Pharmacology Exam 2 Flashcards
Let's get it ladies! I feel the A!
Brand Name For:
Midazolam
Diazepam
Lorazepam
Dexmedetomidine
Midazolam (Versed)
Dizepam (Valium)
Lorazepam (Ativan)
Dexmedetomidine (Precedex)
How does the GABAA Receptor work?
- Ligand gated ion channel (Cys- loop Family)
- Cl selective channel allows influx into cell or hyperpolarization.
What is the action of GABAA?
Inhibitory neurotransmitter when stimulated induces unconsciousness, depression of spinal reflexes & amnesia
Alpha1 and Alpha5 containing GABAA receptors are important for _____.
Alpha 2 and Alpha 5 containing GABA A receptors are important for _____.
Alpha 1 & 5: Sedation
Alpha 2 & 5: Anxiolytic
What is the most abundant GABAAreceptor subunit, and where is it located?
Alpha 1 subunit accounts for approximately 60% of GABAAreceptors in the brain.
Where are 2subunits located?
Principally in the hippocampus and amygdala
What is one of the most important advantages of Propofol compared with other sedative hypnotics?
More rapid return of consciousness with minimal residual CNS effects.
What is the uniqueness is shape about Propofol compared to thiopental, etomidate, and ketamine?
It is not a chiral compound
How does Diprivan and generic Propofol differ?
- Diprivan uses the preservative disodium edetate with sodium hydroxide to adjust the pH to 7 to 8.5
- Generic formulation of Propofol uses the preservative sodium metabisulfite and has a lower pH (4.5 to 6.4).
Though Propofol is not recommended with any other drug lidocaine has been frequently added to Propofol to prevent pain, mixing these two puts your patient at risk of?
A fat emboli leading to a pulmonary embolism. Mixing lidocaine with Propofol may result in coalescence of oil droplets.
How does the prodrug Aquavan compare with Propofol?
- Slower onset
- Large volume of distribution
- Higher potency
- Increased water solubility
- The formaldehyde byproduct causes and unpleasant dysesthesia (burning) sensation in the genital area.
Which receptors do Propofol work on?
GABAA receptors although it has activity at glycine receptors. Ligand gated channels.
True/False, spinal motor neuron excitability is altered by Propofol?
False, spinal motor neuron is not altered by Propofol, suggesting that immobility during Propofol anesthesia is not caused by drug-induced spinal cord depression.
What enzyme is important in the metabolism of Propofol?
cytochrome P450
Elimination half-time and the context sensitive half time for Propofol infusion lasting up to 8 hours.
- Elimination half time = 0.5-1.5 hours
- Context-sensitive half-time after 8 hours= less than 40 minutes.
True/False Pulmonary uptake of Propofol is significant and influences the initial availability of Propofol, and most of the drug that undergoes pulmonary uptake during the first pass is released bake into the circulation.
True
What is the major metabolic pathway for Propofol?
Glucuronidation
True/False. Patients with cirrhosis of the liver have impaired elimination of Propofol?
-False, there is no evidence of impaired elimination in patients with cirrhosis of the liver.
Concentration of Propofol at the time of awakening are similar in alcoholic and normal patients.
True/False. Renal dysfunction influences the clearance of Propofol.
False
How does Propofol in older adults compare to younger adults?
Patients older than 60 years of age have decreased rate of plasma clearance
True/False Propofol crosses the placenta?
True. Propofol readily crosses the placenta but is rapidly cleared from the neonatal circulation.
What are the blood levels needed for unconsciousness and awakening with Propofol.
- Unconsciousness = 2 to 6 mcg/mL
- Awakening = 1 to 1.5 mcg/mL
How do induction doses for the elderly patient and children compare with young adults?
- Children require higher induction doses of Propofol on a mg/kg basis (due to larger central distribution volume and increased clearance rate.
- Elderly patients require a lower induction dose (25 to 50% decrease) due to a smaller central distribution volume, decreased clearance rate, and increased pharmacodynamic activity.
What makes Propofol a readily titratable drug for IV sedation?
The short context-sensitive half time and the short effect-site equilibration time.
What are some beneficial properties of Propofol?
- Antiemetic effects
- Antipruritic effects- 10 mg IV
- Does not produce seizures on the EEG
- Does not prolong the QTc interval
- Significant decreases in intraocular pressure that occurs immediately after intubation
- Provides control of stress responses
- Decreases the prevalence of wheezing after induction of anesthesia and tracheal intubation.
