What medications are used for intubation and sedation maintenance in anesthesia?

Medications for Intubation and Sedation Maintenance in Anesthesia

Induction Agents for Intubation

Propofol is the principal intravenous induction agent for intubation, typically dosed at 2-2.5 mg/kg, offering rapid onset within 40 seconds and superior recovery profiles compared to alternatives 1, 2.

• Propofol produces anesthesia through positive modulation of GABA-A receptors, with blood-brain equilibration occurring within 1-3 minutes 1
• For elderly patients (>60 years) or ASA physical status 3 or above, reduce propofol dose to 25 mcg/kg/min to minimize cardiovascular depression 2
• Propofol causes arterial hypotension (sometimes >30% decrease) and apnea in most patients: <30 seconds in 7%, 30-60 seconds in 24%, and >60 seconds in 12% of adults 1
• In hemodynamically unstable patients, etomidate (10-20 mg) is preferred over propofol due to better cardiovascular stability 2, 3

Ketamine (0.5-2 mg/kg) serves as an alternative induction agent with unique sympathomimetic properties that maintain hemodynamic stability 4, 2, 3.

• Ketamine is particularly valuable in hypotensive patients or those with traumatic brain injury, contrary to historical concerns about increased intracranial pressure 4, 3
• At lower doses, ketamine provides mild sedative and analgesic effects; high doses are required for complete anesthesia as monotherapy 4
• The sympathomimetic effects can mitigate hypotension but may be disadvantageous in severe cardiac disease or post-cardiac arrest patients 4

Analgesic Adjuncts for Intubation

Fentanyl (1-2 mcg/kg or 25-100 mcg bolus) should be administered as first-line analgesia 3 minutes before induction to blunt sympathetic response to laryngoscopy 4, 2, 5, 3.

• High-dose fentanyl effectively attenuates the pathophysiologic response to intubation in traumatic brain injury patients 3
• Fentanyl has a duration of 1-4 hours and potent analgesic effects with anti-shivering properties 4
• In pediatric patients, concomitant fentanyl with propofol may result in serious bradycardia requiring careful monitoring 1

Neuromuscular Blocking Agents

Rocuronium (0.6-1.2 mg/kg) is the preferred neuromuscular blocker for intubation, providing excellent intubating conditions within 60 seconds 6, 7, 8.

• The dose giving 95% probability of successful intubation at 60 seconds is 1.04 mg/kg (95% CI: 0.76-1.36 mg/kg) 7
• Rocuronium at 0.6 mg/kg provides intubating conditions similar to succinylcholine 1.0 mg/kg at 1 minute when used with propofol and fentanyl 8
• Clinical duration after 0.6 mg/kg is approximately 30-45 minutes, which may delay neurological examinations in traumatic brain injury patients 6, 3
• In obese patients, dose rocuronium based on actual body weight 6

Succinylcholine (1.0-1.5 mg/kg) remains an alternative for rapid sequence intubation with faster onset but more contraindications 5, 8.

Sedation Maintenance Post-Intubation

For normotensive/hypertensive patients, propofol infusion (25-300 mcg/kg/h or 0.5-5 mcg/kg/h) combined with fentanyl (25-300 mcg/h) is the preferred maintenance regimen 4, 3.

• Propofol is preferred over benzodiazepines due to shorter half-life and lower risk of delirium 4
• Small, frequent doses minimize hemodynamic side-effects and should be titrated against physiological variables 4
• Continuous benzodiazepine infusions should be avoided whenever possible 4

For hypotensive patients or those with hemodynamic instability, midazolam (boluses of 2-5 mg) combined with fentanyl or ketamine alone should be used instead of propofol 4, 2, 3.

• Midazolam dose should be reduced by at least 20% in elderly patients (>60 years) or ASA physical status 3 or above 2
• Boluses of midazolam are preferred over continuous infusions except when controlling active seizures 4

Dexmedetomidine (infusion rates 4-16 mcg/kg/min) is useful during the recovery/weaning phase but inadequate as sole agent for deep sedation 4, 9.

• Dexmedetomidine must be combined with a GABA agonist to provide amnesia during neuromuscular blockade 4, 9
• It is most effective during and after rewarming while patients are in the ventilator weaning phase 4
• Dexmedetomidine causes hypotension in approximately 21% and bradycardia in up to 10% of patients 9
• When patients have severe ventilator dyssynchrony or require deep sedation, dexmedetomidine is often ineffective and propofol is preferred 4

Critical Safety Considerations

Waveform capnography must be used to confirm correct tracheal tube placement, with 100% sensitivity and specificity in ventilated patients 2.

• Confirmation should be repeated each time the patient is moved 4
• Pulse oximetry is essential for all sedation procedures 2

Emergency support equipment must be immediately available, including suction, advanced airway equipment, positive pressure ventilation, and a functional defibrillator 4, 2.

• At least one individual capable of establishing a patent airway and providing positive pressure ventilation must be present 4
• A team member must have skills for intravascular access, chest compressions, and advanced life support 4

All induction agents ablate sympathetic tone, resulting in vasodilation, hypotension, bradycardia, and potentially low cardiac output 4.

• Fluid deficits should be corrected prior to propofol administration 1
• In patients where additional fluid therapy is contraindicated, elevation of lower extremities or pressor agents may offset hypotension 1

Post-Intubation Ventilation Management

Lung-protective ventilation strategies should be implemented immediately, targeting normocapnia with end-tidal CO2 of 4.0-4.5 kPa 4.

• Transport ventilators are preferred over hand ventilation to decrease hyperventilation risk and free up team members 4
• Positive end-expiratory pressure may need reduction or removal in hypovolemic patients 4

4, 2, 9, 1, 6, 10, 5, 7, 8, 3