Project 2

RAKT in the obese patient

Positive outcomes inspired groups to use RAKT in an increasing number of settings, including deceased donation [48], polycystic kidney disease [40] and multiple vessel grafts in living donation [44]. However, most important is the use of RAKT in obese patients. The only current universal indication for RAKT, performed in the context of appropriately monitored prospective studies, is for those obese patients who would not otherwise be able to have a kidney transplant due to an unacceptable risk of morbidity. Obesity in renal transplantation is a growing problem, with the BMI of patients on the waiting list increasing annually [49]. In developed countries, the BMI of the population overall has continued to increase [50] and renal transplant candidates are no exception. An earlier study from the USA reported that between 1987 and 2001, the proportion of obese transplant recipients rose by 116% [51]. Traditionally, increased BMI was seen as a relative contraindication to renal transplantation, but recent data show considerable benefit in obese recipients [52]. Despite this, analysis of the United Network for Organ Sharing (UNOS) database revealed that 21% of transplant centres do not list morbidly obese patients [53], which may be an underestimation. Those listed wait an average of 50 months for a transplant compared with the 40 months of non-obese patients [53]. The issue is further compounded by the ‘BMI paradox’, i.e. the fact that in the dialysis population, a high BMI is, up to a point, a marker of improved prognosis [54]. The obese population is at higher risk of post-operative SSI [55], with obese transplant recipients experiencing higher incidences of SSI, prolonged operative times and longer hospital stays [56–58]. Taken together, these facts have prompted a rethink and search for new strategies to address the issue. Bariatric surgery has been advocated in very obese transplant candidates [59], but access to this type of surgery is not universal. New approaches to successfully transplant the obese recipient are therefore eagerly awaited.

RAKT provides one such hope, with Oberholzer et al. [31] demonstrating successful transplant and favourable outcomes in RAKT compared with OKT in 28 morbidly obese patients. A group from Chicago compared 28 cases (average BMI 42.6) undergoing RAKT to a frequency-matched retrospective cohort of obese patients (average BMI 38.1) undergoing OKT. RAKT patients experienced significantly lower rates of SSI compared with the control group: 28.6% versus 3.6%, respectively. Patient and graft survival were 100% in both groups at 6 months and 6-month creatine was comparable between the two groups: 1.5 mg/dL versus 1.6 mg/dL in RAKT and OKT, respectively. This clearly shows superior outcomes in terms of SSI and the ability to offer transplantation to groups at high risk of complications. The group continues to demonstrate excellent outcomes [31], with recent data on 239 RAKTs with a mean BMI of 41.4 kg/m² highlighting a post-operative SSI rate of just 0.4%. Graft survival at years 1 and 3 was 98% and 93%, respectively, with a mean eGFR at 1 year of 56.5 ± 17.3 mL/min. Importantly, the group also demonstrated a low mortality of 4.6%, with patient survival of 98% and 95% at 1 and 3 years, respectively. While encouraging, the underlying message is that these results are from a dedicated single-centre experience with experienced surgeons who have passed associated LCs.

In addition to RAKT for obese patients, many teams have performed sleeve gastrectomy, and the safety was demonstrated by a randomized trial performed by Spaggiari et al. [60]. Eleven patients were recruited to a robotic sleeve gastrectomy and RAKT group and nine patients to RAKT alone. At the 1-year follow-up there was a significant (P = 0.0041) change in the BMI between the robotic sleeve gastrectomy and RAKT group (8.76 ± 1.82) compared with the RAKT-alone group (1.70 ± 2.30). There was no significant difference between the eGFR, serum creatinine, readmission rates and graft failure rates up to 12 months, although the length of surgery was longer in the robotic sleeve gastrectomy RAKT group (405 versus 269 min; P = 0.00 304) with no difference in estimated blood loss.

Patient selection for RAKT

It is imperative that patients offered RAKT are selected on the basis of the following parameters: physiological reserve to undergo surgery using pneumoperitoneum, complexities in the donor kidney and the surgical team's experience in performing RAKT. Many teams will consider multiple lower abdominal procedures, calcified aorto-iliac vessels and a lack of appropriate team members as absolute contraindications for RAKT. Robotic teams, after the LC, may consider transplanting grafts with multiple vessels and perform RAKT for patients receiving kidneys from deceased donors. However, most units offer RAKT for transplants from live donors only and Vignolini et al. [48] showed a five-phase approach to consider for teams to perform RAKT from deceased donors. They follow the same principles used to perform RAKT from live donors: availability of a team, operating room with a robot, suitable recipient, anatomical variation of the kidney and cold ischaemia time (CIT). Many units may consider offering RAKT from deceased donors in the time ahead, and the experience gained will offer the advantages of minimally invasive kidney transplant to more recepiants.

