The Effects of Silicone Enclosure Colour on the Function of Optical Sensors

Simple Summary

Implantable optical sensing is a rapidly growing field that allows for continuous monitoring of internal organs’ physiological states. Near-infrared spectroscopy is an optical sensing technology allowing for low-cost, non-invasive, high-sensitivity measurement of tissue oxygenation and haemodynamic parameters. The colour of an optical sensor’s enclosure affects the sensor’s sensitivity, function, and ability to detect tissue vital signs. This study compared the optical properties of coloured silicone materials and related these properties to the function of silicone enclosed implantable near-infrared spectroscopy sensors. We demonstrated that sensor enclosures highly reflective to red and near-infrared light facilitated light propagation to the photodetector and increased the ability to detect the effects of cardiac pulsation and respiratory rhythm on tissue haemodynamics. In contrast, highly absorptive sensor enclosures resulted in better detection and monitoring of tissue oxygenation.

Abstract

The colour of the silicone enclosure of an implantable reflectance-based optical probe plays a critical role in sensor performance. Red-coloured probes that are highly reflective to near-infrared light have been found to increase photodetector power by a factor of 6 for wavelengths between 660 and 950 nm and triple the magnitude of measured cardiac pulsations compared to traditional black probes. The increase in photodetector power and cardiac pulsation magnitude is presumably due to increased spatial range resulting from a higher magnitude of superficial tissue scattering. Conversely, probes with highly absorbent colours such as black and blue result in more stable signals and are expected to have higher spatial resolution and depth of penetration.

Can real-time near-infrared spectroscopy monitoring detect graft venous thrombosis after pediatric kidney transplantation?

BACKGROUND

A prompt detection of graft venous thrombosis might preserve the transplanted organ. A real-time near-infrared spectroscopy (NIRS) monitoring of the allograft perfusion could fulfill this goal. The aim of this work was to report the trend of allograft perfusion (rSO2) after pediatric kidney transplantation (KT) complicated by graft venous thrombosis.

CASE PRESENTATION

An infant, affected by end-stage kidney disease due to posterior urethral valves, underwent non-living donor KT. The allograft presented both arterial and venous variants and required a complex bench surgery reconstruction. The perfusion of the allograft was monitored by real-time transcutaneous NIRS. The early post-operative was conditioned by worsening clinical conditions, and a graft venous thrombosis was detected after four hours since the transplantation. NIRS monitoring lasted for 348 minutes. Median lower pole rSO2-value was 65% (IQR 62-66%), while the median upper pole rSO2-value was 70% (IQR 70-71%). These data reflected the congestion of the lower pole, observed at the end of the transplantation. The lower pole showed inferior rSO2 values (p<0.0001). At the end of the monitoring, the decrease in peripheral rSO2, measured in left lower limb as a benchmark, was consistent with the ongoing hypovolemic shock and severe acute anemia.

CONCLUSION

Transcutaneous NIRS might be a reliable device for monitoring allograft and peripheric perfusion after pediatric KT. The modifications of rSO2 values helped the clinicians manage the patients in the post-operative and early detect acute complications.

Application of Controlled Hypotension During Surgery for Spinal Metastasis

With advances in tumor treatment, metastasis to bone is increasing, and surgery has become the only choice for most terminal patients. However, spinal surgery has a high risk and is prone to heavy bleeding. Controlled hypotension during surgery has outstanding advantages in reducing intraoperative bleeding and ensuring a clear field of vision, thus avoiding damage to important nerves and vessels. Antihypertensive drugs should be carefully selected after considering the patient's age, different diseases, etc, and a single or combined regimen can be used. Hypotension also inevitably leads to a decrease in perfusion of important organs, so the threshold of hypotension and the maintenance time of hypotension should be strictly limited, and the monitoring of important organs during the operation is particularly important. Information such as blood perfusion, blood oxygen saturation, cardiac output, and neurophysiological conduction potential changes should be obtained in a timely fashion, which will help to reduce the risk of hypotension. In short, when applying controlled hypotension, it is necessary to choose an appropriate threshold and duration, and appropriate monitoring should be conducted during the operation to ensure the safety of the patient.

The Application of Nanoparticles in Diagnosis and Treatment of Kidney Diseases

Nanomedicine is currently showing great promise for new methods of diagnosing and treating many diseases, particularly in kidney disease and transplantation. The unique properties of nanoparticles arise from the diversity of size effects, used to design targeted nanoparticles for specific cells or tissues, taking renal clearance and tubular secretion mechanisms into account. The design of surface particles on nanoparticles offers a wide range of possibilities, among which antibodies play an important role. Nanoparticles find applications in encapsulated drug delivery systems containing immunosuppressants and other drugs, in imaging, gene therapies and many other branches of medicine. They have the potential to revolutionize kidney transplantation by reducing and preventing ischemia-reperfusion injury, more efficiently delivering drugs to the graft site while avoiding systemic effects, accurately localizing and visualising the diseased site and enabling continuous monitoring of graft function. So far, there are known nanoparticles with no toxic effects on human tissue, although further studies are still needed to confirm their safety.

