Tissue Oxygen Monitoring Research Articles

Prognostic Value of Fluorine-19 MRI Oximetry Monitoring in cancer.

Hypoxia is a key prognostic indicator in most solid tumors, as it is correlated to tumor angiogenesis, metastasis, recurrence, and response to therapy. Accurate measurement and mapping of tumor oxygenation profile and changes upon intervention could facilitate disease progression assessment and assist in treatment planning. Currently, no gold standard exists for non-invasive spatiotemporal measurement of hypoxia. Magnetic resonance imaging (MRI) represents an attractive option as it is a clinically available and non-ionizing imaging modality. Specifically, perfluorocarbon (PFC) beacons can be externally introduced into the tumor tissue and the linear dependence of their spin-lattice relaxation rate (R1) on the local partial pressure of oxygen (pO2) exploited for real-time tissue oxygenation monitoring in vivo. In this review, we will focus on early studies and recent developments of fluorine-19 MRI and spectroscopy (MRS) for evaluation of tumor oximetry and response to therapy.

MITOCHONDRIAL OXYGENATION DURING CARDIOPULMONARY BYPASS: A PILOT STUDY

Introduction Cardiopulmonary bypass (CPB) is used during cardiac-surgery and provides oxygenated blood to the tissues. Ensuring adequate oxygenation is essential for the preservation of organ function during CPB. Both hypoxia and hyperoxia result in undesired outcomes and a narrow window for optimal oxygenation exists. Current perioperative monitoring techniques are not always sufficient to monitor adequate oxygenation, especially in high-risk patients. Near-infrared spectroscopy (NIRS) tissue oxygen measurement (StO2) is widely used to monitor tissue oxygenation but responds slowly to change. However, the novel non-invasive COMET-monitor measures the mitochondrial oxygen tension (mitoPO2) in the epidermis using the enhanced mitochondrial Protoporphyrin IX Triplet State Lifetime Technique (PpIX-TSLT). The mitoPO2 reflects the local balance between oxygen supply and consumption and provides an insight into the microcirculatory system [1]. This pilot study investigates the correlation between mitoPO2 versus StO2 and varying hemodynamic conditions during CPB and the development of acute kidney injury (AKI). Methods This single center observational study examined 41 cardiac-surgery patients requiring CPB. Six-hours pre-operatively, patients received a 5-aminolevulinc acid plaster on the upper arm to facilitate the mitoPO2 measurements. After induction of anesthesia, both the COMET and INVOS measurements were executed in 5-minute intervals throughout the procedure. To compare mitoPO2 with StO2, NIRS probes were placed near the COMET probe. Post-operatively, both measurements were stopped simultaneously, and the patients were observed until discharge for the development of AKI. Results NIRS data was available for 31 of the 41 patients. The median mitoPO2 at the start of surgery was 63.5 [40.0 – 74.8] mmHg and significantly decreased (p Discussion In contrast to StO2, the mitoPO2 decreased significantly during CPB time. A hemodilution study in pigs also demonstrated that mitoPO¬2 is more likely to change than StO2, which reacted slowly to change. The mitoPO2 also significantly decreased during non-pulsatile flow and increased once pulsatile flow returned, whilst the StO2 did not. This highlights the sensitivity of mitoPO2 to detect circulatory and microvascular changes early through the analysis of oxygen delivery on a cellular level. Lastly, the association found between the AKI and the non-AKI group in time spent below a mitoPO2 of 20 mmHg must be further examined in a well powered study. However, it highlights the potential of this technique to be an early predictor of ischemia.

