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.