Electrosurgical devices Flashcards
What is the equation for voltage?
V (Volts) = I (Amperes) x R (Ohms)
What is the equation for power?
Power (Watts) = V(Volts) x R(Ohms)
Describe the difference in oscillating high frequency waveform between cut and coagulation modes in electrosurgery?
Describe the different tissue effects of electrosurgery based on temperature?
During coagulation waveforms for what percentage of the time is current available?
6% of the time, with the remaining 94% of the cycle being tissue cooling
What tissue temperatures are involved in electrosurgical tissue cutting?
Sparking between the electrode and target tissue results in tissues in excess of 100 degrees, resulting in vaporization and cell rupture.
What are the three different tissue effects based on coagulation waveform and contact type?
- Fulguration - high voltage sparking results in carbonization.
- Dessication - direct contact results in tissue dehydration and protein denaturation.
- Coaptive - lumen of vessel is occluded with instrument and application of current to the instrument results in denaturing of adventitia and collagen weld.
What are the components of a monopolar electrocautery system?
Generator, electrode, grounding pad
What size vessels can monopolar electrocautery successfully seal?
2mm
Why does liquid prevent appropriate functioning of monopolar electrocautery?
Liquid disperses the current
Does bipolar electrosurgery use higher or lower voltage and power settings compared to monopolar?
Lower power and voltage which minimizes collateral tissue damage, but prolongs application of the device.
What process is involved in coagulation with bipolar vessel sealing devices?
Vaporization as temperatures exceed 100 degrees. Carbonization can occur if temperatures exceed 250 degrees.
What are the three potential mechanisms of injury with use of monopolar electrosurgical units during MIS?
- Insulation failure
- Direct coupling
- Capacitive coupling
What size vessels are EnSeal and LigaSure able to seal?
Up to 7mm
What is the main difference between LigaSure and EnSeal?
EnSeal maintains temperatures of 100 degrees between the jaws, limiting thermal spread to 2mm. In a porcine study Ligasure collateral thermal damage extended 1-3mm.
How does the use of ultrasonic or harmonic scalpels result in coagulation?
Protein denaturation leads to formation of a coagulum that seals vessels.
What are the primary differences between ultrasonic energy systems and bipolar vessel sealing devices?
The generated current in ultrasonic energy systems create ultrasonic waves at how many vibrations per second?
55,500
What vessel size can a harmonic device reliably seal?
Up to 3mm
What is the collateral thermal damage with use of a harmonic device?
0-1 mm in a porcine model
Were bursting pressures shown to be higher in LigaSure or Enseal in one study?
Enseal
What determines the power density of a laser?
PD = power(watts)/spot size area(cm2)
What is the focal length of a laser?
The distance from the aperture to the laser’s highest power intensity (typically 1-3 mm)
What are the four basic interactions of a laser beam with tissue?
- Absorption (most important for laser tissue interactions)
- Transmission
- Scatter
- Reflection
Describe the various tissue penetrations of commonly used lasers based on wavelength.
What are the zones of injury based on proximity to the laser energy source?
- Zone of carbonization
- Zone of coagulation
- Zone of hyperthermia
What is the approximate tissue penetration of the Nd:YAG laser?
5mm
What size vessel can be sealed using a CO2 laser?
<0.6mm
