By D. Bram. New England Conservatory of Music. 2019.
In 1969 buy xenical 60mg amex, prior to the routine use of scavenging devices discount xenical 60mg, Linde and Bruce observed an average concentration of halothane of2 10 ppm and nitrous oxide of 130 ppm in the air surrounding an active anesthesia machine purchase 60 mg xenical amex, with end-expired air samples from anesthesiologists as high as 12 ppm of halothane. Subsequent studies have reported even higher concentrations in poorly ventilated and/or unscavenged locations. It is not surprising that chemicals with such widespread and profound physiologic effects as anesthetic agents would evidence toxic properties if applied in adequate concentrations to tissues. For example, there is ample evidence that cellular damage can be caused by chronic exposure of cultured cells and experimental animals to high concentrations of many anesthetic gases. Some limitations of the clinical studies include occupational exposure in the study population to other risk factors such as radiation, long work hours, stress, and unhealthy personal habits, as well as potential reporter bias that can occur in retrospective studies. The reports on possible genotoxic effects of trace anesthetic exposure are conflicting. The increased relative risk for congenital abnormalities was of borderline statistical significance for exposed physicians only. The review also pointed out that duration and levels of anesthetic exposure were not measured in any of the studies and that other confounding factors were not adequately controlled. The importance of adequate scavenging was highlighted in a subsequent meta-analysis of the risk of spontaneous abortion among hospital workers, dental assistants, veterinarians, and veterinary assistants. Reports of elevated risks for adverse reproductive outcomes have continued to appear. Female dental assistants and female veterinarians who work in large animal21 hospitals have been specifically identified as at-risk for adverse reproductive22 outcomes. It is likely that other job-associated conditions besides exposure to trace anesthetic gases, such as stress, infections, long work hours, shift work, and radiation exposure, may account for many of the adverse reproductive outcomes. A survey of 3,985 Swedish midwives demonstrated that night work was significantly associated with spontaneous abortions after the 12th week of pregnancy (odds ratio 3. Preterm birth in obstetric and neonatal nurses was23 associated with increased work hours, hours worked while standing, and occupational fatigue. This risk is minimized when appropriate waste gas scavenging technology is applied. Temporary lethargy and fatigue are the most common symptoms described after brief exposures to subanesthetic concentrations of anesthetic gases. Longer exposures and higher concentrations have been associated with symptoms such as headache, depression, anxiety, loss of appetite, loss of memory, decreased reaction time, and decrements in cognitive function. Most of the measurable psychomotor and cognitive impairments produced by brief exposures are short-lived and disappear within 5 minutes of cessation of exposure. Among anesthetic gases, nitrous oxide is the greatest contributor to this effect because of the relatively large volumes that are used, the longer time period that it has been in use compared to other inhalation anesthetics, and the fact that nitrous oxide from a number of nonmedical sources is currently the dominant ozone-depleting gas. Nitrous28 oxide from anesthetic use represents only a small fraction of that found in the stratosphere but nevertheless does contribute to the greenhouse effect. Known cardiovascular complications of methyl methacrylate in surgical patients include hypotension, bradycardia, and cardiac arrest. Reported risks from repeated occupational exposure to methyl methacrylate include skin irritation and burns, systemic allergic reactions, eye irritation, headache, neurologic signs, adverse reproductive outcomes, and organ damage. In one report, a dental technician suffered significant lower limb neuropathy after repeated occupational exposure to methyl methacrylate. Allergic Reactions Allergic reactions to volatile anesthetic agents and to some muscle relaxants have been associated with contact dermatitis, hepatitis, and anaphylaxis in individual anesthesiologists. The pathophysiology appears more complex than antibody33 development and may be more of a halogenated hydrocarbon autoimmune reaction injuring the liver. These autoantibodies are also detectable in about one-third of patients with advanced alcoholic liver disease and chronic hepatitis C. Despite the presence of these autoantibodies, only 1 of 10534 anesthesiologists had findings of any hepatic injury. Therefore, although autoantibodies may occur in anesthesiologists frequently exposed to volatile anesthetics, they do not appear to commonly cause anesthetic-induced hepatitis. In many cases, medical personnel who are allergic to latex experience their first adverse reactions while they are patients undergoing surgery. Although the majority of symptoms are mild, urticaria, bronchospasm, and rhinitis