Low energy ultrasound used for imaging
High energy ultrasound used to produce thermal and cavitation effects on tissue
Harmonic scalpel is ultrasonic vessel sealer
Mechanism:
- Electrical energy is converted to mechanical energy and sound waves by a piezoelectric crystal in the handpiece
- Mechanical vibrations are amplified and transmitted to the vibrating (active) tip of the instrument which vibrates at 50 000 Hz, creating thermal energy
Effects:
- Cavitation – transmission of high frequency vibrations to the tissue -> rapid volume changes and vapour bubbles
- Coagulation – high temperatures cause protein disruption and denaturing, forming a coagulum which seals small vessels
- Cutting – rapid stretching of tissue beyond its elastic limit by the rapidly vibrating tip
Benefits:
- No transmission of electrical energy through patient
- No charring or smoke
- Less thermal spread
- No risk of coupling
Risks:
- Hot blade remains hot after use
Ligasure is just an advanced bipolar device but with some benefits:
- Pressure based sealing as well as energy based
- Pulsative energy delivery minimises lateral spread
- In built blade allows cutting after sealing and coagulum formation
- Reports up to 7 mm diameter vessels being sealed
Staplers
Usually combined with linear cutting device.
EndoGIA Universal stapler
- 30, 45 or 60 mm length reloads
- Each cartridge has new blade
- Two triple staggered rows of staples, simultaneously cuts between the rows
- 5 mm staples (white or tan, vessels), 3.8 mm staples (blue, bowel), or 4.8 mm staples (green, giant)
- 15 mm increments of compression, stapling and transecting with each squeeze
- Note only staples and cuts within marked areas
- Do not fire across previous placed clips
Non cutting staplers (endo-TA) can be used for donor nephrectomy or to repair enterotomy.
GIA DST stapler for bowel in open procedures
- 60, 80 or 100 mm length reloads
- Two staggered rows of staples and simultaneously cuts between rows
- Same staple sizes as endoGIA – 2.5 mm (white, vessels), 3.8 mm (blue, bowel), and 4.8 mm (green giant)
Clips
Non locking titanium clips or locking polymer Weck clips.
Principles of clips:
- Complete circumferential dissection of vessel
- Visualised of tip of clip beyond vessel
- Confirm tactile snap of clip when placed
- 2 clips on stay side
- Clips placed perpendicular to vessel or pedicle