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Pierre SQUARA, MD Clinique Ambroise Paré, Neuilly

Should we (can we) measure and optimize VO 2 in shock. Pierre SQUARA, MD Clinique Ambroise Paré, Neuilly. I.Fundamentals of hemodynamics. Consumption. Needed consumption. Delivery. death. life. I.Fundamentals of hemodynamics. Consumption. Needed consumption. Critical delivery.

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Pierre SQUARA, MD Clinique Ambroise Paré, Neuilly

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  1. Should we (can we) measure and optimize VO2 in shock Pierre SQUARA, MD Clinique Ambroise Paré, Neuilly

  2. I.Fundamentalsof hemodynamics

  3. Consumption Needed consumption Delivery

  4. death life I.Fundamentalsofhemodynamics Consumption Needed consumption Critical delivery Delivery

  5. I.Fundamentalsofhemodynamics Consumption VO2 depend. Supply independency Needed VO2 Needed consumption Lactate DO2 Critical DO2 Critical delivery Delivery

  6. I.Fundamentalsofhemodynamics Rangers Doctors (SRLF 2001) Limitations in VO2 use are nottheoretical but practical then, must be reassessed periodically Gnu uptake (/needs) Gnu delivery Gnu extraction Gnu density in Gnu density out Gnu transit time VO2(/needs) DaO2 EO2 SaO2 SvO2 CO 100% 0% 0% 0% 0% 0% 5% 35% 15% 95% 50% 85%

  7. I.Fundamentalsof hemodynamics A whole body VO2 equal to needs is not a garantee that circulation is adequate for each cell But it is a pre-requisite ! Macro circulation must be stabilized before looking at the micro circulation. Always consider the balance between the VO2 and the needed VO2 Gattinoni L et al, In: Pinsky & Payen ed. Functional hemodynamic monitoring. Springer 2005. p. 70-86.

  8. II. Should we assess VO2? Key variable VO2 = plateau Prognostic value (AUC) 0.72 0.70 0.54 (0.69) 0.55 (0,68) 0.66 0.66 Squara et al J Crit Care, 1994 VO2 = CO x 1.34 x Hb x (SaO2 – SvO2) Derived variables Decreasing lactate CO =« good » SvO2 =« good » Derived of derived variables Acceptable blood pressure Clinical improvement

  9. II. Should we assess VO2? Key variable VO2 = plateau Physiologic interest Derived variables Decreasing lactate CO SvO2 Derived of derived variables Acceptable blood pressure Clinical improvement Monitoring interest

  10. II. Should we assess VO2? • Normal SvO2 = 68 – 74% • Increased SvO2 > 75% • Hypometabolism, general anesthesia • Hyperdynamic shunts • Mitochondrial blockade • Decreased SvO2 < 68% • Hypermetabolism • Anemia • Hypoxemia • Low cardiac output, • Normal CO =2.3 – 3.2 L/min.m2according to age • Increased CO • Hypermetabolism • Anemia • Hypoxemia • Impaired O2 tissue diffusion, utilization • Decreased CO • Hypometabolism, general anesthesia • Hypovolemia, hypertension • Impaired pump function Is a specific value of CO or SvO2 normal adaptative or pathologic ?

  11. SvO2 VO2 0,7 233 0,6 200 0,5 166 0,4 133 0,3 100 II. Should we assess VO2? CO in L/min/m2 3,5 3,0 2,5 2,0 1,5 PEP 0 PEP 5 1,0 PEP 10 PEP 15 0,5 0,0 0 10 20 30 Min.

  12. Ca-vO2 SvO2 0.82 3 4 0.76 5 0.7 II. Should we assess VO2? CO VO2 1 5 0 2 0 0 No proof that CO or SvO2 values are adequate to needs VO2 = plateau unique quantitative target Septic shock 4 1 0 0 Dysoxia 3 Basal value Cardiogenicshock If Stable Hb Stable SaO2 2 5 0

  13. III. Can we assess VO2 ? +10% CO or SvO2 VO2 CO = -0.5 L/min DO2 Effects of systematicerrors(Squara et al ICM, 2004) Truevalues

  14. III. Can we assess VO2 ? VO2 DO2 Effects of randomerrors(Squara et al ICM, 2004) 10% variability in CaO2 20% variability in CO 10% variability in SvO2

  15. III. Can we assess VO2 ? VO2 DO2 • Additional supply dependency • Increased metabolic needs • Conformance • Non oxidative uptake • In any case these additional needs are part of the needs and must be : • Limited • Balanced by appropriate supply The ability to identify the critical DO2 point is marginally affected

  16. III. Can we assess VO2 ? VO2 using PAC VO2using gas And new devices (CCO) allow decreasing the random errors, therefore the global upsloping is usually <10% On the same unshocked patients, it has been observed different curves (Phang, AJRCCM 1994, Mira, Chest 1994, Hanique, ICM 1993) But the global plateau upsloping is usually easy to distinguish from O2 supply dependency

  17. IV. Is there an alternative? Optimal EO2 =  Optimal EO2 = 40% Optimal EO2 = 30% VO2 SvO2 DO2

  18. VO2 Too high DO2 Adequate DO2 Too low DO2 DO2 V. Tools VO2 plateau determination www.hemodyn.com Method 1 : Sum of 2 sums of squared residuals John-Alder et al. Am J Physiol 1981 Method 2 : Combined analysis of lactate variation (Gilbert et al, ARRD, 1986) The crit DO2 (needed VO2) can be identified In 75-100% of cases using 5 points

  19. Conclusion • Always consider: « Matching the VO2 and needed VO2 » • VO2 matches O2 needs when: • Clinical status improves • Lactate decreases • CO and SvO2 are in empirically expected ranges according to estimated needs • VO2 reaches a plateau

  20. My own guideline VO2 = plateauunique quantitative target Persisting shock CO and SvO2 inside acceptable ranges but empirical objectives Ressusitated but unstable OK, If lactate decreases, blood pressure increases and clinical status improves Simple

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