Detection of critical cerebral desaturation thresholds by three regional oximeters during hypoxia: a pilot study in healthy volunteers

Regional cerebral oxygen saturation during initial mobilization of critically ill patients is associated with clinical outcomes: a prospective observational study

BACKGROUND

Vital signs help determine the safety of early mobilization in critically ill patients in intensive care units. However, none of these variables directly assess cerebral circulation. Therefore, we aimed to investigate the relationship of regional cerebral oxygen saturation (rSO2) and vital signs with in-hospital death in critically ill patients.

METHODS

This prospective study included critically ill patients admitted to the Uonuma Kikan Hospital Emergency Center who received physical therapy between June 2020 and December 2022. We continuously measured rSO2 during the initial mobilization using a wearable brain near-infrared spectroscopy device. With in-hospital death as the primary endpoint, the association between rSO2 and in-hospital death was assessed in Analysis 1 to determine the rSO2 cut-off value that predicts in-hospital death. In Analysis 2, patients were categorised into survival and non-survival groups to examine the temporal changes in vital signs and rSO2 associated with postural changes during mobilization.

RESULTS

Of the 132 eligible patients, 98 were included in Analysis 1, and 70 were included in Analysis 2. Analysis 1 demonstrated that lower premobilization rSO2 was independently associated with in-hospital death (odds ratio 0.835, 95% confidence interval 0.724-0.961, p = 0.012). Receiver operating characteristic curve analysis identified an optimal rSO2 cut-off value of 57% for predicting in-hospital death (area under the curve 0.818, sensitivity 73%, specificity 83%). Analysis 2 showed that rSO2 changes during mobilization were unrelated to changes in vital signs, suggesting rSO2 as an independent prognostic marker.

CONCLUSIONS

The results suggest that rSO2 measured during initial mobilization is associated with in-hospital death in critically ill patients.

Preoperative biomarkers associated with delayed neurocognitive recovery

To identify baseline biomarkers of delayed neurocognitive recovery (dNCR) using monitors commonly used in anesthesia. In this sub-study of observational prospective cohorts, we evaluated adult patients submitted to general anesthesia in a tertiary academic center in the United States. Electroencephalographic (EEG) features and cerebral oximetry were assessed in the perioperative period. The primary outcome was dNCR, defined as a decrease of 2 scores in the global Montreal Cognitive Assessment (MoCA) between the baseline and postoperative period. Forty-six adults (median [IQR] age, 65 [15]; 57% females; 65% American Society of Anesthesiologists (ASA) 3 were analyzed. Thirty-one patients developed dNCR (67%). Baseline higher EEG power in the lower alpha band (AUC = 0.73 (95% CI 0.48-0.93)) and lower alpha peak frequency (AUC = 0.83 (95% CI 0.48-1)), as well as lower cerebral oximetry (68 [5] vs 72 [3], p = 0.011) were associated with dNCR. Higher EEG power in the lower alpha band, lower alpha peak frequency, and lower cerebral oximetry values can be surrogates of baseline brain vulnerability.

Effect of Extracerebral Contamination on Near-infrared Spectroscopy as Revealed during Organ Donation: A Prospective Observational Study in Brain-dead Organ Donors

BACKGROUND

Near-infrared spectroscopy (NIRS) has been utilized widely in anesthesia and intensive care to monitor regional cerebral oxygen saturation (rScO2). A normal oxygenation of extracerebral tissues may overlay and thereby mask cerebral desaturations, a phenomenon known as extracerebral contamination. The authors investigated the effect of a cessation of extracerebral tissue perfusion on rScO2 in patients with anoxic brains.

