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\title{Aerosol Mediated Transmission of SARS-Cov-2 Or COVID-19 In the Cardiac
Surgical Operating Room}



\author[1]{Satish Kumar}%
\author[1]{Lalit Kapoor}%
\author[2]{dhiraj barman}%
\author[1]{Pradeep Narayan}%
\affil[1]{Rabindranath Tagore International Institute of Cardiac Sciences}%
\affil[2]{Affiliation not available}%


\vspace{-1em}



  
  \date{May 25, 2024}


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\selectlanguage{english}
\begin{abstract}
While there is significant awareness regarding droplet and contact
transmission, aerosols are generally underestimated as a potential mode
of transmission of SARS-Cov-2 infection. With the gradual resumption of
cardiac surgical activities, the cardiac surgical operating room will
become an important potential source of infection to the cardiac surgeon
and other healthcare workers participating in the operation. There is
also diminished awareness about the different aerosol generating
procedures (AGP) in the cardiac surgical operating room. In this
mini-review we intend to highlight the various aerosol generating
procedures that are common in cardiac surgery. This will help increase
the awareness among surgeons to AGP. A practical approach to taking
preventive measures have also been discussed.%
\end{abstract}%



\sloppy


\textbf{Abstract}

While there is significant awareness regarding droplet and contact
transmission, aerosols are generally underestimated as a potential mode
of transmission of SARS-Cov-2 infection. With the gradual resumption of
cardiac surgical activities, the cardiac surgical operating room will
become an important potential source of infection to the cardiac surgeon
and other healthcare workers participating in the operation. There is
also diminished awareness about the different aerosol generating
procedures (AGP) in the cardiac surgical operating room. In this
mini-review we intend to highlight the various aerosol generating
procedures that are common in cardiac surgery. This will help increase
the awareness among surgeons to AGP. A practical approach to taking
preventive measures have also been discussed.

Apart from droplet infection and transmission through fomites it is now
well established that coronavirus can spread through aerosols as
well.(1) However, a significant research gap exists in the epidemiology
of the risk of transmission of infections from patients undergoing
aerosol generating procedures (AGP). (2) AGP are generally thought to be
a concern for the anaesthetists and the risk to cardiac surgeons is
grossly underestimated.

Even before the current corona pandemic, a global outbreak of
invasive~\emph{Mycobacterium chimaera} has been reported in cardiac
surgery due to aerosol release. This occurred through breaches in the
heater-cooler units used in cardiopulmonary bypass circuits\emph{.} (3)
Thus, the risk of aerosol mediated transmission is very real and the
need for safety measures are extremely practical.

The COVID-19 virus spreads predominantly through droplet and aerosol
routes and blood-borne infection is not considered a major source of
transmission .(4) There are some major differences between droplet and
airborne transmission that leads to airborne transmission in the
operating room more of a hazard than the droplet route.

Based on e electron microscopy the size of the coronavirus-shaped
spherical particles is estimated to be about 0.125 microns (125 nm) and
ranges from 0.06 microns to 0.14 microns. (5) While droplet infections
are via larger respiratory particles, generally above 5\selectlanguage{greek}µ\selectlanguage{english}m diameter, and
are subject to gravitational forces, aerosol mediated transmission
occurs with smaller respiratory particles (generally\textless{}5\selectlanguage{greek}µ\selectlanguage{english}m)
circulating in the air. As a result, while contact is necessary for
droplet infections and thereby handwashing and gloves are highly
effective against contact transmission, viral particles transmitted
though aerosol is absorbed via the respiratory mucosa and potentially
across the conjunctivae other measures are required to prevent
transmission. These smaller viral particles (\textless{}10\selectlanguage{greek}µ\selectlanguage{english}m) are most
likely to penetrate deeply into the lung and cause infection.(6)The
radius of spread is also different and is no more than one meter for
droplet infections. However, because of the smaller size the SARS-CoV-2
or COVID-19 as it is popularly known as, can spread across larger areas
and has been shown to remain viable in aerosols even at 3 hours.(7)

The highest viral load of the virus causing COVID-19, is in sputum and
upper airway secretions and endotracheal intubation is the commonest and
most relevant aerosol generating procedure in cardiac surgery. (8)

