DISUCSSION
The current global stockpile of PPE is insufficient due to the rapidly increasing number of infected patients world-wide. In view of global PPE shortage, 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 [9].
In Queen Mary Hospital, attempts at minimising PPE need include reducing the volume of head and neck patients undergoing outpatient clinic and endoscopy service by 60%, and operations by 50%; and the number of healthcare providers within endoscopy suites and operating theatre.
Based on current evidence, SARS-CoV-2 is transmitted between people through close contact and droplets. Airborne transmission may occur during AGP and support treatments including tracheal intubation, non-invasive ventilation, tracheotomy, cardiopulmonary resuscitation, manual ventilation before intubation, and bronchoscopy. Despite concerns of aerosolisation of blood through the use of energy device, manipulation of upper aerodigestive tract mucosa and resection of tumours in the upper aerodigestive tract are not classified as AGP [9-12]. According to World Health Organisation (WHO), droplet and contact precautions with the use of medical masks, eye protection, cap, gown and gloves are sufficient for regular care of COVID-19 patients. Respirators such as N95 or PAPR are advocated for AGP [9,13].
There is currently no universal standard for face and/or eye protection from biohazards. Face shield is usually in the form of an optically clear plastic film which covers the forehead to neck and both sides of the face up to the ears. Due to the lack of a good facial seal peripherally, face shields are usually used as an adjunctive PPE which acts to provide additional physical barrier against splashes, sprays, and spatter of body fluids [14]. 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.
Centres for Disease Control and Prevention (CDC) Standard Precautions guidelines for prevention of transmission of infectious agents includes the use of face shields (with a medical/surgical face mask) when sprays, splashes, or splatter are anticipated [15]. The effectiveness of face shields in preventing the transmission of viral respiratory diseases is unknown [16]. With the use of goggles and appropriate respiratory protection device, we re-evaluate the need for face shield in performing head and neck cancer surgical procedures.
In an attempt to conserve face shield and other PPE consumption, we minimised the number of health care providers during operation: all tracheostomy (n=8) was performed by the operating surgeon alone. Furthermore, second assistant was not involved in TORS and free flap harvest procedures. Only the operating surgeon and scrub nurse was involved in all 45 surgical procedures.
From our study, the percentage of procedures with droplet contamination was 57.8% for the operating surgeon , 59.5% for the first assistant and 8.0% for the second assistant. No droplets were noted on all face shields of the scrub nurse. In view of 0% contamination rate, face shield is not necessary for the scrub nurse for all non-AGP.
Droplet count was highest and most widespread with procedures involving osteotomies such as maxillectomy, maxillary swing and manubrial resection. Other than blood, irrigation fluid also contributed to the number of droplets. Vibrations of saw blade caused droplets to be dispersed over a large area during osteotomy, as reflected by the distribution on the surgeon and 2 assistants’ face shields (Figure 3, Table 1). This can be minimised by controlled irrigation and vigilant suction to minimise the amount of irrigation fluid and blood accumulating around the saw blade. Operation by an experienced surgeon would also help to reduce blood loss and shorten procedure time. Face shield should be provided for the operating, first and second assistant surgeons during osteotomy related procedures.
Non-osteotomy surgical procedures involving mucosa of the upper aerodigestive tract yielded minimal droplet count on face shields of the operating surgeon and first assistant, affecting zones 6-11 which were centred over the lower half of the face. There was one droplet splash at zone 2 of the first assistant during nasopharyngectomy, corresponding to the first assistant’s eye-level. No droplet splash was noted on the second assistant’s face shield. Abiding by CDC, WHO and CHP guidelines, face shield should be used by all surgeon(s) for AGP including tracheostomy and laryngectomy. For non-AGP, face shield for second assistant may not be warranted. Given the low droplet count on face shields of the operating surgeon and first assistant, one could argue against the need for face shield as an adjunctive PPE to goggles and adequate respiratory device for the aforementioned procedures which are non-aerosol-generating.
For TORS, docking was performed by the operating surgeon prior to commencement of surgery. In order to prevent droplet splash the following steps have been taken: (1) ensure that the cuff of the endotracheal tube was inflated with no evidence of air leak (2) Fr 16 Nelaton suction catheter was placed through the remaining nostril down to the level of the oropharynx for suctioning of saliva prior to docking and also of blood and diathermy smoke and aerosols during the operation. There were no droplets noted on the operating surgeon’s face shield during docking and none noted on the first assistant’s face shield after the operation. Hence face shield is not necessary for the operating and assistant surgeons when performing TORS.
Average droplet count from non-mucosal, non-osteotomy related surgical procedures such as neck dissection and free flap harvest was minimal on both the operating surgeon’s and first assistant’s face shields, mainly affecting the lower half of the face. One drop was noted in the lower half of the second assistant’s face shield during modified radical neck dissection. Given the low droplet count and low risk of aerosol generation of such procedures, one could argue against the routine use of a face shield as an adjunctive PPE for all surgeons when resources are low during the COVID-19 pandemic.
Given proper eye protection and adequate respiratory device, results from our preliminary study suggested that face shield as an adjunctive PPE was not mandatory for all head and neck surgical procedures. The following recommendations can be made when performing head and neck cancer surgery in an attempt to conserve PPE during the COVID-19 pandemic: (1) All operations are to be performed by an experienced surgeon assisted by specialists in the field of head and neck surgery in order to minimise operation time and droplet contamination. (2) Number of surgeons should be kept at a minimum for all procedures not limiting to AGP. (3) Face shield is advocated for operating and assistant surgeons for procedures involving osteotomies. (4) Conforming to CDC, WHO and CHP guidelines, face shield should be worn by surgeon(s) performing AGP in unknown, suspected and confirmed cases. (5) For non-AGP involving mucosa of the upper aerodigestive tract, face shield can be provided to the operating and first assistant surgeon if resources allow. (6) Routine use of a face shield as adjunctive PPE is not necessary for all parties when performing TORS and all non-AGP, non-mucosal and non-osteotomy related procedures. (7) Scrub nurse could be spared of using a face shield for all non-AGP. (8) If resources allow, all patients to be operated on can be quarantined in hospital 14 days prior to surgery, followed by 2 sets of PCR tests performed 24 hours apart. This would further ensure that patients are COVID-19 free prior to operation whereby we can revert to standard droplet precautions. Larger scale studies with more patients, procedures and operating surgeons is warranted to justify such recommendations. Other means to conserve PPE for instance the role and efficacy of N95 respirator versus medical masks in preventing viral transmission is beyond the scope of this study.