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Anesthetic vaporizers are an essential piece of anesthesia equipment. This activity reviews the modern anesthetic vaporizer classification, the physics principles behind their functioning, and possible hazards that could be present at the time of using an anesthetic vaporizer. It also highlights the role of the interprofessional team in managing the technical complications related to the use of anesthetic vaporizers in patients undergoing general anesthesia. Objectives: Identify the indications and contraindications for the use of anesthesia vaporizers. Describe the equipment required to administer anesthesia vaporizers. Review the potential complications and clinical significance of anesthetic vaporizers. Outline interprofessional team strategies for improving care coordination and communication to advance the use of anesthesia vaporizers and improve clinical outcomes. Access free multiple choice questions on this topic.

Since the first publicly performed anesthetic procedure at Massachusetts General Hospital in 1846, vaporizers have been an essential component of anesthesia equipment.[1] The emergence of potent inhalational anesthetics with unique properties has influenced the evolution of vaporizers. Modern anesthetic vaporizers have been developed to provide accurate amounts of anesthetic gas while mitigating the effects of temperature and barometric pressure on the evaporation process, allowing anesthesiologists to conduct their work with greater safety (see Image. Modern Classification of Vaporizers). The functioning of vaporizers is complex; and requires an in-depth understanding of thermodynamics, gases, and physics. While engineering may not be the forte of many anesthesiologists, familiarity with the proper functioning of the anesthetic equipment and the ability to recognize equipment failures are essential to decrease the potential for patient hazards.[2]

Safety Characteristics and Hazards of Vaporizers It is typically rare to have problems of any kind with anesthetic vaporizers, due to the huge engineering efforts for manufacturing these masterpieces. Many of the hazards related to anesthetic vaporizers are preventable and are more so related to inadequate manipulation by the provider.[11] Incorrect agent filling Many modern vaporizers have agent-specific inputs, making incorrect filling a user error. Vaporizers are, therefore labeled with colors to help reduce the probability of incorrect filling. The consequences of filling the vaporizer with the wrong anesthetic agent include overdose, as could be observed with desflurane, or underdose which could occur with the other halogenated liquids.[12] Tipping The inclination of a variable bypass vaporizer of more than 45º during transportation or replacement can cause the anesthetic liquid to flow into the variable bypass chamber. Once the dial is open, anesthetic liquid in the bypass chamber increases the concentration of anesthetic gas beyond what is marked on the dial. This situation is particularly dangerous for the patient and can last for an amount of time that is difficult to predict. The solution is to increase vaporization in the bypass chamber by decreasing the concentration marked on the dial and simultaneously increasing the FGF to 10 L/min for 20 to 30 minutes.[13] Simultaneous Administration of More Than One Vapor Since newer anesthetic machines with interlock safety devices do not allow the user to open 2 dials at the same time, this issue is somewhat anecdotal. Some older modules allow users to remove the central vaporizer, deactivating the interlock mechanism and permitting the administration of more than 1 vapor at a time. Overfilling the Vaporizer Newer vaporizers have a hole at the appropriate level to prevent overfilling. However, older vaporizers can still be overfilled. The excess anesthetic liquid will flow into the bypass chamber and, once the dial is open, potentially increase the concentration of anesthetic gas for an unpredictable amount of time. There is also a case report of a vaporizer malfunctioning secondary to overfilling where the wicks of the vaporizer were completely covered by the anesthetic liquid, preventing appropriate evaporation.[14] Vapor Leak into the Fresh Gas Line

Newer vaporizers have a hole at the appropriate level to prevent overfilling. However, older vaporizers can still be overfilled. The excess anesthetic liquid will flow into the bypass chamber and, once the dial is open, potentially increase the concentration of anesthetic gas for an unpredictable amount of time. There is also a case report of a vaporizer malfunctioning secondary to overfilling where the wicks of the vaporizer were completely covered by the anesthetic liquid, preventing appropriate evaporation.[14] Vapor Leak into the Fresh Gas Line The size of the leak depends on the ambient temperature and configuration of internal ports. Leakage is usually too small to produce a clinical effect. However, it can trigger an episode of malignant hyperthermia in patients with a known or unknown predisposition. Leaks Most gas leaks will be identified by checking the low-pressure system before using the anesthetic machine with a patient, and sometimes all that is needed is tightening a loose filler cap. The most concerning consequence of an unknown leakage is the administration of light anesthesia. Several case reports exist reporting this issue, with most of them having in common the inappropriate positioning of vaporizers on the back bar of the anesthesia machine. Others report inappropriate adjustments in the mounting system due to a missing rubber O-ring. Additionally, incompatibility between vaporizers and interlocks from different manufacturers could be the cause of leakage. Timely identification of this problem is facilitated by checking the anesthetic machine with the vaporizer in the ON and OFF positions.[15]

Anesthesia vaporizers are an essential part of anesthesia equipment. Understanding the physiology, physics, and mechanics behind anesthetic vaporizers ensures the proper use of these devices. The proper functioning and maintenance of these devices requires interprofessional communication between physicians, anesthesia technicians, and certified registered nurse anesthetists to enhance the safety of patients undergoing general anesthesia.