Respiratory secretions from Covid-positive patients (whether detected or not) could contaminate the OT environment. What are the safety measures?
Covid-19 is a highly contagious and transmissible virus, which spreads mostly through respiratory droplets (size 5-10 micrometres) which are expelled through coughing or sneezing. We now know that airborne transmission is possible too, through aerosols particles (less than 5 micrometres in size), by actions like talking in enclosed spaces like ORs.Contact transmission needs particular attention — respiratory secretions from Covid-positive patients (whether detected or not) can and will contaminate the OT environment, starting a chain of transmission.
Once out in the environment, the virus has been shown to survive in air for 2-3 hours, and on stainless steel and plastic — the materials used in OR equipment — for up to three days. On copper — a substance increasingly used in Western OTs, it lasts for a mere four hours, a fact to keep in mind while designing future OTs.
Before we dive into the micro-management of the OT environment, let us pay heed to Dr Rohini Kelkar, former Head of Department of Microbiology, Tata Memorial Hospital (Mumbai), who said: “The sources of contamination in an OT are dust, lint, skin cells and aerosol, which are controllable, and need to be controlled. There is no such thing as a sterile OT; we can only hope to reduce contaminants to acceptable or near-zero levels.”
Managing ventilation and air handling systems in hospitals during Covid
Engineering design is very important how clean OTs can be kept. An HVAC system typically consists of an air inlet, bank of filters, exhaust system and terminal HEPA filters. According to Dr Kelkar, the air quality standards to be maintained are:
• Temperature: At 21°C +/- 3°C. For joint replacement surgeries, 18°C +/- 2°C, to inhibit microbial growth.
• Relative humidity: 20-60%. Ideally, 35%.
• Air changes: At least 12-20 per hour, with at least four fresh air changes.
In normal times, ORs were always maintained at positive pressure of more than 2.5 Pascals with respect to adjoining areas; this pushed the OT air out, and avoided contaminated air from outside coming in.
In a Covid situation, one wants to prevent Covid-laced OT air from entering adjoining areas. Hence, a negative pressure environment is preferred. An air lock can be used as a negative pressure sink, and positive pressure maintained inside the OT with respect to the lock.
The most practical method is to convert the OT into a negative pressure zone with respect to adjoining areas. At a minimum pressure of – 2.5 Pascals, air bleeds in, which may compromise air quality, but OT air does not contaminate surrounding areas.
Monitoring of parameters
Covid has mandated a shift from measuring microbiological to engineering parameters. Apart from temperature, relative humidity and number of changes, other values to be monitored are pressure differentials across filters, filter and duct maintenance, testing of filters with DOPS, dust spot test or weight arrestance test, and particle counts.
Testing all patients undergoing non-emergency surgeries for Covid has become a given, but false negative reports remain a challenge, as do asymptomatic positive patients. The RT-PCR test for Covid was and remains the gold standard.
For those who test positive, the surgery must be postponed. In an emergency situation, one has to go ahead, irrespective of the Covid status of the patient. Dr Aruna Poojari, Head of Dept, Dept of Pathology & Microbiology, Breach Candy Hospital (Mumbai) suggested administering a screening checklist to all patients, asking them about symptoms, family members who may have tested positive etc. In case a surgery for a Covid – positive patient cannot be postponed, a dedicated OT and recovery must be assigned only for such cases.
Reducing the distance travelled between the pre-op ward and the OT, and the time taken to do so, is one of the ways of preventing transmission within the hospital. Dr Dhruv Mamtora, HOD Microbiology & Infection Control, Wadia Hospitals (Mumbai) advises a dedicated elevator to shift Covid positive patients between floors. Such elevators, and all common
passages they have traversed, must then be immediately sanitised.
“ In my opinion, N95 masks are the most important component of PPE, along with eye protection. Making sure every member of the OT team is equipped with it is critical,” said Dr Murali Chakravarthy, Director-Clinical. Affairs & Chairman, Central Infection Prevention & Control Committee, Fortis Hospitals. The highest amount of aerosol generation occurs when the endotracheal tube (used to ‘breathe’ for a patient under anaesthesia) is inserted or removed. Asking all nonessential personnel to leave the OT during these steps is advised. No longer can surgeons jump from case to case. One needs to give adequate time for the OT to be cleaned between cases, and for OT air to be replaced by fresh air. In Dr Mamtora’s facility, for example, there are 40 air changes per hour in the OTs, so it takes 15-20 mins for air to be replaced. Hence, his center mandates a gap of half an hour between cases in the same OT.
Dr Raju J George, CEO Shihab Thangal Hospital, Tirur says that a separate recovery unit — not connected to the central air-conditioning system — should be allocated for Covid-positive patients after the surgery. Nurses who work here must be regularly monitored for symptoms of Covid, and visitors must be restricted.
Said Dr Pravin Nair, Consultant Microbiologist & Head-Infection Control, Holy Spirit Hospital (Mumbai) : “ We were always prepared for outbreaks, but never for a pandemic. Microbiologists now need to be involved in selecting cleaning products; we look at its spectrum of effectiveness, cost and environment-friendliness. Spray-and-wipe products are preferred over those which need to be diluted, since the latter requires supervision. Surface cleaning needs to be emphasised ”.
The old mop and bucket system can’t go on, said Edward D’Souza, President — Service Master India and Director — Rare Hospitality. Colour coded mops and dusters will avoid cross-contamination. UV cleaning using UV-C rays, additionally to treat returned air in the AHU, is also an option.
As Dr Poojari mentioned, it is not practical to measure Covid levels in the OT environment. What can be done is visual inspection after cleaning, fluorescent markers, ATP markers, swab sticks and air sampling.
OTs and surgeons are raring to go. Before OTs that have been shut for months are brought back into operation, Sanjeev Kumar, President-Dusters Total Solution Pvt. Ltd recommends centralised fogging for 4-5 hours, cleaning of AHU, deep cleaning followed by manual fogging. If the swab tests are negative, the OTs are ready to be used for surgeries, albeit with all possible Covid precautions.
Compiled by Dr Mrigank Warriar