can occur. More severe symptoms are significantly related to a positive history of individual or family atopy. The prevalence of latex sensitivity among medical personnel can be as great as 16% to 20%. The protein content is responsible for most of the generalized allergic reactions to latex-containing surgical gloves. These reactions are exacerbated by the presence of powder that enhances aerosolization. Irritant or contact dermatitis accounts for the majority of reactions resulting from wearing latex-containing gloves (Table 3-2). Anesthesiologists who believe that they are allergic to latex must avoid all direct contact with latex-containing products. It is also important that coworkers wear nonlatex or powderless, low latex-allergen gloves to limit the levels of ambient allergens. The biologic consequences of radiation exposure vary depending on age, gender, and the specific organ that is exposed. The development of cancer is an example of a radiation-induced injury with a long latency period and having no known threshold below which the risk entirely disappears. The annual38 limit is 5 rem with an allowable long-term limit of (N − 18) × 5 rem, where N is the age in years. The recommended maximum occupational exposure to a pregnant or lactating worker should not exceed a monthly limit of 0. Preventative42 226 strategies for anesthesiologists to minimize their risk of radiation-induced injury include limiting the intensity and exposure time, distancing oneself from the source of the radiation, and using maximal shielding from both primary and scattered sources of radiation. Transient43 symptoms such as vertigo, nausea, dizziness, and visual phosphenes (light flashes) have all been reported. The severity of these symptoms is a function of the field strength of the scanner, the proximity to the scanner, and the rate of movement within the magnetic field. There are currently no published regulations in the United States that limit occupational exposure. Guidelines from the International Commission on Non-Ionizing Radiation Protection offer some suggestions regarding technique and worker practices to limit neurobehavioral effects. No studies to date have identified any chronic44 adverse health effects from long-term exposure to high-intensity magnetic fields. However, until more information is available, it would seem prudent to conform to the general admonition regarding all forms of radiation exposure: keep it as low as reasonably achievable. Noise Pollution The magnitude of noise is determined by both the intensity of the sound (measured in decibels) and the duration of the exposure to that sound. A commonly accepted standard for the maximum level of safe noise exposure is 90 dB for 8 hours. Each increase in noise of 5 dB halves the permissible45 exposure time, so that 100 dB is acceptable for just 2 hours per day. Ambient noise levels as great as 90 dB commonly result from high capacity heating and air conditioning systems, ventilators, suction equipment, forced-air patient warming devices, music, and conversations.
The deposits are stained bright red globulinemic glomerulonephritis purchase xenical 120 mg otc, referred to as hyaline thrombi buy xenical 60 mg overnight delivery. In addition order xenical 60mg with mastercard, numerous large conﬂuent subendothelial deposits, known as wire-loop lesions are present Fig. In addition, global, shows widespread subendothelial wire-loop deposits, which there are diffuse subepithelial spikes, typical of membranous lupus, stain light brown on silver staining. Jones methenamine silver stain membrane duplication producing a membranoproliferative pattern of injury. This case shows numerous subendothelial and mesangial depos- extraglomerular immune deposits. In this example, there are numerous its with well-developed basement membrane duplication. There also glomerular capillary loop deposits, wire loops by light microscopy, and are scattered subepithelial deposits with basement membrane response extraglomerular deposits involving tubular basement membranes and in the form of spikes. This image shows a large subendothelial wire-loop deposit (arrow) and numerous mesangial deposits (bottom). Some basement membrane duplication is present, and the podocyte foot processes are largely effaced 230 6 Glomerular Diseases 6. The diagnosis is predicated glomerulonephritis with a full-house immunoﬂuorescence. In the more severe form of C1q nephropa- thy seen here, there is segmental sclerosis with hyalinosis. In this example of C1q nephropathy with indicates a great risk of progressive disease. Jones methenamine stain minimal change–like features, there is no histologic abnormality. Electron microscopy showed mesangial electron-dense deposits and diffuse podocyte foot process effacement. The deﬁning feature of C1q nephropathy on biopsy is the presence of prominent C1q staining. Electron microscopy showed mesangial electron-dense deposits and diffuse podocyte foot process effacement. Patients often present with rapidly progressive renal failure, but may have a more indo- lent and insidious disease if the crescentic process is less ful- minant. There are a variety of causes that are most