Neurological complaints are a common cause of morbidity following cardiac surgery. Adverse central nervous system outcomes include stroke, neurocognitive decline, and delirium. The risk of stroke increases with age and may be as high as 7-9% in patients over 75 years old. Neurocognitive decline can occur in 60% of patients at 1 week post-op and 25-30% between 2 months and 1 year post-op. Neurological injuries following cardiac surgery can be caused by embolization, hypoperfusion, tissue ischemia, or neurodegeneration. Near-infrared spectroscopy is a non-invasive method for monitoring regional cerebral oxygen saturation and detecting cerebral desaturations in real-time, which has been shown

2. Introduction…
Increased PeriOp Complications
Broader
Indications
Cardiac Surgery
Increased Age
at presentation
Comorbidities

3. Neurological
Complaints are
second only to Cardiac
problems for
increasing morbidity
in the post op period

4. Adverse CNS Outcomes
Age Incidence Of Stroke
<64 yrs <1%
65-75 yrs 5%
> 75 yrs 7-9%
Neurocognitive decline may occur
in 60% at 1 week to
25 to 30% between 2 months and 1 year

5. Adverse CNS Outcomes
Type I
Cerebral death
Non-fatal stroke / TIA
Focal injury
Stupor
Encephalopathy
Coma
Type II
Deterioration in
cognitive function
Deficit in
memory
Seizures

6. The big “WHY”…
Brain Injury
Systemic
inflammatory
response
EmbolisationCerebral
Hypoperfusion
Major
Minor
Tissue Ischemia Neuro-degeneration
CPP = MAP -
ICT

7. The big “WHY”…
Etiology :- Multifactorial.
Off Pump Procedures:-
Hypotension,
Anemia
low oxygen Saturation,
Genetic factors,
Anesthetic agents
Previous neurological
pathology
On Pump Procedures:-
Hypotension,
Anemia
low oxygen Saturation,
Genetic factors,
Anesthetic agents
Previous neurological
pathology
Embolisation of gaseous
and particulate emboli

8. Monitoring is required to detect in timely manner.
Modalities include..
1. Electroencephalographic monitoring (EEG),
2. Serial measurements of jugular bulb saturations (jvSO2) and
3. Cerebral oximetry based on near infrared spectroscopy (NIRS)
• Cerebral oximetry is non-invasive, user friendly and is not
influenced by the depth of anesthesia. It can even be utilized as
a monitor to detect ischemia in real-time during a circulatory
arrest period.
Prevention

9. History …
** Jobsis FF. Noninvasive, infrared monitoring of cerebral and myocardial oxygen sufficiencyand circulatory parameters. Science.
1977;198:1264–1267.
* Chance B. (1954). Spectrophotometry of intracellular respiratory pigments. Science 120, 767–775.10.1126/science.120.3124.767
CHANCE
1954
Absorbtion of
light in the NIR
spectrum by
chromatophores
involved in
mitochondrial
respiratory
chain
JOBSIS
1977
“the relatively high degree
of transparency of
myocardial and brain tissue
in the near-infrared (NIR)
range enabled real-time
non-invasive detection of
tissue oxygen saturation
using transillumination
spectroscopy”
22 years

10. Principle: NIRS
“Biological Spectroscopic Window”
exists at the wavelength range 660-940 nm
because only a few chromophores like Hb and HbO2 strongly
absorb light in this spectra range,
allowing light to penetrate tissue to a great distance.
Absorption of this light due to
other biological compounds and tissues such as water, lipids,
skin, and bone
is lower in magnitude,
and these biological compounds generally have a
flat absorption spectra,
*Silvay G, Weinreich A, Owitz S. et al. The cerebral function monitoring during open-heart surgery. Herz. 1978;3:270–275
McCormick PW, Stewart M, Ray P. et al. Measurement of regional cerebrovascular haemoglobin oxygen saturation in cats
using optical spectroscopy. Neurological Res. 1991;13:65–70.

12. principle...
• NIRS relies on the Beer-
Lambert law which describes a
relationship between
light behavior
and
concentration of a compound:
Log (I/Io) = L*C ;
I and Io are intensities of light at
detector and emmitter;
L is the path length;
C is Conc of the absorbing
compound.

13. For probe on the head, the thin
extra-cerebral tissue does not
interfere with brain monitoring.
NIRS monitors a “weighted
average” O2 saturation of blood in
small “gas-exchanging” vessels
with approximately 75% of the
signal originating from venules.
Pulse
Oximetry
Cerebral Oximetry
Pulsatility Pulsatile Non-Pulsatile
Light transmission
(usually)
Transmission
(usually)
Reflectance
Wavelength 660/940 nm 730/810 nm
Arterial
component
Mainly arterial 25% Arterial:75%
venous
Oxygen saturation Hb (arterial) Cerebral venous
saturation
LED 1 Emitter/1
sensor
1Emitter/2 sensor
Limitation Diathermy Diathermy
NIRS views the tissue circulation beneath the optical probe, somewhat
similar to Pulse Oximetry.
principle...

