Key words : Blood flow sensing technology, Kidney transplant thrombosis, Thematic analysis, Qualitative semi-structured interviews

Introduction

A kidney transplant is the best long-term renal replacement therapy for patients with end-stage renal failure.¹ Despite significant advances in medical care over the past decade, about 3.5% to 5.7% of total kidney transplants are lost as a result of vascular complications.² Arterial and venous complications contribute to 0.2% to 7.5% and 0.1% to 8.2% of total kidney graft loss, respectively.²

Patients with graft loss comprise 4% of the current haemodialysis population and 16% of patients on the transplant wait list in the United Kingdom.³ Because of the increased numbers of comorbidities, HLA sensitization, depression, and wait times for retransplant morbidity and mortality are well recognized in this patient group.⁴

The 30-day and 90-day mortality rates in kidney graft loss patients are 5.2% and 11.1%, respectively.⁵ Cardiovascular disease and infections are attributed as major causes.⁵ Although hemodialysis provides (at best) 10% of the normal kidney function, it is associated with a 17-fold increased risk of mortality in this patient group.⁶

An implantable Doppler (ID) probe is a blood flow monitoring device that is capable of delivering real-time information on vascular patency.⁷ The ID probe has been successfully used for microvascular monitoring in cardiovascular, plastic, and breast reconstructive surgeries.⁸ In a similar way, the ID probe may assist in the timely recognition of vascular complications and reduce graft loss after kidney transplant.⁹

According to the Medical Research Council UK guidelines, qualitative studies are endorsed to inves-tigate complex interventions as these studies can inform the decision to adopt an intervention in clinical practice, refine components of the intervention, and address research ethics.^10,11 A qualitative study embedded in a feasibility trial can offer an oppor-tunity to identify the likely range of challenges and suggest solutions to mitigate them, before the conduct of a definitive large-scale trial.¹²

Survival after kidney transplant can be improved with better graft surveillance postoperatively.¹³ In the constant pursuit to explore new technologies, we previously conducted a randomized controlled trial (CONDOR study) to investigate the feasibility of ID probes as a blood flow monitoring device in kidney transplant patients.¹⁴ This qualitative study was embedded in the feasibility trial with the aim to investigate the clinical acceptability of ID probes and obtain suggestions for the development of the intervention. The objective was to explore the experiences of feasibility study participants and, by doing so, identify barriers to the implementation of ID probes in clinical practice (ie, stakeholder-related, research-specific, resources-related, cultural, and organizational barriers).

Materials and Methods

The ID probe is regularly used for the vascular moni-toring of kidney transplant patients at the Southwest Transplant Centre (SWTC), University Hospitals Plymouth NHS Trust.¹⁵ Having the ID probe in regular use at SWTC allowed us to conduct the easibility trial with an embedded qualitative study, which occurred from April 2022 to July 202314 (Figure 1).

Participant selection
Participants of the qualitative study comprised patients who underwent kidney transplant surgery with ID probe monitoring and the transplant surgeons, clinicians, and nurses involved with the postoperative patient care at the SWTC during the study duration. Selected patients were familiar with the ID probe, and healthcare professionals were knowledgeable about the functioning of the ID probe monitoring device. We used purposeful sampling to ensure the selection of information-rich participants who would provide an overall comprehensive perspective of the ID probe.¹⁶

Sample size
Participants (n = 12) consisted of 4 each of clinicians, nurses, and kidney transplant patients. The sample size was comparable to previous qualitative studies that attained theoretical saturation.^17,18 All participants provided study consent. We provided participants with detailed information and a leaflet of the research process, further correspondence for member checking, and publication of findings.

Settings
All kidney transplant patients at SWTC are routinely transferred to the renal ward for postoperative management. Qualitative interviews generate the best results when conducted at timings and in settings comfortable for participants.¹⁹

Data collection
We conducted semi-structured interviews with all participants following the National Institute for Health and Care Research UK guidance on qualitative studies.²⁰ The most effective way to explore the reflections and experiences of participants is through semi-structured interviews with open-ended questions.²¹ Our interviews followed a sequence starting with an introduction, an explanation of the purpose of the study, consent, and interview questions (Table 1). We encouraged participants to elaborate on their answers by using probe questions (Table 2).

