What are the recommendations for cardiac output monitoring based on pulse contour analysis?

Cardiac Output Monitoring Based on Pulse Contour Analysis

Cardiac output measurement with pulse contour analysis may be considered in selected patients, but should not be used as a routine monitoring method due to its limited accuracy in situations with hemodynamic instability. 1

Current Recommendations

• Pulse contour analysis for cardiac output monitoring carries a Class IIb recommendation (may be considered) with Level B evidence according to the 2024 EACTS/EACTAIC/EBCP guidelines 1
• This monitoring technique should be reserved for selected cases rather than routine use 1
• Transoesophageal echocardiography (TOE) is recommended (Class I) in cardiac surgery procedures unless contraindicated and should be prioritized over pulse contour analysis 1
• Pulmonary artery catheters (PAC) should be considered (Class IIa) in selected cases to reduce hospital length of stay 1

Limitations of Pulse Contour Analysis

• Agreement between pulse contour analysis monitors and the "practical gold standard" pulmonary artery catheter has been poor, with a mean percentage error of 41% (exceeding the accepted agreement standard of 30%) 1
• Accuracy is particularly compromised during:
  • Hemodynamic instability 1
  • Changes in temperature 1
  • Changes in vascular tone 1, 2
  • Changes in afterload 1
  • Changes in intravascular volume 1
• There are no clinical studies assessing clinical outcomes with the use of minimally invasive hemodynamic monitors using pulse contour analysis 1

Clinical Applications

Cardiac Surgery Setting

• Pulse contour analysis may be useful during weaning from cardiopulmonary bypass, but its accuracy is questionable during this critical period 1
• TOE is recommended as the primary monitoring tool for cardiac surgery, having shown to influence surgical decisions in 7.0% of cases before CPB and 2.2% after CPB 1

Critical Care Setting

• In ARDS patients, continuous thermodilution-based and pulse contour analysis-based cardiac output monitoring are not recommended during ECMO treatment due to frequently inaccurate results 1
• For patients with septic shock, pulse contour analysis has shown variable reliability:
  • Some studies show good correlation with thermodilution methods 2
  • Others demonstrate that pulse contour analysis underestimates cardiac output and is less reliable than transpulmonary thermodilution 3

Technical Considerations

• Pulse contour analysis requires calibration with a reference method (typically thermodilution) for optimal accuracy 4, 5
• Uncalibrated systems may be less reliable in patients with rapidly changing hemodynamics 3
• The reliability of some pulse contour systems may not be significantly affected by vascular tone changes produced by norepinephrine infusion 2
• For accurate stroke volume variation measurement using pulse contour analysis, patients should be mechanically ventilated with tidal volumes of 6-8 ml/kg 6

Practical Implementation

• Use pulse contour analysis only in selected patients where the benefits outweigh the limitations 1
• Consider recalibration after extreme hemodynamic changes such as those occurring in septic shock 4
• Combine with other monitoring techniques (especially echocardiography) for more comprehensive hemodynamic assessment 1
• Be aware that pulse contour analysis may be inaccurate in patients with:
  • Spontaneous breathing efforts 6
  • Cardiac arrhythmias 6
  • Open chest conditions 6
  • Right ventricular dysfunction 6

In conclusion, while pulse contour analysis offers continuous cardiac output monitoring with minimal invasiveness, its accuracy limitations in unstable conditions make it a supplementary rather than primary monitoring tool. Clinicians should prioritize more reliable methods like echocardiography when making critical hemodynamic management decisions.