- Reliable pharmacologic properties for a computer assisted device SEDASYS for colonoscopy and esophagogastroduodenoscopy.
Propofol dose for a MAC procedure?
25 to 100 mcg/kg/min IV produces minimal analgesic but marked amnestic effects.
Induction dose of propofol and BP expectations.
2-2.5 mg/kg expect to see a 25-40% drop in BP
Typical maintenance dose of Propofol for GA?
100 to 300 mcg/kg/min
Which sedative-hypnotic can be used to treat postoperative N/V?
- Propofol at sub hypnotic doses of (10-15 mg IV)
- However, it does not inhibit gastric emptying and is not considered a prokinetic (control acid reflux) drug.
How does Propofol affect cerebral metabolic rate for oxygen (CMRO2), cerebral blood flow, and intracranial pressure (ICP).
It decreases all of them
Changes in the end-tidal P2 (P2) _______ (parallel/inversely related) to the cerebral blood flow velocity (CBFV) during infusion of Propofol or midazolam.
Parallel
True/False. High doses of Propofol can produce burst suppression?
True
Normally cortical somatosensory are not significantly modified with Propofol alone, but the addition of ______or a ______ results in decreased amplitude.
Nitrous oxide or a volatile anesthetic.
True/False. Propofol and fentanyl can have memory impairment?
False. Propofol has the same memory impairment as midazolam but fentanyl has none.
How does Propofol affect systemic blood pressure, CO, SVR, and HR?
- Systemic BP, CO, and SVR decrease
- HR remains unchanged
What are some non-medication actions that can reverse the decreased BP effects of Propofol?
- Stimulation by direct laryngoscopy and intubation of the trachea.
- On the other hand, Propofol blunts the hypertensive response to placement of a LMA.
What causes the relaxation of vascular smooth muscle produced by Propofol?
It’s due to inhibition of sympathetic vasoconstrictor nerve activity.
In which patient populations are the blood pressure effects of Propofol exaggerated?
- Hypovolemic
- Elderly patients
- Patients with compromised left ventricular function
True/False nitrous oxide alters the cardiovascular effects of Propofol.
False
True/False. Propofol anesthesia enhances the pressor response to intravenous ephedrine.
True
Why is Propofol usually the drug of choice for ablative procedures?
Propofol does not alter sinoatrial or atrioventricular node function in normal patients or in patients with Wolff-Parkinson White syndrome (extra electrical pathway in the heart, causing a rapid heartbeat).
Risk of bradycardia-related death during Propofol anesthesia has been estimated to be:
1.4 in 100,000.
Treatment for Propofol-induced bradycardia?
Direct beta-agonist such as epinephrine
What happens when atropine is administered after Propofol induced bradycardia?
There is a decreased responsiveness to atropine and cannot be overcome by larger doses of atropine. This suggest Propofol may induce suppression of sympathetic nervous system activity.
How does Propofol affect tidal volume and frequency of breathing.
A decrease in tidal volume and frequency of breathing is seen. Can cause a downward shift of the ventilatory response curve to hypoxia.
How is the urine affected with prolonged infusions of Propofol?
- May result in excretion of green urine= presence of phenols in urine.
- Cloudy urine= increase in urinary acid that crystallize in a low pH and temp of urine.
SN- This is not indicative of adverse of renal effects of Propofol.
True/False. Propofol does not normally affect hepatic or renal function.
True
-Though prolonged infusion are associated with hepatocellular injury.
How does Propofol affect coagulation?
It does not alter tests of coagulation or platelet function but inhibits platelet aggregation induced by proinflammatory lipid mediators.
Side effects of Propofol?
- Bradycardia
- Risk of infection
- Pain on injection
- Hyperglyceridemia with prolonged administration
- Potential for pulmonary embolism.
Allergenic components of Propofol?
Phenyl nucleus and diisopropyl side chain
Diprivan caused bronchoconstriction in patients with allergies what products did it contain?
- Soybean oil
- Glycerin
- Yolk lecithin
- Sodium edetate
______ has been described in pediatric and adult patients receiving prolonged high-dose infusions of Propofol for longer than 24 hours.
Lactic acidosis (“Propofol infusion syndrome)
You gave your patient Propofol for induction and now they have unexpected tachycardia, what lab should obtain.
