Kai S. Lehmann

The German Registry for Natural Orifice Translumenal Endoscopic Surgery: Report of the First 551 Patients

Objective:To analyze patient outcome in the first 14 months of the German natural orifice translumenal endoscopic surgery (NOTES) registry (GNR). Summary Background Data:NOTES is a new surgical concept, which permits scarless intra-abdominal operations through natural orifices, such as the mouth, vagina, rectum, or urethra. The GNR was established as a nationwide outcome database to allow the monitoring and safe introduction of this technique in Germany. Methods:The GNR was designed as a voluntary database with online access. All surgeons in Germany who performed NOTES procedures were requested to participate in the registry. The GNR recorded demographical and therapy data as well as data on the postoperative course. Results:A total of 572 target organs were operated in 551 patients. Cholecystectomies accounted for 85.3% of all NOTES procedures. All procedures were performed in female patients using transvaginal hybrid technique. Complications occurred in 3.1% of all patients, conversions to laparoscopy or open surgery in 4.9%. In cholecystectomies, institutional case volume, obesity, and age had substantial effect on conversion rate, operation length, and length of hospital stay, but no effect on complications. Conclusions:Despite the fact that NOTES has just recently been introduced, the technique has already gained considerable clinical application. Transvaginal hybrid NOTES cholecystectomy is a practicable and safe alternative to laparoscopic resection even in obese or older patients.

A Prospective Randomized Study to Test the Transfer of Basic Psychomotor Skills From Virtual Reality to Physical Reality in a Comparable Training Setting

Objective:To test whether basic skills acquired on a virtual endoscopic surgery simulator are transferable from virtual reality to physical reality in a comparable training setting. Summary Background Data:For surgical training in laparoscopic surgery, new training methods have to be developed that allow surgeons to first practice in a simulated setting before operating on real patients. A virtual endoscopic surgery trainer (VEST) has been developed within the framework of a joint project. Because of principal limitations of simulation techniques, it is essential to know whether training with this simulator is comparable to conventional training. Methods:Devices used were the VEST system and a conventional video trainer (CVT). Two basic training tasks were constructed identically (a) as virtual tasks and (b) as mechanical models for the CVT. Test persons were divided into 2 groups each consisting of 12 novices and 4 experts. Each group carried out a defined training program over the course of 4 consecutive days on the VEST or the CVT, respectively. To test the transfer of skills, the groups switched devices on the 5th day. The main parameter was task completion time. Results:The novices in both groups showed similar learning curves. The mean task completion times decreased significantly over the 4 training days of the study. The task completion times for the control task on Day 5 were significantly lower than on Days 1 and 2. The experts’ task completion times were much lower than those of the novices. Conclusions:This study showed that training with a computer simulator, just as with the CVT, resulted in a reproducible training effect. The control task showed that skills learned in virtual reality are transferable to the physical reality of a CVT. The fact that the experts showed little improvement demonstrates that the simulation trains surgeons in basic laparoscopic skills learned in years of practice.

Outcome of patients with acute sigmoid diverticulitis: Multivariate analysis of risk factors for free perforation

BACKGROUND Sigmoid diverticulitis (SD) is common in the West; its incidence is increasing as the average age of the population increases. The aim of this study was to assess the clinical outcomes of patients with acute SD and to determine whether emergency operation was associated more often with previous episodes of acute diverticulitis. METHODS All consecutive patients admitted for acute SD were recruited prospectively over an 11-year period from January 1998 to December 2008. Multiple logistic regression was used to identify risk factors for free perforation. RESULTS We included 934 patients (490 men and 444 women; median age, 59.2 years): 450 (48.2%) presented for their first SD episode and 484 (51.8%) had a prior history of SD. Free perforation occurred in 152 patients: during the first episode of SD in 114 patients (25.3%), during the second in 29 (12.7%), during the third in 8 (5.9%), and during the fifth in 1 patient (0.9%; P < .001). No patient with >5 previous episodes of SD had free perforation. All 152 patients with free perforation required emergent operative intervention. After initial conservative therapy in 782 patients, 82 required early elective operative intervention owing to exacerbation of infection under antibiotic treatment. Late elective colectomy was performed in 299 patients during the inflammation-free interval, and operative intervention was recommended in 345 patients owing to complicated diverticulitis. Uncomplicated SD in 56 patients was managed conservatively. Comorbidity (>1 disorder) and the first episode of SD were identified as risk factors for free perforation on multiple logistic regression. CONCLUSION The risk of free perforation in acute SD decreases with the number of previous episodes of SD. The first episode thus is the most dangerous for a free perforation. The indication for colectomy should not be made based on the potential risk of free perforation.

