ITE Questions Flashcards
What are the 7 conditions approved for hyperbaric oxygen therapy treatment?
- Gas-bubble disease (air embolism/decompression sickness)
- Carbon monoxide poisoning
- Infections (soft tissue necrotizing infections)
- Acute/Chronic tissue ischemia
- Acute hypoxia (blood-loss anemia when transfusion unable to be given)
- Acute thermal burn injury
- Idiopathic sudden sensorineural hearing loss
What are transient neurological symptoms (TNS)? What are the risk factors for the development of TNS (4)?
- Characterized by pain in the butt or legs following spinal anesthesia (usually sef-limiting to 72 hours)
1. Lithotomy position
2. Lidocaine use
3. Addition of phenylephrine to 0.5% tetracaine
4. Pts. who undergo outpatient procedures
How much does oxygen consumption increase during the 1st and 2nd stage of labor?
- Oxygen demand increases by 40% in the 1st stage, and 75% in the 2nd stage
- These demands can be reduced w/ analgesics, especially neuraxial anesthesia
Neurological monitoring (BIS or Entropy) does not correspond to which 3 anesthetic agents?
- Nitrous oxide
- Ketamine (N2O and ketamine can induce anesthesia w/ a high BIS/Entropy value)
- Dexmedetomidine (can produce a low BIS/Entropy value w/o inducing general anesthesia)
What is the treatment for organophosphate poisoning? What can be taken for prophylaxis?
- Atropine (to reduce muscarinic-mediated side effects), pralidoxime chloride (removes organophosphate compound from acetylcholinesterase), decontamination, and supportive therapy if necessary
- Pyridostigmine is effective for prophylaxis, if taken greater than 30 minutes before exposure
What 3 diagnostic tests can help differentiate ATN from acute kidney injury?
- Urinalysis
- Fractional excretion of sodium (FENa)
- Response to fluid challenge
In what age group is emergence delirium most common? What medications can decrease incidence of ED?
- It is most common in children between the ages of 2-5 who undergo a painful procedure under general inhalational anesthesia
- Prophylactic administration of clonidine, dexmedetomidine, fentanyl, ketamine, nalbuphine, or propofol can decrease incidence
What are the 3 diseases that are closely associated w/ malignant hyperthermia? What is the earliest sign of MH? Treatment?
- Central Core Disease
- Multi-Minicore Disease
- King-Denborough Syndrome
-The earliest sign of MH is a rapid rise of end-tidal CO2. Treatment is 2.5 mg/kg of dantrolene
What are the 2 most common risks of using TPN?
-Infection is the most common risk, and thrombophlebitis is the next most common risk, esp. w/ peripherally-delivered TPN
What are values for extracellular/intracellular body weight percentages in neonates? When to the compartments reach adult levels?
- Neonates have an extracellular compartment of 40% and intracellular compartment of 20% of their body weight. The compartments reach adult levels at 1 year of age (Adult levels are reversed: Extra: 20%, Intra: 40%)
- Preterm infants have a higher total body water compared to term infants
What factors decrease FRC? When does the greatest decrease occur?
- It is reduced by obesity, in females (10% less than males), and when moving from upright to supine/prone/Trendelenburg position
- FRC is highest when in an upright position. The greatest decrease occurs when going from 60 degrees to totally supine at 0 degrees. Beyond Trendelenburg of -30 degrees, the drop in FRC is considerable
What is the treatment of choice for pts. w/ Von Willebrands Disease?
- Desmopressin (DDAVP) is the treatment of choice for surgical bleeding in pts. w/ type-1 vWD
- Factor 8-vWF concentrate is useful in pts. w/ type 1 vWD who fail to respond to desmopressin, are undergoing major surgery, or in the setting of severe bleeding
In pts. w/ glaucoma, what medications should be avoided?
- Medications that cause mydriasis (anti-cholinergics and anti-histamines)
- Corticosteroids should be used cautiously in pts. w/ glaucoma
- Atropine and glycopyrrolate are considered safe to use in pts. w/ open or closed-angle glaucoma
What echocardiographic study provides a measure of right ventricular systolic function? What other studies (2) can provide this information?
- The tricuspid annular plane systolic excursion (TAPSE) can be used w/ TTE or TEE. A normal TAPSE is between 1.5-2 cm
- Cardiac MRI or MUGA scans can be used to calculate right ventricular EF also
What are considerations when using carboprost, methylergonovine, misoprostol, and oxytocin?
- Carboprost: venoconstriction, bronchospasm
- Methylergonovine: (alpha-receptor stimulation) alpha-mediated hypertension. Should not be used in pre-eclamptic pts.
- Misoprostol: uterine rupture is possible when used in pts. w/ history of c-section
- Oxytocin: vasodilation/hypotension. Can cause ADH-responses in large doses (water retention, hyponatremia)
What nerve root is affected by a far lateral/paracentral disc herniation?
