Variation in perioperative cerebral and hemodynamic monitoring during carotid endarterectomy.

BACKGROUND: Hemodynamic disturbances cause half of the perioperative strokes following carotid endarterectomy (CEA). Guidelines strongly recommend strict pre- and postoperative blood pressure (BP) monitoring in CEA patients, but do not provide firm practical recommendations. Although in the Netherlands 50 centres perform CEA, no national protocol on perioperative hemodynamic, and cerebral monitoring exists. To assess current monitoring policies of all Dutch CEA-centres, a national survey was conducted. METHODS: Between May and July 2017 all 50 Dutch CEA-centres were invited to complete a 42-question survey addressing perioperative hemodynamic and cerebral monitoring during CEA. Nonresponders received a reminder after 1 and 2 months. By November 2017 the survey was completed by all centres. RESULTS: Preoperative baseline BP was based on a single bilateral BP-measurement at the outpatient-clinic in the majority of centres (n = 28). In 43 centres (86%) pre-operative monitoring (transcranial Doppler (TCD, n = 6), electroencephalography (EEG, n = 11), or TCD + EEG (n = 26)) was performed as a baseline reference. Intraoperatively, large diversity for type of anaesthesia (general: 45 vs. local [LA]:5) and target systolic BP (>100 mm hg - 160 mm hg [n = 12], based on preoperative outpatient-clinic or admission BP [n = 18], other [n = 20]) was reported. Intraoperative cerebral monitoring included EEG + TCD (n = 28), EEG alone (n = 13), clinical neurological examination with LA (n = 5), near-infrared spectroscopy with stump pressure (n = 1), and none due to standard shunting (n = 3). Postoperatively, significant variation was reported in standard duration of admission at a recovery or high-care unit (range 3-48 hr, mean:12 hr), maximum accepted systolic BP (range >100 mm hg - 180 mm Hg [n = 32]), postoperative cerebral monitoring (standard TCD [n = 16], TCD on indication [n = 5] or none [n = 24]) and in timing of postoperative cerebral monitoring (range directly postoperative - 24 hr postoperative; median 3 hr). CONCLUSIONS: In Dutch centres performing CEA the perioperative hemodynamic and cerebral monitoring policies are widely diverse. Diverse policies may theoretically lead to over- or under treatment. The results of this national audit may serve as the baseline dataset for development of a standardized and detailed (inter)national protocol on perioperative hemodynamic and cerebral monitoring during CEA.

Recent progress in development and applications of second near-infrared (NIR-II) nanoprobes.

Optical probes for near-infrared (NIR) light have clear advantages over UV/VIS-based optical probes, such as their low levels of interfering auto-fluorescence and high tissue penetration. The second NIR (NIR-II) window (1000-1350 nm) offers better light penetration, lower background signal, higher safety limit, and higher maximum permitted exposure than the first NIR (NIR-I) window (650-950 nm). Therefore, NIR-II laser-based photoacoustic (PA) and fluorescence (FL) imaging can offer higher sensitivity and penetration depth than was previously available, and deeper lesions can be treated in vivo by photothermal therapy (PTT) and photodynamic therapy (PDT) with an NIR-II laser than with an NIR-I laser. Advances in creation of novel nanomaterials have increased options for improving light-induced bioimaging and treatment. Nanotechnology can provide advantages such as good disease targeting ability and relatively long circulation times to supplement the advantages of optical technologies. In this review, we present recent progress in development and applications of NIR-II light-based nanoplatforms for FL, PA, image-guided surgery, PDT, and PTT. We also discuss recent advances in smart NIR-II nanoprobes that can respond to stimuli in the tumor microenvironment and inflamed sites. Finally, we consider the challenges involved in using NIR-II nanomedicine for effective diagnosis and treatment.

Near Infrared Spectroscopy Based Clinical Algorithm Applicability During Spinal Neurosurgery and Postoperative Cognitive Disturbances.

