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LASER
• Light Amplification of the Stimulated Emission of Radiation
• Intense controlled beam of light• Characteristics : - coherence (one phase) - collimation ( parallel direction) - Monochromaticity (same wavelength)
Apparatus
• Lasing medium• External source of energy - Pumping• Unstable potential energy – Population
reversal• Release of quantum of energy – photons
of light• Reflected through a long resonator• Exit through a mirror
Effect of Laser
• Thermal effects depend on - Energy density - Flux• Temperature
Thermal effect on tissues
Below 55ºc slight destructive shrinking
Above 55ºc welding of cell walls
60ºc early denaturation of cell
protiens
100ºc cell water boils and vaporises
Types of Lasers• Argon gas - ophthalmic photocoagulation, skin lesions, angioplasty, stapedectomy• CO2 gas - cutting & vaporising• Liquid dyes - angioplasty• Excimer gas - angioplasty, radial keratotomy• Krypton gas - photocoagulation• Nd-YAG solid – coagulation, heating of tissues for haemostasis • erbium:YAG• Thulium• Holmium:YAG (Ho:YAG)
CO2 Lasers
• HeNe used as an aiming co-axial laser• Laryngeal laser surgery (e.g., laryngeal
condylomata, papilloma’s and tumors)• Long wave length (10.6 um) • Total absorption in the first few cell layers • Accurate vaporization with minimal
peripheral injury• Best precision (0.2mm) • Cannot be used through a fiberoptic scope• Errant beams can result in corneal damage• Can be stopped with any clear lens material
Nd-YAG lasers
• Neodymium-yttrium aluminum garnet (Nd-YAG)• Invisible• Coagulation of hemorrhagic lesions (necrotic
respiratory tumors and GI varices)• Wave length of 1.06 um• Penetrate tissues causing deep damage with
more thermocoagulation and less vaporization• Can be used through a fiberoptic scope• Penetration is variable with a greater potential
for damage to normal tissue
Holmium:YAG (Ho:YAG)
• Precise cutting with minimal damage to adjacent tissue
• Fiberoptic delivery (which is ideal for endoscopic use)
• Treats tissue in a liquid-filled environment (e.g., saline, blood).
Argon Laser
• Blue-green light • Short wavelength of 0.6 um• Primary use for pigmented structures
(hemangiomas, port wine stains, retinal surgery)
Diode laser• 980-nm wavelength • Fiberoptic delivery system • Tissue-cutting effect comparable to CO2
laser• Coagulation effect comparable argon laser• Higher degree of absorption by tissue than
Nd:YAG laser• Large (up to 10 mm) penetration depth in
biologic tissue• Ideal for photocoagulation
Advantages of laser surgery
• Precise • Selective absorption • Minimal pain, scarring and edema • Remote alteration of tissues• Easy transmission through
endoscopes
Applications
• Laparoscopy• Endoscopy • Thoracic surgery• Ophthalmology• Gynecology• Plastic surgery• Urology• Neurosurgery • ENT
Laser in Urology• Nd:YAG, Ho:YAG, KTP, diode sources• Lasers for benign and neoplastic tissue
coagulation and vaporization - Prostatectomy - Transitional cell carcinoma of bladder, ureter, and renal pelvis - Renal, adrenal. genital and urethral tumors • Laser incision of ureteropelvic junction,
ureter, and urethral strictures • Laser lithotripsy
General safety considerations
Patient• Protection of eyes, nose, moustache/ beard • No eye ointments / No metal eye cups• No plastics• Cloth adhesive tape/ Wet with high porosity• Avoid tincture benzoin• Tissue cleansing agents should be wiped off
General safety considerations
Operating Room
• Eye shields for OR personnel• Wave length specific glass inserts on
windows and doors• Signs identifying laser use • Drapes and towels – cloth with high
porosity / wet • Fire extinguisher, water bucket
RecommendationsAmerican National Standards for the Safe use of Lasers
in Health Care Facilities I All persons should be aware of areas of laser
use, and controlled access to these areas must be maintained
• Nominal hazard zone is identified to prevent unintentional exposure to the laser beam
• Regulation laser signs should be placed at all entrances to laser treatment areas
• Doors in the nominal hazard zone should remain closed and windows--including door windows--should be covered as appropriate to the laser used
• The nominal hazard zone should be occupied only by authorized persons (including patients) or health care personnel approved by the laser safety officer.
II Everyone in the nominal hazard zone should
wear appropriate eyewear• All personnel in the nominal hazard zone should
wear protective eyewear, labeled with the appropriate optical density and wavelength for the laser in use
• The patient's eyes and eyelids should be protected from the laser (eg, wet eyepads, laser protective eyewear, laser specific eye shield)
III All persons in the laser treatment area should be protected from laser beam exposures to their skin and other nontargeted tissues• Exposed tissues around the operative site should be
protected with saline-saturated or water-saturated fire/flame-retardant materials (eg, towels, sponges) when thermally intensive lasers are being used. These materials should be remoistened periodically to ensure proper protection
• Anodized, dull, nonreflective, or matte-finished instruments should be used near the laser site
• When a fiber is used to deliver laser energy through an endoscope, the end of the fiber must extend at least I cm past the end of the endoscope
IV Exposure to smoke plume generated during laser
surgery should be reduced by implementing a
variety of engineering controls• Smoke plume inhalation should be reduced by
implementing various controls that include but are not limited to the use of
* high-filtration surgical masks, * wall suction units with in-line filters, and * smoke evacuator units.
