Lecture Notes: Energy in the Operating Room

Overview

• Focus on Chapter 6 from ST4ST.
• Discussion on the use of energy in surgical procedures, specifically for cutting, cauterizing, and coagulating tissue.

Methods of Cutting Tissue

Scalpel

• Traditional method: slicing through tissue manually.
• Limitations: less precise, potential for excessive bleeding due to blood vessel damage.

Energy Sources

• Uses heat to vaporize and cut tissue.
• Advantages:
  • Precision in hard-to-reach areas.
  • Seals blood vessels while cutting, reducing bleeding.
  • Control over the depth of cauterization.

History and Technology

• Originated with W.T. Bovey in the 1920s.
• Evolution from spark gap generators to modern Electrosurgical Units (ESU).

Basic Physics of Electricity

Atomic Structure

• Atoms composed of protons, neutrons, electrons.
• Free electrons can wander between atoms.

Electrical Concepts

• Current: Flow of electrons, measured in amperes.
• Electrical Potential (Voltage): Pressure/strength of electrons, measured in volts.
• Energy: Combination of current and voltage, measured in joules.
• Power: Number and strength of electrons per second, measured in watts.

Ohm's Law

• Describes relationship between current, voltage, and resistance.

Components of an Electric Circuit

• Power Source: E.g., battery.
• Load: E.g., light bulb, the component doing work.
• Switch: Controls power flow.
• Connection: Made using wires (conductors and insulators).

Conductors and Insulators

• Examples: Copper (conductor), Plastic/Air (insulators).
• Dielectric Breakdown: Insulator becomes conductor under high voltage.

Applications in Surgery

Electrosurgical Unit (ESU)

• Monopolar ESU: Common in surgeries.

  • Uses grounding pad for complete circuit.
  • Risks of burns if grounding pad is not placed properly.

• Bipolar ESU:

  • Uses bipolar cautery forceps.
  • Safer, as it contains circuit within the handpiece.
  • Better for precise coagulation, less effective for cutting.

Alternative Energy Sources

• Mechanical Energy: Ultrasonic vibrations (Harmonic Scalpel) create friction for cutting/cauterizing.
• Light Energy (Lasers): To be discussed in the next lecture.

Safety and Practical Considerations

• Importance of grounding pad placement to prevent burns.
• Consideration of conductive materials in OR to avoid induced currents and potential sparks.
• Use of capacitance pads for safer energy induction.

Additional Concepts

• Direct vs Alternating Current:
  • Direct Current (DC): Flows in one direction (e.g., batteries).
  • Alternating Current (AC): Changes direction, found in wall outlets.
• Frequency: Rate of direction change in AC, measured in hertz.