primary frca teaching 2013 03 cardiac output...

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Cardiac output monitoring O. Zuzan

¤  There is a reduction in post-operative complications, use of central venous catheters and in-hospital stay compared with conventional clinical assessment with or without invasive cardiovascular monitoring.

¤  The CardioQ-ODM should be considered for use in patients undergoing major or high-risk surgery or other surgical patients in whom a clinician would consider using invasive cardiovascular monitoring.

http://www.dh.gov.uk/prod_consum_dh/groups/dh_digitalassets/documents/digitalasset/dh_134597.pdf

Innovation, Health and Wealth. DOH, 2011

CQUIN (Commissioning for Quality and Innovation

¤  Intraoperative fluid management is one of the high impact innovations in the NHS

¤  Cardiac output monitoring for certain operations is a CQUIN pre-qualifier from April 2013

¤  Financial incentive to implement cardiac output monitoring in patients undergoing major surgery

•  http://www.institute.nhs.uk/images/documents/wcc/PCT%20portal/CQUIN%20schemes2/2010.11.25%20Exemplars%20FINAL.doc

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http://www.commissioningboard.nhs.uk/wp-content/uploads/2012/12/cquin-guidance.pdf

Benefits to patients

¤  Low risk of cardiac complications Minimally or non-invasive monitoring

¤  Reduced risk of catheter (CVP, arterial, PAC) related infection

¤  Reduced length of hospital stay, patients are ‘fit for discharge’ sooner

¤  Fewer post-operative complications

¤  Reducing emergency admissions into intensive care after surgery

¤  Earlier detection of complications in surgery

¤  Reduced rate of re-admission and re-operation

NHS Technology Adoption Centre. Intraoperative Fluid Management Technologies. February 2013

¤  In total, the 29 trials involved 4805 patients with an overall mortality of 7.6%.

¤ The use of preemptive hemodynamic intervention significantly reduced mortality (pooled odds ratio of 0.48 [0.33–0.78])

¤ and surgical complications (odds ratio 0.43 [0.34–0.53]).

Anesth Analg. 2010 Oct 21.

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Essential topics

¤  Fick’s principle

¤  Swan-Ganz catheter pressure wave forms

¤  Doppler

¤  Stewart-Hamilton and indicator dilution techniques

¤  Arterial wave form analysis

¤  Sources of error and limitations

¤  Parameters: CO, CI, SV, SI, DO2, SvO2, PCWP, SVV, PPV, FTc, SD

• Vasomotor tone (vascular resistance)

• Vasomotor tone and regional distribution

• Venous return • Intravascuar volume • Pump function / valves • Heart rate / rhythm

• O2 saturation • Haemoglobin

Oxygen content

Cardiac output

Blood pressure

Regional blood flow

¤  Near-infrared spectroscopy

¤  Lactate

¤  Mixed-venous SO2

¤  Systemic oxygen delivery

¤  Systemic Oxygen Delivery = Cardiac Output x Arterial Oxygen Content

¤  Cardiac Output = Stroke Volume x Heart Rate

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Why do we need cardiac output monitoring?

¤  Traditional parameters can be misleading

¤  There is no good correlation between traditional parameters and fluid responsiveness

¤  Decisions based on traditional parameter can be wrong and harmful

¤  CO monitoring provides better end-points to guide haemodynamic interventions like intravenous fluid resuscitation, inotropes, vasopressors, vasodilators

¤  CO monitoring helps to avoid complications and poor outcomes due to low cardiac output, low tissue perfusion or fluid overload

Cardiac output monitoring

¤  Pulmonary artery catheter (Fick principle)

¤  Transoesophageal or suprasternal aortic Doppler

¤  Arterial wave form analysis

¤  Indicator dilution techniques (incl. thermodilution)

¤  Combined techniques

¤  Echocardiography (LVOT Doppler)

