Abstract
Lasers in surgery and medicine have evolved into a specialized area with increasing use and innovative techniques requiring anesthesia providers to be familiar with the historical, technical, and procedural aspects of laser applications.
Lasers applications in surgery include a variety of procedures with various laser types and specific anesthetic considerations.
Currently, anesthesia providers commonly encounter use of lasers in many procedures including airway surgery, cutaneous and cosmetic surgeries and various urologic procedures.
Outline
Lasers in surgery and medicine have evolved into a specialized area with increasing use and innovative techniques requiring anesthesia providers to be familiar with the historical, technical, and procedural aspects of laser applications. Lasers applications in surgery include a variety of procedures with various laser types and specific anesthetic considerations. Currently, anesthesia providers commonly encounter use of lasers in many procedures including airway surgery, cutaneous and cosmetic surgeries and various urologic procedures. Development of an anesthetic plan that is safe and satisfactory to the surgeon and patient necessitates knowledge of the procedure and patient characteristics. Use of lasers for procedures in pediatric patients include dental procedures, dermatologic and laryngeal surgery each having special anesthetic considerations. In obstetrics and gynecology, monitored anesthesia care is used for procedures using lasers ranging from laser conization to in utero coagulation of placental vascular anastomosis for twin-to-twin transfusion syndrome. With the use of lasers in the operating becoming more common in recent years, awareness and adherence against health hazards to both the patient and personnel is essential. Laser safety includes vigilance on the part of the anesthesia provider to prevent laser induced fires, avoid eye injury and burns, as well as, prevent electrical hazards. |
Introduction
Laser applications for surgery are widespread and include excisions of dermatologic lesions, treatment of laryngeal lesions, pediatric dentistry and treatment of prostatic hypertrophy. Procedures involving lasers and the airway represent a special challenge to the anesthesia provider including risk of airway fire, aspiration, injury, and inadequate ventilation and oxygenation. Use of laser in cosmetic and cutaneous procedures is generally well tolerated with monitored anesthesia care supplemented with topical or local anesthesia. Laser use in prosthetic reduction surgery is common and often patients are elderly presenting with multiple co-morbidities influencing choice of anesthetic technique. Anesthesia for procedures involving laser use in specialized patient populations such as pediatrics and obstetrics requires the anesthesia provider to be familiar with the procedure and special needs of the patient. As laser technology continues to evolve in the fields of medicine, surgery, and dentistry, benefits to the patient as it relates to anesthesia are apparent in some areas and require further study in others. Laser safety programs are required nationally in all hospitals and office based surgical facilities using lasers. |
History
The medical application vand uses of the laser have increased greatly over the past 40 years. Currently lasers are used for cauterization, tumor ablation, bloodless surgery and generally where destruction of a pathologic process within a small area is indicated. Cooperation between physicists, engineers and physicians has led to the application of lasers in medicine. It is a prime example of the value of clinical application of basic science discoveries.
The safe use of any new medical instrument such as the laser requires that personnel be aware of the background principles and hazards involved. Laser is a form of electromagnetic radiation and strict adherence to safeguards against health hazards is essential.
Laser
Laser is an acronym for Light Amplification of Stimulated Emission of Radiation. The precursor of laser was Maser, a term coined by Nobel laureate, CH Townes, Microwave Amplification by Stimulated Emission of Radiation. In 1958, work was extended from microwaves to the visible light spectrum and led to the construction of the first ruby laser by Bell Telephone Laboratories. The output of early lasers was not well controlled until the technique of “Q” switching permitted all the energy of radiation to be stored in the laser and then released in pulses. Use of lasers in space technology led to further developments that have been incorporated into operating room lasers. In essence, a laser beam which is defined by wavelength, duration, energy and width of spot focused optics to direct a beam to a biological target. This effort results in ionizing radiation in situ, mechanical shock waves and vaporization of tissues by heat. The beam acts both as a scalpel and to coagulate blood vessels.
Characteristics
Lasers can be generated from solids, liquids or gases with resultant radiation of different wavelengths and biomedical properties. The materiasl used to generate the laser defines depth of vaporization and damage to tissues Table 1. Recently, fiber based lasers and distal chip flexible endoscopy have been added to facilitate a new type of surgery, especially in office based laryngeal procedures.1
Atoms that can be excited to emit light waves are contained in the laser in long narrow tubes with mirrors at either end. External energy is provided initially to excite some of the atoms. The light wave emitted by these few atoms is amplified by stimulating other atoms to emit. A beam of wave is produced which develops tremendous energy by reflection from the mirrors. Finally, the radiation wave emerges from the partially reflective mirror as an intense directional beam of light. Laser beams are unique compared to other light wave beams because all other light or radiation is comprised of wave emissions from individual atoms independently of other excited atoms.
Laser characteristics include:
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A near single frequency of low band-width, i.e., an almost pure monochromatic beam.
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Precisely defined wave fronts. The point of impact can be the same as the wavelength.
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Enormous intensity and a high frequency of temporal and spatial coherence.
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A high plane of polarization and tremendous electromagnetic field strength.
