IntramuscularInduction of anaesthesiaAdult: 6.5-13 mg/kg. A dose of 10 mg/kg produces surgical anaesth 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.
IntravenousInduction of anaesthesiaAdult: 4.5 mg/kg via slow IV inj over 60 sec. A dose of 2 mg/kg produces surgical anaesth 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 anesthesia. Alternatively, a total induction dose of 0.5-2 mg/kg via infusion, given at an appropriate rat, and maintained at 10-45 mcg/kg/min, adjusted according to response.
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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).
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Barbiturates and diazepam.
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Patient w/ HTN, eclampsia or pre-eclampsia, severe coronary or myocardial disease, cerebrovascular accident or cerebral trauma.
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Patient w/ cardiac decompensation, chronic alcoholic or acutely alcohol-intoxicated patients, pre-anaesth elevated CSF pressure, globe injuries, increased intraocular pressure (e.g. glaucoma), neurotic traits or psychiatric illness (e.g. schizophrenia, acute psychosis), acute intermittent porphyria, seizures, hyperthyroidism, pulmonary or upper resp infection, intracranial mass lesions, head injury, or hydrocephalus, hypovolaemia, dehydration, cardiac disease esp coronary artery disease (e.g. CHF, myocardial ischaemia, MI). Pregnancy and lactation.
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Emergence reactions (e.g. vivid dreams, hallucinations, confusion, irrational behaviour); increased muscle tone sometimes resembling seizures; temporary HTN and tachycardia, hypotension, bradycardia, arrhythmias, apnoea, laryngospasm, resp depression, diplopia, nystagmus, nausea, vomiting, lacrimation, hypersalivation, raised intraocular and CSF pressure, transient rash and pain at inj site, cystitis.
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Avoid driving, operating hazardous machinery or engaging in hazardous activities w/in 24 hr or more after anaesth.
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Monitor heart rate, BP, resp rate, transcutaneous oxygen saturation, emergence reactions. Cardiac function should be continuously monitored in patients w/ increased BP or cardiac decompensation.
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Symptoms: Resp depression. Management: Employ supportive ventilation. Mechanical support of respiration is preferred to admin of analeptics.
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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 anaesthetics. 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.
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May potentiate CNS depression when used concurrently w/ alcohol.
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Description:
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.
Onset: 30 sec (IV); 3-4 min (IM).
Duration: 5-10 min (IV); 12-25 min (IM).
Pharmacokinetics:
Absorption: Rapidly absorbed following parenteral admin.
Distribution: Crosses the placenta. Volume of distribution: 3 L/kg.
Metabolism: Hepatic biotransformation to norketamine (active metabolite). Other metabolic pathways include hydroxylation of the cyclohexone ring and conjugation w/ glucuronic acid.
Excretion: Via urine as metabolites. Elimination half-life: 10-15 min (alpha phase); 2.5 hr (beta phase).
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Anon. Ketamine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. https://online.lexi.com. Accessed 23/07/2014. Buckingham R (ed). Ketamine HCl. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. https://www.medicinescomplete.com. Accessed 23/07/2014. Ketalar Injection. U.S. FDA. https://www.fda.gov/. Accessed 23/07/2014. Ketamine HCl Injection, Solution (Mylan Institutional LLC). DailyMed. Source: U.S. National Library of Medicine. https://dailymed.nlm.nih.gov/dailymed/. Accessed 23/07/2014.
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