Okada M, Cordeiro Sousa D, Fabinyi DCA, Hadoux X, Edwards TL, Brown KD, Chiu D, Dawkins RCH, Allen PJ, Yeoh J, Van Wijngaarden. Ophthalmology Retina. Article in Press.
In the era of COVID-19 and concerns of transmission during ophthalmic surgery, retina specialists are faced with continued concerns on how best to protect themselves, patients, and staff from COVID transmission during surgery and to what extent retina surgery itself aids in transmission.
This succinct article in press addresses one of the first ex vivo and in vivo models that evaluate whether pars plana vitrectomies promote the aerosolization of droplets.
In the current literature, the authors first summarize that high speed instruments –such as bone or dental drills—are known to generate aerosols (aerosolized droplets). Vitrectomies also use high speed instruments that raise similar, but unverified concerns.
The authors presented 3 different models. The first in vivo model consisted of a closed-system vitrectomy in cadaveric sheep eyes in a perspex box using fluorescein-tagged balanced salt solution at 3 times points: during vitrectomy, air-fluid exchange, and air-gas exchange. Droplets were measured by a combination of a particle counter (small, medium, large size) and cobalt-blue filter with photographs. No fluorescein droplets were detected and no significant differences were noted in the particle count before and during vitrectomy. The second model used an open-air vitrectomy system using the vitrector probe in balanced salt solution. This model exhibited an increase in small sized particles, however, the results were not significant. The last model was a series of 18 patients that underwent a vitrectomy under regional anesthesia with measurements at multiple time points: before draping, during vitrectomy, and after drape removal. This model demonstrated that particle counts during vitrectomy were lower compared to pre-draping levels and that these levels did not change during multiple time points of the surgery or with specific maneuvers. However, the particle counts did rise towards the end the procedure and after drape removal. This finding suggests that the vitrectomy itself with valved ports is not associated with an increase in particle dispersion in a small sample size. However, an increase in aerosolization may be highest during the end of the case and the drape removal process.
This study is a strong first article on a small scale that evaluates the possible aerosolization during vitrectomy in 3 different environments. The authors create a great stepping stone for future studies that are needed with larger sample sizes. Additional studies should address other considerations that could potentially promote or influence particle dispersion: length of time and specific actions of patient preparation before draping (ie. positioning head, tucking arms/legs, placing the nasal cannula, EKG leads) preoperative sterile preparation at surgical site, specific controlled surgical maneuvers, length of operative times, certain surgical indications/diagnoses, patient co-morbidities, and the method of supplementary oxygen delivery (nasal cannula versus Hudson face mask with or without superimposed standard masks).
Prethy Rao, MD MPH