ISRAEL JOURNAL OF
VETERINARY MEDICINE
Vol. 62 - No. 3-4 2007
REVIEW
USING THE CO2 LASER FOR VETERINARY SOFT TISSUE
SURGERY
GANS Z.
RAMAT HASHARON VETERINARY CENTER, ISRAEL
Surgical lasers have been used in human medicine for over 35 years. In veterinary
medicine lasers have been used infrequently in the past, but since the late 1990's there
has been a significant increase in their use by veterinarians. Over the past 15 years
there have been major improvement s in surgical CO2 lasers units in their size, ease of
operation, maintenance, and most important–cost. Following these developments laser
usage in soft tissue surgery became much more widelspread (initially in the American
market but recently in the European and Asian markets) and these units are routinely
used for ovariohysterectomy, castration, tumor removal and more. In addition, the
advantages of the lasers allow general practitioners to perform procedures in their
own practice, such as soft palate resection and anal sacculectomy that were previously
referred to board qualified surgeons.. The learning curve for the use of the laser units
is relatively rapid1. Both theoretical and practical training opportunities are available
at major conferences by many manufacturers, in the veterinary literature and through
the Veterinary Surgical Laser Society
How does the LASER work?
All surgical laser units have a similar basic structure. A tube containing molecules to
be "lased" (most veterinary surgical units use CO2 molecules as medium), a set of
mirrors that direct the laser beam in a unidirectional manner outside the tube, a
delivery system (articulated arm or flexible fiber) that "carries" the laser beam from
the tube to the patient, and a hand-piece that focuses the laser beam on the tissue.
The molecules in the tube are charged with energy (electric current) and are being
"pushed" to a higher energy level. As the molecules wish to return to their most
stable, lowest energy level they release energy. On their way down the energy scale,
the molecules pass through a "metastable" state. The energy released from that state to
return to the lowest energy level is released in the form of a photon (light energy).
Each molecule releases a photon of a specific wave length (monochromatic) – CO2
molecules release a photon with a wave length of 10.6µm. This wave length is ideal
for soft tissue surgery because it absorbs perfectly in water molecules (over 85% of
soft tissue content) and spreads minimally beyond the impact point. The beam of
energy turns to heat at the impact point, instantaneously boils the intercellular water
and causes vaporization of the cells which disappear as fumes2,3,4.
The impact of the laser beam on the tissue is a function of the "power density" (the
wattage of the beam divided by the square diameter of the beam's focal point). Most
surgical CO2 lasers are focused systems, which means that the laser beam's highest
intensity is found a few millimeters beyond the delivery system – where the focal
point is the smallest. Since the power density decreases by the square of the focal
point's diameter, the surgeon can change the impact of the beam by slightly moving
the delivery system away from the tissue. This allows him to move back and forth
from incising to coagulation without any changes in the machine settings. Focused
systems are also safer because their intensity decreases rapidly the further you get
from the delivery system – decreasing the chance for accidental harm to personel or
equipment away from the laser unit.
CO2 lasers have several advantages over the scalpel. The laser beam incises very
accurately when the beam is focused on the tissue (advanced CO2 lasers have focal
points of 0.1-0.3mm). That said, when moving the delivery system away from the
tissue (defocusing) the intensity of the laser on the tissue diminishes and it can be
used for cauterization of small blood vessels and lymphatics. The laser beam can seal
blood vessels up to 1mm in diameter. Similarly, the laser decreases post-operative
swelling by sealing lymphatic vessels. Probably most important, the laser deceases
post-operative pain by sealing nerve endings at the incision, thereby preventing
formation of an action potential and pain conduction. Bacteria, viruses and fungi also
evaporate under the laser beam which leads to a decrease in local infections 2,3,4,5,6.
Few conflicting studies are available regarding speed of healing of laser incisions
compared with scalpel incisions in animal models. One study found a stronger
incision for laser incision compared to scalpel incision 21 days post-operatively but
equal strength after 21 days7. Another study found the exact opposite 8. Shared
clinical experience of over 10 years among veterinarians using lasers in soft tissue
surgery led to common agreement that it is safe to remove sutures 10 days post - laser
surgery without an increased risk for dehiscence 5.
Safety
Aseptic technique should be maintained in laser surgery as in any surgical procedure.
The veterinary surgeon should be familiar with the use of the laser unit, and the
surgeon and support staff should be familiar with all the safety procedures involved
with the laser unit.