METHODS

In a single-center, prospective, observational study, brain-dead adults undergoing organ donation were investigated. rScO2 was measured bifrontally using the INVOS 5100C/7100 as well as the ForeSight Elite system. To achieve an efficient conservation of organs and to prevent a redistribution of the perfusion fluid to other tissues, the aorta was clamped before organ perfusion. rScO2 was monitored until at least 40 min after aortic clamping. The primary outcome was the amount of extracerebral contamination as quantified by the absolute decrease in rScO2 after aortic clamping. Secondary outcomes were the absolute rScO2 values obtained before and after clamping.

RESULTS

Twelve organ donors were included. Aortic clamping resulted in a significantly (P < 0.001) greater absolute decrease in rScO2 when comparing the INVOS (43.0 ± 9.5%) to the ForeSight (27.8 ± 7.1%) monitor. Before aortic clamping, near-normal rScO2 values were obtained by the INVOS (63.8 ± 6.2%) and the ForeSight monitor (67.7 ± 6.5%). The rScO2 significantly (P < 0.001) dropped to 20.8 ± 7.8% (INVOS) and 39.9 ± 8.1% (ForeSight) 30 min after clamping, i.e., a condition of a desaturation of both extracerebral and cerebral tissues.

CONCLUSIONS

The abrupt end of extracerebral contamination, caused by aortic clamping, affected both NIRS monitors to a considerable extent. Both the INVOS and the ForeSight monitor were unable to detect severe cerebral hypoxia or anoxia under conditions of normal extracerebral oxygenation. While both NIRS monitors may guide measures to optimize arterial oxygen supply to the head, they should not be used with the intention to detect isolated cerebral desaturations.

EDITOR’S PERSPECTIVE

Differences of cerebral oxygen saturation in dialysis patients: a comparison of three principals of near infrared spectroscopy

PURPOSE

It has been reported that cerebral oxygen saturation (rSO2) measured by near infrared spectroscopy is low in dialysis patients. We compared the rSO2 values of dialysis patients before living donor kidney transplantation and their donors as controls by using three spectroscopes that utilize different principals, the INVOS 5100C (spatially resolved spectroscopy), FORE-SIGHT ELITE (modified Beer-Lambert law) and tNIRS-1 (time-resolved spectroscopy).

METHODS

Before induction of anesthesia, the sensors of one of the three spectroscopes were placed on the forehead and rSO2 values were recorded followed by the same measurement using the other two spectroscopes. The primary objective was to compare the rSO2 values of the dialysis patients and controls using the three spectroscopes by the unpaired t test. Then we compared the rSO2 values among the spectroscopes in both dialysis patients and controls by one-way ANOVA. Finally, we examined the relations between the rSO2 values and the physiological values by using the Pearson correlation coefficient.

RESULTS

Fifteen pairs of dialysis patients and controls were studied. With the INVOS 5100 C, the values of the dialysis patients (59.7 ± 9.7% (mean ± standard deviation) were 13% lower than those of the controls (73.3 ± 6.9%) (P < 0.01). With the tNIRS-1, the values were 57.8 ± 4.8% in the dialysis patients and 63.3 ± 3.5% in the controls (P < 0.01). Almost no differences were observed with the FORE-SIGHT ELITE (71.6 ± 4.9% [dialysis patients] vs. 70.8 ± 4.3% [Controls]) (P = 0.62). Among the spectroscopes, the values were significantly different in both dialysis patients and controls. For the INVOS 5100C and tNIRS-1, correlation coefficients between rSO2 values and blood Hb and serum Alb were more than 0.5.

CONCLUSIONS

The rSO2 values for comparisons between the dialysis patients and the controls were different according to differences of the principles of the near infrared spectroscopes. In the INVOS 5100C and tNIRS-1, rSO2 values may be related to blood Hb and serum Alb.

