A 46-year-old man comes to the emergency department due to shortness of breath, cough, and fever. The patient began experiencing mild upper respiratory illness a week ago. He has a history of asthma and was using inhaled bronchodilators more frequently since the onset of respiratory illness. Over the past 2 days, he has had worsening breathlessness, productive cough, and high fever. The patient has no other medical conditions. Temperature is 38.9 C (102 F), blood pressure is 90/60 mm Hg, pulse is 120/min, and respirations are 28/min. On physical examination, the patient appears in severe respiratory distress with intercostal retractions. Lung auscultation reveals bilateral wheezing. Prompt endotracheal intubation for respiratory support is planned. Prior to endotracheal intubation, intravenous ketamine is administered for induction of anesthesia. Which of the following characteristics is the most likely reason for use of this anesthetic agent in this patient?

Question

A 46-year-old man comes to the emergency department due to shortness of breath, cough, and fever.  The patient began experiencing mild upper respiratory illness a week ago.  He has a history of asthma and was using inhaled bronchodilators more frequently since the onset of respiratory illness.  Over the past 2 days, he has had worsening breathlessness, productive cough, and high fever.  The patient has no other medical conditions.  Temperature is 38.9 C (102 F), blood pressure is 90/60 mm Hg, pulse is 120/min, and respirations are 28/min.  On physical examination, the patient appears in severe respiratory distress with intercostal retractions.  Lung auscultation reveals bilateral wheezing.  Prompt endotracheal intubation for respiratory support is planned.  Prior to endotracheal intubation, intravenous ketamine is administered for induction of anesthesia.  Which of the following characteristics is the most likely reason for use of this anesthetic agent in this patient?

Quizplus · Accepted Answer

This hemodynamically unstable patient has severe bronchospasm and impending respiratory failure and requires intubation. Prior to intubation, anesthesia must be induced. Three medications are commonly used because of their rapid onset of action and short duration of effect. In this patient with an acute asthma attack, ketamine was likely chosen because it stimulates release of catecholamines that increase sympathomimetic activity and may improve bronchospasm. (Choice A) Propofol and etomidate are both GABA agonists, but ketamine works at the NMDA receptor. (Choice B) Both ketamine and etomidate are much less lipophilic than propofol. (Choice C) Both ketamine and etomidate are metabolized primarily by the liver. Propofol is also metabolized by the liver, but the effect is terminated by its redistribution rather than metabolism. (Choice D) Neuromuscular blockade is often used to facilitate intubation. None of the three commonly used induction anesthetics cause significant neuromuscular blockade, so an additional medication (eg, succinylcholine, rocuronium) is used if needed. Educational objective: Ketamine can be used for anesthesia induction. The side effects of increased catecholamine release (eg, bronchodilation) are often exploited in patients with bronchospasm.

A 46-Year-Old Man Comes to the Emergency Department Due to Shortness