- A far lateral herniation will affect the exiting nerve root at the level of the disc herniation
- A paracentral herniation will affect the nerve root at the level BELOW the disc herniation
Which cranial nerves have parasympathetic components? Where are they located?
- Cranial nerves 3, 7, 9, and 10 have parasympathetic components
- The component for cranial nerve 3 lies in the midbrain. The others lie within the medulla
What is the most common cause of pregnancy-related maternal mortality in the U.S.?
Maternal cardiovascular conditions (cardiomyopathy, congenital heart disease, CHF, hypertensive/ischemic/valvular disease)
What lung-related parameters are similar between neonates and adults?
- Tidal volume is comparable to an adult on a volume/kg basis
- Closing volume, respiratory rate, and minute ventilation are increased in neonates
What is 1st-line therapy for organophosphate poisoning/nerve agent exposure?
Atropine. It will antagonize muscarinic receptors causing a decrease in secretions and bronchospasm, and an increase in heart rate which will improve hemodynamics
What is the leading cause of perioperative mortality in morbidly obese pts.?
Deep vein thrombosis leading to PE
What kind of response can an IgA-deficient pt. have from a blood transfusion?
They are at risk for an anaphylactic response to IgA antibodies in donor blood. To avoid this reaction, these pts. should receive washed RBCs or blood from IgA-deficient donors
When should epinephrine be given in non-shockable rhythms during cardiac arrest?
As soon as possible
This does not apply for shockable rhythms
How does somatostatin affect other hormones?
It is an inhibitory hormone that suppresses the release of insulin, glucagon, growth hormone, and TSH
What electrolyte changes occur w/ loop diuretics?
- HYPOnatremia/kalemia/magnesemia
- HYPERuricemia
What are goals of management in a pt. w/ hypertrophic obstructive cardiomyopathy (HOCM)?
- The goal is to keep the left ventricle full!
- Increased preload, increased afterload, depressed myocardial contractility, normal to low heart rate, and maintain sinus rhythm
Should SSRI’s, SNRI’s, and MAOI’s be continued perioperatively? What medications can induce a hyper-pyretic response in these pts.?
- SSRI’s and SNRI’s should be continued on the day of surgery. MAOI’s should be held on the day of surgery.
- Many opioids have been implicated in causing a hyper-pyretic response (esp. meperidine), morphine and hydromorphone have also been linked.
- *Fentanyl is safe to use**
What are the 2 most common causes of postoperative jaundice?
- Hemolysis and breakdown of extravasated blood or hematoma
- It is helpful to categorize postoperative jaundice into pre/intra/post-hepatic categories
What factors cause FRC to increase/decrease?
- FRC is Increased: w/ age due to loss of elastic lung tissue, in COPD
- FRC is Decreased: in obesity, fibrosis (restrictive lung disease), pregnancy
What drug interactions can occur in pts. taking SSRI’s? What are signs/symptoms of serotonin syndrome?
- They may cause serotonin syndrome when used w/ other drugs that increase serotonin levels (ondansetron, metoclopramide, meperidine, etc)
- They inhibit cytochrome P450 enzymes (CYP2D6- converts codeine, oxycodone, tramadol)
-Altered mental status, autonomic hyperactivity (flushing, sweating, tachycardia, hyperthermia), tremor, muscle rigidity
What physiologic changes (4) occur in morbidly obese pts.?
Increase in:
- Fat mass
- Lean body weight
- Extracellular fluid volume
- Cardiac output
*Give benzodiazepines/opioids w/ extreme caution!!**
How do vasodilating agents affect cerebral vasculature?
- Most vasodilating agents will also cause cerebral vasodilation- this may result in flushing and a headache.
- Cerebral perfusion pressure is the difference between mean arterial pressure minus the central venous pressure or ICP (whichever is higher)
What can potentiate digitalis toxicity?
- HYPOkalemia/hypomagnesemia
- HYPERcalcemia
-Hyperkalemia can be a sign of acute digitalis toxicity
How does digitalis work?
-It inhibits the Na/K-ATPase which creates an increase in intracellular calcium, increasing myocardial contractility
What is a normal A-a gradient? What does a value >15 indicate? What is the formula for PAO2?
- A normal A-a gradient is 5-15 mm Hg. A normal gradient indicates that the problem is outside of the lungs (gas exchange across the alveoli into the capillaries is not affected)
- A difference >15 indicates there is a problem w/ gas exchange, suggesting lung pathology.
Formula: PAO2= 150 - (PaCO2/0.8)
What lung volume remains unchanged in the elderly?
Total lung capacity remains the same
What are the 2 components of plasma?
