Paralysing Agents

by Qais Abuagla

General Information

Paralysis agents are neuromuscular-blocking agents (NMBA). They block neuromuscular transmission at the motor endplate.

Classification

  1. Non-depolarizing blocking agents (NDBA): They act by competitively blocking the binding of acetylcholine to its receptors, e.g., rocuronium
  2. Depolarizing blocking agents (DBA): These agents act by depolarizing the motor endplate of the skeletal muscle fiber. This persistent depolarization makes the muscle fiber resistant to further stimulation by acetylcholine, e.g., succinylcholine. It has 2 phases of action – fasciculation and then desensitization.

Indications

Paralysis drugs in the emergency department are used in rapid sequence intubation (RSI) to produce paralysis, which helps in RSI in 2 ways:

  1. paralyze the vocal cords, and permit intubation of the trachea
  2. relax the skeletal muscle to facilitate intubation

Succinylcholine

Succinylcholine is the only DBA used in the ED. It is rapidly hydrolyzed by plasma pseudocholinesterase into weak NMBA. Succinylcholine is rapidly active, typically producing intubating conditions within 45 seconds of administration by rapid intravenous bolus injection.

Contraindications

  • Hyperkalemia
  • Preexisting hyperkalemia
  • Burns >5 days old
  • Crush injury >5 days old
  • Severe infection >5 days old
  • Neuromuscular diseases (e.g., Myasthenia Gravis)
  • History of Malignant Hyperthermia
  • Allergy to succinylcholine

Dosing and Administration

  • Adult 1.5 mg/kg IV
  • Pediatrics 1.5 mg/kg IV

Adverse Effects

  • Cardiovascular System: Succinylcholine can lead to bradycardia, significant in pediatric patients that are 1 year and less. For that, some practitioners recommend atropine prior to succinylcholine administration, but there is no evidence supporting that.
  • Malignant Hyperthermia: is a syndrome characterized by rapid temperature rise and rhabdomyolysis. Treatment for this consists of cessation of any potential offending agents and administration of dantrolene.

Pregnant Patient Considerations

Category C

Rocuronium

Rocuronium is one of the NDBA. It works in less than 1 minute after administration.

Contraindications

  • No absolute contraindication to it
  • Anaphylaxis

Dosing and Administration

  • Adult 1 mg/kg
  • Pediatrics 1 mg/kg

Adverse Effects

  • Hypertension in 1-2%
  • Hypotension in 1-2%

Pregnant Patient Considerations

Category C

Reversal agent

Sugammadex

References and Further Reading