Applications
Lasers have achieved many uses in medicine, mainly in surgery. They can be used to excise melanomas, tumors, dermatologic scars (tattoos, port wine stains) and also for cosmetic facial enhancement.2 As noted above, the new lasers are well suited for treatment of laryngeal epithelial diseases such as dysplasia and papillomatosis.1 Carbon dioxide lasers have been used successfully in the treatment of anogenital warts in children.3 In pediatric dentistry erbium lasers have been found effective for both dental and soft tissue treatments.4 Retinopathy of prematurity is amenable to diode laser therapy.5 Other applications have been in prostatic surgery and for complex eye surgery as in vitrectomy, retinal detachment and posterior capsulotomy.6 Perhaps one of the more innovative uses has been in the in utero coagulation of placental vascular anastomosis in the twin- to- twin transfusion syndrome.7 Other diagnostic uses include the application of laser spectroscopy to microanalytic techniques, Papanicolau smears and immunofluorescent techniques.
Because lasers are a source of coherent and monochromatic radiation that can be focused accurately with high intensity and essentially no blood loss, that are used in procedures that require precision. The laser accomplishes tissue excision by vaporization and at the same time seals small blood vessels. The use or the operating microscope ensures a bloodless operation with controlled depth of tissue removal. The carbon dioxide laser as an example emits an invisible wave of 10.6 μm which is absorbed within 0.2 cm of tissue surface.
Laser radiographs appear superior to conventional x rays and may be used in breast tumor imaging and occlusion of hemangiomas. An argon laser counter can determine a complete blood count and calculate derived parameters. A further use may be in caries prevention in dentistry.
Laser fiberoptics have been developed for operating room use. A further application is as an effective tool for mass communication in examination of patient records, test results and for teaching purposes. A helium- neon laser beam communication system has been used for central monitoring in an operating suite.
Laser Surgery Involving the Airway
Indications and Contraindications
Nd-YAG lasers may be used for debulking of tumors of the trachea, main-stem bronchi and upper airway by transmitting energy via fiberoptic cable through the suction port of a fiberoptic bronchoscope Procedures in and around the vocal cords and oropharynx may require the precision of the CO2 laser Patients with underlying cardiopulmonary disease may be unable to tolerate desaturation, hypoxemia, and hypercarbia associated with low concentrations of oxygen and interruptions in ventilation during laser surgery of the airway |
There are many types of lasers, each with specific indications. Neodymium-doped yttrium aluminum gradient (Nd-YAG) laser is the most powerful laser. It allows for a tissue penetration between 2 and 6 mm and is used for tissue debulking, particularly in the trachea, main-stem bronchi, and upper airway. The energy may be transmitted through a fiberoptic cable placed down the suction port of a fiberoptic bronchoscope. The Nd-YAG laser can be used in “contact mode” to treat a tumor mass, such as a papilloma (Fig. 1). Alternatively, the CO2 laser has very little tissue penetration and can be used where great precision is needed. One advantage of the CO2 laser in airway surgery is that the beam is absorbed by water, so minimal heat is dispersed to surrounding tissues. The CO2 laser is primarily used for procedures in the oropharynx and in and around the vocal cords. The helium-neon laser (He-Ne) produces an intense red light and can be used for aiming the CO2 and Nd-YAG lasers. It has a very low power and poses no danger to OR personnel or the patient.8
Because lasers are capable of igniting airway fires, use of high concentrations of oxygen and nitrous oxide is dangerous. Some patients with cardiopulmonary disease may not tolerate low concentrations of oxygen (at or just above room air) and the resultant desaturation and hypoxemia. In addition, interruptions in ventilation frequently result in hypercarbia and may result in arrhythmias. Prior to induction of anesthesia and surgery, a thorough history and physical help to identify patients who are at risk for complications during laser surgery of the airway and associated manipulations of oxygenation and ventilation.
Techniques
Patients with pathologic conditions involving the airway (i.e., mediastinal masses, tracheal stenosis) may be difficult to ventilate and/or intubate during induction of anesthesia Co-morbidities such as chronic obstructive pulmonary disease and coronary artery disease are present in many patients presenting for laser surgery of the airway and should be medically optimized pre-operatively Airway management for laser surgery of the larynx includes endotracheal intubation, intermittent apneic ventilation, and jet ventilation Short-acting opioids such as remifentanil or alfentanil in combination with a sedative-hypnotic (i.e., propofol) typically provide adequate depth of anesthesia for laser surgery of the airway and rapid emergence at the conclusion of surgery Post-operative pain control can generally be achieved with shorter acting opioids such as fentanyl and titrated to pain relief |
Pre-operative Management
Pre-operative management of patients requiring laser surgery for masses or tumors of the trachea, main-stem bronchi and upper airway involves careful attention to airway management. Airway compromise should be anticipated and a clear backup plan devised before the induction of general anesthesia. Patients with lesions in the mediastinum may be difficult to ventilate and/or intubate. Stridor suggests existing narrowing of the airway which may also compromise airway management. Inspiratory stridor indicates a supraglottic lesion, whereas, expiratory stridor suggests subglottic narrowing. Communication with the surgeon and careful planning are imperative during induction of anesthesia in this patient population. Furthermore, many patients presenting for laser surgery for lesions involving the airway are elderly and have a history of tobacco use. A history of chronic obstructive pulmonary disease suggests a need for a chest x-ray to rule out active pulmonary processes. Prior to induction, wheezing should be treated with bronchodilators. Coronary artery disease should be suspected in those at risk (age >65 years, male, family history, tobacco use, high cholesterol, hypertension, diabetes mellitus, obesity, and sedentary lifestyle.) Adrenergic response to airway manipulation should be anticipated and treated with beta blockade to decrease the risk of myocardial ischemia.9
Description of Technique
Laser surgery of the vocal cords requires the cords be immobile during laser firing. Adequate muscle relaxation is therefore important. The CO2 laser is generally used because of its ability to precisely vaporize tissue. The Nd:YAG laser coagulates deeper lesions and is used for tumor debulking.