- ABG and serum lactate- for metabolic lactic acidosis.
- Early stages are reversible with d/c of Propofol
What is the differential diagnosis when Propofol induced lactic acidosis is suspected?
- Hyperchloremic metabolic acidosis associated with large volume infusion of 0.9 % saline
- Metabolic acidosis associated with excessive generation of organic acids such as lactate (release of tourniquet) and ketones (diabetic acidosis).
Tidbit: Measurement of the anion gap and individual measurements of anions and organic acids will differentiate hyperchloremic metabolic acidosis from lactic acidosis.
Propofol supports the growth of which bacteria?
- Pseudomonas aeruginosa
- E. coli
- Candida albicans
The contents of an opened ampule of Propofol must be discarded if they are not used within ____ hours.
6
Which antioxidant does Propofol resemble?
Vitamin E. Propofol contains a phenolic hydroxyl group that scavenges free radicals and inhibits lipid peroxidation.
Why is Propofol beneficial in disease states such as acute lung injury?
In acute lung injury, peroxynitrite formation is thought to play an important role. Propfofol scavenges peroxynitrite which is one of the most potent reactive metabolites.
Most commonly reported adverse event associated with Propofol administration awake patients.
Pain on injection. Changing the composition of the carrier fat emulsion for Propofol to long and medium chain triglycerides decreases the incidence of pain on injection.
True/False. Propofol triggers malignant hyperthermia.
False. Propofol does not trigger malignant hyperthermia.
Why is Propofol not suited for patients undergoing stereotactic neurosurgery?
In this surgery the symptom is required to identify the correct anatomic location and Propofol can cause temporary abolition of tremors in patients.
What are risk factors of PRIS?
- Doses >4mg/kg/hr
- Durations >48hr
- High fat low carb intake
- Errors of Mitochondrial fatty acid oxidation
- Catecholamines infusion & Steroid administration
What are complications of PRIS? What is the treatment?
Propofol Related Infusion Syndrome: Profound bradycardia that can lead to asystole, Acute renal injury, Hyperkaliemia, metabolic acidosis, rhabdomyolysis, lipidemia, Hepatomegaly, hyperthermia, hypoxia, pulmonary edema.
Tx: Stop the drip
What can be done to reduce the pain on injection when administering Propofol?
Dr. Furgang’smodified Bier Block: Inject 40-60mg lidocaine2% in the vein prior to injection of propofol Maintain in the vein for 30-45 sec before release
What is the standard of care to appropriately identify respiratory depression in Propofol during MAC cases?
EtCO2. SaO2 monitoring is not enough as it displays time lag when desaturations are present it is a late sign
What is the chemical makeup of etomidate?
Carboxylated imidazole-containing compound that is chemically unrelated to any other drug used for the IV induction of anesthesia.
What makes etomidate similar to midazolam in that it is water soluble at an acidic pH and lipid soluble at physiologic pH.
The imidazole nucleus
Etomidate is unique among injected and inhaled anesthetics in being administered as a single isomer. The anesthetic effect of etomidate resides predominately in the ____ isomer.
-R(+) isomer. Five times more potent as the S(-) isomer
Etomidate is an agonist of which receptor?
GABAA.
Which Isomer is more active in Etomidate?
the Right (+) (5X more potent than S) isomer has hypnotic properties
How is Etomidate metabolized?
Liver & plasma esterases
Which medication can be used as antagonism of steroid induced psychosis?
Etomidate
Etomidate penetrates the brain rapidly and reaches peak levels after ___ minute(s) of injection.
1 minute
About ___ % of etomidate is bound to albumin. Independently of the plasma concentration of the drug.
76%.
How is etomidate metabolized?
Hepatic microsomal enzymes and plasma esterases are responsible for the hydrolysis of the ethyl ester side chain to its carboxylic acid ester, resulting in a water-soluble, inactive compound.
What is the elimination half-time of etomidate?
2 to 5 hours
Etomidate is a ______ (low/high) hepatic extraction drug.
High hepatic extraction. Hepatic blood flow may alter metabolism.
Involuntary myoclonic movements are common during the induction period as a result of…
Alteration in the balance of inhibitory and excitatory influences on the thalamocortical tract.
How can you decrease the frequency of myoclonic-like activity.
Administer an opioid before etomidate
True/False. Analgesia is produced by etomidate.
False etomidate or barbs do not produce analgesia.
