Pharmacology Flashcards
All ester LA are metabolized by ______
hydrolysis by pseudocholinesterase
*just like succinylcholine
Succinylcholine is metabolized by _____
pseudocholinesterase
What drugs are metabolized by pseudocholinesterase?
- Succinylcholine
- ester LA
- Cocaine
- Heroin
*A pseudocholinesterase deficiency will prolong the effects of the drug
What promotes more bradycardia, high dose or repeated doses of succinylcholine?
Repeat dosing
*dose > 6mg/kg produces a phase 2 block
Prolonged immobilization (after ~16 days) results in upregulation of immature AChRs. - Response to succinylcholine?
Hyper sensitivity
- Succ is easily able to interact with these receptors
- Substantial efflux of K (lethal)
Do anticholinergic toxicity present with diaphoresis?
No the cause of hyperthermia is lack of perspiration
- Thyroid storm also presents with hyperthermia, but will be diaphoretic
Most anesthetic drugs are cleared by the (kidney / liver)
liver transformation
Best depth for TEE probe?
T5-T6 mid thoracic spine
- 30-35 cm
Enoxaparin is a LMWH that binds and potentiates ______ , which will prolong (PTT / PT)
antithrombin to irreversibly inactivate factor Xa.
PTT
Unfractionated heparin binds and potentiates _____
antithrombin III, which in turn inhibits factor II (thrombin) and Factor Xa
Dabigatran is a ______, that leads to increases in (PT / PTT)
Direct thrombin inhibitor
both PT and PTT
*No therapeutic monitoring in place
Rivaroxaban is a ______, that leads to increase in (PT / PTT)
direct factor Xa inhibitor
Both PT and PTT
*monitor using anti-Xa levels
(True / False) Acute herpes zoster treatment, acyclovir, prevents future herpes recurrence
False
- its only effective as a prophylaxis if CHRONIC treatment, not acute.
Droperidol is contraindicated in any pt with ______
prolonged QT
The half-life of aminoamide LA is prolonged in (ESRD / End stage liver disease)
Liver disease
- hepatic enzyme dysfunction
- or immature enzymes in neonates
Why is bupivacaine not used for IV regional anesthesia?
High risk of LA toxicity and death
Absolute contraindication to propofol
Hypersensitivity to egg lecithin/phosphatide (yolk), soy products
*most people are allergic to egg white (egg albumin)
Can neuraxial opioids lead to tolerance, requiring a dosage escalation to obtain same response?
Yes
Why do infusion rates of remifentanil need to be cut in 1/3 in elderly pts?
Why do bolus doses of opioids need to be halved?
Decreased central clearance
- inc opioid effectiveness
Decreased central volume of distribution
The maximum dose of lidocaine with and without epi is ____.
Epi [ ] in a LA should not exceed:
Without: 5mg/kg
With: 7mg/kg
1:200,000
A phase II block is a result of _______with ongoing cellular sodium and potassium shifts ultimately rendering the receptor unresponsive to further binding by ACh
Hyperactivation of ACh receptors
Volatile anesthetics cause muscle relaxation through ______
inhibition of ACh receptor sensitivity and hyperpolarization of motor neurons
Citrate intoxication can occur with blood transfusion and may present as a metabolic (acidosis/alkalosis)
alkalosis
NNT for:
Dexamethasone:
Ondansetron:
Droperidol:
Dexamethasone: 4
Ondansetron: 3
Droperidol: 5
GABA is an (Excitatory/Inhibitory) neurotransmitter that controls the state of chloride ion channels.
- How does this contribute to muscle relaxing properties?
Inhibitory
- Activation of Cl- channels -> neuronal hyperpolarization -> decreases ability for membrane potential to occur
*BDZ facilitate GABA receptors (inhibitory) in the CNS (CENTRAL)
Midazolam bioavailability by route of administration from greatest to least
IV SubQ IM Sublingual Intranasal Rectal (20-50%) Oral
Concurrent use of antacids or grapefruit can (increase/decrease) the onset time and bioavailability of midazolam
Increase
by inhibiting the Cyt P450 enzyme system
_____ has the lowest cardiac-to-CNS dose toxicity ratio (2:1)
*ratio of dose causing cardiac collapse to dose causing seizures/convulsions
Bupivacaine
- and the HIGHEST relative potency for cardiac toxicity
- d/t stronger affinity for both resting and inactivated sodium channels w/in myocardium
*Ropivacaine has same cardiac-to-CNS dose toxicity ratio (2:1), but less cardiac toxicity
Do you need to monitor anti-factor Xa levels to predict safe neuraxial placement?
no
- not predictive of bleeding risk unless elderly pt with renal insufficiency receiving therapeutic doses of LMWH
Which one affects PTT more, LMWH or unfractionated heparin?
Unfractionated heparin
*do not need to routinely monitor PTT in pts on LMWH, it is highly predictable
(LMWH / Unfractionated heparin) prolongs PTT to a larger extent
Unfract. Hep.