Airway management for laser surgery of the larynx includes endotracheal intubation, intermittent apneic technique, and jet ventilation.
Endotracheal intubation with a small-diameter endotracheal tube (5.0–6.0 mm) or microlaryngeal tube allows for visualization of the larynx. The lowest possible FiO2 (less than or equal to 0.3 or 0.4) that assures adequate oxygenation is desirable. Nitrous oxide and a high FiO2 support combustion and should be avoided. Other precautions to prevent airway fires include filling the cuff with methylene blue normal saline and using a special laser endotracheal tube such as a Mallinkrodt Laser-Flex® or Xomed Laser Shield®. It should be noted that laser endotracheal tubes do not provide 100% protection for all laser types (Table 2).
Intermittent apnea technique allows tracheal extubation after a period of hyperventilation. The laser may be used during the time the patient is extubated for approximately 1–5 min prior to desaturation. A pulse oximeter must be accurate and always available. A disadvantage of this technique includes increased risk of airway edema and trauma.
Jet ventilation allows for ventilation without an endotracheal tube such as in treatment of some supraglottic and subglottic lesions. A ventilating laryngoscope is commonly used for supraglottic lesions. The jet flow should be aligned with the trachea and complete exhalation should be allowed prior to the next jet ventilation. By triggering the jet between laser firing, the vocal cords remain immobile. Complete muscle relaxation is essential with the use of jet ventilation. Complications include pneumothorax, barotrauma, and gastric distension.
Standard induction techniques may be used depending on the co-morbidities of the patient (i.e., rapid sequence intubation for those at risk for aspiration.) In general, minimal post-operative discomfort implies decreased need for narcotics intra-operatively. Short-acting opioids such as remifentanil (0.1–0.25 mcg/kg/min) or alfentanil (0.25–0.1 mcg/kg/min) may be used in combination with propofol (100–150 mcg/kg/min) to maintain adequate anesthetic depth while allowing for rapid emergence. As previously mentioned, adequate neuromuscular blockade is especially important in surgery involving the vocal cords.
In most cases, full recovery of airway reflexes should be obtained prior to extubation. In special circumstances, such as vocal cord surgery, the surgeon may request a smooth emergence involving deep extubation. In either case, gastric decompression prior to extubation is prudent, especially following the use of jet ventilation.
Post-operative Management
Use of short acting opioids such as intravenous fentanyl (25–50 mcg) as needed for pain control in the post-operative is usually adequate. Depending on the nature and invasiveness of the surgical procedure, longer acting narcotics such as morphine or dilaudid may be necessary to make the patient comfortable. There is risk of pneumothorax and barotrauma with jet ventilation. If suspected, a chest x-ray should be obtained.
Adverse Events
Factors contributing to the risk of airway fire during laser surgery include energy level of the laser, the gas environment of the airway, and the type of endotracheal tube A safe gas mixture of 25–30% oxygen and avoidance of nitrous oxide decreases the risk of airway fire during laser surgery Laser-resistant endotracheal tubes are designed to prevent fires associated with laser use The anesthesiologist and all members of the operating room team should remain vigilant in recognizing the early signs of airway fire (i.e., unexpected flash, flame, smoke, odors, discolorations of the breathing circuit) In the event of an airway fire, the endotracheal tube should be removed immediately and the flow of gases stopped followed by removal of burning materials and saline or water poured into the airway |
Side Effects/Complications
The most serious complication of laser airway surgery is fire. Airway fire may occur when an endotracheal tube is ignited. Several factors contribute to the likelihood of airway fire including the energy level of the laser, the gas environment of the airway, and the type of endotracheal tube. Oxygen and nitrous oxide both support combustion thus pose a fire hazard. If the patient is being ventilated with oxygen or nitrous oxide, the endotracheal tube emits a blow-torch type of flame that results in severe injury to the trachea, lungs, and surrounding tissue. Endotracheal tubes made of polyvinyl chloride, silicone, and red rubber have oxygen flammability indices of 26%. Wrapping the endotracheal tube with reflective tape still imposes a hazard in that kinking of the tube may occur, gaps may be present, and non-laser resistant tape may be inadvertently used.
Prevention and Treatment of Side Effects/Complications
The prevention of airway fires involving laser use begins with communication amongst the anesthesiologist, surgeon, and all members of the operating room team. Precautions should be taken to minimize the risk of an oxygen rich environment that would support ignition and combustion. To prevent fires associated with endotracheal tubes and laser use, laser-resistant endotracheal tubes have been developed. It is best to use an endotracheal tube that is designed to be resistant to a specific laser that may be used in surgery (e.g., CO2, Nd:YAG, Ar, Er:YAG, KTP). The tracheal cuff of the laser tube should be filled with saline and colored with an indicator dye such as methylene blue to alert the surgeon if he contacts the endotracheal tube. To minimize the risk of ignition, a safe gas mixture during laser surgery involving the airway is oxygen/air or oxygen/helium to achieve an oxygen concentration 25–30% or minimal oxygen concentration required to avoid hypoxia. Nitrous oxide should be avoided. Surgical drapes should be arranged to reduce the accumulation of oxidizers under the drapes. Gauze and sponges should be moistened prior to use near an ignition source.
