“Thoracic anesthesia in patients with airborne disease”

Abstract

Health care workers are at risk of infection from aerosolization of respiratory secretions, droplet and contact spread. This has gained great importance after the COVID19 pandemic.

Intra-operative aerosol-generating procedures are arguably unavoidable in the routine provision of thoracic anesthesia. Airway management for such patients during the COVID-19 pandemic including tracheal intubation, lung isolation, one-lung ventilation and flexible bronchoscopy may pose a significant risk to healthcare professionals and patients.

The thoracic anesthetic community has been confronted with the need to modify existing techniques to maximize safety for patients and healthcare professionals.

1 Main text

Respiratory infections are thought to be spread via three main mechanisms: droplets, contact (direct and indirect) and airborne [ , , , , ].

Droplet spread refers to relatively large droplets ejected from an infected patient’s mouth, nose or trachea that are transmitted directly to the recipient’s mouth or nose. These larger droplets do not persist in the air and rapidly land on surfaces, causing contamination.

Contact spread can be direct (such as hand-to-hand contact) or indirect, which refers to contact with surfaces contaminated with respiratory droplets, known as fomites. These can be picked up (usually by the hands), and self-inoculation can occur via the nose or mouth.

Airborne spread refers to inhalation of smaller respiratory particles that are light enough to remain ‘suspended’ in the air and are hence able to be inhaled directly into the recipient’s respiratory tract.

Coronavirus disease 2019 (COVID-19) has changed the way we practice medicine worldwide. The specialty of anesthesia and, in particular, thoracic anesthesia has faced major challenges during the crisis due to the frequent necessity to perform aerosol-generating procedures that pose significant risk of viral transmission.

It should be emphasized that both the management of the infected patient with COVID-19 and the self-protection of the anesthesia team constitute a complicated challenge [ ].

The text focuses therefore on both important topics.

1.1 Aerosol-generating procedures

Aerosol-generating procedures during anesthesia for thoracic surgery are not limited to intubation and extubation, but may occur throughout the surgery. These include, but are not limited to, bronchial blocker (BB) insertion, endotracheal intubation with double-lumen tubes (DLT), and bronchoscopy, which are required to provide adequate operating conditions and one-lung ventilation (OLV) [ ].

In the management of all COVID-19 patients undergoing anesthesia, it is widely acknowledged that the minimum number of staff should be present in theatre during intubation and other aerosol generating procedures (AGPs) and that these should be performed by the most experienced operator to maximize efficiency and minimize aerosol generation [ , ]. This applies even more so in the practice of thoracic anesthesia as correct placement of lung isolating airway devices and the use of bronchoscopy and one lung ventilation are highly technical skills, best performed by an anesthetist familiar with thoracic surgery. Disposable equipment should be used where possible, and detailed team briefings should be held with a focus on AGP management.

Many endorsed techniques to reduce aerosol generation during induction of general anesthesia and intubation also apply to thoracic patients: thorough preoxygenation, avoidance of high gas flows, avoidance of manual facemask ventilation, use of two-handed face mask technique when necessary, rapid sequence induction, ensuring complete neuromuscular blockade prior to airway instrumentation, use of videolaryngoscopy, and tracheal tube cuff inflation prior to ventilation [ , , ].

A survey of clinicians from Spanish Society of Anesthesiology who were involved in tracheal intubations in patients with suspected or confirmed COVID-19 infection showed that the preferred airway device was video laryngoscope with remote monitor and disposable Macintosh blade, using the Frova guide. Most participants worked in public hospitals and were anesthesiologists. The survey also highlighted variations in clinical practice of senior doctors differed from younger physicians in the type of video-laryngoscope used, the number of experts involved in tracheal intubation and the reason that caused more stress during the airway management [ ].

Several guidelines on difficult airway (DA) management have been published5, but recommendations differ when treating COVID-19 patients; awake intubation in a patient meeting DA criteria should be avoided and reserved solely for non-deferrable or emergency surgery. Administer mild intravenous sedation and avoid topical analgesics. If 3 attempts at intubation are unsuccessful in a patient with unanticipated DA, secure the airway with a 3rd generation supraglottic device and then perform intubation with a fibreopticbronchoscope (FOB) [ ].

