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Question 1

What spinal level does the great radicular artery (artery of Adamkiewicz) most commonly originate?

Answer 1

T9-12
Paraplegia following open thoracoabdominal aortic aneurysm repair occurs in 10-20% of pts due to cross clamping and hypoperfusion of spinal cord anteriorly.

Question 2

Most likely side effect of celiac plexus neurolytic block?

Answer 2

Orthostatic hypotension from splanchnic vasodilation caused by sympatholysis. Can also cause diarrhea from unopposed parasympathetic tone.

Question 3

How do you improve spinal cord perfusion pressure in aortic surgery?

Answer 3

Increase MAP and reduce CSF pressure using lumbar CSF drain.

SCPP = MAP - CSF pressure (same as CPP = MAP-ICP)

Question 4

What is the blood supply to the spinal cord?

Answer 4

Vertebral arteries –> single ASA that supplies anterior 2/3rds of spinal cord.
Two PSAs from PICA supply posterior 1/3rd of spinal cord.

Cervical cord is supplemented by radicular branches from vertebral arteries. Thoracolumbar cord supplemented by radicular arteries, especially great radicular artery of Adamkiewicz.

Question 5

What movement is preserved after lumbar plexus block via posterior approach?

Answer 5

Plantar flexion of foot (lumbar plexus block spares sciatic nerve)

Question 6

What muscles does sciatic nerve innervate?

Answer 6

gastrocnemius, soleus, plantaris, digital flexors

Question 7

What is lumbar plexus formed by?

Answer 7

Ventral divisions of first four lumbar nerves (L1-L4), small contribution from T12 (subcostal nerve)

Question 8

What nerves does lumbar plexus block?

Answer 8

femoral, lateral femoral cutaneous, obturator

Question 9

What muscles does obturator nerve innervate?

Answer 9

Hip adduction (adductor longus, brevis, magnus muscles)

Question 10

What muscles does femoral nerve innervate?

Answer 10

Hip flexion (iliopsoas, quadriceps femoris) and extension of lower leg at knee (quadriceps femoris)

Question 11

How to visualize the ascending aorta on TEE?

Answer 11

Long axis view of ascending aorta, mid-esophageal, at about 100-110 degrees

Question 12

How is PDA treated medically?

Answer 12

Fluid restriction and indomethacin - nonselective COX inhibitor. Inhibits prostaglandin synthesis. Prostaglandins usually aid in smooth muscle relaxation within ductus arteriosus and prevent closure.

Question 13

Pathophys of PDA? What can PDA lead to if untreated?

Answer 13

allows a portion of oxygenated blood from the left heart to flow back to the lungs by flowing from the aorta, which has a higher pressure, to the pulmonary artery. Symptoms are uncommon at birth and shortly thereafter, but later in the first year of life there is often the onset of an increased work of breathing and failure to gain weight at a normal rate. With time, an uncorrected PDA usually leads to pulmonary hypertension followed by right-sided heart failure.

Question 14

What causes increased risk of DVT during pregnancy?

Answer 14

Increase in circulating levels of fibrinogen - fibrinogen levels double in pregnancy.

Other increased coagulation factors are: factors VII, VIII, IX, X and XII.

Prothrombin time (PT) and partial thromboplastin time (PTT) are shortened by about 20% in pregnancy

Question 15

Pt presenting with flushing, diarrhea, wheezing, right-sided cardiac abnormalities (fibrous deposits on tricuspid valve) - diagnosis? How to test for it?

Answer 15

Carcinoid syndrome from carcinoid tumor. Excrete large amts of serotonin, which is broken down and excreted as 5-hydroxyindoleacetic acid in urine (test for this in urine).

Lung metabolism of serotonin leads to right sided (but prevents left sided) involvement of the heart.

Question 16

What nephron segment absorbs majority of sodium?

Answer 16

Proximal tubule (65-80% of Na absorbed here)

Question 17

What factors can result in variable activated clotting times?

Answer 17

Hemodilution, hypothermia, platelet counts below 30-50K/ml and concomitant administration of other medications which affect platelets.

Question 18

Induction strategy for peds pt with congenital emphysema going for resection of emphysematous bleb?

Answer 18

Mask induction with sevoflurane, spontaneous respiration. Nitrous oxide is contraindicated.

Question 19

What are the pKa of common opioids (fentanyl, sufentanil, alfentanil, remifentanil, morphine)?

Answer 19

Fentanyl - 8.4
Sufentanil - 8.0 
Morphine - 8.0 
Remifentanil - 7.1 
Alfentanil - 6.5

Question 20

What is duration of effect of opioids determined by?

Answer 20

Primarily by lipid solubility, not drug elimination as with many other drugs.

Morphine has a longer onset time and duration of action because more difficult time crossing blood-brain (or blood-spinal cord) barrier due to lower lipid solubility.

Question 21

Are ionized or nonionized drugs more lipid soluble?

Answer 21

Ionized drugs are polar and do not readily pass through cell membranes. Nonionized drugs are significantly more lipid soluble.

Question 22

What is the pKa of a drug refer to?

Answer 22

the pH at which it exists in equal parts of ionized and nonionized forms.

Opioid with pKa less than physiologic pH (~7.4) will have much greater NONionized fraction, whereas opioid with pKa >7.4 will have greater ionized fraction.

Question 23

What is mechanism for neurogenic pulmonary edema a few hours after traumatic brain injury?

Answer 23

Massive sympathetic discharge. Presents with rapid onset, severe pulmonary vascular congestion, intra-alveolar hemorrhage and protein-rich edematous fluid. Tx - supportive and reduce intracranial hypertension

Question 24

Accumulation of metabolites of meperidine in renal dysfunction can cause what?

