Regional And Neuraxial

Question 1

Benefits of neuraxial Anesthesia?

Answer 1

That altogether translates into fewer DVTs, less bleeding and transfusions (in some specific surgical cohorts), less splinting and respiratory complications, less pain, and for reasons less clear (likely related to the immune response), lower rate (slightly) of cancer recurrence (for specific tumors undergoing specific management). Older data regarding decreased coronary events with neuraxial anesthesia probably cannot be generalized to more modern techniques (anesthetics).

Question 2

Order of structures when placing neuraxial

Answer 2

Supraspinous ligament, then interspinous ligament, then ligamentum flavum, then dura, then arachnoid

Question 3

Tell me what comes from the posterior vs anterior part of nerves

Answer 3

The posterior nerve root carries somatic and visceral sensation (pain) (answers B, C & D) and the anterior nerve root carries motor and sympathetic outflow (answers A & E). Review hand dermatomes!

Question 4

What is a differential blockade, and how can it happen?

Answer 4

In the case of hyperbaric local anesthetic (for example), the more caudad areas near the site of injection will have higher concentrations of local anesthetic and cephalad areas have lower concentrations. As concentrations lower, motor nerves are not inhibited, but sensory nerves are (accounting for loss of motor block but dense sensory block). At even more cephalad levels the concentration is low enough to the point where temperature (and pinprick) discrimination is lost, but the sensory block is inadequate to block pain. This is called a differential blockade.

Question 5

The sympathetic chain runs from what?

Answer 5

T1 to L2

Question 6

Why no spinals in AS?

Answer 6

Decreased afterload will therefore decrease aortic diastolic pressures, leading to myocardial ischaemia. Because cardiac output against a stenotic aortic valve requires high LVEDP (now decreased due to the spinal) and adequate contractility (now decreased due to the myocardial ischaemia), cardiac output falls, leading to a vicious cycle.

Question 7

Neuraxial in a COPDer extreme

Answer 7

Altogether, in most cases (and probably every case below the umbilicus), neuraxial anesthesia is a safer choice for a severe COPD’er. Neuraxial anesthesia will affect intercostal (inspiration and expiration) and abdominal (expiration/cough) muscles and decrease pulmonary reserve. However, tracheal intubation and general anesthesia in a severe COPD’er also has many (many, many, many) deleterious effects on post-operative pulmonary function.

Question 8

Having seizures after getting a block-give ____ and then give ___ if that’s not around.

Answer 8

Benzos and then give Propofol of benzos aren’t available

Question 9

What is TNS? Most common offender? How to reduce the incidence?

Answer 9

Transient neurologic symptoms (TNS) is a well described “benign” phenomenon likely caused by radicular irritation following spinal anesthesia. Lidocaine is the most common offender (answer C) and its incidence is increased with obesity and lithotomy position. Symptoms typically resolve within a couple days to a week. Aspirating equal volume of CSF prior to injection can reduce the incidence.

Question 10

Why has chloroprocaine had a bad rep?

Answer 10

Chloroprocaine has had an especially bad rap through the years (answer D). Prolonged neurologic deficits have been associated with its intrathecal use, possibly due to preservatives used in the solution. Severe back-pain has also been reported after epidural chloroprocaine has been used, again with the possibility of preservatives being the cause.

Question 11

Why does intralipid work for LAST? Why not Propofol in ACLS setting?

Answer 11

Intralipid supplies a lipid sink in which bupivicaine can be bound to and should be administered immediately. Propofol’s lipid emulsion may theoretically bind bupivicaine in this circumstance too, but its afterload and contractility depressing effects make it contraindicated in this setting.

Question 12

Tell me about Neuraxial and once daily dosing of enoxaparin

Answer 12

To keep things straight in your mind, you should think of enoxaparin at the once daily prophylactic dose and the twice daily treatment dose as two distinct drugs. Also, realize that the guidelines are not different for spinals and epidurals, its just that the epidurals have the catheter to worry about. So to start off with, and keep things simple, lets review a single shot spinal/ epidural. With low dose, once daily enoxaparin, you can place the block 12 hours after the last dose of enoxaparin and then restart low dose enoxaparin 12 hours later. The same is true for prophylactic twice daily therapy as well.

