Implantable Doppler Probe as a Vascular Monitoring Device in Kidney Transplant Patients: Investigation of Use at a Single Center

Effectiveness of Implantable Doppler Probe Versus Standard Clinical Care in Preventing Thrombosis-Related Graft Loss in Kidney Transplantation: A Systematic Review and Meta-Analysis

OBJECTIVES

The implantable Doppler probe can monitor the patency of vascular anastomosis, thereby facilitating early detection of vascular thrombosis critical to reducing graft loss. In this study, we examined the effectiveness of this technology compared with standard clinical care in reducing thrombosis-related graft loss and the requirement for color duplex ultrasonography in the first 24 hours postoperatively by a medical literature search of the application of this technology in kidney transplantation.

MATERIALS AND METHODS

We conducted a systematic search (January 15, 2024) of a wide range of experimental and observational studies that comprised kidney transplant recipients monitored with blood flow sensing technology (intervention group) and standard clinical care (control group). Primary outcomes were differences between groups of thrombosis-related graft loss and surveillance requirement of color duplex ultrasonography scans in the first 24 hours postoperatively. Two independent researchers conducted critical appraisal and data extraction of the selected papers using the Joanna Briggs Institute Meta-Analysis of Statistics Assessment and Review Instrument. We used a random effects model for the meta-analysis. Dichotomous outcomes were expressed as relative risk or odds ratio.

RESULTS

The search identified 43 articles. After exclusion criteria, 7 studies (1 experimental, 6 observational) were included, with a total participant sample of 874 adult kidney transplant recipients with and without blood flow sensing technology. The certainty of evidence level was rated as moderate. Blood flow sensing technology resulted in a 66% reduction in the risk of thrombosis-related graft loss and a 61% lower probability of requiring color duplex ultrasonography in the first 24 hours postoperatively compared with standard clinical care.

CONCLUSIONS

Blood flow sensing technology can be used as a helpful adjunct in the postoperative monitoring of kidney transplant recipients. However, given the technical limitations, signals should be interpreted alongside the traditional clinical assessment techniques.

Experiences of Participation in a Study Investigating Feasibility of the Implantable Doppler Probe in Kidney Transplantation: An Embedded Qualitative Study

OBJECTIVES

Kidney transplant survival can be improved with better graft surveillance postoperatively. In the quest to explore new technologies, we explored the feasibility of an implantable Doppler probe as a blood flow monitoring device in kidney transplant patients. This qualitative study was embeddedin a feasibility trial and aimed to test the device's clinical acceptability and obtain suggestions for the development of the intervention. Objectives included exploring the experiences of feasibility study participants and identifying barriers to the implementation of implantable Doppler probes in clinical practice.

MATERIALS AND METHODS

We conducted semi-structured interviews containing open-ended questions with 12 feasibility study participants recruited by purposive sampling. All interviews were audio-recorded with verbatim transcription. Thematic data analysis was performed at the latent level by using an inductive approach with a previously published 6-phase guide.

RESULTS

Three key themes emerged: (1) perceived value of the intervention in clinical practice, (2) challenges and barriers to implementation of the intervention, and (3) suggestions forthe development of the intervention. Due to functional limitations and lack of research, medical professional participants revealed clinical equipoise regarding the utility of implantable Doppler probes. However,the device was well received by patient participants. Challenges included device training needs for medical professionals and educational sessions for patients. Innovative ideas for development included the insertion of a display screen, adopting disposable units to reduce overall cost, online access allowing remote monitoring, decreasing external monitoring unit size, and integrating a wireless connection with the probe to reduce signal errors and increase patient safety.

CONCLUSIONS

The clinical need for blood flow sensing technology in kidney transplants has been widely acknowledged. Implantable Doppler probes may be a beneficial adjunct in the early postoperative surveillance of kidney transplant patients. However, the device's technical limitations are the main challenges to its acceptance in clinical practice.

A Study Protocol Exploring the Role of an Implantable Doppler Probe in Kidney Transplantation: A Feasibility Randomized Controlled Trial with an Embedded Qualitative Study

OBJECTIVES

Vascular complications in kidney transplant surgery constitute one-third of early graft loss, which can be prevented by timely diagnosis of vascular compromise. A blood flow monitoring device may have a beneficial role in the early identification of graft hypoperfusion critical to reducing graft loss. This research protocol aims to evaluate the potential of an implantable Doppler probe as a blood flow monitoring device in kidney transplant recipients.