Two reasons to administer an opioid before etomidate.
- Myoclonic-like activity can be attenuated when an opioid (benzo or fentanyl) is administered first.
- No analgesia effects so opioids help to blunt the hemodynamic responses evoked by direct laryngoscopy and tracheal intubation.
What is a dogma about etomidate and nausea and vomiting.
Widely viewed that postoperative N/V is increased in patients receiving etomidate for induction of anesthesia. However, there was no increased incidence of N/V in the first 24 hours after surgery when compare with Propofol.
What are the CNS side effects of etomidate?
- Potent direct cerebral vasoconstrictor that decreases cerebral blood flow and CMRO2. ICP is lowered.
- Frequency of excitatory spikes on the EEG is greater (caution in patients with seizures).
- May activate seizure foci (caution in patients with focal epilepsy).
True/False. Etomidate can be used to terminate status epilepticus.
True. Etomidate has anticonvulsant properties.
Cardiac stability is seen in etomidate with administration of ___ mg/kg IV. However, when the induction dose is _____ mg/kg IV, significant decreases in systemic blood pressure and cardiac output may occur.
- 0.3 mg/kg
- 0.45 mg/kg
What can you give to reverse decreases in developed tension in isolated cardiac muscle in patients undergoing a CABG or cardiac transplantation caused by etomidate?
Beta adrenergic stimulation (epinephrine, norepinephrine)
True/False. Etomidate does not result in detrimental effects when accidently injected into an artery.
True
Etomidate can cause a decrease in tidal volumes but is offset by _______ (increases/decreases) in the frequency of breathing.
Increases. Only lasts about 3-5 minutes
Inclusion of _____ in the preoperative medication can suppress spike activity on the EEG when giving etomidate.
Atropine
How does etomidate cause myoclonus?
Disinhibition of subcortical structures that normally suppress extrapyramidal motor activity.
How does etomidate cause adrenocortical suppression?
Producing a dose-dependent inhibition of the conversion of cholesterol to cortisol. Can last up to 8 hours
Why should you avoid etomidate in patients experiencing sepsis or hemorrhage?
Etomidate causes adrenocortical suppression and this population needs an intact cortisol response.
What is one of the main complications with Etomidate administration?
ADRENOCORTICAL SUPPRESSION: 4-8 hrs after induction. @ higher risk when several doses are used.
TX: IV steroids.
also high incidence of PONV
Etomidate has a ____ (high/low) incidence of allergic reactions.
Low. The drug does not release histamine from tissue mast cells.
True/False. Retrograde amnesia is altered by benzodiazepines
False. Anterograde (encoding of new information) is altered by benzos
What is used benzo overdose?
Flumazenil (Romazicon)
A 1, 4imidazobenzodiazepine competitive antagonist/ shorter elimination ½ of 1hr may need redosing with long acting. Onset 1-2 mins; duration 30-60mins;
Max dose total 3-5mg adults/ 0.05mg/kg pedi if pt unresponsive benzo is not the problem or its treated too late.
How do benzodiazepines bind to a GABA receptor?
At an allosteric site, (located between the alpha & gamma subunits) not directly. To enhance the affinity of the receptors for GABA.
True/False. Benzodiazepines, barbiturates and alcohol can act on a single receptor at different binding sites to increase GABAAreceptor-mediated inhibition.
True. This is consistent with the clinical use of benzodiazepines as the first-choice drugs for detoxification from alcohol.
All benzodiazepines are highly ______ (lipid soluble/water soluble) and are highly bound to plasma proteins, especially albumin.
Lipid Soluble
Most benzodiazepines produce a flat (isoelectric) EEG except.
Midazolam
Most common side effects of benzodiazepines?
Fatigue & Drowsiness
If a patient is chronically treated with intermediate and long acting benzodiazepines like lorazepam and diazepam, sedation that could impair performance usually subsides in __ weeks.
2
What are patient instruction for taking benzodiazepines?
-Ingest benzos before meals in the absence of antacids because meals and antacids may decrease absorption from the GI tract.
What are the withdrawal symptoms of benzodiazepines?
-Irritability, Insomnia, tremulousness
Elimination half-life of midazolam, lorazepam, diazepam
- Short acting < 6 hours- Midazolam =1-4 h
- Intermediate acting = 6-24 h – Lorazepam = 10-24 h
- Long-acting > 24h Diazepam= 21-37 h
-This onset reflects the elimination half-life of the drug
What is the time frame for withdrawal systems of short acting and long acting benzodiazepines?
