During induction of anesthesia, a patient receives a bolus of high-dose fentanyl intravenously and suddenly cannot be ventilated despite an open airway. The most likely mechanism of this complication is:

• A Direct diaphragmatic paralysis
• B Histamine-induced bronchospasm
• C Laryngospasm from increased secretions
• D Mu-receptor mediated truncal and thoracic skeletal muscle rigidity ✓

Explanation

Large intravenous doses of fentanyl and its congeners can trigger generalized thoracoabdominal muscle rigidity that prevents bag-mask ventilation, attributed to mu-receptor activity in supraspinal motor pathways. It is managed by neuromuscular blockade with succinylcholine or by naloxone, not by bronchodilators. Fentanyl notably does not release histamine, unlike morphine, which kills option B. Ventilation fails because the chest wall cannot expand, not because of airway closure.

Reference: Miller's Anesthesia Review / Goodman and Gilman's The Pharmacological Basis of Therapeutics, 13th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.