- Total blood volume is composed of an intracellular part (blood cells) and an extracellular part
- The extracellular part (plasma) has 2 components: plasma and subglycocalyx compartments
- The glycocalyx layer acts as a semipermeable membrane that keeps intravascular proteins from moving to the interstitial fluid
What will happen if a vaporizer is mistakenly filled w/ the wrong volatile anesthetic that has a higher saturated vapor pressure?
-The volume percentage of volatile anesthetic will be HIGHER than the concentration set on the dial
(DHIES)
- Des (669)
- Halothane (243)
- Iso (238)
- Enflurane (172)
- Sevo (157)
If a pt. aspirates while supine, where will the fluid go (most likely)?
The posterior segment of the right lower lobe
What cardiovascular changes (4) occur in the elderly?
- Decreased left ventricular compliance
- Decreased vascular compliance
- Decreased inotropy
- Decreased sensitivity of beta-adrenergic receptors
What are 5 physiologic considerations in the neonatal/pediatric patient?
- Neonates have reduced GFR/immature nephrons predisposing to sodium loss
- Higher metabolic requirements predisposing to hypoglycemia
- Large evaporative losses due to large relative body surface area
- Larger total body water percentage
- Immature sympathetic nervous system w/ a non-compliant myocardium
Electrolyte findings in pyloric stenosis?
HYPOnatremic/kalemic/chloremic metabolic alkalosis
How do opioids reduce pain signal transmission?
-They activate G-protein coupled opioid receptors at both pre- and post-synaptic sites in the dorsal horn of the spinal cord
What malformation is commonly seen in pts. w/ meningomyelocele?
Chiari II malformation (herniation of the cerebellar vermis through the foramen magnum)
What is the strongest single predictor for risk of complications/mortality following lung resection?
Predicted post-operative carbon monoxide diffusing capacity < 40% (DLCO <40%)
How is etomidate metabolized/excreted? Does it have low or high protein-binding?
- It is primarily metabolized by hepatic ester hydrolysis to inactive metabolites. It is then excreted by the kidneys (85%) and in bile (13%)
- Etomidate is HIGHLY protein-bound (dose can be reduced in pts. w/ disease processes that decrease plasma protein concentration)
What is the formula for oxygen delivery?
DO2= CO x CaO2 x 10
CaO2= arterial O2 content
What is the advantage of regional anesthesia for orthopedic/urologic procedures?
Neuraxial anesthesia can reduce the incidence of DVT (assoc. w/ TURP, total hip/knee replacements) compared to general anesthesia
Exam findings of compartment syndrome? When is an emergent fasciotomy indicated?
- Pain out of proportion to injury, persistent deep aching pain, pain w/ passive stretching of affected compartment
- A compartment pressure over 40 mm Hg is an indication for emergent fasciotomy
How does propofol cause hypotension?
It decreases preload/afterload and cardiac function. It also impairs the baroreceptor reflex
What are independent risk factors (5) for difficult mask ventilation?
- Presence of beard/facial hair
- BMI >26
- Lack of teeth
- Age > 55
- History of snoring
What nerve is spared w/ brachial plexus blockade (interscalene/supra/infraclavicular)? What areas does it innervate?
The intercostobrachial nerve (ICB). It provides innervation to the skin of the axilla and medial aspect of the proximal arm
How do volatile anesthetics affect cerebral autoregulation?
They attenuate autoregulation. At high doses, autoregulation is abolished and cerebral perfusion becomes pressure-passive
How much rocuronium is renally excreted?
- Up to 30%
- Metabolism of rocuronium does not produce active metabolites (unlike vecuronium and pancuronium)
How do pts. w/ severe anemia compensate?
Cardiovascular compensation for pts. w/ chronic and severe anemia is primarily mediated through an increase in cardiac output secondary to decreased blood viscosity
The concentration of what molecules can increase after dialysis?
Large molecules such as proteins are unable to pass through the HD semi-permeable membranes. Serum proteins usually increase following HD due to a concentrating effect
What electrolyte abnormalities can make digoxin toxicity more likely?
- Toxicity is more likely to occur in the setting of hypokalemia (digoxin competes w/ K for the same binding site on Na/K ATPase)
- Digoxin use in pts. w/ hypomagnesemia or HYPERcalcemia may result in toxic increase of intracellular calcium which can cause ventricular arrhythmias
What kind of cardiac pacing results in higher cardiac output, ventricular or atrioventricular pacing?
AV sequential pacing results in a 10-50% improvement in cardiac output compared w/ ventricular pacing alone
What pts. require fructosamine testing? What HbA1C level is diagnostic for DM?
- Fructosamine testing is used for pts. who have reduced RBC lifespans (hemolytic anemia, sickle cell disease)
- A HbA1C level of 6.5% or higher, is diagnostic for DM
What roles do pKa/concentration/lipid solubility play when administering local anesthetics?