¤  Impedance cardiography, electrical velocimetry, bioreactance

¤  Gas rebreathing

¤  Electromagnetic flow meter

Fick’s equation

VO2 = Q(CA −CV )

VO2 = oxygen uptake rateQ = cardiac outputCA = arterial oxygen contentCV = venous oxygen content

250ml/min = 5L/min (200ml/L – 150ml/L)

VO2 = Q ⋅CA − Q ⋅CV

Fick method

Limitations

¤  Accurate measurement of O2 uptake required

¤  Only valid in steady state

¤  Invasive, requires pulmonary artery catheter

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Pulmonary artery catheter

Transoesophageal Doppler


¤  Uses piezo-electric crystals to emit and receive ultrasound waves

¤  Detects flow in descending aorta

¤  Uses nomogram (age, height, weight) derived from Swan-Ganz measurements to convert trace into stroke volume


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Measured parameters

¤  Stroke Distance (SD): Distance a column of blood will travel down the aorta with each LV contraction. Area under the velocity-time waveform. Is used to calculate stroke volume.

¤  Mean Acceleration (MA): Average acceleration of blood from start of systole to detected peak velocity (cm/sec2). Corresponds to contractility.

¤  Flow Time corrected (FTc): Systolic flow time (ms) standardized to heart rate of 60 bpm (one cardiac cycle per second). Inversely correlated to systemic vascular resistance. Reference range 330 – 360ms


Stroke Distance

Aortic cross-sectional area

Aortic Cross-Sectional Area x Stroke Distance = Stroke Volume

Doppler effect

Reflected sound wave

Velocity

Doppler equation

fD = ( fr - f0 ) = 2 v f0 cos θc

fD = Doppler shiftf0 = frequency of emitted ultrasoundfr = frequency or received ultrasoundv = velocity of blood flowθ = angle of insonationc = speed of sound in tissue (1540ms-1)

v = c fD

2 f0 cos θ

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Transoesophageal Doppler Transoesophageal Doppler

Sources of error

¤  Probe position

¤  Altered angle of insonation

¤  Change in vascular tone / aortic cross-sectional area

¤  Turbulent flow

¤  Diathermy artefacts (piezo-electric crystals)

Arterial wave form analysis

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Technical problems

¤  Compliance of aorta is non-linear

¤  Wave reflection, proximity of sampling site, vasoconstriction

¤  Over- and under-damping

¤  Aortic outflow during systole


Sources of error

¤  Damped trace

¤  Arrhythmias

¤  Intra-aortic balloon pump

¤  Aortic regurgitation

¤  Variable aortic impedance

Stewart-Hamilton equation

Q = I

CI (t)dt0

∞

∫

Q = cardiac outputI = amount of indicator

CI (t)dt = integral of indicator concentration over time0

∞

∫ CO =LiCl dose x 60AUC(1−PCV )

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The ideal indicator

¤  Stable

¤  Non-toxic

¤  Easily measured

¤  Uniformly distributed in target compartment

¤  Not lost from circulation during first transit

¤  Rapidly dissipates to avoid recirculation

Thermodilution

Q = VI (TB −TI )K

ΔTB (t)dt0

∞

∫

Q = cardiac outputTB = blood temperatureTI = injectate temperatureK = computation constantVI = injectate volume

ΔTB (t)dt0

∞

∫ = integral of temperature change over time

PiCCO system

¤  Combines arterial wave form analysis and transpulmonary thermodilution

¤  Requires CVP line (for injectate) and special thermistor-tipped proximal arterial line to measure the temperature change over time

¤  Allows calculation of extravascular lung water (EVLW), global end-diastolic volume (GEDV) and intrathoracic blood volume (ITBV)

LIDCO Plus system

¤  Combines arterial waveform analysis and indicator dilution (Lithium)

¤  Uses a continuous arterial blood sample over a lithium-sensitive electrode to measure lithium plasma concentration over time

