Measurement of cardiac output

Sangram Patil

Cardiac output
§ Definition
§ Determinants
§ Ideal device
§ Gold standard- thermo dilution technique of PAC.

Clinical assessment
§ Low organ perfusion
§ CNS
§ Metabolic acidosis
§ R/S
§ GUT
§ CVS
§ CRT

Techniques
§ Fick partial rebreathing method
§ Dye dilution
§ Thermo dilution
§ Arterial pulse contour analysis
§ Combined Li dilution APCA
§ Thoracic impedance
§ Doppler ultrasound technique

Dye dilution
§ Diagram
§ Graph
§ CO= Computer analysis of AUC for concentration-time curve.
§ Indocyanine green
§ Lithium dilution technique.

Thermo dilution
§ Most widely used.
§ Technique
§ Recent advance- Continuous CO measurement.
§ Status

Arterial waveform analysis
§ Pulse contour analysis- PiCCO (aortic).
§ Arterial cannulation- pulse contour analysis.
§ CVP line- transcardiopulmonary thermo dilution CO measurement for calibration.
§ Beat to beat calculation of CO from AUC.
§ Problems-abnormal waveforms, arrhythmias.

Combined Li dilution-APCA
§ Li dilution-calibration.
§ APCA-Beat to beat CO calculation.
§ LiDCO
§ PulseCO
§ SVR, SV, CO.

Fick Partial rebreathing method
§ Fick principle + CO2 elimination--NICO
§ CO2 elimination = V CO2/ CaCO2 - CvCO2
§ V CO2, CaCO2, CvCO2
§ Technique
§ ETT+IPPV, Rebreathing valve cycles through 2 phases- baseline (non RB), second phase (rebreathing), CO2 / flow sensor, ratio of change in CO2 elimination- calculated as CO.

Thoracic electrical bio-impedance
§ Flow from ventricle to aorta changes the electrical impedance.
§ Xiphoid electrode, neck electrode.
§ Not good correlation with thermo dilution.
§ Problems- age, fluid shifts, pulmonary oedema, myocardial ischemia, electrical interference.

Doppler ultrasound
§ Velocity of BF in descending aorta
§ Frequency of reflected US is changed depending on flow velocity in aorta.
§ V= 2.F0 / (C). (Fd). (Cosine incident angle).
§ > 20 degree angle- underestimates V.
§ Sites- suprasternal, trachea, Oesophagus
§ Oesophageal- Doppler transducer, M mode transducer, SV, 70% CO, ETT.

TOE
§ Sophisticated endoscopic probe.
§ Doppler ultrasound technique.
§ CO, V function, Wall motion abnormality, anatomy, valve function.
§ Doppler- velocity across valve. AUC for flow- velocity curve gives VIT ( velocity time integral)
§ 2DECHO- valve cross sectional area, CSA.
§ SV =VTI . CSA
§ CO= SV. HR

Advantages