Should we (can we)
measure and optimize
VO2 in shock
Pierre SQUARA, MD
Clinique Ambroise Paré, Neuilly
I.Fundamentals of hemodynamics
Consumption
Needed
consumption
Delivery
I.Fundamentals of hemodynamics
Consumption
Needed
consumption
death
life
Critical delivery
Delivery
I.Fundamentals of hemodynamics
Consumption
VO2
depend.
Needed
VO
consumption
2
Supply independency
Lactate
Critical DO
delivery
2
DO2
Delivery
I.Fundamentals of hemodynamics
Rangers
Gnu
Gnu
Gnu
Gnu
Gnu
Gnu
Doctors
(SRLF 2001)
uptake (/needs) 100% VO2 (/needs)
delivery
0% DaO2
Limitations in VO2 use
are
extraction
0% EO2
not theoretical
S
O
density
in
0%
a
2
but practical then, must be
density
out
0% SvO2
reassessed
periodically
transit time
0% CO
5%
35%
15%
95%
50%
85%
I.Fundamentals of hemodynamics
A whole body VO2 equal to needs is not
a garantee that circulation is adequate
for each cell
But it is a Always
pre-requisite
Macro
consider!the
balance
circulationbetween
must be
thestabilized
VO2 and before
looking at the
theneeded
microVO
circulation.
2
Gattinoni L et al, In: Pinsky & Payen ed.
Functional hemodynamic monitoring.
Springer 2005. p. 70-86.
II. Should we assess VO2?
Key variable
VO2 = plateau
Prognostic value (AUC)
0.72
VO2 = CO x 1.34 x Hb x (SaO2 – SvO2)
Derived variables
Decreasing lactate
CO =« good »
SvO2 =« good »
0.70
0.54 (0.69)
0.55 (0,68)
Derived of derived variables
Acceptable blood pressure
Clinical improvement
0.66
0.66
Squara et al J Crit Care, 1994
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
II. Should we assess VO2?
Normal
74%
Normal SvO
CO =2.3
––
3.2
L/min.m2 according to age
2 = 68
Increased
SvO2 > 75%
Increased CO

 Hypometabolism,
Hypermetabolism general anesthesia
Is a specific
value of

Hyperdynamic
shunts
 Anemia
CO or SvO2 normal

blockade
 Mitochondrial
Hypoxemia
adaptative
Decreased
 Impaired
O2 tissue
diffusion,
utilization
2 < 68%
or SvO
pathologic
?
 Hypermetabolism
Decreased
CO

 Anemia
Hypometabolism, general anesthesia

 Hypoxemia
Hypovolemia, hypertension

cardiac
output,
 Low
Impaired
pump
function
II. Should we assess VO2?
SvO2 VO2
CO in L/min/m2
3,5
0,7
233
3,0
0,6
200
2,5
0,5
166
2,0
0,4
133
1,5
0,3
100
PEP 0
PEP 5
1,0
PEP 10
PEP 15
0,5
0,0
0
10
20
30
Min.
II. Should we assess VO2?
CO
150
4
200
VO2
100
Dysoxia
Septic shock
No proof that CO or
SvO2 values
adequate to needs
Basalare
value
3
VO2 = plateau unique
quantitative target
2
50
Cardiogenic shock
0.82
3
0.76
4
0.7
5
If
Stable Hb
Stable SaO2
SvO
Ca-vO
2 2
III. Can we assess VO2 ?
Effects of systematic errors
VO2
(Squara et al ICM, 2004)
+10% CO
True
or
SvO2
values
CO = -0.5 L/min
DO2
III. Can we assess VO2 ?
Effects of random errors
(Squara et al ICM, 2004)
VO2
10% variability in CaO2
20% variability in CO
10% variability in SvO2
DO2
III. Can we assess VO2 ?
Additional
In
any casesupply
thesedependency
additional needs are part of
Increased
the needs •and must
be : metabolic needs
•
Conformance
Limited
VO2
Non oxidative
uptake
•
Balanced
by appropriate
supply
The ability to identify the critical DO2
point is marginally affected
DO2
III. Can we assess VO2 ?
And
On the
But
the
new
same
global
devices
unshocked
plateau
(CCO)
upsloping
allow
patients,
decreasing
isit has
the
been
usually
random
observed
easyerrors,
to different
distinguish
therefore
curves
from
the O
global
2
(Phang, AJRCCM 1994, Mira, Chest 1994, Hanique, ICM 1993)
upsloping
supply dependency
is usually <10%
VO2 using gas
VO2 using PAC
IV. Is there an alternative?
VO2
Optimal EO2 = 40%
30%

SvO2
DO2
V. Tools
VO2 plateau determination
Method 2
1:
VO2
www.hemodyn.com
Combined
analysis
of lactate
Sum of 2 sums
of squared
residuals
John-Alder et al. (Gilbert
Am J Physiol
1981
variation
et al,
ARRD, 1986)
The crit DO2 (needed VO2)
can be identified
In 75-100% of cases
using 5 points
Too low
DO2
Adequate
DO2
Too high
DO2
DO2
Conclusion
Always consider:
« Matching the VO2 and needed VO2 »
VO2 matches O2 needs when:
1.
Clinical status improves
2.
Lactate decreases
3.
CO and SvO2 are in empirically expected
ranges according to estimated needs
4.
VO2 reaches a plateau
My own guideline
VO2 = plateau unique
quantitative target
CO and SvO2 inside
acceptable ranges
but empirical objectives
OK, If lactate decreases, blood
pressure increases and
clinical status improves
Persisting
shock
Ressusitated
but unstable
Simple