Haemodynamic monitoring

Cardiac output monitoring

Reviewed Nov 2026·1 references
New· views rounded down, updated weekly

Choosing between echo, pulse contour, transpulmonary thermodilution and pulmonary artery catheter, and what each number means.

Definition
Cardiac output (CO) = HR x stroke volume; cardiac index = CO/BSA (normal 2.5-4.0 L/min/m²). Advanced monitoring is indicated in shock not responding to initial therapy, complex mixed shock, or RV failure/ARDS where fluid balance is critical.

At the bedside

  1. 1

    Start with echo

    ESICM 2014 recommends echocardiography as the first-line tool to assess type of shock. LVOT VTI x LVOT area x HR estimates CO; normal VTI 18-22 cm.

  2. 2

    Choose advanced monitoring if not responding

    Transpulmonary thermodilution (e.g. PiCCO, EV1000/VolumeView) or pulmonary artery catheter in severe shock, especially with ARDS or RV dysfunction.

  3. 3

    Pulse contour analysis

    Uncalibrated (FloTrac, LiDCO rapid, ProAQT) or calibrated (PiCCO). Good for trends and SVV; inaccurate with arrhythmia, aortic regurgitation, IABP, rapid vasopressor changes and damped traces.

  4. 4

    Transpulmonary thermodilution

    Cold saline (15-20 mL) via CVC, femoral arterial thermistor: CO, GEDVI (preload, normal 680-800 mL/m²), EVLWI (lung water, > 10 mL/kg = pulmonary oedema), PVPI (> 3 = permeability oedema).

  5. 5

    Pulmonary artery catheter

    CO (thermodilution), PAOP (wedge, LV filling), PAP, SvO2, PVR. Use in complex RV failure, pulmonary hypertension, cardiogenic shock and cardiac surgery; no routine benefit in general ICU patients.

  6. 6

    Integrate, don't chase numbers

    Use CO with MAP, perfusion markers (lactate, CRT, ScvO2, CO2 gap) and organ function to choose fluid vs vasopressor vs inotrope.

Cardiac output tools compared

ToolInvasivenessKey outputsLimitations
EchocardiographyNoneLV/RV function, VTI, CO, pericardium, valvesOperator dependent, intermittent
Uncalibrated pulse contourArterial lineCO trend, SVVArrhythmia, AR, vasoplegia, damping
Transpulmonary thermodilutionCVC + femoral arterial lineCO, GEDVI, EVLWI, PVPI, SVVRecalibrate every 8 h / after changes; cost
Pulmonary artery catheterPA catheterCO, PAOP, PAP, SvO2, PVRComplications (arrhythmia, PA rupture), interpretation errors
Bioreactance / oesophageal DopplerNon-/minimally invasiveCO trendValidation varies
Red flag · call your senior now
Cardiac index < 2.2 L/min/m² with hypoperfusion = low-output shock: inotrope/mechanical support evaluation.
Pitfall
Trusting uncalibrated pulse-contour CO in severe vasoplegia, AF or after large vasopressor changes.
Pitfall
Measuring PAOP at peak inspiration instead of end-expiration.
Pearl
EVLWI from thermodilution helps stop fluids in ARDS: values > 15 mL/kg mean severe pulmonary oedema.

Calculators for this topic

Body surface area (Mosteller)

√(height cm × weight kg ÷ 3600).

Mean arterial pressure

(SBP + 2 × DBP) ÷ 3 (estimate; use the arterial line value when available).

References

  1. 1

    Cecconi M, De Backer D, Antonelli M, et al. Consensus on circulatory shock and hemodynamic monitoring. Task force of the European Society of Intensive Care Medicine. Intensive Care Med 2014;40:1795-815.

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