The energy level of the laser is controlled by the surgeon and activation of the laser should be preceded by adequate notice. Safe use of laser in airway surgery includes intermittent and noncontinous mode at moderate power (10–15 W.) In addition, allowing time for heat dispersal and packing of adjacent tissues with moist gauze helps reduce the risk of airway fire.11 Precautions that should be taken to minimize the risk of airway fire include:
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Intubation with a laser resistant endotracheal tube resistant to the specific type of laser to be used
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Filling the endotracheal tube cuff with saline or an indicator dye such as methylene blue
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Requesting the surgeon to give adequate notice prior to activating the laser
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Reducing the concentration of oxygen to the minimum avoiding hypoxia
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Discontinuing use of nitrous oxide
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Waiting a few minutes after reducing the oxygen concentration before allowing laser activation
The anesthesiologist and members of the operating room team must be vigilant in recognizing the early warning signs of fire. Examples include unexpected flash, flame, smoke or heat, unusual sounds or odors, discoloration of the drapes or breathing circuit. If a fire occurs involving the airway, the anesthesiologist should immediately remove the endotracheal tube and stop the flow of all gases (Table 3). All flammable and burning materials should be removed from the airway and saline or water poured into the airway. Once the airway or breathing circuit is extinguished, mask ventilation should be established avoiding oxygen and nitrous oxide if possible. The removed endotracheal tube should be examined for fragments that might be left in the airway and bronchoscopy (rigid preferred) considered to assess injury and remove any debris. The patient’s status and plan for ongoing care such as admission to the intensive care unit, serial chest x-rays, arterial blood gases must be reassessed.11
Anesthesia for Cutaneous and Cosmetic Laser Surgery
Indications and Contraindications
Cosmetic laser surgery is frequently used to minimize the signs of aging in areas such as periorbital and perioral creases Laser skin resurfacing can successfully treat scars related to acne and trauma, as well as, pre-cancerous lesions |
Laser skin resurfacing is used to treat a variety of skin conditions including acne scars, traumatic scars, and pre-cancerous lesions such as actinic keratosis. Cosmetic laser surgery utilizes a controlled burn to the facial skin to reduce the signs of aging, especially in the periorbital and perioral creases where previous cosmetic techniques were lacking.
Many cosmetic procedures utilizing lasers are perfomed in an office-based setting under local or topical anesthesia sometimes with monitored anesthesia care. Therefore, patients with pre-existing medical conditions preventing safe administration of sedation and/or anesthesia should probably undergo elective procedures in a hospital setting rather than an office-based environment.12
Techniques
Topical and/or local anesthesia supplemented with intravenous sedation generally provides adequate anesthesia for facial laser resurfacing A lidocaine/tetracaine-based peel for minimal to moderately painful cutaneous laser procedures has been used successfully |
Pre-operative Management
Full face laser resurfacing is painful and can be stressful to the patient. Local anesthesia is often inadequate and must be supplemented with intravenous sedation, regional nerve blocks, topical anesthetics, and/or general anesthesia. Patients presenting with chronic medical problems such as hypertension, cardiovascular and/or pulmonary disease should be evaluated and treated for these problems prior to the procedure.
Description of Technique
Usually, CO2 or erbium:yag lasers are used for laser skin resurfacing (Fig. 2). Anesthetic technique should be chosen keeping in mind that a tremendous amount of heat is delivered to the skin surface resulting in a deep thermal injury and pain.12 General anesthesia, regional nerve blocks with local infiltration and/or intravenous sedation may be used. Combinations of the intravenous sedation (e.g., propofol, ketamine, midazolam, opioids) with topical anesthesia (e.g., EMLA cream- eutectic mixture of local anesthetics) have been successful for laser skin resurfacing in the ambulatory setting.14
A novel topical anesthetic compound using lidocaine/tetracaine-based peel has been used successfully for minimally to moderately painful cutaneous laser procedures. In a study of 20 patients undergoing full-face single-pass CO2 laser resurfacing, topical lidocaine/tetracaine-based cream was found to provide safe and effective dermal anesthesia. 15
Post-operative Management
Patients undergoing full face laser resurfacing receive potent narcotics in a short time and should have adequate recovery time prior to discharge. Oral analgesics are generally adequate for management of pain following the procedure. Post operative nausea and vomiting should be treated with anti-emetics (e.g., ondansetron).
