Pharm - anesthetics Flashcards
Halothane
inhaled general anesthetic
Mech:
SE: Malig. hyperthermia, hepatic toxicities, tachycardia/arrhythmia w/ epinephrine,
(good smell, does NOT irritate upper airways).
*not used anymore.
Nitrous Oxide
inhaled general anesthetic, but used mostly as analgesic.
*LOW potency (105 MAC), can’t be used alone.
*good smell, does NOT irritate upper airways.
SE: distend closed air spaces
Contraind: methionine synthase path def., pneumothorax, high ICP, pulm HTN, 1st trimester pregnancy
Enflurane
inhaled general anesthetic
Mech:
*bad smell
SE: Malig. hyperthermia, upper airway irritation, seizure activity on EEG, renal toxicity, possible hepatotoxicity.
Isoflurane
Inhaled general anesthetic, cheapest
*bad smell
SE: malig hyperthermia, upper airway irritation & laryngospasm, coronary steal syndrome (potent vasodilation => shunt blood away from already ischemic areas), possible hepatotoxicity
Desflurane
inhaled general anesthetic, expensive
0 metabolism -> rapid induction & fastest recovery.
*bad smell -> not used for induction (get coughing)
SE: malig hyperthermia, upper airway irritation => transient BP & HR rise
Sevoflurane
inhaled general anesthetic, expensive
* smooth induction, & fast recovery.
SE: malig hyperthermia, possible hepatotoxicity
*good smell, does NOT irritate upper airways
Xenon
newer inhaled general anesthetic
SE: NO malig. hyperthermia
Thiopental
IV barbiturate, (RAPID anesthetic/inducing agent & sedative)
*excellent hypnosis, poor amnesia, no analgesia.
Mech: activate GABA & chloride channels -> inhibit post-synaptic neurons => depress RAS
SE: hypotension (mild), transient apnea worse w/ opioids, cerebral vasoconstriction, crystallization in veins -> necrosis
Methohexital
IV barbiturate, (RAPID anesthetic/inducing agent & sedative)
*excellent hypnosis, poor amnesia, no analgesia.
Mech: activate GABA & chloride channels -> inhibit post-synaptic neurons => depress RAS
SE: hypotension (mild), transient apnea worse w/ opioids, cerebral vasoconstriction, crystallization in veins -> necrosis
Midazolam (Versed)
IV or oral Benzodiazepine agonist;
anxiolytic, sedative & anesthesia inducer; & anti-convulsant.
* Excellent anterograde amnesia + calming, no analgesia.
Mech: increase Cl- gating of GABA (post-synaptic n. endings)
*P450 metabolism, SLOW induction, long context-dep. 1/2 life.
SE: minimal heart & ventilation effects
Diazepam (valium)
IV or oral benzodiazepine agonist (sedative) & anticonvulsant;
* Excellent amnesia & calming esp. perioperative, no analgesia;
- onset slower than midazolam.
Mech: increase Cl- gating of GABA (acts on post-synaptic n.)
SE: *minimal heart & ventilation effects
Lorazepam (Ativan)
IV or oral benzodiazepine (sedative), esp. perioperative.
* #1 amnesia & calming, no analgesia; *very SLOW induction.
Mech: increase Cl- gating of GABA (acts on post-synaptic nn)
SE: *minimal heart & ventilation effects
Flumazenil
IV benzodiazepine antagonist
* Excellent amnesia, unpredictable hypnosis, no analgesia
Mech: increase Cl- gating of GABA
Propofol
good bc low risk for post-Tx nausea/vomiting
IV general anesthetic (#1!) & inducing agent; for total IV anesthesia.
Mech: slows GABA dissociation from Rs –> membrane hyperpol.
painful on injection into small veins
Metab: hepatic
SE: decrease SVR, BP & inotropy -> possible bradycardia/asystole (give anti-ACh), apnea & bronchodilation, EEG burst suppression;
*risk bacterial infection or allergic rxn
Etomidate
IV general anesthetic & inducing agent
*excellent hypnosis, poor amnesia, no analgesia.
Mech: enhance effects of GABA (inhibitory), short 1/2 life.
SE: adreno-cortical suppresion, minimal heart effects, myoclonus, cerebral vasoconstrictor & EEG excitation, post-op vomiting common. Painful injection.
