Fernando Burdío

Large hepatic ablation with bipolar saline-enhanced radiofrequency: an experimental study in in vivo porcine liver with a novel approach

SUMMARY BACKGROUND DATA Radiofrequency ablation (RFA) is a relatively new technology for the local destruction of liver tumors. Development of recent devices has enabled the creation of larger lesions. Nevertheless, treating liver tumors larger than 2.5 cm in diameter often requires multiple overlapping ablations to encompass the tumor and the surrounding healthy tissue rim with an increasing risk of local recurrence. MATERIAL AND METHODS RFA (480 kHz) of the liver using our method was undertaken on a total number of 15 healthy farm pigs with (Group B, n = 8) or without (Group A, n = 5) the Pringle maneuver via laparotomy. The pigs were followed and euthanized on the seventh day of the experiment. Livers were removed for histological assessment. Time of the procedure, impedance, current, power output, energy output, temperatures in the liver, central temperature of the animal, volume size of the lesion, and delivered energy per lesion volume were determined and compared among groups. Additionally a regularity ratio (RR) was determined by gross examination of the specimen and scored (0-3) taking into account regularity and predictability of the ablation with pathologic assessment. RESULTS With both methods, ellipsoid lesions were created between the two probes. In both groups tissue impedance fell with time (r = -0.47, P < 0.01 and r = -0.34, P < 0.05, in Groups A and B, respectively). The mean lesion size achieved with the Pringle maneuver was the largest lesion size described in the literature for any RFA method in vivo and was greater in Group B than in Group A (123.22 cm(3) +/- 49.62 and 52.40 cm(3) +/- 23.59, respectively, P < 0.05). A better regularity and predictability evaluated by RR was observed in Group B compared to Group A (1.88 +/- 1.35 and 0.40 +/- 0.55, respectively, P < 0.05). Five major complications were described and attributed primarily to failure in isolation from hypertermic lesions. CONCLUSIONS Our new bipolar saline-enhanced electrode with Pringle maneuver achieves large hepatic ablations in in vivo pig liver. These large lesions are well-tolerated by the animal when thermal injuries to adjacent structures are avoided.

Research and development of a new RF-assisted device for bloodless rapid transection of the liver: Computational modeling and in vivo experiments

BackgroundEfficient and safe transection of biological tissue in liver surgery is strongly dependent on the ability to address both parenchymal division and hemostasis simultaneously. In addition to the conventional clamp crushing or finger fracture methods other techniques based on radiofrequency (RF) currents have been extensively employed to reduce intraoperative blood loss. In this paper we present our broad research plan for a new RF-assisted device for bloodless, rapid resection of the liver.MethodsOur research plan includes computer modeling and in vivo studies. Computer modeling was based on the Finite Element Method (FEM) and allowed us to estimate the distribution of electrical power deposited in the tissue, along with assessing the effect of the characteristics of the device on the temperature profiles. Studies based on in vivo pig liver models provided a comparison of the performance of the new device with other techniques (saline-linked technology) currently employed in clinical practice. Finally, the plan includes a pilot clinical trial, in which both the new device and the accessory equipment are seen to comply with all safety requirements.ResultsThe FEM results showed a high electrical gradient around the tip of the blade, responsible for the maximal increase of temperature at that point, where temperature reached 100°C in only 3.85 s. Other hot points with lower temperatures were located at the proximal edge of the device. Additional simulations with an electrically insulated blade produced more uniform and larger lesions (assessed as the 55°C isotherm) than the electrically conducting blade. The in vivo study, in turn, showed greater transection speed (3 ± 0 and 3 ± 1 cm2/min for the new device in the open and laparoscopic approaches respectively) and also lower blood loss (70 ± 74 and 26 ± 34 mL) during transection of the liver, as compared to saline-linked technology (2 ± 1 cm2/min with P = 0.002, and 527 ± 273 mL with P = 0.001).ConclusionA new RF-assisted device for bloodless, rapid liver resection was designed, built and tested. The results demonstrate the potential advantages of this device over others currently employed.

Oncological outcomes of lipofilling breast reconstruction: 195 consecutive cases and literature review

INTRODUCTION Lipofilling has become a widely used procedure in breast reconstruction after mastectomy or breast-conserving treatment. The possibility that this technique may increase stimulation of cancer development between the potential tumor bed and the lipoaspirates grafts has been raised regarding its safety. The aim of this study was to identify the oncological risks associated with this procedure in our institution. METHODS Between years 2007 and 2014 we record 195 consecutive patients with fat grafting technique for reconstructive purpose after breast cancer treatment. The loco-regional recurrence (LRR) as first event of relapse was the primary end point of this study. RESULTS We performed 319 lipofilling procedures in 132 mastectomy and 63 breast-conserving surgery patients. Invasive carcinoma represents 81.6% of the series. The median follow-up from primary cancer surgery and fat grafting was 74 and 31 months respectively. Median time between oncologic surgery and lipofilling was 36 months. The authors observed a complication rate of 8.2%, most of them liponecrosis and oil cysts (7.2%). Four local, 2 regional and 4 distant recurrences were observed as first event of relapse in 10 patients with invasive ductal carcinoma. The loco-regional recurrence rate was 3.1% (1.08% per year). CONCLUSIONS Although larger prospective trials are needed, these results support the fact that lipofilling following breast cancer treatment leads to a very low rate of complications and similar to other authors, it does not seem to interfere in patients oncological prognosis when compared with prior publications.

