Ketamine Side Effects
Ketamine Infusion Has a Broad Spectrum of Side Effects
Ketamine side effects are numerous, many of which are rare. Common side effects of ketamine infusion include dissociation, hallucinations, hypertension, nightmares, and sinus tachycardia. Ketamine appears to selectively interrupt association pathways of the brain before producing somatesthetic sensory blockade. Unlike barbiturates that act on the reticular activating system in the brainstem, ketamine acts on receptors in the cortex and limbic system.
Ketamine causes sedation and altered awareness
Cognitive side effects of ketamine may include amnesia (temporary loss of short-term memory), sedation, hallucinations, and a strong feeling of dissociation from the environment. It can induce a state of unconsciousness or trancelike state (eyes may remain open until deep anesthesia is obtained) that is cataleptic in nature characterized by minimal movement.
Ketamine has antidepressant and analgesic activity
Ketamine can relieve feelings of depression that may last anywhere from the duration of the infusion to a few weeks to months thereafter. Ketamine can also relieve pain at high enough doses administered over a long enough period of time.
Ketamine has sympathomimetic activity
Ketamine side effects also include stimulation of the sympathetic nervous system, causing tachycardia, hypertension, increased myocardial and cerebral oxygen consumption, increased cerebral blood flow, and increased intracranial and intraocular pressure.
Ketamine dilates the bronchi
Ketamine is a potent bronchodilator and can be used to treat refractory bronchospasm.
Ketamine has minimal respiratory system activity
Ketamine causes minimal respiratory depression. Ketamine has no effects on pharyngeal or laryngeal reflexes, thus, the patient’s airway remains intact.
Ketamine may cause post-anesthesia emergence reactions
After ketamine infusion, some patients experience some form of post-anesthesia emergence reaction. This type of reaction involves psychological alterations such as pleasant dreams, vivid imagery, hallucinations, nightmares, floating sensations, agitation, and dissociative states. Along with the emergence reactions, some patients may experience confusion, excitability, or irritability. Reportedly, these reactions occur less frequently in patients over 65 years of age and typically last only a few hours, although some patients may experience reoccurrence up to 24 hours postoperatively.
Ketamine has neuromuscular side effects
Ketamine can cause involuntary movements of the head and extremities, sometimes described as tonic-clonic movements. This side effect can be frequent with ketamine use. The movements are typically brief and sometimes include intense myoclonus with twitching, but are not considered seizure activity. These movements are typically benign and not associated with EEG changes. Skeletal muscle hypertonia and rigidity may also occur with ketamine use.
Ketamine may cause vision and ocular effects
Diplopia and nystagmus have been noted after ketamine administration.
Ketamine Infusion Side Effects by Percentage
dissociative state 12% Moderate
hallucinations 12% Moderate
hypertension > 10% Moderate
nightmares 12% Mild
sinus tachycardia > 10% Moderate
injection site reaction Mild
cardiac arrest Severe
increased intracranial pressure
increased urinary frequency