easily resolved by a combination of immunoﬂuorescence ﬁndings, clinical history, and serologic data. This electron micrograph from the case – Diverse types of primary and secondary immune com- shown in Fig. One patient was an 18-year-old man who died with hemoptysis and acute renal failure. The eponym Goodpasture’s syndrome , was coined by Stanton and Tange in 1958 for the clinical presen- tation of renal failure and alveolar hemorrhage. They usually have preexisting pulmonary injury, most com- monly as the result of smoking. The histologic ﬁnding typically is a diffuse necrotizing process with exuberant crescent formation. This combination should Major speci ﬁ city: myeloperoxidase prompt consideration of the co-existence of two diseases. This glomerulus shows the initial lesion that leads to crescent formation, segmental necrosis. Note the large mass of ﬁbrin in Bowman’s space, which is the result of capil- Fig. Surrounding the ﬁbrin mass are a few epithelial ence of an extraglomerular cellular reaction following capillary loop cells, whose numbers will increase rapidly, forming a cellular crescent disruption. It is collapsed, and its structure is difﬁcult to assess by hematoxylin and eosin stain 6. Crescents form after disruption or strated readily in the active stage of necrotizing injury and crescent for- necrosis of the capillary loop basement membrane, a ﬁnding identiﬁed mation with direct immunoﬂuorescence for ﬁbrinogen. Fibrin is beginning to spill into Bowman’s space, centic process but does not allow identiﬁcation of the underlying dis- and a cellular reaction (crescent) has just begun to form. In the early crescentic lesions, ﬁbrin may be abundant and nicely demonstrated with trichrome Fig. Over time, the ﬁbrin breaks down and becomes inconspicuous as and has a stringy appearance on electron microscopy. The ﬁbrin is enveloped by cells of the through a ﬁbrocellular, then a ﬁbrous, stage as the cellularity diminishes cellular crescent and matrix dominates the lesion. Note that only a remnant of the glomerular tuft is present; most of ease is a possibility. Bowman’s space is ﬁlled with red cells and ﬁbrin Bowman’s space representing the initial phase of organization of the with an early cellular response. Complement may be linear or interrupted in its stain- have one or more multinucleated giant cells of histiocytic lineage. Immuno ﬂ uorescence for IgG glomerulus contains one multinucleated giant cell in the center. Although giant cells may be seen in granulomatosis with polyangiitis, they are very rare in that context as well as in other glomerular diseases with crescent formation 6. Patients with together in a category of renal disease known as the “colla- Alport’s syndrome initially present with hematuria but pro- gen nephropathies. Only the typical ultra- structural ﬁndings of these entities are shown in the follow- ing illustrations. Electron microscopy in Alport’s syn- drome shows variable segments of glomerular capillary loop basement membrane thinning and thickening. Rariﬁed foci with tiny electron-dense granulations also may be observed, but often representing an X-linked disorder caused by mutations these are not present in this image 236 6 Glomerular Diseases 6. Often which patients have hypoplastic or absent patella, bony there is a family history of hematuria. Thin basement mem- abnormalities of elbows, dystrophic ﬁngernails and toenails, brane nephropathy is a benign nonprogressive disorder in the and iliac horns. Approximately 50 % of patients develop pro- vast majority of patients; however, rare progressive cases teinuria, although progression to renal failure affects less have been reported. To qualify for a diagnosis of thin base- logic features are nonspeciﬁc, with glomerulosclerosis and ment membrane nephropathy, patients must have hematuria secondary tubulointerstitial scarring. Tannic acid or phosphotungstic acid staining enhances the visibility of the collagen ﬁbers and their banded periodicity. Electron microscopy in nail-patella syndrome shows lucent foci in the capillary loop basement membrane Fig. Within these foci are collagen copy in thin basement membrane nephropathy simply shows general- ﬁ bers (arrow). Generally, there is preservation of the podocyte foot pro- of their foot processes cess because patients do not have signiﬁcant proteinuria. The banded collagen ﬁbers (arrow) are revealed most readily when sections are stained with phosphotung- stic acid, as in this example.
