Near-Infrared Spectroscopy

(NIRS)Monitoring

By: Katie Lawton, RN, SNNPJuly 7, 2014GRNS 5632

To understand what NIRS is

To understand how NIRS works

To become acquainted with the NIRS machine

and where to place the probe

To understand how NIRS can be utilized in the

clinical setting

To understand the beneficial significance of NIRS

Objectives

To understand the relationship between cerebral and somatic regional oxygen saturations

To become familiar with normal cerebral and somatic rSO2 ranges and interventions to improve rSO2

To provide research regarding the use of NIRS in the clinical setting in relation with patient outcomes

Objectives

Noninvasive, continuous tissue oxygenation monitoring ◦ Measures concentrations of oxyhemoglobin and

deoxyhemoglobin ◦ Used to measure regional oxygen saturation (rSO2)

Cerebral and Somatic Can be to measure oxygenation in:

Brain Renal Liver Extremities

◦ Commonly used during cardiac surgery and emergency situations

What is NIRS?

(Covidien, 2011)

Increase ◦ Rise in oxygen delivery ◦ Diminished oxygen demand

Decrease◦ Decrease in oxygen delivery◦ Uncompensated rise in demand

Factors That Affect Cerebral Oxygen Saturation

(Covidien, n.d.)

Helps in early identification of complications associated with

◦ Low cardiac output◦ Shock and seizures◦ Renal failure◦ Neurological damage

Why is NIRS used at the bedside?

Markers of Perfusion

(Covidien, n.d.)

Measure the relationship between light and concentration of the compound

Evaluates the transparency of tissues to the near infrared light to determine tissue oxygenation

Uses Beer-Lambert equation:

log (I/Io) = L C

I: measures power of light at the detector after it passes through the tissueIo: measured power of light at the emitter before it enters the tissueL: path length of the light from the emitter to detector C: concentration of the absorbing compound in the tissue

How does it work?

(Kurth, 2006)

Spectrophotometer

I/Io Probe

NIRS Equipment

The probe (I/Io) is placed on the on the skull (cuvette)

LED light is emitted in tissue (scalp, skull and brain)

Distal and proximal detector (on other end of probe)provide information regardingthe oxygenation of tissues after light is emitted through the cuvetteand relayed to the detector

How is the rSO2 determined by the probe placement?

(Covidien, 2011)

L: Left Cerebral R: Right Cerebral S: Somatic

NIRS Monitor

(Covidien, n.d.)

Cerebral Probe Placement◦ L/R side of forehead

Somatic◦ Renal area◦ Abdomen◦ Upper extremites

(arm)◦ Lower extremities

(calf, thigh)

Probe Placement

(Covidien, n.d.)

Relatonship Between Cerebral & Somatic Regions Cerebral

◦ High flow/ high extraction organ

◦ Compensatory mechanisms Autoregulation Flow metabolism coupling

◦ If autoregulation is intact, cerebral desaturations are a late warning of shock

Somatic◦ Variable flow/ low O2

extraction◦ Flow influenced by

sympathetic tone◦ Somatic desaturations

are early sign of shock due to compensatory mechanisms

(Covidien, n.d.)

Provides indication of hypoxia and cerebral perfusion

rSO2 range 60-80%◦ During cardiac surgery a drop in rSO2 <45% or a 25%

drop from the individual baseline is critical

Studies have shown a correlation between rSO2 in cardiac surgery and postoperative outcome◦ Intraoperative desatuartion associated with cognitive

dysfunction, stroke and increased length of stay with decreased rSO2

Cerebral Targets

(Scheeren, Schober & Schwarte, 2012)

Lower oxygen usage than cerebral

rSO2 range: 5-20 higher than cerebral rSO2

Changes in variance may indicate pathology

Somatic Targets

(Covidien, n.d.)

Interventions to Improve rSO2 Cerebral

◦ Increase cerebral perfusion pressure

◦ Increase arterial oxygen content

◦ Decrease cerebral vascular resistance

◦ Decrease cerebral metabolic rate

Somatic

◦ Increase cardiac output◦ Reduce sympathetic

outflow◦ Increase Hct◦ Avoid

hypothermia/hyperthermia

◦ Regional vasodilation

(Covidien, n.d.)

Covidien. (n.d). INVOS Cerebral/Somatic Oximeter: Quick reference guide for pediatric use. Retrieved from https://lane.stanford.edu/portals/cvicu/HCP_Equipment/NIRS-INVOS_Reference_Guide.pdf

Covidien. (2011). INVOS Cerebral/Somatic Oximeter. Retrieved from http://www.covidien.com/rms/imageServer.aspx?contentID=27565&contenttype=application/pdf&originalFileName=1.3.3.1_Neonatal%20Brochure.pdf

Hill, L. (n.d.). Cerebral blood flow and intracranial pressure. Retrieved from http://www.frca.co.uk/Documents/17 0907%20Cerebral%20physiology%20I.pdf

Kurth. (2006). Near infrared spectroscopy. Retrieved from http://www.pedsanesthesia.org/meetings/2006winter/pdfs/Friday_Kurth.pdf

Marimon, G.A., Dockery, W.K. Sheridan, M. J. & Agarwal, S. (2012). Near-infrared spectroscopy cerebral and somatic (renal) oxygen saturation correlation to continuous venous oxygen saturation via intravenous oximetry catheter. Journal of Critical Care, 27, 314.e13-314.e18.

doi: 10.1016/j.jcrc.2011.10.002

Scheeren, T.W.L, Schober, P. & Schwarte, L.A. (2012). Monitoring tissue oxygenation by near infrared spectroscopy: background and current applications. Journal of Clinical Monitoring and Computing, 26 (4), 279-287. doi: 10.1007/s10877-012-9348-y

References