6: ESU laser

Question 1

Electrosurgery

Answer 1

• Currents heat tissue to achieve cutting, coagulation and desiccation
• Active electrode-
o Scapel-like
o Can be held like a pencil
o Finger switch to enable/disable power to probe
o Various shapes and sizes depending on application
• Dispersive/return electrode-
o Completes the circuit
o Reduces risk of patient burns
o Large surface area in contact with patient to reduce current density
o When current density is low, temperature is low
• Bipolar-
o Alternatively 2 active electrodes can be used in close proximity
o Current travels between the 2 = no need for return electrode
o Less tissue damage occurs
o Requires less power during coagulation

Question 2

ESU Surgical modes

Answer 2

• Cutting
• Desiccation
• Coagulation
• Blended cut- cutting without bleeding

Question 3

ESU Cutting

Answer 3

• High current through tissue = greater heat
• Cells heated so rapidly they vaporise
• Increased surface area compared to scalpel cut
• Continuous wave
• Medium current density with extended activation time

Question 4

ESU Coagulation

Answer 4

• High current density, sporadic activation time
• Short bursts = intermittent heating effect
• Cells dehydrate (desiccate) and begin to adhere to each other
• Coagulation = desiccation + fulguration

Question 5

ESU Desiccation

Answer 5

• Lower current density used
• Resistance from tissue causes cells to heat
• Cells dehydrate
• Takes place with active electrode in contact with patient

Question 6

Principles of laser surgery

Answer 6

• Laser beams are monochromatic, coherent and low dispersed
• Sharply focused down to a few cells
• When cells absorb energy from laser, they vaporise- cutting of tissue occurs
• Coagulation also possible
• Spot diameter of laser determines energy density applied to tissue
o Small spot = cutting
o Larger spot = coagulation

Question 7

Laser interaction with tissue

Answer 7

• Different tissues absorb different wavelengths
• Long i-r absorbed by water within a few cell layers = superficial effect
• Near i-r less absorbed by water, less vaporising
• Green and blue (argon laser) transmits through water and is absorbed by Hb
o Coagulates vascular or pigmented tissue
• CO2 lasers are effective at heating tissue as their produced long i-r wavelengths are absorbed by water