By: Katie Lawton, RN, SNNP July 7, 2014 GRNS 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

 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

 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 (Covidien, 2011)

 Increase ◦ Rise in oxygen delivery ◦ Diminished oxygen demand  Decrease ◦ Decrease in oxygen delivery ◦ Uncompensated rise in demand (Covidien, n.d.)

 Helps in early identification of complications associated with ◦ Low cardiac output ◦ Shock and seizures ◦ Renal failure ◦ Neurological damage

(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 tissue Io: measured power of light at the emitter before it enters the tissue L: path length of the light from the emitter to detector C: concentration of the absorbing compound in the tissue (Kurth, 2006)

Spectrophotometer I/Io Probe

 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 regarding the oxygenation of tissues after light is emitted through the cuvette and relayed to the detector (Covidien, 2011)

 L: Left Cerebral  R: Right Cerebral  S: Somatic (Covidien, n.d.)

 Cerebral Probe Placement ◦ L/R side of forehead  Somatic ◦ Renal area ◦ Abdomen ◦ Upper extremites  (arm) ◦ Lower extremities  (calf, thigh) (Covidien, n.d.)

 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 (Scheeren, Schober & Schwarte, 2012)

 Lower oxygen usage than cerebral  rSO2 range: 5-20 higher than cerebral rSO2  Changes in variance may indicate pathology (Covidien, n.d.)

 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 Covidien. (2011). INVOS Cerebral/Somatic Oximeter. Retrieved from df&originalFileName= _Neonatal%20Brochure.pdf Hill, L. (n.d.). Cerebral blood flow and intracranial pressure. Retrieved from %20Cerebral%20physiology%20I.pdf Kurth. (2006). Near infrared spectroscopy. Retrieved from 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.e e18. doi: /j.jcrc 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), doi: /s y