Laser Light

Laser energy is measured by the wavelength of the light, which is the distance between two successive peaks of a wave. Laser wavelengths are often measured in nanometers (nm). One nanometer is equal to 10^–9 meter or one billionth of a meter.^1,2 Lasers used in surgery today that are longer wavelengths (700 nm to 1 mm) are found in the invisible infrared section of the electromagnetic spectrum, such as the CO₂ laser at 10,600 nm used to cut and coagulate soft tissue. Laser wavelengths can be in the visible area of the electromagnetic spectrum (400 to 700 nm), such as the green light used to coagulate superficial blood vessels or a pulsed-dye laser at 504 nm used to fragment urinary stones. Wavelengths that are very short are found in the ultraviolet section of the electromagnetic spectrum (100 to 400 nm), such as the excimer laser used to sculpt corneas during a LASIK procedure¹ (Fig. 47.1).

Laser light differs from ordinary light in three distinct ways that make it both unique and effective in the surgical setting.^1,2

1. 1. Laser light is monochromatic, which means one color or wavelength. This pure color can determine how the laser beam reacts with certain tissues. Ordinary light, in comparison, is polychromatic, which means that it comprises a multiple array of colors or wavelengths.
   
2. 2. Laser light is collimated. The light waves travel parallel to each other and do not diverge or spread. Collimation reduces the loss of power and allows for better focus and precision. Ordinary light spreads out in space as it travels away from its source.
   
3. 3. Laser light is coherent. All the waves travel in an orderly manner in the same phase and direction, and all the peaks and troughs of the waves are synchronized. This coherence gives the laser beam its power. Ordinary light, in comparison, is incoherent as its waves travel out in random directions.

Tissue Interaction

Four different interactions can occur when laser energy comes into contact with human tissue (Fig. 47.2). These interactions include reflection, scattering, transmission, and absorption.^1,2 The extent of this interaction is dependent on the wavelength of the laser, power settings, spot size, duration of exposure of the laser beam with the tissue, and the characteristics of the tissue. These interactions can have both positive and negative effects.^1,2

• • Reflection. Reflection occurs when the direction of the laser beam is changed after it comes into contact with a surface. This direction change can be intentional or accidental and thus can have both positive and negative effects. Mirrors can be used to intentionally reflect the laser beam to direct the beam to a hard-to-reach area. This action must be done carefully, however, to prevent an inadvertent strike and possible damage to a nontargeted area. Reflection can also occur if the laser beam hits an obstacle (e.g., a shiny metal surgical instrument) and then is inadvertently reflected to another area, thus causing a tissue burn. Reflection can be either specular (direct reflection) or diffuse (scattered reflection).
  
• • Scattering. The laser beam can also scatter as it enters certain tissues. This scattering causes the beam to disperse over a large area and weakens its strength. Backscattering can also occur as the beam scatters backward up the endoscope, thus causing damage to the operator’s eye, the endoscope optics, or the distal end of the scope.
  
• • Transmission. Transmission occurs when the laser beam passes or is transmitted through fluids or tissue with little or no thermal effect. Transmission depends on the wavelength of the laser beam and the tissue with which it comes in contact. For example, an argon laser beam can be transmitted through the clear structures and solutions of the eye to coagulate a bleeding vessel on the retina. This action occurs because the argon energy is not absorbed by clear structures and solutions; therefore, no thermal effect is noted in these tissues.
  
• • Absorption. Thermal effects and tissue response occur only when the tissue absorbs the energy of the laser. The amount of absorption and penetration depends on the beam’s wavelength and power, the characteristics of the contact tissue (color, consistency, and water content), the duration of the beam exposure, and the beam spot size. A thermal response can occur when tissue absorbs laser energy, thus heating the target cells. The degree of tissue response or thermal damage depends on the temperature to which the cells are heated. This temperature change is purposely regulated to effect the desired tissue response (Table 47.1).
  
  
  

  Table 47.1

  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

  Tissue Changes with Temperature Increases

  Temperature (° C)	Visual Change	Biologic Change
  37–60	No visual change	Warming, welding
  60–65	Blanching	Coagulation
  65–90	White/gray	Protein denaturization
  90–100	Puckering	Drying
  >  100	Smoke plume	Vaporization, carbonization

  
  

  From Ball KA. Lasers: The Perioperative Challenge. 4th ed. Laser Institute of America: Orlando; 2018. p. 13, Table 1.3.

