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Inhalational Anesthetic Agents

Inhalational Anesthetic Agents

by Fatima Jen Pagsolingan -
Number of replies: 1

Good day! I have a few questions po on the use of inhaled anesthetics.

1. Since almost all volatile inhaled anesthetics directly depress uterine muscle tone, what is the usual recommended inhaled anesthetic for those requiring general anesthesia in those undergoing cesarian section?

2. Since some inhaled anesthetics can cause airway irritation and bronchospasm, what inhaled anesthetics is preferred for patients with asthma?

3. Xenon has demonstrated a lot of advantages over the other inhaled anesthetics, however, its limitation is its cost. In the Philippine setting, are there institutions which makes us of xenon as part of their inhalational anesthetic regimen?

4. Since inhaled anesthetics provide an easy route of administration, it is usually used for children and some adults. What other indications can be considered where the use of inhaled anesthetics is preferred over IV anesthetics?  

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In reply to Fatima Jen Pagsolingan

Re: Inhalational Anesthetic Agents

by Karel Ann Espejo -
Hi, Fatima!

1. You are correct, volatile anesthetics directly depress uterine tone. It does this in a dose-dependent manner such that higher %concentrations cause more depression. For CS, we can safely use volatile anesthetics, but we lower the %concentration to less than 1 MAC to minimize the effect on the tone. Luckily pregnant patients also has a lower MAC requirement so the lower vol% does not translate necessarily to inadequate depth of anesthesia. We also use uterotonics such as carbetocin, oxytocin etc. to helpstimulate uterine contraction.

2. In general, most inhaled anesthetics are safe to use in people with asthma since it causes direct bronchodilation. Airway irritation and spasm during inhaled anesthetics occur when the depth of anesthesia is inadequate. Thus, as long as the depth is adequate this rarely occurs. An exception is desflurane which can cause direct airway irritation, especially in sudden changes in concentration. However, this can still be safely used as long as you titrate it slowly, or ensure a deep level of anesthesia (via IV agents, for example.)

3. As of the moment, xenon is not a cost-effective gas. With the presence of cheaper more manageable agents, it is currently not used as an anesthetic in the Philippines.

4. You are correct, inhaled anesthesia is the preferred route for most patients. It has minimal metabolism, measurable alveolar levels, and easy route of intake and removal making it very titratable. We prefer inhalational anesthesia for most people unless there is a contraindication for it based on the procedure, comorbidities or logistics.

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