Ketamine

Indications

Ketamine is used for: Induction of anesthesia.

Adult Dose

Intravenous Induction of anaesthesia Adult: 1-4.5 mg/kg via slow IV inj over 60 sec. A dose of 2 mg/kg produces surgical anaesthesia w/in 30 sec after inj lasting for 5-10 min. Increments of half to the full induction dose may be repeated as needed for maintenance of anesth. Alternatively, a total induction dose of 0.5-2 mg/kg via infusion, given at an appropriate rate, and maintained at a rate of 10-45 mcg/kg/min, adjusted according to response. Intramuscular Induction of anaesthesia Adult: 6.5-13 mg/kg. A dose of 10 mg/kg produces surgical anaesthesia w/in 3-4 min after inj lasting for 12-25 min. Increments of half to the full induction dose may be repeated as needed for maintenance of anesth. For diagnostic or other procedures not involving intense pain: 4 mg/kg as initial dose.

Child Dose

Renal Dose

Administration

Reconstitution: 50 mg/mL and 100 mg/mL vials may be further diluted in 5% dextrose or 0.9% NaCl to prepare a maintenance infusion containing 1 mg/mL (or 2 mg/mL in patients w/ fluid restrictions).

Contra Indications

Hypertension, history of cerebrovascular accident. Eye injury, raised ocular and intracranial pressure. Psychotic disorders.

Precautions

Minimise verbal and tactile stimulation during recovery period. Chronic alcoholic and alcohol-intoxicated patients. Preanaesthetic elevated CSF pressure. Dependence and tolerance may develop. May impair ability to drive or operate machinery. Monitor cardiac function in patients with hypertension or cardiac decompensation. Pregnancy and lactation.

Pregnancy-Lactation

Pregnancy There are no adequate and well-controlled studies performed in pregnant women; in animal reproduction studies in rats developmental delays (hypoplasia of skeletal tissues) were noted at 0.3 times the human intramuscular dose of 10 mg/kg; in rabbits, developmental delays and increased fetal resorptions were noted at 0.6 times the human dose; since safe use in pregnancy, including obstetrics (either vaginal or abdominal delivery), has not been established, such use is not recommended Lactation Not known if excreted in breast milk; effect on nursing infant unknown

Interactions

Prolonged recovery time w/ barbiturates or narcotics. May potentiate neuromuscular blocking effects of atracurium and tubocurarine including resp depression w/ apnoea. May increase risk of bradycardia, hypotension or decreased cardiac output w/ halogenated anaesth. May potentiate CNS depression and risk of resp depression w/ CNS depressants (e.g. phenothiazines, sedating H1-blockers, skeletal muscle relaxants). May antagonise hypnotic effect of thiopental. May increase risk of HTN w/ thyroid hormones. May increase risk of hypotension w/ antihypertensive agents. Reduction in seizure threshold resulting in unpredictable extensor-type seizures when given concurrently w/ theophylline.

Adverse Effects

Side effects of Ketamine : >10% Emergence rxns (Emergence reactions e.g. vivid dreams, hallucinations, confusion, irrational behaviour) HTN, Increased cardiac output, Increased ICP, Tachycardia, Tonic-clonic movements, Visual hallucinations, Vivid dreams 1-10% Bradycardia, Diplopia, Hypotension, Increased IOP, Injection-site pain, Nystagmus <1% Anaphylaxis, Cardiac arrhythmia, Depressed cough reflex, Fasciculations, Hypersalivation, Increased IOP, Increased metabolic rate, Hypertonia, Laryngospasm, Respiratory depression or apnea with large doses or rapid infusions

Mechanism of Action

Ketamine is a noncompetitive N-methyl-D-aspartate receptor antagonist that blocks glutamate. It has a direct action on the cortex and limbic system. It produces a cataleptic-like state wherein the patient is withdrawn from the surrounding environment.