Influence of intrahepatic vessels on volume and shape of percutaneous thermal ablation zones: in vivo evaluation in a porcine model.

Objectives:Aim of the study was to evaluate the precise influence of different intrahepatic vessels, vessel sizes, and distances from the applicator on volume and shape of hepatic laser ablation zones in an in vivo porcine model. Materials and Methods:The study was approved by the institutional animal care and use committee. Eighteen computed tomography-guided Nd:YAG laser ablations were performed in the livers of 10 pigs at varying distances from hepatic veins and portal fields. After hepatectomy the livers were cut into 2-mm slices perpendicular to the laser applicator axes. For each ablation zone the maximum achievable (ideal) volume, the segmented (real) volume, the maximum radius, and the radius at the position of adjacent hepatic vessels were determined. The shapes of the ablation zones were evaluated qualitatively. Comparative statistics using the unpaired t test and a multiple linear regression analysis were performed. Results:Ideal and real ablation zone volumes differed by 27.3% (8.6 ± 1.5 mL vs. 6.4 ± 1.1 mL; P < 0.0001). Thirty-eight of 60 (63%) hepatic veins versus 28 of 31 (90%) portal veins within the central slices of the 18 ablation zones led to a reduction of the ablation zones radius, depending on the distance between the vessel and the applicator and the vessel type. Portal fields revealed stronger effects than hepatic veins. The vessel diameter showed no independent effect (P > 0.05). When influencing, all hepatic veins showed a focal indentation whereas portal fields always showed broad flattening of the ablation zone. Conclusions:Portal fields lead to more heat sink than hepatic veins. The effects decreased with the distance between vessel and applicator tip, but less so for portal fields. The 2 vessel types induced considerably different shape alterations of the ablation zones. These results were not dependent on vessel size. This should be considered in the planning of thermal tumor ablations.

Impact of sleep deprivation on medium-term psychomotor and cognitive performance of surgeons: prospective cross-over study with a virtual surgery simulator and psychometric tests.

BACKGROUND Despite recent work hour restrictions, 24-hour calls remain an important part of patient care. The aim of this study was to assess the impact of 24-hour night calls on the psychomotor and cognitive skills of surgeons with a virtual surgery simulator (VSS) and psychometric tests. We hypothesized that sleep loss impairs surgical skills and concentration performance. METHODS Seventeen surgery residents (test group) and 13 medical students (reference group) performed a 5-day training program on the VSS. The test group was then assessed during a night call on 4 test points (8 am and 4 pm on the on-call day, 8 am on the postcall day, and 8 am on the recovery day) to assess the effects of sleep loss on these surgery residents. The reference group performed the same tests but without a night call. RESULTS The training resulted in a homogenous performance level for both groups. The average time for the test group was 26 minutes. The analysis between rested and sleep-deprived participants (6.5 +/- 0.9 vs 2.9 +/- 1.4 hours of night sleep) in the on-call part showed no performance differences. No impairment was found for the VSS and the cognitive tests within the test group between the start of the working day and the start of the postcall day after the night of relative sleep loss. The subgroup analysis showed no significant differences regarding the amount of night sleep and laparoscopic experience. CONCLUSION No performance impairment was found for surgeons with a VSS and standardized cognitive tests after a night of relative sleep loss. Although there is no doubt that sleep deprivation ultimately impairs human functioning, typical surgical skills do not necessarily deteriorate with a limited amount of sleep loss under clinical conditions.

Natural-orifice transluminal endoscopic surgery (NOTES) in Europe: summary of the working group reports of the Euro-NOTES meeting 2010.

