Basic Questions Flashcards
When should FFP be used for warfarin reversal?
- FFP may be used if surgery is urgent and INR is >1.5
- Vitamin K should be used for elective procedures (including procedures that can be delayed 24 hours)
What can happen if excessive anti-cholinesterase medication is given (i.e. neostigmine, edrophonium, etc)?
-It can cause a depolarizing blockade! (Similar to succinylcholine)
How long should patients wait after receiving drug-eluting stents vs. bare-metal stents before undergoing surgery?
- It depends. For elective cases: wait 30 days for bare-metal stents, and wait 365 days for DES.
- For drug-eluting stents, urgent cases can proceed after 180 days. (If pt. will experience bad outcome w/ surgical delay).
- A case should be delayed 14 days if pt. has had a recent balloon angioplasty
What can trigger laryngospasm?
- It can be triggered by pain, abdominal/visceral stimulation, vomitus, respiratory secretions/blood, foreign body in the airway
- It is more common in pediatric pts.
- It is especially high in kids w/ GERD or URI’s within the preceding 4-6 weeks!
What is the difference between a case-control study and a cohort study?
- In a cohort study, 2 groups of subjects are separated before the intervention is given (i.e. vitamin C to reduce viral illness)
- In a case control study, the subjects are separated AFTER the intervention has been given (i.e. pts. that already either had vitamin C or had not)
Carbon monoxide cause tissue hypoxia/acidosis by what 3 mechanisms?
- Decreased coupling of oxidative phosphorylation/decreased ATP production
- Increased lactate production
- Leftward shift of oxygen-hemoglobin dissociation curve
What 3 things increase MAC?
- Hyperthermia/hypernatremia
- Chronic ethanol abuse
- Increased central neurotransmitter levels (MAOI’s, amphetamines, cocaine, ephedrine, levodopa)
Maximum allowable doses for local anesthetics?
Bupivicaine (plain) 2.5 mg/kg Bupivicaine (w/ epi), Ropivicaine (plain) 3 mg/kg Lidocaine (plain) 5 mg/kg Lidocaine (w/ epi) 7 mg/kg Chloroprocaine (plain) 12 mg/kg
What are presenting signs of sodium nitroprusside toxicity?
- Flushing
- Elevated mixed venous oxygen
- Metabolic acidosis
- Tachyphylaxis to SNP
- Due to toxicity from SNP’s metabolic byproducts: cyanide and thiocyanate
- Treatment is amyl nitrate (coverts Hb to MetHb which binds cyanide)
What 3 metabolic abnormalities occur w/ respiratory alkalosis?
- Hypocalcemia
- Hypokalemia
- Hypophosphatemia
Which patients are most at risk when performing neuraxial anesthesia?
Pts. w/ space-occupying extradural lesions or those that reduce the cross-sectional area of the spinal cord (i.e. spinal stenosis).
-They are most at risk for new or worsening neurologic injury
What are acid-base abnormalities in alcoholics?
- HYPOkalemia/hypomagnesemia/hyponatremia
- HYPERuricemia
- Metabolic acidosis
- Respiratory alkalosis
What happens w/ decreasing/increasing temperatures and gas solubility in blood?
- As temperature decreases, gases become more soluble in blood. This means the partial pressure of the gas will DECREASE!!
- The opposite will happen w/ increases in temperature.
- *Blood pH will increase w/ decreasing temperatures**
What order does blockade occur in after local anesthetic administration? What are the levels of pain/sympathetic/motor blockade?
- First to last: B fibers, A fibers, then C fibers (BAC). Recovery is in reverse order (CAB)
- ‘Sympathetic People Matter’ (sympathetics are 2-4 levels higher than motor block, pain blockade levels are 2-3 levels higher than motor)
What receptors does dopamine act on at low/moderate/high doses?
- Low: D1 dopamine receptors (vasodilation of coronary/renal/mesenteric vasculature)
- Moderate: Beta-1 receptors
- High: Alpha-1 receptors
What are the percentages of data for 1, 2, and 3 standard deviations from the mean (assuming a normal distribution)?
-Plus/minus 1 standard deviation: 68%
“ “ 2 standard deviations: 95%
“ “ 3 standard deviations: 99%
What kind of metabolism does lorazepam undergo?
- Phase 2 reaction (in the liver). It undergoes glucuronidation
- *Midazolam and diazepam undergo Phase I reaction (oxidation/reduction)
How does an intrathoracid/extrathoracid lesion affect inspiration/exhalation?
- A variable extrathoracic lesion causes impairment during INHALATION
- A variable intrathoracic lesion causes impairment during EXHALATION
- A fixed upper airway obstruction or large airway obstruction causes impairment of both inspiratory and expiratory phases (Foreign body, tracheal stenosis, etc.)
