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Anes. Pharm I Test 2
benzodiazepines, flumazenil, naloxone, doxapram
| Question | Answer |
|---|---|
| What are the 5 pharmacologic effects of benzodiazepines? | sedation, anxioslysis, anticonvulsant actions, skeletal muscle relaxation, antegrade amnesia |
| What is the mechanism of action of benzodiazepines? | Benzo receptors are part of GABA receptor, which, when activated cause increased binding of GABA to its receptor, opening Cl- channels = hyper polarization = inhibition of excitation of neuron |
| Benzodiazepines also have an attraction to ________ receptors in the brainstem and spinal cord | glycine |
| What is GABA? | a major inhibitory neurotransmitter in the CNS |
| What is glycine? | the major inhibitory neurotransmitter in the brainstem and spinal cord |
| Sedative and anticonvulsant effects are explained by what mechanism of action of benzodiazepines? | enhancement of GABA inhibitory effect |
| Muscle relaxation effect is explained by what mechanism of action of benzodiazepines? | glycine-like inhibition in the spinal cord motor neurons |
| Anxiolytic effect is explained by what mechanism of action of benzodiazepines? | inhibition of afferent conduction to anxiety centers at the brainstem level |
| GABA receptors have separate binding sites for what 3 things? | benzodiazepines, barbiturates, and ETOH |
| If the GABA receptor is activated at more than one site, the inhibition of the CNS to excitation is __________ | synergistic |
| Midazolam (Versed) is water soluble at what pH? | 3.5 |
| Midazolam is lipid soluble at a pH > 4. What chemical structure of midazolam accounts for this? | imidazole ring |
| Does Midazolam cause pain on IV or IM injection? Why or why not? | No; because it does not have to be dissolved in a carrier agent since it is water soluble at 3.5 pH; carrier agents are what cause the sting upon administration |
| What 2 things is midazolam IV compatible with? | opioids and LR |
| What routes can midazolam be given in? | PO, IM, IV, sublingual, intranasal (very rapid onset) |
| What are 4 uses of midazolam for the CRNA? | premedication, sedation, induction of anesthesia, maintenance of anesthesia |
| What are the effects of midazolam on the CV system? | decrease in BP r/t SVR decrease, increase in HR, no change in CO; the hemodynamic effect is exaggerated in hypovolemic patients |
| What are the effects of midazolam on the respiratory system? | dose-dependent decrease in ventilation (COPD patient show exaggerated effect), apnea possible with big doses |
| What are the effects of midazolam on the CNS? | decreases CMRO2 and cerebral blood flow |
| Can midazolam cause an EEG to become isoelectric? | No |
| Excitement occurs in less than 1% of patients who receive midazolam. What do you treat this with? | Flumazenil |
| What is the onset of midazolam? | 0.9 - 5.6 minutes (be sure to allow equilibration before redosing) |
| What is the elimination 1/2 time of midazolam? | 1 - 4 hours; may be doubled in the elderly |
| How is midazolam metabolized? | in the liver via C-P450 metabolism (patients with endured enzymes may require frequent re-dosing or higher doses) |
| What is the dosage of midazolam used for pediatric premedication? | 0.3 - 0.5 mg/kg PO (allow 30 minutes for effect) |
| What is the dosage of midazolam used for sedation? | 1 - 2.5 mg IV |
| What is the dosage of midazolam used for induction? | 0.1 - 0.2 mg/kg IV (though will probably never do this) |
| Is diazepam (valium) water soluble? What are the implications of this? | No; must be dissolved in carrier agent which causes pain on injection |
| Rapidly absorbed orally with peak concentrations in _____ | 1 hour |
| True or false: IM or IV are the best routes to give diazepam | False! will probably never give IV and should never be given IM r/t unreliable absorption |
| What are the CV effects of diazepam? | minimal decreases in BP, CO, SVR; synergistic decreases in these three with fentanyl admin; decreases are exaggerated with hyopvolemic patients |
| What are the respiratory effects of diazepam? | depresses response to CO2 (minimal depressant effects until 0.2 mg/kg), decrease in TV |
| What are the CNS effects of diazepam? | decreased CMRO2, cerebral blood flow, and ICP; relaxant effect on skeletal muscle tone; decreased MAC up to 30%; anxiolysis, amnestic; anticonvulsant prophylaxis |
| Rank the amnestic effect of the 3 benzodiazepines we have studied from greatest to least | lorazepam > midazolam > diazepam |
| What are the 2 active metabolites of diazepam? | desmethyldiazepam and oxazepam |
| Because desmethyldiazepam (a metabolite of diazepam) is only slightly less potent than diazepam, drowsiness returns ________ after admission | 6 - 8 hours; causes prolonged effect of diazepam |
| What is the elimination 1/2 life of diazepam? | 21 - 37 hours; increases with age; increases with cirrhosis of liver; prolonged by cimetidine (Tagamet) |
| What is the dosage of diazepam in adults and when does it reach its peak effect? | 10 - 15 mg PO; peak effect 55 minutes after admin |
| Is Lorazepam (Ativan) soluble in water? | No; must be dissolved in carrier agent (polyethylene glycol or propylene glycol) |