Adverse Events
Laser-specific eyewear for the patient and operating room personnel are necessary to provide protection from ocular hazards during cosmetic laser surgery A smoke evacuation system is used to remove carbon particles, DNA, microils, and toxic fumes from the operating room environment |
Ocular hazards require laser-specific eyewear for the patient and operating room personnel. Protection from fire and reflectivity hazards include: fire-retardant draping, moist draping, water basin and fire extinguisher available. Alcohol containing solutions and plastic and rubber instruments should be avoided. Also, oxygen sources and metal or reflective materials should be avoided. Fire-resistant endotracheal tubes decrease the possibility of tube breach or ignition. Furthermore, release of carbon particles, DNA, microils, and toxic fumes accompany laser destruction of cells. Utilizing a smoke evacuation system 2 cm from the plume and wearing high-filtration masks protect the patient and medical personnel. 9
Anesthesia for Urologic Procedures Involving Laser Use
Indications and Contraindications
Laser techniques for resection of the prostate allow for minimal use of irrigating solutions compared to classic transurethral resection of the prostate (TURP) Transurethral resection of the prostate with the Holmium:yttrium-aluminum-garnet and potassium-titanyl-phosphate lasers are associated with almost no absorption of irrigant and minimal blood loss |
With an aging population comes an increasing incidence of bladder outlet obstruction and patients in need of prostatic reduction surgery. Advances in laser techniques for resection of the prostate have several proposed advantages over traditional transurethral resection. Classic transurethral resection of the prostate for patients with benign prostatic hypertrophy involves use of large amounts of irrigating solutions predisposing the patient to “TURP syndrome.” Subarachnoid block for classic transurethral resection of the prostate allows the anesthesiologist to monitor for mental status changes associated with electrolyte abnormalities due to absorption of large amounts of irrigating fluids. In an effort to reduce peri-operative morbidity, alternatives to conventional electorcautery have been explored. The Holmium:yttrium-aluminum-garnet and potassium-titanyl-phosphate lasers allow for transurethral resection of the prostate with almost no absorption of irrigant and minimal blood loss.16
Techniques
Patients undergoing TURP are often elderly with co-existing cardiovascular and pulmonary disease New laser technology using less irrigation fluid reduces the incidence of systemic complications associated with TURP syndrome KTP laser is used to treat BPH (benign prostatic hypertrophy) and allows for an almost bloodless procedure using less irrigation solution than conventional techniques |
Pre-operative Management
Most patients presenting for TURP have obstructive symptoms and are elderly. Co-morbidities increase risk of cardiovascular and pulmonary complications in the peri-operative period. Preexisting medical problems including coronary artery disease, peripheral vascular disease, cerebrovascular disease, chronic obstructive pulmonary disease, and renal impairment should be evaluated and treated in the preoperative period.9
Anesthetic Management
While general anesthesia makes it more difficult to recognize the early manifestations of TURP syndrome (e.g., altered mental status), anticoagulants and degenerative spinal changes may prevent or make difficult use of regional anesthesia.
Holmium laser technique decreases the amount of irrigation solution required and avoids the osmotic complications associated with absorption of large quantities of glycine, mannitol, and sorbitol. By decreasing the risk of TURP syndrome, the anesthesiologist may choose among several anesthetic techniques (e.g., general, neuroaxial, local and monitored anesthesia care) and tailor the anesthetic plan to an individual patient’s needs.
KTP laser is the most recent advancement in laser treatment of BPH.(Fig. 3) This technology allows for an almost bloodless procedure, fewer blood transfusions, and less absorption of the irrigant.16
Post-operative Management
Patients undergoing classic transurethral resection of the prostate under subarachnoid block may encounter urinary retention due to blockade of the parasympathetic fibers that control detrusor contraction and bladder neck relaxation. Delays in the recovery room and delays in discharge to home are some disadvantages of spinal anesthesia in the post-operative setting.9 Development of new laser technology using less irrigation fluid reduces the incidence of the TURP syndrome (Table 4). The systemic complications including fluid overload, hyponatremia, and hemolysis are reduced.
Adverse Events
Longer procedure times are associated with use of the Holmium and KTP lasers requiring longer durations of anesthesia As with most new technologies and procedures, KTP and Holmium lasers for prostate surgery are associated with learning curve and acquisition of skills by the surgeon |
Both the Holmium laser and KTP laser have longer procedure times requiring the patient to be anesthetized for a longer time period. Holmium laser prostate surgery is technically demanding and requires a longer learning curve. However, KTP laser procedure is less technically demanding and easier to learn.16
Anesthesia for Laser Use in Special Patient Populations
Pediatrics
Indications and Contraindications
Lasers are used for a wide variety of procedures in the pediatric population including removal of laryngeal papillomatosis and anogenital warts Erbium lasers are used for dental and soft tissue treatments Diode laser therapy is used in treatment of retinopathy of prematurity |
Lasers are frequently used in certain types of procedures and surgeries involving pediatric patients. Lasers have been successfully used for removal of anogenital warts, laryngeal papillomatosis, and excision of port wine stains. Diode laser therapy for retinopathy of prematurity and erbium lasers for dental and soft tissue treatments are other indications for laser use in the pediatric patient.
Techniques
Standard pre-operative fasting guidelines apply in the healthy pediatric patient for elective laser surgery Oral midazolam provides adequate pre-medication in patients older than 1 year prior to induction of anesthesia Pulsed dye laser treatment is commonly used to treat port wine stain (PWS) associated with Sturge Weber syndrome General anesthesia combined with local anesthetic filtration is commonly used for laser surgery in pediatric patients |
Addressing post-operative pain in the pediatric patient can be challenging and difficult to assess It is generally comforting to the child to have the parents at the bedside as he or she regains consciousness |
Pre-operative Management
Factors such as age, weight, and existing medical conditions deserve special consideration in formulating the anesthetic plan prior to surgery. Regarding pre-operative fasting, standard guidelines apply for pediatric patients presenting for elective laser surgery. Clear liquids may be given until 2 h before surgery. Breast milk should be stopped 4 h prior and formula 6 h prior to surgery. Solids should be discontinued 6 h before surgery. Recommendations vary somewhat and are for healthy pediatric patients without increased risk of aspiration or decreased gastric emptying.17
Pre-medication is generally not necessary for patients under 1 year of age. Beyond 1 year up to 10 years, oral midazolam 0.5 mg/kg to a maximum of 15 mg provides adequate anxiolysis. Intravenous doses of commonly used pediatric drugs such as atropine and midazolam are below in table Table 5.