Apart from intubation and extubation, bag mask ventilation, suctioning
of airways, insertion of chest drains and thoracotomies can all lead to
aerosol generation. (9) In paediatric cardiac surgery, valve repairs and
at times in coronary artery bypass operations as well, transesophageal
echocardiography (TEE) is often used. TEE carries an increased risk of
transmission of SARS-CoV-2. While this risk is greater in non-intubated
patients, viral transmission may still occur through direct contact with
the patient's secretions, resulting in contaminated hands and surfaces
with the potential to infect not just the echocardiographers but also
other personnel in the operating room. (10) Sternotomy requires a high
-speed device and is considered to be a procedure that leads to blood
and tissue fluid aerosolization. (4) Surgical smoke produced by heat
generating devices in cardiac surgery can also contain chemicals, blood
and tissue particles, bacteria, and viruses. (11)

Carbon di-oxide (CO2) insufflation in the operative field is practiced
in both open cardiac surgical procedures as well as minimally invasive
cardiac surgery to aid in de-airing and prevention of air embolism. This
has more relevance in minimally invasive cardiac surgery as minimal
invasive cardiac surgery often does not permit normal de-airing
maneuvers. (12) OPCAB surgery relies heavily on using a blower-mister
which used CO2 with saline and perhaps contribute to aerosol generation
as well.(13)Disconnection of ventilatory circuits during use;
cardiopulmonary resuscitation (before tracheal intubation);
bronchoscopy; and tracheal suction without a `closed in-line system,
nasogastric tube insertion are the other examples of aerosol generating
procedures. (8)

Prevention of aerosol-based transmission requires two approaches.
Firstly, minimizing aerosol generating procedures and secondly
protecting against exposure.

Minimizing aerosol generation:

Since the greatest risk of aerosol generation is from endotracheal
intubation preventive measures should primarily focus on minimizing the
risk at this very stage. It is recommended that adequately ventilated
single rooms should be used when performing aerosol-generating
procedures. Hospitals could make adjustments to their intubation and
operating practices. Ideally it should be seen if it is possible to
convert any of the operating rooms to negative pressure environments
with airflow changes (\textgreater{}12 air flow changes/hour).(8)
Failing this, patients could be intubated in a room next to the
operating room. If such a room does not exist and if there are two OR's
next to each other one of them could perhaps be used as an anesthetic
room for intubating and the other one for operating.

However, most of the centers across the world, the intubation is
performed is either performed in a positive pressure environment or
often even inside the operating room. The positive pressure airflow
environment of the operating room is a risk factor for viral spread and
thus aerosols once released actually stay in the environment for 3 hours
or longer which often is the duration of the cardiac surgical procedure.
In these situations, following intubation of the patient, the air
conditioning should be turned off and after 20 minutes to allow for the
droplets and aerosols to settle, the floors should be cleaned. This is
known to clear the settled aerosols without refreshing the spread.(8)

Reducing the use of blower-mister during OPCAB as far as practicable and
depending on traditional measures for de-airing after open cardiac
surgery in preference to CO2 insufflation would also be useful in
reducing the aerosol load. So, TEE should only be performed in intubated
patients only in those perioperative situations in which the benefits
outweigh the risks.(10)

Protecting against exposure:

The minimum number of personnel that can safely conduct the procedure
should be present in the OR. Insertion of intra-pleural chest drains at
the start of the procedure and connecting them to the wall suction may
reduce the aerosol generated from the electro-cautery as well as from
the blower-mister in OPCAB surgery.

There is some evidence that double gloving for tracheal intubation might
provide extra-protection and minimize spread by fomite contamination of
equipment and surroundings.(10)

The use of fluid-repellent long sleeved gown, eye protection,
respirators and gloves are recommended to protect against aerosol
mediated transmission of infection. Eye protection should include
protection from side exposure with side shields or goggles.

The most common types of respirators in healthcare are N95 filtering
facepiece respirators (FFRs), surgical N95 FFRs, and powered air
purifying respirators (PAPRs). PAPRs reduce the aerosol concentration
inhaled by the wearer to at least 1/25th of that in the air, compared to
a 1/10th reduction for FFRs. PAPRs provide increased protection and
decrease the likelihood of infection transmission to the wearer as
compared to FFRs however there a PAPR has limited downward vertical
field of view as well as because of the blower noise may present
difficulty in communicating.(14) Evidence from systematic review and
meta-analysis have failed to confirm the superiority of one type of mask
(FFP3/FFP2/N95) over another (surgical facemask).(15) This could be
partly because of issues with doffing off techniques of personal
protective equipment and other training issues.

Conclusions: Awareness about aerosol generating procedures is key to
prevent transmission of aerosol mediated SARS-Cov-2 infection.
Minimizing aerosol generation as far as practicable and taking measures
to prevent exposure are important for ensuring safety of cardiac
surgeons and other team members.