Background and Objectives: Postoperative cognitive disturbances (POCD) can significantly alter postoperative recovery. Inadequate intraoperative cerebral oxygen supply is one of the inciting causes of POCD. Near-infrared spectroscopy (NIRS) devices monitor cerebral oxygen saturation continuously and can help to guide intraoperative patient management. The aim of the study was to evaluate the applicability of the NIRS-based clinical algorithm during spinal neurosurgery and to find out whether it can influence postoperative cognitive performance. Materials and Methods: Thirty four patients scheduled for spinal neurosurgery were randomized into a study group (n = 23) and a control group (n = 11). We monitored regional cerebral oxygen saturation (rScO2) throughout surgery, using a NIRS device (INVOS 4100). If rScO2 dropped bilaterally or unilaterally by more than 20% from baseline values, or under an absolute value of 50%, the NIRS-based algorithm was initiated in the study group. In the control group, rScO2 was monitored blindly. To evaluate cognitive function, Montreal-Cognitive Assessment (MoCA) scale was used in both groups before and after the surgery. Results: In the study group, rScO2 dropped below the threshold in three patients and the NIRS-based algorithm was activated. Firstly, we verified correct positioning of the head; secondly, we increased mean systemic arterial pressure in the three patients by injecting repeated intravenous bolus doses of Ephedrine, ultimately resulting in an rScO2 increase above the approved threshold level. None of the three patients showed POCD. In the control group, one patient showed a drop in rScO2 of 34% from baseline and presented with a POCD. RScO2 drop occurred with other stable intraoperative measurements. Conclusions: A significant rScO2 drop may occur during spinal surgery in prone position despite other intraoperative measurements remaining stable, allowing it to stay otherwise unrecognized. Use of the NIRS-based clinical algorithm can help to avoid POCD in patients after spinal surgery.

Fluid Responsiveness After CArdiac Surgery (FRACAS): A Prospective Observational Study Using Peripheral Near-Infrared Spectroscopy.

OBJECTIVES: To describe tissue oxygen saturation (StO2) in response to a vascular occlusion test using thenar eminence and forearm near-infrared spectroscopy (NIRS) and the association with volume responsiveness after cardiac surgery. DESIGN: Single-center, prospective, observational cohort study. SETTING: Cardiothoracic intensive care unit. PARTICIPANTS: Seventy-six post-cardiac surgical adults. INTERVENTIONS: Immediately before and 10 minutes after a 250-to-500 mL fluid bolus, StO2 was measured in response to a vascular occlusion test to calculate tissue deoxygenation (Rdes) and reoxygenation (Rres) rates. Concurrently, systemic hemodynamic, metabolic, and blood gas variables were collected. MEASUREMENTS AND MAIN RESULTS: A total of 203 boluses were captured using thenar NIRS and 141 boluses using forearm NIRS. Approximately 25% of boluses increased cardiac output by ≥15% (volume responders). Thenar and forearm Rdes decreased in responders, but increased (thenar) or remained unchanged (forearm) in nonresponders. A logistic regression model of the association among StO2, Rdes and Rres, and volume responsiveness was significant for thenar measurements (p = 0.001) with an area under the receiver operating characteristic of 0.69 (95% confidence interval: 0.62-0.75). It also was significant (p = 0.02) for forearm measurements, with an area under the receiver operating characteristic of 0.71 (0.62-0.79). Rdes was an independent variable in both instances (odds ratio 0.31 [0.14-0.69], thenar; odds ratio 0.60 [0.45-0.80], forearm). Thenar and forearm NIRS variables were correlated poorly with cardiac output, stroke volume, systemic oxygen delivery and consumption index, mixed venous, and central venous oxygen saturation (Spearman׳s coefficients, r = 0.17-0.46, p < 0.002). CONCLUSION: In post-cardiac surgical patients, thenar and forearm NIRS variables were associated with volume responsiveness although not achieving precision necessary for clinical management.

Recent developments of imaging modalities of carotid artery stenting.

