LASER SURGERY & ANAESTHESIA

Speaker : Dr. Rajesh Choudhuri, PGTModerator: Prof. Dr. S. Singh, H.O.D

INTRODUCTION Light Amplification by Stimulated Emission of Radiation Laser is a source of an intense beam of light that

results from stimulation of atoms (the laser medium) by electrical or thermal energy.

Laser light has three defining characteristics: Coherence (all waves oscillates synchronously), Collimation (all waves minimal dispersion & travel in

parallel directions ) and Mono chromaticity (all waves have the same well

defined narrow wavelength).

HISTORY The first laser to operate successfully was

designed by Maiman in 1960. It consisted of a ruby crystal in the form of a rod 4 cm long and 0.5 cm diameter. The ends of the crystal were polished and optically flat and parallel. One end of the rod was fully silvered and the other partially. A powerful electronic flash tube was coiled around the

ruby. Ruby consists of aluminium oxide (Al2O3) with 0.05%

chromium ions in the crystal, giving its characteristic colour.

PHYSICS OF LASER LIGHT

•Electromagnetic radiation• Einstein:

all electromagnetic radiation consisted of wavelike quanta called photons

→E (J) = h v…….[E= energy, h= plank constant( 6.63× 10-34 ),v=frequency of photon in hertz]

So, Frequency is the key to Photoelectric effect ,is independent of no of photon present .

• Wavelength for visible light ranges from 385nm to 760 nm , shorter wavelength are ultraviolet, longer wavelength are infra red.

• When atoms of the lasing medium are excited from a normal ground state into a high-energy state by a 'pumpingsource, this is known as stimulated absorption.

• When the atoms return from the excited state to the normal state, the energy is often dissipated as light or radiation of a specific wavelength characteristic of the atom (spontaneous emission). – this light emitted is likely to be

absorbed by an atom in the lower energy state.

– In a laser, the number of excited atoms is raised significantly so that the light emitted strikes another high energy atom and, as a result, two light particles with the same phase and frequency are emitted (stimulated emission).

These stages are summarized below:• Excitation: stable atom + energy —> high energy

atom• Spontaneous emission: high-energy atom —>

stable atom + a photon of light• Stimulated emission: photon of light + high

energy atom —> stable atom + 2 photons of light The light emitted is reflected back and forth many

times between mirrored surfaces giving rise to further stimulation. This amplification will continue as long as there are more atoms in the excited state than in the normal state.

A laser system has four components:

• The laser medium may be gas, liquid or solid. Common surgical lasers are CO2, argon gas and neodymium-yttrium-aluminiumgarnet (Nd-YAG) crystal. This determines the wavelength of the radiation emitted. The

Nd-YAG and CO2 lasers emit infrared invisible radiation and argon gives blue-green radiation.

• The pumping source supplies energy to the laser medium and this can be either an intense flash of light or electric discharge.

• Resonating mirror: contains mirrors used to reflect light in order to increase the energy of the stimulated emission. One of the mirrors is a partially transmitting mirror, which allows the laser beam to escape.

• The light guide directs the laser light to the surgical site. This may be in the form of a hollow tube or a flexible fibre-optic guide.

LASER SYSTEM COMPONENTS

The longer the wavelength of the laser light, the more strongly it is absorbed, and the power of the light is converted to heat in shallower tissues, e.g. CO2( wavelength 10600 nm).

The shorter the wavelength, the more scattered is the light, and the light energy is converted to heat in deeper tissues, e.g. Nd-YAG( 1064 nm).

Lasers are categorized according to the degree of hazard they afford into four classes: class 1 is the least dangerous and class 4 the most dangerous. (Surgical lasers)

Used as scalpels and

electrocoagulatorsPrecise microsurgeryRelative “dry”Less damage to

adjunct tissueLess postoperative

pain and edema

Used as scalpels and electrocoagulators Dermatology, Thoracic surgery, Ophthalmology, Gynaecology, Plastics, ENT, Urology and Neurosurgery

Clinical applications

COMMON USED LASER LIGHTSLaser media Color Wavelengt

h (nm)Typical application

Remarks

Carbon dioxide Far infrared

10,600 General, cutting Strongly absorbed by water

Neodymium:YAG Near infrared 1064 General, coagulation,

with fiberoptics

Absorbed by dark tissues,Transmitted through clear fluid,Tissue penetration 2-6 mm.