References:

1. Fathizadeh H, Maroufi P, Momen-Heravi M, Dao S, K\selectlanguage{ngerman}öse \selectlanguage{polish}Ş, \selectlanguage{english}Ganbarov K,
et al. Protection and disinfection policies against SARS-CoV-2
(COVID-19). Infez Med. 2020 Jun 1;28(2):185--91.

2. Tran K, Cimon K, Severn M, Pessoa-Silva CL, Conly J. Aerosol
Generating Procedures and Risk of Transmission of Acute Respiratory
Infections to Healthcare Workers: A Systematic Review. PLoS ONE
{[}Internet{]}. 2012 Apr 26 {[}cited 2020 May 18{]};7(4). Available
from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3338532/

3. Diekema DJ. MYCOBACTERIUM CHIMAERA INFECTIONS AFTER CARDIOVASCULAR
SURGERY: LESSONS FROM A GLOBAL OUTBREAK. Trans Am Clin Climatol Assoc.
2019;130:136--44.

4. Cook TM. Personal protective equipment during the coronavirus disease
(COVID) 2019 pandemic - a narrative review. Anaesthesia. 2020 Apr 4;

5. Zhu N, Zhang D, Wang W, Li X, Yang B, Song J, et al. A Novel
Coronavirus from Patients with Pneumonia in China, 2019. N Engl J Med.
2020 20;382(8):727--33.

6. Gralton J, Tovey E, McLaws M-L, Rawlinson WD. The role of particle
size in aerosolised pathogen transmission: a review. J Infect. 2011
Jan;62(1):1--13.

7. van Doremalen N, Bushmaker T, Morris DH, Holbrook MG, Gamble A,
Williamson BN, et al. Aerosol and Surface Stability of SARS-CoV-2 as
Compared with SARS-CoV-1. N Engl J Med. 2020 16;382(16):1564--7.

8. Cook TM, El-Boghdadly K, McGuire B, McNarry AF, Patel A, Higgs A.
Consensus guidelines for managing the airway in patients with COVID-19:
Guidelines from the Difficult Airway Society, the Association of
Anaesthetists the Intensive Care Society, the Faculty of Intensive Care
Medicine and the Royal College of Anaesthetists. Anaesthesia.
2020;75(6):785--99.

9. Engelman DT, Lother S, George I, Funk DJ, Ailawadi G, Atluri P, et
al. Adult Cardiac Surgery and the COVID-19 Pandemic: Aggressive
Infection Mitigation Strategies are Necessary in the Operating Room and
Surgical Recovery. Ann Thorac Surg. 2020 Apr 27;

10. Nicoara A, Maldonado Y, Kort S, Swaminathan M, Mackensen GB.
Specific Considerations for the Protection of Patients and
Echocardiography Service Providers When Performing Perioperative or
Periprocedural Transesophageal Echocardiography During the 2019 Novel
Coronavirus Outbreak: Council on Perioperative Echocardiography
Supplement to the Statement of the American Society of Echocardiography.
J Am Soc Echocardiogr. 2020 Apr;S0894731720302194.

11. Liu Y, Song Y, Hu X, Yan L, Zhu X. Awareness of surgical smoke
hazards and enhancement of surgical smoke prevention among the
gynecologists. J Cancer. 2019;10(12):2788--99.

12. Nyman J, Svenarud P, Linden J van der. Carbon dioxide de-airing in
minimal invasive cardiac surgery, a new effective device. J Cardiothorac
Surg. 2019 Dec;14(1):1--8.

13. Plass CA, Podesser BK, Prusa AM. Effect of blower-mister devices on
vasoreactivity of coronary artery bypass grafts. J Thorac Cardiovasc
Surg. 2010 Oct 1;140(4):923--7.

14. CDC. Coronavirus Disease 2019 (COVID-19) {[}Internet{]}. Centers for
Disease Control and Prevention. 2020 {[}cited 2020 May 18{]}. Available
from:
https://www.cdc.gov/coronavirus/2019-ncov/hcp/ppe-strategy/powered-air-purifying-respirators-strategy.html

15. Effectiveness of Masks and Respirators Against Respiratory
Infections in Healthcare Workers: A Systematic Review and Meta-Analysis.
- PubMed - NCBI {[}Internet{]}. {[}cited 2020 May 18{]}. Available from:
https://www.ncbi.nlm.nih.gov/pubmed/29140516

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