The relationship between renal oxygen saturation and renal function in patients with and without diabetes following coronary artery bypass grafting surgery

Background/Aim: Acute kidney injury may occur due to renal ischemia and hypoxia during coronary artery bypass surgery. Monitoring of renal regional tissue oxygenation might be useful to determine renal hypoxia. We aimed to investigate whether renal oxygen saturation values differ between diabetic and non-diabetic patients and evaluate the relationship between intra-operative renal oxygen saturation values and postoperative renal function. Methods: Forty consecutive patients aged 18-65 years, who underwent elective coronary artery bypass grafting, were included in this prospective case-control study. Body mass index ≥30 kg/m2 and the presence of renal damage were considered the exclusion criteria. Group I consisted of diabetic patients (n = 20), and Group II consisted of non-diabetic patients (n = 20). Near Infrared Spectroscopy (NIRS) recorded renal saturation values just before the intubation as the basal value and every 10 minutes after intubation in all patients. Creatinine clearances and glomerular filtration rates were calculated along with blood urea nitrogen and creatinine values on the postoperative 1st and 3rd days of all patients. Results: The two groups were similar in terms of gender, age, body mass index, duration of surgery, cross-clamp time, and total cardiopulmonary bypass duration (P>0.05). While there was no difference between baseline values, significant differences were found between preoperative BUN and creatinine and POD 3 BUN and creatinine values in Group 1 (P=0.003 and P=0.046, respectively) and Group 2 (P=0.018 and P=0.030, respectively). There was no significant difference between two groups in renal oxygen saturation values considering both basal and post-intubation measurements (P>0.05 for all). However, an earlier decrease in renal oxygen saturation values was seen in diabetic patients (P 0.05 for all). Conclusion: Although coronary artery graft bypass surgery does not lead to a significant difference in renal saturation values, as determined by Near Infrared Spectroscopy, in diabetic patients compared to non-diabetic patients, NIRS may be helpful and beneficial to show renal ischemia in these patients.

Post-Operative Monitoring of Intestinal Tissue Oxygenation Using an Implantable Microfabricated Oxygen Sensor.

Anastomotic leakage (AL) is a common and dangerous post-operative complication following intestinal resection, causing substantial morbidity and mortality. Ischaemia in the tissue surrounding the anastomosis is a major risk-factor for AL development. Continuous tissue oxygenation monitoring during the post-operative recovery period would provide early and accurate early identification of AL risk. We describe the construction and testing of a miniature implantable electrochemical oxygen sensor that addresses this need. It consisted of an array of platinum microelectrodes, microfabricated on a silicon substrate, with a poly(2-hydroxyethyl methacrylate) hydrogel membrane to protect the sensor surface. The sensor was encapsulated in a biocompatible package with a wired connection to external instrumentation. It gave a sensitive and highly linear response to variations in oxygen partial pressure in vitro, although over time its sensitivity was partially decreased by protein biofouling. Using a pre-clinical in vivo pig model, acute intestinal ischaemia was robustly and accurately detected by the sensor. Graded changes in tissue oxygenation were also measurable, with relative differences detected more accurately than absolute differences. Finally, we demonstrated its suitability for continuous monitoring of tissue oxygenation at a colorectal anastomosis over a period of at least 45 h. This study provides evidence to support the development and use of implantable electrochemical oxygen sensors for post-operative monitoring of anastomosis oxygenation.

The use of near-infrared spectroscopy in the diagnosis of peripheral artery disease: A systematic review.

Peripheral arterial disease is a stenosis or occlusion of peripheral arteries that results in compromised blood flow and muscle ischemia. The available diagnostic methods are mostly used to measure and visualize blood flow and are not useful in the evaluation of perfusion, especially in diabetic patients, which is now considered to be a research priority by most of the vascular societies around the world as this is still a relatively poorly studied phenomenon. The aim of this review is to explore the clinical significance of muscle tissue oxygenation monitoring in lower-extremity peripheral artery disease diagnosis using the near-infrared spectroscopy method. A systematic search in PubMed, CINAHL, and Cochrane databases was performed to identify clinical near-infrared spectroscopy (NIRS) studies in English and Russian, published until September 2019, involving muscle tissue oxygenation in peripheral arterial disease (PAD). The manuscripts were reviewed by two researchers independently and scored on the quality of the research using MINORS criteria. After screening 443 manuscripts, 23 studies (n = 1580) were included. NIRS-evaluated recovery time seems to be more accurate than ankle-brachial index in diabetic patients to differentiate between moderate and severe claudication. Consistent findings across all the included studies showed that both the oxygenation and deoxygenation rates as well as the recovery times varied from patient to patient and therefore were not suitable for standardization. The clinical relevance of routine use of NIRS to diagnose PAD is unproven; therefore, its use is not currently part of standard-of-care for patients with PAD since the absolute values seem to vary significantly, depending on the outside conditions. More data need to be provided on the possible use of NIRS monitoring intraoperatively where the conditions can be more controlled.

