Camran Nezhat, MD, Michael Lewis, MD, Louise P. King, MD, JD
Multiple technological advances have allowed surgeons to treat extensive disease and complicated pathology by laparoscopy. Initially, the establishment of pneumoperitoneum allowed for better visualization of the operative field and better access to the deep pelvis and cul-de-sac.1 The full promise of excellent visualization was realized with the introduction of video-laparoscopy in 1986 and innovations that achieved higher resolution videography.2 As surgeons sought to treat more and more complex cases by laparoscopy, the need for versatile and reliable hemostasis became of utmost importance.
Initially, surgeons used suturing, then titanium clips and laparoscopic stapling devices. The first electric modality introduced used monopolar electrocurrent which passed through tissue via the use of two electrodes at distant sites. Energy is dispersed from the active smaller electrode on the Bovie or other instrument to a larger return electrode, the grounding pad. Common monopolar instruments used in laparoscopy include the shears, scissors, hook and spatula. Concentration of current at the smaller electrode allows for hemostatic cutting and coagulation. However, injuries were common with this first technology for a variety of reasons. The instrument shaft has current passing through it. If the insulation of the shaft is damaged tissues such as bowel or blood vessels touching the shaft can be injured. Direct coupling can result from unintended contact with tissue or from an electric arc between the active electrode and a metal instrument or object. This contact can energize the object in question, usually the laparoscope, a grasper or a ligating clip that may be outside the field of vision. Capacitive coupling occurs when current is transferred from the active electrode through the intact insulation into adjacent materials without direct contact because of a difference in potential between two conductors. Factors that increase the risk of this type of injury include longer instruments, thinner insulation, higher voltages and narrow trocars.3
Bipolar diathermy overcomes some of the limitations of monopolar electrosurgery.4 Bipolar technology employs an active electrode and a return electrode into a single electrosurgical instrument with two small poles. Rather than passing through the patient to the grounding pad, the alternating current is distributed through the target tissue.5 Lower voltages are needed to achieve the same tissue effect in bipolar electrosurgery as those achieved in monopolar because the poles are close to each other. Bipolar electrosurgery thus results less potential damage to surrounding tissues and less risk of capacitive coupling.3 The classic bipolar instrument is the Kleppinger bipolar forceps used most commonly for laparoscopic tubal sterilization and hemostasis of vascular pedicles. Bipolar forceps allow for firm grasping and reliable coagulation of vessels less than 3 mm in size. Newly developed vessel sealing devices build upon bipolar diathermy as well as ultrasonic technology to provide more consistent hemostasis with added functionality and increased efficiency.
Recent reviews have compared the most commonly used vessel sealing devices.6-9 Both ultrasonic and bipolar electrosurgical instruments employ tissue sensing technology and can seal blood vessels with supra-physiologic burst pressure equal to that of previously used surgical clips or ligatures. Research continues in the field to achieve minimal thermal damage to surrounding tissue and improve the speed with which a reliable seal is achieved without compromising the seal integrity.
Most studies of currently available technology show small statistical differences in mean burst pressure and seal times; however, these differences likely have little effect on surgical outcome. Instead, reproducibility of effect and comfort of use or ergonomic design are of greatest importance when evaluating the superiority of various instruments. The following factors should be considered when selecting a vessel sealing device for use in a particular case:
Consistency: Independent of user, the device must consistently perform the same way with every procedure. You can assume it will behave similarly to previous procedures.
Utility: The device is able to perform sealing and ligation for the majority of steps of any particular case.
Reliability: For vessels up to 7mm in diameter, the device does not change its sealing capabilities with repetitive uses during a single case.
Efficiency: The treatment time needed to seal the tissue will not prolong the operation unnecessarily.
Safety: Lateral thermal spread is not excessive with reference to the needs of any particular case and anatomy.
The following is a brief review of the currently available laparoscopic vessel sealing devices.
Ligasure (Valleylab, Boulder, CO)
This bipolar electrosurgical device delivers high current, low voltage along with pressure from the jaws to tissue. The instrument can seal vessels up to 7 mm in size. Of note, this differs from the high voltage, low current energy used in standard monopolar and bipolar cautery instruments. The system monitors the energy expended while denaturing the collagen and elastin within the vessels walls. During the cooling phase of the cycle, cross linking re-occurs creating a new seal. The instrument is available in 5 or 10-mm sizes. For most gynecological procedures, the 5-mm size is used.
Tissue sensing technology in the Ligasure makes use of a computer algorithm to adjust the current and voltage based on real-time measures of tissue impedance. This results in a constant delivery of wattage over a broad range of tissue types.