The duration of the interview was 40 to 45 minutes. We conducted interviews in the renal ward, during the participants’ free time, to ensure an informal and relaxed environment without any distractions. We maintained participant privacy to allow anonymity.²² We informed participants that any quotes published would be pseudonymized and their identities kept strictly confidential.

We audio-recorded all interviews with verbatim transcription, which was subsequently deleted. We gathered field notes during the interviews to promote the richness of data.²³

Ethical review
The Continuous Implantable Doppler Probe Monitoring in Renal Transplant Study (a feasibility randomized controlled study with an embedded qualitative study) was approved prospectively by the regional and national ethical committees, including Health Research Authority UK (approval reference ID 302833), North of Scotland Research Ethics Committee (approval reference ID 22/NS/0009), University of Plymouth Faculty Research Ethics and Integrity Committee (approval reference ID 3358), and University Hospitals Plymouth NHS Trust (R&D department sponsorship number 21/SUR/626.4863). The study is registered with ClinicalTrials.gov (identifier: NCT05634863).

Data analyses
Thematic analysis is a technique to identify, analyze, and interpret patterns in qualitative research.²⁴ It allows an in-depth understanding of participants’ experiences and perspectives concerning a phenomenon.²⁵ Limitations to thematic analysis include the time-consuming process and the dependence on the researcher’s judgment.²⁶ To reduce the potential for interviewer bias, who had a theoretical interest in ID probe monitoring, inductive thematic analysis by data-driven identification of themes was performed.²⁷ Moreover, as all participants had experience and knowledge of ID probes, their underlying ideas and assumptions were interpreted by latent-level content analysis.²⁸

We followed the 6-step thematic analysis process (Figure 2), which was originally developed by Braun and Clarke.^24,25 The first step was familiarization of data. We repeatedly read the collected data to identify patterns of potential interest and meaning. The second step was the generation of codes. We conducted a data-driven meaningful coding of the extracts. The third step was combining codes into themes; for this, we collated codes into broader themes. The fourth step was a review of themes; we refined the themes from codes, categories, and subthemes according to their relevance, internal homogeneity, and external heterogeneity. The fifth step was establishing the significance of themes. We identified the essence or attributes of each theme and constructed a narrative, addressing the research question. In the final step, we collected findings in the form of a concise write-up.^24,25 The thematic analysis was done with NVivo software (version 12).²⁹ We reported results under the Consolidated Criteria for Reporting Qualitative Research checklist.³⁰

Trustworthiness of data
Some of the challenges faced in qualitative research involve the researcher’s impressions, lack of reproducibility, and generalization. Previous work has reported that the spirit of inquiry and responsiveness are more important than specific techniques to reduce bias in qualitative studies.³¹ Nevertheless, the demonstration of trustworthiness in qualitative research confers respectability and validity to the results. Shenton³² and Hadi and Closs³³ in their studies endorsed the importance of following Guba and Lincoln’s 4-criteria strategy to ensure trustworthiness in qualitative research. The criteria and measures to ensure trustworthiness in qualitative research are described in Table 3.

Credibility
Credibility is attributed to the confidence that can be placed in the quality and integrity of the research findings.³² We applied prolonged engagement, theoretical saturation of data, and respondent validation to ensure the credibility of the results. Prolonged engagement with the participants during the interviews allowed time for an in-depth understanding of perceptions.³³ We continued the recruitment of study participants until theoretical saturation of data was achieved.¹⁸ After the interviews, we contacted participants again for feedback about the emerging interpretations and noted participant reactions.³⁴

Transferability
Transferability is the extent to which the study findings can be transferred to other settings or populations.³⁰ Study transferability is ensured by giving an adequate description of the research processes and purposeful sampling. The qualitative research findings are transferable, as the study participants and settings are similar to any kidney transplant unit across the United Kingdom.³³

Confirmability
Confirmability is the degree to which the research findings are confirmed by or agreed to by other researchers.³⁰ Reflexivity strategies and triangulation of data collection are used to ensure rigor and value to the qualitative study. The researcher’s impressions were bracketed by the use of a reflective diary, and all research questions were formulated in a neutral format.²⁶ The triangulation of data collection was applied by obtaining perspectives from all 3 groups of participants involved with ID probe monitoring (patients, nurses, and clinicians).¹⁶