Outcomes associated with brain tissue oxygen monitoring in patients with severe traumatic brain injury undergoing intracranial pressure monitoring.

Brain tissue oxygen monitoring combined with intracranial pressure (ICP) monitoring in patients with severe traumatic brain injury (sTBI) may confer better outcomes than ICP monitoring alone. The authors sought to investigate this using a national database. The National Trauma Data Bank from 2013 to 2017 was queried to identify patients with sTBI who had an external ventricular drain or intraparenchymal ICP monitor placed. Patients were stratified according to the placement of an intraparenchymal brain tissue oxygen tension (PbtO2) monitor, and a 2:1 propensity score matching pair was used to compare outcomes in patients with and those without PbtO2 monitoring. Sensitivity analyses were performed using the entire cohort, and each model was adjusted for age, sex, Glasgow Coma Scale score, Injury Severity Score, presence of hypotension, insurance, race, and hospital teaching status. The primary outcome of interest was in-hospital mortality, and secondary outcomes included ICU length of stay (LOS) and overall LOS. A total of 3421 patients with sTBI who underwent ICP monitoring were identified. Of these, 155 (4.5%) patients had a PbtO2 monitor placed. Among the propensity score-matched patients, mortality occurred in 35.4% of patients without oxygen monitoring and 23.4% of patients with oxygen monitoring (OR 0.53, 95% CI 0.33-0.85; p = 0.007). The unfavorable discharge rates were 56.3% and 47.4%, respectively, in patients with and those without oxygen monitoring (OR 1.41, 95% CI 0.87-2.30; p = 0.168). There was no difference in overall LOS, but patients with PbtO2 monitoring had a significantly longer ICU LOS and duration of mechanical ventilation. In the sensitivity analysis, PbtO2 monitoring was associated with decreased odds of mortality (OR 0.56, 95% CI 0.37-0.84) but higher odds of unfavorable discharge (OR 1.59, 95% CI 1.06-2.40). When combined with ICP monitoring, PbtO2 monitoring was associated with lower inpatient mortality for patients with sTBI. This supports the findings of the recent Brain Oxygen Optimization in Severe Traumatic Brain Injury phase 2 (BOOST 2) trial and highlights the importance of the ongoing BOOST3 trial.

Near-Infrared Spectroscopy Assessment of Tissue Oxygenation During Selective Cerebral Perfusion for Neonatal Aortic Arch Reconstruction.

Objective: Optimal selective cerebral perfusion (SCP) management for neonatal aortic arch surgery has not been extensively studied. We induced mild hypothermia during SCP and used the tissue oxygenation monitor to ensure adequate perfusion during the cardiopulmonary bypass (CPB).Methods: Eight cases were recruited from September 2018 to April 2020. SCP was maintained at 30°C, and CPB was adjusted to achieve a mean right radial artery pressure of 30 mmHg. The near-infrared tissue saturation (NIRS) monitor was applied to assess the right and left brain, flank, and lower extremity during the surgery.Results: During surgery, the mean age was 4.75 days, the mean body weight was 2.92 kg, the CPB duration was 86.5 ±18.7 min, the aortic cross-clamp time was 46.1 ± 12.7 min, and the SCP duration was 14.6±3.4 min. The brain NIRS before, during, and after SCP was 64.2, 67.2, and 71.5 on the left side and 67.9, 66.2, and 70.1 on the right side (p = NS), respectively. However, renal and lower extremity tissue oxygenation, respectively decreased from 61.6 and 62.4 before SCP to 37.7 and 39.9 after SCP (p < 0.05) and then increased to 70.1 and 90.4 after full body flow resumed. No stroke was reported postoperatively.Conclusion: SCP under mild hypothermia can aid in efficient maintenance of brain perfusion during neonatal arch reconstruction. The clinical outcome of this strategy was favorable for up to 20 min, but the safety duration of lower body ischemia warrants further analysis.

