Which of the following agents may precipitate bronchospasm in patients with reactive airway disease?
**Core Concept**
Methohexital, a barbiturate anesthetic, can precipitate bronchospasm in patients with reactive airway disease due to its potential to release histamine and cause smooth muscle contraction. This is a critical consideration for anesthesiologists when selecting an induction agent for patients with pre-existing respiratory conditions.
**Why the Correct Answer is Right**
Methohexital can induce histamine release, which in turn stimulates the H1 receptors on smooth muscle cells, leading to bronchoconstriction. This is particularly concerning in patients with reactive airway disease, such as asthma, as it can exacerbate existing bronchospasm. The histamine release is thought to be due to the ability of methohexital to bind to histamine release sites on mast cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Midazolam, a benzodiazepine, is not typically associated with histamine release or bronchospasm. It is often used as an anxiolytic and sedative in patients with respiratory conditions.
**Option B:** Etomidate, an imidazole-derived anesthetic, is known for its minimal impact on respiration and is often chosen for patients with severe respiratory compromise. It is less likely to precipitate bronchospasm compared to methohexital.
**Option D:** Propofol, an alkylphenol anesthetic, is generally considered safe for use in patients with reactive airway disease. It does not typically release histamine and is often used as a first-line agent for anesthesia induction.
**Clinical Pearl / High-Yield Fact**
Methohexital's propensity for histamine release makes it a high-risk agent for patients with reactive airway disease. When choosing an anesthetic agent for these patients, it's essential to select a drug that minimizes the risk of bronchospasm, such as etomidate or propofol.
**✓ Correct Answer: C. Methohexital**