¤  Does not require a CVP line or a special arterial line

¤  Does not require proximal arterial line

¤  Uses pulse power analysis for arterial waveform analysis / continuous CO measurement

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Lithium dilution

Sources of error

¤  Muscle relaxants

¤  Therapeutic dose lithium

¤  Incorrect lithium dose injected

Dilution techniques

Sources of error

¤  Loss of indicator (before or after injection)

¤  Inadequate indicator dose

¤  Inadequate sampling

¤  Haemodynamic fluctuations

Problems for all CO monitors

¤  Aortic cross-clamping

¤  Aortic stenosis/regurgitation

¤  Arterio-venous shunts

¤  Intra-aortic balloon pump

¤  Arrhythmias (e.g atrial fibrillation)

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Dry Wet

•  Hypotension •  Hypoperfusion •  Shock •  Acidosis •  Renal failure •  Surgical site infection •  Sepsis •  Multiple organ failure

•  Oedema •  Respiratory failure •  Pleural effusions •  Pneumonia •  Abdominal

hypertension •  Anastomotic

breakdown •  Sepsis •  Multiple organ failure

Haemodynamic+op-misa-on

Intravascular+volume Cardiac+output Blood+pressure

Low Low+ Low

Fluid Inotrope Vasopressor

How to assess preload and fluid responsiveness

Static ¤  CVP, PCWP ¤  Transoesophageal Doppler

(FTc, SD) ¤  GEDV, ITBV

¤  Echo (end-diastolic diameter/area)

Dynamic ¤  Stroke Volume Variation ¤  Pulse Pressure Variation

¤  Pleth Variability Index (PVI) ¤  IVC collapsibility

(ultrasound)

¤  Passive leg raising ¤  Fluid challenge

Preload

Stro

ke

volu

me

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Fluid challenge• Give 250ml of colloid over 5 minutes to all patients• Record Stroke Volume Index (SVI) immediately pre

and post

SVI increase > 10% after fluid challenge?

DO2I ≥ 600 ml/min/m2?

Dopexamine• Hb must be > 8g/L before starting Dopexamine• Start/increase dopexamine by 0.25 μg/kg/min• Maximum 1μg/kg/min• Check DO2I after 15 minutes• Consider lower target for DO2I (e.g. 500) in patients

with known cardiac disease and in vascular patients

Recheck parameters regularly at least every 60 minutes

SVI decreased ≥10% from last check?Yes

Yes

Repeat fluid challenge immediately

Yes

No

No

Loop 1

Loop 2

No

References

¤  Drummond KE, Murphy E. Minimally invasive cardiac output monitors. CEACCP 2012; 12: 5-10.

¤  Vincent JL, Rhodes A, Perel A, Martin GS, Della Rocca G, Vallet B, et al. Clinical review: Update on hemodynamic monitoring--a consensus of 16. Crit Care. 2011;15(4):229. /

¤  Jhanji S, Dawson J, Pearse RM. Cardiac output monitoring: basic science and clinical application. Anaesthesia 2008; 63: 172-81.

¤  Schober P, Loer SA, Schwarte LA. Perioperative hemodynamic monitoring with transesophageal Doppler technology. Anesthesia and Analgesia 2009; 109: 340-53.

¤  Reuter DA, Huang C, Edrich T, Shernan SK, Eltzschig HK. Cardiac output monitoring using indicator-dilution techniques: basics, limits, and perspectives. Anesthesia and Analgesia 2010; 110: 799-811.

¤  Pellett AA, Kerut EK. The Doppler equation. Echocardiography 2004; 21: 197-8.

¤  Lawrence JP. Physics and instrumentation of ultrasound. Critical Care Medicine 2007; 35: S314-22.

¤  Levick JR. An introduction to cardiovascular physiology, 5th edn. London, Hodder Arnold, 2010.

¤  www.oliverzuzan.net

primary frca teaching 2013 03 cardiac output...

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