Dependability
Dependability is the extent to which the research findings are consistent and repeatable.30 We established dependability by maintenance of an audit trail and peer review. The analysis process of this study was reviewed by 2 colleagues (clinician and transplant surgeon).³⁵ An audit trail elaborating on all decisions by the researcher is displayed in Tables 4, 5, and 6. All themes and interpretations were supported by participants’ verbatim quotes.³² Having quotes increases the study consistency by showing a direct connection between the researcher’s interpretations and the participants’ responses.³³

Results

Data analyses showed the emergence of 3 key themes: (1) perceived value of the intervention in clinical practice, (2) challenges and barriers to implementation of the intervention, and (3) suggestions for the development of the intervention. Regarding the perceived value of intervention, because of the probes’ functional limitations and lack of research in the field, the medical professionals disclosed a clinical equipoise regarding the utility of ID probes. However, the device was well received by patients. Concerning challenges and barriers, the device training needs for medical professionals and educational sessions for patients were identified, necessitating an organizational structure in the units where ID probe monitoring is not used locally. About suggestions for future development, innovative ideas comprised 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. A word cloud for the most frequently used words in the qualitative interviews is shown in Figure 3.

Theme 1: Perceived value of the intervention in clinical practice
Table 4 elaborates on the audit trail of theme 1. Mixed feedback was given by the participants regarding the perceived value of ID probe monitoring in kidney transplants, reflecting a clinical equipoise. Theme 1 was derived from 2 subthemes: positive and negative experiences with the monitoring device. Positive experiences with the device included benefits to the health care professionals, nurses, and the health care system. The participants felt that ID probes had the potential to improve patient safety, graft outcomes and increase financial savings to the NHS.

Negative experiences with the device included difficulties encountered during the application of the device and anxiety related to false positive results.

Theme 2: Challenges and barriers to implementation of the intervention
Table 5 elaborates on the audit trail of theme 2, which highlighted participants’ difficulties and organiza-tional hurdles during the implementation of ID probes at SWTC. Two subthemes were identified. The first subtheme described difficulties encountered by health care professionals, which underlined a need for device training by health care professionals and educational sessions for the patients.

The second subtheme described the requirement of an organizational structure to support the functioning of the device in the Trust, emphasizing the need to secure administrative support and develop a pathway for the procurement and storage of the device.

Theme 3: Suggestions for the development of the intervention
Table 6 elaborates on the audit trail of theme 3. Theme 3 described suggestions and proposals for the development of the device and consisted of 2 subthemes. The first subtheme consisted of innovative ideas for the improvement of the device in terms of insertion of a display screen, decrease in the size of the monitoring device, and introduction of financially cost-effective disposable units.

The second subtheme described recommended modifications that would improve patient safety, including designing a wireless connection between the probe and the monitoring device. The importance of further research to refine components of the intervention was highlighted.

Discussion

Qualitative studies have increasingly been incor-porated in feasibility studies to acquire a global overview of whether an intervention is ready for uptake into routine clinical practice.¹² Our qualitative study was embedded in a randomized controlled trial (CONDOR study) previously conducted to assess the feasibility of blood flow sensing technology in kidney transplant patients.³⁶ The study identified barriers and facilitators of the ID probe at an early stage, allowing improvements to be made, before the start of a pragmatic main trial. The ADNAT study¹⁰ and Project ACE¹¹ are examples of mixed-methods studies (feasibility randomized controlled trial with embedded qualitative work) that have assessed the acceptability of interventions to stakeholders.

The study participants had mixed reactions regarding the perceived value of the intervention in clinical practice. Earlier consultations have also revealed clinical equipoise on the possible role of the ID probe as a monitoring device.³⁷ Although the benefits of blood flow sensing technology in kidney transplant surgery have been acknowledged, a lack of information and gaps in evidence are the main reasons for apprehensions surrounding the probes’ utility.³⁷ However, clinical equipoise is a motive for future research, as it is an essential ingredient for unbiased research with therapeutic intent.³⁸

The clinician participants felt secure with the use of ID probes in kidney transplant patients. They described Doppler signals as reassuring, and this allowed them the comfort to request fewer color duplex ultrasonograph scans. Malik and colleagues reported reliable ID probe blood flow monitoring in a high-risk patient with a kidney transplanted directly on an iliofemoral polytetrafluoroethylene graft.³⁹ However, the surgeons felt unsure of the device as they were concerned regarding the possible risk of renal artery constriction at the ID probe application site. Kreutz-Rodrigues and colleagues reported no adverse clinical outcomes over a 3-year follow-up of 18 patients with musculocutaneous free flaps and with retained ID probes.⁴⁰ Future retrospective studies on long-term complications of retained probes are warranted.⁴⁰

