Laparoscopic bowel resection: a comparison of three ultrasonically activated devices.

BACKGROUND AND OBJECTIVES: To compare resection time and collateral thermal damage of 3 currently available ultrasonically activated devices in laparoscopic small bowel surgery.
METHODS: AutoSonix, SonoSurg, and UltraCision were compared in laparoscopic small bowel mesentery resection in a porcine model. A resection was defined as 12 endarcade arteries supplying the intended bowel segment. Vssels were divided 1 cm off the bowel wall. AutoSonix, SonoSurg, and UltraCision were comparable for blade length and type, cutting mechanism, handle ergonomics, and vibration amplitude, but not well matched for vibration frequency (55.5;23.5;55.5 kHz), working shaft diameter (5;11;10 mm) and length (29;33;34 cm), respectively. A sample size of 114 was calculated to detect a 25% difference with 90% power at a 5% significance level. Resections were allocated to devices by block randomization. Analysis of variance and pairwise Scheffe tests were used for multiple comparisons, and a Kaplan-Meier plot was drawn to confirm differences in resection time with each device. A pathologist blind to the devices evaluated bowel wall biopsies for thermal damage.
RESULTS: Procedures as allocated comprised 114 resections (38 with each device). UltraCision median resection time of 5160 (range 2340-7860) seconds was significantly longer (P=0.0001). The difference in resection time between AutoSonix (median 3420, range 1860-8760 s) and SonoSurg (median 3660, range 1800-6900 s) did not reach statistical significance. A microscopy revealed no thermal damage.
CONCLUSIONS: Laparoscopic resection time for porcine bowel mesentery was shorter with AutoSonix or SonoSurg than with UltraCision, and no thermal damage to the bowel wall was found.

INTRODUCTION

The implementation of laparoscopic surgery during the past decade has made surgeons more aware of several quality control issues raised by the widespread use of energy-based surgery.[1] Multi-functionality and reduced heat production are among the appealing features that have made ultrasonically activated surgery (UAS) emerge in the laparoscopic setting.[2] The former, which allows coagulation, cutting, dissection, and grasping, minimizes the need for frequent instrument changes and contributes to contain operating time. The latter has been lately confirmed in open[3] and laparoscopic[4] porcine models, although similar data from the epidermis were reported in the late 1980s.[5] The evidence available so far seems to be in support of the assumption that reduced heat production may minimize collateral thermal tissue damage.[3,4] Within the context of the interaction between implementation of laparoscopic surgery and awareness of quality control issues an impressive empowerment has occurred in the currently available ultrasonically activated devices.[2] The aim of the present experimental study was to compare resection time and collateral thermal damage of 3 ultrasonically activated devices in laparoscopic small bowel surgery in a porcine model.

MATERIAL AND METHODS

Domestic Norwegian pigs weighing approximately 40 kg were preanesthetized with intramuscular ketamine (10mg/kg) and ventilated with halothane via tracheostomy. Through the same neck incision, the right carotid artery was catheterized to allow monitoring of blood pressure and heart rate. Pneumoperitoneum was achieved insufflating carbon dioxide to a pressure of 10 mm Hg through a needle introduced into the infraumbilical skin. Five (three 5 mm, two 12 mm) trocars and a 0° forward-viewing telescope were used. The angle formed by the line of action determined by the working ports and the line of vision determined by the telescope was 60° to the right and 60° to the left of the optimal 0∞position.[6] A resection was defined as 12 end-arcade arteries supplying the intended bowel segment to be resected. A 2-handed technique was used during mesentery dissection, and 2 grasping forceps were used to hold the small intestine. Vessels were divided one at a time approximately 1 cm off the bowel wall. In case of bleeding, all time consumed to achieve hemostasis was included in the resection time, which was defined as the time elapsed from the division of the first to the twelfth mesentery artery.

