Clinical and Technical Limitations of Cerebral and Somatic Near-Infrared Spectroscopy as an Oxygenation Monitor

Cerebral and somatic near-infrared spectroscopy monitors are commonly used to detect tissue oxygenation in various circumstances. This form of monitoring is based on tissue infrared absorption and can be influenced by several physiological and non-physiological factors that can induce error in the interpretation. This narrative review explores those clinical and technical limitations and proposes solutions and alternatives in order to avoid some of those pitfalls.

A validation method for near-infrared spectroscopy based tissue oximeters for cerebral and somatic tissue oxygen saturation measurements

We describe the validation methodology for the NIRS based FORE-SIGHT ELITE^® (CAS Medical Systems, Inc., Branford, CT, USA) tissue oximeter for cerebral and somatic tissue oxygen saturation (StO₂) measurements for adult subjects submitted to the United States Food and Drug Administration (FDA) to obtain clearance for clinical use. This validation methodology evolved from a history of NIRS validations in the literature and FDA recommended use of Deming regression and bootstrapping statistical validation methods. For cerebral validation, forehead cerebral StO₂ measurements were compared to a weighted 70:30 reference (REF CX_B) of co-oximeter internal jugular venous and arterial blood saturation of healthy adult subjects during a controlled hypoxia sequence, with a sensor placed on the forehead. For somatic validation, somatic StO₂ measurements were compared to a weighted 70:30 reference (REF CX_S) of co-oximetry central venous and arterial saturation values following a similar protocol, with sensors place on the flank, quadriceps muscle, and calf muscle. With informed consent, 25 subjects successfully completed the cerebral validation study. The bias and precision (1 SD) of cerebral StO₂ compared to REF CX_B was −0.14 ± 3.07%. With informed consent, 24 subjects successfully completed the somatic validation study. The bias and precision of somatic StO₂ compared to REF CX_S was 0.04 ± 4.22% from the average of flank, quadriceps, and calf StO₂ measurements to best represent the global whole body REF CX_S. The NIRS validation methods presented potentially provide a reliable means to test NIRS monitors and qualify them for clinical use.

Cerebral oxygen saturation after multiple perioperative influential factors predicts the occurrence of postoperative cognitive dysfunction

Background

Postoperative cognitive dysfunction (POCD) is a frequent complication in elderly patients undergoing major non-cardiac surgery, but its etiology is still unclear. Cerebral oxygen saturation (ScO₂) represents the balance of cerebral oxygen supply and demand. The aim of present study was to evaluate the relationship between perioperative ScO₂ and POCD, and to verify the hypothesis that the value of ScO₂ after multiple perioperative influential factors could predict POCD in elderly patients undergoing total knee arthroplasty (TKA).

Methods

Seventy eight Patients aged more than 65 years undergoing elective TKA with intrathecal anesthesia were enrolled. Cognitive functions were assessed one day before and 6 days after surgery, and POCD were defined according to ISPOCD. Demographics were recorded. Perioperative ScO₂, blood pressure (BP), blood gas analysis and other clinical data were monitored and recorded, then the decrease of ScO₂, BP and PaO₂ after influential factors were calculated.

Results

POCD occurred in 15 patients (19.2 %). BP decreased after anesthesia induction and tourniquet deflation, and PaO₂ decreased after cement implantation, then percentage decrease of BP was higher in POCD group. ScO₂ of POCD group is significantly lower than non-POCD group (P < 0.05), and the absolute value and percentage decrease of ScO₂ became significant between two groups after multiple influential factors. ScO₂ after all influential factors (anesthesia induction, cement implantation and tourniquet deflation) had the best predictive performance for POCD (AUC = 0.742), and the optimal threshold was 66.5 %.

Conclusions

Perioperative ScO₂ of patients with POCD is lower than patients without POCD. ScO₂ after multiple perioperative influential factors could be an effective predictor for POCD, which reveal an important role of ScO₂ decrease in the development of POCD and provide possible treatment target.

Survey of the clinical assessment and utility of near-infrared cerebral oximetry in cardiac surgery

OBJECTIVES

Near-infrared cerebral oximetry increasingly is used for monitoring during cardiac surgery. Nonetheless, the scientific basis for incorporating this technology into clinical practice, the indications for when to do so, and standard diagnostic and treatment algorithms for defining abnormal values are yet to be rigorously defined. The authors hypothesized that there would be (1) variation in clinical use and practices for near-infrared spectroscopy (NIRS), and (2) variation in management of patients when clinicians are provided with NIRS information. In order to test this hypothesis, they sought to assess the nature and strength of response heterogeneity among anesthesiologists and cardiac perfusionists when provided with cardiac surgery patient scenarios and cerebral oximetry data.