What is the dosing for lipid emulsion (20%) in pts with LAST?
bolus 1.5ml/kg over 1 min
infusion 0.25 ml/kg/mi
What is the preferred treatment of arrhythmias in pts with LAST?
amiodarone
How is the dose of epi changed in ACLS if LAST is suspected?
dose < 1 mcg/kg per dose
- epi is arrhythmogenic in itself and make LAST more pronounced
The maximum allowable dose of lidocaine:
- without epi
- with epi
- without epi: 5mg/kg
- with epi: 7mg/kg
over 60 min
1% lidocaine = 10mg/mL
2% lidocaine = 20mg/mL
The maximum allowable dose of bupivacaine:
- without epi
- with epi
- without epi: 2.5mg/kg
- with epi: 3mg/kg
over 120min
What is the maximum allowable dose of 2% lidocaine (20mg/mL) with epi in a 70kg pt?
7mg/kg * 70kg = 490mg
490mg / (20mg/mL) = 24.5 mL
When the pH of the soln is LESS than the pKa, the molecule will be (ionized/unionized) at physiologic pH
ionized
When the pH of the soln is EQUAL to the pKa, the molecule will be (ionized/unionized)
both
50% ionized
50% unionized
What happens when bicarbonate is added to local anesthetics? downside?
increases the non-ionized form of lidocaine
- increases speed of onset
- can form precipitation
- unionized drugs are much less soluble than ionized drugs
Allergic reaction with ester type local anesthetics (procaine, benzocaine, tetracaine) most often is d/t ______
hypersensitivity to para-aminobenzoic acid (PABA)
metabolite of ester LA
Metformin MOA
Decrease hepatic gluconeogenesis and increase insulin sensitivity
Metformin is excreted by the ____.
Common adverse effect to monitor for?
kidneys
- if kidney disease, it can build up / have poor elimination -> lactic acidosis
Usually metformin is continued thru the periop period. When would you make an exception and d/c the metformin?
If pt has renal dysfunction
- d/c metformin 24-48hrs prior to surgery
Why is methylene blue (1mg/kg) used for methemoglobinemia?
methylene blue is an antioxidant for the reduction of methemoglobin using NADPH produced from the hexose phosphate pathway
What is the tx choice for methemoglobinemia in pts with G6PD deficiency?
Ascorbic acid (vitamin C) - an antioxidant (electron donor), is able to reduce Fe3+ to Fe2+
*avoid methylene blue bc the hexose phosphate pathway is dysfunctional and free radicals can develop -> RBC lysis
Which meds can cause a transient decrease in SpO2 lasting anywhere form 30 seconds - 20 min?
- Methylene blue
- Indocyanine green
- Indigo carmine
*absorbance is lower at 630 nm, which correlates to SpO2 of 84-86% in pulse ox
Meds known to induce methemoglobinemia (7)
- Prilocaine
- Nitroglycerine
- Sodium nitroprusside
- Phenytoin
- Sulfonamides
- Metoclopramide
- Benzocaine
Clinical sx of acetaminophen overdose
Nonspecific
- N/V
- Malaise
- abdominal pain
Why is N-acetylcysteine (NAC) used for acetaminophen overdose?
NAC provides cysteine for replenishment and maintenance of hepatic glutathione stores ->
enhances elimination pathway
Exogenous corticosteroids stimulate the negative feedback loop and suppress both _______
Corticotropin releasing hormones (CRH) and arginine vasopressin (AVP) production
V1 receptors
vs
V2 receptors
Where are they located?
What happens if receptors are activated?
V1:
- located in vascular smooth muscle
- ca2+ release and vasoconstriction
V2:
- located in- the distal renal tubules and collecting ducts
- increase water reabsorption in states of hyperosmolarity or hypovolemia
How do loop diuretics cause a constriction alkalosis?
Loop diuretics inhibit the Na/K/2Cl channel in the LOH
- Increase urine output
- Urine is high sodium, low bicarbonate containing fluid
What metabolic derangements are associated w/ aspirin overdose?
Initially: respiratory alkalosis
Eventually: metabolic acidosis
Which organs are at increased risk of injury from propofol infusion syndrome (PRIS)?
- Cardiac muscle
- HF - Skeletal muscle
- Rhabdo - Liver
- Pancreas
Why do some pts have green urine with propofol infusion syndrome (PRIS)?
Phenol excretion
Why is methadone a good choice for pts with chronic neuropathic pain?
It is an opioid analgesic with concurrent NMDA antagonistic properties
Also provides serotonin reuptake
How does nitrous oxide affect pts with B12 deficiency?
What symptoms can get exacerbated?
Reacts with and inactivates B12 -> worsening B12 deficiency
Megalobastic anemia
Myelopathy
Neuropathy
Encephalopathy
Name the toxic inhalational reaction:
Nitrous oxide:
Methoxyflurane:
Halothane:
Nitrous oxide: B12 deficiency
Methoxyflurane: polyuric renal insufficiency
Halothane: subclinical or fulminant hepatotoxicity
Max dose of bupivacaine
With and without epi
Without epi: 2.5 mg/kg
With epi: 2.5 mg/kg
Max dose of chloroprocaine
With and without epi
Without epi: 11 mg/kg
With epi: 14 mg/kg
1% drug = __mg/mL
2% drug = ___ mg/mL
10mg/mL
20mg/mL