Laser surgery can be categorized into three different types of tissue response, including thermal, mechanical, and chemical effects.^1,2 The thermal effect, as discussed previously, is the most common laser effect as tissue is vaporized, coagulated, ablated, cut, and welded depending upon the degree of thermal interaction. The mechanical (acoustical) effect from laser energy results when sound energy is created by the laser beam which disrupts tissue. The chemical effect is produced as the laser energy is used to activate a light-sensitive dye to disrupt and change tissue.

Types of Lasers

Lasers are classified by the four active mediums used to generate the laser energy: gas, solid-state crystal, liquid, and semiconductor diode.1 In a gas medium, electric energy is pumped through a gas, such as argon, to produce the laser energy. A solid-state crystal medium uses a special rod doped with an element that is activated with exposure to flash lamps to create the laser energy. Liquid mediums are organic dyes that produce a wide range of wavelengths when activated with another laser beam. Semiconductor diodes are used in the medical field and in consumer products and fiberoptic communication systems. Experimental mediums that are currently being explored include free electron lasers. The actual laser name is usually derived from the active medium substance that is used to generate the laser energy.^1,2 A summary of the various lasers currently in use can be found in Table 47.2.

Preoperative Care

For example, transmyocardial revascularization with the laser is generally limited to patients with advanced cardiovascular disease who have hemodynamically stable conditions and are not candidates for traditional bypass surgery. This innovative laser treatment may offer a method to revascularize the heart muscle for patients with intractable ischemic heart disease.^1,3 Dermatologic procedures may require skin preparation at home, preoperative administration of prophylactic antibiotics or antivirals, multiple treatments, and consistent postoperative skin care regimens that may last up to 1 month or more.¹ Preoperative care must include education concerning these issues and must be used to determine whether the patient will be able to comply with the treatment regimen.

The patient must also be prepared for expectations both during and after surgery. Many of these procedures are conducted without any anesthesia or with moderate sedation. The patient must be prepared for the sights, smells, and other sensations that will be experienced. Eye protection must be provided for the patient depending on the laser wavelength used. Odors can include the smell of tissue vaporization. The patient may also have burning or stinging types of painful sensations with certain procedures that can be minimized with appropriate preoperative preparation and relaxation medications.^1,4

Intraoperative Issues

Intraoperative issues with laser procedures primarily concern safety. Lasers are considered a class III medical device and, as such, are subject to U.S. Food and Drug Administration jurisdiction.^1,2 Many other regulatory, industry, and professional bodies also address the safe use of lasers. Regulations addressed include if registration of laser devices is needed, training requirements, laser safety officer responsibilities, and safety rules.

Lasers must be further classified by the manufacturer according to their potential to cause biologic harm and their inherent level of hazard. The classification system is based on the laser output power, wavelength, exposure duration, and emergent beam exposure.¹ The classification system ranges from I to IV; the higher the class, the greater the potential hazard. Most lasers used in surgery are classified as class IV and can damage eyes and skin and present a fire hazard.^1,2 Because of the many provider and patient risks associated with laser use, a laser safety program should be in place in any facility in which laser procedures are conducted. This includes freestanding ambulatory facilities and physician’s offices. A laser safety committee complete with a laser safety officer should be established and responsible for guiding and overseeing all laser use in the facility.¹ Issues that should be addressed include staff education, physician credentialing, and the monitoring of quality and safety issues. All staff involved in laser use must receive appropriate education before using or being involved in laser procedures.¹ Topics included in these special training classes include laser biophysics, laser equipment, laser-tissue interaction, safety procedures, and clinical applications.^1,5 Knowledge and skills should be verified through a competency-based credentialing program, and the skills should be reassessed and updated on a regular basis.^1,2,5 The three most important areas of safe laser use include eye protection, smoke evacuation, and fire safety.