- pKa and concentration determine the SPEED of onset
- Lipid solubility determines potency, duration of action, and degree of protein-binding
What information is transmitted through the posterior columns/spinothalamic tract/corticospinal tract?
- Posterior Columns: carry touch/vibratory sensation
- Spinothalamic Tract: transmits pain/temperature signals
- Corticospinal Tract: descending motor information
What anesthetic drugs are affected by anti-retroviral (HAART) medications?
- Benzodiazepines and opioids are the most commonly affected (usually prolonged half-life). Protease inhibitors tend to have the most drug interactions.
- Neuromuscular blocking drugs are usually NOT affected
What is the most common side effect of NSAIDs in the elderly?
10-20% of elderly pts. will experience dyspepsia
-There is an increased risk of A-fib, CHF, renal toxicity, and GI bleeding; although these risks are all lower than development of dyspepsia
What are the potential uses for FFP (6)? What are the least stable factors in FFP?
- Treatment of specific factor deficiencies, coagulopathy related to hepatic insufficiency, TTP, dilution coagulopathy after massive RBC transfusion, anti-thrombin 3 deficiency, reversal of warfarin therapy
- Factors 5 and 8 are the least stable factors in FFP and can degrade above 4 degrees Celsius
What agents are contraindicated in MI w/ cardiogenic shock? What agents should be used?
- Vasodilators (nitroglycerin/morphine) are contraindicated in the setting of MI w/ cardiogenic shock
- Positive inotropic agents should be used (dopamine, dobutamine)
What is the best type of anesthetic to use for combined somatosensory/motor evoked potential monitoring?
An intravenous technique w/ either no neuromuscular blockade, or a stable blockade of 1-2 twitches to allow for accuracy of monitoring
What is the most common reaction that occurs in pts. receiving a blood transfusion? Who does it occur in most commonly?
- Non-hemolytic febrile reaction is the most common reaction. It is defined as a temperature increase of greater than 1 degree Celsius w/o concurrent hemolysis
- This occurs b/c recipient antibodies cause lysis of donor leukocytes
- Febrile reactions are relatively common in multi-transfused and multiparous pts.
What is the mechanism for cardiac toxicity from local anesthetics? What are presenting signs of LAST?
- Toxicity involves delayed repolarization via action potential inhibition w/ the binding of voltage-gated Na channels
- Local anesthetic toxicity can present w/: perioral numbness, metallic taste, confusion, seizures, and ventricular tachycardia/fibrillation, or asystole
What are risk factors for development of heparin resistance (5)? What is the treatment?
- Anti-thrombin levels <60% of normal
- Platelet count 300,000 or greater
- Preoperative heparin therapy
- Use of low molecular weight heparin
- Age 65 or greater
-Treatment includes supplemental heparin, anti-thrombin 3, or FFP
What nerves are involved in an ankle block?
- 5 nerves must be blocked:
1. Sural
2. Saphenous
3. Superficial peroneal (first 3 are purely SENSORY)
- Tibial
- Deep peroneal (these last 2 are motor AND sensory)
What is the most common type of nerve injury postoperatively? What are the risk factors?
- Ulnar nerve injury. Males are more likely than females to develop ulnar neuropathy
- The brachial plexus is also highly vulnerable
- Risk factors: male gender, BMI >38, prolonged postoperative bed rest
What is the current theory for how malignant hyperthermia is transmitted?
-The genetic inheritance patterns are not completely understood- autosomal dominant inheritance w/ variable penetrance is currently how it is thought to be transmitted
Differences between gastroschisis and omphalocele?
- Gastroschisis: occurs to the right of the umbilicus. Has a higher incidence of heat loss, rapid dehydration, infection and postoperative bowel hypo-motility than omphalocele
- Omphalocele: central defect of the umbilical ring. Typically larger defect than gastroschisis (stomach and liver are often involved). Often assoc. w/ other physical/chromosomal anomalies.
Pectus carinatum is more commonly seen in males or females? When do pts. present for surgery?
- It is more common in males. Pts. typically present in their adolescent years
- The postoperative course is complicated by high analgesic requirements and respiratory complications (i.e. flail chest)
In a spontAneously breathing pt. using a Mapleson A circuit, how much fresh gas flow should be used to prevent rebreathing of CO2?
- The FGF must be equal to the minute ventilation to prevent rebreathing of exhaled gas
- The FGF must be equal to 1-2 times minute ventilation in the Mapleson D, E, and F circuits in order to prevent rebreathing of exhaled gas during CONTROLLED ventilation
What is a complication following parathyroidectomy? What are the symptoms?
- Hypocalcemia
- Signs/symptoms: distal paresthesias, tetany, and in severe cases, seizures and laryngospasm
How can perioperative median nerve injury occur?
