Predicting fluid response in the ICU

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Predicting fluid response in the ICU

  1. 1. Predicting fluid response in the critically ill Dr. Andrew Ferguson Consultant in Anaesthesia & Intensive Care Medicine Craigavon Area Hospital
  2. 2. Approach to shock <ul><li>Fluid challenge central to therapy </li></ul><ul><li>+/- CVP (and/or PA) monitoring </li></ul><ul><li>Repeat if CVP/PAWP still low </li></ul><ul><li>Stop if CVP/PAWP goes high </li></ul><ul><li>Surrogate markers for CO </li></ul><ul><ul><li>Lactate </li></ul></ul><ul><ul><li>SvO 2 </li></ul></ul>
  3. 4. So what’s the problem? <ul><li>? validity of CVP as end-point </li></ul><ul><li>? validity of PAWP as end-point </li></ul><ul><li>Preload-SV relationship unknown </li></ul><ul><li>Only 50% of patients fluid-responsive </li></ul><ul><li>Excess fluid problems </li></ul><ul><ul><li>Interstitial fluid excess </li></ul></ul><ul><ul><li>Worsened gas exchange </li></ul></ul><ul><ul><li>Limitation of oxygen diffusion </li></ul></ul>
  4. 5. Variability of fluid response rates Michard (Chest 2002; 121: 2000-2008)
  5. 6. Preload does not guarantee response
  6. 7. To be a fluid responder, both ventricles must be on ascending portion of Frank-Starling curve Response depends on contractility and diastolic function as well as load
  7. 8. Common measures used to indicate likelihood of response <ul><li>CVP </li></ul><ul><li>PAWP </li></ul><ul><li>RVEDV (thermodilution) </li></ul><ul><li>LVEDA (echo) </li></ul>
  8. 9. R 2 = 0.2 In spontaneous resp. a fall > 1 mmHg in RAP has positive predictive value of 77-84% and negative predictive value of 81-93% for response
  9. 10. R 2 = 0.33
  10. 12. ROC curve minimal correlation
  11. 14. They don’t work --- what next??
  12. 16. BP change relates to SV change
  13. 17. Cardio-pulmonary interactions Changes in SV, PP, SBP with positive pressure ventilation
  14. 18. Increased pleural pressure RV preload falls LV afterload falls Increased transpulmonary pressure RV afterload increases LV preload increased by alveolar vessel squeeze Decreased RVSV Increased LVSV
  15. 19. Inspiratory decrease in RVSV Expiratory decrease in LVSV Expiratory decrease in LV preload Pulmonary transit time
  16. 20. Stroke volume variation and LVEDP
  17. 23. Potential tools <ul><li>Stroke volume variation </li></ul><ul><li>Systolic pressure variation </li></ul><ul><li>Pulse pressure variation </li></ul><ul><li>Peak aortic blood flow velocity variation </li></ul>
  18. 25. Systolic Pressure Variation  down is the important one for fluid response
  19. 26. Systolic pressure variation
  20. 27.  SP as indicator of fluid response
  21. 28. Pulse pressure variation
  22. 29.  PP as indicator of fluid response
  23. 30. Measures of response to volume
  24. 31. Predictive values Study No. of patients Measure Threshold Positive pred. val. Negative pred. val. Magder 33  RAP (SPONT) 1 mmHg 84 93 Tavernier 35  Down 5 mmHg 95 93 Magder & Lagonidis 29  RAP (SPONT) 1 mmHg 77 81 Michard 40  PP 13% 94 96 Feissel 19  VPeak 12% 91 100
  25. 32. Problems with  PP and  SV <ul><li>Equipment not universal </li></ul><ul><li>Need sinus rhythm </li></ul><ul><li>False positive in severe abdominal distension </li></ul>
  26. 33. Normal values <ul><li> PP 13% </li></ul><ul><li>SPV  down 5% </li></ul><ul><li> Vpeak (aortic blood flow velocity) 12% </li></ul><ul><li> SV 10% </li></ul>
  27. 34. Conclusions <ul><li>Conventional measures often not valid </li></ul><ul><li>New and accurate measures available </li></ul><ul><li>Consider passive leg raising! </li></ul><ul><li>Know cardio-pulmonary interactions </li></ul>

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