Three currently available ultrasonic-activated devices were compared: AutoSonix® (Tyco, Pembroke, Bermuda), SonoSurg® (Olympus, Tokyo, Japan), and UltraCision“ (Johnson & Johnson, Cincinnati, OH). The following features were adjusted to make the devices as comparable as possible: Axial rotation of the working shaft was not used although available in 2 devices; devices were used as they all were reusable although 2 devices were disposable; increase power (or vibration amplitude) for tissue cutting was achieved by setting power at the maximum level for each device (AutoSonix® 5; SonoSurg® 100%; UltraCisionr 5); power (or vibration amplitude) was set up at the intermediate level for each device (AutoSonix® 3; SonoSurg® 50% UltraCision® 3); the blunt blade edge of UltraCision® was used. Comparable and not well-matched characteristics of the 3 devices are outlined in . A computer-generated block randomization was used to generate the allocation schedule. Resections were randomly allocated to devices. Allocation concealment was ensured giving identity numbers to the resections. Timing of assignment was just before the planned surgical task at the National Center for Advanced Laparoscopic Surgery, Trondheim, Norway. The generator of the assignment was separated from its executor.[7] In a previous study,[4] the median resection time was estimated to be 60 (standard deviation 20) seconds, and a 25% difference in resection time was considered of clinical relevance. With a 5% significance level and a study power of 90%, a sample size of 114 (38 with each device) resections was needed. One-way analysis of variance (ANOVA) and post-hoc pairwise Scheffe tests were used for multiple comparisons. A Kaplan-Meier graph was drawn to illustrate and confirm differences in resection time with each device.

RESULTS

The study comprised 114 small bowel resections performed as allocated, which is 38 with each device. No withdrawals occurred. No significant differences existed in intraoperative blood pressure and heart rate variations in pigs undergoing the resections. The cumulative median resection time of 5160 (range 2340-7860) seconds with UltraCision® was significantly longer than those of the other 2 devices (ANOVA P=0.0001). The difference in cumulative resection time between AutoSonix® (median 3420, range 1860-8760 s) and SonoSurg® (median 3660, range 1800-6900 s) did not reach statistical significance (Scheffe test) (. A Kaplan-Meier plot of resection time with each of the 3 devices illustrated and confirmed the statistically significant differences (. Microscopy revealed no thermal damage to the bowel wall.

Median and range values of resection time of 3 ultrasonic activated devices.

Kaplan-Meier plot comparing the learning effect of 3 ultrasonic activated devices on resection time.

DISCUSSION

Prolonged operating time is one of today's limitations of laparoscopic surgery. In the particular case of laparoscopic colorectal surgery, dissection of the bowel mesentery and division of its vessels are often the most time-consuming parts of the procedure. These issues account for the authors' choice to compare resection time with 3 currently available ultrasonically activated devices in porcine small bowel mesentery. UAS-based laparoscopic dissection of the bowel mesentery is considered a safe procedure because most vessels encountered are within 3 mm in diameter and may be safely divided. In fact, arteries up to 3 mm in diameter exposed to pressures commonly found in living animals and occluded by ultrasonically activated devices are as unlikely to burst as when secured by suture knots or clips.[8,9] The results of the present experimental study showed that uncontrolled bleeding did not occur with the 3 tested ultrasonically activated devices. Differences in resection time among the 3 devices were not due to bleeding, although all time consumed to achieve hemostasis was included in the resection time. Aside from the 23.5-kHz ultrasonically activated device, differences in working shaft diameter and length can hardly account for differences in resection time between the two 55.5-kHz ultrasonically activated devices.

Heat production is a source of concern for unintentional thermal injuries that may occur whenever dissecting close to hollow viscera in laparoscopic surgery. As opposed to bipolar electrosurgery, a 55.5-kHz ultrasonically activated device minimizes macroscopic charring in small bowel mesentery during laparoscopic dissection in a porcine model.[4] Moreover, a 23.5-kHz ultrasonically activated device is associated with a much slower heat production than monopolar electrosurgery.[3] However, absence of microscopic thermal damage to the bowel wall was reported with either bipolar electrosurgery or UAS provided that mesentery vessels were divided 1 cm off the bowel wall.[4] The findings of the present experimental study confirm lack of microscopic thermal damage to the bowel wall with either 23.5-kHz or 55.5-kHz ultrasonically activated devices when the mesentery was divided 1 cm off the bowel wall.

CONCLUSIONS

Laparoscopic resection time of porcine small bowel mesentery was shorter with Auto Sonix® or SonoSurg® than with UltraCision®. No thermal damage to the bowel wall was found when the mesentery was divided 1 cm off the bowel wall.

Table 1.

Comparison of Characteristics and Settings of 3 Ultrasonic Activated Devices

	AutoSonix®	SonoSurg®	UltraCisionr
Active blade
Length, mm	13	15.5	15
Type	blunt	blunt	blunt
Cutting mechanism	increase power	increase power	increase power
Handle ergonomics	pistol grip	pistol grip	pistol grip
Vibration setting
Amplitude, mm	70	100	80
Frequency, kHz	55.5	23.5	55.5
Use	disposable*	reusable	disposable*
Working shaft
Axial rotation	available*	available*	unavailable
Diameter, mm	5	11	10
Length, mm	29	33	34

Features not used as stated.