Chapter 15: Energy Sources: Electrosurgery and Lasers Flashcards
Define electrical voltage, current and resistance and how they relate in regards to Ohm’s law:
- Volatage (V) = the difference in potential between two points. (The force that drives particles across a potential difference). Volts
- Current (I) = Represents the flow of electons. Amperes
- Resistance (R) = The impedence to the flow of the electrons. Ohms
Ohm’s Law: V = IR or 1 volt = 1 amp x 1 ohm
What is power?
Power is the work performed expressed in watts
W = VI =RI^2
What is the difference between electrosurgery and electrocautery?
- Electrosurgery = Passing an electrical current from an instrument through tissues in order to achieve a desired result
- Electrocautery - Using electrical current to heat a metal instrument first before applying it to a targeted area
What are differences between radiowave surgery and electrosurgery?
- Radiowave uses current in the higher frequency range (>4MHz as compared to 500kHz)
- Less tissue penetration
- Less lateral tissue damage
- No ground plate required
How does pure cut mode on monopolar devices work in terms of waveform?
- Current is delivered uninterrupted 100% of the time (and therefore V is low as W=VI)
- Best cutting achieved with electrode held slightly away from tissue
- Generator power settings 50-80W
How does coagulation mode work in terms of waveform?
- Series of interrupted waves at a higher voltage than cut mode
- Generator power setting 30-50W (spikes of V as high as 9000V can be produced at 50W)
What percentage of the time is current available due interrupted coagulation waveforms?
- Current is available 6% of the time to heat the tissue.
- Remaining 94% of the time the tissue cools to produce a coagulation effect
What are fulguration, desiccation, and coaptive coagulation?
- Fulguration coagulation - holding the electrode slightly away from the tissue with a resulting arc and spark. Good if a discrete bleeder cannot be identified.
- Desiccation Coagulation is achieved by direct contact of the electrode and tissue. Heats tissue more efficiently with deeper necrosis and thermal spread.
- Coaptive coagulation is a type of desiccation coagulation which occurs when the lumen of a vessel is occluded by a metal instrument (Collagen weld)
What are some advantages / disadvantages of monopolar electrosurgery?
Advantages:
Commonly available
Hemostasis for vessels <2mm
Disadvantages:
- Does not function well in liquid
- Potential for burns at grounding pad
- Increase in histopath scores of wound inflammation
- Delays in wound healing
What are some advantages and dsadvantages of bipolar electrosurgery?
Advantages
- Much more precise
- Can be used in a wet environment
- Lower voltage and power setting
- Cosidered to be safer
Disadvantages
- Increased time for coagulation
- Charring and adherence can lead to tearing
- Limited use for dissection and ineffectual for cutting
What are the main mechanisms of injury when using electrosurgery devices in minimally invasive surgery?
- Insulation failure (reuse issue)
- Direct coupling (touches another metal instrument)
- Capacitive coupling - When 2 conductors or instruments are seperated by an insulator (air) and form stored energy
What size vessels is the LigaSure approved for?
- Blood vessels 7mm or smaller and tissue as big as fits in jaw
List benefits of the Harmonic Ultrasonic device over electrosurgical units:
- Simultaneously cuts and coagulates tissue
- Lower temperatures (50-100C vs 150-400C)
- Minimal lateral thermal spread
- Virtually no charring, desiccation or sticking
- Reduces smoke and vapour
However, does not reliably seal vessels >3mm
What does laser stand for?
Light Amplification by Stimulated Emission of Radiation
What are the characteristics of a laser beam?
- Monochromic (photons of the same waveform)
- Spatial coherence (parallel photons)
- Temporal coherence (photons in phase with each other)
- Collimated (travel in a linear direction)
These photons will have consistent energy released at the same wavelength, amplitude, frequency and time allowing it to be focused 100x better than ordinary light
