SUCCINYLCHOLINE 

 1. INTRODUCTION

Succinylcholine (Suxamethonium) is a depolarizing neuromuscular blocking agent (NMBA) used for:

✔ Most rapid onset among all NMBAs
✔ Shortest duration (ideal for emergency airway control)

 2. MECHANISM OF ACTION

 Depolarizing Neuromuscular Block

• Structurally = 2 acetylcholine molecules
• Acts on nicotinic receptors (Nm) at NMJ

Steps:

1. Binds to ACh receptor
2. Causes persistent depolarization
3. Prevents repolarization → paralysis

 Phases of Block

 3. PHARMACOKINETICS

✔ Not metabolized at NMJ → diffuses back to plasma

 4. DOSE (ICU / RSI)

Adult RSI dose:

• 1–1.5 mg/kg IV

Special situations:

• Obese → dose based on total body weight
• Pediatric → 2 mg/kg IV

 5. INDICATIONS IN ICU

 Primary Use:

• Rapid Sequence Intubation (RSI)

Other uses:

• Emergency airway control
• Short procedures requiring paralysis

 6. ADVANTAGES (WHY STILL USED?)

✔ Fastest onset (gold standard for crash airway)
✔ Excellent intubating conditions
✔ Short duration → recovery if intubation fails

 7. ADVERSE EFFECTS 

 1. HYPERKALEMIA 

• K⁺ increase: +0.5 mEq/L (normal patients)
• Can be massive in high-risk states

 High-risk conditions:

• Burns (>24–48 hrs)
• Crush injury
• Denervation (stroke, spinal cord injury)
• Neuromuscular disease (e.g., Duchenne muscular dystrophy)
• Prolonged immobilization

 Mechanism: Upregulation of extrajunctional ACh receptors → massive K⁺ efflux

 2. MALIGNANT HYPERTHERMIA

• Trigger in susceptible patients
• Associated with mutation in ryanodine receptor

 Treat with:

• Dantrolene

 3. BRADYCARDIA

• Especially in:
• Children
• Repeated doses

 Mechanism: Muscarinic stimulation

 4. FASCICULATIONS

• Muscle pain (post-op myalgia)
• Increased ICP, IOP, intragastric pressure

 5. PROLONGED APNEA

• Due to:
• Pseudocholinesterase deficiency
• Liver disease
• Pregnancy

 8. CONTRAINDICATIONS 

 ABSOLUTE:

• Hyperkalemia
• Neuromuscular disease
• Major burns (>48 hrs)
• Malignant hyperthermia history

 RELATIVE:

• Raised ICP
• Open globe injury
• Severe acidosis

 9. SPECIAL ICU CONSIDERATIONS

 In ICU patients:

• Avoid in:
• Sepsis with prolonged immobilization
• ICU-acquired weakness

 RSI COMPARISON 

 Current trend:

• Rocuronium + Sugammadex replacing succinylcholine in many ICUs

10. PSEUDOCHOLINESTERASE DEFICIENCY

Types:

• Genetic
• Acquired (liver disease, pregnancy)

Diagnosis:Dibucaine number ↓

Clinical:

• Prolonged apnea → ventilatory support