What are the safety considerations when using non-interlocked (vaporizers that do not prevent simultaneous administration of multiple anesthetic agents) vaporizers?

Safety Considerations for Non-Interlocked Vaporizers

Non-interlocked vaporizers pose significant safety risks due to the potential for inadvertent simultaneous administration of multiple anesthetic agents, which can lead to unpredictable anesthetic concentrations and potentially fatal cardiovascular collapse. 1

Key Safety Risks

• Non-interlocked vaporizers allow multiple vaporizers to be turned on simultaneously, which can result in uncontrolled and potentially lethal concentrations of anesthetic vapors being delivered to patients 1, 2
• Mixing of anesthetic agents can create unpredictable concentrations that may not be accurately detected by conventional monitoring equipment 3, 2
• When wrong agents are added to vaporizers, the delivered concentration may be significantly higher than expected, potentially reaching twice the intended MAC (Minimum Alveolar Concentration) 2

Essential Safety Precautions

Pre-use Checks

• Ensure that vaporizers are correctly fitted to the anesthetic machine with any locking mechanism fully engaged 1
• Verify that vaporizer control knobs rotate fully through their entire range 1
• Check that vaporizers are adequately filled but not overfilled, with filling ports tightly closed 1
• Perform manual leak testing on basic machines (following manufacturer's recommendations) by:
  • Setting oxygen flow at 5 L/min with vaporizer turned off
  • Temporarily occluding the common gas outlet
  • Confirming no leaks from any part of the vaporizer 1

During Use

• Turn off all vaporizers not in active use 1
• Maintain vigilant monitoring of end-tidal anesthetic gas concentrations whenever possible 4
• When changing vaporizers during a case, repeat the leak test as failure to do so is a common cause of critical incidents 1
• Keep vaporizers upright at all times, as tilting can result in delivery of dangerously high concentrations of vapor 1, 5

Critical Pitfalls to Avoid

• Never operate multiple vaporizers simultaneously as this can lead to unpredictable and potentially dangerous anesthetic concentrations 1, 2
• Avoid adding the wrong agent to a vaporizer, as some combinations (particularly Halothane added to an Enflurane vaporizer) can result in delivered concentrations twice the expected MAC 2
• Do not tilt or agitate loaded vaporizers, which can cause subsequent delivery of uncontrolled, potentially lethal concentrations 5
• Never attempt agent-vaporizer mismatching without end-tidal anesthetic gas monitoring, as this is an extremely dangerous practice 4

Modern Safety Solutions

• Use anesthetic gas monitors with automatic agent identification capability to detect erroneous agent mixtures 2
• Consider piezoelectric crystal monitoring which can correctly display the sum of multiple agent concentrations in volume percent 2
• Modern anesthetic workstations often include automatic vaporizer interlocking systems and vaporizer integrity testing 1

By following these safety precautions and understanding the risks associated with non-interlocked vaporizers, clinicians can significantly reduce the potential for adverse events related to inadvertent simultaneous administration of multiple anesthetic agents.