Emergence from General Anesthesia

Emergence from General Anesthesia

🎯 Core concept

• Emergence = passive recovery หลังหยุด anesthetic
• เป้าหมาย:
• return consciousness
• regain airway reflexes
• stable ventilation + hemodynamics

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⚙️ Preparation (เริ่มก่อนจบผ่าตัด)

🔻 1. Stop anesthetic agents (ต้อง “plan timing”)

• ไม่มี reversal สำหรับ GA drugs
• ต้องคำนวณตาม:
• agent type
• duration
• dose

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🌬️ Inhalation agents – ปัจจัยที่กำหนด recovery

• low solubility → recovery เร็ว (desflurane > sevoflurane > isoflurane)
• ↑ minute ventilation → washout เร็ว
• ↑ fresh gas flow → ลด rebreathing
• duration ยาว → accumulation → recovery ช้า

👉 N₂O:

• washout เร็ว → ช่วย volatile ออกเร็ว (second gas effect)
• แต่ → diffusion hypoxia → ต้องให้ O₂

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💉 IV agents

• Recovery ขึ้นกับ:
• redistribution (bolus)
• metabolism/elimination (infusion)

Key points

• Propofol → recovery เร็ว (context-sensitive half-time ต่ำ)
• Fentanyl → recovery ช้า (สะสม)
• Remifentanil → ultra-short

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⚠️ Drug synergy → delayed emergence

• opioids + propofol + benzo + dexmedetomidine
• ↓ ventilation → ↑ CO₂ → sedation

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💪 Neuromuscular block (critical step)

🎯 ต้องทำก่อน extubation

• TOFR ≥ 0.9
• reverse (neostigmine / sugammadex)

👉 residual block →

• hypoventilation
• airway collapse
• aspiration

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🧠 Signs of recovery (sequence)

1.       spontaneous breathing (initially irregular)

2.       airway reflexes (gag, swallow)

3.       muscle tone return

4.       eye movement / corneal reflex

5.       follow commands

6.       eye opening (late sign)

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💊 Before emergence ต้อง ensure

• analgesia adequate
• antiemetic given
• communication with surgical team

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🚑 Airway management during emergence

🫁 Extubation criteria (concept)

• adequate ventilation
• TOFR ≥ 0.9
• hemodynamically stable
• awake / obey commands

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🧠 Special technique

• Remifentanil extubation
• ลด coughing (neuro/eye surgery)

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⚠️ Postpone extubation ถ้า:

• respiratory failure
• hemodynamic instability
• airway edema
• residual weakness

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⚠️ Complications (สำคัญมากใน OR)

🌬️ Airway / respiratory

• Residual NMBA → hypoventilation
• apnea → opioids / residual block
• laryngospasm
• bronchospasm
• negative pressure pulmonary edema

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❤️ Hemodynamic

• hypertension / tachycardia
• pain / agitation / sympathetic surge

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🧠 Neurologic

• delayed emergence
• emergence agitation (Stage II)

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🌡️ Other

• hypothermia → delayed drug metabolism
• pain → agitation / sympathetic surge

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🧠 Key Clinical Pearls

• Emergence = highest complication risk phase
• ต้อง:
• plan drug stop timing
• ensure TOFR ≥ 0.9
• optimize ventilation + analgesia
• Residual NMBA = major preventable cause morbidity
• N₂O:
• ให้ O₂ ป้องกัน diffusion hypoxia
• Emergence agitation:
• think pain / hypoxia / NMBA / drugs

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🚨 Practical checklist (ใช้จริงใน OR)

ก่อนหยุดยา

• ↓ volatile / stop TIVA
• ↑ fresh gas flow
• optimize ventilation

ก่อน extubation

• TOFR ≥ 0.9
• spontaneous breathing adequate
• hemodynamic stable
• analgesia adequate

หลัง extubation

• monitor airway / SpO₂
• manage pain
• watch:
• laryngospasm
• hypoventilation

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