Nimble laser devices for minimally invasive gynecologic surgery

 

 

 

 

 

 

Minimally invasive gynecologic surgery (MIGS)  has become the standard of care in all developed countries. One of the most notable technical changes in the safe translation of surgeries from the open to laparoscopic arena has been the use of energy, rather than cold steel, to keep the operative field clear of blood. In laparoscopy, we lack the ability to remove blood and other fluids by pressure and sponging; also, we have a more limited ability to apply continuous suction. Consequently, the use of energy in minimally invasive gynecology “comes with the territory.”

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Gynecologists operate in close proximity to vital organs and to nonvital but still irreplaceable reproductive tissues. Achieving adequate hemostasis while avoiding excessive thermal injury is one of the main goals of safe gynecologic laparoscopic technique. Expert laparoscopists spend years mastering energy tools and may resist trying radically different energy forms.

The goal of this review is to entice practitioners to reconsider the role of the laser in surgical gynecologic practice in view of the radical technical innovations that have changed the tool in recent years.

How lasers work

“LASER” is an acronym for “light amplification by the stimulated emission of radiation.” As laser energy is deposited, water in tissue is heated and vaporized, producing steam and tiny solid particles (a laser plume). Because laser is a light based energy, lasers that operate at different wavelengths have different properties. Carbon dioxide (CO₂) laser is highly absorbed by water in tissue. Because of that, energy effects are limited to an area immediately adjacent to the laser-tissue interface, at a depth of approximately 150 microns.

Furthermore, CO₂ laser is not pigment-seeking, so energy is distributed evenly throughout the tissue independently of the presence of hemoglobin. TP and Nd:YAG lasers have a depth of penetration greater than 4 mm and are more pigment-seeking. Laser’s tissue effects vary by power density (power output combined with beam diameter), duration of application, and the target organ (lasers act on the water content of cells, which changes with tissue type).

The tissue effects of electrosurgical instruments vary based on these same characteristics, plus waveform and the shape of the electrode. Because there are two more variables with electrosurgery, its effects on the tissue are less consistent and thus less predictable than those of the laser. A recent animal study by Bailey et al. showed that monopolar electrosurgery, in both cut and coagulation modes, damages uterine tissue significantly more than the CO₂ laser and that the tissue damage increases in proportion to the power setting with electrosurgery significantly more than with the laser.¹ This is a clinically significant difference in that surgeons are classically trained with mechanical tools (knife) that will cut deeper-but not wider-with any increase in energy applied to them. These results corroborate prior research that shows that electrosurgery has a depth of penetration of up to 3.5 mm (depending on duration of use).²

Because of the large thermal spread, electrosurgical instruments must be used with extreme caution to limit common complications such as pelvic adhesions as well as rarer but more serious complications such as injury to the bowel, bladder, or ureter. Conversely, laser energy can provide sub-millimeter depth of tissue penetration,³ which may be beneficial for improving patient outcomes and avoiding complications.^4,5

Laser use in surgery

Surgical lasers have been in use for more than 60 years and were introduced to gynecology in 1974. Utilization surged in the 1980s, followed by a loss in popularity, likely due to a general inability to efficiently employ this technology in laparoscopy, as well as to the improved safety of electrocautery technology. Many surgeons of this generation remember laser units collecting dust in utility rooms. The technical reason for the effective demise of the line-of-sight lasers in gynecology was unwieldiness. Laser units were bulky, laser arms were clumsy and obtrusive, laser pointers were somewhat intimidating, and lasers were either cutting or coagulating instruments, with minimal flexibility.

In a partial answer to this problem, Baggish et al. reported in 1987 on a flexible fiber by Xanar Inc. that allowed a CO₂ laser to be used laparoscopically in humans.⁶ This technology, however, did not gain wide acceptance, possibly due to the short length of the fiber and the limited adoption of laparoscopy in gynecology at the time. As a result, although many gynecologic surgeons have used a CO₂ laser at some point (predominantly externally), most are completely unfamiliar with many of its characteristics.⁷ Although its safety and accuracy is well-documented, laser energy remains the most underutilized energy option in gynecologic laparoscopy today.

Laparoscopic use of the laser has recently resurfaced, in part due to a new generation of flexible fiber delivery systems for the CO₂ laser in gynecology. These systems feature several characteristics that have the potential to foster the adoption of this energy form by advanced gynecologic surgeons. The first flexible CO₂ laser fibers with documented use in gynecologic laparoscopy are the BeamPath and BeamPath Robotic fibers (OmniGuide Inc.). These hollow fibers feature beam divergence, which allows the surgeon to increase the area of laser-tissue interaction simply by pulling the beam slightly away from the tissue. A smaller area concentrates the energy to produce a cutting effect, while a larger area allows for broad deposition of energy contributing to hemostasis or superficial ablation.

As a safety feature, the very rapid drop in power density with distance minimizes damage to other organs (in the case of “past-pointing”) or to operating room personnel if the laser should be engaged while the tip of the fiber is outside the patient. In spite of this implicit safety, a judicious use of the standby mode is recommended at all times when the operator is not actively using the laser.

The generator for the OmniGuide laser is kept at a safe distance from the patient and from the surgical field, thanks to the use of fibers up to 180 cm. The distal segment of the fiber (ie, the one closer to the patient) runs through either a 2.9 mm flexible steel guide introduced through a laparoscopic cannula during robotic cases (FlexGuide, OmniGuide, Inc.), or a 5-mm laparoscopic applicator with articulated tip in conventional laparoscopic cases (LapFlex, OmniGuide, Inc.) (Figures 1 and 2).

The coiled design of the FlexGuide Ultra accommodates full robotic wrist articulation. Photo courtesy of OmniGuide.

 

The authors of this review have had a chance to use several iterations of this device, thus it will necessarily be the main focus here. However, the BeamPath is not the only flexible CO₂ laser fiber on the market, and many of the technical points discussed below may apply to other products based on similar technology, such as the FiberLase LTC fiber and Acupulse Duo CO₂ generator (Lumenis, Inc.). Unique aspects of the FiberLase LTC include the fact that it is a multiple-use fiber (for up to 5 operations), which is attractive in terms of cost containment. Moreover, the FiberLase LTC has an aiming beam, which could be a welcome feature to surgeons who are used to the classic line-of-sight set-up. Similar to the BeamPath, The FiberLase LTC is quite long (200 cm), allowing placement of the generator well out of the operator’s way.

Photo courtesy of OmniGuide.

As stated above, our clinical experience has focused on the OmniGuide system. This is due not only to the fact that this was the first flexible CO₂ laser system on the market, but also to the unique mechanics of the delivery systems (for both robot-assisted and conventional laparoscopy) and to the novel concept of the divergent beam, which allows for an intuitive and immediate change of tissue effect.

Other types of laser fibers that do not allow use of the laser delivery system as a probe or spatula, or that produce a broader area of thermal damage than what is achieved with CO₂ lasers, will not be considered in this review and should not be employed due to the availability of the above models.

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