Improved perfusion system for bipolar radiofrequency ablation of liver: preliminary findings from a computer modeling study

Current systems for radiofrequency ablation of liver tumors are unable to consistently treat tumors larger than 3 cm in diameter with a single electrode in a single application. One of the strategies for enlarging coagulation zone dimensions is to infuse saline solutions into the tissue through the active electrodes. Nevertheless, the uncontrolled and undirected diffusion of boiling saline into the tissue has been associated with irregular coagulation zones and severe complications, mainly due to reflux of saline along the electrode path. In order to improve the perfusion bipolar ablation method, we hypothesized that the creation of small monopolar coagulation zones adjacent to the bipolar electrodes and previous to the saline infusion would create preferential paths for the saline to concentrate on the targeted coagulation zone. Firstly, we conducted ex vivo experiments in order to characterize the monopolar coagulation zones. We observed that they are practically impermeable to the infused saline. On the basis of this finding, we built theoretical models and conducted computer simulations to assess the feasibility of our hypothesis. Temperature distributions during bipolar ablations with and without previous monopolar coagulation zones were obtained. The results showed that in the case of monopolar coagulation zones the temperature of the tissue took longer to reach 100 degrees C. Since this temperature value is related to rise of impedance, and the time necessary for this process is directly related to the volume of the coagulation zone, our results suggest that monopolar sealing would allow larger coagulation zones to be created. Future experimental studies should confirm this benefit.

Laparoscopic Pancreas-Sparing Subtotal Duodenectomy

CONTEXT Primary adenocarcinoma of the duodenum is a rare digestive malignancy which is commonly treated by radical surgical resection, pancreaticoduodenectomy being the technique of choice. Complete tumor resection obtaining free margins should be the standard of treatment for primary adenocarcinoma of the duodenum. Segmental duodenal resection is an appropriate operation for selected cases of primary adenocarcinoma of the duodenum of the 3rd and 4th portions of the duodenum. CASE REPORT We present the case of a 67-year-old woman suffering from an infra-ampullary large villous polypoid mass affecting the 3rd portion of the duodenum. Multiple endoscopic biopsies did not disclose any malignancy, and abdominal CT and endoscopic ultrasound found no extraduodenal involvement. A 3rd and 4th portion pancreas-sparing duodenectomy was carried out using a totally laparoscopic approach. Intra-operatory duodenoscopy was done to safeguard the papilla of Vater. Recovery was uneventful and the patient was discharged on the 7th postoperative day. The final diagnosis was primary adenocarcinoma of the duodenum (free resection margins). After forty-five months of follow-up, the patient is free of disease. CONCLUSIONS We recommend this procedure for treatment of an infra-ampullary benign and pre-malignant duodenal pathology; it can also be a treatment option and an alternative to a pancreaticoduodenectomy in very selected cases of tumors confined to the duodenum. Expertise in both pancreatic surgery and laparoscopic techniques is required.

Assessment of Hyperbolic Heat Transfer Equation in Theoretical Modeling for Radiofrequency Heating Techniques

Theoretical modeling is a technique widely used to study the electrical-thermal performance of different surgical procedures based on tissue heating by use of radiofrequency (RF) currents. Most models employ a parabolic heat transfer equation (PHTE) based on Fourier’s theory, which assumes an infinite propagation speed of thermal energy. We recently proposed a one-dimensional model in which the electrical-thermal coupled problem was analytically solved by using a hyperbolic heat transfer equation (HHTE), i.e. by considering a non zero thermal relaxation time. In this study, we particularized this solution to three typical examples of RF heating of biological tissues: heating of the cornea for refractive surgery, cardiac ablation for eliminating arrhythmias, and hepatic ablation for destroying tumors. A comparison was made of the PHTE and HHTE solutions. The differences between their temperature profiles were found to be higher for lower times and shorter distances from the electrode surface. Our results therefore suggest that HHTE should be considered for RF heating of the cornea (which requires very small electrodes and a heating time of 0.6 s), and for rapid ablations in cardiac tissue (less than 30 s).

