The high-power ultrasonic dissection devices have become an integral part of current laparoscopic surgical instrumentation.18-21 They carry undoubted advantages over HF electrosurgery in that they do not generate smoke, while maintaining good cutting and secure tissue coagulation at dissection. Currently, three systems are commercially available: UltraCision Harmonic Scalpel™ (Ethicon Endo-Surgery, Cincinnati, OH), Autosonix™ (USSC, Tyco Healthcare, Norwalk, CT), and SonoSurg™ (Olympus, Tokyo, Japan). Each system consists of an ultrasonic generator, a foot switch, a hand piece, and various types of minimally invasive instruments. The generator supplies an electrical signal to the hand piece through a shielded coaxial cable. A piezoelectric ceramic element in the hand piece expands/contracts rapidly (up to 55 kHz) when electrically activated. This mechanical energy is then transduced to an imperceptibly moving blade that oscillates to produce heat secondary to friction and shear when coupled to the tissue. The vibration of the blade also causes cavitational fragmentation to separate the tissue ahead of the blade. Coagulation is also accomplished by conversion of ultrasonic energy into localized heat in tissue, which causes collagen molecules in adjacent tissue to denature. Because the scalpel itself is not heated, it does not become very hot. Thus, there is no smoke production (it produces a water vapor "mist"), no charring, no accumulation of debris on the blade, and thermal injury can be minimized. In general, lower power causes slower tissue heating and thus more coagulation effect. Higher-power setting and rapid cutting is relatively nonhemostatic. In these regards, ultrasonic surgery is similar to other forms of energy-induced hemostatic modalities. Aside from the power setting, hemostatic tissue effect can be enhanced by blade configuration and tissue traction in a manner analogous to electrode design for electrosurgery.
Blade configuration has a significant effect on device performance. Currently available blades include a single-blade scalpel (hook, ball, spatula) and a coagulating shears. A single blade is used in a similar manner as the monopolar electrosurgical appliances. If the sharp edge of the blade is used, good cutting is achieved. If the blunt side of the blade is pressed on tissue, good coagulation can be obtained. These "single-bladed" ultrasonic scalpels are useful for rapid incision/dissection on avascular planes such as lateral attachment of the ascending/ descending colon. For colorectal surgical use, however, our recommendation is the shears-type instrument, sometimes so called "Laparoscopic Coagulation Shears" (LCS). It consists of a stationary portion that supports the tissue and a vibratory blade that transmits the ultrasonic energy to the tissue (Figure 3.9). The tissue is grasped with the shears and clamped. The blade is then activated to coagulate the tissue. The blade can also be used in a manner similar to the ultrasonic scalpel to cut or coagulate. Because of its tip configuration, the LCS-type instrument can also be used as an effective dissector when its blade is inactivated. Our experience has shown that the 5-mm LCS-type instrument provides the best surgical flexibility in colorectal surgery and reduces the instrument traffic through the working port during the operation.
Previous studies have shown that small- to medium-size arteries can be appropriately occluded and divided by LCS-type ultrasonic dissection devices.18-20 Kanehira et al.20 compared the bursting pressure of 3- to 3.5-mm porcine arteries occluded by SonoSurg™, laparoscopic clips, or silk ligatures, and reported the comparable performance of SonoSurg™ to clips and ligatures. Another study demonstrated that porcine arteries up to 5 mm in diameter can be divided safely by 10-mm UltraCision LCS™ if the blunt side of the blade is used.19 These data suggest that when used alone, the ultrasonic dissection device can securely occlude small arteries in humans, if the device is used
appropriately. This is valuable in colorectal laparoscopic surgery, especially when dissecting fatty tissue such as mesentery or omentum.
Reduced heat production has been known as another advantage in ultrasonic dissection.18 Less energy to surrounding tissue during activation can lead to a reduced propensity for lateral thermal damage. Kinoshita et al.1 studied the change in temperature around the blade of conventional electrocautery and ultrasonic dissecting device: the temperature of the tissue adjacent to the SonoSurg™ blade increased gradually and remained below 150°C; by contrast, with electrocautery at 30 W, the tissue temperature increased rapidly and exceeded 350°C within only a few seconds. They also investigated the width of the area where the tissue temperature reached 60°C or more, and reported the final width of 10 mm for SonoSurg™, as compared with 22 mm for electrocautery. These data demonstrate that ultrasonic surgery may cause fewer thermal alterations in adjacent tissue compared with conventional electrosurgery.
One well-known disadvantage of the ultrasonic dissection device is that the tissue coagulation or cutting takes more time compared with the conventional electrosurgical devices. A serious "vapor" (mist) production during the procedure is another disadvantage of LCS, although the vapor vanishes more rapidly than smoke.22 Although one study indicated that very few morphologically intact and no viable cells were found in the vapor,23 the aerosol created by the ultrasonic scalpel has not been well studied and no consensus exists regarding its composition.
In summary, the ultrasonic dissection device is a useful tool in laparoscopic colorectal surgery. Less thermal spread is practically valuable when dissecting significant structures from fatty tissue: e.g., taking down the ureter and gonadal vessels below the inferior mesenteric pelvic artery pedicle, and skeletonizing the vascular pedicle during pelvic lymph node dissection.
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