Recommendations for Preanesthesia Check Out Procedure

The followings table is the ASA (American Society of Anesthesiologist) recommendation of Preanesthesia checkout procedures. Some of the items listed may not available in each hospital; it is advisable that each department will prepare a procedure list which is appropriate for checkout of each type of gas machine they use (Table 4.1).


Table 4.1 Preanesthesia Checkout Procedures (ASA Recommendations)

To Be Completed Daily
Item 1. Verify auxiliary oxygen cylinder and self-inflating manual ventilation device are available & functioning Failure to ventilate is a major cause of morbidity and mortality related to anesthesia care. Because equipment failure with resulting inability to ventilate the patient can occur at any time, a self-inflating manual ventilation device (eg. AMBU bag) should be present at every anesthetizing location for every case and should be checked for proper function. In addition, a source of oxygen separate from the anesthesia machine and pipeline supply, specifically an oxygen cylinder with regulator and a means to open the cylinder valve, should be immediately available and checked. After checking the cylinder pressure, it is recommended that the main cylinder valve be closed to avoid inadvertent emptying of the cylinder through a leaky or open regulator.
Item 2. Verify suction is adequate to clear the airway Safe anesthetic care requires the immediate availability of suction to clear the airway if needed.
Item3. Turn on anesthesia delivery system and confirm that AC power is available. Anesthesia delivery systems typically function with backup battery power if AC power fails. Unless the presence of AC power is confirmed, the first obvious sign of power failure can be a complete system shutdown when the batteries can no longer power the system. Many anesthesia delivery systems have visual indicators of the power source showing the presence of both AC and battery power. These indicators should be checked and connection of the power cord to a functional AC power source should be confirmed.
Item 4. Verify availability of required monitors and check alarms. Standards for patient monitoring during anesthesia are clearly defined. The ability to confirm to these standards should be confirmed for every anesthetic.
  • The first step is to visually verify that the appropriate monitoring supplies (BP cuffs, oximetry probes, etc.) are available. All monitors should be turned on and proper completion of power-up self tests confirmed.
  • Given the importance of pulse oximetry and capnography to patient safety, verifying proper function of these devices before anesthetizing the patient is essential.

o Capnometer function can be verified by exhaling through the breathing circuit or gas sensor to generate a capnogram, or verifying that the patient's breathing efforts generate a capnogram before the patient is anesthetized. Visual and audible alarm signals should be generated when this is discontinued.

o Pulse oximeter function, including an audible alarm, can be verified by placing the sensor on a finger and observing for a proper recording. The pulse oximeter alarm can be tested by introducing motion artifact or removing the sensor.

  • Audible alarms have also been reconfirmed as essential to patient safety by ASA. Proper monitor functioning includes visual and audible alarm signals that function as designed.
Item 5. Verify that pressure is adequate on the spare oxygen cylinder mounted on the anesthesia machine. Anesthesia delivery systems rely on a supply of oxygen for various machine functions. At a minimum, the oxygen supply is used to provide oxygen to the patient. Pneumatically-powered ventilators also rely on a gas supply. Oxygen cylinder(s) should be mounted on the anesthesia delivery system and determined to have an acceptable minimum pressure. The acceptable pressure depends on the intended use, the design of the anesthesia delivery system and the availability of piped oxygen. Typically, an oxygen cylinder will be used if the central oxygen supply fails.
  • If the cylinder is intended to be the primary source of oxygen (e.g. remote site anesthesia), then a cylinder supply sufficient to last for the entire anesthetic is required.
  • If a pneumatically-powered ventilator that uses oxygen as its driving gas will be used, a full E oxygen cylinder may provide only 30 minutes of oxygen. In that case, the maximum duration of oxygen supply can be obtained from an oxygen cylinder if it is used only to provide fresh gas to the patient in conjunction with manual or spontaneous ventilation. Mechanical ventilators will consume the oxygen supply if pneumatically powered ventilators that require oxygen to power the ventilator are used.
  • Electrically-powered ventilators do not consume oxygen so that the duration of a cylinder supply will depend only on total fresh gas flow.

