COVID-19 and Neurophysiology - Risks and Rewards
Whilst Australia’s suppression/elimination strategy has, for the majority of the Covid-19 pandemic, kept us at low risk as healthcare practitioners there still remains a significant risk to both ourselves, patients and the wider community particularly in regards to new emerging more infectious variants. 3561 Victorian healthcare workers acquired Covid-19 in 2020, with 73% of those in a healthcare setting. Nosocomial spread is a real risk and we should try and mitigate that risk where possible.
Covid-19 has put us as Neurophysiology scientists, like many healthcare workers, in a difficult position of providing a clinical service in a risk laden environment. The risk matrix is constantly in flux and we must carefully mitigate risk wherever possible. This has to be balanced against the number of active cases in the community and, unfortunately, the availability of PPE to scientists. Many of us have been put in difficult situations where we are asked to perform a task where we may not feel comfortable and through a better understanding of the current data around Covid-19 we can make better informed decisions and raise concerns where appropriate with Neurologists.
I will try and outline the latest data around risks to us as Neurophysiology scientists and suggest some possible mitigation strategies, many of which may already be in practice. I will also examine risks in performing routine EEG testing in Covid-19 and examine some of the usual standard practices around EEG. Please remember that new data and science around Covid-19 is emerging at a rapid rate and as new information arises we will need to constantly tailor our approach to accommodate this.
Aerosolisation risks
There has been some debate to the transmission risk of Covid-19 through aerosolisation although the evidence on consensus is strongly supportive of this as a mode of transmission. SARS-CoV2 survives in the air for in excess of 3 hours and longer on a range of surfaces found in healthcare facilities (1). There is also strong evidence that the virus can be transmitted in excess of the previously recommended 2 m safe distance (2). Variable rates of air exchange in hospital rooms can also increase the risk, as can patients with coughing or rapid breathing who have been shown to generate more aerosols. Coughing, often associated with the hyperventilation procedure, has been shown to generate more aerosols than tracheal intubation (3). Droplet precautions are insufficient in a setting of aerosolisation risk with N95 masks and eye protection recommended by the WHO in this setting (4). Singapore who learnt hard lessons from the previous SARs epidemic has restricted healthcare worker infections to 40 using strict airborne precautions and patient isolation (5,6,7). The current Australian Government Department of Health recommendations (13) recommend only waring an N95 mask when performing an aerosolising procedure on a Covid-19 positive patient and are inadequate when compared to recommendations from the WHO and other international bodies such as the CDC.
Paediatric Population risks
Initially paediatric patients were thought to be of very low risk for acquisition and spread of the virus, however, the data has changed significantly on this particularly with the advent of new variants. The UK recently reported infections in children (ages 5 to 12 years) and young adults (18 to 24 years) at 5 times the rate of those aged 65 years and older (8). This cohort was primarily the delta variant (>90%). Although this data is somewhat skewed by very strong vaccination uptake in the UK in the older population this shows a worrying trend in children when you consider that the UK reported 51,273 cases on 15/07/2021. Paediatric cohorts are typically where the greatest reward for hyperventilation resides particularly in regards to childhood absence epilepsy.
Vaccination protection of the individual
Both Astra Zeneca and Pfizer vaccines provide excellent protection against the current delta variant with Pfizer offering 96% protection from serious disease resulting in hospitalisation and Astra Zeneca 92%. A recent Canadian study shows that Pfizer is 87% (11) effective at preventing infection although an Israeli government study put this at 64%. UK health states that Astra Zeneca is around 60% effective at preventing symptomatic infection. The majority of reported deaths in the UK with the recent Delta variant have been in the unvaccinated, with a small number in those receiving one dose of the vaccine and fewer in those who have received 2 doses. The majority of the deaths in the vaccinated were in the over 50s age group. As the vaccination rate rises in a country you will see a greater proportion of deaths occurring in the vaccinated. These will be hopefully dramatically reduced on the expected deaths in an unvaccinated population.
Vaccination protection against onward transmission
There is emerging data around the ability of vaccinations to protect from onward transmission from those who are vaccinated; this is of course of high importance to healthcare workers who may inadvertently spread the virus when asymptomatic/pre-symptomatic. A recent study in the UK, primarily vaccinated with Astra Zeneca, suggests that the protection against onward spread for the vaccinated is at around 40-50% (9) although this data did not account for asymptomatic cases. A study from Israel, Pfizer being the exclusive vaccine used, showed significantly less virus present in nose swabs of positive patients who had been vaccinated putting them at lower risk for onward transmission (10). A recent small study reported that 43% of vaccinated Covid-19 positive workers were asymptomatic (12). This raises the question of whether regular testing of staff should be mandated during outbreak periods.
Hyperventilation risks
Hyperventilation is an aerosolising procedure and we need to assess the risks and benefits of performing it in the setting of an outbreak.
