Operative vectors, anatomic distortion, fluid dynamics and the inherent effects of pneumatic insufflation encountered during transanal total mesorectal excision

Carbon Dioxide Embolism During Transanal Total Mesorectal Excision: Case Report and Literature Review

The actual incidence of carbon dioxide embolism during transanal total mesorectal excision (taTME) is unknown, but the reported incidence in the existing literature is reassuring. However, the incidence of CO2 embolism, which can be life-threatening, is severely underestimated. By reviewing the available data on carbon dioxide embolism during taTME and synthesizing other reports on CO2 embolism in laparoscopic procedures, we provide the first comprehensive account of the etiology, pathophysiology, and recommend tools to monitor carbon dioxide embolism during taTME. Additionally, we provide guidance and recommendations on preventive and therapeutic measures to minimize the adverse consequences of this potentially severe complication, knowledge about which we hope will improve patients' safety.

3D pelvimetry and biometric measurements: a surgical perspective for colorectal resections

PURPOSE

Male sex, high BMI, narrow pelvis, and bulky mesorectum were acknowledged as clinical variables correlated with a difficult pelvic dissection in colorectal surgery. This paper aimed at comparing pelvic biometric measurements in female and male patients and at providing a perspective on how pelvimetry segmentation may help in visualizing mesorectal distribution.

METHODS

A 3D software was used for segmentation of DICOM data of consecutive patients aged 60 years, who underwent elective abdominal CT scan. The following measurements were estimated: pelvic inlet, outlet, and depth; pubic tubercle height; distances from the promontory to the coccyx and to S3/S4; distance from S3/S4 to coccyx's tip; ischial spines distance; pelvic tilt; offset angle; pelvic inlet angle; angle between the inlet/sacral promontory/coccyx; angle between the promontory/coccyx/pelvic outlet; S3 angle; and pelvic inlet to pelvic depth ratio. The measurements were compared in males and females using statistical analyses.

RESULTS

Two-hundred patients (M/F 1:1) were analyzed. Out of 21 pelvimetry measurements, 19 of them documented a significant mean difference between groups. Specifically, female patients had a significantly wider pelvic inlet and outlet but a shorter pelvic depth, and promontory/sacral/coccyx distances, resulting in an augmented inlet/depth ratio when comparing with males (p < 0.0001). The sole exceptions were the straight conjugate (p = 0.06) and S3 angle (p = 0.17). 3D segmentation provided a perspective of the mesorectum distribution according to the pelvic shape.

CONCLUSION

Significant differences in the structure of pelvis exist in males and females. Surgeons must be aware of the pelvic shape when approaching the rectum.

Development and early outcomes of the national training initiative for transanal total mesorectal excision in the UK

AIM

Transanal total mesorectal excision (TaTME) has attracted substantial interest amongst colorectal surgeons but its technical challenges may underlie the early reports of visceral injuries and oncological concerns. The aim of this study was to report on the feasibility, development and the outcome of the national pilot training initiative for TaTME-UK.

METHODS

TaTME-UK was successfully launched in September 2017 in partnership with the healthcare industry and endorsed by the Association of Coloproctology of Great Britain and Ireland. This multi-modal training curriculum consisted of three phases: (i) set-up; (ii) selection of pilot sites; and (iii) formal proctorship programme. Bespoke Global Assessment Scoring (GAS) forms were designed and completed by both trainees and mentors. Data were collected on patient demographics, tumour characteristics and perioperative clinical and histological outcomes.

RESULTS

Twenty-four proctored cases were performed by 10 colorectal surgeons from five selected pilot sites. Median operative time was 331 ± 90 (195-610) min which was reduced to 283 ± 62 (195-340) min in the final case. Independent performance (GAS score of 5) was achieved for most operative steps by case 5. There was one conversion (4.2%), but no visceral injuries. Pathological data confirmed no bowel perforation and intact quality of the mesorectal TME specimens with clear distal margin in all cases and circumferential margins in 23/24 cases (96%).

CONCLUSION

This exploratory study demonstrates acceptable early outcomes in a small cohort suggesting that a competency-based multi-modal training programme for TaTME can be feasible and safe to implement at a national level.

