ELECTROSURGERY AND ENERGISED #

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mindmap
	root((Electrosurgery))
		Defi
			Electrosurgery
				High fz AC - heat
				Cut coagulate
			Electrocautery
				DC - heat
		Biophy
			electric current
		Types
			Monopolar
			Bipolar
  

Introduction #

Definitions #

• Electrosurgery:
  • Uses high-frequency alternating current (AC) to generate heat,
  • which is used to cut or coagulate tissue.
• Electrocautery:
  • Uses direct current (DC) to generate heat at the tip of an instrument.

Monopolar #

• Active Electrode:

  • a small, precise electrode that generates heat at its tip
  • that delivers the high-frequency electrical current to the tissue.
  • allowing for cutting or coagulating tissue at the point of contact.

• Return Electrode:

  • aka dispersive electrode or grounding pad
  • The larger electrode placed elsewhere on the patient’s body.
  • which safely return the electrical current from the patient back to the electrosurgical unit (ESU).
  • Because of its larger surface area, the current is dispersed over a wide area, minimizing heat production.

Biophysics #

What is Electrical Current? #

• Electrical Current: The flow of electrons through tissue between adjacent atoms.
• Heat Generation:
  • As the current flows through tissue, the tissue resists the flow,
  • converting the electrical energy into heat.

Principle of Diathermy #

• Electrosurgical Unit (ESU): Generates the electrical current used in electrosurgery.
• Heat Generation:
  • Depends on current density, which is the amount of current applied per ==unit area==.
  • Maximum Heat:
    • Generated where the current density is highest,
    • typically at the tip of the active electrode.
  • Return Electrode:
    • In monopolar circuits, a larger electrode placed in body,
    • dissipating the current and minimizing heat at that site.
• Temperature Rise is proportional to the time the active electrode is in contact with the tissue.

Frequency of Electrical Current #

• High-Frequency Current:
  • Used by the ESU, ranging from 200 kHz to 3.3 MHz.
• Low frequency current:
  • Used by household appliances
  • Using standard AC frequency (60 Hz) would cause unwanted neuromuscular stimulation.

Current Waveforms in Electrosurgery #

1. Cutting Waveform (Low Voltage Continuous Current) #

• Wave: Continuous, sine wave
• Time: ESU on 100% of the time.
• Voltage: low
• Effects:
  • Cutting:
    • When the active electrode is held slightly away from the tissue,
    • it quickly vaporizes the tissue.
  • Desiccation:
    • When the active electrode touches the tissue directly,
    • it dries out the cells, forming a coagulum.

2. Coagulation Waveform (High Voltage Intermittent Current) #

• Wave: Intermittent
• Time: The ESU is on only 6% of the time and off 94%.
• Voltage: High.
• Effects:
  • Coagulation:
    • Causes more heat to spread through the tissue,
    • leading to
      • protein denaturation,
      • tissue shrinking, and
      • forming a coagulum.
  • Fulguration (Spray):
    • Creates electrical arcing in coagulation mode that chars tissue over a wide area.
    • Active electrode is held slightly away the tissue
    • uses the highest voltage setting, so caution is needed.

3. Blended Waveform #

• Wave: Combination of both coagulation and cutting waveform.
• Time: The ESU is on 50% of the time and off 50%.
• Voltage: Moderate.
• Effects:
  • Provides a mix of cutting and coagulation, with varying levels of each.

Electrosurgical Circuit Types #

1. Monopolar Delivery System #

• Circuit Flow: ESU → Active Electrode → Target Tissue → Patient’s Body → Return Electrode → ESU

flowchart LR
	A[ESU] --> B[Active Electrode] --> C[Target Tissue] --> D[Patient's Body] --> E[Return 
 Electrode] -->|Current Flow| A
  

• Key Points for Placing the Return Electrode:

  • Material should be made of low-resistant material.
  • Surface Area should be large.
  • Placement Location:
    • Should be placed over well-vascularized muscle mass, avoiding crossing a joint to maximize conduction of current.
    • Ideally placed in the same quadrant as the operative site to ensure the current travels the shortest distance through the patient’s tissues.
  • Placement Condition: Ensure the electrode is not wrinkled.
  • Avoid:
    • Vascular insufficient areas.
    • High resistance areas (e.g., scar tissue, edematous tissue, bony prominences).

• Preventing Alternative Current Pathways:

  • Ensure metal prostheses and ECG electrodes are out of the circuit’s direct path.
  • Remove all metal piercings.
  • The patient should not be touching any metal part of the table.

• Newer ESUs:

  • Feature Contact Quality Monitors (CQM) that shut down the unit if the contact surface area becomes too small.

2. Bipolar Delivery System #

• Circuit Flow: ESU → Active Tine → Target Tissue (between tines) → Return Tine → ESU**

• Key Features:

  • Patient’s body does not form part of the circuit.
  • Can be safely used on narrow tissue pedicles (e.g., penis).
    • Monopolar use in such cases may cause high current densities in the pedicle, leading to thermal injury.

Safety Guidelines for Electrosurgical Units (ESU) #

1. Training and usage #

• Train all team members on the proper use of the ESU.
• Use the lowest effective power setting to minimize risk.

2. Implants #

Pacemaker Considerations #

• Avoid using diathermy with patients who have pacemakers.
• If diathermy is necessary:
  • Prefer bipolar diathermy.
• If monopolar diathermy must be used:
  • Use short bursts.
  • Place the return electrode as far away as possible from the pacemaker.
• Intraoperative
  • Ensure continuous ECG monitoring during surgery.
  • Have a defibrillator readily available in the theatre.

Warning

Pacemaker settings #

• Set the pacemaker to “maintain only” mode to prevent inappropriate shock delivery due to electrical interference.
• In Emergency Surgery If pacemaker settings cannot be adjusted, place a magnet over the ICD to inhibit shock delivery.

