Anesthesia in Laser Surgery Never are cooperation and

Anesthesia in Laser Surgery

“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: v all electromagnetic radiation consisted of wavelike quanta called photons →E (J) = h v ¨ Wavelength for visible light ranges from 385 nm to 760 nm

Physics of Laser light (II) ¨ Characteristics: v Monochromatic (one wavelength) v Coherent (oscillates in the same phase) v Collimated (exists as a narrow, parallel beam) ¨ Intense light beams, intense energy to small target sites

Laser system components

Laser system components Light guide

Clinical applications ¨ Used as scalpels and electrocoagulators ¨ Dermatology, thoracic surgery, ophthalmology, gynaecology, plastics, ENT, urology and neurosurgery

Laser interaction with tissue v. Used as scalpels and electrocoagulators v. Precise microsurgery v. Relative “dry” v. Less damage to adjunct tissue v. 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

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

Atmospheric contamination ¨ Plume of smoke and fine particulates (mean size 0. 31 um) ¨ 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

Perforation ¨ 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

Venous gas embolism ¨ 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, CO 2 should be considered → Continuous airway CO 2 monitoring

Inappropriate energy transfer ¨ Incidentally pressing the laser control trigger ¨ Tissue damage outside of surgical site ¨ Drape fire ¨ Eye (patient or other medical staff) ¨ Endotracheal tube fires

Endotracheal tube fires ¨ Incidence: 0. 5 – 1. 5 % ¨ Source: – direct laser illumination – reflected laser light – incandescent particles of tissue blown from the surgical site

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

Protection of the endotracheal tubes ¨ wrapping with moistened muslin ¨ coating with dental acrylic ¨ wrapping with metallized foil tape → most popular approach v aluminum foil v copper foil v plastic tape thinly coated with metal

Cuff wrapping technique methylene blue stained saline instead of air

Disadvantages of wrapping v v v v 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

Effect of high oxygen and nitrous oxide gas mixture v Oxygen and nitrous oxide are powerful v v oxidizers Reduce Fi. O 2 to minimum concentration Helium may benefit as a diluent gas Volatile anesthetics currently used are nonflammable and nonexplosive Pyrolized toxic compounds

Metal endotracheal tubes v v 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

Jet ventilation v v v Barotrauma Pneumothorax Restriction to only intravenous agents Gastric distention Relative requirement for compliant lungs Intermittent apnea technique v Hypoventilation v Pulmonary aspiration

Airway fires protocol (I) v v v 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% O 2, continue anaesthesia i. v. Direct laryngoscopy & rigid bronchoscopy for damage and debris.

Airway fires protocol (II) v Reintubate if damage. v Blowtorch fire may need distal fibreoptic v v bronchoscopy and lavage. Severe damage may need low tracheostomy. Assess oropharynx and face. CXR. Steroids.