What are the guidelines for using ketamine (Ketamine) in medical settings?

Ketamine Guidelines for Medical Use

FDA-Approved Indications

Ketamine is FDA-approved as a sole anesthetic agent for diagnostic and surgical procedures not requiring skeletal muscle relaxation, for induction of anesthesia prior to other general anesthetics, and as a supplement to other anesthetic agents. 1

• Must be administered by or under the direction of physicians experienced in general anesthetics, airway maintenance, and ventilation 1
• Emergency airway equipment must be immediately available 1
• Continuous vital sign monitoring is mandatory 1

Dosing by Route of Administration

Intravenous Induction

• Initial dose: 1-4.5 mg/kg IV, with 2 mg/kg being the average dose producing 5-10 minutes of surgical anesthesia within 30 seconds 1
• Administer slowly over 60 seconds to avoid respiratory depression and enhanced vasopressor response 1
• Alternative: IV infusion at 0.5 mg/kg/min 1
• The 100 mg/mL concentration must be diluted before IV administration 1

Intramuscular Induction

• Initial dose: 6.5-13 mg/kg IM, with 9-13 mg/kg producing surgical anesthesia within 3-4 minutes, lasting 12-25 minutes 1

Maintenance Anesthesia

• Repeat increments of one-half to full induction dose as needed 1
• Slow microdrip infusion: 0.1-0.5 mg/minute for adult maintenance 1

Pain Management (Off-Label)

• Sub-anesthetic doses: 0.5 mg/kg IV bolus followed by 1-2 μg/kg/min infusion reduces opioid requirements by approximately 22 mg morphine equivalents 2
• Pediatric adjunct: 0.5 mg/kg with optional continuous infusion of 0.1-0.2 mg/kg/hr (maximum 0.4 mg/kg/hr) 2
• ICU continuous infusion: 0.5-2 mg/kg/hr (maximum 100 mg/hour) 2
• Maximum intraoperative dose: 0.5 mg/kg/h, discontinue at procedure end 2

Hemodynamic Considerations

Ketamine produces dose-dependent increases in heart rate, blood pressure, and cardiac output through sympathetic nervous system stimulation, making it advantageous in shock states but potentially problematic in cardiovascular disease. 3

Advantages in Specific Populations

• Superior hemodynamic stability in trauma and septic shock compared to propofol or dexmedetomidine 3, 2, 4
• Maintains cerebral perfusion pressure in traumatic brain injury 3
• Does not increase intracranial pressure compared to opioids (mean difference 1.94 mmHg, 95% CI -2.35 to 6.23, P=0.38) 3

Hemodynamic Risks

• In septic patients, ketamine causes less hypotension than etomidate (51% vs 73%) according to one report, but other data show higher post-RSI hypotension rates (OR 2.7) 3
• Emergency department peri-intubation hypotension: 18.3% with ketamine vs 12.4% with etomidate 3
• In patients with depleted catecholamine reserves, ketamine can suppress myocardial contractility despite its sympathomimetic effects 3, 4

Contraindications and Precautions

Absolute Contraindications

• Pregnancy: All ketamine formulations are contraindicated in women who are or may become pregnant 3, 2
• Uncontrolled cardiovascular disease 3, 2

Relative Contraindications (Use with Caution)

• Ischemic heart disease, cerebrovascular disease, or hypertension due to cardiovascular stimulant effects 3
• Active psychosis (emergence reactions occur in 10-30% of adults) 3
• Severe liver dysfunction (extensive hepatic metabolism required) 3
• High ocular pressure 3

Special Considerations

• High intracranial pressure is NOT an absolute contraindication based on recent evidence 3
• Patients who have not followed nil per os guidelines should not receive ketamine due to aspiration risk 1

Side Effect Management

Psychotomimetic Effects

• Co-administer benzodiazepines (particularly midazolam) to minimize emergence reactions including dysphoria, nightmares, hallucinations, and delirium 3, 2, 1
• Psychotomimetic effects occur especially at higher doses and with prolonged use 2

Respiratory and Airway

• Administer antisialagogue prior to induction due to potential for increased salivation 1
• While laryngeal-pharyngeal reflexes provide some airway protection, vomiting and aspiration can still occur 1

Genitourinary

• In chronic ketamine users, consider cessation if genitourinary pain continues with other genitourinary symptoms 1

Other Side Effects

• Sedation is the predominant side effect 2
• Purposeless and tonic-clonic movements of extremities may occur and do not indicate need for additional dosing 1
• Monitor for nausea and vomiting, particularly in patients with gastritis 4

Clinical Advantages by Application

Pain Management

• Local infiltration consistently demonstrates superior analgesia compared to IV administration 2
• Subcutaneous administration provides similar analgesia to IV route 2
• Pre-operative administration provides better pain relief than postoperative dosing 2
• Effective for opioid-refractory cancer pain when other modalities fail 2
• Reduces postoperative respiratory impairment and agitation in recovery 2

Breastfeeding Compatibility

• No data available on transfer to human milk, but levels likely low due to rapid redistribution from plasma 5
• Other induction agents should be used if possible 5
• If used, monitor infant for drowsiness and poor feeding 5

Monitoring Requirements

• Continuous cardiac monitoring and pulse oximetry during infusion 2
• Regular assessment of sedation level, respiratory status, and hemodynamics 2, 1
• In shock patients, monitor carefully as altered drug metabolism may occur 4

Drug Interactions

• Avoid mixed agonist-antagonists (butorphanol, pentazocine) in combination with ketamine 2