14. • In order to guarantee that only cerebral oxygen saturation is being
measured most commercially available oximeters minimize
extracerebral contamination by equipping the sensors with 2 light
detectors located at fixed distances from the light source.
• By simply subtracting the measurements obtained from the brain
detector from the scalp detector, extracerebral contamination can
be minimized.
principle...

15. Localized Area of Measurement
LED Emitter
Distal Detector
Proximal Detector
Hongo K, Kobayashi S, Okudera H, Hokama M, Nakagawa F. Noninvasive cerebral optical spectroscopy:
Depth-resolved measurements of cerebral haemodynamics using indocyanine green. Neurol Res. 1995;17(2):89-93.

16. Localized Area of Measurement
LED Emitter
Distal Detector
Proximal Detector
Hongo K, Kobayashi S, Okudera H, Hokama M, Nakagawa F. Noninvasive cerebral optical spectroscopy:
Depth-resolved measurements of cerebral haemodynamics using indocyanine green. Neurol Res. 1995;17(2):89-93.

17. Localized Area of Measurement
LED Emitter
Distal Detector
Proximal Detector
Hongo K, Kobayashi S, Okudera H, Hokama M, Nakagawa F. Noninvasive cerebral optical spectroscopy:
Depth-resolved measurements of cerebral haemodynamics using indocyanine green. Neurol Res. 1995;17(2):89-93.

19. Healthy Volunteers
Comparison to Jugular Bulb
Kim M, Ward D, Cartwright C, Kolano J, Chlebowski S, Henson L. Estimation of jugular venous O2 saturation from cerebral oximetry or arterial O2 saturation during isocapnic hypoxia. J Clin
Monit Comput. 2000;16(3):191-99.

20. Viz A Viz
BP & SPO2
Jugular Venous
Saturation
Whole Brain
Whole Body
Cerebral
Oximetry
Focal Brain

21. Left Brain
Right Brain
TIA
Systemic BP Compared to
Cerebral Perfusion
• With normal left brain arteries,
perfusion and rSO2 are
independent of blood pressure.
• With stenotic right brain
arteries, perfusion, rSO2 and
function are pressure-
dependent.
• Hypotension caused right
hemisphere TIA.
Blood pressure is an unreliable indicator of regional brain perfusion
Kashiwazaki D, Kuroda S, Terasaka S, Iwasaki Y. Detection of hemodynamic transient ischemic attack during hemodialysis with near-infrared
monitoring in a patient with internal carotid artery occlusion. Surg Neurol. 2007;68(3):292-4.

22. Unrecognized Ischemia in CABG
Underlying data and case notes on file ISC-10092.
22 | Covidien Respiratory and Monitoring Solutions | May 14, 2014 | Confidential

23. rSO2 may act as FIRST ALERT of
impending dysfunction
Contributor: David J. Rosinski, CCP
Underlying data and case notes on file ISC-10088.

24. Options
• There are presently four non-invasive cerebral oximetry devices
with FDA approval to measure and monitor cerebral tissue oxygen
saturation during the perioperative period.
1. INVOS cerebral oximeter (Somanetics Corporation, Troy, MI; now
Covidien, Boulder,CO); since 1993
2. FORE-SIGHT absolute cerebral oximeter (CAS Medical Systems,
Branford, CT); since, 2007
3. NONIN regional oximeter (Nonin Medical Inc. Minnesota,
MN);since 2009
4. CER-OX monitor (Ornim Medical Systems)
A fifth device, the NIRO series near-infrared spectrophotometer
(Hamamatsu, Photonic. Hamamatsu, Japan), is available in the
Japanese and European markets.

25. INVOS
• INVOS – In-vivo Optical Spectroscopy
• Non-invasive technology which acts as a “window” into body’s
microvasculature
• Monitor site-specific adequacy of perfusion in the brain or body
tissue directly beneath sensor.
• Provide real-time data regarding balance or imbalance of O2 supply
and demand.

26. Depth
How deep does it measures?
Measures 2.5 – 3cm beneath the sensor.
The differences in thickness of skull;
and the skin pigmentation do not
modify the readings.

