Value of ScvO2 Monitoring in PICU - The Canadian Association of ...

The Value of Continuous
ScvO 2 Monitoring in PICU
Caulette Young, RN, BSN
Pediatric Clinical Nurse Consultant
Edwards Lifesciences, LLC

Disclaimers
• Paid consultant for Edwards Lifesciences, LLC
• Pediatric critical care products
• Provide education, in-services, research &
• Provide education, in-services, research &
technical advice

Objective
The goal in PICU is to maintain a balance
between oxygen delivery and consumption.
Continuous ScvO 2 allows the clinician to
2
assess oxygen delivery and consumption in
real-time. Imbalances can rapidly be identified
and treated earlier with improved outcomes.

What is our main goal for patients in ICU?
• Adequate oxygenation & tissue
perfusion
How can we achieve this?
• Ensure a balance between oxygen
delivery & oxygen consumption
How can we assess for this?
• Continuous monitoring ScvO 2

Reflection vs Transmission
Spectrophotometry
74
LED photo detector
Receiving fiber
Transmission fiber
SVC

Benefits of Continuous vs. Intermittent
• Real-time, no waiting for analysis results
• Decrease risk for infection
• Decrease risk for transfusions
• Early warning
– Identification of DO 2/VO 2 imbalance
– Traditional hemodynamic monitoring unreliable
• Cost savings
– Financial
– Resources of staff
– Prevention

Using continuous ScvO 2 monitoring
to evaluate tissue oxygenation at
the bedside enables the clinician to
detect early alterations in oxygen
balance.
(Goodrich 2006 Crit Care Nurs Clin N Am)

“Oxygen delivery does not provide
information about the adequacy of
tissue oxygenation.”
Curley & Harmon
Critical Care Nursing of Infants and Children 2 nd Ed

Uncorrected imbalances
• Shift in dissociation curve: left or right
• Hypoxia / hypoxemia
• Acidosis
• Redistribution or maldistribution of blood
• MODS
• Pulmonary hypertension
• Cardiovascular collapse / cardiac arrest
• Necrosis & irreversible cell death
• Death

SVC-RA
junction
What is
ScvO 2?
Central venous oxygen saturation
measured at the SVC-RA junction
Indicative of balance between
oxygen delivery & consumption
Trends well with SvO 2
Can be used as a surrogate for
adequate cardiac index
Early warning indicator
Used to guide therapy in sepsis &
congenital cardiac surgery

ScvO 2
Oxygen Delivery Oxygen Consumption
Hemoglobin Cardiac
output
Heart
rate
Stroke
volume
Oxygenation
/ventilation
FiO 2
Preload Afterload Contractility
Metabolic demands

SvO 2 or ScvO 2: What’s the difference?
• PA catheter or central line
• Global or regional
– SvO 2 represents mixed venous blood from:
• SVC ≅ 70%
• CS ≅ 37%
• IVC ≅ 80%
– ScvO2 represents blood returning from upper or
lower body (depending on site)
• Normal values:
– SvO 2 (60-80%)
– ScvO 2 (70-75%)
• ScvO 2 usually runs ~7% higher than SvO 2
• Difference can widen in shock states when
perfusion redistribution occurs

Regional oxygen saturation from upper body
Trends with SvO SvO2 values, nearly interchangeable
Reinhart et al Intensive Care Med. 2004
ScvO 2 ……
SvO 2
ScvO 2 ……
SvO 2

Has been considered a surrogate for cardiac
output / index in pediatrics
Tibby et al Arch Dis Child 2003

“Adequate” oxygenation can only be defined when
tissue O 2 supply matches tissue O 2 demand
Usually consumption (VO 2) independent of delivery (DO 2)
DO 2I= CO x SaO 2 x Hgb x 1.34 x 10 = 650 + 50 ml/min/m 2
VO 2I= CO x (SaO 2-SvO 2) x Hgb x 1.34 x 10 = 120-200 ml/min/m 2
If VO 2 increases or DO 2 decreases, tissue oxygenation is
maintained by increasing oxygen extraction
O 2ER = VO 2/DO 2 x 100 = 25 + 2%
If DO 2 drops below a critical level, oxygen extraction
becomes exhausted resulting in VO 2 dependent on DO 2 or
oxygen debt
Tissue hypoxia occurs!
Note: O 2ER increases well before lactate begins to accumulate