- Shorter = 1-2 days
- Longer= 2-5 days
- This onset reflects the elimination half life of the drug
True/False. The sedative effects of midazolam are more potent than amnestic effects?
-False, amnestic effects are more potent.
Is midazolam lipid soluble or water soluble and how does the shape help in aqueous solutions?
Midazolam is a water-soluble benzo with an imidazole ring (open) that accounts for stability in aqueous solutions and rapid metabolism.
At physiological pH the ring closes and midazolam in the bloodstream is 90% lipid soluble.
The imidazole ring makes midazolam unlike any other
Approximately ____ % of an orally administered dose of midazolam reaches the systemic circulation.
50%
Which populations have an increase volume of distribution when midazolam is administered? (Think more adipose tissues).
- Elderly
- Morbidly obese patients.
How is midazolam metabolized?
Metabolized by CYP3A4 enzymes in hepatic and small intestine.
What drugs slow the metabolism of midazolam?
- Fentanyl- CYP3A4 influemce the metabolism of fentanyl
- Antifungal drugs
- Cimetidine
- Erythromycin
- Calcium channel blockers
-These drugs inhibit the metabolism of cytochrome P450
Is clearance of midazolam altered by renal failure?
NO, but it is in hepatic dysfunction
How does midazolam affect CMRO2, cerebral blood flow, and ICP?
- Decrease in CMRO2 and cerebral blood flow.
- No change in ICP with doses 0.15 to 1.27 mg/kg IV. Push slowly in patients with head trauma, can cause an increase in ICP.
Most common side effect of midazolam?
-Depression in ventilation caused by a decrease in hypoxic drive.
How does benzodiazepines affect the swallowing reflex and upper airway activity?
Depress the swallowing reflex and decrease upper airway activity
Midazolam and its effects on tracheal intubation?
Does not prevent increased ICP, BP, and HR evoked by intubation
How does midazolam affect the cardiovascular system?
- Decrease in arterial BP
- No effect on CO
Which benzo crosses the placental with lowest levels to the fetus ?
Which benzo crosses the placental with levels higher in fetus than maternal?
Midazolam (Versed) fetal to maternal ratio is less than other benzos.
Diazepam (Valium) Higher levels in fetus than mom.
Midazolam dose, onset, peak and duration for sedation during regional anesthesia?
- Dose= 1.0 to 2.5 mg IV
- Onset= 30-60 secs
- Peak= 5.6 minutes
- Duration = 15 to 80 minutes
True/False. Increased age equals increased sensitivity to hypnotic effects of Midazolam?
True
What are the most common used treatments for valium?
- Oral preop out pt. procedures,
- Management of Delirium Tremens with alcohol withdrawal
- Treatment of local anesthetic induced seizures, skeletal muscle relaxation in lumbar disc disease or tetany
What are the 5 characteristics of Benzo’s?
- Anxiolysis
- Sedations/Hypnosis
- Anticonvulsant
- Skeletal muscle relaxation
- Anterograde amnesia (can NOT stimulate GABA by its self like barbs)
What are Benzos used to treat?
- Anxiety,
- Insomnia,
- Agitations,
- Seizure,
- Muscle spasms,
- ETOH withdrawal
- Pre-medicate for procedures
- NO analgesic properties give narcotic to treat pain
Which benzo is produces profound amnesia when combined with alcohol?
Triazolam
How does Midazolam effect respiratory system
- dose dependent central ventilatory depression 40% decrease in Vt
- RR min ventilation unchanged but alveolar ventilation decrease.
- Blunts hypoxic drive relaxes upper airway & gag reflex
Which benzo is least likely to be impacted by hepatic alterations & P450 inhibitors?
Lorazepam less likely than diazepam to be influenced by hepatic functions increase in age, & P450 inhibitors (cimetidine)
Which drug is conjugated with glucuronic acid in the liver to form inactive metabolites?
Lorazepam
diazepam & midazolam have pharmacologically active metabolites
What is only clinically used agent that induces a state of dissociativeanesthesia?
Ketamine- (Arylcycloalkylamine Phencyclidine derivative PCP) causes separation of thlamocorticalfrom limbic systems (catatonia)
Which drug is widely used in veterinary anesthesia?
