Ketamine for Surgical Pain: What Patients Need to Know
A patient-friendly guide to subanesthetic ketamine used for surgical pain management, including how it works, what the experience feels like, side effects, benefits for opioid reduction, and recovery expectations.
What Ketamine Is and How It Helps Pain
Ketamine is an anesthetic medication used at high doses in operating rooms since the 1970s. At much lower (subanesthetic) doses, it also effectively reduces surgical pain through a completely different mechanism than opioids.
Opioids work on opioid receptors in the brain and spinal cord. Ketamine works primarily by blocking NMDA receptors (N-methyl-D-aspartate receptors), which are involved in pain amplification. This dual mechanism makes the combination of low-dose ketamine with opioids significantly more effective than either drug alone.
One of ketamine's key benefits is that it reduces central sensitization: the process by which the nervous system becomes hypersensitive to pain signals after injury or surgery. This can reduce chronic post-surgical pain development.
Studies show that perioperative ketamine (given before, during, or after surgery) reduces 24-hour opioid consumption by 25% to 40% on average. Lower opioid use means fewer opioid side effects, including nausea, constipation, and respiratory depression.
Ketamine is most commonly used via intravenous infusion in a hospital or clinic setting. Ketamine lozenges (troches) or nasal sprays are used in some outpatient pain management programs.
What to Expect During and After Infusion
Subanesthetic ketamine infusions for pain are typically given at doses of 0.1 to 0.5 mg per kilogram per hour, far below the 1 to 2 mg per kilogram used for anesthesia induction. At these low doses, you remain awake and oriented.
Common sensations during infusion include mild dissociation (feeling slightly detached or dreamlike), dizziness, and unusual visual or auditory perceptions. These effects are dose-dependent and resolve completely within minutes of stopping the infusion.
Infusion duration varies. Peri-operative doses given during or immediately after surgery typically last 1 to 24 hours. Outpatient ketamine infusion series for chronic pain typically involve 40 to 60 minute sessions repeated 3 to 6 times over 2 to 3 weeks.
You cannot drive after a ketamine infusion. Arrange transportation. The dissociative effects resolve within 30 to 60 minutes, but judgment and reaction time may remain subtly affected for several hours.
Blood pressure and heart rate typically rise modestly during ketamine infusion. Your blood pressure and pulse will be monitored throughout. This cardiovascular stimulation is usually not a problem for healthy adults but requires caution in patients with uncontrolled hypertension.
Side Effects and Who Should Avoid It
The most common side effects at subanesthetic doses are nausea (in 10% to 20% of patients), dizziness, and mild dissociative experiences such as visual distortions or a dreamlike state. Pre-medicating with ondansetron reduces nausea risk.
Dysphoria (an unpleasant emotional state) or anxiety can occur during infusion, particularly at higher doses. Benzodiazepines such as midazolam are sometimes given alongside ketamine to reduce this effect.
Laryngospasm (brief spasm of the vocal cords) is rare at low doses but is one reason ketamine infusions require trained medical staff and resuscitation equipment nearby.
Ketamine is generally avoided or used with extreme caution in patients with uncontrolled high blood pressure, a history of psychosis (including schizophrenia), active substance use disorder involving ketamine or other dissociatives, and severe liver disease.
Repeated high-dose recreational ketamine use can cause ketamine cystitis, a severe bladder condition. This risk is not associated with medically supervised low-dose therapeutic use.
Ketamine and Opioid Reduction After Surgery
Ketamine is particularly valuable for patients with opioid tolerance (those who take opioids regularly for chronic pain), where standard post-surgical opioid doses are less effective. It can restore opioid sensitivity and improve pain control.
For opioid-naive patients (those not previously taking opioids), perioperative ketamine reduces post-operative opioid requirements and lowers the chance of transitioning to chronic opioid use after surgery.
In enhanced recovery after surgery (ERAS) protocols, ketamine is often part of a multimodal analgesia approach combining acetaminophen, NSAIDs, regional nerve blocks, and ketamine to minimize or eliminate opioid use entirely.
Pain relief from perioperative ketamine can outlast the infusion by days to weeks. This is thought to result from NMDA receptor modulation that reduces pain sensitization rather than simple analgesic effects.
If your surgeon or anesthesiologist recommends ketamine as part of your pain management plan, discuss your mental health history, current medications, and any previous experiences with ketamine or anesthesia to ensure the approach is appropriate for you.
Frequently asked
Questions patients ask.
Will I hallucinate during a ketamine infusion?
At the low doses used for surgical pain management, true hallucinations are uncommon. Most patients experience mild dissociation, described as feeling floaty, dreamy, or slightly detached from surroundings. These effects resolve completely when the infusion ends. Higher doses used in psychiatric treatment (for depression) carry a higher chance of perceptual effects. Tell your care team immediately if you feel anxious or overwhelmed during the infusion so the rate can be adjusted.
Is ketamine addictive?
Medically supervised, low-dose ketamine has a low addiction risk when used short-term for surgical recovery. Recreational ketamine use at high doses carries real addiction potential. If you have a personal or family history of substance use disorder, discuss this with your provider before receiving ketamine. Medical protocols include clear duration limits and monitoring to minimize misuse risk.
How is ketamine different from what I have heard about for depression treatment?
Ketamine for depression (often given as intravenous racemic ketamine or intranasal esketamine, brand name Spravato) targets different brain pathways at doses that produce stronger dissociative effects. Ketamine for surgical pain uses similar or lower doses but focuses on NMDA-receptor pain modulation rather than antidepressant effects. Some patients do report improved mood after ketamine infusions, which may be a secondary benefit of the NMDA pathway effects.
Can I request ketamine if I want to avoid opioids after surgery?
Yes, you can discuss this with your anesthesiologist and surgeon during your pre-operative appointments. Ketamine is not appropriate for everyone, and its use depends on your procedure, medical history, and the protocols available at your surgical facility. If opioid minimization is a priority for you, ask specifically about multimodal analgesia options including ketamine, nerve blocks, and non-opioid analgesics as a combined approach.
For patients
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This guide provides general information. For instructions tailored to your specific procedure, ask your provider about QR Rx care plans.
These medication guides are for educational purposes only and do not replace medical advice. Always follow your healthcare provider's specific medication instructions.
