Development of an in vivo tumor-mimic model for learning radiofrequency ablation.

Radiofrequency ablation requires accurate probe placement using ultrasound guidance. The purpose of this study was to develop an in vivo tumor-mimic model for learning open and laparoscopic radiofrequency ablation. Tumor-mimics were created in ex vivo porcine livers by injecting a mixture of 3% agarose, 3% cellulose, 7% glycerol, and 0.05% methylene blue, which formed 1 cm hyperechoic, discrete lesions on ultrasound. Open and laparoscopic (using a box-trainer) ablation techniques were practiced. In vivo experiments were then conducted in 10 pigs. Three tumor-mimics were created in each animal using a laparoscopic approach. Lesions were characterized sonographically, ablated using an open (n = 5) or laparoscopic (n = 5) approach, and examined pathologically. An ablation in normal liver tissue was performed as a control. Tissue impedance was recorded. Target creation took 81 minutes per animal and 96% of injections were successful. Tissue impedance (48.8 +/- 5.8 vs. 49.6 +/- 5.4) and ablation size (25.1 +/- 3.4 vs. 24.3 +/- 5.1) were not significantly different for controls (n = 8) and tumor-mimics (n = 26), respectively. One animal died of a pulmonary embolism following injection of agarose into a hepatic vein. The agarose-based tissue-mimic creates realistic sonographic targets for learning ultrasound-guided open and laparoscopic radiofrequency ablation in an in vivo model.

Laparoscopic skills training.

BACKGROUND: The purpose of this study was to quantify the learning curve of a previously validated laparoscopic skills curriculum. METHODS: Second-year medical students (MS2, n = 11) and second (PGY2, n = 11) and third (PGY3, n = 6) year surgery residents were enrolled into a curriculum using five video-trainer tasks. All subjects underwent baseline testing, training (30 minutes per day for 10 days), and final testing. Scores were based on completion time. The relationship between task completion time and the number of practice repetitions was examined. Improvement (the difference in baseline and final performance) amongst groups was compared by one-way analysis of variance using the baseline score as a covariate; P <0.05 indicated significance. RESULTS: Baseline scores were not significantly different. Final scores were significantly better for MS2s versus PGY3s. Adjusted-improvement was significantly larger for the MS2s compared with PGY2s and PGY3s, and for PGY2s compared with PGY3s. The mean number of repetitions corresponding to a predicted 90th percentile score was 32. CONCLUSION: Inexperienced subjects benefit the most from skills training. For maximal benefit, we recommend that each task be practiced for at least 30 to 35 repetitions.

Lichtenstein inguinal herniorrhaphy using sutures versus tacks.

The Lichtenstein hernia repair has become a popular technique for most inguinal hernias performed in the United States. One attempt to improve on this technique includes the use of a tacker instead of suturing the mesh. This study compared the feasibility and time saving for placement of mesh for open inguinal hernias with a tacker versus polypropylene suture.Thirty-four patients were prospectively randomized to undergo open hernia repair using either running 2-0 polypropylene suture or a tacker device that contained spiral titanium tacks. Patients were examined after 1 week and followed for a mean of 8 months (range 1-26 months) to record postoperative complications and technical failure rate. Mesh placement times were significantly shorter in the tacker group (9.0+/-3.5 min) than the suture group (30.9+/-9.9 min). No technical complications or recurrences were found in the follow-up period in either group.Securing mesh with the tacker is safe, and repair appears durable at short-term follow-up. Using the tacker on open inguinal hernia repairs shortens the time for mesh placement compared to suture fixation. Decreased operative time may reduce overall cost.

Leukocyte nitroblue tetrazolium test and chemotaxis in children with nephrotic syndrome and nephritis.

Patients with nephrotic syndrome have an increased incidence of infection; the cause of this is unknown. It is recognized that neutrophils play an important role in the protection of the body against bacteria. In an attempt to evaluate the function of neutrophils in various categories of nephritis, and that function's relationship in response to steroid therapy in the idiopathic nephrotic syndrome, a study using peripheral blood neutrophils on nitroblue tetrazolium test (NBT) and chemotaxis was performed in 62 children suffering from nephritis during its acute phase and remission. These patients included minimal change nephrotic syndrome (MCNS), 9 cases; focal segmental glomerular sclerosis (FGS), 3 cases; mesangial cell proliferative nephropathy (MesPGN), 23 cases; hepatitis B antigenemia associated with membranous glomerulonephropathy (HBSMGN), 4 cases; poststreptococcal glomerulonephritis (AGN), 20 cases and chronic glomerulonephritis (CGN), 3 cases. The NBT reduction levels were significantly increased in the MCNS and AGN groups during the acute nephrotic or nephritic phase and returned to normal range in remission. The chemotactic index significantly decreased in the MCNS and significantly increased in the MesPGN cases; in the remission stage, they returned to normal range. All cases of MesPGN in this study were nephrotic syndrome with frequent relapse or were steroid non-responsive. These results suggest that, except for MCNS, the higher incidence of infection in nephrotic syndrome has no relation to neutrophil chemotaxis and NBT in various categories of nephritis. However, the chemotactic index may serve as one of the parameters between steroid responsive and non-responsive nephrotic syndromes.

Accuracy and effectiveness of laparoscopic vs open hepatic radiofrequency ablation.

BACKGROUND: The purpose of this study was to compare the accuracy (in terms of ultrasound-guided probe placement) and the effectiveness (in terms of pathologic tumor-free margin) of laparoscopic vs open radiofrequency (RF) ablation. METHODS: Using a previously validated tissue-mimic model, 1-cm simulated hepatic tumors were ablated in 10 pigs randomized to open or laparoscopic techniques. Energy was applied until tissue temperature reached 100 degrees C (warm-up) and thereafter for 8 min. A pathologist blinded to technique examined all specimens immediately after treatment. Analysis was by Fisher's exact test and the Mann-Whitney U test; p < 0.05 was considered significant. RESULTS: Off-center distance (3.5 +/- 1.6 vs 4.2 +/- 1.4 mm), size (24.7 +/- 3.1 vs 25.6 +/- 3.8 mm), symmetry (40% vs 73%), margin positivity (33% vs 9%), and margin distance (1.1 +/- 1.2 vs 2.2 +/- 1.6 mm) were not significantly different between laparoscopic (n = 15) and open (n = 11) ablations, respectively. The proportion of round/ovoid lesions (20% vs 64%) was lower (p = 0.043), and warm-up time (20.2 +/- 14.0 vs 10.7 +/- 7.5) was longer (p = 0.049) for the laparoscopic than for the open groups, respectively. CONCLUSION: Accurate probe placement can be achieved using laparoscopic and open RF ablation techniques. The physiologic effects of laparoscopy may alter ablation shape and warm-up time. Additional studies are needed to establish effective ways of achieving complete tumor destruction.