Answer 24

Seizures - active metabolite is normeperidine and is neurotoxic.

Question 25

What are morphine's metabolites and consequences of accumulation?

Answer 25

``` In renal disease, metabolites can accumulate. Active metabolite (morphine-6-glucuronide/M6G) has nearly 100-fold higher potency than morphine but has equal or decreased affinity for mu-opioid receptors. Increased potency can lead to respiratory depression in renal failure due to accumulation from delayed excretion. ``` Morphine's inactive metabolite, morphine-3-glucuronide M3G, has nearly 300-fold lower affinity for mu-receptors but it has neuroexcitatory effects -> myoclonus and allodynia are seen after large doses.

Question 26

What are morphine's metabolites and consequences of accumulation?

Answer 26

``` In renal disease, metabolites can accumulate. Active metabolite (morphine-6-glucuronide/M6G) has nearly 100-fold higher potency than morphine but has equal or decreased affinity for mu-opioid receptors. Increased potency can lead to respiratory depression in renal failure due to accumulation from delayed excretion. ``` Morphine's inactive metabolite, morphine-3-glucuronide M3G, has nearly 300-fold lower affinity for mu-receptors but it has neuroexcitatory effects -> myoclonus and allodynia are seen after large doses.

Question 27

What is common side effect of meperidine?

Answer 27

Tachycardia - meperidine molecule resembles atropine.

Question 28

What is Gilbert disease?

Answer 28

Decrease in activity of bilirubin glucuronyltransferase (needed for hepatocyte uptake of unconjugated bilirubin). They have increased risk of jaundice, especially following multiple pRBC transfusions.

Question 29

Distressed fetus with bradycardia is more susceptible to toxicity from what drug?

Answer 29

Lidocaine - crosses placenta and accumulates due to ion trapping from fetal acidosis. In setting of decreased uterine blood flow (such as significant maternal blood loss) fetal pH will decrease further. A basic drug, like local anesthetic, crosses placental in un-ionized form accepts a H+ ion in more acidic environment and becomes ionized.

Question 30

What common drugs don't cross placenta?

Answer 30

"He Is Going Nowhere Soon" = Heparin, Insulin, Glycopyrrolate, Non-depolarizing muscle relaxants, Succinylcholine

Question 31

Primary site of dexmedetomidine metabolism and excretion?

Answer 31

Dexmedetomidine undergoes extensive hepatic metabolism including conjugation, n-methylation, and hydroxylation followed by conjugation before being excreted in urine and feces. Its elimination half-life is 2-3 hours.

Question 32

``` What is the order of plasma elimination half life of the following? (shortest to longest) Alprazolam Diazepam Flumazenil Lorazepam Temazepam Midazolam ```

Answer 32

``` Shortest: Flumazenil (0.7 - 1.3h) Midazolam (1.7-2.6h) Temazepam (10h) Alprazolam (6-27h) Lorazepam (11-22h) Diazepam (20-50h) ```

Question 33

What are Boyle, Avogadro, Charles, and Guy-Lussac laws in relation to gases?

Answer 33

Boyle: P1 x V1 = P2 x V2 (changes in volume inversely related to changes in pressure) Avogadro: equal volumes of all gases at the same pressure and same temperature will contain the same number of molecules Charles: V1/T1 = V2/T2 Guy-Lussac: P1/T1 = P2/T2

Question 34

What is the renin-angiotensin-aldosterone system?

Answer 34

RAAS is one of the primary regulators of volume and blood pressure. Angiotensinogen is synthesized in liver, circulates in plasma until cleaved by renin to angiotensin I. Renin is released by juxtaglomerular apparatus in response to B1 activation, decreased renal perfusion pressure (glomerulus) or decreased NaCl concentration at the macula densa (distal convoluted tubule). Angiotensin I is cleaved to form active angiotensin II by angiotensin-converting enzyme (ACE) in the lungs.

Question 35

Side effects of methylergometrine and carboprost?

Answer 35

Methylergometrine = hypertension Carboprost = bronchospasm "methylergometrine makes the blood pressure go HYER (higher): HY ER: metHYlERgometrine HYpERtension Also, the double O's go together: OOS: carbOprOSt brOnchOSpasm"

Question 36

What are estimated blood volumes by age for premature infant to adult male/female?

Answer 36

``` Age Group Blood Volume Premature infant 90-105 mL/kg Full-term newborn 80-90 mL/kg Infant 3-12 months 70-80 mL/kg Child 1-12 years 70-75 mL/kg Adult male 65-70 mL/kg Adult female 60-65 mL/kg ```

Question 37

Indications for spinal cord stimulator?

Answer 37

accepted indications for spinal cord stimulation include (but are not limited to): thoracic and lumbar post-laminectomy syndrome (“failed back syndrome”), post-herpetic neuralgia, phantom limb pain, cauda equina syndrome, CRPS I and II, cardiovascular angina, lower extremity ischemic pain, chronic cervical radiculopathy, and nerve root injury.

Question 38

Relative contraindications to spinal cord stimulator?

Answer 38

cognitive and psychological disability that interferes with proper usage and understanding of the device. This includes significant somatization/somatoform disorders and unmanaged substance abuse.

Question 39

Absolute contraindications to spinal cord stimulator?

Answer 39

Absolute contraindications for spinal stimulation include (but are not limited to): sepsis, coagulopathy, previous surgery or trauma obliterating the spinal canal, localized infection, and spinal bifida.