This reservoir bag should be removed from its mount before using the machine when there is no central vacuum or waste anesthesia gas disposal. AGSS = anesthesia gas scavenging system. Photo by Dr. Loeb, used with permission.

This reservoir bag should be removed from its mount before using the machine when there is no central vacuum or waste anesthesia gas disposal. AGSS = anesthesia gas scavenging system. Photo by Dr. Loeb, used with permission.

You arrive on a Saturday for an urgent hip manipulation under general anesthesia when you notice a high-pitched, unfamiliar alarm and discover that the entire hospital lost central vacuum. You call the nursing supervisor and share that a lack of suction raises significant safety concerns for the anesthesia team. She reassures you that your ortho OR has stand-alone suction and that there are portable suction machines available for recovery. While that may solve the secretion/vomiting problem, you worry about the implications for the anesthesia machine. You contact the on-call biomedical technician who states that they usually outsource anesthesia machine maintenance and is unsure what it means.

So, what does it mean? What are the machine implications? Is it safe to proceed? Dr. Loeb and Sem Lampotang provide the following perspective:

It is safe to proceed with this hip manipulation under general anesthesia without central vacuum, but with two caveats. The first issue is to prevent or minimize release of waste inhaled anesthetics and nitrous oxide into the anesthetizing location. The second consideration is to make sure the scavenger system won’t cause high airway pressures due to backpressure on the anesthesia machine breathing circuit.

Typically, waste anesthetic gases flow into a scavenger system that is evacuated by the central medical vacuum or waste anesthesia gas disposal (WAGD) lines (; Anesthesia Equipment: Principles and Applications. 3rd ed., 2021). These central suction systems then vent to the outside of the building. Waste gas can accumulate in the room when these lines are obstructed or the system is not working. To prevent the hazard of waste gas exposure, avoid using inhaled anesthetics and nitrous oxide by choosing a total intravenous (TIVA) technique.

Elevated airway pressure is a potential hazard of some scavenger systems when the central vacuum fails or the vacuum or WAGD hose is disconnected or kinked. Symptoms when using the ventilator are inadvertent PEEP levels as high as 12 cm H2O, elevated mean airway pressure, and elevated peak airway pressure that progressively increases, especially at high fresh gas flows (Anesth Analg 2021;132:1191-8). The issue has been reported in the APSF Newsletter (Anesthesia Patient Safety Foundation Newsletter 2016;31:17; Anesthesiology News January 18, 2021). All of the machines involved have closed scavenger systems. To prevent the problem of elevated airway pressure with these machines in this situation, the reservoir collecting bag (usually located low on the left side of the anesthesia machine) should be removed from the closed scavenger system prior to use or if the backpressure problem occurs during use (see photo). All other modern anesthesia machines have open scavenger systems (identified by the absence of a bag) that should not create backpressure on the breathing circuit in the absence of active suction and thus do not need to be modified.

There are two options for a longer-term solution to removing waste anesthetic gases that do not depend on central suction. One is to avoid nitrous oxide and direct the waste gas through a canister of activated charcoal, which captures potent inhaled anesthetics but not nitrous oxide. This requires special equipment that may not be available. It also requires that canister weight be monitored to determine when the activated charcoal is saturated and needs to be disposed of and replaced. The second technique is to direct gases from a closed scavenger system to the intake duct of a nonrecirculating room ventilation intake duct (a technique called passive scavenging). This approach may require modification of the scavenger system and should only be taken in collaboration with the building facilities team. Keep in mind that these capabilities may not be available at your institution.

If inhaled anesthetics must be used, their effect on personnel can be reduced by avoiding nitrous oxide and after an intravenous induction using low-flow anesthesia to minimize anesthetics wasted into the OR. While this will slowly elevate the room air concentration of inhaled anesthetics, it is safe for short durations and may not elevate trace anesthetic levels above accepted thresholds in ORs with high fresh air turnover rates. See APSF Technology Education Initiative: Low-Flow Anesthesia ( for a tutorial on low-flow anesthesia, the ASA Statement on the Use of Low Gas Flows for Sevoflurane, October 2023 ( for a recent ASA-approved statement on the safety of low gas flows with sevoflurane, and the article “Low-Flow Sevoflurane is Safe, Economical, and Better for the Environment” (ASA Monitor 2023; 87:e4-e5) for the science behind it.

Dr. Staggenborg, a member of the ASA Committee on Practice Management, provides the following management perspective:

While there are no data on the incidence of central vacuum failure, it’s safe to say that this is an uncommon occurrence. One may, however, experience unattached or unavailable central vacuum in offsite locations, so there is value in thinking through the situation. In the case of central vacuum failure, your department may or may not be asked if it is safe to provide anesthesia services as your institution might not be aware of the machine implications, so you may need to be proactive.

Certainly, it is possible to proceed as outlined above, but remember, this was a case of short duration. The following questions should be considered: Are there enough stand-alone suction units for each anesthetizing location for secretions? Is our biomed/facilities department comfortable with the above machine modifications? Does our anesthesia department have the knowledge, experience, and supplies to perform TIVAs or low-flow anesthesia on every case? In this environment of drug shortages, pharmaceutical supplies are a valid concern, especially when doing TIVAs on a larger scale. Is the OR staff comfortable with potential exposure to volatile agents? On a broader level, what is the acuity of your cases? A hospital with an obstetrics unit or trauma services would have a different threshold for proceeding compared to a community hospital that does primarily elective cases. These are all difficult issues to navigate, and unfortunately there isn’t uniform guidance in this instance. The answer may be to perform all cases, perform only urgent or emergent cases, or to close the ORs altogether. Ultimately, it is up to the comfort level of your department.