Induction agents Flashcards

Question

tell me about ketamine

Answer 1

ketamine is a phencyclidine derivative commonly used for anaesthesia induction, sedation, analgesia, refractory bronchospasm and recreational use. comes as clearcolourless solution in different strengths for IV, IM, intrathecal, epidural use. also available as oral tablet. IV dose is 1-2mg/kg IM 5-10mg/kg for pain 10-30mg given (0.1-0.5mg/kg) ketamine can come as a racemic mix or as an S.enantiomer. It works via non-competitive antagonisms of NMDA to reduce neuronal excitability and pain transmission. also potentiates u receptors and has a role in dopamine and serotonin reuptake inhibition. pharmacodynamics * dissociative amnesia and analgesia * slightly slower in onset than other agents = 60s (IM would be 15mins) * other CNS effects include - increase BF, ICP and O2 consumption. increases sympathetic NS. causes nystagmus and delirium and hallucination. emergence phenomena * CVS - tachycardia, hypertension (sympathetic response), increase CO. infact has myocardial depressive effects which are masked by sympathetic response. * respiratory - no loss of airway reflexes, no resp depression, potent bronchodilator, can drive secretions. * GI - N&V , increases uterine tone pharmacokinetics: - weak base with pKA of 7.5 - A: IV, IM , oral (BO 20%) - D: large VD (3L/kg) , 30% PB - M: renal - norketamine is active + glucuronides - E: renal , clearance 17ml/kg/hr. t1/2 2-3 hours

Answer 2

brain injury / raised ICP - although its advantage in CVS instability overides this. eye surgery / glaucoma - due to raised pressures and nystagmus avoid in porphyria avoid in psychosis avoid in severe IHD

Answer 3

imadazole derivative with ester link used to be used for induction anaesthesia for its good CVS profile however not used as much now due to supression of 11b hydroxylase and addisonian risk. presented as either lipid emulsion or propylene glycol (aqueous solution) IV dose of 0.3mg/kg works via potentiation of GABA Pharmacodynamics rapid onset anaesthesia 30seconds CNS - reduces CBF, ICP, increases EEG activity in epileptic foci and hence used in ECT. CVS - cardiostable resp - minimal effects however - inhibits 11b hydroxylase and 17a hydroxylase - prevents production of cortisol and aldosterone - adrenal insufficiency even after one dose pharmacokinetics weak base, pKA 4.2 A: IV only D: lipid sol, Vd 3L/kg, PB 75% M: ester hydrolyssi plasma and liver E: renal and bile, short CSHT but cant be used as infusion due to adrenal action.

Answer 4

yes R enatiomer is 10x more potent

Answer 5

barbiturate C=0 (rather than C=S) , hence weak acid hypnotic agent and anti-convulsant agent presented as powder for reconstitution

Answer 6

short acting used in ECT for this reason this is because its pKA is higher than thio so at physiological pH more is unionised. AND less protein bound than thio

Answer 7

Barbiturate used as induction anaesthetic agent, for status epilepticus and to induce coma in those with raised ICP. classically used in RSIs for its rapid onset and clear end point. presented as a powder in a glass vial with Na2CO3 and N2 air. it is reconstituted with 20ml saline to make 2.5%solution (25mg/ml). This makes an alkaline solution of ph 10.5 for promote ionised water soluble form of thiopentone. dose is 3-7mg/kg allosteric GABA modulation pharmacodynamics: - hypnosis, anaesthesis, anticonvulsive effects - other effects... - CNS: reduces BF, ICP and O2 consumption - CVS: venodilation, reduced BP, reflex tachy, myocardial depression - Resp: reduced TV, resp rate, CO2 sensivity. histamine release and bronchospams risk. - GI - garlic taste at induction, hepatic enzyme inducer. - anaphylaxis risk pharmacokinetics weak acid, pKA 7.6 , undergoes tautomerism at physiological pH and becomes unionised. A: only IV, rapid onset 30s D: 2.5L/kg Vd, 80% PB M: hepatic, some weakly active metabolites E: renal, clearance 3-5ml/kg/min. on repeated doses - 0 order kinetics hence cant be used as infusion

Answer 8

tautomerism - this is down to the S atom (phenobarbital can do this but not as readily). enables aqueous solution. less electronegative than O (phenobarbital) making it more lipid soluble - quicker onset and higher potency for anaesthesia. methyl groups are lipid soluble - promote its crossing across BBB and anaesthetic effect specific overall structure allows it to interact with GABA A receptors

Answer 9

Ketamine phencyclindine derivative chiral centre is the point at which C-N bond - this carbon has 4 different groups.

Answer 10

antiemetic really good for abtunding laryngeal reflexes for airway manipulation less risk of anaphylaxis typically better recovery

Answer 11

good for RSI as quicker onset if there a propofol allergy neuroanaesthesia - neuroprotective