Hypovolemia

Possible Hypovolemia. Reduced FTc, narrow base, low SV, respiratory swing. Try fluid challenge.

Atrial fibrillation. Increase average cycles to between 10 and 20.

Sepsis. Low resistant state. Hyperdynamic circulation. Fill to top of Starling curve and/or vasoconstrict if BP then remains low.

Aortic regurgitation. Normal forward flow in systole followed by reversed flow in diastole

Lady with aortic stenosis and secondary LVF on induction of anaesthesia. PV lower than age range and LVF shows rounding of waveform.

Useful ectopic1. May still be fluid responsive as wave after compensatory pause is Larger due to increased filling time.

Use of inotropes may show very upright waveform.

Cardiopulmonary bypass

Heading

Coeliac axis. Probe usually too low.

Large wide waveform Flow in diastole. Starts high and tapers down

Flow underneath line from other vessels. Artefact above line in diastole. EDM only measuring between white arrows.

Case History

Case History

• Doctor says “I wouldn’t usually use this for this type of patient!”

• 21 year old.• Hysterectomy for terminal Ca• Physically had good appearance.

Case History 5

“OK, so what do I have to do?”

•Probe placed. •Explanations given. •Focus acquisition good. •Surgery begins.

Case History 5

“What do you think Doppler is showing me?…”

BP 120/80

HR 85 • Remember the BP & HR numbers!

SV 50

FTc 350

PV 80

Case History 5

Doppler shows increased afterload possibly due to HypovolemiaFluid challenge given as per algorithm

• SV 60• FTc 360• PV 80• BP 120/80!• HR 85!

No further response to fluid challenges.

Case History 5

10 minutes later• SV suddenly 45• PV 70• FTc 330• BP 120/80!• HR 85!

“What does it mean now?”

Saw that surgeon was removing packs from abdomen and these were covered in clots. Doppler showed reduced flow probably due to covert bleeding. Checkout BP & HR though!

• Good Doppler response to fluid challenges

Case History 5

Rest of surgery• BP 120/80!• HR85!

• SV only ever maintained at 60 despite possible vasodilation from anaesthetic agents and drugs. Would have expected it higher.

Case History 5

End of surgery• BP 120/80!• HR 85!• Hb at end of surgery was 6 (preop was 10)• Patient had blood transfusion

“This patient may have gone back to ward and coped for 24 hours or so but then deteriorated suddenly, had Doppler not been used”

• Doppler helped to give colloid and blood when needed

Case 5

What does that mean?• Doppler was showing reduced flow due to covert bleeding• Despite good responses to fluid challenges, unable to keep up with

losses and so SV probably never really increased to Starling curve limit• BP and HR did not indicate a problem because young fit adult using

compensation mechanisms

Case 5

Doppler use;• Age doesn’t matter• ASA doesn't matter• Not just for 1 or 2 surgery types

– Use it on all moderate and major surgery to give the fluid when they need it despite normal (?) pressure readings

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