Ketamine
IV general anesthetic & inducing agent;
*excellent analgesia, good hypnosis & amnesia.
Mech: NMDA Rs, Monoamine Rs, opioid Rs, mACh Rs, & volt-gated Ca2+ channels (NOT GABA)
SE: hallucinations, sympathetic CNS stimulation, myoclonus, slow nystagmus, emergence delirium (esp. F)
NOT for pts w/: pulmonary HTN or high ICP
Dexmedetomidine
IV sedative agent or w/ other induction drugs.
Mech: alpha-2 agonist –> negative feedback to presynaptic neuron
slow onset, injection = painful.
SE: hypotension, bradycardia.
Lidocaine
injected local anesthetic for nerve block & regional analgesia;
Mech: amide, FAST ONSET
SE: cauda equina syndrome if used as spinal block
Mepivacaine X
injected local anesthetic for nerve block & regional analgesia;
Etidocaine
injected local anesthetic for nerve block and regional analgesia,
Mech: amide
SE: ~cardiotoxic
Prilocaine
injected local anesthetic for nerve block and regional analgesia;
Mech: amide
SE: methemoglobinuria
Ropivacaine
injected local anesthetic for nerve block and regional analgesia;
Mech: amide, S-enantiomer so less toxic
SE: allergic rxn more likely
L-bupivacaine
injected local anesthetic for nerve block and regional analgesia;
Mech: amide ester => S-enantiomer (less cardiotoxic),
*LONGest duration of action!
SE: dysrhythmogenic
Articaine. X
injected local anesthetic for dental analgesia;
Mech: ester & amide
Benzocaine. X
spray local anesthetic for topical use;
Mech: ester
Cocaine
topical local anesthetic, usually used in ENT;
Mech: ester
Procaine. X
injected local anesthetic for nerve block and regional analgesia;
Mech: ester
Chloroprocaine. X
injected local anesthetic for nerve block and regional analgesia;
Mech: ester
Tetracaine
local anesthetic, esp as intrathecal.
Mech: ester
SE: ~cardiotoxic
risks/side effects of barbiturates: (4)
(methorexital, thiopental)
Heart: hypotension/decreased BP
Lungs: upper airway reflexes NOT depressed (be ready to control)
Skin/Soft tissue: necrosis if IV not properly placed!
Brain: decreased ICP and isoelectric EEG
“MAC”
= “Mean Alveolar Concentration” at 1 atm that induces anesthesia in 50% of test subjects.
*used to compare potencies of inhaled anesthetics,
Low # = most potent.
Epinephrine
Most potent vasoconstrictor, used to reduce systemic absorption of local anesthetic.
*SE: HR increase (immediate if intravascular!)
3 major take-aways regarding ALL inhaled anesthetics
- bc of steady state, alveolar partial P = partial P in brain
- Higher % INSPIRED [ ] increases –> reach desired % faster
- Better ALVEOLAR VENTILATION (rate & depth) –> faster increase in Fa
(Fi ~= Fa)
Mech. of action of volatile anesthetics
block Na channels, stimulate GABA & background K+ channels;
Best use pattern:
Sevofluorane for induction, Desfluorane for maintenance.
What these mean for local anesthetics:
- pKa
- protein binding
- lipid solubility
- Lower pKa = faster the onset of action
- more protein bounding = longer duration of action
- more lipid soluble = more potent (also more cardiotoxic)
Side effects of Local Anesthetics
- Allergic reaction (esp. esters, or preservatives)
- Cardiotoxicity: 1st HTN, high HR, 2nd: low CO, hypotension
- Neurotoxicity: 1st circumoral numbness, lightheaded, 2nd tonic-clonic convulsions, 3rd unconsciousness, respiratory arrest
* *treat w/ lipid emulsion in case of toxicity!
General mech of action of local anesthetics
- Block Na+ channels: prevent depolarization & repol. for APs
- Anti-inflammatory: via GPCRs, decrease PMN infiltration.
Amide vs amine local anesthetics
Amides: (2 I’s in the name) allergies rare, more STABLE, hepatic metab.
Esters: (one i in the name) ALLERGIES more common, less stable, breakdown by plasma cholinesterase.
