Laser surgery: transendoscopic

• Transendoscopic surgery provides a safe, reliable and minimally invasive surgical method for surgical treatment of some equine upper respiratory tract (URT) conditions.
• The Nd:YAG laser Laser surgery: overview is usually used transendoscopically, transmitted through a 2.1 m long, flexible fiber introduced via the biopsy channel of most fiberoptic or videoendoscopes.
• When activated, the fiber tip emits a red aiming beam produced by a coaxially aligned milliwatt helium:neon laser.
• Diode lasers are considerably less expensive than Nd:YAG systems and are generally small and portable .
• CO₂ lasers developed for transendoscopic use require the use of fragile waveguides that can fit through the biopsy channel.

Uses

• Treatment of:
  • Pharyngeal lymphoid hyperplasia Pharynx: lymphoid hyperplasia.
  • Guttural pouch tympany Guttural pouch: tympany.
  • Ethmoid hematoma Ethmoid: hematoma.
  • Epiglottic entrapment Larynx: epiglottic entrapment.
  • Subepiglottic cysts Epiglottis: cyst - subepiglottic.
  • Intralaryngeal granulation tissue.
  • Tracheal lesions: removal of benign lesions, eg ulceration or chondromas; biopsy or debulking of malignant lesions.
  • Dorsal epiglottic abscess.
  • Nasal fungal plaques.
  • Membranous choanal atresia.
  • Dorsal pharyngeal recess polyps/lymphoid tissue.
  • Solitary pharyngeal polyps Nose: polyps.
  • Dorsal displacement of the soft palate Soft palate: dorsal displacement.
  • Endometrial cysts Uterus: cysts.
  • Aryepiglottic fold resection .
  • Ventriculocordectomy Larynx: ventriculocordectomy.

Advantages

• Most transendoscopic surgery can be performed in standing sedated Anesthesia: standing chemical restraint horse - no requirement for general anesthesia Anesthesia: general - overview.
• For peri-laryngeal surgery, additional advantage of no skin wound, eg laryngotomy or similar as is required for access to laryngeal structures using conventional open surgical techniques.
• Ability to coagulate blood vessels of various sizes (depends on type of laser being used).  
• Photovaporization of tissues.
• Excision/incision of tissues with minimal zone of tissue injury.
• Reduced post-operative pain and swelling.
• A continuous sterile incision is created (intense heat).
• Can be used down an endoscope, arthroscope or laparoscope to perform minimally invasive surgery.

Disadvantages

• Expensive equipment required.
• Health and safety issues when using laser energy Laser surgery: overview.

Technical problems

• Considerable skill required to perform techniques.

Alternative techniques

Non-contact: Nd:YAG laser only

• The fiber tip does not touch the tissue but the beam is focused and aimed.
• Useful for:
  • Vessel coagulation.
  • Indiscriminate photovaporization of bulky tissues, eg ethmoid hematomas Ethmoid: hematoma, large pharyngeal polyps.
• Not an effective means of clean incision because of substantial latent thermal effect.
• The 2.2 mm outer diameter fiber is used at 40-100 W power setting.

Contact: Nd:YAG or diode lasers

• Substantially reduces light scatter (decreases spot size).
• Requires less power per given procedure.
• Usually performed using either a synthetic sapphire probe, laser scalpel or sculpted fiber.
• The larger fibers allow the attachment of various sizes and shapes of probes and scalpels.
• The Nd:YAG Laser surgery: overview laser is used with either a chisel probe attached to a 2.2 mm outer diameter fiber or an 800 µm sculptured fiber with a conical tip.
• Diode laser fibers can be used 'bare' or 'free', ie without a probe attached.
• The basic technique for incising/excising tissue is similar for both types of fiber:
  • Slow, cautious approach.
  • Avoid adjacent normal tissue injury.
  • Light contact of the tip allowing the laser to do the work (on the surface).
  • Always have structures to be incised clearly visible with short segments of fiber projecting from the endoscope.
• If traction is required:
  • Grasping forceps should be placed up the opposite nostril.

  Spraying the nasal cavity with local anesthetic solution before introducing the forceps usually increases patient compliance.

  • Solid tissue can usually be removed without traction but is retrieved via forceps.
  • Less firmly attached/bulkier tissues, eg polyps or cysts, are easier to excise placed under traction.
• Some procedures, eg removal of large subepiglottic cysts are easier to perform:
  • Under general anesthesia Anesthesia: general - overview.
  • In lateral recumbency.
  • Intubated with a cuffed nasotracheal tube Laser surgery: overview.
  • Insert a mouth speculum and displace the soft palate.
  • Place a suction tube adjacent to the site to evacuate smoke and fluid.
  • Place the video-endoscope via the mouth.

Time required

Preparation

• Depends upon specific disease entity being treated and technique used.

Procedure

• Depends upon specific disease entity being treated and technique used.

Decision taking

Criteria for choosing test

• Previous or concurrent endoscopic examination to visualize the lesion.

Risk assessment

• Adherence or proximity of unaffected tissue to the lesion.
• Assessment of the likelihood of collateral damage