Haemodynamic monitoring


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Haemodynamic monitoring

  1. 1. Hemodynamic monitoring <ul><li>Tobias Witter </li></ul>This presentation has been adapted to optimise online viewing
  2. 2. Agenda <ul><li>Status quo of our hemodynamic monitoring </li></ul><ul><li>New devices </li></ul><ul><li>How they work </li></ul><ul><li>Outcome data – Do we need it? </li></ul><ul><li>Discussion </li></ul>
  3. 3. A brief – incomplete - history <ul><ul><li>1870 Adolf Fick postulated his principle for CO measurement </li></ul></ul><ul><ul><li>1929 Werner Forssman devised a method to get mixed venous blood from a man </li></ul></ul><ul><ul><li>1930 Otto Klein was the first to draw mixed venous blood and calculate CO </li></ul></ul><ul><ul><li>1967 Thermistor tipped catheter for CO measurement </li></ul></ul><ul><ul><li>1970 Swan and Ganz added ballon </li></ul></ul>
  4. 6. Richard et al
  5. 7. A randomized, controlled trial of the use of Pulmonary Artery Catheters in High-Risk Surgical Patients. Sandham et al (CCCTG) NEJM 2003; 348.
  6. 8. Knowledge? Gnaegi, Crit Care Med 1997
  7. 10. EVLW Wedge
  8. 12. EVLW
  9. 13. <ul><li>Hemodynamic Monitoring - Status quo: </li></ul><ul><ul><ul><li>HR, BP, SaO 2 , clinical findings </li></ul></ul></ul><ul><ul><ul><li>Lactate </li></ul></ul></ul><ul><ul><ul><li>Echo, IVC? </li></ul></ul></ul><ul><ul><ul><li>CVP , ScvO 2 , invasive arterial pressure </li></ul></ul></ul><ul><ul><ul><li>PAC </li></ul></ul></ul>
  10. 15. Current Opinion Crit Care 2003
  11. 16. . Stroke volume Ventricular preload normal heart failing heart preload-dependence preload-independence
  12. 17. R (CVP/BV) = 0.16 ROC (ΔCVP/CO) = 0.56
  13. 18. Cardiac output <ul><li>Ficks principle </li></ul><ul><li>Waveform analysis </li></ul><ul><li>Stroke volume </li></ul><ul><li>Bioimpedance </li></ul><ul><li>Thermodilution </li></ul>
  14. 19. Bioimpedance <ul><ul><li>Current of known amplitude and frequency </li></ul></ul><ul><ul><ul><li>Measures changes in voltage (thoracic resistance) = Impedance Z </li></ul></ul></ul><ul><ul><ul><li>Change of Z is triggered by changes in aortic blood flow </li></ul></ul></ul>
  15. 20. <ul><ul><ul><li>blood flow pulse contour is roughly triangular in time </li></ul></ul></ul><ul><ul><ul><li>SV is proportional to peak flow x VET, therefore proportional to max change of Z x VET </li></ul></ul></ul><ul><ul><ul><li>SV = (L/Z)2x VET x dZo/dtmax, where L is the distance between the electrodes on the body surface </li></ul></ul></ul>
  16. 22. Bioreactance
  17. 23. Bioreactance <ul><li>Phase shift due to blood volume in aorta </li></ul><ul><li>SV can be expressed as: </li></ul><ul><li>SV = C x VET x dΦ/dtmax </li></ul><ul><ul><li>where C is a constant of proportionality. </li></ul></ul>
  18. 26. Bioreactance - Cheetah <ul><li>NICOM and CPB (pig model): </li></ul><ul><ul><li>Good correlation, regardless of acute changes and temperature swings </li></ul></ul>
  19. 27. Limitations <ul><li>Depending on assumption that the area under the flow pulse is proportional to the product of peak flow and VET </li></ul><ul><ul><li>Not always like that (low flow) </li></ul></ul><ul><li>Different type of bypass in animal studies </li></ul><ul><li>Tested against SGC - thermodilution technique may not actually provide an accurate value for comparison </li></ul>
  20. 28. Flowtrac <ul><li>Skewness </li></ul>Kurtosis
  21. 30. Flotrac - Vigileo <ul><li>Pulse contour analysis </li></ul><ul><li>CO=HRxSV </li></ul><ul><li>Flotrac=PR x (σAP x χ) </li></ul><ul><li>χ is dependent on: </li></ul><ul><ul><li>PR, MAP, σAP </li></ul></ul><ul><ul><li>Patient demographics </li></ul></ul><ul><ul><li>Skewness and Kurtosis </li></ul></ul>
  22. 31. Pulse contour - problems <ul><li>Compliance of aorta not constant </li></ul><ul><li>Wave reflection: depending on distance from heart, age </li></ul><ul><li>Damping – good wave form needed – clinically wave forms are often over or underdamped </li></ul><ul><li>Aortic flow in systole (intermittend vs. continous) </li></ul>
  23. 32. Ideal system <ul><li>Independent of arterial location </li></ul><ul><li>Would correct for aortic unlinearity </li></ul><ul><li>Independent on SVR eg reflection </li></ul><ul><li>Not dependent on wave morphology </li></ul><ul><li>Not affected by damping of wave form </li></ul>
