Why is ketamine beneficial as an induction agent in Chronic Obstructive Pulmonary Disease (COPD) patients requiring Rapid Sequence Intubation (RSI)?

Why Ketamine is Beneficial as an Induction Agent in COPD Requiring RSI

Ketamine provides bronchodilation through direct smooth muscle relaxation in COPD patients undergoing RSI, making it superior to propofol (which causes myocardial depression) and thiopental (which causes bronchoconstriction), though it requires anticholinergic premedication to manage increased airway secretions and carries paradoxical hypotension risk in severely ill patients. 1

Primary Bronchodilatory Advantage

• Ketamine causes direct bronchodilation, which is particularly beneficial in COPD patients who already have compromised airway mechanics and reactive airway disease 1, 2
• During one-lung ventilation in COPD patients undergoing thoracic surgery, continuous ketamine infusion significantly increased PaO2/FiO2 ratios and decreased shunt fraction (Qs/Qt) at 60 minutes compared to saline controls 3
• This bronchodilatory effect makes ketamine fundamentally different from propofol (which causes profound myocardial depression and vasodilation) and thiopental (which causes severe bronchoconstriction in reactive airway disease) 1

Comparative Safety Profile

• The Society of Critical Care Medicine found no mortality difference between ketamine and etomidate in critically ill patients undergoing RSI, despite etomidate causing transient adrenal suppression 4, 1
• A 2025 meta-analysis of 23,926 patients confirmed no significant difference in 30-day survival between etomidate and ketamine (OR = 0.92,95% CI: 0.68-1.24 for RCTs) 5
• Etomidate was associated with significantly higher incidence of adrenal insufficiency (OR = 2.43,95% CI: 1.67-3.53), though this has not translated to worse clinical outcomes 5

Critical Dosing Algorithm for COPD Patients

Use ketamine 1 mg/kg IV (lower end of dosing range) in COPD patients with any hemodynamic compromise, chronic cor pulmonale, or signs of right ventricular dysfunction to minimize hypotension risk while maintaining adequate sedation. 1

• Administer anticholinergic premedication (glycopyrrolate 0.2 mg or atropine 0.5 mg) 3-5 minutes before ketamine to prevent secretion-related complications 1
• Standard ketamine dosing is 1-2 mg/kg IV, but COPD patients with cardiovascular compromise should receive the lower 1 mg/kg dose 1, 2

Essential Pitfalls and Precautions

Paradoxical Hypotension Risk

• Despite ketamine's sympathomimetic properties, paradoxical hypotension occurs in critically ill COPD patients with depleted catecholamine stores from prolonged respiratory distress, chronic hypoxemia, or concurrent sepsis 1, 6
• Never assume ketamine guarantees hemodynamic stability—COPD patients with chronic hypoxemia, cor pulmonale, or concurrent sepsis may have exhausted endogenous catecholamine stores 1
• Always have vasopressors immediately available during RSI with any induction agent, as post-intubation hypotension is common and associated with increased mortality 2, 6

Secretion Management

• Ketamine significantly increases upper airway secretions in COPD patients, which can worsen dyspnea and requires aggressive suctioning capability 1
• COPD patients already have compromised airway clearance mechanisms, making the secretion burden from ketamine particularly problematic without anticholinergic pretreatment 1

Preoxygenation Requirements

• Ensure adequate preoxygenation before ketamine administration, as COPD patients have reduced functional residual capacity and desaturate rapidly despite ketamine's theoretical preservation of respiratory drive 1
• The Society of Critical Care Medicine recommends preoxygenation with high-flow nasal oxygen (HFNO) when laryngoscopy is expected to be challenging, or noninvasive positive pressure ventilation (NIPPV) in patients with severe hypoxemia (PaO2/FiO2 < 150) 4

Hemodynamic Considerations in Real-World Practice

• Ketamine was associated with higher post-intubation vasopressor requirements compared to etomidate (OR = 0.71,95% CI: 0.53-0.96) in the 2025 meta-analysis, though this may reflect selection bias toward more unstable patients 5
• Peri-intubation hypotension rates in emergency department RSI were 18.3% with ketamine versus 12.4% with etomidate, though the clinical significance of these differences remains unclear 2
• The Society of Critical Care Medicine found mixed results regarding peri-intubation hemodynamics between etomidate and ketamine, with no difference in duration of vasopressor use 4

Alternative Airway Strategies with Ketamine

• Ketamine enables delayed sequence intubation (DSI) in agitated COPD patients, allowing airway preparation and preoxygenation before paralysis 7
• Ketamine-only breathing intubation (without paralytic) facilitates ETI while the patient continues spontaneous breathing, which may be advantageous in COPD patients with difficult airways 7