Description of Technique
The anesthetic plan is determined by the procedure, the requirement to stay immobile, the age of the patient, any preexisting conditions and nay special needs of the patient. Anesthetic exposures are often multiple, especially in port wine stain treatments. Regarding cosmetic concerns related to the port wine stain (PWS) and/or the child with Sturge Weber syndrome, pulsed dye laser treatment is commonly used.18 There are no definitive numbers of treatments used in this therapy although 10–20 are commonly needed. Usually about 50–100 shots are tolerated at a time. The initial parameters for the vascular specific pulsed dye laser utilize a wavelength of 595 nm and pulse duration of 450 μs. This minimizes the spread of heat from the lesion and allows for selective destruction of capillary sized blood vessels. It is important to treat the PWS due to the negative psychosocial impact for affected children. Moreover, it is a simple procedure with minimal risk and a satisfactory cosmetic result.18 Treatment should be started as early as possible, even in small infants as the PWS grows with the child and hence will require more sessions for removal. Each laser flash has a relatively small spot size and thus larger lesions require more shots. Also, PWS seem to be more susceptible to fading when therapy is begun early. However, the treatment is painful and infants usually require at the least sedation and often general anesthesia. Older children may be managed after application of EMLA® cream. Refractory pediatric glaucoma may also complicate Sturge Weber syndrome (SWS) and Kirwan et al. have investigated the efficacy and complications of diode laser cyclophotocoagulation (cyclodiode.)19 Some appropriate pediatric dosages are listed in Table 5.
Many surgeons prefer to work with small patients under general anesthesia, while others prefer conscious sedation when possible. General anesthetic techniques provide many advantages such as immobility, and variables such as PaCO2, blood pressure, and intracranial pressure are more easily controlled to optimize operative conditions. Combined techniques utilizing general anesthesia with local anesthetic infiltration are commonly employed. Remifentanil and fentanyl have commonly been used during conscious sedation. They may be administered by bolus or infusion techniques. Propofol infusion is also appropriate. Several anesthetic challenges exist in the patient with SWS. A prone position is often required to treat PWS of the leg. Intubation may prove difficult due to angiomas of the mouth and upper airway.20 Placement of a supraglottic airway may be beneficial. Initial sedation with oral midazolam may be indicated, followed by EMLA® cream applied to the PWS and secured with plastic tape. A propofol infusion would then allow 30 min of flash lamp pulsed dye laser therapy, prompt awakening and discharge to home with oral acetaminophen.
Post-operative Management
Pain assessment in the pediatric patient can sometimes be challenging due to their inability to communicate effectively with the care giver. Irritability and crying may be attributed to other causes other than pain. Therefore, given the invasiveness and extent of the surgery one must rely on clinical judgment on administration of pain medications. As the pediatric patient regains consciousness, it is generally helpful to have the parents at the bedside. Common pediatric post-operative analgesics and antiemetics are found in Table 6.
Adverse Events
Complications during laser surrey are mainly related to underlying conditions of the patient Laryngospasm in pediatric patients should be anticipated on induction and emergence of anesthesia Airway edema as a result of airway surgery may pre-empted by administration of dexamethasone |
As with any anesthetic, complications may occur. During laser surgery, problems are related mainly to the underlying condition. Procedures are usually short, especially dermatologic conditions. However, cardiac arrest has been described during nasal sinus surgery using the Nd YAG laser, most likely due to venous air embolism, which has also occurred during other, similar procedures.21 The authors recommend that monitoring for this complication should be in place, even for short procedures. In another case involving a 15 month old child, unobserved laser damage during pediatric endoscopy resulted in bilateral tension pneumothorax and pneumoperitoneum which caused rapid severe decompensation.22 The baby was successfully resuscitated after placement of bilateral chest tubes and a peritoneal tube.
Laryngospasm is common in pediatric patients during induction and emergence from general anesthesia. Manipulation of the airway during laser surgery for papillomatosis requires adequate depth of anesthesia and muscle relaxation to minimize the incidence of laryngospasm and hypoxemia during surgery. Prior to extubation, pharyngeal suctioning and an awake, spontaneously breathing patient moving all extremities helps to avoid laryngospasm. Also, some advocate deep extubation in the spontaneously breathing patient prior to the return of airway reflexes. If larygnospasm occurs, treatment includes continuous positive pressure ventilation with 100% oxygen. Failure to resolve and resultant hypoxia should be treated with succinylcholine 0.1–0.5 mg/kg IV followed by positive pressure ventilation and possible re-intubation. Bradycardia associated with succinylcholine administration can be avoided by administering atropine 0.01–0.02 mg/kg IV prior to succinylcholine administration.
Airway edema resulting from surgery may be preempted by administering dexamethasone 0.25–0.5 mg/kg IV. Post intubation croup may be treated with inhaled nebulized racemic epinephrine 0.25–0.5 ml of 2.25% solution in 2.5 ml of normal saline.
Obstetrics and Gynecology
Indications and Contraindications
Conization of the cervix and diagnoses of Papanicolau smears are applications of lasers in gynecology In utero coagulation of placental vascular anastomosis in twin-to-twin transfusion syndrome is a novel technique for laser use |
In gynecology, laser applications include diagnostic spectroscopy for Papanicolau smears and conization of the cervix for cervical dysplasia.
In obstetrics, an innovative use of laser has been developed for in utero coagulation of placental vascular anastomosis in the twin-to-twin transfusion syndrome.