MATERIALS AND METHODS

The potential study will be a mixed methodology, 2-arm feasibility randomized controlled trial with an embedded qualitative study. For the trial, we will compare demographic characteristics and outcome measures of kidney transplant patients receiving implantable Doppler probe monitoring (intervention group, n = 30) with those having standard clinical care (control group). For the qualitative study, we will conduct semi-structured interviews with stakeholders (n = 12) recruited by purposive sampling to explore experiences of participants. All interviews will be audio recorded with verbatim transcription.

RESULTS

Our results will use the summarized quantitative data and descriptive statistics to determine differences between the groups. We will use CONSORT guidelines to determine the suitability of the research processes, availability of research resources, and potential challenges faced during the feasibility randomized controlled trial. We will use thematic analysis and NVivo software to analyze the acceptability of the intervention in clinical practice. We will compile the results according to the consolidated criteria for reporting qualitative research checklist.

CONCLUSIONS

The goal of this protocol is to determine the feasibility of an implantable Doppler probe monitoring device in kidney transplant recipients. The feasibility study will collect preliminary information, fill gaps in evidence, and test research processes for the pragmatic future randomized controlled trial. The template of this study is transferable to other transplant centers across the United Kingdom.

The Use of the Implantable Doppler Probe as a Blood Flow Monitoring Device in Clinical Settings: A Narrative Review of the Evidence

OBJECTIVES

In the past decade, the implantable Doppler probe has been studied widely as a blood flow-monitoring device in reconstructive and transplant surgical specialities. Its utility as an effective postoperative monitoring technique is still debatable, with no clear guidelines in clinical practice. Here, we mapped the current evidence on the usefulness of the implantable Doppler probe as a blood flow-monitoring device. The objective was to present an up-to-date assessment of the benefits and limitations of using implantable Doppler probes in clinical and experimental clinical settings.

MATERIALS AND METHODS

We conducted a literature search using the Cochrane Library and Healthcare Databases Advanced Search and using implantable Doppler probe, transplant, graft, and flap as key words. The search yielded 184 studies, with 73 studies included after exclusions. We evaluated, synthesized, and summarized the evidence from the studies in tabular form.

RESULTS

There is clinical equipoise regarding the effectiveness of implantable Doppler probe as a flow sensing technique. The main reason is the lack of information and gaps in the evidence regarding the benefits and limitations of using implantable Doppler probes in clinical practice.

CONCLUSIONS

The implantable Doppler probe has the potentialto be used as an adjunctpostoperativeblood flow-monitoring device. However, keeping in view of technical limitations, its signals should be interpreted alongside traditional clinical assessment techniques to determine the patency of microvascular anastomosis. Although evidence in this review will inform clinical practice in transplant and reconstructive surgical specialties, a prospective randomized controlled study with a larger patient cohort is required to evaluate the effectiveness of this probe in clinical settings.

Are Signals from Implantable Doppler Probes Always Accurate for Prediction of Blood Flow in Kidney Transplant?

Vascular anastomotic occlusion has a catastrophic outcome in kidney transplant. The implantable Doppler probe is a blood-flow monitoring device that provides real-time information and direct assessment of anastomotic patency. We present the case of a complex kidney transplant recipient who was postoperatively monitored with an implantable Doppler probe attached to the renal artery. The patient showed clinical deterioration despite a continuous trace of Doppler signals. An urgent color duplex scan confirmed renal vein thrombosis. Interestingly,the Doppler signals persisted during the surgical exploration, which revealed a grossly discolored and congested graft with renal vein thrombosis. The persistent Doppler signals were caused by the back-and-forth blood flow in the renal artery due to the blood pressure shifts during the cardiac cycle against the high intrarenal resistance of the thrombosed graft. Therefore, the signals of implantable Doppler probes should be interpreted alongside the traditional clinical assessment techniques to ensure safe and effective postoperative monitoring. This information will inform the clinical practice in kidney transplant surgery.

Overview of Biofluids and Flow Sensing Techniques Applied in Clinical Practice

This review summarizes the current knowledge on biofluids and the main flow sensing techniques applied in healthcare today. Since the very beginning of the history of medicine, one of the most important assets for evaluating various human diseases has been the analysis of the conditions of the biofluids within the human body. Hence, extensive research on sensors intended to evaluate the flow of many of these fluids in different tissues and organs has been published and, indeed, continues to be published very frequently. The purpose of this review is to provide researchers interested in venturing into biofluid flow sensing with a concise description of the physiological characteristics of the most important body fluids that are likely to be altered by diverse medical conditions. Similarly, a reported compilation of well-established sensors and techniques currently applied in healthcare regarding flow sensing is aimed at serving as a starting point for understanding the theoretical principles involved in the existing methodologies, allowing researchers to determine the most suitable approach to adopt according to their own objectives in this broad field.