What is Toxic Anterior Segment Syndrome (TASS)?
Toxic anterior segment syndrome (TASS) is a pure postoperative inflammatory reaction caused by a non-infectious substance entering the anterior segment, resulting in toxic damage to intracellular tissue. This process usually begins 12 to 48 hours after cataract / anterior segment surgery, is limited to the anterior segment of the eye, is always Gram stain and culture-negative, and generally improves with steroid treatment. The primary differential diagnosis of this toxic anterior segment syndrome is infectious endophthalmitis.
A review of the literature suggests that possible causes of toxic anterior segment syndrome (TASS) include intraocular solutions with inappropriate chemical composition, concentration, pH, or osmolality; Preservatives; Dinachard ophthalmic visco-surgical equipment; Enzymatic detergents; Bacterial endotoxin; Rusty metal deposits and residues; And factors related to intraocular lenses, such as polishing or sterilizing compound residues. The prevalence of Toxic anterior segment syndrome (TASS) is an environmental and toxic control problem that requires a thorough analysis of all medications and fluids used during surgery, as well as a complete review of the operating room and sterilization protocols.
Anterior segment toxic syndrome (TOS), acute non-infectious inflammation of the anterior segment of the eye, which is a complication of anterior segment eye surgery; Cataract removal is the most common form of this type of surgery. Various contaminants from surgical instruments or supplies are commonly indicated as causes of release. The toxic anterior segment syndrome usually develops within 24 hours after surgery and is characterized by corneal edema and accumulation of white blood cells in the anterior chamber of the eye.
Although most cases of release can be successfully treated with topical steroids, topical non-steroidal anti-inflammatory agents, or both, the inflammatory response associated with release can cause severe damage to intracellular tissue, resulting in loss of vision. In October 2006, the Maine Department of Health and Human Services (MDHHS) received a report of a change in patients undergoing cataract surgery at a Maine hospital. The MDHHS and CDC group investigated and worked with an ophthalmologist and a hospital to treat and prevent additional cases.
This report describes the results of that investigation and subsequent preventive measures. Although a specific cause for the toxic anterior segment syndrome outbreak has not been identified, no additional cases have been reported after two consecutive changes in the materials and equipment used for the surgery. Prevention of Toxic anterior segment syndrome (TASS) requires careful attention to ophthalmic solutions, medications, and devices, and cleaning and sterilizing surgical instruments can have several causes.
Topical eye drops
Many of the solutions used in the ophthalmology department contain toxic preservatives or stabilizing agents for the corneal endothelium if access to the anterior segment of the eye is available. The corneal endothelium is very sensitive to the preservatives used in many topical eye drops, the most common of which is benzalkonium chloride (BAK). There have been many reports of patients with significant corneal edema or endothelial cell damage as a result of BAK-containing solutions.
Furthermore, BAK has been found to cause significant corneal edema when used as a preservative in OVD. While low concentrations of preservatives are relatively safe when used on the surface of the eye, other preservatives such as methylparaben used in BAK or lidocaine should be avoided in any of the previously used or previously accessible medications. Eye department during surgery.
Agents that are used to stabilize intraocular reactions can also lead to the development of shaking. Although not technically preservative, these agents have been found to be toxic to the endothelium and other cells of the anterior segment of the eye. Commonly used stabilizing agents are bisulfites or metabisulfites. They are often used to stabilize epinephrine, which is then attached to the BS during surgery to help dissociate the pupil.
Cataract anaesthesia is now commonly used during cataract surgery to help reduce pain and topical sedation. Preservative-free narcotics at low concentrations were found to be safe and did not cause signs of endothelial toxicity. Lidocaine MPF (without methylparaben) 1% is the most widely used intracameral anaesthetic. However, the preservative drug can cause endothelial poisoning.
Furthermore, the intracameral anaesthetic at high concentrations damages the endothelial tissue. For example, lidocaine levels of 2.0% or more caused significant corneal hardening and blurred vision after surgery. Intracameral anaesthetics used during preoperative surgery are essential to avoid worrying and have the proper concentration.
Antibiotics are a potential source of toxicity when used in irrigation solutions during surgery or injected intramuscularly at the end of cataract or anterior segment surgery.
Antibiotics have been prescribed for many years to prevent endophthalmitis. Initially, vancomycin and gentamicin were added to the irrigation solutions to prevent endophthalmitis. However, there are concerns about the toxicity of these agents, especially gentamicin. This drug has a relatively narrow therapeutic index and can damage not only the anterior segment of the eye but also the posterior segment, causing macular infarction when used in high concentrations. The use of these antibiotics in BSS solutions for the prevention of endophthalmitis is not very favourable.