Ketamine
How is Ketamine prepared ? (Racemic)
- Commercial preparation is a racemic mixture
- S isomer is more active- produces more analgesia, rapid meta, less salivation and lower incidence of emergence reaction
What is the MOA of Ketamine?
Mostly unknown but thought of as…
Noncompetitive antagonism Ketamine appears to exert its effect through blockade of the N-Methyl-D-aspartate receptor (NMDA) inhitbiting the excitatory neurotransmitter glutamae.
Also interacts with Opiods in Mu receptors antagonist Kappa Agonist
At lower dose what actions can Ketamine produce? (Think why would you go to a Ketamine clinic?)
Analgesia and Antidepressant (12-weeks)
In which patients should Ketamine be avoided ?
- Icreased ICP(can increase CBF by 60%)
- can activate epileptogenic foci in patients with seizure disorders
Bipolar/ schizophrenia
What drug is associated with Emergence delirium?
Ketamine can cause Emergence delirium ( Give with Versed/benzo for amnesia)
- can occur for up to 24 hours and are often morbid and bright in color.
- likely due to depression of the colliculus and medial geniculate nucleus.
- Occurs 5-30%
Respiratory effects of Ketamine?
Great Bronchodialator! Maintain airway & gag reflex. Promotes Salivation giveglycopyrrolate to combat
Where is the MOA for DEXMEDETOMIDINE ?
pontine locus ceruleusin (forebrain)
How are Barbiturates separated?
2 groups:
Oxybarbiturates only metabolized by hepatocytes (Oxy only fuks wid Hepatocytes) & retain O2on #2 carbon atom Methohexital, Phenobarbital, Pentobarbital (Lethal injection), Secobarbital(PPMS).
Thiobarbiturates undergo oxidative metabolism(Phase II) in Liver & extra hepatic sites (brain, kidney) it also Replace O2Atom with Sulfur on #2 carbon atom Thiopental (lethal Injection) Thiamylal (TT)
Which anesthetic gas increases the incidence of PONV?
N2O
Which receptors do barbiturates work on?
- GABAA
- Glutamate, Adenosine, and neuronal nicotinic acetylcholine receptors at clinically used concentrations
What are the 3 mechanisms of action on Barbs?
- Depression of reticular activating system
- Depression of acetylcholine release
- Enhancement of GABA (Can work without GABA present )
How do barbiturates interact with GABAA receptors?
- Binds allosterically to increase the affinity of GABA for binding site opening the chloride channel
- Or at higher doses barbs can mimic the action of GABA by directly activating GABA receptors
Describe the onset, awakening, uptake and distribution of thiopental.
Everything is rapid! Rapid onset and rapid awakening due to rapid uptake then rapid redistribution out of the brain into inactive tissues
Thiopental has a ____ hepatic extraction ratio.
low hepatic extraction ratio.
How is the elimination half-life of thiopental affected in pediatric and obese patients?
- Pediatric patients have a shorter elimination half time due to rapid hepatic clearance.
- Obese patients prolonged elimination half- life due to an increase in Vd.
Sedative and hypnotic properties of barbiturates are determined by alterations in the 2nd and 5th carbon atom. What are these carbon atoms replaced by?
- 2= Oxygen (pentobarbital, secobarbital)
- 5= A phenyl group (phenobarbital) increases anticonvulsant. In addition to an oxgen at the 2nd carbon atom
Why is methohexital more potent than thiopental?
At blood pH of 7.4 methohexital is 76% unionized compared with 61% for thiopental.
How does methohexital affect the seizure threshold?
It lowers the seizure threshold and induces seizures (useful in ECT). Seizures can be decreased with treatment of opioids.
This class of medication can be administered to decrease refractory ICP that remains increased despite other measures.
Barbiturates
-Decreased ICP results from a decrease in Cerebral Blood Flow via vasoconstriction.
Which drug has a shorter elimination ½ time Methohexital or Thiopental?
Methohexital Remember M before T alphabetically
When administering barbs in normovolemic pt’s what cardiovascular changes should you expect?
Mild transient decrease in BP peripheral vasodilation compensatory tachycardia
Why are barbiturates not recommended during cardiac surgery or after a stroke?
Moderate degrees of hypothermia (33 to 34) that occur naturally, provide superior neuroprotection without prolonging the recovery phase.
When administering thiopental to the elderly, by how much would you reduce the dose?
30-35%
The elimination ½ time of thiopental is prolonged in what conditions?