Tips and Tricks

The role of transanal total mesorectal excision (taTME) in minimally invasive proctectomy, especially rectal cancer surgery, is increasing. There has been exponential growth in uptake from the initial in vivo case in 2010 to the present day. Early adopters of taTME are well within the mature portions of their learning curve, but there are a significant number of novice taTME surgeons. We have overviewed the critical aspects of patient selection, operating room set-up, and necessary equipment. In particular, we recommend that a one-team approach is used for the early cases, and ideally with an experienced proctor. The important technical pearls that will aid the novice taTME surgeon were also described.

Anatomical Considerations and Procedure-Specific Aspects Important in Preventing Operative Morbidity during Transanal Total Mesorectal Excision

As transanal total mesorectal excision (taTME) becomes increasingly utilized, its technical challenges and potential pitfalls have become more clearly appreciated. This chapter explores the differences in how anatomy presents itself from the taTME vantage point as compared with traditional approaches to taTME, and how special problems unique to taTME pose a new set of operative challenges. Morbidity related, specifically, to the technique of taTME is also delineated with particular focus on male urethral injury.

Future Directions

Transanal total mesorectal excision (taTME) is a novel technique that has evolved over the years to address the challenges of low rectal cancer surgery by applying the principles and benefits of laparoscopic surgery to more historic transanal techniques. It has been popularized through its use in rectal cancer, but the transanal approach is slowly being expanded to tackle different clinical scenarios including benign conditions such as inflammatory bowel disease and endometriosis. For all of these new indications, it is the desire to access and begin the dissection in native tissue beyond the pathology which makes this approach applicable to other diseases where anatomy can be challenging. Training pathways to safely introduce taTME in a standardized manner are being developed and implemented in a bid to ensure adequate training to all the surgeons using this technique and thus minimize complications and patient morbidity. The future directions of this promising technique include the use of image and optical technological enhancement to aid navigation, the use of pneumorectum stabilization, and perhaps the use of fluorescence as a safety improvement. Developments have come also from the field of robotics. After a demonstration of feasibility in cadaver models, a growing experience has been gathered in the robotic approach to taTME, covered in the last part of this chapter.

Summary of Oncologic and Functional Outcomes

Large cohort and collaborative studies to date have shown that the short-term oncological outcomes appear to be at least as good as traditional laparoscopic surgery. These results need confirmation in randomized controlled trials, which are currently underway (GRECCAR 11 and COLOR III). The functional data on transanal total mesorectal excision is still very scarce and more mature data on quality of life and function outcomes are eagerly awaited.

Total Mesorectal Excision Technique-Past, Present, and Future

While the treatment of rectal cancer is multimodal, above all, a proper oncological resection is critical. The surgical management of rectal cancer has substantially evolved over the past 100 years, and continues to progress as we seek the best treatment. Rectal cancer was historically an unsurvivable disease, with poor understanding of the embryological planes, lymphatic drainage, and lack of standardized technique. Major improvements in recurrence, survival, and quality of life have resulted from advances in preoperative staging, pathologic assessment, the development and timing of multimodal therapies, and surgical technique. The most significant contribution in advancing rectal cancer care may be the standardization and widespread implementation of total mesorectal excision (TME). The TME, popularized by Professor Heald in the early 1980s as a sharp, meticulous dissection of the tumor and mesorectum with all associated lymph nodes through the avascular embryologic plane, has shown universal reproducible reductions in local recurrence and improvement in disease-free and overall survival. Widespread education and training of surgeons worldwide in the TME have significantly impact outcomes for rectal cancer surgery, and the procedure has become the gold standard for curative resection of rectal cancer. In this article, we discuss the evolution of the standard abdominal approach to the TME, with emphasis on the history, relevant anatomy, standard procedure steps, oncologic outcomes, and technical evolution.

Carbon Dioxide Embolism Associated With Transanal Total Mesorectal Excision Surgery: A Report From the International Registries

BACKGROUND

Carbon dioxide embolus has been reported as a rare but clinically important risk associated with transanal total mesorectal excision surgery. To date, there exists limited data describing the incidence, risk factors, and management of carbon dioxide embolus in transanal total mesorectal excision.

OBJECTIVE

This study aimed to obtain data from the transanal total mesorectal excision registries to identify trends and potential risk factors for carbon dioxide embolus specific to this surgical technique.

DESIGN

Contributors to both the LOREC and OSTRiCh transanal total mesorectal excision registries were invited to report their incidence of carbon dioxide embolus. Case report forms were collected detailing the patient-specific and technical factors of each event.

SETTINGS

The study was conducted at the collaborating centers from the international transanal total mesorectal excision registries.

