The following checks should be carried out at the beginning of each operating theatre session. In addition, specific checks should be carried out before each new patient during a session or when there is any alteration or addition to the breathing system, monitoring or ancillary equipment.
It is the responsibility of the anaesthetist to make sure that these checks have been performed, and the anaesthetist must be satisfied that they have been carried out correctly. In the event of a change of anaesthetist during an operating session, the status of the anaesthetic equipment must be confirmed, including that a formal check has been perform before taking over.
Before using any anaesthetic equipment, ventilator, breathing system or monitor, it is essential to be fully familiar with it. Modern anaesthetic workstations are complex devices. It is essential that anaesthetists have full training and formal induction for any machines they may use the first time by qualified personnel. A quick‘run-through’ before the start of an operating session is not acceptable.
Careful note should be taken of any information or labelling on the anaesthetic machine that might refer to its current status. e.g. date of last service.
Alternative Means Of Ventilation
The early use of an alternative means of ventilation (a self-inflating bag that does not rely on a source of oxygen to function) may be life-saving.
A self-inflating bag must be immediately available in any location where anaesthesia may be given [7, 8]. An alternative source of oxygen should be readily available.
Perform Manufacturer’s Machine Check
Modern anaesthesia workstations may perform many of the following checks automatically during start-up. Users must know which are included and ensure that the automated check has been performed.
- Check that the anaesthetic workstation and relevant ancillary equipment are connected to the mains electrical supply (where appropriate) and switched on. The anaesthetic workstation should be connected directly to the mains electrical supply, and only correctly rated equipment connected to its electrical outlets. Multisocket extension leads must not be plugged into the anaesthetic machine outlets or used to connect the anaesthetic machine to the mains supply.
- Hospitals should have back-up generators, and many operating theatres will have their own back-up system. Anaesthetists should know what is available where they are working. Back-up batteries for anaesthetic machines and other equipment should be charged.
- Switch on the gas supply master switch (if one is fitted).
- Check that the system clock (if fitted) is set correctly
Gas Supplies and Suction
To check the correct function of the oxygen failure alarm involves disconnecting the oxygen pipeline on some machines, whilst on machines with a gas supply master switch, the alarm may be operated by turning the master switch off.
As repeated disconnection of gas hoses may lead to premature failure of the Schrader socket and probe, these guidelines recommend that the regular presession check of equipment includes a ‘tug test’ to confirm correct insertion of each pipeline into the appropriate socket. It is therefore recommended that, in addition to these checks, the oxygen failure alarm must be checked on a weekly basis by disconnecting the oxygen hose whilst the oxygen flowmeter is turned on, and a writtenrecord kept. In addition to sounding an alarm, which must sound for atleast 7s, oxygen failure warning devices are also linked to a gas shut-off device. Anaesthetists must be aware of both the tone of the alarm and also which gases will continue to flow on the particular model of anaesthetic machine in use.
Medical Gas Supplies
Identify and take note of the gases that are being supplied by pipeline, confirming with a ‘tug test’ that each pipeline is correctly inserted into the appropriate gas supply terminal. Note that excessive force during a ‘tug test’ may damage the pipeline and ⁄ or gas supply terminal.
- Check that the anaesthetic apparatus is connected to a supply of oxygen and that an adequate reserve supply of oxygen is available from a spare cylinder.
- Check that adequate supplies of any other gases intended for use are available and connected as appropriate. All cylinders should be securely seated and turned off after checking their contents.
- Carbon dioxide cylinders should not be present on the anaesthetic machine. Where a blanking plug is supplied this should be fitted to any empty cylinder yoke.
- Check that all pressure gauges for pipelines connected to the anaesthetic machine indicate 400–500 kPa.
- Check the operation of flowmeters, where these are present, ensuring that each control valve operates smoothly and that the bobbin moves freely throughout its range without sticking. If nitrous oxide is to be used, the anti-hypoxia device should be tested by first turning on the nitrous oxide flow and ensuring that at least 25% oxygen also flows. Then turn the oxygen flow off and check that the nitrous oxide flow also stops. Turn on the oxygen flow and check that the oxygen analyser display approaches 100%. Turn off all flow control valves. (Machines fitted with a gas supply master switch will continue to deliver a basal flow of oxygen).