Obesity & pregnancy (increased Vd fatty tissue in the obese & Increase protein binding pregnancy)
What respiratory changes should you expect after delivering barbs?
Depresses medullary & pontonary Decreased RR & Tidal Volume blunts resp to hypercarbia/hypoxemia decrease RR drive even in COPD
True/False. Barbiturates blunt responses to CO2, hypoxemia, and apnea.
True
Which drug can be administered when the ability to monitor somatosensory evoked potentials is desirable?
Thiopental
Can barbs be used in pt’s with increased ICP?
It decreases CBF& pressure, can be used as tx. For icp resistant to other treatments ie. Hyperventilation
What is a direct contraindication to the use of barbs?
Acute Intermittent Porphyria (defects in heme metabolism conversion of porphobilinogen to hydroxymethlibilane)
clinically presents as abd pain, neuropathies, constipation NO RASH.
Are barbiturates enzyme inhibitors or inducers?
Inducers- can result in accelerated metabolism of oral anticoagulants, phenytoin and tricyclic antidepressants.
-Even endogenous substances like corticosteroids, bile salts, and vitamin K.
Is the inadvertent arterial injection of thiopental emergent?
Hell Yeah!! It results in immediate intense vasoconstriction and excruciating pain radiating along the artery.
Can lead to gangrene and loss of hand.
Treatment includes immediate attempts to dilute the drug, prevention of arterial spasm by injection vasodilators such as lidocaine or papaverine and measures to restore blood flow.
With a Pka of 7.6, in acidosis thiopental will favor its Ionized/unionized\_ form making the _drug **more/less** potent. In alkalosis it will favor its ionized/unionized making the drug more/less potent.
Acidosis: Unionized, More potent
Alkalosis: Ionized, Less potent
What Barb is the most potent liver enzyme inducer?
Phenobarbital increases hepatic enzyme 20-40% & promotes its own metabolism may persist up to 30days (after infusion 2-7 days)
True/False. Thiopental can produce signs of an allergic reaction in the absence of prior exposure suggesting an anaphylactoid response.
True. May be due to direct release of histamine from tissue mass cells. Although anaphylaxis can occur.
Allergic reaction occurrence is 1 per 30,000 patients.
What side effects should be expected after barbs administration?
40% report garlic/ onion taste in the mouth, low incidence of N/V,
When administering a highly soluble agent to patients with compromised cardiac output what should you do?
Use caution as it may predispose them to overdose
What of the only gas inhaled agent?
N2O, all others are liquid that must be vaporized into gas
The Uptake & distribution of volatile agents are determined by?
FD flow delivered, FI inspired gas concentration, FA alveolar gas concentration.
What are the 3 goals of inhaled anesthetic use?
- Achieve inhaled anesthetic concentration in the brain
- MOA promoting analgesia and amnesia
- Induced unconsciousness.
When using inhaled anesthetic agents on in pediatrics you should prepare to?
Used more gases as their rate of metabolism is quicker.
In which patients should Halothane be used in caution?
Impaired hepatic function such as cirrhosis or liver failure due to its hepatic metabolism.
What is the ideal agent for Asthmatics?
Sevo, produces bronchodilation & non-pungent produces LEAST degree of airway irritation of all inhaled agents
What is the MAC of Sevoflurane? What is it derived of?
1.8 Fluorinated Methyl isopropyl ether
How can lowering of alveolar partial pressures by uptake be countered?
Increasing alveolar ventilation or increasing Fa/Firatio for soluble agents
What is unique about the delivery of halothane?
Sensitizes the heart to dysrhythmogenic effects of drugs that induce catecholamines release ie EPI.
In which cases should N2O be avoided?
Eyes & ears(tympanoplasty) & all cases where gas volume can be expanded like pt.s with venous air embolism or closed pneumothorax
At what age are MAC concentrations the highest?
infants age 6 months 1.5-1.8x higher than 40 y.o. adult
What is the Mac of Isoflurane & what properties does it share with Enflurane?
1.17, Isomer of enflurane & also Halogenated methyl ethyl ether
Which additive is used in Halothane & why?
Thymol to stabilize it & prevents decomposition, build up can alter delivery % of drug
In which patients should Enflurane be used with caution
Epileptics (decreases seizure threshold) & renal impairment (Nephrotoxic effects from inorganic fluoride ions)
What is the purpose of the alveolus asymmetrical sides?