Question 13

Tell me about twice daily enoxaparin dosing

Answer 13

r high dose, twice daily treatment dose enoxaparin, you can place the block 24 hours after the last dose of enoxaparin and the recommendation has been changed from restarting high dose enoxaparin 24 hours after the block (or catheter removal) to no recommendation. Some believe that if there is clear evidence that a vein was violated (positive haeme), then delay subsequent enoxaparin 24 hours regardless of the dose.

Question 14

2015 enoxaparin and catheter guidelines

Answer 14

As of 2015 here are the guidelines regarding lovenox:

Enoxaparin Daily prophylactic:
Place it 10-12 hours after last dose/ Ok to restart 6-8 hours after catheter placed / Remove catheter 10-12 hours after last dose/ Restart 4 hours after catheter removed
Enoxaparin BID prophylactic:
Place it 10-12 hours after last dose/ Do not use while catheter in place/ Restart 4 hours after catheter removed
Enoxaparin Daily therapeutic:
Place it 24 hours after last dose/ Do not use while catheter in place / No recommendation when to restart after catheter removed

Question 15

INR, PTT, and clopidigrel as it relates to Neuraxial Anesthesia

Answer 15

A bit of a trick question (as warfarin would not expected to raise PTT significantly), but an elevated PTT (some say above 40) is a contraindication. As far as INR, anything below 1.5 is within guidelines. Regarding aspirin and NSAIDS, there is no contraindication, even with mildly elevated INR. Clopidogrel should be discontinued for 7 days prior to epidural placement.

Question 16

Heparin and NA:

Answer 16

A couple important points that you must know is this: For heparin, neuraxial placement can occur at anytime on prophylactic dosing, otherwise a PTT should be drawn and be less than 40. After the block is placed, heparin at any dose can be started 1 hour after.

Question 17

List of AC and timing for block placement

Answer 17

Drug - Neuraxial block timing

Abciximab 2 days

Argatroban/ Bivalirudin / Lepirudin PTT < 40

Alteplase 10 days

Clopidogrel 7 days

Dabigatran 3 days

Dalteparin (prophy)/ (full dose) 12 hours/ 24 hours

Fondaparinux (prophy)/ (full dose) 48 hours/ 72 hours

Ticlopidine 14 days

Tirofiban/ Eptifibatide 8 hours

Question 18

Soooo…if you place a spinal using hyperbaric bupi, it’ll go to which level?

Answer 18

T5/T6/T7. Normal kyphosis of the back in the supine patient limits the movement of hyperbaric local anesthetic to about the T6 level.

Question 19

What CSF volume makes blocks go more cephalosporins? What conditions?

Answer 19

With decreased CSF volume, intathecal anesthetics tend to result in a higher block. Pregnancy and ascites can both result in engorgement of the epidural veins, leading to a reduction in volume of the dural sac and CSF. Advanced age have predictable decreases in CSF volume. Severe kyphoscoliosis is really a case by case basis, but it is a known and recognized risk factor. Surprisingly, obesity is not associated with higher spinal blocks.

Question 20

Adding epi to bupi vs to terracaine

Answer 20

The addition of epinephrine has minimal effect on bupivacaine and ropivicaine, but can extend tetracaine up to an additional half hour.

Question 21

What happens when you add Fentanyl to a spinal anesthetic?

Answer 21

Faster onset of block, but NO increased duration, no increased intensity of motor block, and no significant dose reduction of LA-because it doesn’t cause a dense enough block alone.

Question 22

Yep me about the lipophikic opioids and not lipophobic ones: , and why does the lipophopic one have more rosy rap spread and hang around for longer? Tell me more about intrathecal morphine and it’s onset, if it causes respiratory depression, etc. would you give IT morphing for outpatient t procedures?