Compared with conventional angiogram-guided procedure, intravascular imaging modalities give us a lot of useful information to make the procedure better. Intravascular imaging modalities give us the information about lesion characters, reference vessel diameter and the interaction between the stent strut and the plaque such as stent strut malapposition or plaque prolapse in real time during the procedure. We can change our strategy according to this information. Intravascular ultrasound (IVUS) is a most common intravascular imaging modality during carotid artery stenting (CAS) in these days. Its advantage is easy to use compared with optical coherence tomograpy (OCT) which has been reported recently in some case reports or case series. However, due to its high resolution, OCT provides more detailed information especially about plaque prolapse and strut malapposition. IVUS and OCT have a potential to improve acute result and reduce the procedural complication by providing the data of lesion character, reference vessel diameter and the interaction of stent strut and vessel wall. Interventionalists who perform CAS procedure should acquire proficiency in imaging modalities during CAS procedure.

Near-Infrared Spectroscopy Hemoglobin Index Measurement During Fluid Challenge: A Prospective Study in Cardiac Surgery Patients.

OBJECTIVE: Little is known about changes in near-infrared spectroscopy-derived tissue hemoglobin index (HbI). The authors tested the hypothesis that absolute values and changes in brain hemoglobin index (HbIb) and skeletal muscle hemoglobin index (HbIm) could differ from the reference arterial hemoglobin (Hb) during fluid challenge. DESIGN: A prospective, monocenter observational study. SETTING: A 16-bed cardiac surgical intensive care unit in a teaching university hospital. PARTICIPANTS: Fifty consecutive adult patients. INTERVENTIONS: Investigation before and after a fluid challenge. MEASUREMENTS AND MAIN RESULTS: Simultaneous comparative Hb, HbIb and HbIm data points were collected from a blood-gas analyzer and the EQUANOX device (Nonin Medical Inc., Plymouth, MN). Correlations were determined by linear regression. No significant relationship was found between absolute values of Hb and HbIb before (R(2)= 0.04, p = 0.627) and after (R(2) = 0.00006, p = 0.956) fluid challenge. No significant relationship was found between absolute values of Hb and HbIm before (R(2)= 0.030, p = 0.226) and after (R(2) = 0.05, p = 0.117) the fluid challenge. No significant relationship was found between changes in Hb and HbIb (R(2)= 0.26, p = 0.263) and between changes in Hb and HbIm (R(2) = 0.001, p = 0.801) after the fluid challenge. Bland-Altman analysis showed a poor concordance between changes in Hb and HbIb, and changes in Hb and HbIm, with large limits of agreement. CONCLUSIONS: HbIb and HbIm cannot be used to provide continuous noninvasive estimation of Hb, and trends in HbIb and HbIm cannot be considered as noninvasive surrogates for the trend in Hb after cardiac surgery.

Changes in cerebral oxygen saturation following prone positioning for orthopaedic surgery under general anaesthesia: a prospective observational study.