Enseal (SurgRx, Inc. Palo Alto, CA)
The Enseal Tissue Sealing System uses a bipolar electrode to concentrate energy on tissue within the plastic jaws of the instrument. Enseal claims to offer improved efficacy by utilizing a temperature sensitive matrix (nanopolar thermostats) embedded within the jaws of the device that controls the energy delivered to the electrode-tissue interface. The instrument can seal vessels between 1 and 7-mm. Proper use of the Enseal, as with the Harmonic Scalpel, requires a certain level of surgical skill as compared to the Ligasure, Gyrus and Caiman and thus is surgeon dependant.
Caiman (Aragon, Palo Alto, CA)
The Caiman is a new product similar to the Ligasure that promises the same applications but with smaller thermal spread and less operative time given a larger jaw with sealing lengths up to 50-mm. Traditional electrosurgical technology operates on impedance only. However, the Caiman uses an algorithm based on a pulse waveform modulation (PWM) that monitors and delivers current in relation to power, voltage and resistance. This results in virtually no tissue charring or tissue adhesion. Aragon also describes decreased thermal spread as compared to traditional electrosurgical technologies. The articulating head allows the surgeon to operate in hard to reach areas but is only currently offered in a 10mm size. A 5mm version is expected to be available in early 2011. Further experience and comparative studies will be necessary to fully assess this new product.
This bipolar electrosurgical device uses plasma kinetic technology to deliver a high current and very low voltage to the tissue. A series of rapid pulses allows a cooling phase during coagulation thereby decreasing lateral thermal spread. The vessel is sealed by denaturing the protein within the vessel walls, forming a coagulum which occludes the lumen. One of the advantages of this device is its ability to hold onto the tissue being desiccated without slipping. However, in areas where careful dissection may be needed, its jaws can also be traumatic. A blade can be manually deployed through the forceps to transect tissue. Both a 5-mm and 10-mm version is available. A Gyrus spatula is also available and can be used as both a cutting and coagulating instrument.
The Harmonic Scalpel is a high frequency ultrasonic transducer. The active titanium blade vibrates at 55,000 cycles per second. The resulting mechanical energy causes a breakdown of protein in tissues which creates a coagulum. Vessel and tissue sealing is dependent on the power setting as well as the pressure exerted, the formation of the coagulum and tissue tension. The Harmonic Scapel’s mechanism of action is the same as the Gyrus; however, the variability of energy delivered can be adjusted by the surgeon, permitting different tissue effects. The Harmonic Scalpel performs at lower temperatures (50-100 degrees Celsius) while other devices work at higher temperatures (150 to 400 degrees Celcius), causing desiccation and charring. The active blade of the Harmonic Scalpel can also be used as a knife. Available 5-mm blades include a hook, straight and curved electrodes. Curved blades are more versatile and allow for work around difficult anatomical angles; as the blade is able to follow the direction of tissue, the rate of tissue transaction is faster. However, hemostasis is superior with the straight blade. As compared to the other devices listed, the Harmonic Scalpel is FDA approved to seal vessels up to 5-mm.
In a prospective comparison of four laparoscopic vessel ligation devices, the Ligasure had the best overall performance with the highest burst pressure, low thermal spread, fast sealing time, and low smoke production. By contrast, the Harmonic Scalpel has the lowest thermal spread and smoke production but was slow and had the lowest mean burst pressure. The Gyrus has a fast sealing time and the highest smoke production while the Enseal had the slowest sealing time.5 The Caiman was not yet available at the time of the this study. Further comparative studies are warranted.
Sealing time alone should not dictate the device used. Despite being statistically significant in the study described above, we believe the complexity of the individual case would contribute more towards time of surgery than the sealing time of any particular product. Of course, mean burst pressure and lateral spread are important if the surgeon plans cutting or coagulating close to the pelvic side walls. Tension is required for exposure and application of the instrument; however, the more tension that is used, the worse the seal achieved. Be cautious that instruments do not stick after you have sealed and cut. Opening the jaws quickly or abruptly can lead to unnecessary tearing or bleeding.
In conclusion, for the same reason every surgeon performs every procedure with their own habits or instrument preferences, there is no winner for the best vessel sealing device. In some instances, a 5mm port is preferred over a 10mm port as smaller instruments are less bulky and can be used dissectors. On the other hand, small tissue bites may prolong operative time or fail to seal larger vessels. As a surgeon gains more experience with each device, he or she will be better able to predict which instrument is best suited to any particular case.
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