Pierre SQUARA, MD Clinique Ambroise Paré, Neuilly Should we (can we) measure and optimize VO 2 in shock

I.Fundamentals of hemodynamics

Delivery Consumption Needed consumption

I.Fundamentals of hemodynamics Delivery Consumption deathlife Critical delivery Needed consumption

I.Fundamentals of hemodynamics VO 2 DO 2 Needed VO 2 Critical DO 2 Delivery Consumption depend.Supply independency Critical delivery Needed consumption Lactate

Gnu uptake (/needs) Gnu delivery Gnu extraction Gnu density in Gnu density out Gnu transit time VO 2 (/needs) D a O 2 E O 2 S a O 2 S v O 2 CO Rangers Doctors (SRLF 2001) I.Fundamentals of hemodynamics 100% 0% 5% 35% 15% 95% 50% 85% Limitations in VO 2 use are not theoretical but practical then, must be reassessed periodically

A whole body VO 2 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 VO 2 and the needed VO 2 I.Fundamentals of hemodynamics Gattinoni L et al, In: Pinsky & Payen ed. Functional hemodynamic monitoring. Springer p

II. Should we assess VO 2 ? Key variable VO 2 = plateau Derived variables Decreasing lactate CO =« good » SvO 2 =« good » Derived of derived variables Acceptable blood pressure Clinical improvement Prognostic value (AUC) (0.69) 0.55 (0,68) 0.66 Squara et al J Crit Care, 1994 VO 2 = CO x 1.34 x Hb x (SaO 2 – SvO 2 )

Key variable VO 2 = plateau Derived variables Decreasing lactate CO SvO 2 Derived of derived variables Acceptable blood pressure Clinical improvement Physiologic interest Monitoring interest II. Should we assess VO 2 ?

Normal CO =2.3 – 3.2 L/min.m 2 according to age Increased CO Hypermetabolism Anemia Hypoxemia Impaired O 2 tissue diffusion, utilization Decreased CO Hypometabolism, general anesthesia Hypovolemia, hypertension Impaired pump function Normal SvO 2 = 68 – 74% Increased SvO 2 > 75% Hypometabolism, general anesthesia Hyperdynamic shunts Mitochondrial blockade Decreased SvO 2 < 68% Hypermetabolism Anemia Hypoxemia Low cardiac output, II. Should we assess VO 2 ? Is a specific value of CO or SvO 2 normal adaptative or pathologic ?

0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 CO in L/min/m Min. SvO 2 0,3 0,4 0,5 0,6 0,7 VO PEP 15 PEP 10 PEP 5 PEP 0 II. Should we assess VO 2 ?

SvO 2 CO If Stable Hb Stable SaO 2 Septic shock Cardiogenic shock Basal value VO 2 Dysoxia No proof that CO or SvO 2 values are adequate to needs VO 2 = plateau unique quantitative target II. Should we assess VO 2 ? Ca-vO 2

DO 2 VO 2 True values +10% CO or SvO 2 CO = -0.5 L/min Effects of systematic errors (Squara et al ICM, 2004) III. Can we assess VO 2 ?

20% variability in CO 10% variability in CaO 2 10% variability in SvO 2 Effects of random errors (Squara et al ICM, 2004) DO 2 VO 2 III. Can we assess VO 2 ?

Additional supply dependency Increased metabolic needs Conformance Non oxidative uptake DO 2 VO 2 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 DO 2 point is marginally affected III. Can we assess VO 2 ?

VO 2 using gas VO 2 using PAC 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 O 2 supply dependency And new devices (CCO) allow decreasing the random errors, therefore the global upsloping is usually <10% III. Can we assess VO 2 ?

VO 2 DO 2 SvO 2 Optimal EO 2 =  Optimal EO 2 = 30% Optimal EO 2 = 40% IV. Is there an alternative?

DO 2 VO 2 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) Adequate DO 2 Too low DO 2 Too high DO 2 VO 2 plateau determination V. Tools The crit DO 2 (needed VO 2 ) can be identified In % of cases using 5 points

Always consider: « Matching the VO 2 and needed VO 2 » VO 2 matches O 2 needs when: 1. Clinical status improves 2. Lactate decreases 3. CO and SvO 2 are in empirically expected ranges according to estimated needs 4. VO 2 reaches a plateau Conclusion

My own guideline VO 2 = plateau unique quantitative target OK, If lactate decreases, blood pressure increases and clinical status improves CO and SvO 2 inside acceptable ranges but empirical objectives Simple Ressusitated but unstable Persisting shock