The fourth Euro-NOTES workshop took place in September 2010 and focused on enabling intensive scientific dialogue and interaction between participants to discuss the state of the practice and development of natural-orifice transluminal endoscopic surgery (NOTES) in Europe. Five working groups were formed, consisting of participants with varying scientific and medical backgrounds. Each group was assigned to an important topic: the correct strategy for dealing with bacterial contamination and related complications, the question of the ideal entry point and secure closure, interdisciplinary collaboration and indications, robotics and platforms, and matters related to training and education. This review summarizes consensus statements of the working groups to give an overview of what has been achieved so far and what might be relevant for research related to NOTES in the near future.

Preoperative CT staging in sigmoid diverticulitis—does it correlate with intraoperative and histological findings?

PurposeThis study was designed to evaluate whether the computed tomography (CT) reflects the extent of the inflammation in sigmoid diverticulitis (SD) in order to draw conclusions for selecting the appropriate treatment.MethodsTwo hundred four patients who underwent resection for SD from January 2003 to December 2008 were included. The preoperative CT stage was compared with intraoperative and histological findings. Patients were classified into phlegmonous (Hansen–Stock IIa), abscess-forming (HS IIb), and free perforated (HS IIc) forms of SD. Patients with a recurrent type of diverticulitis were excluded.ResultsIn the phlegmonous type (HS IIa; n = 75), we found a correlation with the preoperative stage in 52% (intraoperative) and 56% (histological), an understaging in 12% (intraoperative) and 11% (histological), and an overstaging in 36% (intraoperative) and 33% (histological). In the abscess-forming type (HS IIb, Hinchey I/II; n = 87), we found conformity in 92% (intraoperative) and 90% (histological), understaging in 3% (intraoperative) and 0% (histological), and overstaging in 5% (intraoperative) and 10% (histological). In the presence of a free perforation (HS IIc, Hinchey III/IV; n = 42), we saw conformity in 100% (intraoperative and histological). The positive predictive value for correctly diagnosing of phlegmonous type (HS IIa), abscess-forming type (HS IIb), and free perforation (HS IIc) by CT was intraoperatively (histologically) 52% (56), 92% (90), and 100% (100), respectively.ConclusionsThe CT is one of the most accurate methods for staging in SD. However, in the phlegmonous type (HS IIa), it leads to an overestimation of the findings in every third patient. It must be clarified whether this pronounced low inflammation should really be regarded as a complicated form of SD. In contrast, the abscess-forming (HS IIb) and free perforated (HS IIc) type of complicated SD is very well reflected by CT.

Determination of the temperature-dependent electric conductivity of liver tissue ex vivo and in vivo: Importance for therapy planning for the radiofrequency ablation of liver tumours

Introduction: Knowledge about the changes in the electric conductivity during the coagulation process of radiofrequency ablation of the liver is a prerequisite for the predictability of produceable thermonecrosis in the liver. Materials and methods: Continuous measurements of the electric conductivity σ in ex vivo porcine liver (n = 25) were done during the coagulation and cooling process at the temperature range of the radiofrequency ablation at a frequency of 470 kHz relevant for the radiofrequency ablation. Measurements of the electric conductivity were performed in both perfused porcine liver (n = 3) and a human surgical specimen from a colorectal liver metastasis. Results: At a body temperature of 37°C, conductance σ was 0.41 siemens per metre (0.32 S/m; 0.52 S/m). Conductance σ increased continuously and uniformly at a temperature of 77°C. Maximum conductance σ with 0.79 S/m (0.7 S/m; 0.87 S/m) was reached at 80°C. A continuous reduction of conductance was observed during the cooling phase. At 37°C, the specific conductance σ in the healthy perfused porcine liver was 0.52 S/m, 0.55 S/m and 0.57 S/m (mean 0.55 S/m). The electric conductivity of the human colorectal liver metastasis was clearly higher. Conclusion: Changes in the specific conductivity during the coagulation and the cooling phase play an important role for the produceable size of a coagulation necrosis and necessitates an adaptation of the therapy parameters during radiofrequency ablation.