27. Using INVOS in patients?

29. Most critical thing to do:
Cause the baseline saturation values follow a bell shaped curve
pattern,
rSO2 baselines should be obtain
prior to induction/supplemental
O2/sedation.
SET BASELINE
Heringlake study (2011) showed preoperative cerebral rSO2 values ≤ 50 were an
independent predictor of short & long term mortality in patients undergoing on-
pump cardiac surgery

30. Normal Values
• Normal rSO2 values in healthy cerebral tissue are 58-82.
• In cardiac patients, the baseline rSO2 values were 65 +/- 9.
• A reduced Value may be found during CPB at:
1. Initiation of CPB, secondary to Haemodilution.
2. Rewarming after CPB, due to an imbalance in oxygen supply
and demand.
3. At other times due to inadequate
bypass flow, hypocarbia,
inadequate MAP, or anaemia.

31. Normal Values
A difference of +/- 9 scale units of right-left rSO2 values are
acceptable
• Any values of > 10 scale units cause for further investigation
• Possible causes of asymmetry include:
– carotid / intracranial arterial stenosis
– infarction
– intracranial space-occupying lesion
– excessive frontal sinus fluid

32. Critical Values
A Common intervention trigger is taken as:
rSO2 <50
or 20% change from rSO2 baseline
Critical threshold for intervention is taken as :
rSO2 <45
or 25% change from rSO2 baseline

33. What to do…
1 Increase Inspired O2 to 100%
2 Check head and canula position to ensure adequate venous
drainage.
3 If PaCO2 < 40 mmHg; increase PaCO2 to > 40mmHg.
4 If MAP < 50 mmHg ; increase MAP > 60 mmHg.
5 If Hematocrit < 20%; Transfuse Blood.
6 If none of the above interventions improve cerebral saturation,
decrease cerebral Oxygen consumption by increasing depth of
anaesthesi
As stated by Murkin JM, Iglesias I, Bainbridgge D, Adams S, et al
Brain Oxygenation in Diabetic Patients during Coronary Surgery: A Randomized prospective Blinded Study.
Anesthesia and Analgesia. 2005;100:SCA1-116

34. INVOS Clinical Evidence

35. The INVOS™ System is the clinical referenced standard
in cerebral/somatic oximetry
• 800+ clinical references (600 peer reviewed) unique to
INVOS™ technology.
• Three prospective, randomized controlled trials.
• 800+ centers nationwide, including 90% and 80% of the top 10
adult and pediatric heart hospitals respectively (U.S. News &
World Report, 2010).
• Approximately 6,000 units worldwide.
• 250,000 procedures annually.

36. Improved Patient Outcomes
• Five centers studying 4,300 cardiac surgery patients showed that
monitoring reduced post-op neuro complications, generating a 1.66
day weighted average reduction in length of stay
Yao et al. Anesthesiology 2001;95:A152. Anesthesia & Analgesia 2001;92:SCA86
Iglesias et al. Heart Surgery Forum 2003;6:204
Ganzel et al. Presented at STS, January 28-30, 2002 Fort Lauderdale
Alexander et al. Annals of Thoracic Surgery 2002;373-C
Schmahl. Anesthesiology 2000;93:A399
0.0
0.5
1.0
1.5
2.0
2.5
3.0
LOSReduction(days)
2.1
2.7
1.4
1.7
1.2
Univ of
Louisville
Hackensack
Univ Med Ctr
Weill Medical
College, NY
St. Luke’s Med
Ctr, Milwaukee
Univ Western
Ontario

37. Improve Neuro Protection
Neuro dysfunction is not always embolic:
Detect and correct other factors
Cerebral Oxygen Desaturation is Associated With Early Postoperative
Neuropsychological Dysfunction in Patients Undergoing Cardiac
Surgery
Yao FS, Tseng CC, Ho CY, Levin SK, Illner P. Cerebral oxygen desaturation is associated with early postoperative neuropsychological dysfunction in patients undergoing cardiac surgery. J Cardiothorac Vasc
Anesth. 2004;18(5):552-558.

38. Goldman’s Study
• Retrospective Control, Prospective Intervention, Cardiac Surgery
Study
• n = 2,289, Utilized the STS Stroke definition
• Targeted rSO2 at or near patient baseline values in the intervention
group
• Anesthesia and surgical methods were similar for both groups
Control Group (Retrospective)
n = 1,245 No Interventions
Intervention Group (Prospective)
n = 1,034 Interventions per Protocol
Goldman S, et al. Heart Surg Forum 2004;7:E376-E378.