What 2 agents are unaffected by pseudocholinesterase deficiency? What agents are metabolized by pseudocholinesterase?
- Remifentanyl and esmolol are metabolized by non-specific blood and tissue esterases and are not affected by pseudocholinesterase deficiency
- Succinylcholine, mivacurium, ester local anesthetics, cocaine and heroin are metabolized by pseudocholinesterase
What are the 3 mechanisms of nitroprusside toxicity?
- Cyanide ions bind to cytochrome-C oxidase and inhibit cellular aerobic respiration
- Formation of cyanmethemoglobin (which cannot carry oxygen)
- Thiocyanate production (which causes CNS-related effects)
What is the preferred therapy for urgent reversal of warfarin therapy?
Prothrombin complex concentrate (PCC) along with vitamin K administration
What are the 3 phases of coagulation?
- Primary hemostasis (platelets form a clot to plug vascular injury)
- Coagulation (fibrin forms mesh over the clot to stabilize it)
- Fibrinolysis (after the injury is repaired, the clot is broken down)
How is the time constant calculated?
It is the volume or capacity of the circuit (Vc) divided by the fresh gas flow (FGF). Vc/FGF
How long does it take after an episode of acute hypotension/hypovolemia for angiotensin-II-mediated vasoconstriction to occur?
Within 20 minutes after the onset of hypotension/hypovolemia
When should perioperative stress-dose steroids be given?
- They should be given to patients who take >10 mg prednisone per day, or patients who had previously been taking that dose less than 3 months before surgery. (If the last dose was >3 months before surgery, they do NOT need supplementation)
- *Patients taking high-dose steroids for immunosuppression do NOT need perioperative supplementation**
What are the 3 most important factors which determine level of spinal blockade?
- Drug dosage
- Drug baricity
- Patient positioning
Meperidine is similar to what molecule?
Atropine. Increased heart rate may occur as a side effect of meperidine administration
What 4 things cause (gas) laminar flow to become turbulent?
- High gas flow rates
- Sharp angles/branch points within a tube
- Increase in diameter of a tube
- Decreasing viscosity of a gas
How long should patients wait for elective surgery after having an MI/bare-metal stent/drug-eluting stent?
- After MI: wait 14 days (after balloon angioplasty)
- After BMS: wait 30 days
- After MI (w/o coronary intervention): wait 60 days
- After DES wait 360 days
Where does cardiac sympathetic innervation originate from?
T1-T4.
-It is associated w/ alpha-1, beta-1, and beta-2 adrenergic receptors
What is the difference between an acute and delayed hemolytic transfusion reaction?
- Acute reactions are almost always due to ABO incompatibility
- Delayed reactions are usually secondary to antibodies associated w/ Rh, Kidd, or Kell systems.
- Both are the result of RECIPIENT antibody and complement attack on donor cells.
*Delayed reactions can take up to 21 days!**
What are the 2 types of starches? Which is associated w/ lower risk of coagulopathies?
- Hetastarches and tetrastarches
- Tetrastarches are newer and lower molecular weight. They are associated w/ lower risk of coagulopathy.
Anti-arrhythmic of choice in CHF/low ejection fraction? Side effects?
Amiodarone
-Bradycardia, hypotension, hypothyroidism/hyperthyroid storm, pulmonary toxicity, prolonged QT, elevated LFTs, tissue deposits (blue-grey appearance)
What steps should be taken for a patient that has aspirated gastric contents w/ an LMA?
- Increase FiO2 to 100%
- Deepen anesthesia
- Place patient in head-down position
-Suctioning should be performed and severity of aspiration assessed using fiberoptic bronchoscopy
What 3 receptors does nitrous oxide act on?
‘AND’
- Alpha-adrenergic receptors (analgesia and sympathomimetic effects)
- NMDA (analgesia and CNS-depression)
- Dopamine (analgesia via downstream induction of opioid release)
St. John’s Wort drug interactions?
It is an herbal anti-depressant that induces the CYP enzymes, which can over-metabolize lidocaine, alfentanil, midazolam, cyclosporine, and warfarin.
-It should be stopped at least 5 days prior to any surgical operation
What are the 3 main determinants of myocardial oxygen demand?
- Wall tension
- Heart rate
- Contractility
What is the treatment for citrate toxicity?
Calcium
What are the goals for patients w/ aortic stenosis/regurgitation?