There is great interest in the use of intracameral antibiotics at the end of surgery for the prevention of endophthalmitis. The use of cefuroxime was initially evaluated in multiple studies in Sweden to determine its immunity to endophthalmitis. When used intramuscularly in the correct 1 mg / 0.1 cc ration, cefuroxime has been found to be effective in preventing endophthalmitis and non-toxic. The European Society for Cataract and Refractive Surgery (ESCRS) endophthalmitis study recorded a significant reduction in the rate of endophthalmitis using intracameral cefuroxime compared to a third-generation topical fluoroquinolone antibiotic.
The main problem with the use of antibiotics like cefuroxime is that there is no single-use antibiotic approved in the United States for intracameral injections. Surgeons considering the use of intracameral antibiotics are advised to ensure that the antibiotics are mixed and dosed correctly to avoid dilution errors leading to release problems. It is important to dilute any intracerebral antibiotics under clean dilution conditions to avoid inflammation or contamination of the anterior segment.
Cleaning and sterilization of ophthalmic devices
Cleaning and sterilization of equipment used in anterior segment surgery have become a key issue in recent launch cases. The high prevalence of release unrelated to cytosol use peaked in April 2006. Increased number of cases reported to the University of Utah Intermountain Eye Research Center, as well as to representatives from Emory University and industry. An ad hoc task force funded by the American Society for Cataract and Refractive Surgery (ASCRS) was created to help investigate the outbreak, which eventually dissolved in mid-summer 2006.
The task force estimated that more than 130 different centres reported discard cases. The task force found no conclusive epidemiological evidence to suggest that a single product was responsible for the increase in the release, but careful analysis revealed multiple potential etiological factors related to release. The most important aspect of this outbreak is the cleaning and sterilizing of eye surgery equipment. Most centres report that there is very little time between cases to properly clean and process equipment.
This is an area of concern for several reasons, including proper washing of the handpiece and cannula at the end of the case. Due to the small internal diameters and openings of these devices, the use of reusable small-hole devices, such as cannulas, has been found to be a potential source of jarring. Additionally, the ultrasound and irrigation/suction handpieces used during phacoemulsification allow the formation of OVD and residual cortex, which in later cases can lead to inflammation when using these tools. It is important to thoroughly rinse reusable canvases and handpieces at the end of each box to not allow any material from these canvases and tools to dry out and build up.
Enzymes and detergents
The Working Group found that enzymes and/or detergents used to clean ophthalmic devices are an important factor in the etiology of Tas. Enzymes and detergents are toxic to corneal endothelium in humans and animal samples and cause corneal edema. When the residue of these cleaning materials accumulates on the internal surfaces of the reusable cannula or handpiece, the residue is especially toxic on the OVD frame or cortex. Enzymes and detergents are not completely inactivated when treated with high-temperature instruments used in autoclaving.
The task force found that the use of ultrasound baths in cleaning ophthalmic devices was another possible source of confusion. There have been numerous reports of ultrasound baths contaminated by gram-negative bacteria that produce heat-stable endotoxins that cause shaking. The heat used in autoclaving kills the bacteria themselves, while the endotoxins are active on the cell surface. Endotoxin residues can adhere to instruments or cannulas that have been cleaned in an ultrasound bath and can cause poisoning if injected into the eye. Endotoxins are very difficult to remove once they have access to ophthalmic devices.
Surgeons and surgical centres are encouraged to reconsider the use of ultrasound baths for cleaning ophthalmic devices. These baths are helpful in removing the massive contamination of devices that commonly occurs in general surgery, although this is rarely a factor in preoperative surgery. Complete rinsing of the ophthalmic handpiece and cannulated instruments at the end of each case should remove residual material such as cortex or OVD. Ultrasonic cleaning is not required as less bioburden is maintained in reusable ophthalmic devices. If used, the ultrasonic water bath must have strict protocols to avoid contamination or endotoxins.
The ultimate source of Toxic anterior segment syndrome (TASS) is related to water problems in equipment used to clean and disinfect equipment. Residual heavy metal condensates, as well as sulfate condensates and contaminants, were found in the water supply to steam sterilizers of autoclave systems. Eventually, these build-up to the point where the residue has access to sterile eyewear. Toxic anterior segment syndrome (TASS) diffusion has been reported to be associated with contaminants in autoclave steam moisture and heavy metals, which is secondary to improper handling of the steam sterilizer.