Cerebrovascular pressure reactivity and intracranial pressure are associated with neurologic outcome after hypoxic-ischemic brain injury

AimWe evaluated the association of physiological parameters measured by intracranial multimodality neuromonitoring with neurologic outcome in a consecutive series of patients with hypoxic-ischemic brain injury (HIBI). MethodsWe retrospectively identified all patients with HIBI who underwent combined invasive intracranial pressure (ICP) and brain tissue oxygen (PbtO2) monitoring over a 3 year period. Cerebrovascular pressure reactivity index (PRx) was calculated continuously as a surrogate of cerebral autoregulation. Favorable outcome was defined as recovery of consciousness (Glasgow Coma Scale motor score = 6). Differences in mean ICP, PRx and PbtO2 for the entire monitoring period across outcomes were measured. Logistic regression and area under receiver operating characteristic (AUROC) curve were used to assess the association of each monitoring parameter with neurologic outcome. ResultsWe analyzed data from 36 patients. Most (89%) had an antecedent sudden cardiac arrest. Favorable outcome occurred in 8 (22%) patients. ICP and PRx were higher in patients with unfavorable outcome (ICP: 26 ± 4.1 mmHg vs 7.5 ± 2 mmHg, p = 0.0002; PRx: 0.51 ± 0.05 vs 0.11 ± 0.05, p < 0.0001). There was no significant difference in PbtO2 between groups (unfavorable: 20 ± 2.4 mmHg vs favorable: 25 ± 1.5 mmHg, p = 0.12). Both ICP (AUROC 0.84, 95%CI 0.72–0.98, p = 0.003) and PRx (AUROC 0.94, 95%CI 0.85–1, p = 0.0002) discriminated between favorable and unfavorable outcome, in contrast to PbtO2, (AUROC 0.59, 95%CI 0.39–0.78, p = 0.52). ICP > 15 mmHg, PRx > 0.2, and PbtO2 < 18 mmHg had sensitivity/specificity of 68%/100%, 89%/88%, and 40%/100% respectively for discriminating outcomes. ConclusionCerebrovascular pressure reactivity and intracranial pressure appear to be associated with neurologic outcome in patients with HIBI.

Comparison of renal region, cerebral and peripheral oxygenation for predicting postoperative renal impairment after CABG

Patients undergoing coronary artery bypass grafting (CABG) are at risk of developing postoperative renal impairment, amongst others caused by renal ischemia and hypoxia. Intra-operative monitoring of renal region tissue oxygenation (SrtO2) might be a useful tool to detect renal hypoxia and predict postoperative renal impairment. Therefore, the aim of this study was to assess the ability of intra-operative SrtO2 to predict postoperative renal impairment, defined as an increase of serum creatinine concentrations of > 10% from individual baseline, and compare this with the predictive abilities of peripheral and cerebral tissue oxygenation (SptO2 and SctO2, respectively) and renal specific tissue deoxygenation. Forty-one patients undergoing elective CABG were included. Near-infrared spectroscopy (NIRS) was used to measure renal region, peripheral (thenar muscle) and cerebral tissue oxygenation during surgery. Renal region specific tissue deoxygenation was defined as a proportionally larger decrease in SrtO2 than SptO2. ROC analyses were used to compare predictive abilities. We did not observe an association between tissue oxygenation measured in the renal region and cerebral oxygenation and postoperative renal impairment in this small retrospective study. In contrast, SptO2 decrease > 10% from baseline was a reasonable predictor with an AUROC of 0.767 (95%CI 0.619 to 0.14; p = 0.010). Tissue oxygenation of the renal region, although non-invasively and continuously available, cannot be used in adults to predict postoperative renal impairment after CABG. Instead, peripheral tissue deoxygenation was able to predict postoperative renal impairment, suggesting that SptO2 provides a better indication of ‘general’ tissue oxygenation status.Registered at ClinicalTrials.gov: NCT01347827, first submitted April 27, 2011.