- It can occur from forced elbow extension (after neuromuscular blockers have been given), or by iatrogenic trauma during i.v. placement in the antecubital fossa
- Presents as decreased sensation over the lateral 3.5 fingers, or loss of ability to oppose the 1st and 5th digits
How is massive transfusion defined? When is platelet transfusion indicated?
- It is defined as receiving more than 10 units of blood products in a 24 hour period
- In a massive transfusion, platelet transfusion is indicated if less than 75,000 and in pts. w/ ongoing bleeding if less than 50,000
Anesthetic considerations in pts. w/ Down syndrome/rheumatoid arthritis?
- Cervical spine instability
- The transverse and alar ligaments provide support for the atlantoaxial joint
What are differences between volume control and pressure control ventilation?
- Volume control uses a constant flow rate to deliver a breath
- Pressure control delivers the breath as a deceleration, which improves pt. comfort
What lesions are assoc. w/ hypoplastic left heart syndrome (5)?
- Atrial septal defects
- Stenotic/atretic mitral/aortic valves
- Hypoplastic left ventricle
- Hypoplastic ascending aorta
- Patent ductus arteriosus
What are physiologic changes that occur in obese pts.? How should doses be given for propofol, succinylcholine, rocuronium?
- They have increased butyrylcholinesterase activity and extracellular fluid volume
- Total body weight: maintenance infusion of propofol, succinylcholine
- Lean body weight: induction dose of propofol, fentanyl, thiopental
- Ideal body weight: rocuronium, vecuronium
What are potential obstetric nerve injuries during childbirth and/or obstetric surgery?
-Lesions to the lumbosacral trunk, common peroneal nerve, meralgia paresthetica (lateral femoral cutaneous nerve), femoral nerve, and obturator nerve
What are physiologic goals for brain-dead donors (organ procurement)?
- MAP of 60 or greater
- Urinary output of 1 mL/kg/hr or greater
- Left ventricular EF of 45% or greater
-A 3-drug protocol is often used: thyroid replacement therapy, steroids, vasopressin
What is the triad of TURP syndrome? What is the treatment?
- Elevated systolic and diastolic pressures
- Bradycardia (may be due to HTN or increased ICP)
- Mental status changes
-Symptomatic pts. w/ NA <120 should have the serum osmolality corrected w/ 3% hypertonic saline and loop diuretics
What is amniocentesis used for? What technique should be used for sampling if the fetus is less than 15 weeks old?
- Amniocentesis is used for diagnosis and treatment of fetal disorders
- Chorionic villus sampling should be performed if the fetus is <15 weeks old
What should be done after cardiac arrest and ROSC?
- A 12-lead EKG should be obtained ASAP to determine whether acute ST-segment elevation is present
- Goals: O2 sat 94-99%, avoidance of hyperthermia, treat hypotension if systolic is <90 or MAP is less than 65
What are considerations in pts. w/ transplanted lungs?
- Transplanted lungs are denervated and cough reflex/mucociliary function will likely be impaired
- Lymphatic drainage is also absent and predisposes pts. to pulmonary edema w/ over-zealous fluid administration
How does thiopental affect the cerebral flow-metabolism relationship and cerebral autoregulation?
- They remain intact w/ use of thiopental
- Thiopental decreases cerebral blood flow and CMRO2 by 30% w/ induction doses, and by 50% upon achievement of an isoelectric EEG
What changes are seen in the renal function of pregnant pts.?
Increased GFR (by about 50%) w/ decreases in urea, uric acid, and creatinine. An increase in glycosuria is also seen
What is seen in pts. w/ hepatopulmonary syndrome?
- Intrapulmonary vascular dilatations
- Increased A-a gradient
- Hepatic failure
- Excessive levels of circulating nitric oxide cause V/Q mismatching
- A positive contrast-enhanced ECHO supports the diagnosis in a pt. w/o underlying cardiopulmonary disease**
What can be done when a pt. has a decreasing mixed venous saturation?
- Focus on increasing cardiac output and arterial saturation. If it remains low, consider giving a RBC transfusion
- In cases of sepsis or high catabolic states, treating the underlying reason for increased O2 consumption can also improve mixed venous saturation
What lung values increase w/ aging? What values decrease?
Increase:
- Closing capacity
- FRC
- Residual volume
Decrease:
- Vital capacity
- Diffusion capacity
Where are M2 and M3 receptors found? How do opioids cause miosis?
- M2: heart, lungs
- M3: smooth muscle (vascular, airway, ocular)
*Opioids cause miosis by binding to opioid receptors on the parasympathetic Edinger-Westphal nucleus in the brainstem. This nucleus then stimulates M3 muscarinic receptors, causing pupil constriction
What are the 5 criteria that may predict need for postoperative mechanical ventilation for pts. w/ myasthenia gravis?
