What is the appropriate use and dosage of ketamine (anesthesia medication) in medical settings?

Ketamine: Uses, Dosing, and Administration in Medical Settings

Ketamine should be administered by or under the direction of physicians experienced in general anesthetics, airway management, and ventilation, with continuous monitoring of vital signs and immediate availability of emergency airway equipment. 1

Clinical Applications and Indications

• Ketamine is a dissociative anesthetic agent with sedative and analgesic properties that has been used clinically for over 50 years 2
• Primary FDA-approved indications include anesthesia induction/maintenance and procedural sedation 1, 3
• Ketamine has demonstrated efficacy for procedural sedation in children with 100% adequacy of sedation in multiple studies 4
• For perioperative pain management, ketamine is recommended in surgeries with high risk of acute pain or chronic postoperative pain, and in patients with vulnerability to pain, particularly those taking long-term opioids 5
• Emerging applications include treatment of treatment-resistant depression, with esketamine (S-ketamine) FDA-approved for this indication in 2019 3

Dosing Guidelines

For Anesthesia

• Intravenous induction: 1-4.5 mg/kg (average 2 mg/kg) administered slowly over 60 seconds to produce 5-10 minutes of surgical anesthesia 1
• Intramuscular induction: 6.5-13 mg/kg (typically 9-13 mg/kg) producing surgical anesthesia within 3-4 minutes, lasting 12-25 minutes 1
• Maintenance infusion: 0.1-0.5 mg/minute by slow microdrip infusion technique 1

For Procedural Sedation

• IV administration: 1.5-2 mg/kg is more effective than 1.0 mg/kg, with only 5.5% requiring additional doses compared to 54% with lower dosing 6
• IM administration: 4 mg/kg with repeat doses of 2-4 mg/kg allowed after 5-10 minutes if needed 6
• Pediatric procedural sedation: Ketamine/midazolam (1-2 mg/kg and 0.05 mg/kg respectively) has shown superior efficacy compared to other sedation regimens 4

For Pain Management

• Perioperative pain: Maximum dose 0.5 mg/kg/h after anesthesia induction, with continuous infusion at 0.125-0.25 mg/kg/h, stopping 30 minutes before end of surgery 5
• Acute pain management: Subanesthetic doses include boluses <0.35 mg/kg, infusions at 0.5-1 mg/kg/h 5
• Critically ill adults: Low-dose ketamine (0.5 mg/kg IVP followed by 1-2 μg/kg/min infusion) as adjunct to opioid therapy 6

Administration Considerations

• The 100 mg/mL concentration must be diluted before IV administration with equal volume of either Sterile Water for injection, 0.9% Sodium Chloride Injection, or 5% Dextrose in Water 1
• For maintenance infusion, dilute to 1 mg/mL by transferring 10 mL from a 50 mg/mL vial (or 5 mL from 100 mg/mL vial) to 500 mL of 5% Dextrose or 0.9% Sodium Chloride 1
• IV ketamine has rapid onset (30-96 seconds) with average recovery time of approximately 84 minutes 6
• Consider administering an antisialagogue prior to ketamine administration due to potential for increased salivation 1

Monitoring and Safety

• Continuous monitoring of vital signs, oxygen saturation, heart rate, and blood pressure is required during ketamine administration 6
• Patients should maintain oxygen saturation >93% on room air during the procedure 6
• Ketamine provides some degree of airway protection through active laryngeal-pharyngeal reflexes, but vomiting and aspiration can still occur 1
• If patients develop hypoxemia or significant hypoventilation, they should be encouraged to breathe deeply, administered supplemental oxygen, and provided positive pressure ventilation if needed 5

Adverse Effects and Contraindications

• Common side effects include mild recovery agitation (17.6% of patients), moderate-to-severe agitation (1.6%), and emesis without aspiration (6.7%) 6
• Ketamine causes dose-dependent increases in heart rate, blood pressure, and cardiac output through sympathetic nervous system stimulation 6
• Contraindications include uncontrolled cardiovascular disease, pregnancy, active psychosis, severe liver dysfunction, or high intracranial/ocular pressure 5
• In pediatric patients, recovery agitation is associated with higher ASA status (>I) and decreasing age, while emesis is associated with increasing age 6
• Chronic ketamine use has been associated with genitourinary pain, cystitis, and cholangiopathy 7

Special Considerations

• Consider co-administration of benzodiazepines for prevention of neuropsychological manifestations during emergence from anesthesia 1
• For pediatric procedural sedation, ketamine/midazolam combination has shown fewer complications compared to midazolam/meperidine regimens 5
• Purposeless and tonic-clonic movements of extremities may occur during ketamine anesthesia but do not imply a light plane or need for additional doses 1
• Ketamine has abuse potential and has become popular in recreational settings, particularly in dance culture and electronic music events 7