Impact of SARS-Cov2 on Endoscopic Trans-Nasal Skull Base Surgeries
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.287683
Source of Support: None, Conflict of Interest: None
Keywords: Algorithm, COVID-19, personal protection equipment, skull base surgeryKey Message: In all emergency patients skull-based surgeries, to consider transcranial surgery or a sub-labial approach avoiding exposure to mucosa. It is preferable to avoid use of powered drills. However, cold procedures involving shavers and microdebriders generate lesser amounts of aerosol.
The COVID-19 pandemic is currently an evolving situation. Attrition of hospital personnel due to infection can be extremely devastating and undesirable among the provider team and society as a whole. An increase in the number of people infected with SARS-CoV2 escalates there may also be a proportional increase in a number of asymptomatic carriers but with a negative SARS-CoV2 negative test. With limited to low number of tests across the world, these asymptomatic carriers will inevitably appear in hospitals and pose a risk to other patients and health care workers. Therefore, early identification of both infected people and asymptomatic carriers becomes a natural priority. A comprehensive understanding of the aerosolization risks will help develop protection strategies. Reportedly, viral shedding is higher in the upper respiratory tract, and as aerosols, the virus particles remain airborne for more than three hours., More importantly, there is a high degree of uncertainty whether COVID-19 can behave as an airborne pathogen and transmit the infection through these potential aerosols.
Operating rooms (OR) are high risk areas for the transmission of any respiratory infection given the fact that multiple personnel are involved, often in close proximity. More often than not, patients requiring emergency/urgent surgery but with high-risk or unknown status of SARS-CoV-2 infection may present to the hospital. Of concern to neurosurgeons is the high risk of some aerosol generating procedures (AGPs) such as transsphenoidal and endonasal surgery. Endonasal AGPs theoretically present a higher risk of viral exposure due to the longer duration of exposure and aggressive disruption of potentially virus-containing mucosa. Common high-risk AGPs in include endoscopic endonasal pituitary surgery as well as anterior skull base procedures.
Early reports from China showed staggering number of transmission to many operating room (OR) personnel, particularly after transsphenoidal surgery in COVID-positive patients. This resulted in limiting pituitary surgery and other skull base surgeries to emergency cases where vision is compromised by chiasmal compression. However, in emergency situations patient care must proceed, but with an abundance of safety precautions and caution. Encouragingly, with strict precautions, the reported rates of infection among fully equipped healthcare workers are negligible.
Effective response to any health disaster is often summarized as “staff, stuff (medical/surgery supplies), space (ORs), and systems (support system).” A desirable algorithm for patients who require neurosurgery should be able to assess the patients' potential risk of infecting others, appropriate personal protective equipment (PPE), and perhaps a hint at post-surgical management. This algorithm could be crucial not only to adequately protect the hospital staff, but also effective and balanced utilization of PPE. The current review discusses potential strategies to Neuro-surgeons to avoid transmission of COVID 19 during endo-nasal and trans-sphenoidal surgeries.
Prior to surgery and admission, thermal screening and a comprehensive screening questionnaire is now mandatory to be administered in various hospitals. Additionally, a review list of symptoms and exposure history is also helping to identify patients who may be potentially infected. The questionnaire also includes details to enquire if the patient is from any of the government designated containment or red zones.
Currently, the decision of scheduling a surgery is influenced by two variables.:
So, the most important question for the neuro-surgeon is: “Can this patient safely wait for things to return to normal without incurring further neurological deficit and/or progression of disease?” If the answer is “yes”, the surgeon can defer the surgery for four weeks and follow-up with clinical symptoms, symptomatic management with medications or radiation therapy and probably investigations. If the answer is “no”, then the surgeon should navigate the system and perform the surgery done in a timely manner.
In all emergency or urgent patients, it is preferable to consider transcranial surgery or a sub-labial approach avoiding exposure to mucosa, for all the cases, ordinarily done by trans-sphenoid approach. Furthermore, it is desirable that all patients who require elective high-risk neuro-surgery (defined as surgery that transgresses the upper airways) should undergo a routine preoperative swab for COVID-19 the day before surgery. The time of the testing before an emergency procedure is often dependent on how long it takes to obtain the results. Importantly, during the duration between the patient is tested for COVID-19 and obtaining the results, the patient should remain isolated until the procedure. Preferably, surgery for those who test positive for COVID-19 should be postponed until test results are negative.
