What is the future of haemodynamic monitoring?

Steven M. Hollenberg, MD

Professor of Medicine

Robert Wood Johnson Medical School/UMDNJ

Director, Coronary Care Unit

Cooper University Hospital, Camden NJ

“Prediction is very difficult, especially about the future.”

Yogi Berra

Niels Bohr

“The only way to predict the future is to invent it.”

Alan Kay

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The future of hemodynamic monitoring

• New technologies

• New hemodynamic parameters

• New methods of analysis

• Methods of evaluation

New technologies

• Implantable monitors

New technologies

• Miniaturization– Imagers

• X-ray• MRI• Ultrasound

– Sensors, effectors, and transmitters• Surgical instruments• Analyzers• Optical sensors

New technologies

• Noninvasive methods of evaluation– Echocardiography

• Myocardial contrast: visualization, perfusion• Tissue Doppler• Strain rate imaging• Hand-held devices

– Bioimpedance– Magnetic resonance imaging

New hemodynamic parameters

• Microcirculatory flow and density

• Cardiac power

Cooper MARS Mission

To study the alterations of the sublingual microcirculatory network in humans with severe sepsis undergoing early goal-directed resuscitation

To determine if microcirculatory flow velocity and perfused vessel density correlate with conventional hemodynamic parameters in patients with severe sepsis

Microcirculatory flow in Sepsis

Cardiac Power

Cardiac Power Output [(Mean Arterial Pressure*Cardiac Output)/451]

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Cardiac Power Output [watt] = Mean Arterial Pressure x Cardiac Output / 451

Cardiac Power Output [watt] = Mean Arterial Pressure x Cardiac Output / 451

Fincke R, et al. J Am Coll Cardiol 2006; 44:340

New methods of analysis

• Reductionist approach– Take things apart– Simple rules will yield simple results

• Output is proportional to input

– Engineering paradigms for hemodynamics• Heart as a pump• Electrical analogy with impedance as resistance

Hemodynamic waveforms

• Time series measurements– Smooth, large-scale continuous signal– Discontinuous, small-scale, erratic disruptions

(noise)– Filter out the noise– Describe the average state toward which

homeostatic mechanisms are heading

Biology is a complex system• Body is complex, open and dynamic• System: a group of independent but interconnected

elements that function together to comprise a unified whole.

• “Emergent” properties: properties of the system as a whole that cannot be predicted from individual components

• Fluctuations around the average are not just “noise,” but convey information

• Healthy variability: nonstationary, nonlinear, and multiscaled

• Disease is characterized not by loss of regularity but by loss of complexity

Nonlinear analysis

• Can in theory be automated by computer• Changes in frequency spectrum

components of variability• Breakdowns of fractal scaling with disease• Challenges

– Some of the measures are nonintuitive– Volume of data to be captured is daunting– Artifacts are a real problem– Paucity of therapeutic interventions directed

at nonlinear measures

Evaluation of new technologies

• Monitoring tools would not be expected to improve outcome unless tied to an effective therapeutic strategy prompted by data they provide

• Hemodynamic measures are not used in isolation but in clinical context– Thus, a single hemodynamic variable taken

alone is rarely a good predictor of the response to an intervention

• Implications for trial design

New evaluation paradigms

• Polar ideas that no approach can be adopted without a pivotal RCT and that since no approach can be rigorously tested that theory is enough are equally constricting

• Consensus conferences– Uniform definitions– Uniform processes of evaluation– Managing differences of opinion

Evaluating existing evidence and planning new trials

• Surrogate endpoints– Skepticism is appropriate, but there may be

no alternative• Tradeoff between power and feasibility

– How should surrogates be developed and validated?

• Translation of measures of proven efficacy in clinical trials into effective strategies when applied broadly

The way forward

• We make our own future

• We need active engagement with the evaluation and implementation of new concepts and technologies– New hemodynamic parameters– New ways of measurement– New methods of analysis