| What routes of administration can lorazepam be given in? | PO, IM, IV |
| Due to Lorazepam's slow onset and prolonged duration of action, it's use is limited. Is it useful in outpatients for anesthetic purposes? What patient population is it useful in? | Not good for outpatients r/t long effects; good for heart surgery patients because of long effects |
| How long can antegrade amnesia last with administration of lorazepam? | up to 6 hours |
| Does lorazepam have active or inactive metabolites? | inactive |
| Why does lorazepam have a longer clinical effect than diazepam? | lorazepam is more slowly released from GABA receptors |
| What is the dose of lorazepam? | 50 mcg/kg (up to 4 mg) |
| What is the peak concentration of lorazepam? | 2 - 4 hours |
| What is the elimination 1/2 life of lorazepam? | 10 - 20 hours |
| What is the mechanism of action of flumazenil? | competes with benzodiazepines for the benzodiazepine receptor sites on GABA receptors |
| Reversal of benzodiazepine effects with flumazenil is buffered by the _____________ | weak agonist effects |
| In contrast to nalaxone, what will you NOT see with flumazenil administration? | acute anxiety, stress response, HTN, tachycardia |
| What could you see with administration of flumazenil in those patients who are on seizure treatment? | withdrawal seizures |
| What is the initial dose of flumazenil? | 0.2 mg IV (8 - 15 mcg/kg) |
| What is the onset of flumazenil? | 2 minutes |
| What is the additional dose(s) of flumazenil? | 0.1 mg IV (up to total of 1 mg) |
| What is the duration of flumazenil? | 30 - 60 minutes |
| If the goal is to decrease the sedative effect of a benzodiazepine, what would the dose of flumazenil be? | 0.3 - 0.6 mg |
| If the goal is to abolish the benzodiazepine effect altogether, what would the dose of flumazenil be? | 0.5 - 1 mg |
| What is the mechanism of action of naloxone? | the attraction of naloxone for the receptor displaces the opioid from the receptor. the antagonist then binds with the receptor and inactivates it. |
| What receptors does naloxone respond to the most? | mu receptors more than kappa and delta |
| What are the clinical indications for the use of naloxone? | opioid overdose, post op ventilatory depression due to maternal opioids, adverse effects of spinal and epidural opioids |
| What is the dose of naloxone? | 0.5 - 1 mcg/kg q 3 - 5 minutes |
| What is the onset and duration of naloxone? | onset: 1 - 3 minutes; duration: 30 - 45 minutes |
| Where is naloxone metabolized primarily? | the liver |
| What are the positive effects of the administration of naloxone? | if titrated properly, ventilatory depression caused by opioids can be reversed without weakening analgesic effect; return of airway reflexes |
| What are the negative effects of the administration of naloxone? | acute pulmonary edema, sympathetic stimulation - pain, tachycardia, ventricular irritability, HTN, N/V |
| Can naloxone cross the placenta? | Yes; it can cause withdrawal symptoms in neonate if opioid-abusing mother |
| If a patient is dependent on opioids and appears normal on them and a CRNA administers too large of a dose of opioids and needs to reverse the adverse effects, what will happen with naloxone administration? | it may precipitate abstinence syndrome |
| What 6 patient populations should you be careful with and possibly avoid naloxone administration? | critically ill, CAD, preexisting lung disease, CHF, cardiac surgery, opioid dependence |
| What is doxapram? | a CNS stimulant |
| What is the mechanism of action of doxapram? | stimulates hypoxic drive via the activation of the chemoreceptors in the carotid bodies |
| Does doxapram primarily produce an increase in respiratory rate or tidal volume? | tidal volume, produces small increase in respiratory rate |
| What are 2 indication for the use of doxapram? | COPD patients who breath based on hypoxic drive but need supplemental O2; ventilatory depression and CNS depression due to drugs |
| What is the dose of doxapram? | 0.5 - 1 mg/kg (max 4 mg/kg) |
| What is the onset and duration of doxapram? | onset: 1 minute; duration: 5 - 10 minutes |
| Where is the primary site of metabolism of doxapram? | the liver |
| What are the CNS effects of doxapram? | stimulates hypoxic drive r/t activation of chemoreceptors in carotid; confusion, dizziness, seizures, increased sympathetic outflow, vomiting, increased body temperature |
| What are the respiratory effects of doxapram? | increases minute volume by increasing Vt and slightly increasing RR, increases O2 consumption, wheezing, tachypnea |
| What are the CV effects of doxapram? | increased sympathetic stimulation, HTN, tachycardia, cardiac dysrhythmias |
| What are 7 patient populations in which you should be careful with and possibly avoid administration of naloxone? | seizure disorder, cerebrovascular disease, acute head injury, coronary artery disease, HTN, asthma, patients who have been given halothane |
| 1 mg/kg of doxapram makes the body think that its PaO2 is what? | 38 mmHg |
Created by:
Mary Beth
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