Perioperative anesthesia care for the pediatric patient undergoing a kidney transplantation: An educational review

Living-donor kidney transplantation is the first choice therapy for children with end-stage renal disease and shows good long-term outcome. Etiology of renal failure, co-morbidities, and hemodynamic effects, due to donor-recipient size mismatch, differs significantly from those in adult patients. Despite the complexities related to both patient and surgery, there is a lack of evidence-based anesthesia guidelines for pediatric kidney transplantation. This educational review summarizes the pathophysiological changes to consider and suggests recommendations for perioperative anesthesia care, based on recent research papers.

Intraoperative Near-Infrared Spectroscopy Monitoring of Renal Allograft Reperfusion in Kidney Transplant Recipients: A Feasibility and Proof-of-Concept Study

Conventional renal function markers are unable to measure renal allograft perfusion intraoperatively, leading to delayed recognition of initial allograft function. A handheld near-infrared spectroscopy (NIRS) device that can provide real-time assessment of renal allograft perfusion by quantifying regional tissue oxygen saturation levels (rSO₂) was approved by the FDA. This pilot study evaluated the feasibility of intraoperative NIRS monitoring of allograft reperfusion in renal transplant recipients (RTR). Intraoperative renal allograft rSO₂ and perfusion rates were measured in living (LDRT, n = 3) and deceased donor RTR (DDRT, n = 4) during the first 50 min post-reperfusion and correlated with renal function markers 30 days post-transplantation. Intraoperative renal allograft rSO₂ for the DDRT group remained significantly lower than the LDRT group throughout the 50 min. Reperfusion rates were significantly faster in the LDRT group during the first 5 min post-reperfusion but remained stable thereafter in both groups. Intraoperative rSO₂ were similar among the upper pole, renal hilum, and lower pole, and strongly correlated with allograft function and hemodynamic parameters up to 14 days post-transplantation. NIRS successfully detected differences in intraoperative renal allograft rSO₂, warranting future studies to evaluate it as an objective method to measure ischemic injury and perfusion for the optimization of preservation/reperfusion protocols and early prediction of allograft function.

Transcutaneous near-infrared spectroscopy (NIRS) for monitoring kidney and liver allograft perfusion

BACKGROUND

The use of transcutaneous near-infrared spectroscopy (NIRS) for monitoring the perfusion of kidney and liver allografts has been proposed in the last years. This device might detect an early decrease in allograft oxygenation allowing prompt detection of vascular complications.

METHODS

A systematic review of the literature about the use of transcutaneous NIRS in monitoring allograft perfusion was performed according to the PRISMA guidelines.

RESULTS

The authors screened 1313 papers. The search yielded five pertinent articles. Three of them reported the experience of NIRS in kidney transplantation and the other two dealt with its use in liver transplantation, for a total of 55 paediatric patients and 121 adults. In the studies concerning kidney transplantation, NIRS measurements were significantly related to serum creatinine, estimated glomerular filtration rate (eGFR), urinary neutrophil gelatinase-associated lipocalin (u-NGAL), serum lactate, resistive index assessed by Doppler-ultrasonography and systolic blood pressure. The two studies dealing with liver transplantation found a significant decrease in liver regional oxygenation, assessed by NIRS, before the occurrence of vascular complications.

CONCLUSIONS

Preliminary studies have related NIRS monitoring to kidney and liver allograft perfusion, both in adults and children. Further investigation is needed to establish the normal range of NIRS values and the factors influencing NIRS monitoring.

Near-Infrared Spectroscopy: Clinical Use in High-Risk Neonates

In this review, we describe the near-infrared spectroscopy (NIRS) technology and its clinical use in high-risk neonates in critical care settings. We searched databases (e.g., PubMed, Google Scholar, EBSCOhost) to find studies describing the use of NIRS on critically ill and high-risk neonates. Near-infrared spectroscopy provides continuous noninvasive monitoring of venous oxygen saturation. It uses technology similar to pulse oximetry to measure the oxygen saturation of hemoglobin in a tissue bed to describe the relative delivery and extraction of oxygen. Near-infrared spectroscopy can be a valuable bedside tool to provide clinicians indirect evidence of perfusion. It may prompt early interventions that promote oxygen delivery, which can improve high-risk neonatal outcomes.

NIRS-based monitoring of kidney graft perfusion

Introduction

Acute early vascular complications are rare, but serious complications after kidney transplantation. They often result in graft loss. For this reason, shortening the diagnostic process is crucial. Currently, it is standard procedure to monitor renal graft perfusion using Doppler ultrasound (DU). With respect to acute vascular complications, the main disadvantage of this type of examination is its periodicity. It would be of great benefit if graft blood perfusion could be monitored continuously during the early postoperative period. It appears evident that a well-designed near infrared spectroscopy (NIRS) monitoring system could prove very useful during the early post-transplantation period. Its role in the immediate diagnosis of vascular complications could result in a significant increase in graft salvage, thus improving the patient’s overall quality of life and lowering morbidity and mortality for renal graft recipients. The aim of this study was to design, construct and test such a monitoring system.