Answer 22

By learning intrathecal fentanyl (question 25) and morphine, you can essentially get a gauge of other opioids as they represent the two extremes: lipophilic (fentanyl, sufentanyl) and hydrophilic (morphine). Because morphine is hydrophilic (lipophobic), it crosses the dura slower and has a much longer lifespan within the CSF than fentanyl.

Because morphine is hydrophilic (lipophobic), it crosses the dura slower and has a much longer lifespan within the CSF than fentanyl. Because of the slow clearance of the drug (and its hydrophilic properties) it has the greatest rostral spread among opioids. This means two important (board-worthy) things: First, a lumbar intrathecal injection will produce analgesia well into high thoracic levels. More lipophilic drugs like fentanyl will create a more narrow band around the site of injection. Drugs less lipophilic than fentanyl and less hydrophilic than morphine like hydromorphone or meperidine will have an intermediate level of rostral spread

Second, because of its long duration of action and high rostral spread, respiratory depression has two peaks, an early peak and a late peak. Like all opioids, soon after intrathecal injection, opioids can be detected in the CSF surrounding the brainstem, which can lead to respiratory depression. Unlike other opioids, morphine’s slow rostral spread leads to another peak of respiratory depression at about 6 hours after injection (answer A), but can occur later. A 600 mcg dose (less than 300 mcg is typical) leads to late respiratory depression in most people. Also, because of the late peak in respiratory depression, intrathecal morphine should not be used for outpatient procedures. Analgesia from intrathecal morphine has a slow onset (answer B) due to its hydrophilic nature and duration of action (in most cases) longer than 24 hours. Peak analgesic effects are typically at 6-12 hours after injection.

Question 23

Pruritus worse in intrathecal than IV administration?

Answer 23

Puritis following intrathecal administration of opioids is very common with all commonly used opioids, and is ubiquitously worse in the intrathecal administration than IV

Question 24

Opioids and urinary retention: what makes it worse?

Answer 24

Generally, the more lipophilic the drug, the less likely it will cause urinary retention; although, it is also dose dependent

Question 25

N/V with opioids

Answer 25

Nausea and vomiting is also (generally) less likely with lipid soluble opioids (fentanyl), and again is very dose dependent

Question 26

Fentanyl and sufenta with respiratory depression:

Answer 26

Fentanyl and sufentanyl have been associated with respiratory depression within 30 minutes after administration, but never after two hours (answer D), making them ideal outpatient opioid adjuvants.

Question 27

Meperidine-tell me about it-can you use it for surgeries alone?

Answer 27

Meperidine is an exception to other opioids in a variety of ways. Its atropine-like structure leads to increased heart rate, it has cardiac depressant effects, it produces more euphoria than other opioids, it has local anesthetic properties, and can reduce post-operative shivering. Its local anesthetic properties combined with its normal opioid properties make it possible to be used as a sole agent for neuraxial anesthesia (for less “stimulating” surgeries….whatever that means). The draw back is it makes the recipient miserable with nausea, vomiting, and pruritus. There is probably a good reason that you have never tried this drug in a spinal anesthetic before

Question 28

Why does Benadryl not work for itching caused by intrathecal administration of opioids? What can you use instead?

Answer 28

Intrathecal opioid mediated itching works through a central mechanism (likely through the opioid receptor) and does not involve histamine release. Diphenhydramine is not an effective treatment for this condition, but does effectively treat annoying nurses through its sedating properties. If you should want to actually treat the patient all of the above choices are far more effective. Ondansetron can be used both to prevent and treat. Propofol needs to be very carefully titrated to be sub-hypnotic and continued on a gtt. Nalbuphine can also be sedating, but is reportedly the most effective. Naloxone doses should be very small and below the dose which would reverse analgesia. Typically 0.04-0.08 mg will do the trick.

Question 29

Epinephrine doesn’t contribute heavily to density of epidural blocks, but does contribute to intrathecal. T/F

Answer 29

True

Question 30

Chloroprocaine-how is it metabolized? What does it do to other opioids?