BACKGROUND: Prone positioning is often necessary in orthopaedic surgery. The prone position, however, may result in impaired cerebral venous drainage with a subsequent reduction in cerebral perfusion. As a consequence, cerebral hypoxia may occur with the potential for neurological impairment. OBJECTIVE: We assessed the changes in cerebral oxygen saturation with near-infrared spectroscopy using two different monitors after positioning the patient from supine to prone. DESIGN: Prospective observational study. SETTING: Primary Care University Hospital, from May 2010 to February 2011. PARTICIPANTS: Forty patients undergoing general anaesthetic procedures, of which 35 completed the investigation. Similar measurements were done in 35 volunteers, who were studied while awake. INTERVENTIONS: Near-infrared spectroscopy was measured throughout anaesthesia using INVOS (a trend monitor using two infrared wavelengths) for one hemisphere and FORE-SIGHT (a monitor using four wavelengths of laser light to calculate absolute oxygen saturation) for the other hemisphere in an alternate randomisation pattern. OUTCOME MEASUREMENTS: The primary outcome was a change in cerebral oxygen saturation of more than 5% during prone positioning. A comparison with the changes obtained in awake volunteers following similar positioning was also made. RESULTS: Cerebral oxygen saturation increased during prone positioning with INVOS 0.032% per minute (P < 0.01) and with FORE-SIGHT 0.032% per minute (P < 0.01) in anaesthetised patients. Awake volunteers showed an increase of 0.171% per minute (INVOS) and 0.082% per minute (FORE-SIGHT) during prone positioning. Comparison of INVOS with FORE-SIGHT showed a good association, with a gradient of 0.80% per 1% change (P < 0.01). CONCLUSION: Both monitors detected a small increase in cerebral oxygen saturation of less than 5% in patients undergoing orthopaedic surgery in the prone position and in awake volunteers. This small increase is of limited clinical relevance and prone positioning may be regarded as safe in terms of the maintenance of cerebral oxygen saturation. TRIAL REGISTRATION: clinicaltrials.gov identifier: NCT01275898.

Current techniques for lymphatic imaging: State of the art and future perspectives.

Techniques for lymphatic imaging are aiming at accurate, simple and minimal-invasive approaches with less side-effects and repetitive application. Limitations are emerging in conventional techniques, and new techniques have shown their advantages in high resolution and sensitivity as well as transcutaneous imaging. In the present review, these techniques and their applications are reviewed and elucidated, aiming at a better understanding of recent advancements and current trends of lymphatic imaging as well as promising techniques for future research.

Monitoring tissue oxygenation by near infrared spectroscopy (NIRS): background and current applications.

Conventional cardiovascular monitoring may not detect tissue hypoxia, and conventional cardiovascular support aiming at global hemodynamics may not restore tissue oxygenation. NIRS offers non-invasive online monitoring of tissue oxygenation in a wide range of clinical scenarios. NIRS monitoring is commonly used to measure cerebral oxygenation (rSO(2)), e.g. during cardiac surgery. In this review, we will show that tissue hypoxia occurs frequently in the perioperative setting, particularly in cardiac surgery. Therefore, measuring and obtaining adequate tissue oxygenation may prevent (postoperative) complications and may thus be cost-effective. NIRS monitoring may also be used to detect tissue hypoxia in (prehospital) emergency settings, where it has prognostic significance and enables monitoring of therapeutic interventions, particularly in patients with trauma. However, optimal therapeutic agents and strategies for augmenting tissue oxygenation have yet to be determined.

Translation of near-infrared fluorescence imaging technologies: emerging clinical applications.

Technical developments in near-infrared fluorescence (NIRF) imaging and tomography have enabled recent translation into investigational human studies. Noninvasive imaging of the lymphatic vasculature for diagnosis and assessment of function has been uniquely accomplished with NIR using indocyanine green (ICG), a nonspecific dye that has comparatively poor fluorescent properties compared to emerging dyes. Adjunct use of NIRF-ICG for (a) intraoperative sentinel lymph node mapping for cancer staging, (b) video-angiography during surgery, and (c) discrimination of malignant from benign breast lesions detected by mammography and ultrasongraphy also evidences the clinical utility of NIRF. Future NIRF imaging agents that consist of bright fluorescent dyes conjugated to disease-targeting moieties promise molecular imaging and image-guided surgery. In this review, emerging NIRF imaging is described within the context of nuclear imaging technologies that remain the "gold standard" of molecular imaging.

The use of muscle near-infrared spectroscopy in sport, health and medical sciences: recent developments.