Materials and methods

We designed a rough NIRS-based system prototype and prepared a two-stage laboratory experiment based on a laboratory pig model. In the first stage, a total of 10 animals were used to verify and optimize the technical aspects and functionality of the prototype sensor by testing it on the animal kidneys in-vivo. As a result of these tests, a more specific prototype was designed. During the second stage, we prepared a unique laboratory model of a pig kidney autotransplantation and tested the system for long-term functionality on a group of 20 animals. Overall sensitivity and specificity were calculated, and a final prototype was prepared and completed with its own analytic software and chassis.

Results

We designed and constructed a NIRS-based system for kidney graft perfusion monitoring. The measurement system provided reliable performance and 100% sensitivity when detecting acute diminished blood perfusion of the transplanted kidneys in laboratory conditions.

Conclusion

The system appears to be a useful tool for diagnosing diminished blood perfusion of kidney transplants during the early postoperative period. However, further testing is still required. We believe that applying our method in current human transplantation medicine is feasible, and we are confident that our prototype is ready for human testing.

Vascular inflow after renal transplantation: Does the arteriotomy technique impact early allograft perfusion and function?

BACKGROUND

There are two main techniques for arterial reconstruction in RT: TA using a stab longitudinal incision which creates an elliptical opening and AP which fashions a circular defect. We hypothesized that AP creates a natural anastomosis lumen, similar to the donor renal artery, which optimizes RT perfusion.

METHODS

A retrospective review of a single-institution database was performed between 2000 and 2018. Twenty patients who underwent AP arteriotomy were compared to 40 TA-matched controls. Data were collected on creatinine (preoperative, nadir, and time to nadir), and DUS RI and PSV at 1 week, 3 months, and 6-12 months post-RT.

RESULTS

ttNC was shorter in the AP group (5 ± 4 vs 12 ± 13 days; P = .03). PSV at 1 week was lower in the AP group (186 ± 65 cm/s vs 232 ± 89 cm/s; P = .04). There was no difference in nadir creatinine value (P = .26), preoperative creatinine (P = .66), and initial postoperative creatinine (P = .80). RI at week 1 were not different between groups (P = .37). Follow-up DUS showed the difference in PSV between groups became non-significant (1 month P = .50 and 6-12 months P = .53).

CONCLUSIONS

AP arteriotomy in RT improves early perfusion and function parameters (ttNC and initial PSV) as compared to TA. AP arteriotomy optimizes early allograft reperfusion, which may have important long-term implications and deserves further evaluation.

The Use of Near-Infrared Spectroscopy (NIRS) to Measure Cerebral Oxygen Saturation During Body Position Changes on Infants Less than One Year Old

OBJECTIVE

To describe the state of the literature for near-infrared spectroscopy (NIRS) to measure cerebral oxygen saturation during body position changes on infants <1 year old.

INTRODUCTION

Although regional cerebral oxygen saturation is commonly used in critically ill populations, it is not usual practice to tailor care based on differences in the cerebral oxygen saturation during measurements in different body positions. We believe that alterations in cerebral oxygen saturation during position changes can also inform clinicians regarding brain health, such as the regulation of brain blood flow.

INCLUSION CRITERIA

We included studies in infants <1 year old; who had cerebral oxygen saturation measured in varying positions (e.g. supine versus side-lying).

METHODS

On March 30, 2019, we searched Medline, Embase, Cochrane CENTRAL, CINAHL, and Web of Science for studies written in English with no restriction on publication dates. We selected studies that involved infants <1 year old and measured cerebral oxygen saturation during varying body positions.

RESULTS

We found 24 primary studies on 694 infants. The authors investigated whether brain oxygen saturation was influenced by body position. A majority of the studies found a statistically significant difference between cerebral oxygen saturation in various body positions.

CONCLUSIONS

More research needs to be performed on variations in brain oxygen saturation during body position changes and the correlation with outcomes. Knowledge of brain oxygen saturation can provide clinicians an understanding of the infant's brain health. Healthcare providers may adapt care specifically to improve brain health with NIRS-based brain oxygen saturation monitoring.

Monitoring kidney optical properties during cold storage preservation with spatial frequency domain imaging

Transplantation of kidneys results in delayed graft function in as many as 40% of cases. During the organ transplantation process, donor kidneys undergo a period of cold ischemic time (CIT), where the organ is preserved with a cold storage solution to maintain tissue viability. Some complications observed after grafting may be due to damage sustained to the kidney during CIT. However, the effects due to this damage are not apparent until well after transplant surgery has concluded. To this end, we have used spatial frequency domain imaging (SFDI) to measure spatially resolved optical properties of porcine kidneys over the course of 80-h CIT. During this time, we observed an increase in both reduced scattering (μ s& ' ) and absorption (μa) coefficients. The measured scattering b parameter increased until 24 h of CIT, then returned toward baseline during the remaining duration of the imaging sequence. These results show that the optical properties of kidney tissue change with increasing CIT and suggest that continued investigation into the application of SFDI to kidneys under CIT may lead to the development of a noninvasive method for assessing graft viability.