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Inhalation anesthetics (nitrous oxide, halothane, isoflurane, desflurane, sevoflurane, most commonly used agents in practice today) are used for induction and maintenance of general anesthesia in the operating room. This review is a general overview of inhalation anesthetic agents. Inhalation anesthetic agents are medications primarily used in the operating room to provide general anesthesia for surgery. This activity describes the indications, action, and contraindications for the use of inhalational anesthetic agents. This activity will also highlight the mechanism of action, adverse event profile, and other key factors (e.g., off-label uses, dosing, pharmacodynamics, pharmacokinetics, monitoring, relevant interactions) pertinent for members of the interprofessional healthcare team in providing general anesthesia. Objectives: Identify the mechanism of action of inhalation anesthetics. Describe the potential adverse effects of inhalational anesthetics. Review the appropriate monitoring for inhalational anesthetics. Outline some interprofessional team strategies for improving care coordination and communication to advance inhalational anesthetics and improve outcomes. Access free multiple choice questions on this topic.

It is worth mentioning that there is no pharmacological intervention for an overdose of inhaled anesthetics. In an overdose incident, the primary treatment method is supportive, with optimal ventilator settings and alveolar clearance. Several rare acute and chronic toxicities can occur with inhaled agents. Acute toxicities include carbon monoxide poisoning (CO2), nephrotoxicity, and hepatotoxicity. Chronic toxicities include hematotoxicity, teratogenic effects, and carcinogenic toxicities. The dose of Nitrous Oxide necessary used in a routine anesthetic can cause diffusion hypoxia. As gas exits the bloodstream into the lungs, the nitrous oxide displaces air and oxygen from the alveoli. This can be ameliorated by using supplemental oxygen to displace and dilute the nitrous oxide. Hepatotoxicity and hepatic failure is rare but has associations with patients who have suffered exposure to halothane.[10] Nephrotoxicity occurs most commonly with sevoflurane as its metabolism occurs at a much faster rate than other gases. This faster rate of absorption causes high levels of inorganic fluoride, which correlates with renal impairment. While this observation has largely occurred in research studies, the clinical recommendation remains to avoid sevoflurane in patients who have known renal dysfunction.[11][12] Carbon monoxide toxicity with inhaled anesthetics occurs most commonly with desflurane as it is the largest producer of CO.[13] Inhaled anesthetics can produce additional CO as dry CO2 absorbers are used in the perioperative setting; CO accumulates when not changed. Hematotoxicity is a chronic complication that can occur with prolonged exposure to nitrous oxide; this is due to a reduction in the recycling of vitamin B12.[14] If a patient has a chronic prolonged vitamin B12 deficiency, other symptoms such as megaloblastic anemia and neuropathies can begin to manifest. Additionally, when vitamin B12 metabolic pathways become disrupted, pregnant patients should be aware of potential teratogenic complications such as delayed cognitive impairment.[15] Halothane produces a decrease in cardiac output with increasing dosage. Care should be taken using this anesthetic with patients known to have a low cardiac ejection fraction.

Hematotoxicity is a chronic complication that can occur with prolonged exposure to nitrous oxide; this is due to a reduction in the recycling of vitamin B12.[14] If a patient has a chronic prolonged vitamin B12 deficiency, other symptoms such as megaloblastic anemia and neuropathies can begin to manifest. Additionally, when vitamin B12 metabolic pathways become disrupted, pregnant patients should be aware of potential teratogenic complications such as delayed cognitive impairment.[15] Halothane produces a decrease in cardiac output with increasing dosage. Care should be taken using this anesthetic with patients known to have a low cardiac ejection fraction. Neurologic and carcinogenic complications from volatile anesthetics or the choice of the anesthetic technique have not been reliably reproduced in human studies in randomized controlled studies. Increasing awareness has been growing regarding chlorofluorocarbon waste from volatile anesthetic gases as a source of pollution. Their impact on the environment, and costs and benefits of volatile anesthetics, and their alternatives will continue to be a topic of debate for the foreseeable future.

An interprofessional team is the best design when administering inhaled anesthetics. A care team can consist of an anesthesiologist, certified registered nurse anesthetist, physician assistant, nurse practitioner, pharmacist, and other additional staff, including postoperative nurses and technicians. Volatile anesthetics are also used in veterinary medicine and administered by a veterinarian or a technician. Designating roles in this setting is essential. Having a devoted postoperative nurse who monitors vital signs is necessary as this is the primary means for monitoring a patient's safety and comfort. The pharmacy will play a role in storing and preparing these agents for administration and need to be aware of all medications the patient is taking. This type of interprofessional teamwork is crucial to achieving optimal results when using inhaled anesthesia. [Level 5] The use of inhaled agents has also demonstrated benefits in the critical care setting, where they are often utilized in conjunction with intravenous anesthetics to provide optimal sedation for urgent procedural interventions. Their role outside of the operating room has increased as procedural suites outside the traditional operating room have also increased. Inhalational anesthetic agents have been used more in medically refractory epilepsy patients in neurointensive care units. These agents have also been used to treat status asthmaticus refractory to medical management. In this setting, physician assistants, nurse practitioners, critical care nurses, and ICU staff should have a fundamental knowledge of inhaled anesthetic agents. It is important to have essential care staff abreast of inhaled agents, and signs and symptoms of complications since this staff often see these patients in the postoperative anesthesia care unit or intensive care unit.