 | Term | Definition |
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Nitrous Oxide |
Inhaled anesthetic; good analgesia; rapid onset & recovery |
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Halothane |
First halogenated inhalational anesthetic; medium rate of onset & recovery; sensitizes heart to epi-induced arrhythmias |
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Enflurane |
Inhaled anesthetic; Less soluble than halothane; more hypotension and respiratory depression; BP decreases on induction; CO fall w/ rise in central venous pressure; more neuromuscular depression; less liver damage; nausea on recovery |
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Isoflurane |
Inhaled anesthetic; Medium rate of onset & recovery; less CV or respiratory depression than enflurane; used for induction and maintenance of anesthesia; has been largely replaced by Desflurane |
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Methoxyflurane |
Inhaled anesthetic; Considered widely obsolete now; slow onset & recovery; caused renal dysfunction (extensive hepatic/renal metabolism released F- ion) |
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Desflurane |
Inhaled anesthetic; Most rapid onset of action and recovery; very irritating to the airway; poor induction agent; used for maintenance of anesthesia |
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Sevoflurane |
Inhaled anesthetic; Rapid onset of action & recovery; widely used for outpatient surgery; not irritating to airway; useful induction agent, esp w/ children |
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Toxicity - Malignant Hyperthermia |
Occurs esp when halogenated GA used w/ succinylcholine; Treat w/ Dantrolene immediately! |
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Toxicities of Halothane |
May sensitize heart to Epi (causes arrhythmias); rare cases of postoperative hepatitis |
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Toxicities of Methoxyflurane |
Fluoride release during metabolism may cause renal insufficiency after prolonged exposure |
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Toxicities of Nitrous Oxide |
Megoblastic anemia may occur after prolonged exposure due to decreases in methionine synthase activity (Vit B12 deficiency) |
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Why do GA commonly cause nausea and vomiting after recovery? |
GAs effect the chemoreceptor trigger zone and brainstem vomiting center; prevent by taking Ondansetron |
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Thiopental |
Intravenous anaesthetic; most frequently used barbiturate; short acting, w/ long elimination half-life; most commonly used induction agent; rapid unconsciousness; good amnesia, poor analgesia, poor m relaxation; pleasant induction |
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Thiopental - MOA |
Binds to GABA a receptor; increases chloride ion flux into cell; stimulates inhibitory neuronal systems |
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Thiopental - Effects on CNS |
Reduces cerebral metabolism and oxygen utilization, reduces cerebral blood flow (blood volume and ICP, but not cerebral profusion pressure), protects brain against hypoxic/ischemic injury |
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Thiopental - Effects on CV |
Direct: BP, vascular resistance and CO may decrease transiently; Venodilation (due to increased venous capacitance) may result in hypotension in pats in shock; Acts as direct depressant which lowers myocardial contractility; HR increases via barostatic reflex |
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Thiopental - Effects on Respiratory |
Depress respiration and responses to hypoxemia & hypercapnia; M relaxants required due to retention of tracheal/laryngeal reflexes (hiccups); Depresses mucociliary clearance |
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Thiopental - Effects on Kidney, Liver and GI track |
Decreased renal blood flow and glomerular filtration rate |
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Midazolam and Lorazepam |
Benzodiazepines as intravenous anaesthetics; best amnestic agents; excellant anxiolytics, anti-convulsants, and m relaxants |
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MOA for Benzodiazepines |
Bind to distinct sites on GABA a receptor; sensitize the channel |
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Midazolam - Physiochemical Properties |
At pH = 3.5, allows imidazole ring to remain open and maintains water solubility; at pH = 6.2, ring closes and the basic drug becomes 94% unionized, increasing lipid solubility and decreasing time to onset of action |
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Midazolam - Effects on CNS |
Dose-related effects on cerebral metabolism and blood flow; raises seizure threshold; antegrade amnesia; has antagonist = Flumazenil |
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Midazolam - Effects on CV |
Hypotensive effect, exaggerated in hypovolemia |
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Midazolam - Effects on Respiration |
Hypnotic dose causes apnea; Amnestic dose gives minimal depression |
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Opioids |
Intravenous anaesthetics; Analgesics w/ some hypnotic action, however, not reliable for amnesia; used for premedication, induction and maintenance of anesthesia, and postoperative pain control |
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Opioids - MOA |
Analgesic action via Mu receptors (slow, G proteins) |
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Opioids - Effects |
Pruritis (itchiness); Chest wall rigidity (supresses ability to breath b/c decreases sensitivity to CO2 buildup) |
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Remifentanil |
Intravenous anaesthetic; Opioid; Shorest acting; termination is due to elimination (not redistribution); Metabolism via non-specific esterases; commonly used as neuroanesthetic |
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Ketamine |
Intravenous anaesthetic; Arylcyclohexylamine - like PCP; causes "dissociative" anesthetia |
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Ketamine - MOA |
Non-competitive NMDA antagonist; only IV agent - works predominately via inhibition of stimulatory neuronal systems |
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Ketamine - Effects on CNS |
Unpleasant dreams, hallucinations and delirium; Increaes ICP 1-60mmHg; Benzos, barbs, and N2O reduce incidence of these effects |
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Ketamine - Effects on CV |
Central sympathetic stimulation results in increased HR, BP, Epi and NE levels; direct myocardial depressant |
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Ketamine - Effects on Respiratory |
Small doses given slowly result in minimal ventilatory depression; profound analgesia reduces airway reflexes; Rapid infusion, or combo w/ benzos, potentiates depressant effects; sympathetic stim results in bronchodilation via direct smooth m effects |
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Ketamine - Effects on salivary/tracheobronchial secretions |
Markedly increased; reduced w/ atropine |
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Ketamine - Effects on mm |
Nonpurposeful tonic, clonic mvmts; make determination of anesthetic depth difficult (at high doses); Nystagmus may also occur |
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Etomidate |
Intravenous anesthetic; Imidazole derivative |
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Etomidate - MOA |
Activates GABA a receptors indirectly |
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Etomidate - Effects on CNS |
Lowers CBF and ICP; Lowers CMRO2 |
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Etomidate - Effects on Respiration |
Minimal ventilatory depressant; lower incidence of apnea |
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Etomidate - Effects on CV and MS system |
Minimal changes in all parameters; myoclonus |
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Propofol |
Originally designed as an organic solvent (cleaner!); Diisopropyl phenol; Intravenous anesthetic |
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Propofol - MOA |
Some action at GABA a complex (binds to a distinct site); May enhance Cl- conductance at glycine receptors |
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Propofol - Effects on CNS |
Reduces CBF and metabolism; Autoregulation maintained, along w/ resonse to changes in CO |
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Propofol - Effects on CV |
Decreased mean BP, vascular resistance, HR and CO; central venous pressure unchanged |
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Propofol - Effects in general |
Burns on injection; Extremely fast-acting; Clearance exceeds hepatic blood flow; Euphoric (pats feel better next day); Referred to as "Mild of Amnesia" |
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Propofol - Disadvantage |
No antagonist to use if given too much!!! |
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