The eyes are susceptible to damage from laser radiation. The damage may occur acutely or may go unnoticed and develop gradually over time. The type of damage also varies with the type of laser being used. Anyone who enters an operating room or treatment area where a laser is in use (including the patient) is at risk for eye damage and, therefore, should wear protective eyewear specific to the laser in use. Filtering devices should also be placed on operative microscopes and endoscopes. The patient’s eyes should be protected with either the appropriate eyewear or moist gauze pads.^1,2,5 The protective eyewear should have inscribed on the side of the frame the laser wavelength that the lenses are protecting against along with the optical density (i.e., the lenses’ filtering capabilities).^1,2,5

Another major safety concern with the use of laser technology is the control of the smoke that the laser energy produces as it impacts tissue. This surgical smoke is also called laser plume or surgical plume. Surgical smoke contains extremely small particles of vaporized tissues, toxins, and steam.¹ If inhaled, this particulate can end up in the alveoli of surgical team members or can coat the inside lumen of unprotected suction lines if used to evacuate smoke. Even short exposure to smoke particulate and odor from toxic gases may be related to nasal congestion, headaches, nausea, myalgia, rhinitis, conjunctivitis, and respiratory conditions and complications.^1,2,5,6 In Ball’s research, perioperative nurses were shown to have twice the incidence of targeted respiratory problems, probably because of the repeated inhalation of surgical smoke.⁶ In addition, there is a high chance that surgical smoke can transmit viable pathogenic material within the plume.^1,2,5,6

Patients are also exposed to hazards when surgical smoke is not evacuated appropriately. Ott’s classic study demonstrated that laparoscopic surgery patients can absorb the byproducts of laser-tissue interaction (surgical smoke), thus increasing the level of the patient’s methemoglobin and carboxyhemoglobin.⁷ This, in turn, will decrease the oxygen-carrying capabilities of the red blood cells. The patient absorbs the toxins produced within surgical smoke and then exhibits symptoms of headache, double vision, or nausea in the postanesthesia care unit (PACU).⁷ When surgical smoke is properly evacuated during laparoscopy, vision of the surgical site is maintained, smoke is not absorbed by the patient, and these untoward symptoms are not routinely present in the recovering patient.

A smoke evacuation system with an Ultralow Penetration air (ULPA) filter (to remove small particles) and charcoal filters (to absorb toxic gases) must be used whenever surgical smoke is generated.^1,5 The smoke collection device should be positioned as close to the laser-tissue impact site as possible. All persons in the room should also wear high-filtration masks to protect against any residual plume that may have escaped capture. Surgical masks are never to be the first line of defense to protect against plume inhalation. There are smoke evacuators available today that sense surgical smoke is being generated during laparoscopy and will automatically activate the system to gently evacuate the plume without destroying the pneumoperitoneum. There also are other different types of plume removal products that can be attached to the trocar sleeve to help clear the abdominal cavity of smoke without impacting the pneumoperitoneum. If any of these products require a suction line, then an in-line suction filter must be used so that plume particulate will not be drawn into the suction system. The in-line filter must be placed between the wall outlet and the suction canister to avoid pulling fluids through the filter, which would greatly alter its efficiency. Although smoke evacuation devices and supplies are available on the market today, compliance with smoke evacuation recommendations continues to be lacking.

Whenever a laser is in use, the risk of fire is also increased.^1,5 A fire can be triggered any time that a reflected laser beam or a direct beam comes in contact with a dry combustible item. The oxygen, anesthetic gases, and vapors from alcohol-based preparation solutions also contribute to the possible danger. All members of the laser team must be trained in fire safety and be able to respond quickly should a fire occur.^1,5 All combustibles near the laser-tissue impact site should be kept wet to prevent ignition. Use of flammable draping materials and skin preparation solutions should be avoided.^1,5 Sterile water or saline solution should be immediately available to douse any small fires that may occur.^1,5

Postoperative Care

Only one type of laser procedure requires special nursing care in the PACU. If the patient has undergone photodynamic therapy for selective destruction of a malignancy, the laser is used to activate a special light-sensitive dye that has been injected into the patient approximately 1 to 2 days before the procedure.1 The laser is introduced intraoperatively, which may be during a laparoscopic procedure, to activate the dye that, in turn, causes singlet oxygen to be formed, thus destroying a malignancy.¹ Because some of the light-sensitive dye may be retained for approximately 6 weeks in the skin cells (depending on the specific dye used), the patient cannot be exposed to bright lights or sunlight. Precautions to avoid this light exposure must be followed in the postanesthesia phase and especially if the patient is discharged.¹ Sometimes these procedures are performed later in the day so that the patient can be discharged during the evening hours when it becomes dark outside.