Techniques
In general, patients presenting for gynecological procedures involving laser use are young and health Pregnant women beyond 18 weeks gestation presenting for laser surgery are at increased risk for aspiration Local anesthesia with monitored anesthesia care is usually sufficient for laser conization of the cervix Compared to general anesthesia or total intravenous anesthesia, conscious sedation with local anesthesia results in less hemodynamic fluctuations and intraamniotic bleeding during fetoscopic laser surgery Oral analgesics such as acetaminophen or ketorolac are usually adequate for post-operative pain relief in minor gynecologic surgeries Post–operative nausea and vomiting may be treated with anti-emetics such as ondansetron and metoclopramide |
Pre-operative Management
Patients presenting for gynecologic procedures such as Papanicolau smears and conization of the cervix are generally young and healthy. History and physical guides the need for anything other than routine lab tests. In the pregnant woman presenting for any surgery, effects of anesthetic agents on the fetus especially in the first trimester should be considered, although no particular anesthetic technique or agent has proven to be teratogenic in humans. If greater than 18 weeks gestation, precautions to decrease the risk of aspiration are indicated.9
Description of Technique
Gynecological procedures such as laser conization of the cervix for cervical dysplasia may be performed under local anesthesia with monitored anesthesia care. Generally, there is less blood loss, but a longer operative time compared to using a scapel.9
Some controversy has arisen as to the preferred method of maternal anesthesia during fetoscopic laser coagulation (Fig. 4). Morimoto et al. determined that maternal respiratory status remained stable with careful titration of midazolam and fentanyl.24 Only one patient in their study required general anesthesia. Rossi et al., studying a larger group (266 vs 22), found that maternal-fetal hemodynamic fluctuations and intraamniotic bleeding were far greater when general or total intravenous anesthesia was used.25 They concluded that a technique of local anesthesia with some conscious sedation was preferable.
Post-operative Management
Laser conization of the cervix under local anesthesia results in minimal discomfort for most women post-operatively. Oral analgesics such as acetaminophen or ketorolac are acceptable choices. Post operative nausea and vomiting can be treated with anti-emetics such as raglan or zofran. Monitoring for post operative bleeding is appropriate.
In the parturient following fetoscopic laser coagulation, management in the post-operative period involves monitoring mother for bleeding and pre-term labor. Tocolytic agents may be needed after consultation with an obstetrician.9
Adverse Events
Peroneal nerve injury is a complication of the lithotomy position manifested by foot drop and loss of sensation over the dorsum of the foot Monitoring for pre-term labor and bleeding in the parturient post-operatively is imperative and may involve consultation of an obstetrician |
A complication following gynecological and obstetrical procedures involving laser is peroneal nerve injury secondary to the lithotomy position manifested by foot drop and loss of sensation over the dorsum of the foot. Vigilance during positioning and during the surgery is the best ways to prevent this injury. Post operative nausea and vomiting should be anticipated and prophylaxis given prior to emergence in those at risk.9 Bleeding and premature labor are risks of surgery in the parturient, particularly involving in utero procedures. Involvement of the obstetrician in the peri-operative care of these patients is important.
Future Directions of Laser Applications and Anesthesia
Further clinical research in the field of laser applications will have implications on anesthesia as laser technology evolves. For example, it is believed that pulsed angiolysis lasers are a platform technology for future innovations in management of not only laryngeal disease, but other areas in which superficial mucosa is diseased (i.e., Barrett’s esophagus and granulation in the nose and ear.)26 Furthermore, where there has already been advancements in laser technology such as in prostate surgery, the benefits of broadening anesthetic options still requires documentation and further study Yet another area of innovation is in the field of dentistry. Lasers are currently used for contouring the gums, treating mouth ulcers, and setting bonding materials. Although use of lasers in dentistry is not without a need for anesthesia, research continues to determine the effectiveness and safety of laser use in hard-tissue such as cavity removal.
Special Considerations
Safety Concerns Involving Use of Lasers in the Or
Laser Safety Program
Development of a laser safety program is a national requirement for all hospitals and for office based surgical facilities using lasers. The laser can ignite any combustible material and thus is a fire hazard. Any tissue that the laser focuses is vaporized, whether diseased or healthy. Also, contact with the laser, like all radiation, should be avoided. There is no known acceptable of safe dose. There may be biological effects from scattered or reflected radiation. The long term effects on the genetic system are unknown as are the effects during pregnancy.
Issues critical to safety include:
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1.
Area control is essential. Lasers should be in isolated low traffic areas, locked in cabinets and used only by authorized and trained personnel.
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2.
Adequate ventilation and scavenging systems should be able to remove all by-products as the dangers of inhalation or dissemination of viral, bacterial or tumor tissue has not been determined.
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3.
A good suction system should be available to remove smoke and vaporized tissue which might disseminate particles that might be inhaled by operating room personnel or the patient.
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4.
Surfaces in the room should be minimally reflective.
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5.
Warning signs and light alarms should be posted at entrances.
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6.
A laser safety officer should head up the safety program, which should include plans for emergency treatment of laser radiation and education programs.
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7.
Eye protection is essential. The lens of the eye can focus the laser beam and cause retinal burns. Eye safety is afforded by goggles with high optical density and specificity for the laser wavelength in use. The goggles must fit the forehead and enclose the globe. Although the carbon dioxide beam is invisible, a tracer light is incorporated to allow the surgeon to select the target area. The axis of the visible tracer and laser beam should be aligned prior to use.
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8.
