Prevention of postoperative endophthalmitis – some random thoughts

Postoperative endophthalmitis (PE) is the most dreaded complication in any intraocular procedure. Most PE are exogenous and are preventable by diligent observance of disinfection and sterilization procedures and control of risk factors. Some of the procedures that we follow, like use of perioperative systemic or topical antibiotics, do not have any scientific backing. On the other hand, use of povidone iodine solution has proven benefits.[¹] The prospective European Society for Cataract and Refractive Surgery (ESCRS) study advocates the role of intracameral (I/C) cefuroxime in lowering PE. Several surgeons were using Moxifloxacin drops intracamerally for many years. But the landmark study by Haripriya et al.[²] in a retrospective analysis of more than 6 lakhs eyes compared the PE rate before and after initiation of intracameral moxifloxacin prophylaxis for both phacoemulsification and sutureless manual small-incision cataract surgery (M-SICS) and in patients with posterior capsular rupture. There was a three-fold reduction in PE in the M-SICS group with I/C Moxifloxacin, whereas it was a six-fold reduction in Phacoemulsification. This study has emphasized the role of intracameral Moxifloxacin in all routine intraocular surgeries. However, endophthalmitis prophylaxis failures with intracameral antibiotics after phacoemulsification have also been reported.[³] Of the 216,141 surgeries in a study in Northern California, endophthalmitis occurred in 0.020% of moxifloxacin-injected eyes and 0.013% of cefuroxime eyes. Of the 34 (0.016%) cases of endophthalmitis in which cefuroxime 1 mg was injected into 13 eyes and moxifloxacin 0.1% into 21 eyes, endophthalmitis cases with positive cultures were generally related to organism resistance in cefuroxime eyes but to sensitive organisms in moxifloxacin eyes where the doses may have been insufficient in eyes with a larger postoperative anterior chamber volume.

The National Accreditation Board for Hospitals & Healthcare Providers guidelines have stressed the importance of proper infrastructure and comprehensive measures and protocols for preventing nosocomial infections. Although conventional Split Air Conditioners are acceptable in entry level accreditation of a small healthcare organization, Air Handling Units (AHUs) are mandatory for full accreditation. However, it is important to factor that they increase the capital cost substantially.

Indoor air quality is of utmost importance in the operating room where there should be no known contaminants at harmful concentrations. Several measures are mentioned to reduce the microbial load of air in the Operation Theatre (OT).

Minimum Efficiency Reporting Value rated filters, for example, High Efficiency Particulate Air filter, ensure clean ventilation in the OT through an AHU. In an AHU, clean, cooled, and dehumidified air is passed through a series of filters which include a 20-micron prefilter with 90% efficiency, a 5-micron fine filter with 95% efficiency, and a terminal High Efficiency Particulate Air filter with 99.97% efficiency. The suction side of the AHU will have a damper arrangement (valve) to draw fresh air during each recycling stage. Laminar air flow units which provide positive pressure ventilation above the operating area significantly reduce the bacterial colony forming units in the surgical field, but some studies question the efficiency of such units in preventing sepsis[⁴] in a statistically significant manner. In a systematic review and meta-analysis of 1947 records of orthopedic, abdominal, and vascular surgeries, no benefit of laminar airflow as compared to turbulent ventilation was found in reducing the risk of surgical site infection in total hip and knee arthroplasties and in abdominal surgery.

Germicidal Ultra Violet (UV) lights which emit UV-C radiations (253.7 nm) are bactericidal. However, those below 240 nm will produce Ozone which is toxic to the personnel inside the OT. Exposure to UV radiation can produce erythema of skin and painful keratoconjunctivitis. UV lights installed in rooms and even in the air ducts and split ACs can help in supplying clean air. The bactericidal effect of UV light is dependent on the irradiation dose and dwell time (the time the particle is exposed in the killing region of the radiation). Hence, proper planning should be made on the wattage and number of lamps to be installed in the desired area.

Magnetized air media filtration (Electrostatic filters) can filter the indoor air. Germicidal lamps create positive-charged and negative-charged oxygen molecules which act like hydroxyl radicals and can destroy the cell wall of microbes. Photocatalytic oxidation occurs, releasing hydroxyl radicals when UV light and ambient light falls on surfaces sprayed with titanium dioxide (Nano TiO2). Hydroxyl radicals thus created harm the microbes.

Sterilizing instruments and linen are of utmost importance in reducing endophthalmitis. Steam under pressure is the most economical and effective method to sterilize items that are heat-resistant. Class B autoclave is a steam sterilizer that uses a vacuum pump to remove air/steam mixtures from the chamber prior to the beginning of sterilization. This process can remove 99% of the air inside of the chamber before the temperature and pressure increases to its stipulated parameters. Class B autoclave is the ideal one for use, whereas N type which has no vacuum pump can only be used as an auxiliary unit. Ethylene oxide sterilization can be used for heat-sensitive items like rubber and plastic. Sharp instruments are also best sterilized by ethylene oxide. It is always better to have sufficient sets of surgical instruments for the day's surgery rather than sterilize used ones in between cases. A slight increase in capital cost to have enough surgical sets is worth the investment.

There should be a disinfection protocol for every hospital. Daily cleaning and weekly cleaning procedures should be properly supervised. The right disinfectants at the right dilution must be used in the right way to clean surfaces. One cannot underestimate the role of periodic training to the OT staff to inculcate the correct attitude and work ethic in the practice of the infection control protocols. Properly designed operation theater complex will ensure that there would not be mixing up of clean and dirty linen and materials. The traffic inside the OT should be streamlined so that there is no entry of staff and patients from unclean environment to clean zones. Staff at all hierarchies should develop a habit of religious adherence to OT discipline. OT is one area where there should be zero tolerance in implementing correct techniques of asepsis. With the recent trend of eye hospitals getting themselves accredited by National Accreditation Board for Hospitals & Healthcare Providers, there has been a shift in the mindset of managements and staff to develop the right infrastructure and protocols for control of nosocomial infections.