liquefied fat can aerosolize causing a flash fire due to the diesel effect. The surgical field should be kept clean and dry with surgical suction and sponges [32].
If surgical sites are to be closed, the sutures should be placed an additional 2–3 mm from the lased edge to reduce the possibility of dehiscence.
Pathogenesis
Endoscopic Laser Surgery
Endoscopic Laser Surgery is largely limited to Nd:YAG/diode lasers because the flexible quartz fibers can be inserted through the biopsy channel of the video endoscope. Waveguides for CO2 lasers are improving but not commonly in endoscopic use. Upper airway endoscopic surgery is the most common equine application. Paramount for these procedures is endoscopic surgical skill, the lack of which can cause catastrophic patient complications.
Arrangement of the surgical suite facilitates efficient function, thereby preventing equipment and potential patient accidents. Cables, cords, suction line, vacuum hose, foot switches, horse head supports and restraint devices clutter the area, thus offering every opportunity for misfire, tripping, disconnecting equipment or otherwise contributing to bursts of mayhem. Systematic equipment placement and a clean floor in front of the horse are mandatory (Figure 12.12).
Inadvertent incision or “escaped” laser energy have produced seriously unfortunate patient complications. Non‐contact delivery of this wavelength has the real potential for penetration beyond the pale pink mucous membrane to injure underlying pharyngeal nerves or arytenoid cartilage. Dysphagia or arytenoid chondritis (respectively) are serious complications. Contact incision/excision of tissue (such as vocal fold and laryngeal saccule) is far safer, yet the fiber should still be blackened and directed tangentially to underlying tissues. Additionally, failure to strip the plastic from the quartz fiber can result in flame outs when the plastic burns.
In lieu of excising the laryngeal ventricle, some have performed non‐contact ablation/coagulation of ventricular mucosa to stimulate closure. Any surviving mucosal cells can produce enough mucus to cause a large mucocoele at variable periods postoperatively (Figure 12.13) [2].
Endoscopic laser surgery has also been used to address uterine cysts and uroliths. Perforation of the hollow organ is always a potential; however, the equine bladder is rather thick and the uterus is a quite thick muscular structure. Aside from the decision as to whether the cysts should be treated, the Nd:YAG/diode lasers can be used endoscopically to ablate or excise the fluid‐filled cysts. Some have “boiled” the interior fluid to “burst” the cyst. The author is unaware of complications except occasional hemorrhage, which should be controlled if it occurs. Insufflation is required to visualize the endometrium and cysts. Over‐insufflation can compress the cysts and make them difficult to locate or manipulate. The author has seen no report of air embolism or peritoneal insufflation from this procedure but the potential should not be discounted and air should always be evacuated after a procedure.
Figure 12.12 Operating facility for standing endoscopic surgery. The video endoscopic monitor faces the surgeon making all the movements in the patient mimic those on the screen. The floor around the surgeon and assistants is free of cables or other debris.
Source: Kenneth E. Sullins.
Figure 12.13 Incomplete ventricular mucosal ablation left buried viable mucus‐producing cells, resulting in a mucocoele that had to be surgically addressed.
Source: Kenneth E. Sullins.
Lasers of different wavelengths than discussed here or other techniques are required to efficiently address equine uroliths. The pulsed dye laser does work well but has become largely unavailable. The Ho:YAG laser is used for smaller uroliths in dogs and humans, but is extremely inefficient for the larger equine stones. Endoscopic guidance has successfully confined the laser energy to the urolith. The author has observed no complications directly related to either laser for lithotripsy. However, insufflation is required to access the stones and both lasers transmit a constant flow of gas into the bladder. Air embolism during standing cystoscopy has been reported, although the horse also had an intravenous catheter in place [33].
Prevention
Care should be taken to minimize inadvertent application of the laser fiber to normal tissues. Care should also be taken to minimize the hot laser fiber to touch normal tissues. In a confined cavity, insufflation should be kept to a minimum to limit compression of cysts and to reduce the likelihood of penetrating the thin wall of the insufflated organ.
Pathogenesis
Tarsal arthrodesis complications
The Nd:YAG/diode laser has been applied to “arthrodese” the distal tarsal joints of horses with refractory distal tarsal osteoarthritis [34]. The laser fiber inserted into the joints through a needle generates sufficient heat to boil the joint fluid, thereby incapacitating the sensory nerves in the fibrous joint capsule. The needle becomes extremely hot and will burn the skin, possibly causing a significant slough, which opens the joint.
Prevention
The skin and needle should be constantly covered with gauze sponges soaked in frozen “slushy” sterile saline to avoid this complication. Furthermore, inserting the needle/laser from the down side of a limb of a horse in lateral recumbency makes it very difficult to maintain this freezing procedure on the limb.
Equipment Complications
Definition
Complications associated with the laser equipment
Risk factors
Aged endoscope
Reuse of fibers
Acute flexing of the endoscope
Pathogenesis
Successful endoscopic laser surgery requires practice and attention to detail for patient and equipment safety. The videoendoscope itself is at risk of serious damage.
Quartz fibers (Nd:YAG‐Diode lasers) and waveguides (CO2 laser) can be relatively fragile and random laser energy escapes when they break. Carbon dioxide laser waveguides are highly polished semi‐flexible tubes and generally not flexible enough to pass safely through an endoscopic biopsy