Modifed from Adler  A summary of the susceptibility loci identifed thus far and their chromosomal locations is presented in Fig xenical 60mg with amex. A potential linkage at the 7q36 locus was also demonstrated in the Australian/New Zealand and Icelandic population linkage analyses [55 cheap 120mg xenical fast delivery, 67] buy 120mg xenical otc. The lack of replication between these early studies as explained by Harrison et al. A subsequent reanalysis of the original Australian/New Zealand scan, using an alternative variance component-based linkage approach, showed novel susceptibility loci on chromo- somes 5q and 13q . The Finnish group also dem- onstrated signifcant linkage with the 9p13 locus . An additional case-control analysis in the Finnish population demonstrated a nominal association at the 2p13 locus . A meta-analysis of these multiple population genome scans confrmed linkage with seven of the loci and revealed an additional six novel loci . These studies show further associations with the 2q14 locus in an Australian/New Zealand cohort  and the 19q31. Hence, to test for imprinting effects, the Dutch group examined gene expression in androgenetic placentas, where all genes are derived solely from the father. Another issue is that populations will have different genetic back- grounds and likely have a diverse range of causal gene variants, thus lowering study reproducibility of a single causal gene variant. Yet another confounder is that most of the earlier studies were inadequately powered with small sample sizes, which results in more false positives. Effect sizes of causal gene variants are also likely to be small, further reducing the ability of past studies, which are designed to identify larger effect sizes, to detect them. While the use of meta-analyses may improve statistical power by combining past studies, they are reli- ant on the quality of the original studies. Activin A and its related receptors belong to the transforming growth factor β-family , and are ubiquitously expressed throughout the body, where they mediate numerous cellular functions such as proliferation, differ- entiation, and apoptosis . To identify novel interactions and possible func- tions of susceptibility genes, and prioritize efforts for future functional studies, we previously pursued a novel integrative bioin- formatics approach based on transcriptome profling . Genetic and familial predisposition to eclampsia Obstet Gynecol 32(3):303–311 and preeclampsia in a defned population. Torbergsen T, Oian P, Mathiesen E, Borud O eclampsia across generations: exploring fetal and (1989) Preeclampsia – a mitochondrial disease? Mutze S, Rudnik-Schoneborn S, Zerres K, severe preeclampsia amongst mothers and Rath W (2008) Genes and the preeclampsia mothers-in-law of preeclamptics and controls. Dai B, Liu T, Zhang B, Zhang X, Wang Z (2014) Polymorphisms in infammatory genes (2013) The polymorphism for endothelial are associated with term small for gestational nitric oxide synthase gene, the level of nitric age and preeclampsia. A pre- risk of preeclampsia: an updated meta-analysis eclampsia genome-wide linkage scan in based on 51 studies. New Zealand confrms the presence of a Hum Biol 76(6):849–862 maternal susceptibility locus for preeclampsia, 57. Accessed effect of 10q22 in preeclamptic females coin- 2015 cides with two regions clustered for genes with 71. Wang Q, Wang G, Guo C, Cao X, An L, Du down-regulated expression in androgenetic M, Qiu Y, Yang Y, Wang Y, Wang S, Wang X, placentas. Women who develop hypertensive disorders during pregnancy are considered to have “failed” the cardiovascular stress test of pregnancy and likely represent a subpopulation with inadequate cardiovascular accommodation. Preeclampsia is a serious complication with a myriad of manifestations in both mother and offspring. This pregnancy syndrome is a polygenic disease and has now been linked to a greater incidence of cardiovascular disease. Moreover, offsprings born to preeclamptic mothers exhibit an elevated risk of cardiovascular disease, stroke, and mental disorders during adulthood. This suggests that preeclampsia not only exposes the mother and the fetus to complica- tions during pregnancy but also programs chronic diseases during adulthood in the offspring. The etiology of preeclampsia remains unknown, with various theories being suggested to explain its origin. It is primar- ily thought to be associated with poor placentation and entails excessive maternal infammation and endo- thelial dysfunction. It is well established now that the maternal immune system and the placenta are involved in a highly choreographed cross talk that underlies adequate spiral artery remodeling required for uteroplacental perfusion and free fow of nutrients to the fetus. Although it is not clear whether immuno- logical alterations occur early during pregnancy, studies have proposed that dysregulated systemic and placental immunity contribute to impaired angiogenesis and the onset of preeclampsia. This chapter will focus on important aspects of epigenetics, immunological aspects, and cardio- vascular and vascular remodeling of preeclampsia. It remains a major obstetric concern owing to the associated high prevalence of maternal and fetal mortality and morbidity. Although the etiology is not well characterized, several pathophysiological mechanisms combined have proven to Padma Murthi and Cathy Vaillancourt (eds. All these factors may interact with the genome of the mother and the fetus in terms of gene expres- sion modulation, ultimately affecting the expressed phenotype. The placenta is extremely important for intrauterine fetal development and growth. Early gamete alterations (of epigenetic origin) may be adequate to induce placental defects. Two concepts are mostly accepted: hypertension results either from defects in fetal or placental tissues itself or from a