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.

NEXT: Laser procedures

Laser procedures

In our clinical practices, we use the CO₂ laser delivered by flexible fiber in myomectomy, lysis of adhesions, and treatment of endometriosis. We find that it functions extremely well in all these situations, thanks to its specific maneuverability, functionality, and safety profiles, especially in conjunction with the minimal depth of penetration of thermal damage. This provides increased safety while working near critical structures such s bowel, bladder, ureters, and blood vessels. The safety profile of CO₂ laser in proximity to delicate vital structures has been particularly highlighted by a recent in vivo animal study looking at the effects of the laser fiber compared to monopolar electrocautery on the sciatic nerve.⁸

More: Mini-laparoscopy

As reproductive surgeons, we are faced with the challenge of removing fibroids of all sizes and locations while respecting the surrounding reproductive tissues in order to create conditions that are conducive to successful pregnancy and delivery. Because of this, based on the arguments and evidence discussed above, we have never employed electrosurgical instruments for myomectomy (with the exception of focal bipolar coagulation of isolated tumor-feeding vessels). Our instrument of choice has been the ultrasonic scalpel, which is our only energy choice for conventional laparoscopic myomectomy.

However, our surgical practice over the past decade has shifted toward an almost universal use of the robotic surgical system for all, or part, of the myomectomy operation. The adoption of robot-assisted surgery has revealed the limitations of the ultrasonic scalpel. Because its long vibrating rod occupies the entire shaft of the instrument, the ultrasonic scalpel loses pitch and yaw at the distal wrist, which is a fundamental technical characteristic of robot-assisted surgery.

It is, therefore, not surprising that reproductive surgeons have pioneered the use of the CO₂ laser fiber in robotic myomectomy for fibroids up to 8 to 10 cm in diameter.⁹ The flexible fiber in its sheath will pass easily through a 5-mm laparoscopic cannula. If you want to simultaneously use the trocar for other instruments (suction-irrigator, tenaculum, grasper, etc.) as we frequently do in our robotic cases, you will need an 8-mm or 12-mm assistant cannula. The flexible fiber in its sheath is passed through the assistant port and seated onto the robotic large needle driver while the laser is in standby mode. The fiber will follow all of the movements of the large robotic needle driver, including the pitch and yaw of the wrist, allowing exceptionally precise delivery of the beam and a consistently optimal angle of incidence (ie, perpendicular to the tissue surface).

Meanwhile, the 3-dimensional working environment implicit in computer-assisted surgery, together with the fact that this laser is basically a contact device, will virtually eliminate the danger of pass-pointing. Because of this, we have never felt that the use of a separate visible laser pointer would be advantageous (Figures 3A-3D).

In the Bailey et al. study, tissue damage remained consistent at 110 to 130 microns for laser settings of 5 to 15 watts.¹ However, we prefer to minimize the energy deposited in and around critical structures, including the ovary, while maintaining a level of energy that accomplishes the planned procedure. Therefore, in a myomectomy, we set the CO₂ laser to between 10 and 20 W, depending on the thickness of the tissue layers to be incised.

The fiber is then aimed perpendicularly at the target tissue, using the tip of the FlexGuide as a reliable bearing; indeed, we recommend that the spatula tip touch the tissue while in use (unless the fiber is being pulled away from the tissue for use of beam divergence to obtain a coagulation/ablation effect).

A foot pedal (set in front of the robot pedal section in robotic cases or toward the foot of the bed for conventional laparoscopy) engages the laser; a 180-degree shield covers the foot pedal, to protect against inadvertent use. Once engaged, the laser allows for layer-by-layer dissection of the tis sue planes overlying the fibroid and minimal charring of the tissue (due to the occurrence of vaporization instead of coagulation). Moreover, a constant flow of helium (inert gas) keeps the hollow of the fiber clean of debris, but also blows any pooling blood out of the trajectory of the laser beam. Absence of overlying blood or water and continuous tissue tension are key elements of successful use of the laser beam for myometrial incision. During enucleation of the fibroid in the robot-assisted setting, the spatula tip of the FlexGuide is an outstanding tool for blunt dissection. This spatula tip should be cleaned of accumulating debris if the energy output appears diminished. This is most safely accomplished by placing the unit on standby mode and removing the FlexGuide from the cannula with a gentle rotational pull; the guide tip can be briefly placed into saline and then wiped off.

