A 28-year-old man is brought to the emergency department due to a construction site accident in which a heavy concrete slab fell on his legs. The patient was trapped from the waist down for about 15 minutes until other workers were able to rescue him. He sustained no injury to the head or upper torso and did not lose consciousness. The patient has no significant medical history and takes no medications. He drinks 1 or 2 beers daily but does not use tobacco or illicit drugs. Blood pressure is 140/90 mm Hg, and pulse is 110/min. Bilateral breath sounds are equal and normal. Heart sounds are not muffled. The abdomen is soft and nontender. There are obvious deformities, abrasions, and lacerations on both lower limbs. Radiographs reveal multiple bilateral lower extremity fractures. After the patient is cleared of other major trauma, he is taken for surgical stabilization and fixation of the lower extremity fractures. Succinylcholine is considered for rapid-sequence intubation. With the use of succinylcholine, this patient is at greatest risk for which of the following?

Question

A 28-year-old man is brought to the emergency department due to a construction site accident in which a heavy concrete slab fell on his legs.  The patient was trapped from the waist down for about 15 minutes until other workers were able to rescue him.  He sustained no injury to the head or upper torso and did not lose consciousness.  The patient has no significant medical history and takes no medications.  He drinks 1 or 2 beers daily but does not use tobacco or illicit drugs.  Blood pressure is 140/90 mm Hg, and pulse is 110/min.  Bilateral breath sounds are equal and normal.  Heart sounds are not muffled.  The abdomen is soft and nontender.  There are obvious deformities, abrasions, and lacerations on both lower limbs.  Radiographs reveal multiple bilateral lower extremity fractures.  After the patient is cleared of other major trauma, he is taken for surgical stabilization and fixation of the lower extremity fractures.  Succinylcholine is considered for rapid-sequence intubation.  With the use of succinylcholine, this patient is at greatest risk for which of the following?

Quizplus · Accepted Answer

Succinylcholine is a depolarizing neuromuscular blocker that works by binding to postsynaptic acetylcholine receptors to trigger influx of sodium ions and efflux of potassium ions through ligand-gated ion channels; depolarization occurs and temporary paralysis ensues (delayed repolarization of the skeletal muscle membrane). Succinylcholine is often used during rapid-sequence intubation as it has a rapid onset (45-60 seconds) and offset (6-10 minutes) of action. However, in certain patients it can cause life-threatening cardiac arrhythmia due to severe hyperkalemia. This patient has experienced an extensive skeletal muscle crush injury, which places him at risk for hyperkalemia due to skeletal muscle cell lysis (rhabdomyolysis). In addition, skeletal muscle injury leads to upregulation of postsynaptic acetylcholine receptors, which can result in massive efflux of potassium following administration of succinylcholine. Other relevant conditions that cause upregulation of acetylcholine receptors include burn injury, disuse muscle atrophy, and denervation (eg, stroke, Guillain-Barré syndrome, critical illness polyneuropathy). To avoid life-threatening hyperkalemia in such settings, nondepolarizing neuromuscular blocking agents (eg, vecuronium, rocuronium) should be used as they do not affect postsynaptic ligand-gated ion channels. (Choice A) Halothane can lead to acute liver failure due to production of hepatotoxic intermediary compounds; therefore, it is now rarely used. Adult women are at greatest risk of developing halothane-associated liver toxicity. (Choice B) Etomidate inhibits 11β-hydroxylase and can lead to adrenal insufficiency. The elderly and patients with critical illness (eg, sepsis) are typically susceptible. (Choice D) Nitrous oxide inactivates vitamin B₁₂, leading to inhibition of methionine synthase activity; subsequent neurotoxicity (eg, peripheral neuropathy) can result in patients with preexisting vitamin B₁₂ deficiency. (Choice E) Severe hypotension due to myocardial depression is a common adverse effect of propofol. Therefore, propofol should be avoided or used with extreme caution in patients with ventricular systolic dysfunction. Educational objective: Succinylcholine is a depolarizing neuromuscular blocker that can cause life-threatening hyperkalemia in patients with a condition leading to upregulation of postsynaptic acetylcholine receptors (eg, skeletal muscle trauma, burn injury, stroke). Nondepolarizing neuromuscular blocking agents (eg, vecuronium, rocuronium) should be used with these patients. References: Succinylcholine-induced hyperkalemia in acquired pathologic states: etiologic factors and molecular mechanisms. (http://www.ncbi.nlm.nih.gov/pubmed/16394702)

A 28-Year-Old Man Is Brought to the Emergency Department Due