Monitoring deep-tissue oxygenation with a millimeter-scale ultrasonic implant.

Vascular complications following solid organ transplantation may lead to graft ischemia, dysfunction or loss. Imaging approaches can provide intermittent assessments of graft perfusion, but require highly skilled practitioners and do not directly assess graft oxygenation. Existing systems for monitoring tissue oxygenation are limited by the need for wired connections, the inability to provide real-time data or operation restricted to surface tissues. Here, we present a minimally invasive system to monitor deep-tissue O2 that reports continuous real-time data from centimeter-scale depths in sheep and up to a 10-cm depth in ex vivo porcine tissue. The system is composed of a millimeter-sized, wireless, ultrasound-powered implantable luminescence O2 sensor and an external transceiver for bidirectional data transfer, enabling deep-tissue oxygenation monitoring for surgical or critical care indications.

Neurologic Assessment of the Neurocritical Care Patient.

Sedation is a ubiquitous practice in ICUs and NCCUs. It has the benefit of reducing cerebral energy demands, but also precludes an accurate neurologic assessment. Because of this, sedation is intermittently stopped for the purposes of a neurologic assessment, which is termed a neurologic wake-up test (NWT). NWTs are considered to be the gold-standard in continued assessment of brain-injured patients under sedation. NWTs also produce an acute stress response that is accompanied by elevations in blood pressure, respiratory rate, heart rate, and ICP. Utilization of cerebral microdialysis and brain tissue oxygen monitoring in small cohorts of brain-injured patients suggests that this is not mirrored by alterations in cerebral metabolism, and seldom affects oxygenation. The hard contraindications for the NWT are preexisting intracranial hypertension, barbiturate treatment, status epilepticus, and hyperthermia. However, hemodynamic instability, sedative use for primary ICP control, and sedative use for severe agitation or respiratory distress are considered significant safety concerns. Despite ubiquitous recommendation, it is not clear if additional clinically relevant information is gleaned through its use, especially with the contemporaneous utilization of multimodality monitoring. Various monitoring modalities provide unique and pertinent information about neurologic function, however, their role in improving patient outcomes and guiding treatment plans has not been fully elucidated. There is a paucity of information pertaining to the optimal frequency of NWTs, and if it differs based on type of injury. Only one concrete recommendation was found in the literature, exemplifying the uncertainty surrounding its utility. The most common sedative used and recommended is propofol because of its rapid onset, short duration, and reduction of cerebral energy requirements. Dexmedetomidine may be employed to facilitate serial NWTs, and should always be used in the non-intubated patient or if propofol infusion syndrome (PRIS) develops. Midazolam is not recommended due to tissue accumulation and residual sedation confounding a reliable NWT. Thus, NWTs are well-tolerated in selected patients and remain recommended as the gold-standard for continued neuromonitoring. Predicated upon one expert panel, they should be performed at least one time per day. Propofol or dexmedetomidine are the main sedative choices, both enabling a rapid awakening and consistent NWT.