- Operate the emergency oxygen bypass control and ensure that flow occurs from the gas outlet without significant decrease in the pipeline supply pressure. Ensure that the emergency oxygen bypass control ceases to operate when released.
Check that the suction apparatus is functioning and all connections are secure; test for the rapid development of an adequate negative pressure.
Breathing System and Vaporisers
Whole Breathing System
Check all breathing systems that are to be used and perform a ‘two-bag test’ before use, as described below. Breathing systems should be inspected visually and inspected for correct configuration and assembly. Check that all connections within the system and to the anaesthetic machine are secured by ‘push and twist’. Ensure that there are no leaks or obstructions in the reservoir bags or breathing system and that they are not obstructed by foreign material. Perform a pressure leak test (between 20 and 60 cmH2O on the breathing system by occluding the patient-end and compressing the reservoir bag.
Manual leak testing of vaporisers was previously recommended routinely. It should only be performed on basic ‘Boyle’s’ machines and it may be harmful to many modern anaesthetic workstations. Refer to themanufacturer’s recommendation before performing a manual test. Check that the
vaporiser(s) for the required volatile agent(s) are fitted correctly to the anaesthetic machine, that any locking mechanism is fully engaged and that the control knobs rotate fully through the full range(s). Ensure that the vaporiser is not tilted. Turn off the vaporisers. Check that the vaporiser(s) are adequately filled but not overfilled, and that the filling port is tightly closed.
Manual Leak Test of Vaporiser
- Set a flow of oxygen of 5 L / min and with the vaporiser turned off, temporarily occlude the common gas outlet. There should be no leak from any part of the vaporiser and the flowmeter bobbin (if present) should dip.
- Where more than one vaporiser is present, turn each vaporiser on in turn and repeat this test. After this test, ensure that the vaporisers and flowmeters are turned off.
Changing and filling vaporisers during use. It may be necessary to change a vaporiser during use. Where possible, repeat the leak test; failure to do so is a common cause of critical incidents. Some anaesthetic workstations will automatically test vaporiser integrity. It is only necessary to remove a vaporiser from a machine to refill it if the manufacturer recommends this. Vaporisers must always be kept upright. Tilting a vaporiser can result in delivery of dangerously high concentrations of vapour.
Carbon Dioxide Absorber
Inspect the contents and connections and ensure there is adequate supply of carbon dioxide absorbent.
Check the colour of the absorbent – Indicate what colour shows that it is exhausted.
Alternative Breathing Systems
For Bain-type and circle co-axial systems, perform an occlusion test on the inner tube and check that the adjustable pressure limiting (APL) valve, where fitted, can be fully opened and closed.
Correct Gas Outlet
Particular care must be exercised in machines with an auxiliary common gas outlet (ACGO). Incidents of patient harm have resulted from misconnection of a breathing system to an ACGO or mis-selection of the ACGO.
Whenever a breathing system is changed, either during a case or a list, its integrity and correct configuration must be confirmed. This is particularly important for paediatric lists when breathing systems maybe changed frequently during a list.
- Check that the ventilator is configured correctly for its intended use. Ensure that the ventilator tubing is securely attached. Set the controls for use and ensure that adequate pressure is generated during the inspiratory phase.
- Check that alarms are working and correctly configured.
- Check that the pressure relief valve functions correctly at the set pressure
A two-bag test should be performed after the breathing system, vaporisers and ventilator have been checked individually.
- Attach the patient-end of the breathing system (including angle piece and filter) to a test lung or bag.
- Set the fresh gas flow to 5 l/min and ventilate manually. Check the whole breathing system is patent and the unidirectional valves are moving (if present).
- Check the function of the APL valve by squeezing both bags.
- Turn on the ventilator to ventilate the test lung. Turn off the fresh gas flow or reduce to a minimum. Open and close each vaporiser in turn. There should be no loss of volume in the system.Breathing systems should be protected with a test lung or bag when not in use to prevent intrusion of foreign bodies.
Check that the anaesthetic gas scavenging system is switched on and functioning. Ensure that the tubing is attached to the appropriate exhaust port of the breathing system, ventilator or anaesthetic workstation.