Answer 30

Chloroprocaine is often administered at a 3% concentration for epidural anesthesia. Its duration in the epidural space is limited by venous uptake, where it is metabolized by pseudocholinesterase (half life just over 20 seconds). Older formulations contained preservatives, which led to neurotoxicity (controversial, bisulfite) or back pain (EDTA). Unlike other local anesthetics, epidural administration of chloroprocaine is thought to interfere with epidural opioid mediated analgesia which is the explanation of why she had significant post-operative pain (probably overstated and overblown, but still has boards potential)

Question 31

What is sacral sparing? What causes foot drop? Does foot drop happen with epidurals?

Answer 31

Sacral sparing is where a well functioning epidural is “patchy,” or less dense in L5-S2 distribution and is due to the large size of the nerve roots (requiring greater penetration by the local anesthetics). Bolusing the epidural with the patient in reverse trendelenburg is a common remedy.
Foot drop occurs secondary to injury to the peroneal nerve (often due to lithotomy position) and isolated foot drop is not consistent with epidural anesthesia related injury.

Question 32

What do you do if you placed an epidural, but find out the patient was taking Plavix?

Answer 32

The safest course of action on the boards is likely to wait 7 days (after discontinuing Plavix) and remove the epidural catheter, although this is obviously not the real-life answer. The incidence of clinically significant epidural haematoma in the presence of Plavix is unknown. An MRI would be indicated if the patient were symptomatic, but not in this setting (answer C). There is no evidence for platelet transfusion to prevent epidural haematoma, and consideration should be given to how recent the coronary stents have been placed

Question 33

After injecting 2 cc of bupivacaine during an interscalene block, the patient has a clonic-tonic seizure.

Answer 33

In-line or caudad direction of the needle too deep can potentially penetrate the vertebral artery. Small volumes of local anesthetics resulting in seizures almost always means intravascular injection on the boards.

Question 34

What will the IS block not cover?

Answer 34

The interscalene block classically has variable degrees of ulnar sparing (C8 & T1). It also has a variable block of proximal cutaneous shoulder and occasionally requires superficial cervical blockade to cover incisional pain.

Question 35

SC vs IS block-which one has more PTX? Can stellate ganglion block happen in both? Which one blocks ulnar nerve better? Which one has the higher incidence of Phrenic nerve block?

Answer 35

Supraclavicular block with ultrasound is one of the easiest and safest blocks to perform; however using nerve stimulator or paraesthesia technique, incidence of pneumothorax is higher than with interscalene (answer A). Stellate ganglion block (see question 36) has occurred with both blocks (answer B). The supraclavicular has a far higher frequency of adequately blocking the ulnar nerve (answer C). The incidence of phrenic nerve block with interscalene (using 30 cc of volume) is 100% and is about 40% with supraclavicular (answer D). Although large volumes of local anesthetics (20-40cc) can spread to the degree of significant overlap of the two blocks, there is still a predictable difference, especially in regards to blocking the shoulder and distal ulnar.

Question 36

Which block has the biggest risk for chylothorax?

Answer 36

Infraclavicular block (without ultrasound) has the highest risk of pneumothorax. If you hear chylothorax on the boards, it probably means either a subclavian central line or infraclavicular brachial plexus block was performed (on the left side, of course).

Question 37

If you block the axillary nerve, what distribution is not covered? Why?

Answer 37

The axillary approach does not address the musculocutaneous nerve as that has taken off from the lateral cord (giving rise to the musculocutaneous and part of the median) proximal to the area where the axillary nerve is blocked. The musculocutaneous nerve has to be blocked independently within the coracobrachialis muscle for lateral forearm coverage

Question 38

Under ultrasound guidance three nerves are seen around the axillary artery. Assuming the approach was made lateral to the axillary artery, blockade of the nerve closest to the entry point would result in sensory block of:

Answer 38

With a lateral approach (the side of the ultrasound probe closest to the biceps) the closest nerve to the needle at the skin would be the median nerve. Classically, the median nerve will be superior-lateral, ulnar superior –medial, and radial deep to the artery.

