Surgical Technology: Electrosurgery, Lasers, and Microbiology Study Guide
Electrosurgical Principles and Electrical Safety
Electricity serves as a fundamental source of power used to perform work in the surgical environment. Key electrical concepts include voltage, which is the pressure that pushes the flow of charged electrons through a circuit. As the voltage increases, so does the ability to push a greater number of electrons along the circuit. Wattage represents the total amount of electrical power a device either consumes or generates. Current is defined as the continuous flow of charge, and a single alteration cycle is defined as one complete degree sequence of an electrical waveform. In the context of electrosurgery, radiofrequency electromagnetic energy is utilized, which includes waves in the frequency area of radio transmission, to achieve specific surgical effects on tissue.
Tissue reacts to electrosurgical energy based on several determining parameters. The tissue type is critical, specifically the density and the amount of water and collagen present. Exposure time, or the duration of contact with the electrical current, also dictates the outcome. Current density is another vital factor; as density increases, the tissue response intensifies. Current density specifically increases when voltage is forced through a relatively small area. Ultimately, specific combinations of frequency and voltage determine the distinct effects produced in the tissue. For instance, to coagulate blood vessels, an electrode is held in contact with or slightly above the tissue, causing slower heating than cutting mode, which results in tissue "welding" and coagulation.
Monopolar and Bipolar Circuitry Systems
A monopolar circuit in electrosurgery consists of a continuous path of electricity flowing from the electrosurgical unit (ESU) to the active electrode, through the patient's body to a patient return electrode (PRE), and then back to the ESU. The active electrode in a monopolar system must always be used in conjunction with a PRE. The PRE, also known as the dispersive electrode, is a conductive pad or adhesive patch (often metallic and coated with conductive gel) that captures electricity and shunts it safely out of the body to prevent unintended heating or burns. A common cause of patient burns is the failure to properly attach the PRE to both the patient and the generator.
Proper placement of the PRE is essential for safety. It must be positioned close to the surgical site over a large muscle mass, as muscle has low impedance and serves as the best conductor. It must never be placed over prominent bony surfaces, scars, tattoos, hair, or fatty tissue, as these materials increase impedance and heighten the risk of burns. Safety is further enhanced by the Return Electrode Monitor (REM) alarm, a system where the PRE provides continuous feedback on impedance quality. If impedance reaches dangerously high levels, the REM system automatically stops the current.
Bipolar electrosurgery differs in that it uses lower voltage than monopolar surgery, making it a safer technique with fewer risks of injury. In a bipolar unit, the current does not pass through the patient's entire body, as it only travels between the two poles of the instrument. This makes it suitable for patients with implanted electronic devices (IEDs), such as pacemakers. Because the low voltage cannot easily penetrate dense tissue like bone, bipolar surgery is mainly used on low-impedance tissue. This technique is ideal for delicate areas such as the brain and microvascular tissue due to minimal heat spread to surrounding areas.
Specialized Electrosurgical and Surgical Modalities
Fulguration, also referred to as spray coagulation, is achieved through the pulsed or intermittent application of the active electrode. Argon gas can be used in some electrosurgical procedures to focus the current during cutting and coagulation. Argon is an inert, nonflammable gas that is easily ionized, making it particularly useful during long fulguration procedures that require extended electrosurgery. Additionally, various vessel-sealing systems like LigaSure and ENSEAL are available for specific use in gynecology and general surgery.
Other surgical technologies include the Cavitron Ultrasonic Surgical Aspirator (CUSA), which is commonly employed for ultrasonic ablation and aspiration (suction) during tumor surgery. Phacoemulsification is a specialized process used in ophthalmology, where a phacoemulsifier uses ultrasonic energy to destroy cataracts. Cryoablation involves inserting a probe into a tumor or tissue mass to destroy it via extreme cold. Ultrasonic energy in these contexts is created when electricity is transformed into mechanical energy through high-frequency vibrations and frictional forces.
