Introduction

The COVID-19 pandemic has spotlighted the hazard of operating room personnel contracting serious infection from patients during procedures [1]. The aerosolization risk at minimally invasive surgery has been an especial concern given that the gas used to distend intracorporeal cavities can leak unfiltered into the operating room carrying with it any pollutant and pathogenic particles from the internal operating workspace [2,3,4]. While the transmissibility of pathogens by such a route remains uncertain, chemical constituents of surgical smoke can cause respiratory irritability and some are known to be mutagenic [5].

Transanal minimally invasive surgery (TAMIS) enables deployment of laparoscopic instruments intrarectally to achieve precise rectal dissection. Most commonly, TAMIS and its derivative Transanal total mesorectal excision (taTME) use a specific access device (Gelpoint Path, Applied Medical, Rancho Santa Margarita, CA, USA). In addition, proponents advocate use of a high-powered insufflation system with access port (AirsealTM, ConMed, Utica, USA) in order to maintain a stable operating field by minimising the fluctuations that otherwise occur due to gas leakage [6] and ensure efficient smoke evacuation [7]. While the Gelpoint Path platform is provided with valved access trocars, the Airseal system is often used with its valveless trocar. Both types of trocars allow gas to escape unfiltered [3, 8]. In use during TAMIS/taTME, also, these access devices lie in a horizontal position, different to the more vertical position with laparoscopic use. This means that fluid (blood, faeces and fluid) can enter directly into the trocar channels risking considerably more contamination of the operating room airspace (especially that occupied by the surgeon and assistant who are positioned close to the access interface). We sought to evaluate if indeed this occurs.

Methods

With institutional approval and informed patients’ and team consent (AEROSOLVE Study, IRB 1/378/2172), analytical measurements were carried out during TAMIS procedures using the Gelpoint Path access platform with two valved trocars in tandem with the Airseal insufflation system via its valveless access. Hook diathermy was used for cautery and at these times Airseal smoke evacuation mode was used. Carbon dioxide (CO2) gas leakage via the access port was examined using a sensitive thermographic camera (FLIR 343, FLIR Systems Ltd, UK) to visualise gas escape. Secondly, a sensitive particle handheld counter (Model 8306, Particles Plus, Stoughton, MA, USA) was used after training to measure particle counts occurring intraoperatively in the local operating room for sampling periods of 30-s duration. The particle counter cumulatively measures particles by laser diode with differential counting between 0.3 and 25 microns at a flow rate of 0.1 CFM (2.83 LPM) as well as humidity and temperature. Particle counts were measured at baseline (prior to operation) as well as intraprocedurally by placing the device’s isokinetic probe inlet 10 cm from the region of interest at each time point. For comparison, additional readings were taken similarly during laparoscopic procedures also using an Airseal device. Procedures were performed within an operating room environment with positive pressure ventilation (PPV, 25 room air changes/hr) with room temperature settings between 18 and 20 °C and humidity 50–60%. Hospital protocols regarding personal protective equipment and respect of the sterile field were adhered to at all times including, at this time, COVID-19 screening.

Results

Significant CO2 escape was thermographically visualised related to the transanal access port during use in TAMIS with a significant jetstream flowing continuously from the Airseal access trocar after commencement of gas insufflation (see Figure 1 and Video 1). Gas leak was also seen occurring episodically at other access points. The results of the particle count measurement are shown in Table 1. In general, particle counts were low prior to dissection phases of the operation but increased substantially (25 × 106/m3 or over 40× background counts) during tissue dissection with hook cautery. The majority of particles were in the 0.3–0.5 micron range (where counts were increased relative to background between 42× and 65) with the highest relative increase versus background in the 0.5–1.0 micron range. High amounts of smallest size particles remained present at the time of specimen extraction despite desufflation of gas from the rectum via the Airseal insufflation device. Particle counts < 5 were substantially greater during the TAMIS procedure versus laparoscopic procedures (a laparoscopic-assisted parastomal hernia repair and laparoscopic cholecystectomy) employing similar tools (although notably increased particle counts were also be found in the operative airspace during the non-TAMIS procedures).

Fig. 1
figure 1

Composite frames from thermographic video showing carbon dioxide jetstreams arising (a) continuously from the Airseal valveless access trocar (b) episodically from the valved trocars of the Gelpoint Path platform (c) intermittently from the insertion point of the Gelpoint Path device and (d) clouding in the operative airspace from all sources

Full size image
Table 1 Particles counts of local operative airspace external to the patient during TAMIS operation with counts from laparoscopic operations (also using Airseal for insufflation and hook diathermy for dissection) of similar duration. .bgd background. Colour shading in the table denotes increasing values within the individual columns per operation. For absolute readings green denotes least, orange middle and red highest. Re background ratios, white represents the lowest with shades of red darkening with higher values
Full size table

: Thermographic video showing gas jets carrying carbon dioxide from the operative work-space within the patient into the operative airspace. (MP4 13763 kb)

Discussion

When CO2 used to create space internally escapes to the exterior during TAMIS, considerable quantities of particles transfer with it even in the presence of smoke evacuation settings, as had been suggested possible by prior experimental work [9]. These particles include some of very small size (< 0.5 microns) which are important as such particles may remain airborne for a substantial period of time. While larger particles tend to fall to the ground, they first travel considerable distances in the turbulent jetstream before doing so. The small particle counts in aerosols at TAMIS are higher than for laparoscopic operations for similar timeframes perhaps because of the greater contamination of rectal fluid (including blood and enteric matter) directly into the access devices during operations. While the information for users sheet for the Airseal does recommend “positioning the patient lower than the device” for laparoscopy [10], it and its valveless trocar have been specifically approved for TAMIS use [11] even though this requires in-patient positioning. Although infection has not been proven to definitely spread to healthcare staff by such material nebulisation, chemical constituents of surgical smoke are known to be pathogenic. Therefore, N95/FFP2 masks, at a minimum, seem prudent [12] while other engineering methods evolve to ensure greater surgical team safety.