A new single-instrument technique for parenchyma division and hemostasis in liver resection: a clinical feasibility study

The objective of this study was to evaluate the clinical feasibility of a new technique for liver resection based on a radiofrequency-assisted (485 kHz) device that has shown high performance in the animal setting in both transection speed and blood loss per transection area. Eight patients with colorectal hepatic metastasis underwent 11 partial hepatectomies using the proposed technique for both parenchyma division and hemostasis. Main outcome measures were blood loss per transection area and transection speed. No other instruments (including sutures or clips) were used in any of the cases; temporary vascular occlusion performed was not performed. No blood transfusions were required and no mortality or morbidity linked to the hepatic procedure were observed. The median blood loss per transection area and the median transection speed were .79 mL/cm² (range, .05-7.37 mL/cm²) and 1.28 cm²/min (range, .49-1.87 mL/cm²), respectively. During the follow-up period (range, 4-12 mo) no late complications were detected and postoperative patients were free from hepatic recurrence. The proposed radiofrequency-assisted device was shown to achieve parenchymal division and hemostasis simultaneously, resulting in extremely reduced blood loss.

RF tumor ablation with internally cooled electrodes and saline infusion: what is the optimal location of the saline infusion?

BackgroundRadiofrequency ablation (RFA) of tumors by means of internally cooled electrodes (ICE) combined with interstitial infusion of saline may improve clinical results. To date, infusion has been conducted through outlets placed on the surface of the cooled electrode. However, the effect of infusion at a distance from the electrode surface is unknown. Our aim was to assess the effect of perfusion distance (PD) on the coagulation geometry and deposited power during RFA using ICE.MethodsExperiments were performed on excised bovine livers. Perfusion distance (PD) was defined as the shortest distance between the infusion outlet and the surface of the ICE. We considered three values of PD: 0, 2 and 4 mm. Two sets of experiments were considered: 1) 15 ablations of 10 minutes (n ≥ 4 for each PD), in order to evaluate the effect of PD on volume and diameters of coagulation; and 2) 20 additional ablations of 20 minutes. The effect of PD on deposited power and relative frequency of uncontrolled impedance rises (roll-off) was evaluated using the results from the two sets of experiments (n ≥ 7 for each PD). Comparisons between PD were performed by analysis of variance or Kruskal-Wallis test. Additionally, non-linear regression models were performed to elucidate the best PD in terms of coagulation volume and diameter, and the occurrence of uncontrolled impedance rises.ResultsThe best-fit least square functions were always obtained with quadratic curves where volume and diameters of coagulation were maximum for a PD of 2 mm. A thirty per cent increase in volume coagulation was observed for this PD value compared to other values (P < 0.05). Likewise, the short coagulation diameter was nearly twenty five per cent larger for a 2 mm PD than for 0 mm. Regarding deposited power, the best-fit least square function was obtained by a quadratic curve with a 2 mm PD peak. This matched well with the higher relative frequency of uncontrolled impedance rises for PD of 0 and 4 mm.ConclusionSaline perfusion at around 2 mm from the electrode surface while using an ICE in RFA improves deposition of energy and enlarges coagulation volume.

Distant infusion of saline may enlarge coagulation volume during radiofrequency ablation of liver tissue using cool-tip electrodes without impairing predictability.

OBJECTIVE Our aim was to evaluate the capability of a Cool-tip electrode to create larger coagulation volumes combined with a low-flow (0.1 mL/min) perfusion of hypertonic saline at a distance of 2 mm (hybrid applicator) without reducing either predictability or sphericity of the coagulation zone. MATERIALS AND METHODS A total of 48 radiofrequency ablations were performed on a total of 12 adult pigs: 24 with the Cool-tip (group 1) and 24 with the hybrid applicator (group 2). Volumes and diameters were assessed both macroscopically and with imaging techniques (ultrasound and MRI). Digital reconstruction techniques were also used. Reproducibility of the coagulations was assessed by means of the coefficient of variation. RESULTS The macroscopic assessment showed a significantly larger coagulation zone in group 2 than in group 1, both with (19.40 ± 11.38 cm(3) vs 9.16 ± 5.62 cm(3); p < 0.001) and without (19.54 ± 11.39 cm(3) vs 9.21 ± 5.74 cm(3); p < 0.001) digital reconstruction. Differences were also significant in the MRI assessment. The minimum transverse diameter was also significantly (p < 0.01) larger in group 2 than group 1: 2.46 ± 0.61 versus 1.86 ± 0.55 cm for macroscopic assessment, 2.33 ± 0.96 versus 1.69 ± 0.53 cm for ultrasound, and 2.41 ± 0.58 versus 1.8 ± 0.52 cm for MRI. The coefficient of variation was similar in both groups. CONCLUSION The results suggest that low-flow perfusion of hypertonic saline at 2 mm from a Cool-tip electrode could increase coagulation zone volume without reducing predictability.

Influence of approach on outcome in radiofrequency ablation of liver tumors

In this article some recent data concerning the approach on radiofrequency ablation (RFA) of liver tumors are reviewed. Specifically, several critical statements between surgical and percutaneous approach are raised and discussed: (1) Open approach may lead to a higher complication rate; (2) Temporary occlusion of hepatic inflow during surgical approach may lead to a higher rate of ablation of the liver tumors; (3) Surgical approach may permit better targeting of the tumor to be ablated. (4) Surgical approach may discover additional liver tumors. Finally, several conclusions and recommendations are also addressed.