MAIN OUTCOME MEASURES

Characteristics and outcomes of patients with carbon dioxide embolus associated with transanal mesorectal excision were measured.

RESULTS

Twenty-five cases were reported. The incidence of carbon dioxide embolus during transanal total mesorectal excision is estimated to be ≈0.4% (25/6375 cases). A fall in end tidal carbon dioxide was noted as the initial feature in 22 cases, with 13 (52%) developing signs of hemodynamic compromise. All of the events occurred in the transanal component of dissection, with mean (range) insufflation pressures of 15 mm Hg (12-20 mm Hg). Patients were predominantly (68%) in a Trendelenburg position, between 30° and 45°. Venous bleeding was reported in 20 cases at the time of carbon dioxide embolus, with periprostatic veins documented as the most common site (40%). After carbon dioxide embolus, 84% of cases were completed after hemodynamic stabilization. Two patients required cardiopulmonary resuscitation because of cardiovascular collapse. There were no deaths.

LIMITATIONS

This is a retrospective study surveying reported outcomes by surgeons and anesthetists.

CONCLUSIONS

Surgeons undertaking transanal total mesorectal excision must be aware of the possibility of carbon dioxide embolus and its potential risk factors, including venous bleeding (wrong plane surgery), high insufflation pressures, and patient positioning. Prompt recognition and management can limit the clinical impact of such events. See Video Abstract at http://links.lww.com/DCR/A961.

Transanal TME: new standard or fad?

Transanal total mesorectal excision (taTME) has been developed to overcome the difficulty of laparoscopic dissection and transection in the deep pelvis. TaTME has several clinical benefits over laparoscopic surgery, such as better exposure of the distal rectum and direct determination of distal resection margin. Although evidence demonstrating the true benefits of taTME over laparoscopic TME (LapTME) is still insufficient, accumulating data have revealed that, as compared with LapTME, taTME is associated with shorter operative time and a lower conversion rate without jeopardizing other short-term outcomes. However, taTME is a technically demanding procedure with specific complications such as urethral injury, and so sufficient experience of LapTME and step-by-step acquisition of the skills needed for this procedure are requisite. The role of transanal endoscopic surgery is expected to change, along with the recent progress in the treatment of rectal cancer, such as robotic surgery and the watch-and-wait strategy. Optimization of treatment will be needed in the future in terms not only of oncological but also of functional outcomes.

Spin in articles about minimally invasive transanal total mesorectal excision: an assessment of the current literature

AIM

Minimally invasive transanal total mesorectal excision (TaTME) is a new approach for treating rectal cancer. 'Spin' can be defined as 'reporting strategies to highlight that the experimental treatment is beneficial' despite limitations in study design. The aim of this study was to assess spin within publications about TaTME.

METHOD

EMBASE and MEDLINE (2009-2017) were searched for publications assessing TaTME in rectal cancer. All papers published between 2009 and 2017 were eligible for inclusion. Study titles and abstracts were assessed for evidence of spin, as previously defined.

RESULTS

A total of 1202 studies were identified through our search, and 73 were included. The majority were case series (n = 48, 66%). A total of 55 publications (75%) had evidence of spin within at least one domain. The most common type of spin was claiming safety without describing how this was defined or tested (56%). Other strategies included claiming superiority without support (33%) and reporting nonsignificance as equivalence (42%). We did not find that year of publication (P = 0.61), study design (P = 0.60), number of patients (P = 0.85) or declared conflict of interest (P = 0.43) were associated with spin.

CONCLUSION

We have shown that spin is common within studies assessing TaTME for rectal cancer. Despite a lack of support from study results, in the majority of studies authors concluded that TaTME is safe for use in rectal cancer. Readers of study abstracts describing new techniques need to be cautious about accepting the authors' conclusions, especially in case series and observational studies.

Transanal total mesorectal excision for rectal cancer: state of the art

Achieving a high-quality total mesorectal excision (TME) resection specimen is a central tenet of curative rectal cancer management. However, operating at the caudal extremity of the pelvis is inherently challenging and a number of patient- and tumour-related factors may increase the risk of obtaining a poor TME specimen and positive resection margins. Transanal TME (TaTME) is an advanced surgical technique developed to overcome the limitations in pelvic exposure and instrumentation of transabdominal surgery. This up-to-date narrative review describes the evolution of TME surgery, the indications for TaTME, current published outcomes, its limitations and future developments.