Monitoring tissue oxygenation index using near\u2010infrared spectroscopy during pre\u2010hospital resuscitation among out\u2010of\u2010hospital cardiac arrest patients: a pilot study

BackgroundTissue oxygenation index (TOI) using the near infrared spectroscopy (NIRS) has been demonstrated as a useful indicator to predict return of spontaneous circulation (ROSC) among out-of-hospital cardiac arrest (OHCA) patients in hospital setting. However, it has not been widely examined based on pre-hospital setting.MethodsIn this prospective observational study, we measured TOI in pre-hospital setting among OHCA patients receiving cardio-pulmonary resuscitation (CPR) during ambulance transportation between 2017 and 2018. Throughout the pre-hospital CPR procedure, TOI was continuously measured. The study population was divided into two subgroups: ROSC group and non-ROSC group.ResultsOf the 81 patients included in the final analysis, 26 achieved ROSC and 55 did not achieve ROSC. Patients in the ROSC group were significantly younger, had higher ∆TOI (changes in TOI) (5.8 % vs. 1.3 %; p < 0.01), and were more likely to have shockable rhythms and event witnessed than patients in the non-ROSC group. ∆TOI cut-off value of 5 % had highest sensitivity (65.4 %) and specificity (89.3 %) for ROSC. Patients with a cut-off value ≤-2.0 % did not achieve ROSC and while all OHCA patient with a cut-off value ≥ 8.0 % achieved ROSC. In addition, ROSC group had stronger positive correlation between mean chest compression rate and ∆TOI (r = 0.82) than non-ROSC group (r = 0.50).ConclusionsThis study suggests that ∆ TOI could be a useful indicator to predict ROSC in a pre-hospital setting.

Near-Infrared Spectroscopy in Extremely Preterm Infants.

With advances in neonatal care, survival of premature infants at the limits of viability has improved significantly. Despite these improvement in mortality, infants born at 22–24 weeks gestation are at a very high risk for short- and long-term morbidities associated with prematurity. Many of these diseases have been attributed to abnormalities of tissue oxygenation and perfusion. Near-infrared spectroscopy utilizes the unique absorption properties of oxyhemoglobin and deoxyhemoglobin to provide an assessment of regional tissue oxygen saturation, which can be used to calculate the fractional tissue oxygen extraction. This allows for a non-invasive way to monitor tissue oxygen consumption and enables targeted hemodynamic management. This mini-review provides a brief and complete overview of the background and physiology of near-infrared spectroscopy, practical use in extremely preterm infants, and potential applications in the neonatal intensive care unit. In this mini-review, we aim to summarize the three primary application sites for near-infrared spectroscopy, disease-specific indications, and available literature regarding use in extremely preterm infants.

The Effects of Endotracheal Suctioning on Hemodynamic Parameters and Tissue Oxygenation in Pediatric Intensive Care Unit.

Airway secretions may increase in intubated patients due to the impaired mucociliary clearance, impaired cough reflex, abnormal glottic function, insufficient moisturizing, and respiratory tract infections. As with any intervention, patients should be cautiously monitored for possible complications during the endotracheal suctioning. Procedure-related changes in the cerebral and somatic tissue oxygenation, hemodynamics, and oxygen saturation can be observed in these patients. It is important to ensure maintenance of tissue oxygenation during these and other interventions performed in critically ill children. The aim of this study was to investigate the effects of the endotracheal suctioning on tissue oxygenation in patients undergoing mechanical ventilation in the pediatric intensive care unit. Cerebral and somatic near-infrared spectroscopy (NIRS) monitoring were performed noninvasively using standardized NIRS equipment as a means of monitoring regional tissue oxygenation. Vital signs, level of sedation, pain scores, and somatic and cerebral tissue oxygenation values of mechanically ventilated patients were recorded prospectively 5 minutes before, during, and after endotracheal suctioning. Cerebral NIRS measurements did not exhibit any statistically significant changes during endotracheal suctioning. Somatic NIRS levels changed significantly before, during, and after endotracheal suctioning and remained low throughout the procedure. Endotracheal suctioning is an invasive intervention that facilitates clearance of tracheal secretions and maintenance of the oxygenation and ventilation. The maintenance of the tissue oxygenation should be documented during these and other interventions performed on critically ill children. Somatic NIRS is a useful tool for monitoring tissue oxygenation during such procedures.