The oxygen cylinder valve should be closed after it has been verified that adequate pressure is present, unless the cylinder is to be the primary source of oxygen (i.e. piped oxygen is not available). If the valve remains open and the pipeline supply should fail, the oxygen cylinder can become depleted while the anesthesia provider is unaware of the oxygen supply problem.
Item 6.Verify that piped gas pressures are ≥ 50 psig. A minimum gas supply pressure is required for proper function of the anesthesia delivery system. Gas supplied from a central source can fail for a variety of reasons. Therefore the pressure in the piped gas supply should be checked at least once daily.
Item 7. Verify that vaporizers are adequately filled and, if applicable, that the filler ports are tightly closed. If anesthetic vapor delivery is planned, an adequate supply is essential to reduce the risk of light anesthesia or recall. This is especially true if an anesthetic agent monitor with a low agent alarm is not being used. Partially open filler ports are a common cause of leaks that may not be detected if the vaporizer control dial is not open when a leak test is performed. This leak source can be minimized by tightly closing filler ports. Newer vaporizer designs have filling systems that automatically close the filler port when filling is completed.
Item 8. Verify that there are no leaks in the gas supply lines between the flowmeters and the common gas outlet. The gas supply in this part of the anesthesia delivery system passes through the anesthetic vaporizer(s) on most anesthesia delivery systems. In order to perform a thorough leak test, each vaporizer must be turned on individually to check for leaks at the vaporizer mount(s) or inside the vaporizer. Furthermore, some machines have a check valve between the flowmeters and the common gas outlet, requiring a negative pressure test to adequately check for leaks. Automated checkout procedures typically include a leak test but may not evaluate leaks at the vaporizer especially if the vaporizer is not turned on during the leak test. When relying upon automated testing to evaluate the system for leaks, the automated leak test would need to be repeated for each vaporizer in place. This test should also be completed whenever a vaporizer is changed. The risk of a leak at the vaporizer depends upon the vaporizer design. Vaporizer designs where the filler port closes automatically after filling can reduce the risk of leaks. Technicians can provide useful assistance with this aspect of the machine checkout since it can be time consuming.
Item 9.Test scavenging system function. A properly functioning scavenging system prevents room contamination by anesthetic gases.
  • Proper function depends upon correct connections between the scavenging system and the anesthesia delivery system. These connections should be checked daily by a provider or technician.
  • Depending upon the scavenging system design, proper function may also require that the vacuum level is adequate which should also be confirmed daily.
  • Some scavenging systems have mechanical positive and negative pressure relief valves. Positive and negative pressure relief is important to protect the patient circuit from pressure fluctuations related to the scavenging system. Proper checkout of the scavenging system should ensure that positive and negative pressure relief is functioning properly. Due to the complexity of checking for effective positive and negative pressure relief, and the variations in scavenging system design, a properly trained technician can facilitate this aspect of the checkout process.
Item 10. Calibrate, or verify calibration of, the oxygen monitor and check the low oxygen alarm. Continuous monitoring of the inspired oxygen concentration is the last line of defense against delivering hypoxic gas concentrations to the patient. The oxygen monitor is essential for detecting adulteration of the oxygen supply.
  • Most oxygen monitors require calibration once daily, although some are self-calibrating. For self-calibrating oxygen monitors, they should be verified to read 21% when sampling room air. This is a step that is easily completed by a trained technician.
  • When more than one oxygen monitor is present, the primary sensor which will be relied upon for oxygen monitoring should be checked.
  • The low oxygen concentration alarm should also be checked at this time by setting the alarm above the measured oxygen concentration and confirming that an audible alarm signal is generated.
Item 11. Verify carbon dioxide absorbent is not exhausted. Proper function of a circle anesthesia system relies on the absorbent to remove carbon dioxide from rebreathed gas. Exhausted absorbent as indicated by the characteristic color change should be replaced. It is possible for absorbent material to lose the ability to absorb CO2 yet the characteristic color change may be absent or difficult to see. Some newer absorbents do change color when desiccated. Capnography should be utilized for every anesthetic and, when using a circle anesthesia system, rebreathing carbon dioxide as indicated by an inspired CO2 concentration > 0 can also indicate exhausted absorbent.
Item 12. Breathing system pressure and leak testing. The breathing system pressure and leak test should be performed with the circuit configuration to be used during anesthetic delivery. If any components of the circuit are changed after this test is completed, the test should be performed again. Although the anesthesia provider should perform this test before each use, anesthesia technicians who replace and assemble circuits can also perform this check and add redundancy to this important checkout procedure. Proper testing will demonstrate that pressure can be developed in the breathing system during both manual and mechanical ventilation and that pressure can be relieved during manual ventilation by opening the APL valve. Automated testing is often implemented in the newer anesthesia delivery systems to evaluate the system for leaks and also to determine the compliance of the breathing system. The compliance value determined during this testing will be used to automatically adjust the volume delivered by the ventilator to maintain a constant volume delivery to the patient. It is important that the circuit configuration that is to be used be in place during the test.
Item 13. Verify that gas flows properly through the breathing circuit during both inspiration and exhalation. Pressure and leak testing does not identify all obstructions in the breathing circuit or confirm proper function of the inspiratory and expiratory unidirectional valves. A test lung or second reservoir bag can be used to confirm that flow through the circuit is unimpeded. Complete testing includes both manual and mechanical ventilation. Proper function of unidirectional valves cannot be visually assessed since subtle valve incompetence may not be detected. Checkout procedures to identify valve incompetence which may not be visually obvious can be implemented but are typically too complex for daily testing. A trained technician can perform regular valve competence tests. Capnography should be used during every anesthetic and the presence of carbon dioxide in the inspired gases can help to detect an incompetent valve.
Item 14. Document completion of checkout procedures. Each individual responsible for checkout procedures should document completion of these procedures. Documentation gives credit for completing the job and can be helpful if an adverse event should occur. Some automated checkout systems maintain an audit trail of completed checkout procedures that are dated and timed.
Item 15. Confirm ventilator settings and evaluate readiness to deliver anesthesia care This step is intended to avoid errors due to production pressure or other sources of haste. The goal is to confirm that appropriate checks have been completed and that essential equipment is indeed available. The concept is analogous to the time out used to confirm patient identity and surgical site prior to incision. Improper ventilator settings can be harmful especially if a small patient is following a much larger patient or vice versa. Pressure limit settings (when available) should be used to prevent excessive volume delivery from improper ventilator settings.
Last modified: Tuesday, 15 November 2016, 7:17 PM