- Duration of disease 6+ years
- Presence of pulmonary disease(s) unrelated to MG (i.e. COPD)
- Vital capacity of <2.9 L
- Negative inspiratory force <20 cm H2O
- Daily pyridostigmine dose >750 mg
-The leading predictor for postop respiratory failure is the inability to clear secretions and produce a strong cough
During closure of gastroschisis, what 2 factors suggest a staged-procedure should be performed?
-Increases in central venous pressure above 4 mm Hg, and intragastric pressure above 20 is assoc. w/ increased ischemia of the bowel
What agent should be used for uterine relaxation in a pt. w/ a retained placenta?
-Nitroglycerin. Volatile anesthetics are a potential 2nd option if nitro is ineffective
What is the difference between type 1 and 2 hepatorenal syndrome?
- Type I: ACUTE renal failure caused by an inciting event in pts. w/ liver cirrhosis
- Type II: gradual onset of renal failure not assoc. w/ an inciting event
*Unlike type 2, type 1 improves w/ treatment and stabilizes. Vasoconstrictors and volume expanders are the mainstay of treatment. Liver transplant is the definitive treatment for type 1/2 HRS
Which molecule is more active, T3 or T4?
Triiodothyronine is 3-4 times more active than thyroxine and directly affects the myocardium, causing lymphocytic and eosinophilic infiltration. T3 also causes fibrotic/fatty changes within the myocardium
Does magnesium prolong or shorten neuromuscular blockade? What about calcium?
- It prolongs neuromuscular blockade w/ non-depolarizing agents
- Calcium shortens neuromuscular blockade w/ non-depolarizing agents (it increases release of ACh)
What pts. have increased production of acetone during use of a closed circuit technique?
- Alcoholics, pts. w/ cirrhosis, malnutrition, or ketoacidosis. Acetone is removed by the lungs during exhalation
- Rebreathing of acetone can lead to nausea/vomiting/slow emergence
What factors attenuate hypoxic pulmonary vasoconstriction? How is HPV modulated?
- HYPOcapnia and alkalosis attenuate HPV
- HPV is triggered locally in the hypoxic alveolus by PAO2 and PvO2 and modulated in a paracrine fashion by local vasodilators and vasoconstrictors (i.e. nitric oxide/endothelin). It is NOT modulated by the autonomic nervous system
What determines duration of action for opioids? Why does fentanyl have faster onset than morphine?
- Lipid solubility determines the duration of action for opioids
- Lipophillic compounds (fentanyl) have faster onset and decreased duration of action compared to HYDROphillic compounds (morphine).
- Faster onset is due to penetration across the blood-brain barrier and decreased duration of action is due to redistribution into peripheral tissues
What are the premedication doses for midazolam/ketamine in pediatric pts.?
- Midazolam dose increases w/ decreasing age. Total oral dose should not exceed 15-20 mg. It is effective within 10-15 minutes.
- Oral ketamine dose is 5-6 mg/kg. IM dose is 2-5 mg/kg and is effective within 5 minutes
What are the management goals for pts. w/ cardiac tamponade?
-To keep the heart ‘full, fast, and tight’
Maintain preload w/ volume resuscitation, keep heart rate up, and maintain SVR w/ pressors
What is the standard therapy for hemophilia A?
- Factor 8 concentrate. Mild cases of hemophilia may respond to desmopressin.
- A factor 8 level of 30% for mild hemorrhages and at least 50% for severe hemorrhages is advisable
Where does dexmedetomidine act to produce its sedative-hypnotic effect?
It involves endogenous sleep pathways through alpha-2 receptors in the locus ceruleus
What is responsible for ‘fade’ during non-depolarizing neuromuscular blockade?
- Nondepolarizing neuromuscular blocking drugs bind to presynaptic and post-synaptic receptors. They prevent re-uptake of ACh at presynaptic receptors.
- As a result, ACh becomes depleted w/ each TOF stimulation, causing a ‘fade’
What facet block location has the highest chance of intravascular injection?
Cervical facet injections carry a higher risk of intravascular complications. This is due to the vertebral artery lying just lateral to the cervical facet joint
What are potential causes for a unilateral epidural block?
- An epidural catheter that is located laterally in the epidural space
- Inadequate local anesthetic
- Presence of the plica mediana dorsalis (midline fold on the dura mater that extends to the ligamentum flavum)
What are risk factors for cauda equina syndrome after insertion of intrathecal catheters?
- Use of a MICROcatheter
- High local anesthetic concentration
- Directing the tip in the dependent direction
- Slow and low-pressure injection of local anesthetic
*Factors that contribute to maldistribution of local anesthetic (such as spine tumors) have been reported in cases of CES
What is the only modality which consistently shows a reduction in post-thoracotomy respiratory complications?
Thoracic epidural catheter placement
What can happen when a bilateral carotid endarterectomy is performed?