One of the unique applications of the flexible CO₂ laser fiber is its use for myomectomy with single-incision robotic technology, recently described by our team. Such a technique allows for the excision of intramural myomata up to 6 to 8 cm in diameter through a classic open laparoscopy (2.5-cm) vertical umbilical incision, resulting in a virtually scarless surgery. The miniaturization and flexibility of the laser fiber are essential to this technique (Figure 4).¹⁰

We do not employ the CO₂ laser fiber for conventional laparoscopic myomectomy. This is mostly because the laparoscopic delivery guide (LapFlex) is designed for delicate dissection and precise laser application but does not have the short and sturdy build of the robotic FlexGuide and, therefore, cannot be used to dissect and enucleate fibrous tumors with tenacious connections to the surrounding tissues.

Certainly, one could use the LapFlex to perform the hysterotomy to the level of the intracapsular space and then proceed with myoma enucleation through standard non-energy tools; however, we feel that the classic myomectomy technique with the more rigid ultrasonic shears confers unique advantages in conventional laparoscopy. With recent bans on power morcellation, one of us has started using colpotomy to remove large fibroids from the peritoneal cavity. The laser at 18 to 20 watts is an excellent tool for creation of this colpotomy.

However, colpotomy is not a standard procedure in laparoscopic myomectomy. Therefore, patients should be thoroughly counseled regarding potential untoward effects of this approach, including a possible increase in the rate of post-surgical infections, and should formally consent to its use.

Laparoscopic treatment of endometriosis (with or without robotic assistance) also illustrates many of the functional benefits of the laser. Minimal depth of penetration allows one to work very near critical structures while performing resection or ablation of endometriotic lesions anywhere in the pelvis (eg, ablation of peritoneal endometriosis in the ovarian fossa and over the ureter). For the same reason, we use the laser for ovarian cystectomies that have an increased risk of bleeding due to size and/or proximity to the ovarian hilum and especially on endometriomas because they represent invaginations of the original cortex and are therefore particularly difficult to resect. In some of these cases we adopt the technique described by Donnez et al. in 2010: We leave 10% to 15% of the endometrioma in place (namely the base, adjacent to the ovarian hilum) and ablate its surface employing the CO₂ laser in super-pulse mode to minimize the risk of recurrence while avoiding damage to the underlying ovarian vasculature (Figure 5).¹¹

Indeed, use of the laser in this particular application minimizes the incidence of diminished ovarian reserve after such cystectomies. Also in this setting, the tip on the FlexGuide is an excellent tool for blunt dissection in robotic surgery. Differently from what we have described for myomectomy, the conventional laparoscopic delivery system (LapFlex) works very well for endometrioma and ovarian cystectomy in general, and particularly well for ablation of peritoneal endometriosis.

Flexible laser fibers truly shine in the lysis of pelvic adhesions. Using a robotic or conventional Maryland grasper as the main dissector (as well as backstop for the beam), and the tip of the FlexGuide or LapFlex as super ficial dissector, we have been able to consistently, completely, and safely lyse every frozen pelvis we have encountered (Figure 6). The surgeon must understand that the instrument has no thermal spread; it is completely rational and prudent to use full wattage (we use between 5 and 10 watts, continuous mode) to cut an adhesion that lies less than a millimeter from bowel mucosa: no possibility of thermal spread exists.

Also, in the case of the OmniGuide fiber at least, we have never observed any tissue effect deriving from the laser beam being reflected by the metal instrument used as a backstop because the scatter of an already divergent beam has no appreciable thermal effect.

NEXT: Safety considerations

Staff and patient safety considerations

Staff may wear laser-rated eye protection in the operating room, but microscopes, surgical loupes, laparoscopic optics, and standard window glass provide effective protection against the CO₂ laser’s wavelength. Post signs outside the operating room warning that a laser is in use. The treatment area should be free of oil-based lubricants and should not be prepped with alcohol-based solutions, and the patient should have eye protection and a hair cover. The anesthesiologist must use a laser-safe tube and keep oxygen levels as low as possible if the laser will be used anywhere near the airway.

Next: Simulation builds skills

For intra-abdominal cases, the suction will capture airborne particles created by laser vaporization, so laser-specific masks are not necessary. The circulator should take care to wipe up fluids around the laser cart, check for loose wires in plugs, and add reliefs to any strained wires. Bags of irrigation should not be placed above the laser because it is an electronic device.

Patient counseling

Patients should be counseled that all surgical instruments have risks associated with them but that the laser has key safety features and minimizes thermal damage to tissues. Despite this, use of a laser does not completely eliminate the potential for uterine and ovarian tissue damage, so a patient is still at risk for adhesion formation, diminished ovarian reserve, or uterine rupture in pregnancy, depending upon which procedure is being performed.