Similarly, there were concerns about the risk of vascular injury during probe removal. At the SWTC, ID probes have been used uneventfully in kidney transplant patients for the past 7 years,7 and no such accidents have been encountered during our study; all probes were removed safely with gentle traction on the connecting wire. Nevertheless, previous studies have reported bleeding from arterial anastomosis and pedicle laceration with resultant graft loss following probe extraction.^41,42 Because the probe is not under direct vision during its detachment from the renal artery, any accidental bleeding could be catastrophic in kidney transplant patients.⁸

The ID probe was well received by the patient participants. No issues regarding recruitment, randomization, and follow-up were reported. The patients understood the importance of research and were keen to participate in the study. Earlier work conducted on the ID probe also revealed enthusiastic patient participation.³⁷ Patients valued participating in their postoperative care, and the probe did not cause any discomfort or hindrance to their mobility.⁴³ The clinician participants deemed the outcome measures selected for the study as appropriate, routinely measured in clinical practice, and easily comparable to inform clinical decision-making.

Individual-specific and organizational challenges to the implementation of ID probes in clinical practice were identified. Requirements for device training for health care professionals and educational sessions for patients were proposed to reduce professional anxiety and apprehensions, respectively. In their qualitative study, Macurik and colleagues emphasized the importance of training professionals and educating patients in intervention plans.⁴⁴ No problems with intervention adherence at the SWTC were reported. Because all of the participants were known to the researcher, to avoid social desirability bias, his viewpoint on the device was not disclosed.³⁷ To avoid problems of adherence at other participating centers, the motivation of clinicians and prolonged engagement with patients are recommended as key considerations to inspire retention.¹⁰ Likewise, other centers would have to develop a device-related organi-zational structure and pathways for procurement, storage, and maintenance.

The interviews revealed innovative ideas for the improvement of the ID monitoring device. The nurses suggested the insertion of a vibrant display screen and a decrease in the size of the monitoring device. The visual presentation of the signals would assist signal interpretation and reduce nurses’ learning curves for the device. It would also allow the functioning of the monitoring device in silent mode while patients are resting. Designing small disposable units would be convenient for patients and could reduce the overall cost of procurement, storage, and maintainance.⁴⁵

The clinicians proposed modifications to the device to address its technical limitations and increase patient safety. The probe is attached to the external monitoring device with a delicate connecting wire.⁹ This wire is sensitive to traction and easily dislodged, particularly during patient movement. An inadvertent wire detachment leads to false positive cases (ie, cessation of signals, despite normal blood flow in the vessels).¹⁵ Negative surgical reexplorations in false positive cases resulting from accidental wire disentanglements have been reported.⁸ A second shortcoming of the ID probe is its capacity to provide reliable patency information of only the vessel to which it is attached. In kidney transplants, the ID probe is attached to the renal artery, so it offers direct blood flow assessment of the renal artery¹⁴; because the probe cannot be attached to thin-walled renal veins, it is unable to provide direct information on renal vein patency.¹⁵ These drawbacks can be thwarted by designing a wireless connection between the probe and the monitoring device. Developing a link through Bluetooth or WIFI systems could enable probes to be attached to renal veins, increasing the accuracy of venous return information and reducing false positive cases resulting from inadvertent wire detachments.

The essence of the interviews demonstrated that the participating groups appreciated the benefits of a blood flow monitoring device in the postoperative care of kidney transplant patients. Previous studies evaluating the merits of ID probes are in agreement, that thrombotic graft loss can only be reduced with timely diagnosis and prompt surgical intervention.^37,39 However, the value of an ID probe as a blood flow monitoring device, its role in the prevention of graft loss, and its acceptability to stakeholders can be substantially improved by refining the components of the intervention. An ID probe may be used as a beneficial adjunct for vascular monitoring of kidney transplant patients, alongside the traditional clinical assessment techniques and color duplex ultrasonography.⁴³

There was complete consensus among all participant groups for the need for continuing research to improve graft outcomes. A pragmatic large-scale controlled study is recommended to evaluate the effectiveness of ID probes in clinical settings.⁴⁶

Conclusions

There is a clinical requirement for the implemen-tation of blood flow sensing technology in kidney transplantation. The use of ID 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.

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