Anesthesia in Laser Surgery

R1 Minghui Hung

Department of Anesthesiology, NTUH

“Never are cooperation and communication between surgeon and anesthesiologist more important than during head and neck surgery.”

Morgan, Clinical Anesthesiology

Physics of Laser light (I)

Light Amplification by Stimulated Emission of Radiation

Electromagnetic radiation Einstein:

all electromagnetic radiation consisted of wavelike quanta called photons

→E (J) = h v

Wavelength for visible light ranges from 385nm to 760 nm

Physics of Laser light (II)

Characteristics: Monochromatic (one wavelength)Coherent (oscillates in the same phase)Collimated (exists as a narrow, parallel beam)

Intense light beams, intense energy to small target sites

Laser system components

Laser system componentsLight guide

Used as scalpels and electrocoagulators

Dermatology, thoracic surgery, ophthalmology, gynaecology, plastics, ENT, urology and neurosurgery

Clinical applications

Laser interaction with tissue

Used as scalpels and

electrocoagulators

Precise microsurgery

Relative “dry”

Less damage to

adjunct tissue

Less postoperative

pain and edema

Common used Laser lights

Laser media Color Wavelength (nm)

Typical application

Carbon dioxide Far infrared 10,600 General, cutting

Ruby Red 694 Tattoos, nevi

KTP:YAG Green 532 General,

pigmented lesions

Argon Green 514 Vascular,

pigmented lesions

Xenon fluoride Ultraviolet 351 Cornea, angioplasty

Atmospheric contamination Perforation of a vessels or structure Embolism Inappropriate energy transfer

Laser Hazards

Plume of smoke and fine particulates (mean size 0.31um)

Efficiently transported and deposited in the alveoli Sensitive individuals: headaches, tearing, and

nausea after inhalation Animal study: interstitial pneumonia, bronchiolitis,

reduced mucociliary clearance, inflammation, emphysema

Prevention → smoke evacuator → high-efficiency masks

Atmospheric contamination

Misdirected laser energy may perforate a viscus or a large blood vessel

Laser-induced pneumothorax Perforation may occur several days later

when edema and necrosis are maximal

Perforation

Venous gas embolism when laparoscopic or hysteroscopic laser surgery

At hysteroscopy, liquid (saline) coolant is the only safe option

If coolant gas must be used, CO2 should be considered

→ Continuous airway CO2 monitoring

Venous gas embolism

Incidentally pressing the laser control trigger

Tissue damage outside of surgical site Drape fire Eye (patient or other medical staff) Endotracheal tube fires

Inappropriate energy transfer

Incidence: 0.5 – 1.5 % Source:

– direct laser illumination– reflected laser light– incandescent particles of tissue blown from

the surgical site

Endotracheal tube fires

Blowtorch ignition of an endotracheal tube.

Approaches to reduce the incidence of airway fire

Reduce the flammability of the endotracheal tube

Use Venturi ventilation Use intermittent apnea technique

Various endotracheal tubes for laser airway surgery

Type of tube Advantages Disadvantages

Polyvinyl chloride

Inexpensive, nonreflective

Low melting point, highly combustible

Red rubber Puncture-resistant, maintains structure, nonreflective

Highly combustible

Silicone rubber

Nonreflective Combustible, turns to toxic ash

Metal Combustion-resistant, kink-resistant

Thick-walled flammable cuff, transfers heat, reflects laser, cumbersome

wrapping with moistened muslin coating with dental acrylic wrapping with metallized foil tape

→ most popular approach aluminum foil copper foil plastic tape thinly coated with metal

Protection of the endotracheal tubes

Cuff wrapping technique

methylene blue

stained saline

instead of air

No cuff protection Adds thickness to tube Not an FDA-approved device Protection varies with type of metal foil Adhesive backing may ignite May reflect laser onto non-targeted tissue Rough edges may damage mucosal surfacess

Disadvantages of wrapping

Oxygen and nitrous oxide are powerful oxidizers

Reduce FiO2 to minimum concentration

Helium may benefit as a diluent gas Volatile anesthetics currently used are

nonflammable and nonexplosive Pyrolized toxic compounds

Effect of high oxygen and nitrous oxide gas mixture

Norton. spiral wound stainless steel ETT Bivona Fome-Cuff. aluminium spiral tube with

a silicone polyurethane foam cuff Xomed Laser-Shield. silicone elastomer tube

containing metallic powder Mallinckrodt Laser-Flex. airtight stainless

steel spiral wound tube with two PVC cuffs

Metal endotracheal tubes

Barotrauma Pneumothorax Restriction to only intravenous agents Gastric distention Relative requirement for compliant lungs

Jet ventilation

Intermittent apnea technique Hypoventilation Pulmonary aspiration

Remove source of fire (the laser!). Stop ventilating, disconnect circuit, extubate. Extinguish fire in bucket of water (MUST have

one ready!). Mask ventilate with 100% O2, continue

anaesthesia i.v. Direct laryngoscopy & rigid bronchoscopy for

damage and debris.

Airway fires protocol (I)

Reintubate if damage. Blowtorch fire may need distal fibreoptic

bronchoscopy and lavage. Severe damage may need low

tracheostomy. Assess oropharynx and face. CXR. Steroids.

Airway fires protocol (II)

I am a sheep.

SHEEP me 2.

We wish you…

羊 羊 得 意