Billateral carotid body denervation can occur- it can impair the ventilatory response to mild hypoxemia. This is much more likely to occur and cause significant respiratory depression when opioids are given
Up to what age should neonates be monitored after general anesthesia?
- Up until 60 weeks post-conceptual age (to avoid episodes of apnea and bradycardia)
- Post-conceptual age is calculated by subtracting the # of weeks born before 40 weeks from the chronological age
What effect do volatile anesthetics have on cerebral blood flow at low and high concentrations?
- They tend to decrease CBF by decreasing cerebral metabolic rate of O2 consumption (at 0.5-1.0 MAC)
- At higher concentrations, they tend to increase CBF by causing cerebral vasodilation (at 1.5-2.0 MAC)
*Nitrous oxide does NOT cause a decrease in CMRO2**
What are the most common causes of post-partum hemorrhage?
- Uterine atony
- Retained placenta
- Genital-tract trauma
- Coagulation disorders
What are absolute contraindications for shock wave lithotripsy?
- Pregnancy
- Bleeding disorders/anticoagulation therapy
What is the recommended initial treatment for a hyperoxic seizure during hyperbaric oxygen therapy?
- Immediate reduction in the inspired PO2. The chamber should not be decompressed until after the seizure has stopped (due to risk of pulmonary barotrauma if the pt. is unable to exhale)
- Pts. receiving bleomycin are at increased risk for developing fatal pulmonary oxygen toxicity from supplemental oxygen administration**
What is the 1st-line pharmacological treatment of symptomatic bradycardia in adults?
I.V. atropine (this should not delay pacing if needed)
Where is the stellate ganglion located? What are potential complications of doing a stellate ganglion block?
- The ganglion is the fusion of the C7 and T1 cervical sympathetic ganglion. It lies on the anterior surface of the C7 vertebral body. The approach is at C6 b/c the vertebral artery lies anterior to the C7 transverse process
- Complications: hoarseness (unilateral paralysis of recurrent laryngeal nerve), paralysis of phrenic nerve, hematoma, pneumothorax, etc
What changes occur w/ tourniquet inflation/deflation?
- Inflation: causes HTN and increased HR
- Deflation: causes HYPOtension (due to ischemic mediator-induced vasodilation). After deflation, increased lactate/K/End-tidal CO2 occur. Metabolic acidosis is often seen
What things can lead to degradation of the endothelial glycocalyx layer?
- Hypervolemia, hypoxia/ischemia, inflammatory factors, and atrial natriuretic peptide
- Injury can lead to development of edema
How long should nitrous oxide be avoided after injection of A.) Air, and B.) sulfur hexafluoride injection intraocularly?
- If air is used, 5 days
- If SF6 is used, 10 days (will create bubble expansion if used)
Does the placenta consume oxygen? What promotes O2 transfer from mother to fetus?
- Yes. The O2 consumed by the placenta decreases O2 available for transfer to the fetus
- Mechanisms which promote O2 transfer from mother to fetus: higher fetal Hb concentration, the Bohr effect, and the double Bohr effect
What are the 4 components of thromboelastography (TEG)?
- “R” (Reaction Time): from time 0 to initial clot formation. Normal range is 1-3 minutes
- “K” (Coagulation Time): measures speed of clot formation and strengthening. It relies on fibrinogen. Equal to the time from amplitude of 2mm to 20 mm
- “MA” (Maximum Amplitude): measures the strength of the fully formed clot. It reflects platelet # and function (primarily), as well as fibrin cross-linking. Normal is 50-60 mm
- Alpha-Angle: speed of clot formation. This relies on fibrinogen. Normal angle is 45-55 degrees.
What does a P50 value indicate (for hemoglobin)?
- Normal value is 27
- It corresponds to the partial pressure of O2 at which 50% of the Hb is saturated at normal pH and temperature
What current range is associated w/ high risk for intraneural injection during peripheral blocks?
Motor stimulation w/ < 0.2 mA is associated w/ intraneural injection
What is a contraindication for use of droperidol?
It is contraindicated in any pt. w/ a documented prolonged QT, or in pts. w/ electrolyte disturbances (at risk for development of prolonged QT- i.e. hypomagnesemia)
What are the 3 main components of therapy in pts. w/ DKA?
- Intravenous fluids
- Insulin
- Electrolyte replacement
What local anesthetics can be used for intravenous regional anesthesia (3)?
- Lidocaine (0.5-2%)
- Prilocaine (0.5%)
- Levobupivicaine (0.125%)
What are symptoms of congenital muscular dystrophy?
- They present in infancy w/ hypotonia, feeding difficulty, respiratory dysfunction
- They are NOT assoc. w/ increased risk for MH, but can lead to rhabdomyolysis or cardiac arrest after general anesthesia
What pts. are at risk for developing metformin-associated lactic acidosis? Should it be taken perioperatively?