Cochlear Implants #

• Bipolar diathermy should be used.
• If monopolar diathermy is necessary:
  • Place the return electrode as close as possible to the active electrode.

3. Skin Preparation #

• Be cautious with spirit-based fluids as they can ignite and cause serious burns.
  • Avoid pooling of fluids in areas such as
    • the umbilicus,
    • under the drapes, or
    • around the return electrode.
  • Allow adequate time for the fluid to dry before proceeding.

Electrosurgery in Endoscopy #

1. Monopolar Snare Polypectomy #

• Pedunculated Polyps:
  • Use blended mode.
• Right Colon Polyps:
  • Exercise extreme caution due to the thinner wall, which increases the risk of perforation.

2. Sphincterotomy in ERCP #

• Active electrode: sphincterotome has a monofilament or braided wire.
• Ensure short duration of contact time with tissue to minimize damage.

3. Argon Plasma Coagulation (APC) #

• APC Overview:
  • A form of non-contact monopolar electrosurgery used for coagulation and fulguration.
  • Key Differences from Conventional Fulguration:
    • Utilizes a stream of inert argon gas passing over the tip, which gets ionized, confining the current to pass through the gas and onto the tissue.
    • Allows precision application of current to tissues.

Question

How argon plasma coagulation, coagulate a large area?

• The current follows the path of least resistance, thus avoiding already coagulated tissue, thus rapidly coagulating a larger area.

• Uses:
  • Endoscopy Setting:
    • Coagulation of superficial vascular structures (e.g., angiodysplasia).
    • Palliative ablation of tumors.
    • Hemostasis following the resection of large polyps.
  • Operative Setting:
    • Hepatic resection.
    • Retinal surgery.

Tissue Energizers: Advanced Bipolar and Ultrasonic Devices #

1. Advanced Bipolar Devices #

Electrothermal Bipolar Vessel Sealing (EBVS) Devices #

• Examples: Ligasure, Enseal
• How they work:
  • Combine bipolar current with mechanical compression
  • Can seal blood vessels up to 7mm in diameter
  • Process:
    1. High frequency, low voltage current denatures vessel wall proteins, elastin and collagen
    2. Mechanical pressure forms a coagulum (seal)
    3. Sensors in tip measure tissue impedance to ensure complete seal
    4. Energy delivery stops automatically when seal is complete
  • Tissue is then cut mechanically

2. Ultrasonic Devices #

Harmonic Scalpel #

• Converts electrical energy to ultrahigh frequency mechanical energy (55,500 Hz/second)
• How it works:
  1. Mechanical energy generates heat
  2. Heat denatures proteins, forming a coagulum to seal vessels
  3. Can seal vessels up to 5-7mm
  4. Maximum temperature: 150°C (minimizes thermal spread)
• Cutting mechanisms:
  1. Heat-induced cellular vaporization ("cavitational cutting and fragmentation")
  2. Tissue stretching beyond elastic limit

LOTUS (LaparOscopic dissection by Torsional UltraSound) #

• Uses torsional ultrasound to minimize “distal drilling effect”

3. Combined Energy Devices #

Thunderbeat #

• Uses both ultrasonic and bipolar energy
• Two modes:
  1. Seal and cut: simultaneous ultrasonic and bipolar energy
  2. Seal: purely bipolar energy for vessel sealing
• Sensors measure tissue impedance to prevent excess energy delivery

Note: Choice of device depends on preference, availability, and cost. All of above devices are almost equal in clinical trials.

Hazards of Electrosurgery #

A. Electrothermal Injuries #

General Surgery Risks #

1. Diathermy pad burns
2. Insulation failure
   • Breaks in active electrode insulation (common in distal third)
   • Current can discharge from defects

Laparoscopic Surgery Specific Risks #

• Off-camera injuries (1-5 per 1000 laparoscopies)

Direct Coupling #

• If the electrosurgical unit (ESU) is accidentally activated while the active electrode is close to another metal instrument, current can flow through that second instrument.

Capacitance Coupling #

• A capacitor forms when two conductors are separated by a non-conductor.

• An electrostatic field is created between the conductors, allowing alternating current (AC) to pass through (but not direct current).

• How It Works: The active electrode (Conductor 1) can pass current through intact insulation (Non-conductor) into an adjacent metal object (Conductor 2) like a trocar or even nearby bowel.

• Prevention: Activate electrosurgical device only after the electrode is in contact with the target tissue, the energy will go directly into the tissue.

Danger

• Don’t activate monopolar diathermy before the electrode touches the target tissue.
• the current might pass through the insulation into the adjacent conductor.

Warning

• Capacitance coupling in open surgery
  • A towel clip can cause similar issues if used to hold the electrosurgery wires.
  • If the towel clip touches the patient, it could cause burns.

B. Fire and Explosion Risks #

• Caused by alcohol-based skin preparations

C. Electrosurgical Smoke #

• Carcinogenic
• Irritates respiratory mucosa
• Can transmit viral infections

Preventing Electrothermal Damage #

• Always keep the active electrode in full view.
• Tenting Technique: Lift tissue away from surrounding structures before activating the ESU.
• When to Activate:
  • Only activate the ESU when you have a clear view of the field and the electrode is in contact with the tissue. Avoid non-contact activation.
• Power Usage: Use the lowest voltage mode necessary to achieve the desired effect. Avoid overshooting power settings.
• Handling the Electrode:
  • The tip stays hot for several seconds—don’t let it touch anything inside or outside the body. The scrub nurse should place it in a quiver.
• Single Use Electrodes:
  • Discard after one use; do not reuse.
• Consider Alternatives:
  • Use bipolar or ultrasonic electrosurgical devices if available.