maladapted maternal response to pregnancy. These modifcations typically turn genes on or off, allowing or preventing the gene from being used to make a protein . Exposure to different environmental stimuli (ethanol, oxygen tension, and assisted reproduction technologies), particularly during critical windows of development, results in the formation of adaptive epigenetic marks as part of the adaptive stress response . These are usually established early during development and act as regulators of developmental, tissue, and sex-specifc gene expression . These may be heritable if they occur in the gametes and can have phenotypic consequences in the next generation . Methylation of vital regulatory sites such as gene promoters Epigenetics and Preeclampsia 75 or enhancers is mostly connected to gene repression, resulting in downregulation of gene expression . Therefore, there is a discrepancy between the reported hypomethylated status and the observed downregulated activity of these genes in other studies. It is tempting to speculate that this is a compensatory change in methylation to ensure favorable offspring functioning, but on the other hand, it can be an atypical decrease in gene expres- sion that can lead to metabolic maladaptation. Although this does not prove any causal relationship with long-term health effects, it can be used as an initial proof of concept to conduct new cohort studies . It was clarifed that these molecules are implicated in several diseases, and successful revelation of their role in developmental programming can lead to possible biological biomarkers or targets for therapy . Structural and functional changes in the vas- culature are considered independent risk factors for long-term cardiovascular events [35, 36]. Moreover, distur- bances in endothelial function and high blood pressure may affect arterial elasticity and consequently enhance stiffness . A study postulated the hypothesis that timely arterial hypertrophy could favor a “structural” increase in compliance by decreasing the relative amount of connective tissue . Recently, studies have revealed that both immunological toler- ance and immunocompetent cells are important contributors to normal placentation or spiral artery remodeling by extravillous tro- phoblasts, which establish adequate fow of nutrients to the fetus.
Moreover buy 120mg xenical with amex, it should be pointed out that cervicofacial subcutaneous emphysema and pneumomediastinum have been reported after the injection of pressurized gas during retinal detachment surgery purchase xenical 120mg mastercard. It should be emphasized that resorption time is not always uniform or predictable buy xenical 120mg visa. For example, a diabetic 19-year-old woman was injected with sulfur hexafluoride 25 days before subsequent surgery and a diabetic 37-year- old man was injected with perfluoropropane gas 41 days before subsequent surgery. They were given nitrous oxide and developed central retinal artery occlusion and permanent blindness in the affected eye. A scleral buckle procedure is basically an extraocular circumglobal placement of a band. During globe manipulation, rotation of the globe with traction on the extraocular muscles may elicit the oculocardiac reflex. Anesthesiologists are sometimes faced with the unpopular duty of triaging the order of unscheduled cases. Clearly salvage of life takes priority over salvage of limb, but where do nonelective eye operations fit in? A rhegmatogenous retinal detachment is the most common posterior segment emergency. It occurs when a break or tear in the retina allows vitreous fluid to dissect underneath the retina. For the former, the macula remains attached, preserving central vision and retaining high likelihood of ultimately achieving excellent visual acuity. In fovea-involving detachments, the macula is separated, so the prognosis for ultimate visual acuity of 20/40 or better is much lower. Although it seems logical that the sooner the retina is reattached, the better the prognosis, clinical evidence suggests that duration of macular detachment has little to no effect on visual outcome so long as the repair is accomplished within about 1 week. Studies have suggested that surgery within 72 hours reduces the incidence of vision-threatening endophthalmitis. Recent literature challenges this guiding principle, because not a single case of endophthalmitis or other deleterious side effects arose during Operation Iraqi Freedom and Operation Enduring Freedom despite a 21-day median time to foreign body removal. Indeed, strabismus surgery is the most common pediatric ocular operation performed in the United States, and it entails a variety of techniques to weaken an extraocular muscle by moving its insertion on the globe (recession) or to strengthen an extraocular muscle by eliminating a short strip of the tendon or muscle (resection). Infantile strabismus occurs within the first 6 months of life and is often observed in the neonatal period. Moreover, strabismus may be acquired secondary to 3479 oculomotor nerve trauma or sensory abnormalities such as cataracts or refractive aberrations. In addition to the well-known propensity of strabismus