Cerebral tissue oximeter suitable for real-time regional oxygen saturation monitoring in multiple clinical settings

Maintenance of adequate blood perfusion and oxygen delivery is essential for cerebral metabolism. Cerebral oximeters based on near-infrared spectroscopy (NIRS) have been used for noninvasive, continuous, real-time monitoring of cerebral oxygen saturation and management of cerebral oxygen adequacy perioperatively and intraoperatively in various clinical situations, such as cardiac surgery, anesthesia, and cerebral auto-regulation. In this study, a portable and modular cerebral tissue oximeter (BRS-1) was designed for real-time detection of regional oxygen saturation over the brain, finger, or other targeted body tissues, as well as for wireless cerebral oxygenation monitoring. The compact and lightweight design of the system makes it easy to use during ambulance transport, in an emergency cart, or in an intensive care unit. The system performance of the BRS-1 oximeter was evaluated and compared with two US FDA-cleared cerebral oximeters during a controlled hypoxia experiment. The results showed that the BRS-1 oximeter can be used for real-time detection of cerebral desaturation with an accuracy similar to the two commercial oximeters. More importantly, the BRS-1 oximeter is capable of capturing cerebral oxygen saturation wirelessly. The BRS-1 cerebral oximeter can provide valuable insights for clinicians for real-time monitoring of cerebral/tissue perfusion and management of patients in prehospital and perioperative periods.

Postoperative delayed neurocognitive recovery: Evaluation of its incidence and correlation with intraoperative cerebral desaturation - A prospective observational study

BACKGROUND

Delayed neurocognitive recovery (DNR) is commonly seen in patients in the postoperative period. Literature has shown that monitoring cerebral desaturation intraoperatively can predict the development of DNR in elderly patients undergoing surgery in prone position. This prospective observational study was conducted in patients of all ages, with the primary objective to determine the incidence of DNR and its correlation with cerebral oximetry. The secondary objectives were to determine if intraoperative cerebral desaturation influenced the neuropsychometric variables from preoperative to postoperative period.

METHODS

This study included 61 patients, aged > 18 years undergoing spinal surgery in prone position. An evening before surgery and at 48 h postoperatively, patients were subjected to neuropsychological examination; Hindi Mental State Examination, Colour Trail Test 1 (CTT 1), CTT 2, Auditory Verbal Learning (AVLT) tests conducted by principal investigator (PI). DNR was defined as a 20% change in any of the test scores from the baseline. rSO₂ was recorded bilaterally every 10 min throughout surgery by an independent person. Cerebral desaturation was defined as a 20% drop in rSO₂ from the control value.

RESULTS

The incidence of DNR was 24.6%. The duration of anesthesia and cerebral desaturation were found to be independently predictive of DNR, with each hour of anesthesia causing a two-fold increase in the chances of development DNR (P = 0.019) and presence of cerebral desaturation causing a 6-fold increase (P = 0.039). CTT 1 and CTT 2 tests had significantly larger increase in test scores in the postoperative period, in patients with cerebral desaturation.

CONCLUSION

Duration of anesthesia and cerebral desaturation were factors predictive of the development of DNR in patients undergoing spine surgery in prone position.

Neuromonitoring and Neurocognitive Outcomes in Cardiac Surgery: A Narrative Review

Neurocognitive dysfunction after cardiac surgery can present with diverse clinical phenotypes, which include postoperative delirium, postoperative cognitive dysfunction, and stroke, and it presents a significant healthcare burden for both patients and providers. Neurologic monitoring during cardiac surgery includes several modalities assessing cerebral perfusion and oxygenation (near-infrared spectroscopy, transcranial Doppler and jugular venous bulb saturation monitoring) and those that measure cerebral function (processed and unprocessed electroencephalogram), reflecting an absence of a single, definitive neuromonitor. This narrative review briefly describes the technologic basis of these neuromonitoring modalities, before exploring their use in clinical practice, both as tools to predict neurocognitive dysfunction, and with a bundle of interventions designed to optimize cerebral oxygen supply, with the aim of reducing postoperative delirium and cognitive dysfunction following cardiac surgery.

