Are The Less Invasive Techniques For Monitoring Cardiac Output As Accurate As The Pulmonary Artery Catheter? Dr Andrew Rhodes St George’s Hospital London Haemodynamic monitoring in shock and implications for management

Conflicts of Interest Consultant for Edwards Lifesciences. Perform research on LiDCO, Vigilance and Vigileo haemodynamic monitors. Member of DSMB for Orion pharma.

Grade Process for Diagnostic Technologies. 1.Assess the evidence of accuracy for the diagnostic test. 2.Assess the evidence that using the technology influences outcome. R. Jaeschke

Summary Description of Technology Assessment of Evidence for accuracy of technology. Assessment of evidence that technology can influence outcome. Recommendations.

How accurate is the PAC? 12-15% for triplicate injection of ice saline –Stetz, 1982 Am Rev Respir Dis –Nilsson 2004 Acta Anesth But worse if –Old –Obese –Less injections –Continuous technologies

Arterial Pulse Analysis for the Measurement of Cardiac Output Arterial pulse pressure analysis is a technique of measuring and monitoring stroke volume on a beat to beat basis from the arterial pulse pressure waveform. Advantages Minimally invasive No incremental risk to the patient Beat to beat information

Pulse Pressure Relationship to Stroke Volume The fluctuations of blood pressure around a mean value are caused by the volume of blood forced into the arterial conduit by each systole. The magnitude of the change in pressure – known, as the pulse pressure, is a function of the magnitude of the change in stroke volume One factor, however, that is of particular importance is the compliance of the arterial wall.

The relationship between Pulse Pressure and Stroke Volume is difficult however….. Problems with measurement of Pulse Pressure –Wave reflection less in an aortic waveform than in a radial waveform –Damping – in the measuring apparatus –Morphology. Problems with assessing aortic compliance –Non linear relationship, prevents any simple approach to estimate volume from the pressure change

Compliance Is altered by –Age –Sex –Disease process –Pharmacology –Etc etc.

Pressure Compliance Female Male Change of Arterial Compliance with Sex Langouwouters J Biomechan 1984

Pressure Compliance AGE Change of Arterial Compliance with Age Langouwouters J Biomechan 1984

Most companies have concluded that this non-linear compliance relationship implies that some sort of calibration technique is necessary for accurate determination of stroke volume from arterial pressure traces.

Assessment of Accuracy Calibration –Very little in shocked or haemodynamically unstable patients. –Study quality limited by design Stable patients No gold standard (mostly against PAC) Pulse contour analysis –Mostly in anaesthetic or post surgical patients.

Int Care Med : Comparison of pulmonary artery and arterial thermodilution cardiac output in critically ill patients. Sakka SG, Reinhart K, Meier-Hellmann A. Bias 0.7 L/min Limits of agreement 1.9 to -0.5 L/min 37 patients with sepsis / septic shock (33) or SAH (4)

AuthorValidationMean CO Bias2 x SD of bias % Error KuritaPAC, EMF MasonPAC LintonPAC CorleyPAC Garcia-RodriguezPAC LintonTPTD LintonPAC Validation Studies Of Lithium Dilution Calibration.

Validation Studies of PCO from PiCCO No. PtsPopulationBiasLimits of agreement Weissman11Neurosurgery0.1+/- 1.9 Jansen54Cardiac surgery0.1+/- 1.0 Gratz27Cardiac surgery0.0+/- 1.1 Rodig26Cardiac surgery0.2+/- 2.0 Goedje24ICU0.1+/- 1.4 Zollner19ICU0.3+/- 2.5 Buhre12Cardiac surgery0.0+/- 1.3

Crit Care Med ;52-8. Reliability of a new algorithm for continuous cardiac output determination by pulse contour analysis during hemodynamic instability. Godje O, Hoke K, Goetz A et al. 24 cardiac surgical patients with change in cardiac output >20% during study period. Bias -0.2 L/min Limits of agreement 2.1 to -2.5 L/min

No. PtsPopulationBiasLimits of agreement Hamilton20Cardiac surgery0.1+/- 1.2 Pittman22Cardiac surgery0.1+/- 1.3 Validation Studies of PCO from PulseCO

Evidence that the Use of Pulse Analysis monitoring Improves Outcome. In post surgical patients –Pearse, Crit care 2005 In shocked patients –???

Yes, (level of evidence, C) but it depends…. –Not all monitors are the same. –In stable patients they perform to a clinically acceptable level and have other advantages. Continuous data Less invasive Offer other variables. –In shocked patients the evidence is less clear. Are the pulse analysis techniques as accurate as the PAC for monitoring CO?

No. –But we should recommend more studies evaluating the performance and efficacy of these monitors in shocked patients. Can we recommend this new technology as an alternative to the PAC in shock?