SaO2 x Hb + (0.0036xPaO2) [SaO2 x Hb + (0.0036xPaO2)]

Practical issues
in ScvO2
monitoring
Prof. Jan Bakker MD PhD
Chair dept of Intensive Care
jan.bakker@erasmusmc.nl
1

Supply-Demand
2

TO 2 = Hb x SaO 2 x CO x ζ
OXYGEN DEMAND OXYGEN SUPPLY
3

Oxygen Extraction Ratio
100 ml O2
50 ml O2
consumption is
25 ml O2
consumption is
25 ml O2
75 ml O2
O2ER = 25%
25 ml O2
O2ER = 50%
4

Oxygen extraction
Decreased DO2
O2ER %
5

ScvO2 - SvO2 monitoring
6

Extraction and Mixed
venous oxygenation
O2ER = CaO2 - CvO2
O2ER =
CaO2
[SaO2 x Hb + (0.0036xPaO2)] - [SvO2 x Hb + (0.0036 x PvO2)]
O2ER ≈ 1 - SvO2
SaO2 x Hb + (0.0036xPaO2)
7

Oxygen extraction
Decreased DO2
Lactate (mmol/L)
6
5
4
3
2
1
0
Therapy Withdrawn in Brain Death Patient
0 10 20 30 40
SvO2 (%)
50 60 70 80
8

Venous oximetry
‣ Understand basic physiology of oxygen demand and supply
‣ Understand compensatory mechanisms when either
changes
‣ What is the incidence of abnormal values
‣ What is the clinical impact of abnormal values
‣ When are abnormal values acceptable and unacceptable
‣ Can you treat abnormal values, by what measures and for
how long to benefit the patient
9

Bracht et al. Crit Care 2007;11:R2
10

Venous oximetry
‣ Understand basic physiology of oxygen demand and supply
‣ Understand compensatory mechanisms when either
changes
‣ What is the incidence of abnormal values
‣ What is the clinical impact of abnormal values
‣ When are abnormal values acceptable and unacceptable
‣ Can you treat abnormal values, by what measures and for
how long to benefit the patient
11

Clinical relevance
60 patients abdominal surgery
Crit Care 2006;10:R158 48 elective surgery, 12 emergency surgery
12

Adequacy of CO
Resuscitation using restoration to normal of
traditional hemodynamics does not restore
parameters associated with adequate global blood
flow and tissue oxygenation
Normal SO2 in the right atrium as a target of
therapy improves outcome
Am J Emerg Med 1996;14(2):218-225 § N Engl J Med 2001;345(19):1368-1377
13

Venous oximetry
‣ Understand basic physiology of oxygen demand and supply
‣ Understand compensatory mechanisms when either
changes
‣ What is the incidence of abnormal values
‣ What is the clinical impact of abnormal values
‣ When are abnormal values acceptable and unacceptable
‣ Can you treat abnormal values, by what measures and for
how long to benefit the patient
14

The New England Journal of Medicine
EARLY GOAL-DIRECTED THERAPY IN THE TREATMENT OF SEVERE SEPSIS
AND SEPTIC SHOCK
EMANUEL
ALEXANDRIA
RIVERS
MUZZIN
, M.D., M.P.H., B
, B.S., BERNHARD
FOR
THE
EARLY
RYANT
KNOBLICH
GOAL
NGUYEN,
M.D., S
, M.D., EDWARD
-DIRECTED
ABSTRACT
Background Goal-directed therapy has been used
for severe sepsis and septic shock in the intensive care
unit. This approach involves adjustments of cardiac
preload, afterload, and contractility to balance oxygen
THERAPY
UZANNE
PETERSON
HAVSTAD
, P
H
COLLABORATIVE
, M.A., J
.D., AND
GROUP*
ULIE
MICHAEL
RESSLER
TOMLANOVICH
, B.S.,
, M.D.,
THE systemic inflammatory response syndrome
can be self-limited or can progress to
severe sepsis and septic shock. 1 Along this
continuum, circulatory abnormalities (intravascular
volume depletion, peripheral vasodilatation,
15

Venous oximetry
‣ Understand basic physiology of oxygen demand and supply
‣ Understand compensatory mechanisms when either
changes
‣ What is the incidence of abnormal values
‣ What is the clinical impact of abnormal values
‣ When are abnormal values acceptable and unacceptable
‣ Can you treat abnormal values, by what measures and for
how long to benefit the patient
16

Treatment of low ScvO2
‣ Goal to treat abnormal ScvO2 is to restore the balance
between oxygen demand and oxygen delivery
‣ Decrease oxygen demand
‣ Mechanical ventilation, analgesia, sedation, antipyretics
‣ Increase oxygen delivery
‣ Increase arterial oxygen content (hemoglobin and oxygen
saturation)
‣ Increase cardiac output (fluids, inotropes, mechanical support)
19

For how long should we
target Scv(v)O2
‣Short duration following admission (4-8 hours)
‣ N Engl J Med 2001;345:1368
‣ BMJ 2004;329:258
‣ Crit Care 2005;9:R678
‣Longer duration following admission (24 hours)
‣ JAMA 1993;270:2699
‣ Anesth Analg 2000;90:1052
20

Low ScvO2
Increase in MAP
MAP 65 MAP 75 MAP 85
DO2 (ml/min.M 2 )** 620±59 670±59 703±74
VO2 (ml/min.M 2 ) 119±12 138±20 153±20
SvO2 (%) 76±3 76±2 70±2
Lactate (mmol/l) 3.1±0.9 2.9±0.8 3.0±0.9
Urinary output (ml) 49±18 56±21 43±13
Cap.flow (ml/min.100g) 6.0±1.6 5.8±1.2 5.3±0.9
RBCvelocity (au) 0.42±0.06 0.44±0.06 0.42±0.06
Pa-rCO2 (mmHg) 13±3 17±3 16±3
LeDoux et al. Crit Care Med 2000;28:2729
21

Do
Nothing
Fluid
respnsiveneess
≥ 70%
yes
no
SvO2
< 70%
comfort
Fluids
Inotropes
SaO2
95-100 %
Hb
>4.3 mmol/l
VO2
< 95%
< 4.3 mmol/l
Pain - Agitation
FiO2
PEEP
Transfusion
Analgesia
Sedation
Tim Jansen: Adapted from: Pinsky - Vincent Crit Care Med 2005;33:1119-1122
22

Low ScvO2
Increase in CO
Effect of low dose dobutamine on ScvO2
23

Hour following
admission 0 2 4 6 8
BP 100/50 109/58 105/44 95/43 100/39
HR 148 148 133 132 143
CVD 11 21 16 17 12
Lactate 4.2 4.5 4.8 3.7 2.2
ScvO2 67% 52% 78% 71% 69%
Fluids (ml) x 1670 2000 575 725
Dobu x 3.2 6.3 11.0 11.0
Norepi x 0.56 0.78 0.69 0.69
NTG x - 1 mg/h 2 mg/h 2 mg/h
24

Conclusions
‣ ScvO2 reflects the balance between oxygen demand and oxygen supply
to the tissues
‣ Restoring the balance between demand and supply is the goal of
treatment in clinically relevant abnormal ScvO2
‣ Abnormal ScvO2 is frequently present on admission and following
initial resuscitation and cannot be predicted from global
hemodynamics
‣ Low ScvO2 is associated with increased morbidity and mortality
‣ Targeting normal ScvO2 is possible and benefits patients
‣ Monitoring ScvO2 should be standard practice in high risk patients
25