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Anesthetic gases (nitrous oxide, halothane, isoflurane, desflurane, sevoflurane), also known as inhaled anesthetics, are administered as primary therapy for preoperative sedation and adjunctive anesthesia maintenance to intravenous (IV) anesthetic agents (i.e., midazolam, propofol) in the perioperative setting. Inhaled anesthetics enjoy regular use in the clinical setting due to chemical properties that allow the rapid introduction of an agent into arterial blood via the pulmonary circulation compared to the more circuitous route of venous circulation. This activity reviews the mechanism of action, adverse event profile, and other key factors (e.g., dosing, pharmacodynamics, pharmacokinetics, monitoring, relevant interactions) pertinent to members of the interprofessional team for the use of these anesthetic gases. Objectives: Identify the approved and off-label uses for anesthetic gases. Summarize the general mechanism of action for anesthetic gases. Review the potential adverse events and current research on contraindications with the use of anesthetic gases. Outline interprofessional team strategies for improving care coordination and communication to advance appropriate clinical outcomes when using anesthetic gases where applicable. Access free multiple choice questions on this topic.

As stated above, these gases are relatively benign for acute adverse reactions.[9] The toxic profiles for these gases fall into acute and chronic toxicities. Acute Toxicities [15] Nephrotoxicity- Nephrotoxicity can occur with all volatile gases. Sevoflurane is metabolized by CYP2E1 at a much faster rate compared to the other volatile gases and produces increased levels of inorganic fluoride (F), which has been shown during in vivo studies of rats to cause renal impairment. Clinically, this renal impairment has not been reported; however, the recommendation is still that sevoflurane not be used in patients with preexisting renal dysfunction undergoing extensive procedures. Hepatotoxicity – uncommon, but reports exist of individuals with prior exposure specifically to halothane. Patients would present immediately after a procedure with halothane-induced fulminant hepatic failure. Carbon monoxide (CO) poisoning – is a concern as all inhaled anesthetics can produce CO from interaction with the dry CO2 absorbers used in the perioperative setting. The largest producer of CO in this manner is desflurane. This situation can is avoidable by routinely changing the absorbent before each day of cases. Chronic Toxicities [15] Hematotoxicity – chronic exposure to N2O has shown to decrease methionine synthase activity, an important enzyme in the recycling of vitamin B. Prolonged vitamin B deficiency can result in megaloblastic anemia, and peripheral neuropathies in patients who work in dental practices should prompt clinical suspicion of this etiology. Teratogenic/reproductive effects – early exposure can cause cognitive impairment later in life, particularly N2O, as described above, which can disrupt vitamin B-dependent metabolic pathways. Carcinogenic – continued exposure to trace concentrations of anesthetic gases by operating room personnel correlated with increasing rates of cancer diagnosis in these individuals Overdose or Postoperative Reversal There is no pharmacological reversal of anesthetic gases in use for postoperative recovery or in the event of an overdose. The primary reversal method is to remove the patient from continued exposure to gas and hyperventilate to decrease the concentration of gas in the patient’s alveoli.[7] The "ANEclear" device is a novel method for removing anesthetic gases.[16]

Anesthetic gas use is chiefly the purview of the anesthesiologist, anesthesia nurse, and emergency department physician. However, to ensure the patient's safety, the practice of anesthesia is best done with an interprofessional team that also includes anesthesia nurses, recovery room nurses, and anesthesia assistants. Since there is no antidote to an anesthetic gas, the patient requires close monitoring during anesthesia. A dedicated nurse should monitor the vital signs continuously during induction and maintenance to ensure that the patient is not only sedated but has no pain. There are standard protocols for patient monitoring during anesthesia established by all hospitals. Pharmacy is responsible for the delivery of the proper agents and ensuring that dosing and administration are correct, providing a "second set of eyes" to assist the anesthesiologist or nurse anesthetist. After completing the procedure, the patient must be monitored by the recovery room nurses until the patient is fully awake and hemodynamically stable. The anesthesiologist should receive immediate notification if there are problems with the vital signs, oxygenation, and respiration in the recovery room. More crucially, resuscitation equipment should always be available when using anesthetic gases. Ultimately, the anesthesia nurse is responsible for ensuring that the gas canisters are full and that all the monitoring equipment is in working order. Any deficits require the attention and input of the entire interprofessional healthcare team; this is the only way to ensure patient safety. [Level 5]