Near-infrared spectroscopy device selection affects intervention management for cerebral desaturation during cardiopulmonary bypass surgery

OBJECTIVE

Currently, several near-infrared spectroscopy oximetry devices are used for detecting cerebral ischemia during cardiopulmonary bypass (CPB) surgery. We investigated whether two different models of near-infrared spectroscopy oximetry devices affect the assessment of cerebral ischemia and its management during CPB.

METHODS

From January 2017 to August 2017, 70 adult cardiovascular surgery cases were randomly assigned to 1 of 2 different near-infrared spectroscopy oximetry devices. The devices were INVOS 5100C (Medtronic, Minneapolis, MN, USA) (group I; n = 35) and FORE-SIGHT ELITE (CAS Medical Systems, Branford, CT, USA) (group F; n = 35).

RESULTS

There were no significant differences in patient characteristics. The rSO₂ values were significantly higher for patients in group F than for patients in group I. Scalp-Cortex distance showed negative correlations with the mean rSO₂ values in group I (P = 0.01). Interventions for low rSO₂ during CPB for groups I and F were increase perfusion flow (13:5; P = 0.03), blood transfusion (7:1; P = 0.02), and both (6:1; P = 0.04), respectively. The Scalp-Cortex distance in group I was significantly longer in patients who required intervention than in patients who did not (17.1 ± 2.5 vs 15.1 ± 1.6 mm; P = 0.007).

CONCLUSIONS

It is inappropriate to use the same intervention criteria for different near-infrared spectroscopy oximetry devices. Moreover, brain atrophy influence rSO₂ values depending on device selection. It is important to note that inappropriate device selection may misguide perfusionists into performing unnecessary or excessive intervention during CPB.

Comparison of basic regional cerebral oxygen saturation values in patients of different ages: a pilot study

Objective

To explore the basic values of regional cerebral oxygen saturation (rSO₂) among different age groups.

Methods

One hundred twenty patients who were scheduled for elective surgery aged 0 to 80 years (American Society of Anesthesiologists [ASA] physical status I or II) or neonates just after birth via cesarean section were enrolled and divided into the following six groups: infant (0 month and ≤12 months), toddler (>1 and ≤3 years old), preschool (>3 and ≤6 years old), school age (>6 and ≤18 years old), adult (>18 and ≤65 years old), and elderly (>65 and ≤80 years old) groups. There were 20 patients in each group.

Results

The basic values of rSO₂ in infant, toddler, preschool, school age, adults, and elderly groups were 70.41% ± 4.66%, 72.43% ± 3.81%, 70.77% ± 3.27%, 70.62% ± 2.20%, 69.76% ± 6.02%, and 62.69% ± 3.14%, respectively. The basic value in the elderly group was lower compared with other five groups. There was no significant difference among infant, toddler, preschool age, school age, and adult groups.

Conclusions

The basic value of rSO₂ in elderly patients is lower. Age is an important factor that affects the underlying value of rSO₂.

Absolute quantification of cerebral tissue oxygen saturation with multidistance broadband NIRS in newborn brain

Tissue oximetry with near-infrared spectroscopy (NIRS) is a technique for the measurement of absolute tissue oxygen saturation (StO2). Offering a real-time and non-invasive assessment of brain oxygenation and haemodynamics, StO2 has potential to be used for the assessment of newborn brain injury. Multiple algorithms have been developed to measure StO2, however, issues with low measurement accuracy or extracranial tissue signal contamination remain. In this work, we present a novel algorithm to recover StO2 in the neonate, broadband multidistance oximetry (BRUNO), based on a measurement of the gradient of attenuation against distance measured with broadband NIRS. The performance of the algorithm was compared to two other published algorithms, broadband fitting (BF) and spatially resolved spectroscopy (SRS). The median error when recovering StO2 in light transport simulations on a neonatal head mesh was 0.4% with BRUNO, 4.2% with BF and 9.5% with SRS. BRUNO was more sensitive to brain tissue oxygenation changes, shown in layered head model simulations. Comparison of algorithm performance during full oxygenation-deoxygenation cycles in a homogeneous dynamic blood phantom showed significant differences in the dynamic range of the algorithms; BRUNO recovered StO2 over 0-100%, BF over 0-90% and SRS over 39-80%. Recovering StO2 from data collected in a neonate treated at the neonatal intensive care showed different baseline values; mean StO2 was 64.9% with BRUNO, 67.2% with BF and 73.2% with SRS. These findings highlight the effect of StO2 algorithm selection on oxygenation recovery; applying BRUNO in the clinical care setting could reveal further insight into complex haemodynamic processes occurring during neonatal brain injury.