1.2 Lung isolation

Lung isolation enables each lung to be ventilated independently.

The primary function in thoracic surgery is to facilitate deflation of the operative lung and thereby maximize surgical exposure. The most widely used device for enabling lung isolation is a double lumen tube (DLT). Most published literature regarding lung isolation during the pandemic focuses on recommendations for DLT use [ , , ]. Other options include bronchial blockers and, rarely, single lumen tubes advanced into the bronchus of the non-operative lung.

The set of recommendations highlights the importance of attending anesthesiologist to be able to differentiate between lung separation and isolation. The absolute indications to lung isolation using DLT aim at preventing contamination of the healthy lung in case of abscess or hemorrhage, ventilating differentially both lungs in the event of giant emphysematous bullae or broncho-pleural fistulas, lung transplants or t carrying out any type of unilateral, pulmonary lavage or cleaning activities. Relative indications for the use of BBs or DLTs are applicable when improvement of the surgical exposure is required, as in upper lobectomy and lesser lung resection, thoracic aorta aneurysms, lung volume reduction or minimally invasive cardiac surgery ^15.

The advantage of using a DLT is that it can be checked by auscultation and observation of chest wall movements, while bronchial blocker (BB) requires the use of bronchoscope. The routine use of bronchoscope during COVID-19 outbreak is not advised and should be reserved to situations when there is necessity to open and manipulate the airway (like difficult airway management or tube misplacement). A disposable tool is preferred in case of bronchoscopy ^16.

Guidelines concur that it should only be performed; during gas flow cessation, patient apnea, without positive pressure in the circuit, and the adjustable pressure-limiting(APL) valve set at zero cmH2O.

Disposable single-use bronchoscope are preferred to multiuse bronchoscopes. Preoxygenation with 100% O2 ventilation for a few minutes to achieve the adequate anesthetic depth to prevent coughing. Nerve stimulator for neuromuscular block monitoring may be used. Cease ventilation before introducing the bronchoscope and finalizethe procedure during apnea if possible. Reduce the number of the insertions and removals. After removal, the scope must be cleaned and kept in a closed container until no longer required. After surgery, a disposable scope can be discarded.

Transthoracic ultrasound (US) has been proposed as a helpful method to confirm DLT placement. During OLV, a correct position of the DLT is confirmed on lung ultrasound with sign of adequate lung isolation (absence of “lung sliding” and presence of “lung pulse” on the side of surgery and presence of “lung sliding” on the opposite side) [ ].

The use of BB is recommended during postoperative ventilation to avoid catheter exchange and minimize airway manipulation [ ].

According to the survey on the lung separation tools preferably used by for COVID-19 patients, 52.4% would use only a bronchial blocker and 4.7% only a double-lumen tube. The remaining 47.6% chose to use a bronchial blocker or double-lumen tube according to the intubation status (intubated v nonintubated), airway difficulty, and duration of the surgical procedure. The use of bronchial blockers in all patients is advocated by 52.4%; 33.3% would use bronchial blockers in already intubated patients and 9.5% in patients with difficult airway. On the other hand, 28.6% would use double-lumen tubes in all cases and 19% only in nonintubated cases [ ].

We recommend that choosing the most suitable device for lung isolation during the pandemic should bepatient-specific and perhaps most importantly based on methods familiar to the anesthetist with adaptations to limit aerosol generation.

1.3 One-lung ventilation

One-lung ventilation is traditionally achieved by allowing the operative lung to passively deflate and release alveolar gas through an open lumen to the atmosphere whilst maintaining ventilation of the non-operative lung. Clearly, this method risks unacceptable aerosolization and contamination of the theatre environment. To mitigate this risk, all related guidelines recommend lung deflation through an anti-viral filter.

One-lung ventilation should be initiated prior to surgical incision to reduce the risk of lung parenchymal injury and resultant air leak. Application of suction to the operative lung to expedite collapse may be considered; however, it can generate unnecessary aerosols if an open-suction technique is used hence, some societies have advised against it [ , ].

High-efficiency particulate air (HEPA) filters are excellent in removing tiny diameter particulates and can effectively capture agglomerate of viruses and drops. HEPA filters should be applied between the mask and the breathing circuit and on the inspiratory and expiratory limbs of the breathing circuit ( Fig. 1 ).