Ruby Red 694 Tattoos, nevi Absorbed by Haemoglobin,melaninTransmitted through clear fluidTissue penetration 0.5-2 mm

KTP:YAG Green 532 General, pigmented lesions

do

Argon Green 514 Vascular, pigmented lesions

do

Xenon fluoride Ultraviolet

351 Cornea, angioplasty do

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

Laser Hazards

A) Atmospheric contamination: 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

Prevention → smoke evacuator → high-efficiency masks

B) 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

c) Venous gas embolismVenous gas embolism when laparoscopic or

hysteroscopic laser surgeryAt hysteroscopy, liquid (saline) coolant is the only safe

option or if coolant gas must be used, CO2 should be considered

Continuous airway CO2 monitoringMechanical hyperventilation

D) Inappropriate Energy TransferIncidentally pressing the laser control triggerTissue damage outside of surgical siteDrape fireEye (patient or other medical staff)Endotracheal tube fires

Eye injury & protection: Effect:

CO2 laser can quickly cause a serious corneal injury Argon, KTP:Nd:YAG, or ruby lasers may burn the retina

Prevention: The lids of patients’ nonoperated eyes should be taped closed and then covered with

an opaque, saline-soaked knit or metal shield. Operating room personnel must wear safety goggles or lenses specific for the specific

laser wavelength in use. For CO2 lasers, any clear glass or plastic lenses suffice (Regular eyeglasses may be

sufficient, but contact lenses are not.) Nd:YAG lasers require special green-tinted goggles,clear lenses (Nd:YAG Protection

Glass; Surgical Laser Technologies, Malvern, PA), which have a special coating opaque to near infrared.

Argon or krypton lasers require an amber-orange lens filter, and KTP:Nd:YAG lasers require a red filter.

Because lasers other than the far-infrared CO2 produce beams that pass through glass, all windows into the operating room should be covered during laser procedures.

Endotracheal tube fires

Incidence: 0.5 – 1.5 % Source:

Direct laser illuminationReflected laser light Incandescent particles of tissue blown from the surgical

site

Modern PVC strongly absorbs far-infrared light and is very sensitive to CO2 laser energy. PVC tubes seem to be ignited much more easily by CO2 lasers than red rubber tubes , produce more toxic combustion products.

Blowtorch ignition of an endotracheal tube.

Approaches to reduce the incidence of airway fire

Reduce the flammability of the endotracheal tube Protection of the endotracheal tube Using metallic Venturi jet ventilation cannula Use intermittent apnea technique Reduction of oxygen content

Various endotracheal tubes for laser airway surgery

Type of tube Advantages Disadvantages

Polyvinyl chloride

Inexpensive, non-reflective

Low melting point, highly combustible

Red rubber Puncture-resistant, maintains structure, nonreflective, resistant to ignition,Less toxic products,

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

Wipe with alcoholProtection of endotracheal cuff: Completely cover the visible cuff with moistened cotton

pledgets.( Delaying cuff ignition). Cuff inflate with saline.

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

Bivona fome cuff(an aluminum spiral tube with an outer covering of silicone)

The use of laser-resistant endotracheal tubes requires particular care to prevent mucosal abrasions because these tubes tend to be bulkier and more rigid than conventional tubes

Laser resistant endotracheal tubes

Effect of Respiratory Gas Mixture

Combustion is more vigorous when excess oxidizer is present ( to reduce the FIO2 to less than 0.40 )

Adding nitrous oxide as a diluent for oxygen is just as dangerous as having a high FIO2.

Use of an air-oxygen mixture seems to be acceptable. Some investigators prefer helium as a diluent to nitrogen because helium has a higher thermal conductivity, which may delay the ignition of an endotracheal tube for a few seconds.

The volatile anesthetics used in clinical practice are nonflammable and nonexplosive in clinically relevant concentrations. During an airway fire, they may undergo pyrolysis to potentially toxic compounds.

Jet ventilationThis technique takes advantage of Bernoulli's principle to augment the ventilation produced by a narrow, high-speed gas stream in a Venturi tube. In practice, jet ventilation uses an intermittent high-pressure oxygen supply, directed at the glottis through a small metal tube, such as a ventilating bronchoscope or even a 12-gauge blunt needle. Side effects Barotrauma Pneumothorax Restriction to only intravenous agents Gastric distention

Intermittent apnea technique Hypoventilation Pulmonary aspiration

Other consideration: vagal hyperactivity often occurs during instrumentation of the trachea. The paraneoplastic syndrome, occasionally observed with small cell and

other types of endobronchial tumors, may lead to prolonged weakness after administration of neuromuscular relaxants.

Remove source of fire (the laser!). Stop ventilating, disconnect circuit, extubate. Disconnect the circuit from machine and circuit to et tube Extinguish fire in bucket of water (MUST have one ready!). Mask ventilate with 100% O2, continue anaesthesia. Direct laryngoscopy & rigid bronchoscopy for damage and

debris. 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

Thank

you