Laser Plumes
• Carbonised tissue,blood and virus(0.1-0.8µm)
• Occupational Hazard (National Institute for Occupational Safety and Health)
• Hydrocarbons, including acetone, isopropanol, toluene, formaldehyde, and cyanide
• Smoke plume - respiratory irritation - viral infection - mutagenic and carcinogenic potential.
V All persons in the laser treatment area should be protected from flammability hazards associated with laser usage.
• Personnel using lasers should be aware of the fire hazards associated with laser use. Items with the potential for causing fire, bums, or explosions include
* flammable liquids or combustible ointments (eg, skin prep solutions, oil-based lubricants),
* gases (eg, oxygen, methane, anesthetic agents),* plastics,* electrical failures,* paper or gauze materials,* surgical drapes,* adhesive or plastic tapes, and endotracheal tubes
• Fire extinguishers and water/saline should be immediately available where lasers are used.
• Special fire/flame-retardant drapes or moistened, reusable fabrics should be used to drape around areas that are close to the laser treatment site
• An endotracheal tube used during laser procedures in the patient's airway or aerodigestive tract should have protection or be specially designed to minimize the potential for fire.
VI All persons in the laser treatment area should be protected from electrical hazards associated with laser use
• Visual inspection of laser equipment should be performed by the laser operator after setup
• Laser service and preventive maintenance should be documented
VII Personnel working in the nominal hazard zone
should demonstrate competency commensurate
with their responsibilities• Laser safety programs should include but not be limited* to delegation of authority and responsibility for the
supervision of laser safety to a laser safety officer or his/her designee;
* criteria and authorized procedures for all health care personnel working in nominal hazard zones;
* identification of laser hazards and appropriate control measures;
* management and reporting of accidents or incidents related to laser procedures, including action plans to prevent reoccurrences; and
* fundamentals of laser physics, tissue interaction, instrumentation, and delivery systems
VIII Policies and procedures for laser safety should be developed with regard to individual practice settings, applicable standards, and federal and state regulations. They should be reviewed periodically, revised as necessary, and readily available to all personnel.
Laser airway surgery
Endotracheal intubationAdvantages • secured airway• ability to monitor ETCO2 and O2 conc.• decreased risk of soiling the distal airway with
debris, blood, or gastric contents.
Disadvantages • risk of an ETT fire, • high AWP• high resistance with spontaneous ventilation• difficulty in suction
Special ETTs for use in laser surgery
• Red rubber and PVC tubes are at risk of burning
• PVC tubes - 3.7 seconds / red rubber tubes - 16.5 seconds
• Low cost alternative – aluminium foil wrap - cover cuff with moist gauze - methylene blue in saline for cuff
inflation
Special ETT’s• Norton - coiled metal rings without cuff• Bivona Fome-Cuff - aluminum tube coated
with silicone with polyurethane foam cuff• Xomed Laser-Shield - silicone and non-
reflecting metal particles• Malinckrodt Laser-Flex - coiled and flexible
metal rings with two distal plastic cuffs• Sheridan Laser-Trach - red latex covered
with atraumatic screen with latex distal cuff
• Rusch Lasertubus – porous sponge coating and doublee cuff (one inside other)
Laser airway surgery
Without Endotracheal intubation• Ventilating bronchoscope• Jet ventilation - Sander’s injectorAdvantages• Surgical convenience• No risk of ETT fire
Laser airway surgery
Disadvantages• Unable to monitor pCO2• Contamination of lower resp. tract
Intermittent endotracheal intubation
Airway Fire
Combustion• Flammable substrate• Oxidant• Speed of combustionIncidence - 0.5 – 1.5%
Airway Fire
Prevention• Non flammable substrate / jet ventilation• Reducing O2 (30%)• Avoid N2O• Helium (high thermal conductivity)• Avoid Flash point(below critical temp.)
Airway Fire
Management of an airway fire:• Plan ahead, review plan with team.• Immediately stop ventilation.• Disconnect circuit (blow torch effect with
flaming ETT and 02 flow).• Remove and extinguished flaming ETT in a
bucket of water.• Extinguish any flaming debris in pharynx
with water or saline.
• Reintubate, ventilate with 100% O2, flush pharynx with cold water.
• Flexible and rigid bronchoscopy to assess damage and remove debris.
• consider steroids, humidified gases, and prolonged ventilation in ICU.
• Consider tracheostomy if severe lower airway burn.
• Monitor CXR, ECG, and ABG's.
Anesthetic considerations
• surgical procedure• Patient’s pre-existing conditions • Hazards of laser surgery to the patient, OR
personnel and equipment
Anesthesiologist must be aware of• Laser medium • Physical properties• Vital structures around the point of focus• Iceberg effect
Anesthetic plan
• Preoperative evaluation of the airway (stridor, voice quality, ventilation pattern, flow volume loops, CT, MRI, or fiberoptic airway evaluation)
• Mutual planning with the surgeon.• Aspiration prophylaxis• Total iv anesthesia (propofol, remifentanil,
short acting relaxant)• Xylocaine spray
• Tooth guard.• Methylene blue in ETT cuff.• Saline gauze protection of face and airway
and keep mucosal surfaces moist • Laser should be used in short repeated
bursts (pulse), rather than in a prolonged continuous mode.
• Communicate and monitor video camera for signs of airway fire.
• O2 < 30% using an air-oxygen mixture, avoid N2O and volatile anesthetic agents.
• Transcutaneous CO2 monitoring if available may be helpful.
• Esmolol and NTG immediately available for patients with CAD risk factors.
• smooth emergence with minimal bleeding, coughing or laryngeal spasm
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