Indications:
An anesthetic/analgesic agent useful in variety of surgical procedure particularly in pediatric patients. Mechanism of action
Ketamine has several clinically useful properties, including analgesia and less cardiorespiratory depressant effects than other anaesthetic agents, it also causes some stimulation of the cardiocascular system. Ketamine has been reported to produce general as well as local anaesthesia. It interacts with N-methyl-D-aspartate (NMDA) receptors, opioid receptors, monoaminergic receptors, muscarinic receptors and voltage sensitive Ca ion channels. Unlike other general anaesthetic agents, ketamine does not interact with GABA receptors.
Pharmacodynamics - Ketamine is a rapid acting general anesthetic that also has significant analgesic activity and a lack of cardiopulmonary depressant effects. It is thought to induce both anesthesia and amnesia by functionally disrupting the CNS through over stimulating the CNS or inducing a cataleptic state. Ketamine inhibits GABA, and also may block serotonin, norepinephrine, and dopamine in the CNS. The thalamoneocortical system is depressed while the limbic system is activated. It induces anesthetic stages I & II, but not stage III. In cats, it causes a slight hypothermic effect as body temperatures decrease on average by 1.6°C after therapeutic doses.
Effects on muscle tone are described as being variable, but ketamine generally either causes no changes in muscle tone or increased tone. Ketamine does not abrogate the pinnal and pedal reflexes, nor the photic, corneal, laryngeal or pharyngeal reflexes.
Ketamine’s effects on the cardiovascular system include increased cardiac output, heart rate, mean aortic pressure, pulmonary artery pressure, and central venous pressure. Its effects on total peripheral resistance are described as being variable. Cardiovascular effects are secondary to increased sympathetic tone; ketamine has negative inotropic effects if the sympathetic system is blocked,
Ketamine does not cause significant respiratory depression at usual doses, but at higher doses it can cause respiratory rates to decrease. In humans with asthma, ketamine causes decreased airway resistance.
Doses & Administrations:
Parenteral: Adult: For Inductions : 1-4.5mg/kg I/V or 5-10mg/kg I/M. Maintenance : 0.1 to 0.5mg/minute by intravenous infusion or one half to full induction dose I/V or I/M repeated as required. Sedation and analgesia : 2-4 mg/kg by I/M or 0.2-0.75mg I/V. Pediatric : As for adult.
Contra Indications:
Hypersensitivity to ketamine, hypertension.
Precautions:
Cardiovascular disease, psychiatric illness, hyperthyroidism, acute-intermittent porphyria.
Pregnancy Status:
No adequate human data available.
Renal Failure Doses:
Dose adjustment do not appear warranted in renal insufficiency . Lactation Status:
UnKnown.
Interactions:
Barbiturates and narcotics may prolong the recovery time when use concomitantly with ketamine.
Adverse Effects:
Change in B.P and pulse rate, brady cardia, arrythmia, nausea, vomiting, diplopia, nystagmus, respiratory depression (rapid I.V), hallucinations and transient psychotic sequence.
Sources
http://www.rxlist.com/cgi/generic3/ketamine.htm
Drugs.com http://www.drugs.com/cdi/ketamine.html
http://elephantcare.org/Drugs/ketamine.htm
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Unknown - Sunday, 14 August 2011
