1. Neuromuscular Blockers
Bernie Miller, MD
Medical Student Lecture Series

2. Content Outline Indications for Neuromuscular Blockade
Neuromuscular Junction
Classes of Neuromuscular Blockers
Metabolism of Neuromuscular Blockers
Monitoring Neuromuscular Blockade
Antagonism (Reversal) of Neuromuscular Blockers

3. Indications for Neuromuscular Blockade
Intubation
Optimize Surgical Conditions
Optimize Ventilation in ICU

4. Neuromuscular Junction

5. Classes of Neuromuscular Blockers
Depolarizing- Bind to and activate cholinergic receptors
Succinylcholine
Non Depolarizing- Competitively inhibit Ach binding at post-junctional receptors
Short Acting
Medium Acting
Long Acting

6. Succinylcholine Depolarizing neuromuscular blocker Dose: 0.5-1.5mg/kg
Onset: 30-60seconds
Duration: 5-10 Minutes
Metabolism: Hydrolysis by plasma cholinesterase

7. Succinylcholine
Phase 1: Membrane is depolarized by opening AChR channels- Brief fasciculation of muscles
Phase II: End-plate repolarizes, but is desensitized to acetylcholine

8. Succinylcholine-Adverse Side Effects
Cardiac Dysrhythmia
Fasciculations
Hyperkalemia
Myalgias
Myoglobinuria
Increased Intraocular Pressure
Increased Intracranial Pressure
Increased Intragastric Pressure
Trismus
Malignant Hyperthermia Trigger

9. Contraindications to Succinylcholine
Burn injury
Muscle Crush Injury
Stroke
Spinal Cord Injury
History of Malignant Hyperthermia
Neuromuscular Disorders
Relative Contraindications:
Eye Trauma, Increased ICP

10. Non Depolarizing Muscle Relaxants (NDMR)
Structure
Aminosteroids
Pancuronium
Pipercuronium
Vecuronium
Rocuronium
Benzylisoquinolinium
Atracurium
Cisatracurium

11. Long Acting- NDMR Pancuronium Dosage: Onset: 3-5 Minutes
Duration: Minutes
Metabolism: Renal (80-90%), Hepatic (10%)
Side Effects: 10-15% Increase in HR, MAP, CO
Selective blockade of cardiac muscarinic receptors in the sinoatrial node

12. Intermediate Acting - NDMR
Vecuronium
Intubating Dose: 0.1mg/kg
Onset: 3-5 Minutes
Duration: Minutes
Metabolism:
Renal 15-20%, Hepatic 20-30%, Biliary 40%
Side Effects: Minimal
Rocuronium
Intubating Dose: 0.5-1mg/kg
Onset: 2-3 Minutes
Renal 10-20%, Hepatic 10-20%, Biliary 50%
Cisatricurium
Intubating Dose: 0.1mg/kg
Onset: 2-5 Minutes
Duration: Minutes
Metabolism:
Hoffman Elimination
Side Effects: Minimal

13. Short Acting- NDMR Mivacurium Intubating Dose: 0.25mg/kg
Onset: 2-3 Minutes
Duration: Minutes
Metabolism: Plasma Cholinesterase
NOT AVAILABLE IN USA

14. Train of Four Monitoring
TOF
4 total stimuli, 1 every 0.5 secs
Level of block correlates to “number of twitches”
Can still have 70% of receptors blocked with 4 twitches

15. Neuromuscular Blockade Reversal
May reverse blockade of non depolarizing muscle relaxants after patient has > 1 twitch
Anticholinesterases
Inhibit acetylcholinesterase and increase acetylcholine at neuromuscular junction
Neostigmine, Pyridostigmine, Physostigmine Edrophonium
Side Effects (Cholinergic): Bradycardia, salivation, bronchial secretions, diarrhea, increases gut motility
Pair with anticholinergic agents: Atropine, Glycopyrrolate

16. Evaluating Neuromuscular Function
Tidal Volume: > 5ml/kg
TOF: No Fade
Sustained Tetanus
Head Lift: > 180 for 5 seconds

17. Sugammadex
Newly developed reversal agent- Antagonizes steroidal neuromuscular blockers by encapsulating
Not approved in USA

18. Questions?