Recommended Sequence of Arrangement for Non-Interlocked Vaporizers
For non-interlocked vaporizers, the recommended sequence of arrangement should place vaporizers with higher vapor pressures and lower boiling points downstream (further away from the fresh gas flow) to minimize the risk of overdose and ensure patient safety.
Understanding Non-Interlocked Vaporizers
Non-interlocked vaporizers differ from interlocked systems in that multiple vaporizers can potentially be turned on simultaneously, creating significant patient safety risks:
- Non-interlocked vaporizers should be carefully arranged to minimize the risk of accidental delivery of multiple anesthetic agents, which could lead to unpredictable anesthetic depth and cardiovascular collapse 1
- Each vaporizer must be checked individually to ensure proper functioning, with manual leak testing performed on basic machines (though this may be harmful to modern workstations) 1
Proper Sequence Arrangement Principles
The arrangement of non-interlocked vaporizers should follow these principles:
- Vaporizers should be arranged according to the physical properties of the anesthetic agents, particularly vapor pressure and boiling point 2, 3
- Agents with higher vapor pressure and lower boiling points should be placed downstream (further from the fresh gas flow) 2, 3
- This arrangement minimizes the risk of accidental overdose if multiple vaporizers are accidentally turned on simultaneously 1, 4
Specific Arrangement Recommendations
When arranging multiple non-interlocked vaporizers:
- Place vaporizers containing agents with lower vapor pressure (higher boiling points) upstream (closer to fresh gas flow)
- Place vaporizers containing agents with higher vapor pressure (lower boiling points) downstream (further from fresh gas flow)
For common anesthetic agents, this typically means:
- Sevoflurane (vapor pressure: 160 mmHg at 20°C) should be placed upstream 2, 3
- Isoflurane (vapor pressure: 238 mmHg at 20°C) should be placed in the middle position 2, 3
- Desflurane (vapor pressure: 669 mmHg at 20°C) should be placed downstream 2, 3
Safety Precautions for Non-Interlocked Vaporizers
To ensure patient safety when using non-interlocked vaporizers:
- Always verify that only one vaporizer is turned on at any time 1
- Perform manual leak testing on each vaporizer individually by setting oxygen flow to 5 L/min, occluding the common gas outlet, and checking for leaks 1
- Keep vaporizers upright at all times, as tilting can result in dangerously high concentrations of vapor 1, 5
- When changing vaporizers during use, repeat the leak test to prevent critical incidents 1
Common Pitfalls and Caveats
Several dangerous situations can arise with non-interlocked vaporizers:
- Accidental simultaneous activation of multiple vaporizers can lead to unpredictable anesthetic depth and potentially fatal overdose 1, 4
- Filling a vaporizer with the wrong agent can result in fourfold underdoses or overdoses 4
- Mixing of anesthetic agents in vaporizers creates non-ideal solutions with unpredictable vapor concentrations 4
- Tilting vaporizers during transport or installation can cause delivery of dangerously high concentrations of anesthetic 1, 5
By following these recommendations for the sequence arrangement of non-interlocked vaporizers, anesthesia providers can minimize risks and enhance patient safety during anesthetic delivery.