Haemodynamic data can be acquired in many ways. However we obtain the raw data we still have a big problemWhat do all these figures mean? How can we put it all together to help our patients?Associate Professor Brendan E. Smith.School of Biomedical Science, Charles Sturt University,Specialist in Anaesthesia and Intensive Care, Bathurst Base Hospital, Bathurst, NSW, Australia
Text of Hemodynamics - Putting the puzzle together
1. Haemodynamics- putting the puzzle together. HR SVR Hb SV DO2 CVP CO SpO2 BP Associate Professor Brendan E. Smith. School of Biomedical Science, Charles Sturt University, Specialist in Anaesthesia and Intensive Care, Bathurst Base Hospital, Bathurst, NSW, Australia.
2. Data Acquisition.Haemodynamic data can be acquired in many ways Trans-Thoracic Echocardiography Trans-Oesphageal Echocardiography USCOM Doppler examination Impedence Plethysmography Pulmonary Artery Catheter PiCCO Etc etc. Each has its own benefits and drawbacks, BUT.
3. However we obtain the raw data we still have a big problem What do all these figures mean?How can we put it all together to help our patients?
4. Oxygen Delivery DO2 X Blood Pressure X Hb SpO2 Cardiac Output SVRStroke Volume Heart Rate Preload Inotropy Afterload
5. To live we have to have Blood pressure and blood flow!
26. AfterloadDepends on:Degree of vasoconstriction / dilationDensity & viscosity of bloodFlow rate of blood / surface tension forcesElasticity of arteriesStroke volume
27. These are all the same factorsthat determine mean aortic rootpressureSo afterload is exactly the same as meanaortic root pressure.MAP = diastolic + (systolic diastolic)But can we use radial artery pressure?
28. Integrated PressureP2 PP1 t t P2 Mean Pressure = P1 P.dt = Pressure time integral = Pti time
29. Pti-A Pti-R
30. Pti-Aortic and Pti-Radial are close enough in clinical practice to make no significantdifference to haemodynamic calculations. (error typically 95% of cases this is done by clinical judgment alone! Which inotrope and how much? What are our therapeutic targets? How do we know weve reached them? If only we could measure inotropy!!
37. How Can We Measure Inotropy?
38. Conservation of EnergyThe energy produced by cardiac contraction must be converted to either Potential Energy (PE) in the form of blood pressure or Kinetic Energy (KE) in the form of blood flow. But can we measure PE & KE? Is the measurement reliable? How long does it take? Can we monitor Rx with it?
39. Potential EnergyPE developed by the heart appears in the form of the energy needed to raise the stroke volume up to arterial pressure in a given systolic time, the Flow Time. Work Done = P x V PE = MAP x SV Flow Time P = Mean Arterial Pressure - CVP SV and Flow Time are measured directly using CW Doppler.
40. Potential Energy PE = BPm x SV x 10-3 7.5 x FT 7.5 and 10-3 are required to convert BP in mmHg to kPa and SV in ml to m3 to conform with SI units.The unit for PE is therefore Joules/second, or Watts.
41. Kinetic Energy The KE of any moving mass is given by