Anesthesia Induction, Sedation, and Muscle Relaxation Dosing
Induction of General Anesthesia
For standard induction in healthy adults under 55 years, administer propofol 2-2.5 mg/kg IV with fentanyl 5 mcg/kg IV, followed by rocuronium 0.6 mg/kg IV for neuromuscular blockade. 1
Standard Adult Induction Protocol (ASA I-II, <55 years)
- Opioid first: Fentanyl 5 mcg/kg IV (or 0.1 mg for average adult) 1, 2
- Hypnotic: Propofol 2-2.5 mg/kg IV, titrated approximately 40 mg every 10 seconds until loss of consciousness 3
- Muscle relaxant: Rocuronium 0.6 mg/kg IV for intubation 1
- Alternative muscle relaxant: Succinylcholine 1 mg/kg IV if rapid sequence induction needed 1
Elderly or Debilitated Patients (>55 years, ASA III-IV)
Reduce all induction doses by approximately 50% in elderly patients to prevent severe cardiovascular depression. 3
- Fentanyl: 0.1 mg (same as younger adults) 2
- Propofol: 1-1.5 mg/kg IV, administered as 20 mg every 10 seconds 3
- Muscle relaxant: Rocuronium 0.6 mg/kg IV (same dose, but expect longer onset) 1
- Critical: Never use rapid bolus in elderly patients due to risk of severe hypotension and apnea 3
Co-Induction Technique (Reduces Propofol Requirements)
Pre-administering midazolam 2 mg IV reduces propofol requirements by approximately 30% and decreases awareness risk. 4
- Midazolam: 0.03 mg/kg (approximately 2 mg) given 2-3 minutes before propofol 5, 4
- Propofol: Reduced to 1.5-2 mg/kg when midazolam used 4
- Fentanyl: 0.1 mg IV 2
- Advantage: Lower propofol dose reduces bradycardia risk and cost 4
- Caution: Midazolam doses >5 mg may delay discharge by 20 minutes in outpatient settings 4
Maintenance of Anesthesia
Propofol Infusion for Maintenance
Maintain anesthesia with propofol infusion at 50-100 mcg/kg/min in adults to optimize recovery times. 3
- Initial rate: 100-150 mcg/kg/min, then titrate down 3, 6
- Target rate: 50-100 mcg/kg/min for optimal recovery 3
- With nitrous oxide: Can use lower propofol rates (50-75 mcg/kg/min) 3
- Bolus dosing: Give 25-50 mg increments for inadequate depth 3
Opioid Maintenance
Administer fentanyl 2 mcg/kg boluses when systolic blood pressure or heart rate increases >20% from baseline. 1, 7
- Fentanyl boluses: 2 mcg/kg (or 0.5 mcg/kg per some protocols) as needed 1, 7
- Alternative: Remifentanil infusion 0.05-0.3 mcg/kg/min for continuous analgesia 8
Muscle Relaxant Maintenance
Give rocuronium 0.2 mg/kg IV for maintenance doses when neuromuscular monitoring shows recovery. 1
- Rocuronium maintenance: 0.2 mg/kg IV as needed 1
- Monitoring: Use train-of-four monitoring to guide redosing 1
Sedation (Non-Intubated Procedures)
Moderate Sedation with Midazolam
For moderate sedation in healthy adults <60 years, titrate midazolam 1-2.5 mg IV over 2 minutes, waiting 2 minutes between doses, with maximum total dose of 5 mg. 5
- Initial dose: 1-2.5 mg IV over at least 2 minutes 5
- Wait time: 2 minutes minimum between increments to assess effect 5
- Maximum: 5 mg total dose usually sufficient 5
- Endpoint: Slurred speech indicates adequate sedation 5
Moderate Sedation in Elderly (>60 years)
In elderly patients, start with 1 mg midazolam IV over 2 minutes, with maximum increments of 1 mg and total dose not exceeding 3.5 mg. 5
- Initial dose: No more than 1.5 mg over 2 minutes 5
- Increments: Maximum 1 mg over 2 minutes 5
- Maximum total: 3.5 mg 5
- With CNS depressants: Reduce dose by at least 50% 5
Deep Sedation with Propofol
For deep sedation, use propofol loading dose of 0.5-4 mg IV over several minutes, followed by infusion at 1-7 mg/hr (0.02-0.10 mg/kg/hr). 5
- Loading dose: 0.01-0.05 mg/kg (0.5-4 mg typical adult) slowly or over several minutes 5
- Repeat loading: Every 10-15 minutes until adequate sedation 5
- Maintenance infusion: 0.02-0.10 mg/kg/hr (1-7 mg/hr) 5
- Titration: Use lowest rate producing desired sedation level 5
Intubation Without Muscle Relaxants
Intubation without muscle relaxants requires propofol 2 mg/kg with remifentanil 1-1.5 mcg/kg, but expect 10% unacceptable intubation conditions and prolonged apnea. 1, 8
Low-Dose Remifentanil Approach
- Propofol: 2 mg/kg IV 1, 8
- Remifentanil: 1-1.5 mcg/kg IV 8
- Apnea duration: Approximately 4.5 minutes 1
- Failure rate: 10% unacceptable intubation conditions 1, 8
High-Dose Remifentanil Approach (Not Recommended)
- Propofol: 2 mg/kg IV 1, 8
- Remifentanil: 2 mcg/kg IV 1, 8
- Apnea duration: 8 minutes (substantially longer) 1, 8
- Problem: Still 10% failure rate despite longer apnea 1, 8
Ultra-High Dose (Avoid in Routine Practice)
- Remifentanil: 4 mcg/kg provides conditions comparable to succinylcholine 1, 8
- Major problems: Severe hypotension and 12.8 minutes apnea 1, 8
- Conclusion: Not recommended for routine use 1, 8
Critical Safety Considerations
Laryngospasm Management
If laryngospasm occurs with failed mask ventilation, immediately administer succinylcholine 1 mg/kg IV (or 4 mg/kg IM if no IV access). 1, 9
- First-line: Succinylcholine 1 mg/kg IV 1
- Pediatrics <3 years: Add atropine 0.02 mg/kg to prevent bradycardia 1
- Alternative: Rocuronium 0.1-0.2 mg/kg if adequate anesthesia depth 1
- Do not: Give additional propofol hoping to break laryngospasm—this wastes critical time 9
Muscle Relaxant Use for Intubation
Muscle relaxants are strongly recommended for tracheal intubation to optimize conditions and reduce airway trauma. 1
- Evidence: Muscle relaxants significantly improve intubation conditions compared to propofol/opioid alone 1
- Safety: Testing mask ventilation before muscle relaxant is optional but adds time 1
- Reality: Only 2 cases per 100 difficult intubations required awakening the patient 1
Reversal Considerations
Have sugammadex immediately available when using rocuronium, as it provides faster and more reliable reversal than waiting for succinylcholine to wear off. 1