Neuromuscular Blocking Agents (NMBA)
🎯 Indications
- Facilitate
endotracheal intubation
- Improve
surgical conditions (immobility)
- Facilitate
mechanical ventilation
⚙️ Classification
1. Depolarizing
- Succinylcholine
2. Nondepolarizing
- Steroidal:
rocuronium, vecuronium
- Benzylisoquinolinium:
atracurium, cisatracurium, mivacurium
🚑 Drug selection
(practical)
🔥 Rapid sequence
intubation (RSI)
- 1st
line: succinylcholine
- Alternative:
rocuronium 1.2 mg/kg
⏱️ Short procedure (<30 min)
- succinylcholine
- หรือ rocuronium + sugammadex
⏳ Long procedure
- rocuronium
/ vecuronium / cisatracurium
🧠 Special cases
- renal/hepatic
failure →
cisatracurium / atracurium
- neuromuscular
disease →
careful titration / avoid SCh
⚠️ Factors affecting NMBA
response
👤 Patient factors
- Neuromuscular
disease
- MG: ↑ sensitivity
nondepolarizing / ↓
response SCh
- Burns
(>48h) → avoid
SCh (hyperkalemia)
- Elderly
→ prolonged effect
- Obesity
→ dose adjustment
⚡ Physiologic factors
- Hypothermia
→ prolonged block
- Acidosis
→ ↑ effect
- Electrolytes:
- ↑Mg → ↑
block
- ↓K → prolonged block
- ↑Ca → ↓
block
💊 Drug interactions
- Volatile
anesthetics → ↑ NMBA effect
- Aminoglycoside
→ ↑ block
- Lithium
→ prolonged block
- Antiseizure
drugs → resistance
💉 Key drugs
⚡ Succinylcholine
- Dose:
1–1.5 mg/kg
- Onset:
30–60 sec
- Duration:
7–12 min
ข้อดี
- fastest
onset → RSI
ข้อเสียสำคัญ
- Hyperkalemia
- Malignant
hyperthermia trigger
- Myalgia
- Bradycardia
- ↑ ICP / IOP
💪 Rocuronium
- Dose:
0.6 mg/kg (RSI: 1.2 mg/kg)
- Duration:
30–70 min
ข้อดี
- ใช้แทน SCh ใน RSI
- hemodynamic
stable
💉 Vecuronium
- Onset
ช้ากว่า rocuronium
- duration
25–50 min
⚖️ Cisatracurium
- Organ-independent
metabolism (Hofmann)
- เหมาะใน renal/hepatic failure
🎯 ระดับ blockade
|
Level |
TOF |
|
Moderate |
1–3 twitches |
|
Deep |
0 twitches |
👉 ปกติ aim:
moderate blockade
⚠️ Complication: Residual block
- TOFR
< 0.9 → ↑ risk:
- airway
obstruction
- aspiration
- hypoxemia
- ↑ pulmonary complications
📊 incidence ~ 40%
(intermediate NMBA)
🧪 Monitoring (สำคัญมาก)
- ใช้ quantitative TOF monitor
- Target
ก่อน extubation:
- TOFR
≥ 0.9 (ideal ≥0.95)
🔄 Reversal
1. Neostigmine
- ใช้เมื่อ TOF count = 4
- Dose:
20–50 mcg/kg
- ต้องให้ glycopyrrolate
⚠️ ใช้ไม่ได้ใน deep
block
2. Sugammadex (preferred)
- ใช้กับ rocuronium / vecuronium
|
Depth |
Dose |
|
TOF 2–4 |
2 mg/kg |
|
Deep |
4 mg/kg |
|
Emergency |
16 mg/kg |
ข้อดี
- เร็ว + reliable
- ↓ residual block
ข้อเสีย
- ราคาแพง
- anaphylaxis
/ bradycardia
🧠 Key Clinical Pearls
- RSI → SCh หรือ high-dose
rocuronium
- Avoid
SCh:
- burns
>48h
- neuromuscular
disease
- hyperkalemia
risk
- Monitor
ทุก case →
TOFR ≥0.9 ก่อน extubation
- Neostigmine:
- ใช้เฉพาะ shallow block
- Sugammadex:
- best
for deep block / rapid reversal
- Residual
block = major cause morbidity
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