Thick side: provides structural support
Thin: <0.4 gas exchange.
What is the MAC of Halothane? what is it derived from?
0.75. Halogenated Alkane, known for its sweet non-pungent odor
When cardiac ouput is decreased in administering soluble agents what is the pt. at risk for?
Overdose with high soluble agents ( slower whisk away). Increase Cardiac output increase agent uptake.
How to prevent diffusion hypoxia after the administrtion of N2O?
Administer 100% O2 for 5-10mins after to wash out alveoli, transfer pt. to PACU with facemask
For insoluble agents, what effect does hyperventilation have?
Insoluble agents have minimal effects from hyperventilation (increases rate of rise pedi whisk away quick & replaced quickly) Produces rapid induction.
Hypoventilation prolongs induction
What is the factors that impact elimination of inhaled agents?
Exhalation ( most important)
Biotransformation Phase II minimal elimination
Transcutaneous loss (skin) insignificant
True/False. Increased age equals increased sensitivity to hypnotic effects of Midazolam?
True
Treatment for paradoxical vocal cord motion
Versed
Properties of diazepam.
- Insoluble in water. Highly lipid soluble
- Viscid solution, pH 6.6to 6.9
True/False. Dilution with water or saline causes cloudiness and alters the potency of the drug.
False. It does cause cloudiness but does not alter the potency of the drug.
The duration of action of benzodiazepines are not linked to receptor events but is determined by
Redistribution, then rate of metabolism, and elimination
Why isn’t hemodialysis effective in diazepam overdose?
A high degree of protein binding and wide distribution to extravascular tissues.
Two principal metabolites of diazepam
- Desmethyldiazepam (nordazepam)
- Oxazepam
How does diazepam compare to lorazepam in terms of elimination half- life and duration of action?
Longer elimination half time but shorter duration of action. This is related to the quick dissociation from GABA
True/False. Diazepam produces minimal effects on ventilation.
True. The effect is more of a CNS effect because mechanics of respiratory muscle are unchanged.
Diazepam has minimal effect on BP, CO, and SVR but what type of patient can it have a significant decrease in pressure when administered diazepam.
A patient with increased left ventricular end diastolic pressure.
How does nitrous oxide administered with diazepam differ from opioids.
The addition of nitrous oxide after diazepam is not associated with adverse cardiac changes. When nitrous oxide is administered in the presence of opioids, direct myocardial depression and decrease in BP occur.
What happens to skeletal muscle when diazepam is administered?
Skeletal muscle tone is decreased. Used for management of delirium tremors and tetany.
How does benzodiazepines prevent seizures in contrast to barbiturates?
- Benzodiazepines are selective for -1, -2, -5 subunits and increase the frequency of chloride channel opening.
- Barbiturates increase the duration of opening.
What type of seizures do diazepam stop?
- Seizures produced by lidocaine
- Delirium tremors
- Status Epilepticus
Which is the most potent sedative and amnestic, midazolam, diazepam or lorazepam?
Lorazepam. Potency rating of 5
True/False. The elimination half-time of lorazepam is prolonged in elderly patients or those treated with cimetidine?
- False. Formation of glucuronide metabolites of lorazepam is not entirely dependent on hepatic microsomal enzymes.
- However, obese patients have a longer elimination half time.
Why isn’t lorazepam used for IV induction of anesthesia, IV sedation during regional anesthesia, or as an anticonvulsant.
It has a slow onset (1-2 min) and ain’t nobody got time for that
How does oral and IM absorption of lorazepam compare with diazepam.
- Lorazepam undergoes reliable absorption after oral and IM injection.
- Diazepam only 50% reaches systemic circulation.
Recommended initial dose of IV flumazenil and the alternative to the intial dose?
The recommended initial dose is 0.2 mg IV. Typically reverses the CNS effects of benzodiazepine agonists within 2 minutes.
If required further doses of 0.1 mg IV (to a total of 1 mg IV) may be administered at 60-second intervals.
An alternative to repeated doses is continuous infusion of flumazenil 0.1 to 0.4 mg/hr
Total doses of ______ are usually sufficient to completely abolish the effect of a therapeutic dose of benzodiazepine.
0.5 to 1 mg
True/False. It is okay to give flumazenil to patients being treated with antiepileptic drugs for control of seizure activity.
False. It could precipitate acute withdrawal
