Ketamine is neither a traditional local anesthetic nor a conventional general anesthetic. It belongs to its own category called a dissociative anesthetic, meaning it disconnects the brain from sensory input rather than simply numbing a body part or rendering you fully unconscious in the way other general anesthetics do. At higher doses it can produce profound unconsciousness similar to general anesthesia, while at lower doses it creates a trance-like state with strong pain relief, placing it in a unique middle ground.
What “Dissociative” Actually Means
Most anesthetics work in one of two straightforward ways: local anesthetics block nerve signals in a specific body region, and general anesthetics suppress brain activity broadly enough to produce complete unconsciousness. Ketamine does something different. It blocks a specific type of receptor in the brain involved in transmitting pain and sensory signals. When those receptors are blocked, the brain essentially loses its connection to incoming sensations. You may still have your eyes open and appear semi-aware, but you feel detached from pain, your surroundings, and even your own body.
This dissociative state is what makes ketamine hard to classify neatly. At low doses (used for pain relief or sedation), it produces numbness and a dreamlike detachment while you continue breathing on your own. At high doses, it causes full unconsciousness with no awareness or memory of the procedure, functioning much like general anesthesia. The difference between sedation and full anesthesia with ketamine is largely a matter of how much is given.
How It Differs From General Anesthesia
The most important distinction between ketamine and conventional general anesthetics is what happens to your breathing and protective reflexes. Standard general anesthetics suppress respiratory drive, which is why patients on them typically need a breathing tube and mechanical ventilation. Ketamine preserves spontaneous breathing. It also maintains the reflexes that keep your airway clear, like coughing and swallowing, and does not compromise airway patency. This makes it far easier to administer safely in settings where full airway management isn’t available.
Ketamine also diverges from other general anesthetics in how it affects circulation. Most anesthetics lower blood pressure and can slow the heart, sometimes dangerously in patients who are already hemodynamically unstable. Ketamine does the opposite: it mildly stimulates the cardiovascular system. A meta-analysis of hemodynamic data found that ketamine raises systolic blood pressure by an average of about 13 mmHg and heart rate by roughly 4 beats per minute. These increases are modest and resolve shortly after the drug wears off, but they make ketamine especially valuable in trauma patients or anyone at risk of dangerously low blood pressure.
How It Differs From Local Anesthesia
Ketamine is not a local anesthetic. It does not numb a specific patch of tissue or block a particular nerve the way lidocaine or bupivacaine would. Its pain-relieving effects come from the brain, not from the injection site. You could inject ketamine into a muscle in your arm and lose sensation throughout your entire body because the drug travels to the brain and alters how it processes all incoming signals.
That said, ketamine is sometimes added to true local or regional anesthetics to extend their pain-relieving effects. A systematic review of randomized controlled trials found that when ketamine was mixed into a regional nerve block, the duration of pain relief increased by roughly 3 hours on average. For peripheral nerve blocks specifically, the extension was even more dramatic, around 6 hours. It also prolonged sensory blockade by about 29 minutes without significantly affecting motor function, meaning patients kept their ability to move while gaining longer-lasting numbness. This adjuvant role is the closest ketamine comes to local anesthesia, but it’s acting as a booster for the local anesthetic rather than numbing tissue on its own.
Where Ketamine Is Used in Practice
Ketamine’s unique profile makes it the anesthetic of choice in several specific situations. In emergency departments, it is widely used for procedural sedation in children who need painful but brief interventions: stitching facial lacerations, setting broken bones, draining abscesses, or removing foreign bodies from the eye, ear, or nose. Children tolerate ketamine well, and the fact that they keep breathing independently makes it safer than alternatives that require intubation and a full anesthesia team.
In battlefield and disaster medicine, ketamine’s advantages are even more pronounced. It can be given as an intramuscular injection (no IV line needed), it supports rather than crashes blood pressure, and it doesn’t require ventilator equipment. These properties make it one of the few anesthetics that a single provider can administer safely in an austere environment. It’s also used in veterinary medicine for the same practical reasons.
In hospital operating rooms, ketamine is more commonly used as a supplement to other anesthetics rather than the sole agent. An anesthesiologist might add a sub-anesthetic dose to reduce the total amount of opioid painkillers needed during surgery, or use it as the primary induction agent in a patient whose blood pressure is dangerously low from blood loss or sepsis.
Side Effects Unique to Ketamine
The dissociative mechanism that makes ketamine effective also creates its most notable side effect: emergence phenomena. As the drug wears off, some patients experience vivid dreams, hallucinations, confusion, or agitation during the transition back to normal awareness. In one study of 115 patients after laparoscopic surgery, about 15% experienced emergence delirium, though the rate was not significantly different between patients who received ketamine and those who did not (18% vs. 11%).
These experiences tend to be brief, lasting minutes to a short period after waking. They’re more common in adults than children, and clinicians often give a mild sedative alongside ketamine to reduce the likelihood. Patients sometimes describe the feeling as floating, being in a tunnel, or having strange visual distortions. While unsettling, these effects are temporary and leave no lasting impact.
Nausea and increased saliva production are the other common side effects. The blood pressure and heart rate increases are generally well tolerated in healthy patients but make ketamine a poor choice for anyone with uncontrolled high blood pressure, a history of stroke, or certain heart conditions where extra cardiovascular stimulation would be harmful.