Near-infrared spectroscopy (NIRS) has been shown to be one of the tools that can measure oxygenation in muscle and other tissues in vivo. This review paper highlights the progress, specifically in this decade, that has been made for evaluating skeletal muscle oxygenation and oxidative energy metabolism in sport, health and clinical sciences. Development of NIRS technologies has focused on improving quantification of the signal using multiple wavelengths to solve for absorption and scattering coefficients, multiple pathlengths to correct for the influence of superficial skin and fat, and time-resolved and phase-modulated light sources to determine optical pathlengths. In addition, advances in optical imaging with multiple source and detector pairs as well as portability using small wireless detectors have expanded the usefulness of the devices. NIRS measurements have provided information on oxidative metabolism in various athletes during localized exercise and whole-body exercise, as well as training-induced adaptations. Furthermore, NIRS technology has been used in the study of a number of chronic health conditions. Future developments of NIRS technology will include enhancing signal quantification. In addition, advances in NIRS imaging and portability promise to transform how measurements of oxygen utilization are obtained in the future.

Diffuse optical imaging and spectroscopy for cancer.

Visible light and near infrared light interact with biological tissue by absorption and scattering. Diffuse optical imaging and spectroscopy reconstructs tissue physiologic parameters based on noninvasive measurement of tissue optical properties. This technology can be used to differentiate physiologic and molecular signatures of both malignant and benign tissues, as they relate to the area of cancer research. Major advantages are the use of non-ionizing radiation, real-time continuous data acquisition, low cost, and portability. Limitations include low spatial resolution and limited reproducibility. This paper reviews the currently available state-of-the-art technologies for diffuse optical imaging and spectroscopy and their applications in cancer research.

Impaired oxygen extraction in metabolic myopathies: detection and quantification by near-infrared spectroscopy.

Patients with mitochondrial myopathies (MM) or myophosphorylase deficiency (McArdle's disease, McA) show impaired capacity for O(2) extraction, low maximal aerobic power, and reduced exercise tolerance. Non-invasive tools are needed to quantify the metabolic impairment. Six patients with MM, 6 with McA, 25 with symptoms of metabolic myopathy but negative biopsy (patient-controls, P-CTRL) and 20 controls (CTRL) underwent an incremental cycloergometric test. Pulmonary O(2) uptake (VO(2)) and vastus lateralis oxygenation indices (by near-infrared spectroscopy, NIRS) were determined. Concentration changes of deoxygenated hemoglobin and myoglobin (Delta[deoxy(Hb + Mb)]) were considered an index of O(2) extraction. Delta[deoxy(Hb + Mb)] peak (percent limb ischemia) was lower in MM (25.3 +/- 12.0%) and McA (18.7 +/- 7.3) than in P-CTRL (62.4 +/- 3.9) and CTRL (71.3 +/- 3.9) subjects. VO(2) peak and Delta[deoxy(Hb + Mb)] peak were linearly related (r(2) = 0.83). In these patients, NIRS is a tool to detect and quantify non-invasively the metabolic impairment, which may be useful in the follow-up of patients and in the assessment of therapies and interventions.

Monitoring for neuroprotection. New technologies for the new millennium.

Monitoring for neuroprotection, like surgery, has placed on emphasis on minimal or non-invasiveness. Monitoring of parameters that truly reflect the degree of injury to the nervous system is another goal. Thus, two themes for the coming decade in neuromonitoring will be: (1) less-invasive monitoring; and (2) parameters that more closely reflect the etiological factors in ischemic or other neuroinjury. In this paper, we review neuromonitoring techniques and devices that can be used readily in the operating room or intensive care unit setting. Those that require transport of the patient to a special facility (e.g., for computed tomography or magnetic resonance imaging/spectroscopy) and those that have been in standard practice for neuromonitoring (e.g., electrophysiological monitoring--EEG, evoked potentials) are not considered. The two techniques considered in detail are (1) continuous multiparameter local brain tissue monitoring with microprobes, and (2) non-invasive continuous local brain tissue oxygenation monitoring by near infrared spectroscopy. Both techniques have been cleared by the Food and Drug Administration (FDA) for clinical use. The rationale for their use, the nature of the devices, and clinical results to date are reviewed. It is expected that both techniques will gain wide acceptance during the coming decade; further advances in neuromonitoring that can be expected further into the twenty-first century are also discussed.