What is the recommended dosage of ketamine for an adult patient with no significant medical history for acute pain management or sedation?

Ketamine Dosage for Acute Pain Management and Sedation in Adults

For acute pain management in adults with no significant medical history, administer ketamine as a 0.5 mg/kg IV bolus followed by a continuous infusion of 1-2 μg/kg/min (or 0.06-0.12 mg/kg/hr), which reduces opioid requirements by approximately 22 mg morphine equivalents without increasing side effects. 1

Dosing by Clinical Context

Acute Pain Management (Emergency Department/Hospital Setting)

• Standard subanesthetic dosing: 0.3 mg/kg IV administered over 15 minutes for acute pain in adults provides analgesic efficacy comparable to morphine 1
• Alternative bolus dosing: Boluses <0.35 mg/kg can be used for severe acute pain 2
• Continuous infusion: 0.5-1 mg/kg/hr for ongoing pain control 2
• Maximum infusion rate: 0.5-2 mg/kg/hr (maximum 100 mg/hour) in ICU settings, using the lowest effective dose 1

Perioperative Pain Management

• Induction dose: 0.5 mg/kg IV after anesthesia induction 2
• Intraoperative infusion: 0.125-0.25 mg/kg/hr (maximum 0.5 mg/kg/hr) 1, 2
• Timing consideration: Discontinue infusion 30 minutes before end of surgery to prevent analgesic gap and administer a longer-acting opioid 1, 2
• Breakthrough pain in PACU: 0.5 mg/kg titrated to effect 1

Patient-Controlled Analgesia (PCA)

• PCA dosing: 1-5 mg per dose when used in IV-PCA systems 2

Route-Specific Efficacy Considerations

• IV administration: Standard route with predictable pharmacokinetics 1
• Local infiltration: Consistently demonstrates superior analgesia compared to IV administration 1
• Subcutaneous: Provides similar analgesia to IV route 1
• Intramuscular: Lacks analgesic efficacy and should be avoided 1
• Oral: Less effective than infiltration due to extensive first-pass metabolism 1

Critical Safety Monitoring Requirements

Mandatory Monitoring During Administration

• Continuous cardiac monitoring and pulse oximetry throughout ketamine infusion 1
• Regular assessment of sedation level, respiratory status, and hemodynamics 1, 2
• Maintain vascular access throughout procedure until patient is no longer at risk for cardiorespiratory depression 2
• Practitioners must be able to identify and rescue patients from unintended deep sedation or general anesthesia 2

Management of Adverse Effects

Psychotomimetic effects (dysphoria, nightmares, hallucinations) occur in 10-30% of adults, especially at higher doses:

• Prevention strategy: Co-administer benzodiazepines (e.g., midazolam) to minimize these effects 1, 3
• These effects are typically mild and transient 1

Cardiovascular effects:

• Ketamine produces dose-dependent increases in heart rate, blood pressure, and cardiac output through sympathetic stimulation 3
• Maintains cardiovascular stability through central NMDA blockade and preserved adrenal function 1
• Critical caveat: In critically ill patients with depleted catecholamine stores, the hemodynamic response may be blunted or reversed, leading to paradoxical hypotension 3

Respiratory effects:

• If hypoxemia or significant hypoventilation develops, encourage deep breathing, administer supplemental oxygen, and provide positive pressure ventilation if needed 2

Absolute and Relative Contraindications

Absolute Contraindications

• Uncontrolled cardiovascular disease 1, 2
• Pregnancy 1, 2
• Active psychosis 2
• Severe liver dysfunction 2
• High intracranial or ocular pressure 2

Special Population Considerations

Patients with cardiovascular disease:

• The European Society of Cardiology recommends avoiding ketamine in patients with ischemic heart disease, cerebrovascular disease, or hypertension 3
• In compromised patients, cardiac decompensation may result from ketamine's hemodynamic effects 3

Patients with sepsis or critical illness:

• Hemodynamic response may be blunted or reversed in these patients 3
• Despite this, ketamine causes less hypotension than etomidate in septic patients (51% vs 73%) 3

Common Pitfalls to Avoid

• Do NOT continue ketamine in the postoperative period: This increases risk of hallucinations without significantly enhancing analgesic effect 1, 2
• Avoid mixed agonist-antagonists (butorphanol, pentazocine) in combination with ketamine 1
• Do not use in patients with depleted catecholamine stores without careful consideration, as paradoxical hypotension can occur 3
• Allow sufficient time for absorption when using oral ketamine before considering supplementation 2

Advantages Over Opioids

• No respiratory depression or cardiovascular adverse events at recommended doses 1
• Lower risk of life-threatening events compared to opioids 1
• Superior alternative for patients with history of substance abuse or at risk of addiction 1
• Opioid-sparing effect: Reduces overall opioid requirements by approximately 22 mg morphine equivalents 1
• Reduces postoperative respiratory impairment and agitation in recovery 1