Which IV anesthetic causes increased cerebral blood flow and cerebral metabolic rate? (E. REPEAT 2006)
Correct Answer: Ketamine
Description: Ref: Ajar Yadov, Short Textbook of Anaesthesia, 1st edition. Page 76 and Miller Textbook of Anaesthesia, 6th editionExplanation:KETAMINECauses Dissociative anaesthesia.Phencyclidine derivative.NMD A receptor agonist.Dose-2 mg/kg.Anesthetic Propertieso Onset of Action: 30-60 secondso Early regain of consciousness after 15-20 min due to Redistributiono Elimination half life: 2-3 hourso Strong analgesic propertyo Metabolised in liver and products excreted in urine.o Not a muscle relaxant.Primary site of action - Thalamo-neo-cortical projections.Cardiovascular SystemIncreases arterial BP.Increases heart rate.Increases cardiac output.IV agent of choice in SHOCK.Respiratory SystemPotent bronchodilator.Good induction agent for asthmatics.Upper airway reflexes remain largely intact.Increases salivatory and tracheo bronchial secretions.Using glycopyrollate or atropine becomes necessary.Central Nervous SystemIncreases intracranial pressure and can precipitate seizures.Increases cerebral blood flow and cerebral metabolic rate.Emergence reactions:o These are seen at emergenceo Vivid dreamingo Illusions.o Extracorporeal experiences like floatingo Excitemento Confusiono Euphoriao Fear.Hallucinations:o Auditory and visual hallucinations (Most common side effect of ketamine)o Treated with benzodiazepine.Other SystemsEyeo Increase intraocular tensiono Pupils dilate moderatelyo Nystagmus.GITo Increases intragastric pressureo Salivary secretions increased.Muscluaro Increases muscle toneo Increased non-puposeful movements.DoseCan be given IV, IM. oral, rectal and intrathecal route.IV - 2 mg/kg.IM- 5-10 mg/kg.AdvantagesInduction agent of choice in:o Asthmaticso Shock.o Children (Now Sevoflurance is DOC).o Constrictive pericarditiso Cardiac tamponade.Can be used as SOLE agent.Can be used safely at remote places and in inexperienced hands since does not depress heart or respiration.Preferred agent when patient is in FUELSTOMACH (Preserves laryngo-pharyngeal reflexes).Contraindicated in:Head injury.ICSOL.Eye injury.Ophthal pathology.Ischemic heart disease.Vascular aneurysm.Psychiatric diseases.Drug addicts.Hypertensives.
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Anaesthesia
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