Ketamine

# Ketamine ## Overview - **Classification**: Dissociative anesthetic, NMDA receptor antagonist. - **Mechanism**: Non-competitive antagonist of N-methyl-D-aspartate (NMDA) receptors; also interacts with opioid, monoaminergic, and muscarinic receptors. ## Primary Indications 1. **Anesthesia & Sedation**: Induction and maintenance of general anesthesia, procedural sedation. 2. **Analgesia**: Acute and chronic pain management, often opioid-sparing. 3. **Refractory Status Epilepticus**: As an add-on therapy for refractory cases. ## Adult Dosing ### Standard Dosing **Procedural Sedation / Anesthesia Induction** - **Dose**: **1-2 mg/kg IV** (initial); **6.5-10 mg/kg IM** (initial). - **Frequency**: Single dose; IV can be repeated with **0.5-1 mg/kg** for maintenance. - **Route**: Intravenous (IV), Intramuscular (IM). - **Special Considerations**: Administer IV dose over **60 seconds** to avoid respiratory depression. **Analgesia (Sub-dissociative)** - **Dose**: **0.1-0.3 mg/kg IV bolus** over 5-10 min; or **0.1-0.6 mg/kg/hour IV infusion**. - **Frequency**: Bolus PRN; Infusion continuous. - **Route**: Intravenous (IV). - **Max Dose**: Infusion typically limited by adverse effects, not a set max. **Refractory Status Epilepticus** - **Dose**: **0.5-2 mg/kg IV bolus** (initial); then **0.1-2 mg/kg/hour IV infusion**. - **Frequency**: Bolus PRN; Infusion continuous. - **Route**: Intravenous (IV). ### Dose Adjustments - **Renal Impairment**: No specific adjustment needed; monitor for prolonged effects. - **Hepatic Impairment**: Caution; consider **50% dose reduction** in severe impairment (Child-Pugh C). - **Elderly Patients**: Start with lower doses; increased sensitivity and risk of adverse effects. ## Pediatric Dosing ### Neonates (0-28 days) - **Dose**: **0.5-2 mg/kg IV** for sedation/anesthesia; **0.1-0.5 mg/kg/hour IV infusion** for pain. - **Frequency**: Single dose or continuous infusion. - **Maximum**: Single dose up to **4 mg/kg** (anesthesia). - **Special Notes**: Use with extreme caution; monitor for respiratory depression and prolonged emergence. ### Infants (1-12 months) - **Dose**: **1-2 mg/kg IV** for anesthesia; **5-10 mg/kg IM** for anesthesia; **0.1-1.5 mg/kg/hour IV infusion** for pain. - **Frequency**: Single dose or continuous infusion. - **Maximum**: Single dose up to **4 mg/kg** (anesthesia). ### Children (1-12 years) - **Dose**: **1-2 mg/kg IV** for anesthesia; **5-10 mg/kg IM** for anesthesia; **0.1-1.5 mg/kg/hour IV infusion** for pain. - **Frequency**: Single dose or continuous infusion. - **Maximum**: Single dose up to **4 mg/kg** (anesthesia); Infusion up to **2 mg/kg/hour**. ### Adolescents (13-18 years) - **Dose**: Generally follows adult dosing guidelines. - **Maximum**: Adult maximum doses apply. ## Safety Information ### Contraindications - **Absolute**: Conditions where significant blood pressure or heart rate elevation is hazardous (e.g., severe uncontrolled hypertension, aortic dissection, severe CHF, history of stroke/ICH, uncorrected hyperthyroidism, pheochromocytoma, acute globe injury). - **Relative**: Psychiatric conditions (schizophrenia, acute psychosis), porphyria. ### Common Adverse Effects - **Very Common (>10%)**: Emergence reactions (hallucinations, vivid dreams, delirium), increased blood pressure, increased heart rate, nystagmus, increased salivation, nausea/vomiting. - **Common (1-10%)**: Diplopia, generalized tonic-clonic movements, laryngospasm, respiratory depression (rapid IV push). - **Serious but Rare**: Anaphylaxis, hepatotoxicity (with chronic high-dose use), urinary tract dysfunction/cystitis (chronic high-dose recreational use). ### Key Drug Interactions - **CNS Depressants (e.g., benzodiazepines, opioids)**: Potentiate respiratory depression and sedation. Consider dose reduction of ketamine. - **Sympathomimetics (e.g., epinephrine, pseudoephedrine)**: Additive increase in blood pressure and heart rate. Avoid concurrent use. - **Thyroid Hormones**: Increased risk of hypertension and tachycardia. Use with caution. - **CYP3A4 Inducers/Inhibitors**: May alter ketamine levels. Monitor for efficacy or toxicity. ## Monitoring & Follow-up - **Before Treatment**: Baseline vitals (BP, HR, SpO2), airway assessment, cardiac/psychiatric history. - **During Treatment**: Continuous ECG, pulse oximetry, blood pressure, heart rate, respiratory rate. - **Clinical Signs**: Monitor for respiratory depression, laryngospasm, hypertension, tachycardia, agitation, or hallucinations. ## Clinical Pearls - 💡 **Emergence Reactions**: Can be mitigated by co-administration of a benzodiazepine (e.g., midazolam). - 💡 **Airway Management**: Ketamine increases salivary secretions; consider anticholinergic pre-medication (e.g., glycopyrrolate) to reduce sialorrhea. - 💡 **Administration Rate**: Always administer IV bolus doses slowly over **60 seconds** to minimize respiratory depression and apnea risk. - 💡 **Pain Control**: Highly effective for acute, severe pain, and can be valuable in neuropathic pain states. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.