However, due to laboratory constraints in the face of the extremely large number of suspect cases, the capacity for routine swabs or multiple testing is not always available. Fang et al. have reported findings of pneumonia on computed tomography (CT) chest in 50 out of 51 patients with RT-PCR–proven COVID-19. Ai et al. reported similar findings in a larger study population where the CT findings of pneumonia were observed in 580 of 601 patients with RT-PCR–proven COVID-19. The authors further added that that chest CT may be used as a primary tool for detecting COVID-19 in epidemic areas. Since multiple testing is not always possible, routine preoperative screening CT chest may be performed in all patients, and any suspicious findings are discussed with a dedicated on-call COVID-19 Infectious Disease team and the suspected patient is shifted to isolation ward with the surgery postponed till a swab test is done. However, symptomatic treatment is continued under the supervision of the neurosurgeon. [Table 1] summarizes a proposed stratification of potential risk for others. A no-risk classification is deliberately avoided due to uncertainty of prevalence of asymptomatic carriers. In out-patient department (OPD), all consults as possible and preferable should be done as tele-medicine both for new patients and during post-surgical follow-up.
In hospitals across the globe, most neurosurgical supplies have a long shelf life and are already on-site, therefore, hoarding is not required. The most important exception is PPE, especially the supply of N95 masks. However, recommendations allow wearing each N95 mask for more than one patient. Importantly, a regular surgical mask should be worn over the N95 to avoid droplet soiling. Supplies of standard OR gowns, gloves is not immediately threatened. Task Force of the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS) recommends that COVID-19 status and the risk of aerosolization caused by the intervention should determine the appropriate level of PPE required. For patients who are known to be infected with COVID-19, maximal available and appropriate PPE should be used during all “levels of interaction”. However, given the variable false negative rate of testing and the presence of asymptomatic carriers, a conservative approach should be preferred to determine the appropriate PPE. Importantly, procedures that manipulate the mucous membranes of the respiratory tract have a high risk of aerosol transmission should be performed with great caution.
[Table 2] summarizes the judicial use of PPEs for the various risk groups summarized in [Table 1], which could also be utilized in out-patients departments/clinics. Resources and the clinical situation.
Space/operating room (OR)
The “space” comprises of ORs, ICU and inpatient beds. The OR should have an independent air flow/condition system with preferably a laminar air-flow. It is advisable that the ORs are equipped powered air-purifying respirator (PAPR) units and HEPA filters at least. Furthermore, negative-pressure rooms or antechambers may be required in varying combinations. Surgical procedures that require a microscope are particularly challenging as it would be difficult to use microscope/transition glasses while wearing a PAPR.
Pre-operative phase & intubation
While preparing for surgery, to reduce viral load, all patients should be prepared with povidone-iodine (PVP-I) solution nasal irrigations and oral wash. All intubations should be treated with precautions; it is advised to include a period allowing exchange of air in the OR before other non-anesthesia personnel enter. The predominant mode of transmission of COVID-19 has been inhalation of infected aerosols or by exposure to contaminated surfaces. Since the detection of the virus in the blood has been very infrequent. The priority systems to avoid infection of HCWs includes justified use of appropriate PPE, equipment and surface decontamination and managing patients in “single” preferably negative pressure rooms. Therefore, a period of air exchange between intubation and entry of non-anesthesia personnel is very important.
Intra-operative phase & instrumentation
Once a patient tests “negative for COVID/low risk of transmission of infection”, consensus from Infectious Disease experts suggest that for AGPs, in these patients, a properly fitted, molded, and handled N95 mask; eye protection (goggles/full face shield); and standard PPE (gown and gloves) should be adequate. Preferably the surgery should be done within 48 to 72 hours after a negative COVID-test.
In all “COVID-19 positive patients”, where the surgery cannot be differed (severe trauma, bleeding, infections, malignant tumors) and where a waiting time might be fatal, urgent or emergency procedures should be performed. Anecdotal/informal in Europe, UK and US advisories have recommended a cautious stance and suggest to preferably use trans-cranial approach. Moreover, in addition to extended PPE [Table 2], the use of powered, air-purifying respirators (PAPRs) for all operating room staff is recommended. David A.P. et al., have reported the use of Negative-Pressure Otolaryngology Viral Isolation Drape (NOVID) system to reduce the risk of aerosol. As reported by the authors, “NOVID consists of a plastic drape suspended above the patient's head and surgical field with a smoke evacuator suction placed inside the chamber”. To evaluate the efficiency of NOVID, fluorescein was applied to the operative field, the authors revealed minimal contamination distant to the surgical field. The study further revealed that “instruments and cottonoids appeared to be a greater contributor to field contamination”.