ScvO 2 / SvO 2
70-75%
< 70% and > 50%
< 50% and > 30%
Physiology
Normal extraction
(non-cyanotic cardiac)
Compensatory extraction
( demand or supply)
Limits of extraction
(beginning of lactic
acidosis)
< 30% and > 25% Severe lactic acidosis
< 25% Cellular death
Bloos & Reinhart; Intensive Care Med (2005) 31:911–913

Factors to be considered in Oxygenation
Alveolar-pulmonary capillary O 2 transport
• Gas exchange in terminal portion of lungs
O2 transport in the blood
• Hemoglobin & oxyhemoglobin
− Arterial O2 content (CaO2) − Oxyhemoglobin dissociation curve
− O2 delivery (DO2) Cellular respiration
• Oxygen consumption
• Oxygen extraction ratio (O 2ER)
− Tissue oxygenation dependent on
microcirculation
− Microcirculation adjusts to enhance O 2
extraction
DO 2
VO 2

VO 2
Once O 2 extraction
has been maximized,
VO 2 becomes
dependent on DO 2
Critical O 2
DO 2
Tissues extract
what’s needed. If
DO 2 decreases or
VO 2 increases,
O 2ER increases
to meet demands
Pathologic
Tissue hypoxia
occurs when VO 2
exceeds DO 2

Normal
O O2 ER
DO 2
O 2ER may increase to
meet O 2 demands, when
DO 2 is decreased or
VO 2 is increased.
Normal O 2ER 25-30%
Pathologic

VO VO2 O 2 debt: Why is it important?
It needs to be paid back with interest
O 2 debt
Time
Interest
DO 2 needs to meet current
O 2 needs and satisfy the
needs that were previously
unmet

Oxygen Saturation Values
Site Acyanotic Cyanotic
Superior vena cava 70-75% 35-55%
Right atrium / ventricle 75% 67% / 80%
Pulmonary vein 95% 88%
Aorta 95% 80%
Left atrium / ventricle 95% 90%
Inferior vena cava 78%

Pulmonary Hypertension in Post-op Cardiac
Critical Heart Disease in Infants & Children 2 nd Ed
Stimulant: Pain, agitation, hypoxia, hypothermia, suctioning,
acidosis, hypercarbia
PVR R L shunt
Q p Q s
ScvO 2 /SvO 2
Hypoxic vasoconstriction
PaO 2
PaCO 2
DO 2
Cardiac arrest

When is Change Significant?
• Change from baseline ≥ 5-10%
sustained > 5 minutes
• Values may fluctuate ± 5%, with
activities or interventions (i.e.
suctioning)
• Slow recovery may indicate
cardiopulmonary system’s inability to
respond to increases in O 2 demand

Causative Factors
(Decreased O 2delivery)
↓Cardiac Output (CO)
ScvO 2 < 70%
↓O 2 Saturation (SaO 2)
↓ Hgb concentration
Clinical Conditions
Left ventricular dysfunction
Shock
Hypovolemia
Hypoxemia
Lung Disease
Respiratory failure
Anemia
Hemorrhage
Hemodilution
Dyshemoglobinemias

Causative Factors
Increased O 2 consumption
ScvO 2 < 70%
Clinical Conditions
Traumatic brain injury (138%)
Burns (100%)
Sepsis (50-100%)
Shivering (50-100%)
MODS (20-80%)
Increased WOB (40%)
Position change (31%)
Suctioning (27%)
Bath (23%)
Dressing change (10%)
Fever each °C (10%)

Causative Factors
Increased O 2 delivery
(DO 2)
ScvO 2 > 70%
Decreased O 2 consumption
(VO 2)
Clinical Conditions
PaO 2
Hemoglobin
Cardiac output
Anesthesia
Hypothermia
Dyshemoglobinemias
Venous hyperoxia

Understanding the clinical significance of
SvO 2 (ScvO 2) measurements….can help
guide clinical decision-making to assure
adequate oxygenation to meet tissue
needs.
(Sanders, 1997 Applied Pathophysiology)

“Useful in
patient types”
• Congenital cardiac surgery
• Pediatric sepsis
• High risk surgery
• Respiratory failure
• Trauma
• Burns
• Jugular bulb
“Useful in patient
management”
• Fluid administration &
boluses
• Vasoactive infusions
• Blood transfusions
• Ventilatory management
• Arrest resuscitation
• End-organ perfusion

Thank You!
“Hypoxia not only stops the machine, it wrecks
the machinery”
John Scott Haldane, 1880
Caulette_young@edwards.com
www.Edwards.com/pediasat