Hemodynamics In The Icu

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Hemodynamics In The Icu

  1. 1. Hemodynamics Dalhousie Critical Care Lecture Series
  2. 2. Objectives <ul><ul><li>Discuss the basic cardiac physiology that is routinely used in the management of critically ill patients </li></ul></ul><ul><ul><ul><li>Determinants of MAP </li></ul></ul></ul><ul><ul><ul><li>Determinants of CO </li></ul></ul></ul><ul><ul><ul><li>Determinants of DO 2 </li></ul></ul></ul><ul><ul><li>Be able to describe the various states of shock using the above concepts. </li></ul></ul><ul><ul><li>Describe how and why we monitor CVP </li></ul></ul>
  3. 3. Equations to Live By <ul><li>MAP = CO x SVR </li></ul><ul><li>CO = SV x HR </li></ul><ul><li>Therefore: </li></ul><ul><li>MAP = SV x HR x SVR </li></ul>
  4. 4. Determinants of SV
  5. 5. The Need for Preload
  6. 6. Preload Estimates with error JVP CVP RAP RVEDP PAD PAWP LVEDP LVEDV
  7. 7. Right Atrial Waveform
  8. 8. Looking Carefully at the JVP/CVP
  9. 9. The Role of Afterload
  10. 10. Afterload paradigm <ul><li>If CO increases with decreased afterload then wouldn’t the body work better with a very low afterload? </li></ul><ul><li>What pathologic condition is this called? </li></ul><ul><li>Video </li></ul>
  11. 11. In the end why do we need CO? <ul><li>It’s all about oxygen delivery to the tissues </li></ul><ul><li>DO 2 is delivery </li></ul><ul><li>VO 2 is consumption </li></ul><ul><li>CaO 2 is arterial oxygen content </li></ul><ul><li>CvO 2 is venous arterial content </li></ul><ul><li>DO 2 = CO x CaO 2 </li></ul><ul><li>VO 2 = CO x (CaO 2 – CVO 2 ) </li></ul>
  12. 12. What happens when VO 2 > DO 2 ?
  13. 15. All of Cardiac Physiology in a Nut Shell
  14. 16. It’s Really All About the SvO 2 <ul><li>Generally believed that it’s better to have a normal SVO 2 than a lower one. </li></ul><ul><li>Early normalization of SVO 2 as a goal of therapy is desired </li></ul><ul><li>The unknown: </li></ul><ul><ul><li>low SVO 2 after the initial resuscitation </li></ul></ul><ul><ul><li>what number to treat and what to treat to </li></ul></ul><ul><ul><li>conditions other than obvious shock </li></ul></ul>
  15. 17. What number to treat and what is “The Magic Number”? <ul><li>The SVcO 2 of 70% is based on normal physiology </li></ul><ul><li>“ Over treating” may result in increased mortality through a variety of mechanisms </li></ul><ul><ul><li>Increased VO 2 </li></ul></ul><ul><ul><li>Oxidative injury </li></ul></ul><ul><li>It is suggested that the ideal number is patient dependent and that we should be titrating to the inflection point on the curve rather than an absolute number </li></ul>
  16. 18. The Magic Number <ul><li>488 post operative CABG patients retrospective analysis to determine the prognostic cutoff number for SVO 2 as it pertains to mortality </li></ul><ul><li>SVO 2 < 55% at admission was the cutoff for significant mortality difference </li></ul><ul><li>As low SVO 2 was aggressively treated the question of whether it was the number or the treatment that caused the increased mortality </li></ul>
  17. 20. The Magic Number <ul><li>Retrospective cohort study of 111 critically ill patients with septic shock </li></ul><ul><li>Time spent below SVO 2 of 70% was an independent predictor of mortality along with lactate, MAP and CVP </li></ul><ul><li>Supporting validation of Rivers septic shock algorithm </li></ul>
  18. 21. Using the Swan-Ganz catheter to diagnose type of shock
  19. 22. Using the Swan-Ganz catheter to diagnose type of shock O 2 extraction + SVR Septic shock O 2 extraction + SVR Cardiogenic shock O 2 extraction + SVR Hypovolemic shock RVEDV PAP /N PAWP V V Right ventricular failure PAD/PAWP equalised Cardiac tamponade giant ‘v’ waves on PAWP trace Acute mitral regurgitation O 2 step up noted in SvO 2 giant ‘v’ waves on PAWP trace Acute venticular septal defect Pulm Vasc Res PAD>PAWP by >5 mmHg Massive pulmonary embolism PAWP > 25mmHg N/ Cardiogenic pulmonary edema Left ventricular failure Notes PAP/PAWP CVP/RAP CO/CI MAP HR Condition
  20. 23. Summary <ul><li>We use basic cardiac physiology in the ICU to: </li></ul><ul><ul><li>Diagnose various states of shock </li></ul></ul><ul><ul><li>Optimize tissue perfusion </li></ul></ul><ul><ul><li>We will next talk about various drugs that can be used to manipulate the parameters set out in these equations </li></ul></ul>

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