COVID-19 and Anesthesia Machines and Equipment Maintenance
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1. How do we clean and sterilize laryngoscope/GlidescopeTM blades?
- We do not have guidance on individual laryngoscope processing or high-level disinfection processes. To our knowledge, none of the four major U.S. manufacturers of disposable videolaryngoscope blades (covers) recommend cleaning or sterilization of their disposables for reuse. However, a number of U.S. medical centers are using various techniques to process and reuse these covers.
- ASA and APSF both recommend the use of videolaryngoscopes instead of typical laryngoscopes in an effort to limit exposure for operating room and anesthesia personnel.
Below are several examples of techniques used by medical centers to process blades for re-use. Neither ASA nor APSF endorse any specific company or technique. These examples are provided only for information:
- Some medical centers use techniques commonly used to clean endoscopes. This equipment type can be thought of as a super medical dishwasher. A number of centers that have used this technique have reported that they have not seen damage to any of their disposable blades.
- Some medical centers use vaporized hydrogen peroxide. This is a low temperature sterilization process. A number of centers that have used this process also have reported no damage to any of the disposable blades.
- Some medical centers use manual cleaning and autoclaves and have reported that they have not seen damage to their disposable blades.
- To conserve videolaryngoscopy equipment, remember that routine equipment can be used with patients with Mallampati Class 1 and 2 airways. Regardless, please refer to CDC and FDA regulations regarding the reuse of single-use medical devices.
We also recommend that you contact the manufacturer for cleaning guidance in the face of shortages. You may also wish to review recommendations on Infection Prevention in the Operating Room Anesthesia Work Area from the Society for Healthcare Epidemiology of America (SHEA) for consideration.
2. What type of breathing circuit filters should be used to prevent passage of the COVID-19 virus into the anesthesia machine? Could breathing circuit filters become a vector for subsequent patients?
With regard to this question, the ASA recommendations coincide with APSF guidance on filters.
- Place a breathing system filter or HME filter between the Y-piece and the patient’s airway. Attach the gas sampling line (for respiratory gas analysis) to the machine side of the filter. In addition, place a second breathing system filter at the end of the expiratory hose where it connects to the breathing system.
For example, please see the photos below.
Preferred Filter Configuration
VFE > 99.99% for each filter. Gas sampling on machine side of filter. (Courtesy Draeger Medical)
- To our knowledge, all breathing system filters are rated with a viral filtration efficiency (VFE) of at least 99.99%. Some have a VFE of 99.9999% or better. The VFE of a specific breathing circuit filter is listed in the manufacture’s specifications.
- There are no data testing the efficacy of breathing system filters for preventing transmission COVID-19 to the anesthesia machine. All breathing system filters decrease viral transmission, but we do not know the minimum performance specification that will be protective.
- A filter placed between the Y-piece and the patient’s airway adds to respiratory dead space; smaller patients may not tolerate the additional dead space volume. The dead space of a breathing system filter is generally a concern for patients whose tidal volume is less than 300 mL (i.e. patients weighing under 50 kg). The internal volume of the breathing system filter, listed in the manufacturer’s specifications, indicates the additional dead space for a given filter. A rule of thumb is to consider three times the internal volume of the device as the minimum tidal volume. If a filter cannot be placed between the Y-piece and the patient’s airway, then place a viral filter where the inspiratory hose attaches to the breathing system, in addition to the one at the expiratory hose connection to the breathing system. In this situation, also consider the filtration of sampled gas:
- If the gas analyzer returns sampled gas to the breathing circuit, then the sampled gas needs to be filtered. Water traps have built in filters and the viral filtration efficiency (VFE) determines the effectiveness. The GE DFend Pro water traps include a 0.2 micron filter with a VFE of 99.999%. The Draeger Watertrap 2 uses a 0.2 micron filter with a VFE of 99.99981%. If the water trap filter VFE cannot be confirmed, a 0.2 micron drug injection filter similar to that used in epidural kits can be placed at the water trap and used between patients after wiping the surface.
- If the gas analyzer returns sampled gas to the scavenging system, additional filtration may not be necessary as there are standards for managing biohazards in the central suction system or waste anesthetic gas system (WAGS). Check with the local facilities manager to confirm the risk of biohazard in the suction system.
- Unfiltered sampled gas should not be exhausted directly into the OR environment or a passive scavenging system.