-Metformin is excreted 90% unchanged by the kidneys. It should be continued perioperatively except in cases of acute renal failure, or in situations where the risk of renal insufficiency is high (i.e. contrast administration)
Pts. w/ myasthenia gravis have increased sensitivity to which kind of muscle relaxants?
- They are very sensitive to NON-DEPOLARIZING neuromuscular blocking drugs (regardless of their treatment status)
- Pts. being treated w/ cholinesterase inhibitors (pyridostigmine) have reduced metabolism of succinylcholine- depolarizing relaxants are therefore more likely to cause prolonged phase I blockade
What are possible complications of a stellate ganglion block?
- Vasovagal reactions
- Intravascular/spinal injection
- Horner syndrome (ptosis, anhidrosis, miosis) may also have enopthalmos and hyperemia of the eye
What does the standard error of the mean describe?
It describes the PRECISION of the population mean
How do spinal cord stimulators work?
They activate the larger A-alpha and A-beta fibers to a greater degree than the smaller nociceptive A-delta and C fibers. This closes the ‘gate’ and impedes conduction of pain sensation past the substantia gelatinosa of the dorsal horn of the spinal cord
A latex allergy is caused by what type of immune reaction?
Type I IgE-mediated antibody response
What should be done in pts. w/ pre-operative acute viral hepatitis?
Surgery should not proceed unless deemed an emergency; the risk of morbidity and mortality is significantly elevated in these pts.
In most pts., greatest amount of heat loss during general anesthesia is due to what mechanism?
- Radiation
- This is followed by: convection, evaporation, and conduction
What are the respiratory changes in the pregnant pt. (4)?
- Cephalad movement of the diaphragm
- Increase in anteroposterior/transverse diameter of thoracic rib cage
- Decrease in FRC (decreased expiratory reserve volume/residual volume)
- Increase in INSPIRATORY reserve volume
Considerations for SSEPs/MEPs? What agent enhances MEP amplitude?
- SSEPs and MEPs are sensitive to volatile anesthetics, but MEPs are, to a greater degree
- Paralytic agents cannot be used w/ MEPs
- Ketamine will enhance MEP amplitude
Mallampati definitions?
- MP I: full view of soft palate/uvula/tonsillar pillars
- MP II: upper portion of uvula/soft palate/fauces
- MP III: hard palate/soft palate/base of uvula
- MP IV: hard palate only
Common cause of post-operative hypoxemia? Treatment?
Atelectasis (w/ resultant decreased FRC). This produces a (usually small) right-to-left shunt which is more responsive to increasing mean airway pressures/PEEP (vs. increasing FiO2)
How can cerebral salt-wasting syndrome vs. diabetes insipidus be distinguished? What is the treatment for DI?
- Cerebral salt-wasting syndrome causes LOW Na concentrations within the blood (low serum osmolality) w/ dehydration.
- DI causes polyuria, HYPERnatremia (HIGH plasma osmolality), low urine osmolality
- *Desmopressin is the treatment for DI**
1st-line treatment for symptomatic bradycardia?
Atropine (0.5 mg repeated every 3-5 minutes to a maximum of 3 mg)
Absorption of glycine-containing irrigation solution during TURP may lead to what symptoms?
It may lead to hyper-ammonemia, causing neurological complications (encephalopathy and coma)
What happens to closing capacity in obese pts.?
Obese pts. have severely reduced FRC, which narrows the gap between closing capacity and tidal volume, predisposing these pts. to rapid desaturation w/ periods of apnea
What does a z-score mean if it is outside the range of the critical value?
In a test of proportions, if the z-score is outside the range of the critical value (higher than the critical value), the populations are unlikely to be similar (i.e. one group has greater effect w/ the intervention, etc)
What does the hepatic extraction ratio refer to? What are drugs w/ LOW hepatic extraction ratios (4)?
- Hepatic extraction ratio is the fraction of drug removed from blood passing through the liver
- Drugs w/ LOW hepatic extraction ratios: diazepam, methadone, rocuronium, and thiopental
What reaction can pts. w/ myotonic dystrophy have when succinylcholine is given?
-Excessive fasciculations/contractures may occur which can impair ability to ventilate and intubate
(Myotonic dystrophy is a disease of impaired muscle relaxation)
What are concerns w/ burn pts.?
- Large burns can cause hypothermia leading to coagulopathy (also impaired fibrinogen production)
- Succinylcholine should be avoided 48 hours after burn injury
Causes of prolonged PT?
- Liver disease
- Cystic fibrosis (deficient vitamin K)
- Warfarin
Lupus anticoagulant causes prolonged PTT (these pts. are actually PROthrombotic)
What 4 things increase statistical power?
- Increasing sample size
- Increasing effect size
- Increasing alpha (e.g. p-value)
- Reducing population variability (e.g. standard deviation)
