Ketamine Infusion Rate for Maintaining Sedation
For maintaining sedation with intravenous ketamine, administer a continuous infusion at 0.1 to 0.5 mg/kg/hour (or 1.7 to 8.3 mcg/kg/min), which will maintain general anesthesia in adult patients following ketamine induction. 1
Initial Bolus Dosing
Before starting a maintenance infusion, administer an appropriate induction dose:
Give 1.5-2 mg/kg IV as the initial bolus over 60 seconds, which produces 5-10 minutes of surgical anesthesia within 30 seconds and requires significantly fewer supplemental doses compared to lower dosing (only 5.5% of patients require additional ketamine versus 54% with 1.0 mg/kg). 2, 1
Rapid administration should be avoided as it may result in respiratory depression and enhanced vasopressor response. 1
Maintenance Infusion Protocols
Standard Maintenance Approach
Administer ketamine by slow microdrip infusion at 0.1 to 0.5 mg/minute (equivalent to approximately 0.1-0.5 mg/kg/hour in a 70kg adult) to maintain general anesthesia. 1
For preparation, dilute ketamine to create a 1 mg/mL solution by transferring 10 mL from a 50 mg/mL vial or 5 mL from a 100 mg/mL vial to 500 mL of 5% Dextrose or Normal Saline, and use immediately after dilution. 1
Alternative Dosing Regimens
For critically ill patients requiring prolonged sedation, start with 1 mg/kg IV bolus followed by continuous infusion at 1.0 mg/kg/hour, then titrate in increments of 0.5 mg/kg/hour every 30 minutes until achieving adequate sedation (Ramsay score of 4). 3
The mean maintenance dose in ICU patients is approximately 2.25 mg/kg/hour, with plasma concentrations around 3 mcg/mL and recovery time averaging 168 minutes after cessation. 3
Combination Therapy Considerations
Consider adding midazolam 0.05-0.1 mg/kg IV to reduce emergence reactions and recovery agitation, particularly in patients over 10 years old (reduces agitation from 35.7% to 5.7%). 2
When combining ketamine with midazolam for ICU sedation, use ketamine 1 mg/kg bolus followed by 1.0 mg/kg/hour infusion with midazolam 0.1 mg/kg bolus and 0.05 mg/kg/hour infusion. 3
Concurrent administration of ketamine with intravenous lidocaine is acceptable and has often been used in patients with difficult-to-manage pain. 4
Monitoring Requirements
Continuously monitor vital signs including ECG, pulse oximetry, and blood pressure throughout ketamine administration, as care consistent with general anesthesia is required. 5
Maintain vascular access throughout the procedure until the patient is no longer at risk for cardiorespiratory depression. 5
Emergency airway equipment must be immediately available, and practitioners must be able to rescue patients from unintended deep sedation. 5
Duration and Recovery Expectations
Average total sedation time with IV ketamine is approximately 75-78 minutes, with recovery time averaging 84 minutes (range 22-215 minutes). 2
Plasma half-life of ketamine is approximately 1 hour, with rapid decrease in plasma concentrations after cessation of infusion. 3
Common Pitfalls and Safety Considerations
Do NOT continue ketamine infusion into the postoperative period, as this increases risk of hallucinations without significantly enhancing analgesic effect. 5
Hypoxemia occurs in 1.6-7.3% of patients and is typically transient and responsive to supplemental oxygen, though bag-valve-mask ventilation may be required in approximately 2% of cases. 2
Recovery agitation occurs in approximately 17.6% of patients (mild) and 1.6% (moderate-to-severe), which may require treatment with benzodiazepines. 2
Administer an antisialagogue prior to induction due to potential for increased salivation during ketamine administration. 1
Contraindications
Avoid ketamine in patients with uncontrolled cardiovascular disease, cerebrovascular disease, active psychosis, severe hepatic dysfunction, elevated intracranial or intraocular pressure, or pregnancy. 2, 5
Ketamine causes dose-dependent increases in heart rate, blood pressure, and cardiac output through sympathetic nervous system stimulation. 2