Hyperventilation is a relatively low yield procedure. In a large study of 3170 patients only 2.2% had seizures with HV. There was an increase in inter-ictal epileptiform activity not seen the resting records in 3.0% of the studies. Of the seizures incurred 78% were absences, although 54% of these patients also had spontaneous absences in the resting record (14). The second study had a smaller cohort (1084) but similar findings but against a 5 min HV period. Inter-ictal HV only discharges were at 1.8% at a 3 minutes duration period. The paediatric cohort again had an expected increased incidence of provoked absence but very little increase in inter-ictal discharges not seen in the resting record at 0.6% (15).
Prominent international neurophysiological bodies (16, 17, 18), currently recommend that anybody who is a known Covid-19 positive patient should not be hyperventilated. The UK mandated that HV should be suspended during the Covid outbreak with the exception of in the investigation of childhood absence epilepsy. During high-risk periods we need to account for patients who are untested and may be asymptomatic or pre-symptomatic for Covid-19. When significant risk is present in the community caution should therefore be in place and the risk rewards of performing HV should be balanced.
Testing Duration
In Victoria 3561 health care workers acquired COVID-19, 73% were acquired in a health care setting; 50% were aged or disability workers, 40% nurses and 4.8% medical practitioners. Those most at risk are clearly those most in close regular contact with unwell patients attending to their daily care, not those performing aerosolising procedures (7). In one study, 14/41 (63.6%) of occupational infections occurred in health workers using a surgical mask, while no occupational infections were found while using aerosol precautions when treating suspected or confirmed COVID-19 patients (19). We have evidence that Covid-19 remains aerosolised and viable for up to 3 hours and can travel in excess of the arbitrary 2m safety range previously stated (1, 2). Fleeting transmission of the more recent variants, in particularly delta, mandate that any time spent with a Covid-19+ patient is a risk and full PPE (N95, eye protection, gown and gloves) should be used. Test duration should be kept to a minimum during higher risk periods utilising a modified 10/20 placement.
Discussion and guidance
A lot of arguments were made initially that aerosolisation was not a risk for healthcare workers. Risks and precautions around Covid-19 and PPE requirements continue to be misrepresented by the Australian Government Department of Health. HV has been argued by some neurologists not to be an aerosolising procedure and Paediatric patients were framed initially as little to no risk as a vector for transmission.
Whilst the vaccination of the community decreases risks it does not abolish the risk of asymptomatic/pre-symptomatic onward transmission. This not only places us at some risk but also carries risk for nosocomial transmission as well as putting the outside community and our loved ones at risk. Reducing the number of staff and family members involved in a test is key. One person should perform testing only unless help is absolutely necessary. This will help reduce exposure of staff and onward infections to others. It is also important to remember that there will always remain a significant proportion of the population for whom the vaccine is not as effective placing them at a higher risk to serious symptoms and death.
There would appear to be no safe period or distance to be in a room with a Covid-19 positive patient unless we have adequate PPE. This raises questions of safety during outbreaks in community with all patient testing due to the potential for asymptomatic and pre-symptomatic patients.
Whilst hyperventilation (HV) is a useful addition to the normal EEG test the safety of this needs to measured against the risk in the community. It is a relatively low yield procedure with the exception patients with childhood absence epilepsy. Performing HV with the patient masked is also unhelpful as it reduces hypocapnia and renders the procedure unhelpful. Leaving the room whilst the patient hyperventilates and then returning carries a greatly increased risk from aerosol infection, it also places the patient at risk from delayed seizure management due to increased response time. There is general consensus that hyperventilation should never be performed on a Covid-19 positive patient and that it should be restricted during major outbreaks.
The argument that the Paediatric population poses no risk for Covid-19 infection and transmission is no longer a valid one. Again when community transmission is high caution should be in place for hyperventilation in this group of patients. These patients should be treated with the same level of risk as the general community during large outbreaks.
Infection control protocols remain a key defense and disposable electrodes are useful during high-risk periods for mitigating risk of onward transmission and are always preferable in Covid-19+ patients.
It would be useful to define periods of high risk for outbreaks. This currently could be conceived as periods of lockdown within a state although as we move forwards and open up as a country this would need a new way of being defined.
It is clear that this pandemic has a long way to run and even with high vaccination rates in the community the onward transmission amongst the vaccinated will remain a problem. We need to keep across emerging scientific data and be prepared to change and flex in our clinical practices. It is our duty as healthcare workers to mitigate that risk to keep nosocomial spread as low as possible and reduce the risk to the wider community.
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;382(16):1564-7.
Bahl P, Doolan C, de Silva C, Chughtai AA, Bourouiba L, MacIntyre CR. Airborne or Droplet Precautions for Health Workers Treating Coronavirus Disease 2019? J Infect Dis. 2020.
El-Boghdadly K, Wong DJN, Owen R, Neuman MD, Pocock S, Carlisle JB, et al. Risks to healthcare workers following tracheal intubation of patients with COVID-19: a prospective international multicentre cohort study. Anaesthesia. 2020;75(11):1437-47.
