Updated July 2026 · 8 min read
Part of the ICU Pharmacology Hub — browse every related guide in one place.
Most nurses meet ketamine as an induction agent for a crashing airway. But at a fraction of that dose, run as a continuous infusion, it becomes one of the most useful analgesics in the ICU — controlling pain that opioids alone can't touch, and letting the team cut the opioid load in a patient who's becoming tolerant or over-sedated.
Opioids act on opioid receptors; ketamine works mostly by blocking the NMDA receptor, a completely different pain pathway. That matters for two reasons. First, NMDA activation is central to central sensitization and opioid-induced hyperalgesia — the phenomenon where a patient on escalating opioids paradoxically hurts more. By interrupting that pathway, ketamine can break the cycle and let opioid requirements fall. Second, because ketamine doesn't rely on opioid receptors, it provides analgesia without adding to respiratory depression, which is the ceiling that limits opioid dosing in a spontaneously breathing patient. This is the whole appeal of the analgesic-dose infusion: real pain control that spares the airway and the gut.
Exact rates are set by your facility protocol and weight-based, but the principle is constant: start low, titrate to the pain score, and coordinate with the primary opioid so the two are adjusted together rather than stacked blindly.
The opioid-sparing infusion shines in burns (severe, repeated dressing-change pain and high opioid tolerance), multi-trauma and rib fractures (where preserving respiratory drive protects the patient from splinting and pneumonia), sickle-cell vaso-occlusive crisis and other opioid-tolerant chronic-pain patients, and any ICU patient whose pain is uncontrolled despite escalating opioids or who is being pushed toward over-sedation to chase that pain. It's also used as an adjunct in procedural and post-operative settings.
Even at analgesic doses, ketamine has a recognizable side-effect signature. Its sympathomimetic effect tends to raise heart rate and blood pressure — usually helpful in a hypotensive trauma patient, but a caution in uncontrolled hypertension, active cardiac ischemia, or aortic pathology. It increases secretions, so watch for hypersalivation, especially with airway concerns. The best-known effect is emergence phenomena — vivid dreams, dissociation, or unpleasant hallucinations — which are far less common at analgesic doses but still occur; a calm environment helps, and benzodiazepines can treat significant reactions. Historically ketamine was avoided in head injury for fear of raised intracranial pressure, but current evidence has largely walked that back in the setting of controlled ventilation. Follow neuro and hemodynamic status, pain scores, and sedation level, and reassess the opioid dose as the ketamine takes hold.
| Point | What the nurse does |
|---|---|
| Know the dose class | Confirm it's the analgesic (sub-dissociative) drip, not the sedation drip |
| Expect opioid-sparing | Titrate to pain score and lower the opioid as ketamine works |
| Watch hemodynamics | Anticipate higher HR/BP — caution with ischemia and severe HTN |
| Manage secretions | Watch for hypersalivation, especially with airway risk |
| Handle emergence | Calm environment; treat significant reactions with a benzodiazepine |
| Document controlled drug | Waste and charting per policy — ketamine is a controlled substance |
Related: Etomidate vs ketamine for RSI · Ketamine for alcohol withdrawal · Precedex withdrawal · ICU sepsis protocol
Educational content for licensed clinicians. Always follow your facility's pharmacy dosing protocol and provider orders. Not medical advice.
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