- We recommend that the breathing system filter placed between the Y-piece and the patient’s airway be discarded after each patient use. Change the filter(s) at the end of the expiratory limb of inspiratory limb as frequently as supplies allow and in accordance with the manufacturer’s recommendations. If re-used between patients, wipe the external surface of the filter with an EPA-approved disinfectant between patients.
3. Does the anesthesia machine need to be decontaminated after use on a COVID-19 patient? We have breathing circuit filters in the circuit and the gas sampling line is also filtered.
4. Where can I find information on converting anesthesia machines to ICU ventilators?
- If the pandemic overcomes the capacity of the hospital ICUs to provide ventilators, unused operating room anesthesia machines can be purposed for use in the ICUs. Please refer to ASA and APSF guidance for further information. Anesthesia machine manufacturers have also provided their recommendations on repurposing the anesthesia machine for ICU use.
5. Where in the anesthesia circuit should we place the breathing circuit filter to protect the gas sampling tubing?
- The gas sampling line should be protected by placing a breathing circuit filter at patient end after the Y-piece and then sampling from the side of the filter opposite to the patient (from the machine side of the filter). If there is a sampling port on the patient side, it must be capped. Ensure that the gas sampling line is protected from gases expired from the patient by placing it on the machine side of the filter.
- If a filter cannot be placed between the breathing circuit and the patient’s airway and if the gas sampling system does not have an effective viral filter prior to exhausting sampled gases back into ambient air or into the internal conduits of the anesthesia machine, then place a 0.2 micron filter at the entry to the water trap. This is the same filter that is typically placed in an epidural tray for filtering epidural injections.
- New information from GE is that the D-Fend water trap also contains a 99.999% viral filtration efficiency filter. Draeger is conducting tests on the efficiency of their gas analyzer filter, but it will work with an added 0.2 micron drug injection filter. Wipe surface of the drug filter if not changed between patients. Change the filter and water trap after use on a COVID-19 patient.
- Some capnometers and gas analyzers, especially those used in non-operating room settings, transfer the output gas back into the room. Multi-gas analyzers, typically used with or integrated into anesthesia machines, transfer the output gas back into the anesthesia machine into the scavenging system. It is especially important to filter the analyzer gas if the effluent is discharged either into the room or back into the breathing system.
6. For the pediatric patient how do you protect the sampling line due to the fact the breathing circuit filter adds dead space and is too heavy for ETT?
- A filter placed between the breathing circuit and the patient’s airway adds to respiratory dead space; smaller patients may not tolerate the additional dead space volume. If a filter cannot be placed between the breathing circuit and the patient’s airway, then place a viral filter at the end of the expiratory limb at the connection to the anesthesia machine. If the gas sampling system does not have an effective viral filter prior to exhausting sampled gases back into ambient air, then place a 0.2 micron filter at the entry to the water trap. This is the same filter that is typically placed in an epidural tray for filtering epidural injections. Wipe surface of the drug filter if not changed between patients. Change the filter and water trap after use on a COVID-19 patient.
New information from GE is that the D-Fend water trap also contains a 99.999% viral filtration efficiency filter. Draeger is conducting tests on the efficiency of their gas analyzer filter, but it will work with an added 0.2 micron drug injection filter.
- The dead space of a viral circuit filter is generally a concern for patients whose tidal volume is less than 300 mL (i.e. patients weighing under 50 kg). The internal volume of the circuit filter, listed in the manufacturer’s specifications, indicates the additional dead space for a given filter. A rule of thumb is to consider three times the internal volume of the device as the minimum tidal volume.
- We recommend you review the APSF website for more information on this topic.
7. Where can I purchase breathing circuit filters? Does ASA or APSF have any specific product recommendations?
- Hospitals have supply chain managers who generally have established relationships with the contracted suppliers because breathing circuit filters are commonly used on ICU ventilators and anesthesia machines. Anesthesia supply businesses are a second option. When buying breathing circuit filters, obtain those with the highest VRE. Purchase some with smaller internal volume if your practice includes pediatrics. We cannot recommend specific products to purchase.
8. We are using breathing circuit filters that filter 99.9999%. We also have HMEF filters that filter even more. Which filters should I use?