Chu DK, Akl EA, Duda S, Solo K, Yaacoub S, Schünemann HJ. Physical distancing, face masks, and eye protection to prevent person-to-person transmission of SARS-CoV-2 and COVID-19: a systematic review and meta-analysis. Lancet. 2020;395(10242):1973-87. doi: 10.1016
Nguyen LH, Drew DA, Graham MS, Joshi AD, Guo CG, Ma W, et al. Risk of COVID-19 among front-line health-care workers and the general community: a prospective cohort study. Lancet Public Health. 2020
Chotirmall SH, Wang L-F, Abisheganaden JA. Letter from Singapore: The clinical and research response to COVID-19. Respirology. 2020 Oct;25(10):1101-1102.
Peter AB Wark, C Raina MacIntyre, Scott Bell, Brian Oliver and Guy B Marks We are not doing enough to prevent the spread of COVID-19 and other respiratory viruses in Australian hospitals Med J Aust
Published online: 10 June 2021Steven Riley,*, Haowei Wang, Oliver Eales, David Haw, Caroline E. Walters, Kylie E. C. Ainslie, Christina Atchison, Claudio Fronterre, Peter J. Diggle, Andrew J. Page, Sophie J. Prosolek, Alexander J. Trotter, Thanh Le Viet, Nabil-Fareed Alikhan, Leigh M Jackson, Catherine Ludden, The COVID-19 Genomics UK (COG-UK) Consortium, Deborah Ashby,Christl A. Donnelly, Graham Cooke, Wendy Barclay, Helen Ward, Ara Darzi, Paul Elliott REACT-1 round 12 report: resurgence of SARS-CoV-2 infections in England associated with increased frequency of the Delta variant https://spiral.imperial.ac.uk/bitstream/10044/1/89629/10/react1_r12_preprint_final.pdf online July 2021
Ross J Harris1; Jennifer A Hall2,3; Asad Zaidi2; Nick J Andrews1; J Kevin Dunbar2*; Gavin Dabrera2* Impact of vaccination on household transmission of SARS-COV-2 in England https://khub.net/documents/135939561/390853656/Impact+of+vaccination+on+household+transmission+of+SARS-COV-2+in+England.pdf/35bf4bb1-6ade-d3eb-a39e-9c9b25a8122a?t=1619601878136 online July 2021
Matan Levine-Tiefenbrun, Idan Yelin , Rachel Katz, Esma Herzel, Ziv Golan, Licita Schreiber, Tamar Wolf, Varda Nadler, Amir Ben-Tov, Jacob Kuint, Sivan Gazit, Tal Patalon, Gabriel Chodick and Roy Kishony Initial report of decreased SARS-CoV-2 viral load after inoculation with the BNT162b2 vaccine Nature , May 2021,Vol 27, 790–792
Sharifa Nasreen PhD, Siyi He MSc, Hannah Chung MPH, Kevin A. Brown PhD, Jonathan B. Gubbay MD MSc, Sarah A. Buchan PhD, Sarah E. Wilson MD MSc, Maria E. Sundaram PhD, Deshayne B. Fell PhD, Branson Chen MSc, Andrew Calzavara MSc, Peter C. Austin PhD, Kevin L. Schwartz MD MSc, Mina Tadrous PharmD PhD, Kumanan Wilson MD MSc, and Jeffrey C. Kwong MD MSc Effectiveness of COVID-19 vaccines against variants of concern, Canada https://www.medrxiv.org/content/10.1101/2021.06.28.21259420v1.full.pdf Online July 2021
Li Tang, PhD1; Diego R. Hijano, MD, MSc2; Aditya H. Gaur, MD, MBBS2; et al Asymptomatic and Symptomatic SARS-CoV-2 Infections After BNT162b2 Vaccination in a Routinely Screened Workforce JAMA. 2021;325(24):2500-2502. doi:10.1001/jama.2021.6564
NickKanea1LesleyGrocottb1RosKandlerc1SarahLawrencec1CatherinePang Hyperventilation during electroencephalography: Safety and efficacy, Seizure Volume 23, Issue 2, February 2014, Pages 129-134
Edina Timea,VargaIoana Mindruta,Pirgit Meritam, Zoltan Horvath, Daniella Terney, Elena Gardella, Jørgen Alving, Laszlo Vecsei, Sandor Beniczky Diagnostic yield of five minutes compared to three minutes hyperventilation during electroencephalography, Seizure, Volume 30, P90-92, August 01, 2015
Appendino JP, Baker S, Chapman KM, et al. Practice guidelines for Canadian neurophysiology laboratories during the COVID-19 pandemic. Can J Neurol Sci. 2020;48(1):25–30.
Oksanen L-MAH, Sanmark E, Oksanen S, Anttila V-J, Paterno JJ, Lappalainen M, et al. Healthcare workers high COVID-19 infection rate: the source of infections and potential for respirators and surgical masks to reduce occupational infections. medRxiv. 2020:2020.08.17.20176842.
Written by Mark Edmonds
Faculty of Medicine and Health, The University of Sydney