Energy devices

Abhilash

Energy sources in surgery

• Electrical• Ultrasonic• Laser• Mechanical

Electrosurgery

• 1926- Cushing and Bovie• Alternating radiofrequency current.• 500,000 to 2 million Hz.• Electrocautery is not same as

electrosurgery.

Physics of electrosurgery

• Current takes path of least resistance.

• Tissue containing maximal water has least resistance.

• Energy density – amperes/cm2

Ohms Law

• I= V/R• Current = I : flow of electrons/time

(amps)• Resistance (Impedance) = R :

Obstacle to the flow of current (ohms)

• Voltage = V: force pushing current through the resistance (volts)

• Power = V x I (watts)

Types of electrosurgical circuits

• Monopolar.• Bipolar.

Monopolar

• ADVANTAGES– Ease of use– Cutting and coagulation currents– Dissecting capability.

• DISADVANTAGES– Larger volume of tissue injured.– Interferes with electrical implants.– Requires ground pad.

Bipolar

• ADVANTAGES.– Small volume of tissue injured.– Less risk of burns.– Safe with electrical implants.– Effective in wet fields.

• DISADVANTAGES–More skill required.– Coagulation only.– No dissecting capability

Electrosurgical effects

• Cutting.• Coagulation and fulgration.• Dessication.

Cutting

• Non contact activity.• Non modulated sine wave almost

100 percent of time – best for cutting.

Fulgration and coagulation

• Non contact.• Short bursts of high voltage with

pauses. • Cause coagulative necrosis of tissues

and fluid.

Dessication

• Tissue is heated and water in the cell dries out.

• Can use cutting or coagulation current by contact with tissue.

Complications of electrosurgery

• Direct coupling – Active electrode in contact with metal instrument.

• Capacitative coupling – current is transferred from the active electrode to nearby tissue through the intact insulation

• Insulation failure.

New generation

• Higher current, less voltage.• Less thermal spread.• Impedence feedback, end point

feedback.• Grasp, dissect, coagulate and

transect.• More efficient but costly.

Newer energy sources

• Advanced Bipolar devices.– Gyrus ACMI (Olympus)– Enseal (Ethicon Endo-Surgery)– Ligasure (covidien)

vessel sealing

• Ultrasonic scalpel– Harmonic scalpel ( Ethicon Endo-

Surgery)

Gyrus ACMI

• Plasma kinetic energy delivered in pulses

• Intermittent tissue cooling prevents thermal damage and sticking.

• 2 modes– Vapor pulse coagulator– PK cutting

• Audible impedence and end point indicators.

• PK energy to tissue forms vapor zonescurrent passes around the vapor zone vapor zone collapses causing tissue sealing

Enseal

• Adjusts energy according to tissue impedance.

• Smart electrode technology – millions of nano conductive particles each with discrete thermostatic switch.

• Each particle interrupts current flow to a specific tissue when temperature rises.

• If temperature below fusion level particle turns back on.

• Less heat required. Tissue volume reduced by compression.

• Vessel walls fused by compression, protien denaturation and then renaturation.

• Seals upto 7 mm vessels. Thermal spread 1 mm

• Withstands upto 7 times systolic pressures.

Ligasure

• “Electrosurgical collagen welding” combination of pressure and energy denature collagen and elastin permanent seal.

• Hydrothermal rupture of collagen cross links

• 60-90 degree C.

• Cooling allows renaturation of entangled unwound collagen strands.

• High uniform mechanical compression increases entanglement/ recross linking upon thermal relaxation.

• Permanently fuses tissue and vessels without dessication.

• Average seal cycle is 2-4 sec.• Seal can withstand upto 3 times

normal systolic pressure.• Can ligate vessels upto 7 mm.• Impedence feedback – adjust energy

levels according to tissue impedence.• Feedback controlled response system

to detect end of seal cycle.

Harmonic Scalpel

•  Converts ultrasonic energy→mechanical energy.• Piezoelectric crystal produces

~55000 vibrations per second.• Lysis of H-bond → heat →

denaturation of protien → separation of tissue.

•  Tissue separation at 50-60 degree C.

Settings on a harmonic scalpelHigher the setting → longer excursion

of the blade --> more mechanical energy more cutting speed/more thermal energy

Advantages of harmonic scalpel

• Minimal thermal spread.

• No dessication or charring of tissue.

• No risk of electrical injury

• No smoke.

Clipless lap cholecystectomy uses a harmonic scalpel.

Disadvantages of harmonic scalpel

• inability to coagulate vessels greater than 5mm.

• Operator dependence of settings of the blade according to tissue.

• Increased cost.

Types of harmonic scalpels

• ACE curved sheers• Coagulating sheers• Harmonic focus• Dissecting hook

CUSA

• Cavitron ultrasound surgical aspirator.

• Causes cavitational fragmentation of cells.

• Ultrasonic generator at 23000 Hz.• With coupled powerful aspiration

device.• Used in liver surgery and

neurosurgery• No coagulation or cutting.• Only tissue gets fragmented.

Surg Endosc. 2009 Jan;23(1):90-6

Surg Endosc. 2009 Jan;23(1):90-6

Surg Endosc. 2009 Jan;23(1):90-6

• Harmonic scalpel has the least thermal spread.

• Ligasure is the highest rated.

J Endourol. 2008 Oct;22(10):2307-12

Sealing time (s)

Burst pressure (hg mm)

Smoke/visibility (ppm)

Harmonic scalpel

14.3 204 2.88 ppm

Ligasure V 10 385 12.5 ppm

Gyrus PK 11.1 290 74.1 ppm

Enseal 19.2 255 21.6 ppm

Argon beam coagulator

• Inert, non combustible, easily ionisable.

• Used along with monopolar electrosurgery.

• Electric current ionises argon facilitates current flow.

• Not suitable for laparoscopy.

LASER

• Precise application of energy.• Less lateral damage and stray

currents.• Energy induces molecular vibration

and thermal vibrations.• Mediums – CO2, Argon, NdYAG.

Microwave ablation

• Generator probe at 2450 MHz.• Created alternating electrical field

induces motion of polar molecules kinectic energy converted into heat coagulation necrosis.

• Applications – liver, prostatic hyperplasia, endometrial bleeding, partial nephrectomy.

• Only small area ablated.

Radiosurgery

• Gamma knife used in neurosurgery.• High energy gamma radiation

arranged in circular fashion.• Focussed stereotactically

• THANK YOU.