Laser Surgery

Question 1

A 71-year-old male patient is undergoing laser surgery for excision of a laryngeal lesion. He is a smoker with severe COPD and has previously had a myocardial infarction that required stenting.

What are the principles behind laser surgery?

Answer 1

• “LASER” stands for light amplifcation by the stimulated emission of radiation. It uses a focused beam of light at a particular wavelength in order to heat and destroy specific tissues.
• Laser light is particularly effective as it is monochromatic, coherent and collimated, with high-density emission of particles over a small area.
• It consists of three basic elements: a laser medium, a high-energy source, and a mirror-containing tube or space.

Question 2

Can you give some examples of medical laser types?

Answer 2

• Carbon dioxide (10,600nm) – used for heating, cutting and coagulation of tissues. Commonly used in airway surgery.
• Argon (500 nm) – the energy generated causes disruption of molecular bonds. Commonly used in retinal surgery and for the treatment of birthmarks.
• Nd:YAG (1064 nm) – causes tissue ablation. Used for the treatment of GI bleeds and tattoo removal.

Question 3

What are the concerns associated with anaesthetising this patient?

Answer 3

Patient factors:
* This is a high-risk patient with significant cardiovascular and respiratory comorbidities. He will require a thorough preoperative assessment with the relevant further investigations as directed by clinical examination e.g. ECG, echo, lung function tests and/or CPET. He may also need to stop his anti-platelet medication perioperatively, which increases the risk of stent occlusion.

• The laryngeal lesion suggests a potential for malignancy in this patient, and its associated complications e.g. malnutrition and the side effects of adjuvant treatment.
• The lesion may present with an increased risk of a difficult airway.

Surgical factors:
* Laryngeal surgery: surgical preference may necessitate a microlaryngeal tube or tubeless field, with the challenges associated with adequate oxygenation and ventilation.

• Laser surgery: poses risks to the patient and staff involved, hence adequate preparation and discussions are required preoperatively.

Question 4

The surgeon would prefer a tubeless field for this procedure. What are the options for oxygenation and ventilation intraoperatively?

Answer 4

• Manual jet ventilation (Manujet or Sanders injector).
• High-frequency jet ventilation.
• High flow oxygen delivery via nasal cannulae (THRIVE).

The above techniques are commonly used in conjunction with a TIVA-based anaesthetic. Ideally, an oxygen concentration of <30% should be used in laser surgery to minimise the risk of an airway fire developing.

Question 5

What are the complications of high-frequency jet ventilation?

Answer 5

• Barotrauma.
• Pneumothorax.
• Subcutaneous emphysema.
• Airway injury due to dry gas e.g. damage to epithelial cells,
  inflammation and oedema.
• Hypercarbia.
• Poor ventilation and hypoxaemia.
• Aspiration.

Question 6

What safety aspects need to be considered with regard to laser surgery?

Answer 6

Patient factors:
* Use a specific laser-resistant endotracheal tube (if required) with saline-filled cuffs.

• Ensure eye protection for the patient specific to the laser wavelength in use.
• Avoid nitrous oxide and aim for inspired oxygen concentration <30%.
• Avoid flammable skin prep.

Staffing factors:
* Ensure the presence of a designated laser safety officer.

• Keep the theatre locked and marked clearly when laser is in use.
• Ensure eye protection for the staff specific to the laser wavelength in use.
• Ensure matt surfaces to prevent reflection of laser light.
• Ensure the minimum amount of staff required is in theatre.
• Regular staff training and servicing of equipment.

Question 7

How would you manage an airway fire during laser surgery?

Answer 7

• This is a surgical and anaesthetic emergency.
• Alert the theatre team immediately, call for help and turn of the laser
  light.
• Stop oxygenating/ventilating the patient and remove the endotracheal tube if present.
• Flood the surgical field with water.
• Commence ventilation with 100% oxygen via a bag valve mask or re-
  intubate at this point.
• Reassess the airway (rigid bronchoscopy) and formulate a plan for
  further management, which may require intensive care and/or an emergency tracheostomy.