Non-invasive continuous renal tissue oxygenation monitoring to identify preterm neonates at risk for acute kidney injury.

Near-infrared spectroscopy (NIRS) is an emerging tool to identify signs of inadequate tissue oxygenation in preterm neonates with acute kidney injury (AKI). Previous studies have shown a correlation between low renal tissue oxygenation (RrSO2) in the first 24hours of age and the later development of AKI. In this prospective clinical trial, NIRS monitoring was used to identify changes in RrSO2 in comparison to traditional AKI markers, serum creatinine (SCr), and urine output (UOP). We enrolled 35 preterm neonates born less than 32weeks' gestation and applied neonatal NIRS sensors at less than 48hours of age. Neonates underwent 7days of continuous monitoring. Renal and demographic information were collected for the first 7days of age. AKI was determined by the modified neonatal Kidney Disease: Improving Global Outcomes (KDIGO) definition including UOP. Three patients experienced AKI, all based on both SCr and UOP criteria. Each neonate with AKI had decreases in RrSO2 over 48hours prior to changes in SCr and UOP. Patients with AKI had lower median RrSO2 values compared to patients without AKI over the first week of age, (32.4% vs. 60%, p < 0.001). RrSO2 monitoring identified preterm neonates at risk for AKI. NIRS detected a decline in RrSO2 prior to changes in SCr and UOP and was significantly lower in patients with AKI compared to those without AKI. Further studies are needed to evaluate the ability of RrSO2 monitoring to detect signs of kidney stress prior to the diagnosis of AKI. Graphical abstract.

Bladder urine oxygen partial pressure monitoring: Could it be a tool for early detection of acute kidney injury?

ABSTRACT Acute kidney injury (AKI) necessitating renal-replacement therapy has been associated with high mortality rates in critically ill patients. Usual methods to study AKI encompass the assessment of serum and urine biomarkers. Hypoxia is a major pathophysiological feature of AKI, which necessitates continuous bedside monitoring of renal tissue oxygenation in intensive care unit (ICU) patients. Research has made continuous bladder urine oxygen pressure (PuO2) monitoring possible in humans. Although the value of bladder PuO2 does not represent an absolute value of medullary tissue oxygen pressure (Po2), bladder PuO2 can be considered a window into the renal medullary oxygenation. Bladder PuO2 can be monitored by using probes with oxygen sensors inserted into the urinary bladder. Additionally, PuO2 can be measured manually by using a blood gas analyzer machine. PuO2 monitoring can be potentially helpful in early diagnosis and/or prevention of AKI and guide therapeutic interventions aimed at improving renal oxygen delivery in those patients.

Evaluation of immediate complications and 10-years neurological outcomes in patients after reconstructive interventions on the ascending aorta and the aortic arch

OBJECTIVE To estimate the frequency of early postoperative neurological complications in patients undergoing planned surgery on the ascending aortic and arch of the aorta, and their long-term outcomes. MATERIAL AND METHODS The prospective study included 100 patients who were operated on at the FSBSI Petrovsky Russian Research Center of Surgery. In group I (n=50), operations were performed on the aortic arch with hypothermic circulatory arrest (26 °C) and antegrade cerebral perfusion. Patients in group II underwent prosthetics of the ascending aorta with extracorporeal circulation and moderate hypothermia (32 °C). All patients underwent monitoring of cerebral and tissue oxygenation, transcranial Doppler and testing of cognitive functions before and after surgery, and after 5 and 10 years of follow-up. RESULTS Postoperative stroke in group I was observed in 1 (2%) patient, no cases were observed in group II. Delirium was detected in 14% of patients in group I and 6% of patients in group II, its subsyndromal form was found in 6 and 4%, respectively. Moderate cognitive impairment in the immediate postoperative period was found in 42 and 26%; severe in 8% of group I. After 5 years of follow-up, the number of patients with moderate and severe cognitive impairment was 23.1 and 12.8%, respectively. After 10 years, severe disorders were identified in 37.5 and 21.9% of patients. CONCLUSION In cardiac surgery patients, intraoperative multimodal monitoring allows dynamic regulation of antegrade cerebral perfusion. Dynamic testing of cognitive functions and early detection of delirium in the immediate postoperative period improve long-term neurological treatment outcomes.

