Ch. 22: Neuromuscular Blocking Agents

Question 1

NMBA Physiology

Answer 1

• Cholinergic nicotonic receptor postsynaptic
• ACH in presynaptic cell
• AcetylCholinesterase and reuptake clear the synapse.
• Succinylcholine is a depolarizer.
• Rocuronium & Vecuronium are non-depolarizing and compete with ACh for the receptor.
• Neostigmine, edrophonium and pyridostigmine inhibit ACHE
• Sugammadex is a Rocuronium reversal agent.

Question 2

Succinylcholine

Answer 2

1.5 mg/kg 45 second onset 6-10 min duration.

• SCh is 2 ACH connected by Ester
• Stimulates all Nicotinic and muscarinic cholinergic receptors. Parasympathetic and sympathetic.
• Broken down by PseudoCholinesterase in plasma and liver. Thus bigger doses given for RSI.
• Repeat doses can cause bradycardia, esp kids

Question 3

Succinylcholine Contraindications

Answer 3

• Personal or FH of malignant hyperthermia

Question 4

SuccinylCholine Dose

Answer 4

• 1.5mg/kg normally.
• If poor circulation 2mg/kg
• IM 4mg/kg but will be slower incomplete onset requiring BVM.
• If just estimating the weight it’s safer to go higher than lower.
• Age less than 10 2mg/kg. Less than 1 year often give atropine along with.

Question 5

SuccinylCholine Adverse Effects

Answer 5

• Fasciculations: May cause increased ICP!
• Hyperkalemia: In upregulated immature ACH receptors.
  
  • BURNS after 3 to 5 days.
  • Denervation after 3 days: SCI, stroke, GBS, ALS and MS
  • Crush injury 3 days to 6 months.
  • Sepsis: After 3 days.
  • Myopathy: Esp kids w unknown heriditary myopathy.
  • Hyperkalemia: Only ESRD, AKI w arrhythmia.
• Bradycardia: Multiple doses
• Prolonged NMB.
  
  • Acquired PCHE deficiency liver disease, cocaine use, pregnancy, burns, BCP, Reglan, bambuerol or esmolol.

Question 6

Malignant Hyperthermia

Succinylcholine

Answer 6

TREATMENT:

• Dantrolene 2.5 mg/kg IV q 5 min. Max 10mg/kg till muscle regidity improved.
• Monitor K, ABG

Signs:

• Muscle Rigidity
• Autonomic instability
• Hypoxia
• Hypotension
• Lactic acidosis
• Hyperkalemia
• Myoglobinemia
• DIC
• Hyperthermia LATE!!

Question 7

Trismus/Masseter Muscle Spasm

SuccinylCholine

Answer 7

• Treat with Nondepolarizing NMBA
• Consider underlying Malignant Hyperthermia

Question 8

Competitive Neuromuscular Blocking Agents

Rocuronium & Vecuronium

Answer 8

Rocuronium

• 1-1.2 mg/kg
• 60 sec onset
• 40-60 min duration

Vecuronium

• 0.01 mg/kg prime 3 min 0.15 mg/kg GO
• 75-90 sec onset
• 60-75 sec duration

Question 9

Competitive Neuromuscular Blocking Agents

Pharmacology

Answer 9

• Block one or both alpha subunits of receptor
• ACHE inhibitors cause reacumulation of ACH
  
  • Neostigmine 0.06 to 0.08 mg/kg
  • Atropine 0.01mg/kg to prevent the excessive salivation and nausea of neostigmine.
• Sugammadex i Rocuronium reversal.

Question 10

Competitive NMBAs

Indications & ContraIndications

Answer 10

• Myasthenia patients may have longer paralysis

Question 11

Competitive NMBA

Dosage

Answer 11

• Rocuronium 1 to 1.2 mg/KG
  
  • Onset 60 seconds
• Vecuronium Priming 0.01 mg/kg
  
  • 3 min later 0.15mg/kg.
• For ongoing paralysis
  
  • Vecuronium 0.1mg/kg
  • Pancuronium 0.1mg/kg

Question 12

Competitive NMBA

Adverse Effects

Answer 12

• Pancuronium tachycardia.
• Competitive are slower and longer than SCh