Question 39

UE nerve distribution and dermatomes!!!

Answer 39

Okay 😩

Question 40

With a Bier block, you want to release the tourniquet how?

Answer 40

Slowly-over 5-10 minutes, or leave tourniquet up for 45 min. You’re trying to avoid lidocaine toxicity. By slowly letting the tourniquet down it is assumed that small amounts of lidocaine are released and metabolized, avoiding plasma levels high enough to result in significant sequela. Keeping the tourniquet up for 45 minutes is also safe, but wasting OR time.

Question 41

What is the intercostobrachial block?

Answer 41

The intercostobrachial block is a field block of two nerves: the intercostobrachial nerve (T2) and median brachial cutaneous nerve (C8 & T1). Tourniquet pain, however, can be resistant to both dense peripheral nerve blocks as well as neuraxial anesthesia.

Question 42

Medial knee is covered by which nerve?

Answer 42

Obturator

Question 43

If pt has catheter with adequate coverage after initial bolus block, then catheter at 0.125% not covering same area, what do you do?

Answer 43

Increase the rate of infusion-not the concentration. Rate of infusion will have more of an effect.

Question 44

PTT and NA? INR and NA? NSAIDs??

Answer 44

an elevated PTT (some say above 40) is a contraindication. As far as INR, anything below 1.5 is within guidelines. Regarding aspirin and NSAIDS, there is no contraindication, even with mildly elevated INR. Clopidogrel should be discontinued for 7 days prior to epidural placement.

Question 45

IS block spares what?

Answer 45

The interscalene block classically has variable degrees of ulnar sparing (C8 & T1)

Question 46

Nerve medial to brachial artery:

Answer 46

Is the median nerve

Question 47

Wrist drop? Why?

Answer 47

Wrist drop is due to loss of wrist extensor function, which is a function of the radial nerve (median nerve = wrist flexion, pinch = ulnar). Nerve damage can occur due to surgical transection, prolonged tourniquet, positioning injury, needle transection, and intraneural injections. Needle transection and intraneural injections often result in no deficit, but in some individuals a prolonged nerve palsy is seen (rarely permanent). Pronation instead of supination can entrap the ulnar nerve between the ulnar canal and the arm board (although in this situation it makes no sense as that arm was presumably being operated on!).

Question 48

An anesthesiologist draws a line from the patient’s greater trochanter (GT) to the posterior superior iliac spine (PSIS) and another from the greater trochanter to the sacral hiatus. At the midpoint of the GT – PSIS line, another perpendicular line is drawn. At the point this line crosses the GT- sacral hiatus line, a stimulating needle is inserted. Successful block relies on which of the following being seen at 0.5 mA:
What block is this?

Answer 48

The block described is a classic sciatic nerve block at the level of the buttocks. The sciatic nerve innervates muscles responsible for plantar flexion (tibial portion) and dorsiflexion (peroneal portion). An isolated foot dorsiflexion would indicate an isolated peroneal nerve stimulation (answer E) or perhaps, stimulation of only peroneal fibers in the sciatic nerve (although at 0.5 mA, unlikely). Likewise, knee flexion (answer B) would require pure tibial stimulation and is less likely an indicator of a good block than an ankle twitch. Knee extension is through the femoral nerve (answer C). Isolated muscle twitch (answer D) is usually due to direct stimulation of the muscle and not the innervating nerve.

Question 49

Following an in-plane block of the sciatic nerve above the knee with the use of ultrasound, a patient has a sensory block of the mid plantar surface of the foot set up before dorsal surface of the foot. From which direction did the anesthesiologist most likely enter the patient’s skin relative to the ultrasound probe:

Answer 49

The sciatic nerve is composed of elements of the tibial nerve on the medial aspect and common peroneal nerve of the lateral aspect. The tibial nerve continues on to become the plantar nerves, innervating the plantar cutaneous surface. The peroneal nerve separates into superficial & deep. The superficial caries sensation from the dorsal surface (save the web space between the big and second toe which is deep peroneal).