Skin exposure may cause acute or chronic burns. Protection is afforded by using sterile gloves.
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9.
Other areas should be draped with cloth as laser beams undergo scattering and can be reflected. Hair, scrubbing solutions, and some anesthetic agents may be fire hazards (N2O,O2 support combustion).
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10.
Electrical hazards exist as the initial excitation of the atoms requires high energy currents and circuits which add to the existing hazards of electrical apparatus in the operating room.
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11.
An understanding of laser measure and knowledge is necessary for controlled use. Energy density is defined by the total energy (joules) and spot size (cm2) but this may not adequately account for the pulse duration of the beam or the degree of biologic effect.
Patient Protection
Laser hazards to the patient arise from damage to normal tissue or from fires. The eyes should be covered with wet gauze. If a misdirected or reflected beam strikes unprotected tissue, it too is vaporized. Currently available endotracheal tubes are not flammable. Cuffs should be inflated with saline. Oil based lubricants should be avoided.
Danger to OR Personnel from Laser Use
The misuse or misfiring of a laser may cause damage to other personnel in the operating room. Eye damage is of particular concern. The site of ocular damage for any given laser depends upon its output wavelength. Laser light in the visible and near infrared spectrum from 400 to 1,400 nm constitutes the so-called “ retinal hazard region ” and can cause damage to the retina, while wavelengths outside this region (i.e., ultraviolet and far infrared spectrum) are absorbed by the anterior segment of the eye causing damage to the cornea and to the lens. The extent of ocular damage is determined by the laser irradiance, exposure duration, and size of the beam. As laser retinal burns may be painless and the damaging beam sometimes invisible, maximal care should be taken to provide protection for all persons in the laser suite including the patient, laser operator, operative assistants, anesthesiology personnel and observers.
Specific hazards may involve certain laser types:
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Exposure to the invisible carbon dioxide laser beam (10,600 nm) can be detected by a burning pain at the site of exposure on the cornea or sclera.
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Exposure to a visible laser beam can be detected by a bright color flash of the emitted wavelength and an after-image of its complementary color (e.g., a green 532 nm laser light would produce a green flash followed by a red after-image).
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When the retina is affected, there may be difficulty in detecting blue or green colors secondary to cone damage, and pigmentation of the retina may be detected.
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Exposure to the Q-switched Nd:YAG laser beam (1,064 nm) is especially hazardous and may initially go undetected because the beam is invisible and the retina lacks pain sensory nerves. Visual disorientation due to retinal damage may not be apparent to the operator until considerable thermal damage has occurred.
Protective Eyewear
Protective eyewear in the form of goggle, glasses, and shields provides the principal means to ensure against ocular injury, and must be worn at all times during laser operation (Fig. 5). Laser safety eyewear (LSE) is designed to reduce the amount of incident light of specific wavelength(s) to safe levels, while transmitting sufficient light for good vision. In accordance with the ANSI Z136.3 (1988) guidelines, each laser requires a specific type of protective eyewear, and factors that must be considered when selecting LSE include: laser wavelength and peak irradiance, optical density (OD), visual transmittance, field of view, effects on color vision, absence of irreversible bleaching of the filter, comfort, and impact resistance. Failure to address these factors may result in serious eye injury. As LSE often look alike in style and color, it is important to specifically check both the http://www.dermweb.com/laser/eyesafety_colour_code.htmlwavelength and OD imprinted on all LSE prior to laser use, especially in multi-wavelength facilities where more than one laser may be located in the same room (e.g., where urology and gynecology share the same operating room).
The integrity of LSE must be inspected on a regular basis (e.g., annually) since small cracks or loose fitting filters may transmit laser light directly to the eye. With the enormous expansion of laser use in medicine, industry and research, every facility should formulate and adhere to specific safety policies that appropriately address eye protection.
Clinical Considerations of Low Light Situations and Safety Glasses
It is also important to determine the impact of wearing LSE on the ability of the anesthesiologist to read the monitoring waveforms as well as the dials on the anesthesia in low light situations (i.e., darken rooms) before embarking on a case. The choice of waveform color can be changed in new monitors and thought needs to be given this to avoid a critical loss of vital monitoring data (Figs. 6–7).
Conclusion
With advancements in the field of laser technology, applications of lasers in medicine and surgery have become widespread and common place. Innovations in clinical uses of laser in many fields such as otolaryngology, plastic and dermatologic surgery and urologic surgery have demanded a familiarity with laser technology and safety by the anesthesiologist. In some cases, previously invasive surgeries with major blood loss have now become meticulous and practically bloodless procedures. In other cases, surgeries that in the past required general anesthesia or total intravenous anesthesia are currently performed under monitored anesthesia care with local anesthesia.
Patient populations under going laser surgery range from the fetus in utero to the elderly. Therefore, the anesthesiologist must be cognizant of many variables such as age, underlying medical conditions, and potential complications that may arise in the peri-operative period for all procedures or surgeries involving laser use.
Future directions in laser applications in anesthesia continue to evolve as different areas of medicine and surgery take advantage of innovations in laser technology. Realizing the benefits to the patient of increasing use of lasers in surgery and adaptations in the anesthetic plan deserves further study.
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Gayle, J.A., Frost, E.A.M., Gevirtz, C., Churi, S.B., Kaye, A.D. (2011). Laser/Light Applications in Anesthesiology. In: Nouri, K. (eds) Lasers in Dermatology and Medicine. Springer, London. https://doi.org/10.1007/978-0-85729-281-0_47
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