- Depending on the presence and level of community spread of COVID-19 in your area and levels of current supplies will help you determine how to best allocate scarce resources. Reserving the higher filtration breathing circuit filters for the patients with the highest viral titers seems appropriate. Note that a filter may have different filtering capabilities for different pathogens. Please also consult with your local infectious disease physicians and infection control staff. We also recommend you review the APSF website for a discussion on anesthesia machines.
9. Should we use breathing circuits for all general anesthetics since we may not conclusively know which patients are COVID-19+ or contagious?
- Breathing circuit filters or combined heat and moisture exchange filters (HMEF) are already commonly used for all general anesthetics. This is best practice that should be adopted as standard policy in all practice locations now. The filters are VFE rated, and we recommend, at a minimum, filters with a VFE of 99.99% that are already commonly being used.
10. Should I be concerned that my anesthesia machine is a vector for transmission?
11. What is the position of the ASA on placing multiple patients on a single mechanical ventilator?
- ASA, the Society of Critical Care Medicine (SCCM), American Association for Respiratory Care (AARC), Anesthesia Patient Safety Foundation (APSF), American Association of Critical‐Care Nurses (AACN) and American College of Chest Physicians (CHEST) issued a consensus statement on the concept of placing multiple patients on a single mechanical ventilator on March 26.
12. For asymptomatic and negative COVID-19 patients, do we need to protect the CO2 sampling line with a second HEPA filter for each general anesthesia case?
- Guidance on the approach to filtering airway gases is available on the APSF website. Current guidance recommends using an HME filter at the airway and sampling gas from the machine (filtered) side of the HMEF. The viral filtration effectiveness varies with HMEFs and filtering performance at the airway as susceptible to moisture or soiling, especially for electrostatic filters. Sampled gas typically enters a water trap and many of these traps have an internal filter effective for filtering viruses. Some traps do not and the viral filtration effectiveness is not documented for many. The level of additional protection recommended for the sampling line, in addition to the HMEF, depends upon where the exhaust gas from the gas analyzer is routed.
If the analyzer is separate from the anesthesia machine, a second filter is not required if the exhaust port for sampled gas is connected directly to a scavenging system or central suction. It is not recommended for exhaust gas to enter the room directly since inhalation anesthetics will also contaminate the room. If scavenging cannot be accomplished, additional filtering is prudent to protect against viral infection.
- If the analyzer is built into the anesthesia machine, it is important to understand if the exhaust gas from the analyzer goes to the scavenger, back into the circuit or into the room. If exhaust gas is routed into the breathing circuit and the effectiveness of the water trap filter for virus is unknown, additional filtering is prudent to prevent contaminating the inside of the anesthesia machine. It is not recommended for exhaust gas to enter the room directly since inhalation anesthetics will also contaminate the room. If scavenging cannot be accomplished, additional filtering is prudent to protect against viral infection.
13. What processes should I use to return an anesthesia machine that was purposed for ICU back to an operating room setting? If a machine is not used for a month or so, do we need to do any special testing prior to routine anesthesia service?
- Complete guidance on how to return an anesthesia machine to service in the operating room after use for long term ventilation of patients with COVID 9 related respiratory failure can be found in the APSF/ASA Guidance on Purposing Anesthesia Machines as ICU Ventilators.
- The current recommended steps are:
- Remove and discard all disposables - circuit, filters, CO2 absorbent, mask, sampling line and associated water trap.
- Following manufacturer instructions, sterilize the internal breathing system and ventilator components.
- Wipe external surfaces with appropriate anti-viral cleaning solution
- Replace the disposables with new clean/sterile replacements
- Place a viral filter on the inspiratory limb for two to four weeks. This filter could be left in place between patients to conserve supply.
- If the machine has not been used for more than a month, no special testing should be required other than the usual preventive maintenance and pre-use test procedures. It is not likely that viable virus would remain after that period of time.
- Please review the APSF website for a discussion on anesthesia machines.
Viewers of this material should review these FAQs with appropriate medical and legal counsel and make their own determinations as to relevance to their particular practice setting and compliance with state and federal laws and regulations. The ASA has used its best efforts to provide accurate information. However, this material is provided only for informational purposes and does not constitute medical or legal advice. This response also should not be construed as representing ASA policy (unless otherwise stated), making clinical recommendations, dictating payment policy, or substituting for the judgment of a physician and consultation with independent legal counsel.