  24. 33. LiDCO <ul><li>Principles </li></ul><ul><ul><li>Conservation of mass/power </li></ul></ul><ul><li>Assumption: </li></ul><ul><ul><li>Net power change is the input of mass of blood minus the blood mass lost to periphery </li></ul></ul><ul><ul><li>The relation between net power and net flow is linear, once calibration and correction for compliance has been done </li></ul></ul>
  25. 35. Pulse Pressure <ul><li>Pulse pressure: fluctuation of blood pressure around mean caused by stroke volume </li></ul>
  26. 36. LiDCO – 5 steps <ul><li>1. Pressure signal is transformed into a standardized volume waveform: </li></ul><ul><ul><ul><li>dV/dBP=calibration x 250 x e -kxBP </li></ul></ul></ul><ul><li>2. Autocorrelation derives beat pulse period and beat power factor - which is proportional to the ejected “nominal” stroke volume </li></ul>
  27. 38. LiDCO – 5 steps <ul><li>3. Nominal SV can be scaled against the actual SV with indicator dilution measurement </li></ul><ul><li>4. Calibration factor corrects for arterial tree compliance at any given pressure and corrects for interindividual differences </li></ul><ul><li>5. Calibration factor changes saturation volume </li></ul>
  28. 40. Potential Benefits <ul><li>Analyzes the whole beat – not only systole </li></ul><ul><li>Because the whole beat is analyzed, independent of site and reflection wave </li></ul><ul><li>Autocorrelation is time based – not frequency based. Therefore less dependent on damping as frequency based methods </li></ul><ul><li>System can be calibrated with any form of CO measurement </li></ul>
  29. 41. Limitations <ul><li>The performance of the software may be compromised in the following patient groups: </li></ul><ul><ul><li>Patients with aortic valve regurgitation </li></ul></ul><ul><ul><li>Following aortic reconstruction - a recalibration is required </li></ul></ul><ul><ul><li>Patients being treated with an intra aortic balloon pump </li></ul></ul><ul><ul><li>Patients with highly damped peripheral arterial lines </li></ul></ul><ul><ul><li>Patients with pronounced peripheral arterial vasoconstriction </li></ul></ul><ul><li>Cardiac arrythmias (SPV, PPV% and SVV%) </li></ul>
  30. 42. PiCCO-way it works <ul><li>Transpulmonary thermodilution </li></ul>
  31. 43. PiCCO-way it works
  32. 44. PiCCO-way it works
  33. 45. PiCCO-way it works CO is calculated with the Stewart-Hamilton equation Curve is then transformed into a logarithmic form and with the MTt and DSt are determined
  34. 46. PiCCO-way it works
  35. 47. PiCCO-way it works
  36. 48. SVV and PPV
  37. 49. General
  38. 51. Results…. R=used as Reference method, s=stable conditions, PAC-CC0 PiCCO LiDCO NiCOM Flotrac Squara, 2007 X (R) X R=0.82 (s) Marque, 2009 X (R) X X R=0.77 (s) Ni, R=0.69 (s) Flo Mayer, 2008 X (R) X Rel. Err 24.6% Raval, 2008 X (R) X R=0.78 (s) Squara, 2009 X (R) X R=0.76 McCoy, 2009 X (R) X Good bias, large SD
  39. 54. Results <ul><li>Postoperative Complications </li></ul><ul><ul><li>44% vs 68% (0.003) </li></ul></ul><ul><li>Length of Hospital Stay: </li></ul><ul><ul><li>Mean 17.5 vs 29.5 days (0.001) </li></ul></ul><ul><ul><li>Median 11 vs 14 days (0.001) </li></ul></ul><ul><li>No difference in ICU LOS </li></ul><ul><li>No difference in 28 and 60 day mortality </li></ul>
  40. 55. Goepfert, ICM 2007
  41. 57. PiCCO control hrs of ventilation 12.6 15.4 P=0.002 Time to discharge 25 hrs 33 hrs P=0.03
  42. 60. Correlation - again
  43. 62. Results <ul><li>Neurology: </li></ul><ul><ul><li>Less vasospasm (55% vs 66%; p=0.03) </li></ul></ul><ul><ul><li>Less DIND (32% vs 48%; p=0.03) </li></ul></ul><ul><ul><li>Less vasospasm related infarcts (6% vs 14%,p=0.049) </li></ul></ul><ul><li>Medical complications </li></ul><ul><ul><li>2% vs 12% (p=0.01) </li></ul></ul>
  44. 63. Conclusions <ul><li>CVP is overrated </li></ul><ul><li>PAC not good for routine use </li></ul><ul><li>CO change may be more important than absolute values </li></ul><ul><li>Estimating CO alone will probably not be enough </li></ul><ul><li>Advanced hemodynamic monitoring can reduce complications and shorten ICU/hospital LOS </li></ul>