What is the recommended induction agent and dosage for a healthy adult patient undergoing a surgical procedure, considering options such as propofol (induction agent), etomidate (induction agent), and ketamine (induction agent), particularly in patients with cardiovascular disease or impaired respiratory function?

Recommended Induction Agents for Surgical Procedures

Primary Recommendation for Healthy Adults

For healthy adult patients (ASA I-II) undergoing elective surgery, propofol at 2-2.5 mg/kg IV is the preferred induction agent, administered slowly at approximately 40 mg every 10 seconds until loss of consciousness occurs. 1

Dosing Algorithm by Patient Population

Healthy Adults (ASA I-II, Age <55)

• Propofol 2-2.5 mg/kg IV administered as 40 mg every 10 seconds 1
• Avoid rapid bolus administration to minimize cardiovascular depression 1
• Loss of consciousness occurs in less than one minute with duration of approximately 5 minutes 2

Elderly, Debilitated, or ASA III-IV Patients

• Propofol 1-1.5 mg/kg IV administered as 20 mg every 10 seconds 1
• Slower administration is critical as rapid bolus increases likelihood of hypotension, apnea, airway obstruction, and oxygen desaturation 1
• These patients demonstrate reduced clearance and higher blood concentrations requiring dose reduction 1

Cardiac Surgery Patients

• Propofol is preferred over benzodiazepines for post-cardiac surgery sedation, resulting in 1.4 hours shorter time to extubation (95% CI: -2.2 to -0.6 hours) 3
• Propofol 1-2 mg/kg for induction in neurosurgical patients using slower boluses of 20 mg every 10 seconds 1
• Anticholinergic agents should be administered when increases in vagal tone are anticipated, as propofol reduces sympathetic activity and resets baroreceptor reflexes 1

Alternative Agents for Specific Clinical Scenarios

Hemodynamically Unstable or Trauma Patients

Ketamine 1-2 mg/kg IV is the first-line induction agent alongside etomidate for hemodynamically unstable patients, with the lower dose (1 mg/kg) used in cardiovascular compromise. 4, 5, 6

Ketamine Advantages:

• Preserves blood pressure through endogenous catecholamine release, critical in hypovolemic or shocked patients 4
• Causes bronchodilation, beneficial in chest injuries, aspiration risk, or reactive airway disease 4
• Safe in head-injured patients when used with controlled mechanical ventilation, as historical concerns about increased intracranial pressure have been refuted 4, 5

Critical Ketamine Caveats:

• Paradoxical hypotension can occur in critically ill patients with depleted catecholamine stores (prolonged shock, severe cardiogenic shock, adrenal exhaustion) 4, 5
• Always have vasopressors immediately available during RSI 5, 6
• Increases upper airway secretions; consider atropine or glycopyrrolate pretreatment in aspiration-risk patients 4
• Must be administered BEFORE neuromuscular blocking agent to prevent awareness during paralysis 4, 5

Etomidate Considerations

The Society of Critical Care Medicine suggests no difference between etomidate and other induction agents (ketamine, propofol) regarding mortality or hypotension incidence (OR 1.17; 95% CI: 0.86-1.60). 3

• Etomidate 0.2-0.3 mg/kg provides favorable hemodynamic profile 3
• Despite causing transient adrenal enzyme inhibition (11-beta-hydroxylase), no evidence demonstrates this causes negative clinical outcomes 3, 6
• Corticosteroid administration following etomidate is not recommended 6
• Explicitly contraindicated in pediatric septic shock 4

Cardiovascular Disease Patients

Propofol in Cardiac Disease:

• Propofol causes dose-dependent decreases in preload and afterload, with magnitude proportional to blood and effect-site concentrations 1
• In patients with cardiac disease, especially after high or repeated doses, propofol may be more depressant than thiopental, resulting in imbalance of myocardial oxygen demand and supply 7
• Systolic and diastolic blood pressure decrease approximately 20-30% during induction with minimal heart rate change 2

Ketamine in Heart Failure:

• The Society of Critical Care Medicine found no mortality difference between ketamine and etomidate in critically ill patients (OR 0.95; 95% CI: 0.72-1.25) 5
• Ketamine produces dose-dependent increases in heart rate, blood pressure, and cardiac output through sympathetic stimulation 3
• Use is potentially dangerous in ischemic heart disease, cerebrovascular disease, or hypertension; should be avoided in these populations 3

Combination Approach for Hemodynamic Stability:

• Ketamine 0.75 mg/kg + propofol 1 mg/kg (ketofol) provides hemodynamic stability comparable to etomidate 0.2 mg/kg + propofol 1 mg/kg (etofol) in elderly patients 8
• Both combinations effectively prevent hemodynamic changes due to propofol administration alone 8
• Etomidate provides more stable hemodynamic parameters than propofol alone, particularly avoiding vasodilation-induced blood pressure drops 9

Impaired Respiratory Function

Propofol Respiratory Effects:

• Apnea is common during induction 2
• Respiratory depression should not cause major concern in otherwise healthy patients 2
• In elderly, debilitated, or ASA III-IV patients, rapid bolus significantly increases risk of apnea and oxygen desaturation 1

Ketamine Respiratory Advantages:

• Ketamine preserves respiratory drive and causes bronchodilation, making it superior for patients with reactive airway disease or chest injuries 3, 4
• Unlike propofol or thiopental, ketamine does not cause significant respiratory depression 3

Critical Pitfalls to Avoid

• Never use rapid bolus propofol in elderly, debilitated, or ASA III-IV patients as this dramatically increases cardiorespiratory depression risk 1
• Always administer sedative-hypnotic induction agent when neuromuscular blocking agent is used, even in hemodynamically unstable patients with depressed consciousness 5
• Post-intubation hypotension is common with all agents and associated with increased mortality, prolonged ICU stays, and organ dysfunction; have vasopressors immediately available 5, 6
• Peri-intubation hypotension rates: 18.3% with ketamine versus 12.4% with etomidate in emergency department RSI 6
• Propofol causes pain on injection; in pediatric patients, pretreating veins with lidocaine or using antecubital/larger veins minimizes discomfort 1

Maintenance Considerations

• Propofol maintenance infusion rates of 50-100 mcg/kg/min in adults optimize recovery times 1
• Morphine premedication (0.15 mg/kg) with nitrous oxide decreases necessary propofol maintenance rates compared to non-narcotic premedication 1
• For critically ill mechanically ventilated patients, propofol or dexmedetomidine are preferred over benzodiazepines for improved short-term outcomes including ICU length of stay and delirium reduction 3