Optical properties of adenocarcinoma and squamous cell carcinoma of the gastroesophageal junction

Photodynamic therapy (PDT) is an alternative to radical surgical resection for T1a or nonresectable carcinomas of the gastroesophageal junction. Besides the concentration of the photosensitizer, the light distribution in tissue is responsible for tumor destruction. For this reason, knowledge about the behavior of light in healthy and dysplastic tissue is of great interest for careful irradiation scheduling. The aim of this study is to determine the optical parameters (OP) of healthy and carcinomatous tissue of the gastroesophageal junction in vitro to provide reproducible parameters for optimal dosimetry when applying PDT. A total of 36 tissue samples [adenocarcinoma tissue (n=21), squamous cell tissue (n=15)] are obtained from patients with carcinomas of the gastroesophageal junction. The optical parameters are measured in 10-nm steps using new integrating sphere spectrometers in the PDT-relevant wavelength range of 300 to 1140 nm and evaluated by inverse Monte-Carlo simulation. Additional examinations are done in healthy tissue from the surgical safety margin. In the wavelength range of frequently applied photosensitizers at 330, 630, and 650 nm, the absorption coefficient in tumor tissue (adenocarcinoma 1.22, 0.16, and 0.15 mm(-1); squamous cell carcinoma 1.48, 0.13, and 0.11 mm(-1)) is significantly lower than in healthy tissue (stomach 3.34, 0.26, and 0.20 mm(-1); esophagus 2.47, 0.21, and 0.18 mm(-1)). The scattering coefficient of all tissues decreases continuously with increasing wavelength (adenocarcinoma 22.8, 12.99, and 12.52 mm(-1); squamous cell carcinoma 19.44, 9.35, and 8.98 mm(-1); stomach 20.55, 13.96, and 13.94 mm(-1); esophagus 20.34, 12.56, and 12.22 mm(-1). All tissues show an anisotropy factor between 0.80 and 0.94 over the entire spectrum. The maximum optical penetration depth for all tissues is achieved in the range of 800 to 1100 nm. At the wavelength range of 330, 630, and 650 nm, the optical penetration depth is significantly higher in carcinoma tissue (adenocarcinoma 0.27, 1.54, and 1.66 mm; squamous cell carcinoma 0.23, 1.71, and 1.84 mm) than in healthy tissue (stomach 0.16, 1.10, and 1.26 mm; esophagus 0.17, 1.47, and 1.65 mm; p<0.05). Above 1000 nm, a higher absorption coefficient of tumor tissue results in a lower optical penetration depth than in healthy tissue (p<0.05). The higher absorption and scattering of the tumor tissue in the wavelength range of available photosensitizer is associated with a low optical penetration depth. This necessitates higher energy doses and long application times or repeated applications to effectively treat large tumor volumes. Photosensitizers optimized for larger wavelength range need to be developed to increase the efficacy of PDT.

The vascular cooling effect in hepatic multipolar radiofrequency ablation leads to incomplete ablation ex vivo

Abstract Purpose: Major limitations of conventional RFA are vascular cooling effects. However, vascular cooling effects are supposed to be less pronounced in multipolar RFA. The objective of this ex vivo study was a systematic evaluation of the vascular cooling effects in multipolar RFA. Materials and methods: Multipolar RFA with three bipolar RFA applicators was performed ex vivo in porcine liver (applicator distance 20 mm, energy input 40 kJ). A saline-perfused glass tube (‘vessel’) was placed parallel to the applicators in order to simulate a natural liver vessel. Five applicator-to-vessel geometries were tested. A liquid-filled glass tube without perfusion was used as a dry run. Ablations were orthogonally cut to the applicators at a defined height. Cooling effects were analysed qualitatively and quantitatively along these cross sectional areas. Results: Thirty-six ablations were performed. A cooling effect could be seen in all ablations with perfused vessels compared to the dry run. While this cooling effect did not have any influence on the ablation areas (859–1072 mm2 versus 958 mm2 in the dry run, p > 0.05), it had a distinctive impact on ablation shape. A vascular cooling effect could be observed in all ablations with perfusion directly around the vessel independent of the applicator position compared to the dry run (p < 0.01). Conclusions: A vascular cooling effect occurred in all multipolar RFA with simulated liver vessels ex vivo independent of the applicator-to-vessel geometry. While the cooling effect did not influence the total ablation area, it had a distinctive impact on the ablation shape.