Preoperative Issues

Preoperative care for laparoscopic procedures should be focused on the adequate assessment and preparation of the patient. Routine diagnostics and assessments that are conducted for all general anesthesia or surgical patients should be completed. Special attention to determine the appropriateness of a laparoscopic procedure must be evident because laparoscopy, and the creation of a pneumoperitoneum, brings its own inherent risks and problems. A recommended preoperative checklist should include the following (adapted from AORN Guideline, 2020, p. 521)5:

• • History and physical examination (include age, weight, height, allergies, current medications, alternative therapies, drug use, alcohol/tobacco use)
  
• • Evaluation of medical problems
  
• • Baseline cardiac status (e.g., heart rate, blood pressure)
  
• • Thorough evaluation of respiratory system (e.g., rate, rhythm, blood oxygen level, presence of obstructive sleep apnea)
  
• • Baseline neurologic status and sensory impairment
  
• • Normalization of fluids and electrolytes (need for IV access)
  
• • Previous adverse experience with anesthesia or sedation agents
  
• • Antibiotics, if needed
  
• • Deep vein thrombosis prophylaxis
  
• • Genitourinary system evaluation
  
• • Appropriate laboratory and radiologic studies (test results, pregnancy test results, if appropriate)
  
• • Informed consent (explaining risks, benefits, alternatives)
  
• • Level of pain and/or anxiety
  
• • Arrangement for responsible adult caregiving to escort home if outpatient procedure

Numerous relative and absolute contraindications to laparoscopic procedures are well established and the patient should be evaluated closely regarding these issues. Previous abdominal surgery should be thoroughly evaluated and addressed because possible scarring or adhesions can affect the maneuverability of the laparoscope or limit the surgeon’s view of the surgical field. A comprehensive evaluation of the cardiovascular and pulmonary systems is mandated before any laparoscopic procedure because a pneumoperitoneum can greatly stress these systems. Patients with pulmonary or cardiac disease are at particular risk for developing respiratory acidosis, hypercarbia, peritoneal irritation, gas emboli, or cardiac arrhythmias from the presence and accumulation of CO₂ insufflation in the abdomen.⁵ Large abdominal wall hernias, diaphragmatic defects, and previous scars can affect trocar placement. Pregnancy was once considered an absolute contraindication to laparoscopic surgery; however, these procedures have now been shown to be safe and effective well into the second trimester. Obese patients should also be evaluated closely with specific attention to cardiac and pulmonary status.⁵

Intraoperative Issues

Pneumoperitoneum

The creation of a pneumoperitoneum involves the insufflation of the abdomen with a gas. The most commonly used gas for insufflation is CO₂ because of its relatively low risk of venous gas embolism (rapidly dissolves) and noncombustibility.5 Other gases that have been evaluated in clinical and experimental settings include nitrous oxide, helium, and argon, but CO₂ gas has been chosen as the preferred insufflation gas for laparoscopic procedures.⁵

A pneumoperitoneum is created during laparoscopic surgery to allow the surgical team to visualize the abdomen and perform the indicated procedure. Unfortunately, the creation and maintenance of this pneumoperitoneum can have varying effects on the patient and is associated with many of the complications generally associated with laparoscopic surgery. The patient’s position during surgery can exacerbate these adverse effects.⁵ For example, when the patient is placed in the Trendelenburg position, intra-abdominal pressure increases and respiratory problems can occur, including hypoxia.⁵ On the other hand, reverse Trendelenburg can cause decreased venous return, reduced cardiac output, and hypotension.⁵