39. Reduced Complications
• INVOS™ System use on cardiac surgery patients reduced permanent stroke,
pulmonary complications and length of hospital stay
• Statistically significant decreases were achieved despite the INVOS System group
having a higher acuity than the control group (64.1% in NYHA class III and IV vs.
only 30.7%)
Goldman S, Sutter F, Ferdinand F, Trace C. Optimizing intraoperative cerebral oxygen delivery using noninvasive cerebral oximetry decreases the incidence of stroke for cardiac surgical
patients. Heart Surg Forum. 2004;7(5):E376-381.
.
2.01%
0.97%
0%
1%
1%
2%
2%
3%
Permanent Stroke
10.60%
6.80%
0%
2%
4%
6%
8%
10%
12%
Prolonged Ventilation
(p < 0.044) (p < 0.002)

40. Leveling the Playing Field for
Diabetics
30
69
201.6
9
30
132
0
50
100
150
200
250
Ventilation
p=0.002
ICU Stay
P=0.008
Hospital Stay
P=0.013
Control, Diabetics, n=26
Interventions, Diabetics, n=30
Randomized
Prospective
Blinded
Diabetic cardiac surgery patients
monitored with the INVOS™
System showed statistically
significant improvements over
unmonitored diabetic patients.
Murkin JM, Iglesias I, Bainbridge D, et al. Brain oxygenation in diabetic patients during coronary surgery: A randomized prospective blinded
study. Anesth Analg. 2005;100:SCA101.
Hours

41. Murkin JM, et al. Anesth Analg 2005;100:SCA101.
“Clinical outcomes were improved to the point that there
were no significant differences between diabetics and
non-diabetics, essentially leveling the playing field for
patients who traditionally have had poorer outcomes
during cardiac surgery.”
John M. Murkin, MD
Bringing Diabetics in Sync with Non-Diabetics

42. Casati A, et al. Anesth Analg. 2005 Sep;101(3):740-7.
“All cerebral desaturations occurred during the maintenance
period of general anesthesia and the episodes were never
associated with a concomitant reduction in arterial oxygen
saturation.”
• Time spent below the rSO2 desaturation threshold correlated
significantly with:
– MMSE decline (p = 0.01)
– Increased LOS (p = 0.007)
High Risk General Surgery
*MMSE – Mini-Mental State Examination
LOS - Length of stay

43. Predicting Cognitive Decline
• A risk score formula was created by multiplying the number of points
< 50 rSO2 by time in seconds
• Any combination of intra-op rSO2 value and time that resulted in
> 3,000 %seconds was found to increase risk
Slater JP, Guarino T, Stack J, et al. Cerebral oxygen desaturation predicts cognitive decline and longer hospital stay after cardiac surgery.
Presented at: 42nd Annual Meeting of the Society of Thoracic Surgeons, January 29-31, 2007; San Diego, CA.
rSO2 Value
Points Below
Desaturation
Threshold (50% rSO2) Multiplied By
Seconds Under
Threshold
Cognitive
Decline Risk
Score
45 5 X
600 (or 10
minutes)
3,000 %seconds
40 10 X
300 (or 5
minutes)
3,000 %seconds
35 15 X
200 (or 3.3
minutes)
3,000 %seconds

44. Predicting Cognitive Decline
Slater JP Cerebral Oxygen Desaturation Predicts Cognitive Decline and Longer Hospital Stay After Cardiac Surgery
Ann Thorac Surg 2009 Jan;(1) 87:36–45)

45. Patients with cerebral rSO2 oxygen desaturation score
of >3000 % seconds:
• Had a significantly higher risk of post-op cognitive
decline (p=0.024)
• Had a near three-fold increased risk of a prolonged
hospital stay > 6 days (p=0.007)
Slater JP Cerebral Oxygen Desaturation Predicts Cognitive Decline and Longer Hospital Stay After Cardiac Surgery
Ann Thorac Surg 2009 Jan;(1) 87:36–45)

46. Murkin JM, et al. Anesth Analg 2007;7(6):515
Hypothesis
By using the brain as an index organ,
interventions to optimize cerebral perfusion will
have a similarly beneficial effect on systemic
tissue perfusion and clinical outcomes

47. Standard deviation was also tighter, indicating
fewer outlier patients
Reduced ICU Stay
Murkin JM, Adams SJ, Novick RJ, et al. Monitoring brain oxygen saturation during coronary bypass surgery: a randomized, prospective study.
Anesth Analg. 2007;104(1):51-58.

48. “While none of the interventions undertaken are outside
the range of good clinical practice, it is clear that in the
absence of feedback from a specific indicator of end
organ compromise (e.g., cerebral desaturations), the
ability of the clinician to detect and optimize otherwise
silent but potentially adverse perturbations in clinical
variables remains limited.”
Murkin JM, et al. Anesth Analg 2007;7(6):515 Monitoring Brain Oxygen Saturation
During Coronary Bypass Surgery: A Randomized Prospective Study
Conclusion