surgery to trigger the oculocardiac reflex (previously discussed), strabismus or ptosis patients are thought to have an increased incidence of malignant hyperthermia. Although recent studies have challenged this belief, anesthesiologists providing care for eye muscle surgery patients must be cognizant of the theoretically enhanced risk. This simple test provides valuable clues to the presence and site of mechanical restrictions of the extraocular muscles and is most valuable in patients who have previously undergone strabismus surgery, in those who may have paralysis of one of the extraocular muscles, and in those who have sustained orbital trauma. If additional intravenous atropine is indicated, it is not given while the oculocardiac reflex is active in case even 3480 more dangerous cardiac dysrhythmias are triggered. The laryngeal mask can be inserted without the use of muscle relaxants, causes less hemodynamic perturbation, and is associated with less straining and coughing on removal. Vomiting after eye muscle surgery is common, giving credibility to the existence of the oculogastric reflex. However, the droperidol doses used for postoperative nausea and vomiting are extremely low and unlikely to be associated with notable cardiovascular events. Combination therapy consisting of one or two antiemetics, each with a different mechanism of action, plus a glucocorticoid such as dexamethasone has been shown to be efficacious and safe in patients at high risk for postoperative nausea and vomiting. The invention has revolutionized industry, refined scientific measurements, provided therapy for countless medical and surgical conditions, and inspired 13 Nobel Prizes. The principle is based on the consequences of a photon meeting an electron in an excited state. Sometimes 3481 the collision produces a second photon that has the same color and direction as the original. The term laser was coined to describe this photon-cloning effect, and the acronym signifies light amplified by stimulated emission of radiation. Because it is monochromatic, all the photons have the same wavelength, energy, and frequency. The amount of radiant energy (joules) absorbed by tissues is the product of power (watts) multiplied by duration (seconds). The effect that a particular laser beam exerts on tissue depends predominantly on its wavelength and power density. A specific laser’s wavelength depends on its lasing medium, which also gives the laser its name. Of course, another variable that can be manipulated to produce a given effect is the duration of contact between laser beam and tissue. Additional uses of lasers of low-power density include the photoactivation of systemically administered dyes to precisely treat localized disease sites, such as with age-related macular degeneration. Lasers are used to treat a wide spectrum of eye conditions, including three of the most common causes of visual loss in the United States: diabetic retinopathy, glaucoma, and age-related macular degeneration. The use of lasers expanded to include the rapidly growing field of refractive surgery. Owing to concerns that indirect exposure to laser energy could cause ocular damage to operating room personnel, staff working with or near the laser wear protective goggles designed to block the particular wavelength of light emitted by the laser in use. The argon laser emits blue-green light with a wavelength of approximately 488 to 515 nm (approximately 0. Light from the argon laser is strongly absorbed by hemoglobin, melanin, and other pigments, rendering it useful in retinal detachment surgery to photocoagulate or cauterize pigment epithelium and the adjacent neurosensory retina, thus creating an adhesion 3482 between the retina and the “wall of the eye” to keep the retina attached. This photocoagulative property of the argon and similar lasers achieves its therapeutic effect in the treatment of diabetic retinopathy by focal and controlled necrosis of a limited amount of ischemic retina. The argon laser is also used with some efficacy to treat the late complications that can develop in the natural history of retinal vein occlusion. Because emissions of the argon laser can penetrate the cornea and lens, causing severe retinal damage, personnel in the vicinity of the argon laser should wear orange protective goggles. Personnel working in the vicinity of this laser should wear green goggles and realize that their ability to detect cyanosis will be impaired. The term excimer is short for “excited dimer,” and exciplex is short for “excited complex. Under appropriate conditions of electrical stimulation, a pseudomolecule called a dimer is generated, which can exist only in an energized state and gives rise to laser light in the ultraviolet range, typically with wavelengths of 125 to 200 nm. The ultraviolet light from an excimer laser is well absorbed by biologic matter and organic compounds. Instead of burning or cutting material, the excimer laser supplies enough energy to disrupt the molecular bonds of surface tissue through ablation. This property allows removal of exceptionally fine layers of surface material with almost no heating or change to neighboring tissue.