The pneumoperitoneum is created when gas is insufflated into the abdominal cavity after the Veress needle is inserted through the abdominal wall. A mechanical insufflator with a pressure-limiting function is connected to the Veress needle with tubing to deliver the insufflation gas into the peritoneum. A hydrophobic filter is placed between the insufflator within the tubing to prevent contaminants from flowing from the insufflator into the abdominal cavity and also prevents cross-contamination.⁵ Normal insufflation pressures are maintained at 14 to 16 mm Hg² with maintaining an ideal pressure of less than 15 mm Hg.⁵ Insufficient pressure produces an inadequate pneumoperitoneum and impairs surgical visualization of the target site. Excessive pressure creates even greater cardiovascular and respiratory compromise than that commonly associated with the procedure.^2,5 Insufflation control panels should monitor and display the rate of flow of the insufflations gas, volume of gas delivered, and the intra-abdominal pressure.² High-flow insufflators that deliver 15 to 20 L/min are more effective than those delivering gas at slower rates.² When higher pressures are achieved in the abdomen, the insufflator must immediately stop the insufflation and release some of the gas if overpressurization is sensed.²

Cardiovascular changes

A wide variety of hemodynamic effects have been reported with the insufflation of a CO₂ pneumoperitoneum. The increased abdominal pressure compresses veins within the abdominal cavity and results in an initial increase in cardiac preload; however, true preload is ultimately decreased because of impaired venous return. Cardiac afterload is also increased as a result of the increased abdominal pressure and the resultant neurohumoral reflexes. The most common net effects from these changes include increases in heart rate, systemic vascular resistance, and central venous pressure. Cardiac output drops, and mean arterial pressure may increase, decrease, or remain unchanged, depending on the relative changes in cardiac output and systemic vascular resistance. Hemodynamic monitoring can be used to monitor for pressure changes and myocardial compromise in patients at extremely high risk. Pneumoperitoneum can cause dysrhythmias to include sinus tachycardia, bigeminy, and premature ventricular contractions. When pneumoperitoneum has been established, a resultant increase in the abdominal pressure causes vagal stimulation that can lead to severe bradycardia and possible asystole.2 As stated previously, automatic sensors are available within insufflators that provide continual monitoring and adjustment of the abdominal pressure so that cardiac problems are minimized.

Respiratory changes

The creation of a CO₂ pneumoperitoneum has several adverse effects on the respiratory system. Oxygenation may be impaired because of reductions in lung volume and the associated atelectasis that results from an elevated diaphragm. Ventilation may also be impaired and result in CO₂ retention and hypercarbia. Other untoward effects include reduced pulmonary compliance, increased airway resistance, and reduced vital capacity. All these effects are exacerbated by the commonly used Trendelenburg position.^2,5 These respiratory changes are also further aggravated by the following conditions: surgery that lasts more than 4 hours, a history of chronic obstructive pulmonary disease, age, obesity, and an American Society of Anesthesiologists physical status of III or greater.^3,12,13 A summary of cardiopulmonary effects can be found in Table 47.3.

Table 47.3

Cardiopulmonary Effects of a Pneumoperitoneum

	Elevated	Reduced
Respiratory	Respiratory rate	pH
	PaCO2, mixed venous CO2 tension, alveolar volume	Forced expiratory
	CO2 tension	Forced vital capacity
	Arterial-venous CO2 difference	Functional residual capacity
	Peak airway pressure	Total lung capacity
	Plateau airway pressure	Compliance
	Intrathoracic pressure
	Airway resistance
	Atelectasis
Cardiovascular	Heart rate with initial insufflation	Stroke volume
	Systemic blood pressure	Cardiac output
	Mean arterial pressure	Venous return unchanged or reduced
	Central venous pressure	Bradycardia with maintenance of pneumoperitoneum
	Pulmonary artery pressure
	Systemic vascular resistance
	Myocardial oxygen demand

Modified from Ball KA. Surgical modalities. In: Rothrock JC. Alexander’s care of the patient in surgery. 16th ed. Mosby: St. Louis; 2019; Cicek MC, Kaynak Y, Gunseren KO, Kaygisiz O, Vuruskan H. The effects of laparoscopic urologic surgery on cardiac functions: A pulse wave velocity study. Turk J Urol. 2020;46:303–308; Kassem M, Eman MM, El-Maksoud MAA. Low pressure versus standard pressure pneumoperitoneum in laparoscopic cholecystectomy. Egypt J Hosp Med. 2019;75:2499–2504.

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. Space Planning and Basic Equipment Systems
2. Evidence-Based Practice and Research
3. Care of the Gastrointestinal, Abdominal, and Anorectal Surgical Patient
4. Assessment and Management of the Airway

Stay updated, free articles. Join our Telegram channel

Join