- Aortic Stenosis: Normal sinus rhythm should be maintained; a normal to slower HR is good to allow for ventricular filling. Maintain contractility, maintain adequate preload. Afterload must be maintained distal to stenotic lesion to ensure coronary perfusion
- Aortic Regurgitation: HR must be kept above 80 to prevent increased time for regurg. Maintain contractility. Need adequate preload to move enough volume forward, but do not overload-this will increase regurgitant volume. Lower afterload-this should prevent more regurgitation.
What are the values for mild/moderate/severe ARDS?
Mild: PaO2/FiO2 ratio of 200-300
Moderate: 100-200
Severe: <100
What is the role of the carotid body and carotid sinus?
-Carotid body: chemoreceptor
-Carotid sinus: baroreceptor (think ‘Sinus Pressure’)
(The carotid sinus causes increased parasympathetic discharge)
What is seen in primary hyperthyroidism?
Elevated T3/T4 (free and total), elevated thyroid hormone binding ratio, and a low or normal TSH
A full tank of N2O is how many liters/psi?
-1590 L
-745 psig
(Pressure will remain at 745 psi until all liquified gas is used up)
What are the top 3 causes of death associated w/ blood product transfusions?
- TRALI
- Hemolytic transfusion reactions (non-ABO> ABO)
- Infection/transfusion-associated sepsis
Acute hypoxemia immediately following trendelenburg position is most likely due to what?
- Endobronchial intubation
- A shift of the diaphragm upward will result in a cephalad shift of the tracheobronchial tree- this may cause an ET tube to move further into the trachea and into the right main stem bronchus
What are the effects of dexmedetomidine?
- It provides sedation/anxiolysis/hypnosis/analgesia/sympatholysis
- It decreases HR, SVR, CO, and BP
- It also decreases incidence of perioperative myocardial ischemia and reduces perioperative opioid requirements
What structures are HYPOechoic?
- Structures such as blood (which have a high water content) reflect little of an ultrasound’s beam
- Structures w/ low water content (bone and tendon) reflect more of an ultrasound’s beam and appear hyper echoic.
- *Air reflects a significant amount of the beam back**
What is the order of least-to-most soluble volatile anesthetic?
Desflurane, Nitrous Oxide, Sevoflurane, Isoflurane, Halothane
Pseudocholinesterase deficiency affects what 2 drugs?
- Succinylcholine and mivacurium. Deficiency prolongs the actions of both paralytics.
- Echothiophate also inhibits pseudocholinesterase- it can cause up to a 95% decrease in pseudocholinesterase function
How is the standard error (standard error of the mean) calculated?
SE= standard deviation/square root of ‘N’ (sample size)
What is the order of non-depolarizing muscle relaxant potentiation by volatile anesthetics?
Des>Sevo>Iso>Halothane>TIVA
-This is b/c desflurane is less potent, therefore, more of the drug is within the blood compared to sevo and iso
Laminar/Turbulent flow is affected by what gas factor?
- Laminar flow is primarily affected by gas viscosity (Poiseuille)
- Turbulent flow is primarily affected by gas density (Graham’s law)
What is a type I and type II error?
Type I: incorrectly accepting the alternate hypothesis
Type II: incorrectly accepting the null hypothesis
Heat transfer from the patient to the environment occurs through what 4 mechanisms?
- Radiation: surfaces the pt. is in contact with will absorb radiated heat
- Convection: thin layer of air next to skin acts as an insulator- OR air is exchanged and disrupts this layer
- Conduction: transmission of body heat through conducting medium
- Evaporation: sterile prep solutions are applied and liquid changes into vapor, resulting in decreased temp.
* *Radiation and convection are the 2 biggest contributors to heat loss**
Which volatile agent undergoes the most extensive metabolism?
Sevoflurane (5-8%)
From most to least: sevo, iso, des
What is the stimulus for the carotid body chemoreceptors?
They are primarily responsive to reductions in arterial partial pressure of oxygen (PaO2)
-They increase minute ventilation in response to decreases in PaO2 below 60-65 mm Hg
What are the 4 depths of anesthesia?
- Minimal Sedation: normal response to verbal stimulation
- Moderate: purposeful response to verbal/tactile stimulation
- Deep: purposeful response to repeated or painful stimulation. Spontaneous ventilation may be inadequate and airway intervention may be required
- General Anesthesia: unable to arouse even w/ painful stimulus. Spontaneous ventilation is frequently inadequate- airway intervention is often required. Cardiovascular function may be impaired.
What are the current recommendations for preoperative ACE inhibitor use and treatment for refractory hypotension?
- Current evidence states to continue ACE inhibitors on the day of surgery
- Refractory hypotension should be treated w/ NE
What functions are lost in anterior spinal artery syndrome?
Loss of: motor, temperature, and pain
-Proprioception and vibratory senses are preserved