Cerebral oximetry

Introduction…

Increased PeriOp Complications

Broader Indications

Cardiac Surgery

Increased Age at presentation

Comorbidities

Neurological

Complaints are

second only to Cardiac

problems for

increasing morbidity

in the post op period

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

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

The big “WHY”…

Brain Injury

Systemic inflammatory

response

EmbolisationCerebral Hypoperfusion

Major

Minor

Tissue Ischemia Neuro-degenerationCPP = MAP -

ICT

The big “WHY”…

Etiology :- Multifactorial.

Off Pump Procedures:-

Hypotension,Anemialow oxygen Saturation, Genetic factors, Anesthetic agents Previous neurological pathology

On Pump Procedures:-

Hypotension,Anemialow oxygen Saturation, Genetic factors, Anesthetic agents Previous neurological pathologyEmbolisation of gaseous and particulate emboli

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

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

JOBSIS1977

“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

Principle: NIRS“Biological Spectroscopic Window”

exists at the wavelength range 660-940 nmbecause 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;3:270–275McCormick 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.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3484590/figure/F001/

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.

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...

• 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...

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.


LED Emitter

Distal Detector

Proximal Detector



LED Emitter

Distal Detector

Proximal Detector


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 ClinMonit Comput. 2000;16(3):191-99.

Viz A Viz

BP & SPO2

Jugular Venous Saturation

Whole Brain

Whole Body

Cerebral Oximetry

Focal Brain

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.

Unrecognized Ischemia in CABG

Underlying data and case notes on file ISC-10092.

22 | Covidien Respiratory and Monitoring Solutions | May 14, 2014 | Confidential

rSO2 may act as FIRST ALERT of

impending dysfunction

Contributor: David J. Rosinski, CCPUnderlying data and case notes on file ISC-10088.

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.

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.

DepthHow 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.

Using INVOS in patients?

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

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 inadequatebypass flow, hypocarbia,inadequate MAP, or anaemia.

Normal ValuesA 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

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

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 alBrain Oxygenation in Diabetic Patients during Coronary Surgery: A Randomized prospective Blinded Study. Anesthesia and Analgesia. 2005;100:SCA1-116

INVOS Clinical Evidence

The INVOS™ System is the clinical referenced standard

in cerebral/somatic oximetry

• 800+ clinical references (600 peer reviewed) unique toINVOS™ technology.

• Three prospective, randomized controlled trials.

• 800+ centers nationwide, including 90% and 80% of the top 10adult and pediatric heart hospitals respectively (U.S. News &World Report, 2010).

• Approximately 6,000 units worldwide.

• 250,000 procedures annually.

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

LO

S R

edu

ctio

n (

day

s)

2.1

2.7

1.4

1.7

1.2

Univ of

Louisville

Hackensack

Univ Med CtrWeill Medical

College, NY

St. Luke’s Med

Ctr, Milwaukee

Univ Western

Ontario

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 VascAnesth. 2004;18(5):552-558.

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 groupsControl 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.

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)

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

RandomizedProspectiveBlinded

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.

Ho

urs

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

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 ExaminationLOS - Length of stay

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 X600 (or 10

minutes)3,000 %seconds

40 10 X300 (or 5


35 15 X200 (or 3.3


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)

Patients with cerebral rSO2 oxygen desaturation scoreof >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)

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

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.

“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

Healthcare

Cerebral oximetry