ETHICAL CONSIDERATIONS

While creativity and the introduction of novel technologies to improve outcomes and patient experiences is the norm in modern surgical practice, RAKT is perhaps a surgical field that highlights the ethical challenges of surgical innovation [81]. The primary endpoint of surgical transplantation is successful graft function that lasts for a lifetime. The ethical criteria that need to be considered by departments and individual surgeons seeking to introduce RAKT is whether robot-assisted transplantation provides a similar or better technical vascular anastomosis than an open approach and if incision-related morbidity is less than with an open procedure. These ethical considerations are similar to Knight's assessment of innovations in cardiothoracic surgery, including minimally invasive cardiac surgery [82]. Based on these, any surgeon carrying out an RAKT should ask, ‘Can I, with my skill set, in my demographic practice, provide as good or better transplant graft and patient outcomes, when compared with an open implant, with a similar tariff?’ The variables addressed in such self-reflection should be openly discussed with the patient during the consent process, alongside the overall effectiveness of robotic procedures relative to other approaches.

Regular appraisal of surgical ability and outcomes, combined with institutional support for pioneering intervention, will allow safe and efficient progress. With every new approach that evolves, it is essential to continually assess the goals and outcomes that must be achieved, ensuring the procedure is held to the correct standard and patient safety preserved. Robotic surgery is still maturing and long-term follow-up of RAKT patients is as yet not available; we may find that outcome measures and early perceived benefits must be reassessed in light of long-term results. This is essential for all multidisciplinary teams and should be sought by referring physicians and funding bodies as well as surgical teams. Cost must also be borne in mind, ensuring a fair distribution of funding, particularly when transplant patients comprise a relatively small proportion of the wider populations that healthcare services treat.

Ultimately it is of the utmost importance that patients chose the right procedure for them, with the support of their team and careful explanation of appropriate literature, alongside honest conversations about risk, local expertise and the LC involved—true evidence-based medicine.

Mobility is a big factor in the mechanical design of a medical device. On the surface are the big obvious questions: Will it move? Does it have wheels? Does it have to be small, light, and portable? But for medical devices, it’s a lot more than that. Under the IEC 60601-1 Medical Electrical Equipment standard, the mobility classification of a device defines which tests need to be conducted in order to evaluate safety in reasonably foreseeable use scenarios. That means incorrectly defining device mobility (or failing to define it at all) may not only result in a different product than you had envisioned, but it may also result in a design that is not suitable for some of the most rigorous mechanical tests that will be required. Failing to plan for this means your device may require major re-designs right before you thought you were ready for regulatory submission and transfer to manufacturing.

For example, we once changed a device from a mobile cart design to a portable design, as the bottom half of the cart design was mostly empty and users had ready access to benchtops. The device could essentially be sliced in half, and the bottom discarded. The remaining top half became a portable unit. Because the portable version had to pass drop testing, have strong handles, and survive impact tests, making the change was not nearly as simple as it seemed on the surface. Luckily, the designers were aware of the implications and discussed the impacts on the development program early enough to allow for effective planning of the new approach.

Mobility is only one of several categorizations defined as part of 60601-1, including (for example) applied parts and patient supports. However, mobility definitions are spread throughout Clause 9 and 15 of the standard, and this has been challenging to navigate in my experience. This article endeavours to bring clarity to this critical categorization and give examples of why mobility is so important. This flowchart will guide you through all possible classifications and their associated tests:

What Is 60601-1 Anyway?

IEC 60601-1 is a widely recognized standard for medical device safety. This means adherence is either mandatory or very helpful (depending on the region) to obtain regulatory clearance. Within the standard, tests are defined and must be completed in order to verify the safety and efficacy of the device. Not every test in the regulation is required for every device; they vary depending on which classification of device you’re designing. For example, a device that never touches patient tissue (such as many types of benchtop analyzers) doesn’t need to be tested for biocompatibility, but devices that do (such as a contact lens) are subject to biocompatibility testing (more about biocompatibility here). Similarly, devices that can be moved (are transportable) have different expectations and are tested differently than devices that are stationary. The standard has seven different classifications for each type of mobility plus an eighth, a parent term as shown in the chart above.