Neuromuscular Blocking Agents and Epiglottic Muscle Relaxation
Yes, the administration of an induction agent (such as propofol) followed by a paralytic agent (such as rocuronium) will relax the muscles controlling the epiglottis during anesthesia. This is a fundamental pharmacologic effect of neuromuscular blocking agents, which produce paralysis of all skeletal muscles, including those of the larynx and pharynx 1.
Mechanism of Muscle Relaxation
Neuromuscular blocking agents produce complete skeletal muscle paralysis by blocking acetylcholine receptors at the neuromuscular junction, affecting all voluntary muscles including those controlling the epiglottis, vocal cords, and other laryngeal structures 1. The laryngeal muscles are particularly sensitive to these agents, requiring lower concentrations for relaxation compared to peripheral muscles 1.
Specific Anatomical Effects
- The epiglottis is controlled by laryngeal muscles that are among the most sensitive to neuromuscular blockade, meaning they relax at lower drug concentrations than other muscle groups 1
- Both depolarizing agents (succinylcholine) and non-depolarizing agents (rocuronium, atracurium) produce complete relaxation of pharyngeal, laryngeal, and esophageal musculature 1, 2
- The corrugator supercilii muscle is recommended as the monitoring site during anesthesia specifically because its sensitivity and kinetics closely parallel those of the laryngeal muscles, confirming that laryngeal muscle relaxation occurs with standard dosing 1, 2
Clinical Implications for Airway Management
The relaxation of epiglottic and laryngeal muscles is the intended therapeutic effect that facilitates tracheal intubation and reduces pharyngeal/laryngeal injury 1. This complete muscle relaxation:
- Reduces pharyngeal and laryngeal injury during intubation from 22.6% to 9.7% when muscle relaxants are used (GRADE 1+ recommendation) 1
- Facilitates optimal intubating conditions by eliminating muscle tone and reflexes that would otherwise resist laryngoscopy 1, 3
- Creates vulnerability to upper airway obstruction immediately after induction, particularly with propofol alone, due to genioglossus suppression 4
Important Safety Considerations
The period immediately following loss of consciousness represents the highest risk for airway obstruction because propofol-induced muscle relaxation is incomplete without a neuromuscular blocker, while the genioglossus (tongue muscle) is suppressed 4. This creates a critical window where:
- Airway patency depends on proper positioning and potential airway adjuncts until the paralytic takes full effect 4
- Complete laryngospasm during this period may require neuromuscular blocking agents for resolution, as propofol alone is only 77% effective 4
- Immediate availability of succinylcholine and atropine in pediatric settings reduces cardiac arrest and severe airway obstruction by nearly 50% 2
Pharmacologic Specifics
Rocuronium at standard intubating doses (0.6-1.2 mg/kg) produces complete neuromuscular blockade within 60 seconds, including full relaxation of laryngeal and epiglottic muscles 1, 5, 6. The FDA labeling confirms that rocuronium's mechanism involves blocking acetylcholine at the motor endplate, affecting all skeletal muscles 5.
- Lower doses of rocuronium (0.1-0.2 mg/kg) are sufficient to achieve glottic opening and relax laryngeal muscles when adequate anesthetic depth is present 1, 7
- Volatile anesthetics (isoflurane, enflurane) potentiate rocuronium's effects by 20-40%, potentially requiring dose adjustments 5
- The duration and intensity of muscle relaxation can be monitored using train-of-four stimulation, with complete blockade indicated by absence of response 2