In fact, Workman A D et al., report that “the aerosol generation risk, particle size, and transmission distance are entirely a function of the instrumentation utilized”. The authors suggest that the instruments could be categorized into thermal and cold procedures. Cold procedures may be further divided into powered and non-powered. The authors further suggest that cold non-powered endonasal procedures and cold surgical instruments (shavers/microdebriders) exhibit a lower risk of aerosol generation, whereas the use of powered instrumentation does create high airflow velocities and are of concern. Therefore, intra-operative, use of power instruments should be avoided as much as possible, of course without compromising the surgical exposure. Therefore, the usage of rongeurs and chisels instead of power equipment is advised, despite an increase in the duration of the procedure. For procedures that require headlight and loupes, models of PAPR such as the CleanSpace HALO may be used.
Use of personal protective measures in patients whose “COVID-19 status is unknown”: This group includes patients with symptoms of COVID 19 but no changes on CT Chest or vice-versa and where a COVID-19 confirmation test is not possible due to logistic reasons, categorized as high risk for transmission of infection.
Neurosurgery and requirement/extent of protection during surgery in this group of patients, has often generated more debate, especially due to limited availability of various PPEs. However, the safety of surgeons and the OR team should be the highest priority, therefore an extended PPE [Table 2] should be preferred for all the OR staff. If possible, elective endonasal surgeries and trans-sphenoidal surgeries and other AGPs should be deferred by at least 14 days, while observing for a clinical status of the patient. All patients in this group who require emergency surgery should be assumed to be COVID-19–positive until proven otherwise.
In all lateral skull-based surgeries should also be considered as AGPs as mastoid drilling creates droplets and aerosolization of particles. Therefore, extended PPE [Table 2] are desirable for OR personnel. Additionally, after the mastoid and middle ear is open, it is preferable to apply topical PVP-I solution to reduce the mucosal viral load.
Between and after surgeries.
It is vital to avoid over-loading the OR with increased number of cases or extended cases. The following steps should be employed between surgeries.
It is advised to avoid the use of nasal packing or pledgets, because when these are removed in the postoperative phase, it may induce coughing or gagging. When used, nasal packing/pledgets should be removed under safety precautions, [Figure 1] and PPEs as suggested in [Table 2]. Bhangu et al., through COVID surg collaborative, analyzed 30-day mortality and pulmonary complications in 1128 patients who tested positive for COVID-19 during peri-operative period. The authors report that “postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. The authors further add their findings of overall 30-day mortality in 23.8% patients and were high across all patient subgroups. The authors further report that their findings are similar with the 2019 NELA report of 30-day mortality rates, where frail patients older than 70 years had 23.4% mortality. However, the 30-day mortality rates identified Bhangu et al., are higher than a 30-day mortality of 14·9% in the high-risk patients who had emergency midline laparotomy. Interestingly, Post-operative mortality rates in SARS-CoV-2-infected patients with post-operative pulmonary complications, reported by Bhangu et al., are similar to those of the sickest patients with community-acquired COVID-19 who are admitted to intensive care. Therefore, further research could help identify if the SARS-CoV-2 pathology/severity determines the mortality, irrespective of surgery. Importantly, the surgeon should aim to reduce the post-operative hospital stay to optimal possible, in an effort to avoid post-surgical pulmonary complications (either ventilator associated or nosocomial).
After discharge facilities such as surgical ICUs and in-patient wards may have other patients admitted. Moreover, rehabilitation set-ups may also be under pressure, therefore early return to home should be planned. A summary of the suggestions of this manuscript is summarized in the flow-chart, [Figure 2].
During the current SARS-CoV-2 pandemic, endonasal procedures carry a risk of infectious aerosolization of viral particles. Endoscopic skull-based surgeries are intrinsically aerosol generating procedures. Although deferral of surgery with continuous symptomatic treatment is desirable; in emergency situations, a trans-cranial approach should be opted for. In all endo-nasal surgeries, Negative-Pressure Otolaryngology Viral Isolation Drape (NOVID) may reduce the exposure of the surgical team to viral particulate. However, surgeons should continue to wear PPE despite the potential benefits of barrier methods. Use of a high-speed surgical drill should be avoided as they are associated with high volumes of aerosol, even for short intervals.
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There are no conflicts of interest.
[Figure 1], [Figure 2]
[Table 1], [Table 2]