The laser is a fire hazard. Contact between the laser beam and the oxygen in the
operation room should be prevented. When performing surgery in the oral cavity or
around the head the endotracheal tube should be wrapped in wet gauze to prevent
accidental contact with the laser beam. During aseptic preparation of the patient one
should avoid using alcohol on the patient, and wait for all the alcohol to evaporate
before the start of surgery or wash the prepared area with sterile 0.9% solution to
prevent the alcohol from catching fire. When performing surgery around the eyes they
should be covered with wet gauze to prevent accidental harm to the cornea. The risk
for "long – range" injury from the laser beam is quite low with the "focused" units;
however it is still advisable to use protective eye gear for all personel in the operation
room. In addition, it is recommended for the entire surgery team to use face mask
blocking particles up to 0.5um (a recommendation from the human field where there
is concern for inhalation of contagious viral particles in the fumes). It is recommended
to use a smoke evacuation system while the laser is at work and prominently mark the
presence of the laser unit in the surgery room for the benefit of all potential visitors
2,9
.
Laser unit types
Laser units are primarily of two types depending on their delivery arm system:
flexible fiber or articulated arm. The flexible fiber unit's major advantage is that it is a
bit easier to get used to as you manipulate the hand piece at different angles. The
major disadvantage of the flexible fiber is its high cost and the fact that it requires
replacement over time. Over long periods of use, the output of the flexible fiber may
decrease due to changes inside the fiber which initially may require increasing the
wattage of the unit and eventually may even require that the entire fiber to be
replaced. Most flexible fibers have "focusing tips" which need to be discarded every
number of procedures, thus increasing the running cost of the machine. The
articulated arm units are a bit more difficult to get used to initially, but have no
maintenance costs. Some units require manual calibration when the unit is turned on
while others auto-calibrate when turned on. Most advanced laser units provide 3
operational modes: 1. Pulse mode – where each press on the foot pedal releases a laser
beam of a pre-determined duration and intensity (used for small lesions such as
ectopic cilia). 2. Continuous mode – where the laser beam emits photons as long as
the foot is on the pedal, at a pre-determined intensity (used primarily for large bulky
resections). 3. Superpulse /Ultrapulse mode – where each time the pedal is being
pressed the unit releases a stream of photons with multiple ultra-short pauses
combined into the seemingly continuous beam. This mode allows for high intensity
laser beam output with minimal thermal damage to surrounding tissues. This is the
mode in use for the vast majority of soft tissue applications. Most laser units provide
an output of 15-25 watts. In small animal soft tissue applications wattage over 1015W is rarely needed10.
As laser procedures and benefits become more widely known in the human medical
field, the expectation from pet owners for laser procedures for their pets increases as
well, and is likely to encourage veterinary practices to incorporate laser units into
their list of available services in the near future in their own practice.
References
1. Eeg, P.H.: Laser technology offers wide range of surgical applications. DVM in
foc. 20-26; 11 2003
2. Lucroy, M. D.; Bartels K.E.: Using biological lasers in veterinary practice. Vet
Med. 95 (suppl. 10):4-9; 2000
3. Crane, S.W.: surgical lasers. Textbook of small animal surgery, 2nd Ed. (D.H.
Slatter Ed) W.B. Saunders, Philadelphia, Pa., 2001; pp 197-203
4. Bartels, K.E.: Curreent techniques in small animal surgery, 4th Ed. (M.J. Bajorab et
al). Lippincott Williams & Wilkins, Baltimore, Md., 1998; pp 45-52
5. Durante, E.J.; Kriek, N.P.: Clinical and histological comparison of tissue damage
and healing following incisions with the CO2 laser and stainless steel surgical blade
in dogs. J. S. Afr. Vet. Assoc. 64(3):116-120; 1993
6. Wright, V. C.: Laser surgery: using the carbon dioxide laser. Can. Med. Assoc. J.
126(9):1035-1039;1982.
7. Finsterbush A, Rousso M, Ashur H: Healing and tensile strength of CO2 laser
incisions and scalpel wounds in rabbits. Plast Reconstr Surg. 70(3):360-2; 1982.
8. Buell BR, Schuller DE: Comparison of tensile strength in CO2 laser and scalpel
skin incisions. Arch Otolaryngol. 109(7): 465-7; 1983.
9. Smith, J.P. et al.: Evaluation of a smoke evaluator used for laser surgery. Lasers
Surg. Med. 9(3):276-281; 1989
10. Lopez, N.A.: The basics of soft tissue laser surgery. Vet. Med. (4)294-301;2002