DESIGN

A prospectively collected survey.

SETTING

A hospital-based, multi-institutional, multinational study.

PARTICIPANTS

By e-mail, the authors surveyed the membership of the Society of Cardiovascular Anesthesiologists and the online Cardiovascular Perfusion Forum.

INTERVENTIONS

This survey was focused on ascertaining what actions clinicians would take in each scenario, given case information and cerebral oximetry tracings. Questions were based on 11 patient scenarios selected to represent small, large, symmetric, or asymmetric decreases in measured regional cerebral oxygen saturation (rScO2) encountered during cardiac surgery. Information on the respondents' (n = 796; 73% anesthesiologists) clinical practice, demography, and cerebral oximetry utilization was collected. An index of dispersion was used to assess response heterogeneity overall and within demographic subgroups.

MEASUREMENTS AND MAIN RESULTS

The majority of respondents indicated that cerebral oximetry monitoring was either useful or an essential monitor, especially perfusionists and clinicians who used cerebral oximetry most frequently. There were marked differences in responses between perfusionists and anesthesiologists for 4 of the 6 scenarios (p<0.005 for each of these 4 scenarios) occurring during cardiopulmonary bypass. Scenarios having greatest rScO2 reduction or asymmetry in rScO2 were associated with the highest dispersion, indicating least agreement in management. Scenarios with mild or moderate rScO2 reduction were associated with the lowest dispersion, indicating greater agreement in management.

CONCLUSIONS

Although experimental data gradually are accumulating to support the role for cerebral oximetry monitoring during cardiac surgery, the results of the present survey support the view that its role remains poorly defined, and consensus for its appropriate use is lacking. Importantly, the authors observed marked variation in the use, perceived utility, and management of patients for 4 of the 6 CPB scenarios between perfusionists and anesthesiologists who share the management of CPB. These findings support the need for well-designed, adequately-powered clinical trials examining the value of this technology.

Cerebral near-infrared spectroscopy monitoring and neurologic outcomes in adult cardiac surgery patients: a systematic review

BACKGROUND

Near-infrared spectroscopy is used during cardiac surgery to monitor the adequacy of cerebral perfusion. In this systematic review, we evaluated available data for adult patients to determine (1) whether decrements in cerebral oximetry during cardiac surgery are associated with stroke, postoperative cognitive dysfunction (POCD), or delirium; and (2) whether interventions aimed at correcting cerebral oximetry decrements improve neurologic outcomes.

METHODS

We searched PubMed, Cochrane, and Embase databases from inception until January 31, 2012, without restriction on languages. Each article was examined for additional references. A publication was excluded if it did not include original data (e.g., review, commentary) or if it was not published as a full-length article in a peer-reviewed journal (e.g., abstract only). The identified abstracts were screened first, and full texts of eligible articles were reviewed independently by 2 investigators. For eligible publications, we recorded the number of subjects, type of surgery, and criteria for diagnosis of neurologic end points.

RESULTS

We identified 13 case reports, 27 observational studies, and 2 prospectively randomized intervention trials that met our inclusion criteria. Case reports and 2 observational studies contained anecdotal evidence suggesting that regional cerebral O(2) saturation (rSco(2)) monitoring could be used to identify cardiopulmonary bypass cannula malposition. Six of 9 observational studies reported an association between acute rSco(2) desaturation and POCD based on the Mini-Mental State Examination (n = 3 studies) or more detailed cognitive testing (n = 6 studies). Two retrospective studies reported a relationship between rSco(2) desaturation and stroke or type I and II neurologic injury after surgery. The observational studies had many limitations, including small sample size, assessments only during the immediate postoperative period, and failure to perform risk adjustments. Two randomized studies evaluated the efficacy of interventions for treating rSco(2) desaturation during surgery, but adherence to the protocol was poor in one. In the other study, interventions for rSco(2) desaturation were associated with less major organ injury and shorter intensive care unit hospitalization compared with nonintervention.

CONCLUSIONS

Reductions in rSco(2) during cardiac surgery may identify cardiopulmonary bypass cannula malposition, particularly during aortic surgery. Only low-level evidence links low rSco(2) during cardiac surgery to postoperative neurologic complications, and data are insufficient to conclude that interventions to improve rSco(2) desaturation prevent stroke or POCD.