Use of Direct Intracranial Pressure and Brain Tissue Oxygen Monitoring in Perioperative Management of Patients with Moyamoya Disease.

Intracranial pressure monitoring and brain tissue oxygen monitoring are commonly used in head injury for goal-directed therapies, but there may be more indications for its use. Moyamoya disease involves progressive stenosis of the arterial circulation and formation of collateral vessels that are at risk of hemorrhage. The risk of ischemic events during revascularization surgery and postoperatively is high. Impaired cerebral autoregulation may be one of the factors that are implicated. We present our experience with monitoring of cerebral oxygenation and autoregulation in the pathological hemisphere during the perioperative period in four patients with moyamoya disease.

Developing a Wearable Sensor for Continuous Tissue Oxygenation Monitoring: A Proof of Concept Study

Abstract Objective Technologies facilitating continuous free tissue flap monitoring such as near infrared spectroscopy (NIRS) have been shown to improve flap salvage rates. However, the size and associated costs of such technology create a barrier to wider implementation. The aim of this study was to develop and validate a wearable sensor for continuous tissue oxygenation monitoring. Materials and Methods A forearm ischemia model was designed by using a brachial pressure cuff inflation protocol. Twenty healthy subjects were recruited. The forearm tissue oxygenation of each subject was monitored throughout the pressure cuff protocol by using a new optical sensor (Imperial College London), and a gold standard tissue spectrometry system (O2C, Medizintecknik, LEA, Germany). Data were processed to allow quantitative deoxygenation episode comparisons between inflations and sensor modalities. Results The correlation between O2C and optical sensor oxygenation measurements was moderate (average R = 0.672, p &lt; 0.001). Incremental increases in cuff inflation duration resulted in a linear increase in deoxygenation values with both O2C and optical sensors, with significant differences recorded on consecutive inflations (wall shear rate, p &lt; 0.005). The presence or absence of pulsatile blood flow was correctly determined throughout by both sensor modalities. Conclusion This study demonstrates the ability of a small optical sensor to detect and quantify tissue oxygenation changes and assess the presence of pulsatile blood flow. Low power, miniaturized electronics make the device capable of deployment in a wearable form which may break down the barriers for implementation in postoperative flap monitoring.

How do we identify the crashing traumatic brain injury patient - the neurosurgeon's view.

To provide an overview on recent advances in the field of assessment and monitoring of patients with severe traumatic brain injury (sTBI) in neurocritical care from a neurosurgical point of view. In high-income countries, monitoring of patients with sTBI heavily relies on multimodal neurocritical parameters, nonetheless clinical assessment still has a solid role in decision-making. There are guidelines and consensus-based treatment algorithms that can be employed in both absence and presence of multimodal monitoring in the management of patients with sTBI. Additionally, novel dynamic monitoring options and machine learning-based prognostic models are introduced. Currently, the acute management and treatment of secondary injury/insults is focused on dealing with the objective evident pathology. An ongoing paradigm shift is emerging towards more proactive treatment of neuroworsening as soon as premonitory signs of deterioration are detected. Based on the current evidence, serial clinical assessment, neuroimaging, intracranial and cerebral perfusion pressure and brain tissue oxygen monitoring are key components of sTBI care. Clinical assessment has a crucial role in identifying the crashing patient with sTBI, especially from a neurosurgical standpoint. Multimodal monitoring and clinical assessment should be seen as complementary evaluation methods that support one another.