With initial use of any technology, you should counsel the patient on your level of familiarity and have an experienced surgical mentor with you in the operating room.

Cost considerations

More ethically sound than mere cost-analysis is the concept of value proposition, which keeps cost in mind as it relates it to clinical outcomes. The devices described above have a universally higher cost than most electrosurgical devices currently in use. However, the reintroduction of laser in gynecologic surgery, and particularly in reproductive surgery, could represent a valuable technical addition.

For example, our recently published experience shows that patients undergoing myomectomy with a CO₂ laser have a significantly lower chance of being admitted overnight after surgery compared to those in whom an ultrasonic scalpel was used (which appears to be due to differences in levels of postoperative pain). Because overnight admissions have a steep cost, such postoperative considerations are something to keep in mind when considering the cost-effectiveness of adding laser to your armamentarium.⁹

Also in the case of myomectomy, a uterine dehiscence or uterine rupture has never been described following a hysterotomy performed with laser of any kind. In light of our recent in vitro studies comparing the delayed thermal injury of monopolar cautery compared to CO₂ laser,¹ hysterotomy by laser is likely to be the safest possible one.

Practical considerations also should be made when considering adoption of laser in gynecologic laparoscopy. If your hospital or surgery center owns one of the new-generation laser units, the cost per case will be lower. For example, the same fiber and generators used for otolaryngology can be used for colposcopic, laparoscopic, and robotic applications in gynecology.

Summary

Radical improvements in laser technology mean that the time is ripe for a resurgence of this low-impact energy in laparoscopic gynecologic surgery. Flexible CO₂ lasers are tools of proven safety that minimize thermal damage to irreplaceable reproductive tissues. They should be strongly considered in pelvic surgery, particularly in reproductive-age women.

References

1. Bailey A, Lancerotto L, Gridley C, et al. Greater surgical precision of a flexible carbon dioxide laser fiber compared to monopolar electrosurgery in porcine myometrium. J Minim Invasive Gynecol. 2014;21(6):1103-9.

2. Duffy S. The tissue and thermal effects of electrosurgery in the uterine cavity. Baillieres Clin Obstet Gynaecol. 1995 ;9(2):261-77.

3. Hanby DF, Gremillion G, Zieske AW, et al. Harmonic scalpel versus flexible CO₂ laser for tongue resection: a histopathological analysis of thermal damage in human cadavers. World J Surg Oncol. 2011; 9:83.

4. Chang FH, Chou HH, Soong YK, Chang MY, Lee CL, Lai YM. Efficacy of isotopic 13 CO₂ laser laparoscopic evaporation in the treatment of infertile patients with minimal and mild endometriosis: a life table cumulative pregnancy rates study. J Am Assoc Gynecol Laparosc. 1997; 4(2):219-23.

5. Tulikangas PK, Smith T, Falcone T, Boparai N, Walters MD. Gross and histologic characteristics of laparoscopic injuries with four different energy sources. Fertil Steril. 2001; 75(4):806-10.

6. Baggish M, Baltoyannis P, Badawy S, Laurey D. Carbon dioxide laser laparoscopy performed with a flexible fiber in humans. Am J Obstet Gynecol. 1987;157:1129-1133.

7. Bailey A, Correia K, Missmer S, Gargiulo A. Energy source preferences of minimally invasive reproductive and gynecologic surgeons. Fert Stert. 2013;100(3):S398.

8. Robinson AM, Fishman AJ, Bendok BR, Richter CP. Functional and physical outcomes following use of a flexible CO2 laser fiber and bipolar electrocautery in close proximity to the rat sciatic nerve with correlation to an in vitro thermal profile model. Biomed Res Int. 2015;280254.

9. Choussein S, Srouji SS, Farland LV, Gargiulo AR. Flexible carbon dioxide laser fiber versus ultrasonic scalpel in robot-assisted laparoscopic myomectomy. J Minim Invasive Gynecol. Epub ahead of print 2015 Jun 16.

10. Lewis EI, Srouji SS, Gargiulo AR. Robotic single-site myomectomy: initial report and technique. Fertil Steril. 2015;103(5):1370-7.

11. Donnez J, Lousse JC, Jadoul P, Donnez O, Squifflet J. Laparoscopic management of endometriomas using a combined technique of excisional (cystectomy) and ablative surgery. Fertil Steril. 2010;94(1):28-32.