Check that all monitoring devices are functioning and that appropriate parameters and alarms have been set before using the anaesthetic machine.
This includes the cycling times, or frequency of recordings, of automatic noninvasive blood pressure monitors. Check that gas sampling lines are properly attached and free from obstruction or kinks. In particular, check that the oxygen analyser, pulse oximeter and capnograph are functioning correctly and that appropriate alarm limits for all monitors are set.
Be aware of the ‘default’ alarm settings if using these.
Gas monitoring lines are often the cause of a significant leak; check that they are properly attached and any sampling ports not in use have been blanked off. To eliminate the need to change the sampling line repeatedly, the gas monitoring line should be assembled as an integral part of the breathing circuit by attaching it proximal to the patient breathing filter.
These include bacterial filters, catheter mounts, connectors and endotracheal, laryngeal mask airways, etc; check that these are all available in the appropriate sizes, at the point of use, and that they have been checked for patency.
A new, single-use bacterial filter and angle piece ⁄ catheter mount must be used for each patient. It is important that these are checked for patency and flow, both visually and by ensuring gas flow through the whole assembly when connected to the breathing system, as described below.
Check that the appropriate laryngoscopes are available and function reliably. Equipment for the management of the anticipated or unexpected difficult airway must be available and checked regularly in accordance with departmental policies. A named consultant anaesthetist must be responsible for difficult airway equipment and the location of this equipment should be known by all.
Total Intravenous Anaesthesia (TIVA)
When TIVA is used there must be a continuous intravenous infusion of anaesthetic agent or agents; interruption from whatever cause may result in awareness. A thorough equipment check is therefore the most important step in reducing the incidence of awareness. Anaesthetists using TIVA must be familiar with the drugs, the technique and all equipment and disposables being used.
The Safe Anaesthesia Liaison Group (SALG) has produced safety guidance on guaranteeing drug delivery during TIVA; SALG made the following
- An anti-reflux ⁄ non-return valve should always be used on the intravenous fluid infusion line when administering TIVA.
- Sites of intravenous infusions should be visible so that they maybbemonitored for disconnection, leaks or infusions into subcutaneous tissues.
- Clinical staff should know how to use, and to check, the equipment before use.Organisations should give preference to purchasing intravenous connectors and valves that are clearly labeled.
Ancillary and Resuscitation Equipment
Check that the patient’s trolley, bed or operating table can be tilted head-down rapidly. A resuscitation trolley and defibrillator must be available in all locations where anaesthesia is given and checked regularly in accordance with local policies.
Equipment and drugs for rarely encountered emergencies, such as malignant hyperthermia and local anaesthetic toxicity must be available and checked regularly in accordance with local policies. The location of these must be clearly signed.
Any part of the breathing system, ancillary equipment or other apparatus that is designated ‘single-use’ must be used for one patient only, and not reused. Packaging should not be removed until the point of use, for infection control, identification and safety.
In the event of failure, some modern anaesthetic workstations may default too little or no flow, may entrain room air or oxygen only with no vapour.
Users must know the default setting for the machine in use.
Alternative means of oxygenation, ventilation and anaesthesia must be available.
‘Shared Responsibility’ Equipment
As a member of the theatre team, the anaesthetist will share responsibility for the use of other equipment, e.g. diathermy, intermittent compression stockings, warming devices, cell salvage and tourniquets, but should have received appropriate training. Involvement with this equipment, especially ‘trouble shooting’ problems that arise intra-operatively, must not be allowed to distract anaesthetists from their primary role.
Recording and Audit
A clear note must be made in the patient’s anaesthetic record that the anaesthetic machine check has been performed, that appropriate monitoring is in place and functional, and that the integrity, patency and safety of the whole breathing system has been assured. A logbook should also be kept with each anaesthetic machine to record the daily pre-session check and weekly check of the oxygen failure alarm. Modern anaesthesia workstations may record electronic self tests internally. Such records should be retained for an appropriate time. Documentation of the routine checking and regular servicing of anaesthetic machines and patient breathing systems should be sufficient to permit audit on a regular basis.
There must be clear departmental procedures for the daily and other checks of equipment that is used in post anaesthesia care unit recovery room. This may also include pre-use checks of patient-controlled analgesia and epidural pumps, etc.