The two energy sources for bipolar device compared in this study included LigaSure™ V Lap System (Valleylab, Boulder, CO) and the novel bipolar QMR electrical energy generator. The QMR energy generator produces a specific form of waves with the combination of 4 MHz and its components of high-frequency. The laparoscopic jaw of LigaSure™ was used to switch between the two energy sources. Each device was used in a surgical experiment and evaluated by basic ligation performance, microscopic tissue effects, and surgeon experience in the laparoscopic environment.
Open surgery experiment
1) Animals and procedures
A total of three abdominal aortas from three adult male rabbits were used. All the rabbits were New Zealand white rabbits (Oryctolagus cuniculus) and all weighed 3.6 kg.
Anesthesia was performed using an intramuscular injection of glycopyrrolate (0.01 mg/kg) and intravascular injection of propofol (1.5 mg/kg). Animals were positioned in dorsal recumbency and prepared for aseptic surgery. The abdomen was incised to expose the abdominal aorta. Vascular ligation was performed by applying LigaSure™ or QMR electrosurgical instruments to the abdominal aorta in the distal and proximal directions. A total of 11 ligations was conducted, six times using LigaSure™ and five times using the QMR energy source.
2) Measurements
The outer diameter of the abdominal aorta was measured before the ligations, and time to sealing, peak tissue temperature, and burst pressure of sealed vessels were measured during and after the ligations. Among the three rabbits, burst pressure was measured using the aorta of two rabbits, and the other aorta was histologically analyzed. The burst pressure was measured by instilling normal saline into both ends of the vessel lumen. Using a previously described technique [7], pressure was slowly increased until the vessel leaked. Histological analyses were performed on both proximal and distal portions of the sealing site (Fig. 1). Each sealed vessel was processed for staining with Masson trichrome stain and hematoxylin and eosin stain. Histological analysis was performed on the following items (Fig. 2a and 2b): seal width (width of ligation site), adventitial collagen denaturation (length of denatured collagen in the total collagen surrounding the vascular outer membrane of both ligature sites), wall layer cleavage (portion of the whole blood vessel walls on both sides of the ligation site where layer separation occurred, as indicated by qualitative evaluation), and wall injury (ligation site including the length of the entire vessel wall length of damaged blood vessels, expressed as numerical qualitative value). At the time of ligation, the temperature of the surrounding tissue was measured using a thermal imaging camera. While applying energy to the abdominal aorta, a video was acquired using a thermal imaging camera (FLIR-T62101, FLIR Systems, USA). The stored images were analyzed using a temperature analysis program (FLIR R & D software 3.3, FLIR Systems, USA).
Laparoscopic surgery: surgeons' experience
1) Animals and Laparoscopic simple nephrectomy
Two female pigs (conventional farm pigs weighing 40 kg) were used and underwent bilateral laparoscopic simple nephrectomy. Pigs were pretreated by intramuscular injection of rompun (2 mg/kg) and zoletil (10 mg/kg), intubated, and maintained under general anesthesia using 2.5% enflurane and 100% O2. Animals were placed in a left lateral decubitus position, and CO2 was injected to form a pneumoperitoneum on the side of the papilla at the umbilical level. CO2 was injected into the abdominal cavity at a rate of 3–5 L/min, and the intraperitoneal pressure was maintained at 12 mmHg during surgery. A 12 mm camera port was inserted and two 5 mm ports were inserted between the umbilical region below the lateral rib of the camera port and the outside of the anterior superior iliac spine, respectively. After placement of the port, the abdominal organs and fascia were incised as in conventional procedures of simple nephrectomy, exposing the kidney to secure the blood vessels. Then vascular ligation was performed using laparoscopic energy-based devices. By dissecting into the pelvic cavity along the lateral part of the colon, the peritoneum and ureters were dissected and ligated with the device. After left side laparoscopic nephrectomy was performed, we reversed the position and performed the right side laparoscopic nephrectomy with the other energy-based device.
2) Measurements
All laparoscopic surgical procedures were recorded and divided into video clips of ligation of three types of tissue (peritoneum, renal vein, and ureter). Six experienced urologic surgeons watched randomly mixed video clips in a single-blind condition and scored each clip according to the evaluation criteria in Table 1. The surgeons’ experiences regarding surgical smoke, carbonization, and stickiness of tissue to the device were measured according to the established criteria (Table 1).
Table 1
Criteria in the surgeon's experience during laparoscopic surgery
1. Amount of surgical smoke formation |
Grade | Evaluation criteria |
0 | No smoke formation |
1 | Mild smoke formation but no visual interference |
2 | Moderate smoke formation, must be removed to increase visibility |
3 | Severe smoke formation, difficult to proceed with surgery |
2. Tissue carbonization |
Grade | Evaluation criteria |
0 | No carbonization |
1 | Mild carbonization, brown-colored tissue observed |
2 | Moderate carbonization, blackened tissue observed |
3 | Severe carbonization, all tissue is black |
3. Stickiness |
Grade | Evaluation criteria |
1 | No stickiness |
2 | Stick a little but falls off by itself |
3 | Must be removed by holding the tissue with the opposite hand but involves no tissue damage |
4 | Sticking caused damage tissue but no bleeding |
5 | Sticking is severe and produces tissue damage and bleeding when removing the instrument |
Statistical analysis
The groups were compared using Fisher's exact test for categorical variables and Student’s t-test for continuous variables. Statistical analyses were performed using SPSS® (version 21.0, SPSS Inc., Chicago, IL, USA). All p-values were two-sided, and p < 0.05 was considered statistically significant.