Tissue oxygenation indices of cerebrovascular autoregulation in healthy volunteers: a comparison of two NIRS devices

BACKGROUND

Correlation coefficients between blood pressure and cerebral oxygen saturation measured using near-infrared spectrometry may be used to derive the tissue oximetry index of cerebral autoregulation. Cerebral oxygen saturations demonstrate poor agreement between near-infrared spectrometers however it is unclear if measurements of autoregulation are similarly specific to the equipment used.

METHODS

Cerebral oxygen saturation was monitored bilaterally in 74 healthy volunteers using both the FORE-SIGHT and EQUANOX monitors in random order. The tissue oximetry index was calculated during changes in blood pressure induced by isometric handgrip manoeuvres and the mean bias and limits of agreement were calculated.

RESULTS

Tissue oximetry index measured by FORE-SIGHT was higher than EQUANOX (0.21 ± 0.16 versus 0.15 ± 0.17, P < 0.001) and limits of agreement were -0.24 to 0.36. Baseline cerebral oxygen saturation by FORE-SIGHT was lower than EQUANOX by 1.48% (CI95% 0.63-2.33) and limits of agreement ranged from -11.8% to 8.8%.

CONCLUSIONS

The substantial bias and wide limits of agreement for the tissue oximetry index as a measure of cerebral autoregulation indicate that values must be treated as specific to models of near-infrared spectrometers.

Approaches for calibration and validation of near-infrared optical methods for oxygenation monitoring

Pulse oximetry for arterial oxygenation monitoring and tissue oximetry for monitoring of cerebral oxygenation or muscle oxygenation are based on quantitative in vivo diffuse optical spectroscopy. However, in both cases the information on absolute or relative concentration of human tissue constituents and especially on hemoglobin oxygenation can often not be retrieved by model-based analysis. An in vivo calibration against an accepted reference measurement can be a practical alternative. Pulse oximeters and most of commercial cerebral tissue oximeters rely on empirical calibration based on invasive controlled human desaturation studies. As invasive in vivo tests on healthy subjects are ethically disputable and should be limited to exceptional cases this calibration practice is unsatisfactory. We present the current status and problems of calibration and validation in pulse oximetry and cerebral tissue oximetry including the pros and cons of in vivo as well as in vitro methods. We emphasize various digital and physical phantom approaches and discuss the prospects of their application and possible further developments.

Comparison of tissue oximeters on a liquid phantom with adjustable optical properties: an extension

Cerebral near-infrared spectroscopy (NIRS) oximetry may help clinicians to improve patient treatment. However, the application of NIRS oximeters is increasingly causing confusion to the users due to the inconsistency of tissue oxygen haemoglobin saturation (StO2) readings provided by different oximeters. To establish a comparability of oximeters, in our study we performed simultaneous measurements on the liquid phantom mimicking properties of neonatal heads and compared the tested device to a reference NIRS oximeter (OxiplexTS). We evaluated the NIRS oximeters FORE-SIGHT, NIRO and SenSmart, and reproduced previous results with the INVOS and OxyPrem v1.3 oximeters. In general, linear relationships of the StO2 values with respect to the reference were obtained. Device specific hypoxic and hyperoxic thresholds (as used in the SafeBoosC study, www.safeboosc.eu) and a table allowing for conversion of StO2 values are provided.

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.