DISUCSSION
SARS-CoV-2 is transmitted through close contact and droplets. Airborne transmission may occur during AGP including tracheal intubation, non-invasive ventilation, tracheotomy, cardiopulmonary resuscitation, manual ventilation before intubation, and bronchoscopy.
In view of the recent COVID-19 pandemic, tracheostomy guidelines and protocols have been revisited and updated with the aim of decreasing aerosol generation and viral transmission to health care providers. These include patient selection; timing of operation in relation to symptoms, quarantine duration and polymerase chain reaction test results; location of surgery; PPE requirements; minimising the number of health care providers; expertise in performing intubation and tracheostomy; and ways to decrease exposure to aerosolised secretions intra-operatively. [3,11-13]
WHO, CDC and CHP advocates full barrier protection when performing AGP including a face shield which acts as an additional physical barrier against splashes, sprays, and spatter of body fluids. However, the use of face shield hinders the use of a head-light when performing head and neck surgery. Prolonged use can give rise to fogging, carbon dioxide retention especially when combined with respirator, and impaired communication. Furthermore, as the number of infected patients increases world-wide, there is a global shortage of PPE. As a result strategies have been formulated to optimise PPE availability include minimising the need for PPE in health care settings, and ensuring rational and appropriate use of PPE.
In this study, we proposed the use of 2 horizontal anaesthetic screens and a clear sterile plastic sheet draped over a tracheostomy operative field. The rationale is to create a spacious and sterile closed environment for the surgeon to work in whilst preventing droplet and aerosol escape during the procedure, ultimately reducing the chance of viral transmission. Such a set-up is readily available, functional, non-time-consuming and cost effective.
The 2 horizontal anaesthetic screens acted as struts. The height and distance of which could be adjusted by the surgeon to ensure adequate working space whilst not obstructing anaesthetist’s view and working space at the cranial end. Surgical drapes were placed loosely over the 2 anaesthetic screens so that it conformed to the contour of the screens, resulting in a sterile and flat cranial and caudal surface, thereby increasing working space. Finally placement of a clear and sterile plastic sheet over the 2 anaesthetic screens and sealing over the caudal and left lateral edges helped to create a sterile box-like working area for the surgeon. It was imperative that the plastic sheet was pulled taut over the operative field so as not to compromise visibility. A long length of plastic sheet was allowed to drape over the cranial end without fixing to allow anaesthetist to reach the endo-tracheal tube. A length of plastic sheet measuring 14cm over the right lateral surface acted as a hood against droplet and aerosol spillage, under which the surgeon’s hands passed. Skin incision was performed using a scalpel knife followed by soft tissue dissection with monopolar diathermy. A suction catheter for smoke evacuation was placed over the surgeon’s contralateral side to prevent fogging and impaired visibility. On reaching the anterior tracheal wall, haemostasis was secured. Suction was then turned off prior to tracheotomy. In order to minimise aerosol exposure, complete paralysis of the patient was ascertained throughout the procedure; mechanical ventilation was stopped prior to tracheotomy; suction was not used during and after tracheotomy; all tracheostomies were performed by consultant surgeons, consultant anaesthetists and scrub nurses experienced in the management of airways and the procedure. Such a set-up did not adversely affect visibility and efficiency in performing tracheostomy as evidenced by an average operation duration of under 6 mins.
Our study demonstrated that despite meticulous tissue dissection and haemostasis, swift and bloodless tracheotomy, there was droplet contamination noted on plastic sheets of all 5 patients. Droplet contamination was centred over the lower neck which corresponded to the operating site for all patients. Droplet count decreased towards the periphery. The drop was less pronounced towards the right side where the surgeon stood and operated on. Droplet count was also noted on the right lateral surface of the plastic sheet, which acted as a hood further protecting the surgeon against droplet and aerosol contamination. The lack of droplet contamination on face shields of the surgeon and scrub nurse implied that the plastic sheet was effective in preventing droplet and aerosol spillage.
Results from our preliminary study suggested that the use of 2 horizontal anaesthetic screens and a clear sterile plastic sheet draped over a tracheostomy operative field can effectively prevent droplet contamination, obviating the need for a face shield given adequate eye protection and respirator. Such an approach can also be advocated for other AGP in an attempt to reduce droplet and aerosol contamination, and ultimately viral transmission to health care providers.
Larger scale studies with more patients and operating surgeons is warranted to justify such recommendations. Given the effectiveness of the plastic sheet in preventing droplet contamination, the role and efficacy of N95 respirator versus medical masks in preventing viral transmission can be re-assessed.