What is the recommended intramuscular (IM) ketamine dose for Electroconvulsive Therapy (ECT)?

IM Ketamine Dosing for ECT

For electroconvulsive therapy (ECT), administer ketamine 9-13 mg/kg intramuscularly, which produces surgical anesthesia within 3-4 minutes with anesthetic effects lasting 12-25 minutes. 1

Recommended IM Dosing Protocol

• The FDA-approved IM dose range is 6.5-13 mg/kg, with 9-13 mg/kg producing optimal surgical anesthesia within 3-4 minutes 1
• The anesthetic effect typically lasts 12-25 minutes following IM injection 1
• An initial IM dose of 4 mg/kg with atropine 0.01 mg/kg produces surgical anesthesia within 3-4 minutes and results in faster onset compared to alternative sedatives 2

Comparison to IV Dosing for ECT

While the question specifically asks about IM dosing, it's important to note that IV ketamine for ECT is typically dosed at 1-2 mg/kg (median 1.1 mg/kg), which is substantially lower than IM dosing due to different bioavailability 3, 4. Studies examining ketamine as an ECT anesthetic have used IV doses up to 2 mg/kg 5. However, doses of 0.8 mg/kg or greater demonstrate improved reduction in depressive symptoms compared to lower doses 6.

Critical Adjunctive Medication

• Administer an antisialagogue (atropine 0.01 mg/kg, minimum 0.1 mg, maximum 0.5 mg) prior to induction to prevent excessive salivation 1, 2
• Consider adding a benzodiazepine if clinically indicated for prevention of neuropsychological manifestations during emergence from anesthesia 1

Essential Safety Monitoring

• Ketamine must be administered by or under the direction of physicians experienced in general anesthetics, airway maintenance, and ventilation 1
• Continuously monitor vital signs throughout the procedure 1
• Emergency airway equipment must be immediately available 1
• Be prepared to provide respiratory support, as rapid administration may result in respiratory depression and enhanced vasopressor response 1

Important Caveats

• Ketamine is not recommended for patients who have not followed nil per os (NPO) guidelines due to potential for vomiting and aspiration, despite some degree of airway protection from active laryngeal-pharyngeal reflexes 1
• Purposeless and tonic-clonic movements of extremities may occur during ketamine anesthesia; these movements do not imply inadequate anesthesia and are not indicative of the need for additional doses 1
• Cardiovascular adverse effects (hypertension, tachycardia) are particularly relevant in the ECT setting and may be mitigated with concurrent propofol, though this adds complexity 6

Maintenance Dosing if Needed

• If longer duration is required, repeat increments of one-half to the full induction dose as needed for maintenance of anesthesia 1
• Note that higher total doses will result in longer time to complete recovery 1