Fundamentals of Laser Technology and Tissue Effects
Laser light is characterized by intense, precisely focused energy used to cut and coagulate tissue. These characteristics are created when light is pumped into a sealed chamber filled with a laser medium, which can be a solid, gas, or liquid. A laser medium is sensitive to atomic excitation by an energy source, resulting in intense light. Radiant exposure refers to the specific combination of the concentration of laser energy and the duration of tissue exposure. Lasers can be applied continuously or as pulsed-wave (also called Q-switched) lasers, which apply light intermittently to the target site.
When laser light interacts with a surface, four primary actions can occur: absorption, reflection, scattering, or transmission. The reaction of tissue depends on the laser wavelength, the power setting, and the absorption quality of the cells, including their density, color, and moisture content. Selective absorption is a critical feature where certain cells absorb the lasing medium based on color and density while others do not. This specificity prevents the spread of heat and damage to tissue surrounding the target area.
Specific Laser Media and Safety Protocols
Lasers are distinguished by the media activated to transmit photons. Common media include gases, solids, semiconductors (diode lasers), excimers, solid-state media, and liquid dyes. The Holmium:yttrium-aluminum-garnet (Holmium:YAG) laser is a solid crystal containing holmium, thallium, and chromium. It produces a beam outside the visible light range that can penetrate a wide variety of substances, including renal and biliary stones as well as soft tissue. It is used in urological, orthopedic, gynecological, gastrointestinal, general surgery, and ear, nose, and throat (ENT) procedures.
Other notable lasers include the Carbon Dioxide () laser, which is invisible and has a high affinity for water, functioning at a superficial depth. It is extremely versatile and used in microsurgery. The Argon gas laser produces a visible blue-green beam absorbed by red-brown pigmented tissue like hemoglobin. The Potassium-titanyl-phosphate (KTP) laser is a low-power medium suited for microsurgery due to its very small diameter beam. Krypton is another gas medium used in dermatology for removing superficial lesions. Safety is paramount during laser surgery; for example, when operating on the neck or airway, a light-reflective endotracheal tube is required to prevent airway fires in oxygen-rich environments.
Surgical smoke plume, emitted during both electrosurgery and laser surgery, is toxic and contains both living and dead cells. The transmission of diseases through the smoke plume is a known risk to personnel, and the presence of other biological particles, such as cancer cells, is an additional concern for surgeons and staff.
Microbiology, Staining, and Culture Media
To identify specific bacteria, a sample must be grown outside the body in a process called a bacterial culture. Identification often begins with Gram staining, which differentiates bacteria into two primary groups: gram-positive and gram-negative. Gram-positive bacteria have a thicker cell wall that retains the stain, appearing purple under a microscope. Gram-negative bacteria have thinner walls that do not absorb the initial stain and appear red or pink. Objective lenses on standard laboratory microscopes typically include , , and magnifications.
Different types of culture media are used depending on the needs of the specimen. Anaerobic media support only bacteria that grow without oxygen. Complex media contain various proteins to promote growth but lack specific measured substances. Defined media consist of specific recipes and substances. Differential media support the growth of some bacteria while inhibiting others, and selective media are designed for individual types of bacteria. Transport media are used strictly for moving specimens to the lab for later culture. A culture and sensitivity test is performed to identify harmful germs and determine the most effective medication for treatment.
Infectious Diseases and Clinical Practice
Hospital-acquired infections (HAI), or nosocomial infections, are acquired while a patient is in a healthcare institution. The most common HAI is a urinary tract infection (UTI) resulting from catheterization. Surgical site infections (SSI) are most commonly caused by Staphylococcus aureus. Some microbes exist in symbiotic relationships; mutualism is a relationship where both organisms benefit, such as S. aureus living on healthy skin. Commensalism occurs when one organism uses another for physiological needs without harming the host, as seen with E. coli. Other pathogens include Candida albicans, the fungus responsible for vaginal yeast infections.
In the clinical environment, RID technology is used to increase workflow efficiency rather than replace it. Digital files facilitate the easy updating of preference cards, which contain specific instructions for room setup, patient positioning, instrument organization, and supplies. In terms of cellular biology, molecules move via active transport (against a concentration gradient using energy) or passive transport (simple movement in a solution).