Question 50

Following an ankle block, the patient complains of sensation on his lateral heel and lateral maleolus. Which of the following nerves was not blocked properly:

Answer 50

The sural nerve is an early takeoff of the tibial nerve and innervates cutaneous tissue on the posterior-lateral portion of the lower leg and foot. The saphenous nerve innervates cutaneous tissue on the posterior-medial portion of the lower leg and foot. The tibial nerve innervates most the plantar surface and the superficial peroneal innervates the dorsal surface.

Question 51

Easy way to make out anatomy on US

Answer 51

Notice that in this image (and in most images) of the axillary artery there is a white linear density coming off at 9 O’clock. This is a fascial layer separating the (short head) of the biceps muscle from the coracobrachialis muscle. Most of the time you will see this under ultrasound. Starting clockwise, the nerves you will encounter is median, ulnar, and radial in that order. If you like mneumonics, make one up. I use (M)ore (U)ltrasound (R)adiation, but use whatever you like.

Question 52

Snowman:

Answer 52

This image represents the C5-7 nerve roots in the classic “snowman” formation, with “A” representing C5, “B” representing C6, and “C” representing C7. Dermatomally (if that’s a word) speaking, the hand is innervated by C6, C7, and C8. C5 is carried by the radial and axillary nerves and innervate the shoulder and anterior arm and forearm, but not the hand. C6 is carried by the radial and axillary nerves as well (and somewhat the median technically, but that is being picky) and innervates the shoulder anterior-superior arm and thenar area. C7 innervates part of the dorsal shoulder and dorsal arm (and forearm) as well as digits 2 & 3. Notice the C8 and T1 are NOT reliably blocked here and therefore explains why there is generally a large degree of ulnar sparing with this block (ulnar nerve carries C8 and T1). As the block is performed more distally (as the brachial plexus exits the scalene muscles, you will image the upper, middle, and lower trunks of the brachial plexus). At this level, the upper trunk carries C 5 & C6, the middle trunk caries only C7, and the lower trunk carries C8 and T1.

Question 53

Muscles you’ll hit with infraclavicular block:

Answer 53

You can easily see two distinct muscles lying directly above the artery. From the skin, the first muscle one must pass through to perform the block is pectoralis major, and deep to that is pectoralis minor. Fascial lines are easily seen on this image separating the two muscles. The subclavius is a small muscle that lives just under (inferior) to the clavicle and is not in the path of this block, nor is it seen in this image. The subscapularis is deep to the artery and borders the inside (deep) side of the scapula. You might enter this muscle if you go way too deep with your needle. You might also hit the lung depending on which way your needle is pointing as well!

Question 54

Three structures needed to visualize in order to do femoral block. As long as you inject:

Answer 54

When performing a femoral block, three structures are essential to visualize for an effective block, and the femoral nerve is not one of them! The three structures are the femoral artery, the fascia lata and the fascia illiaca. So long as you inject leteral to the femoral artery and below the fascia iliaca (assuming your not injecting intramuscurally into the iliopsoas muscle!), the local anesthetic will fill the space between the fascia iliaca and iliopsoas muscle that will bathe the femoral nerves in its solution. With enough volume, it will spread to cover the obturator nerve (medial to femoral vein) and lateral femoral cutaneous (lateral to the femoral nerve) (aka 3-in-1 block).

Question 55

Femoral nerve vs adductor canal block

Answer 55

The adductor canal block has the advantage of producing less motor block (theoretically could be no motor block) as demonstrated with increased quadriceps strength and earlier mobilization. This is because the saphenous nerve is purely sensory. That being said, a large enough volume can ultimately end up blocking some motor nerves. With the femoral nerve block, both motor and sensory fibers are blocked indiscriminately. Pain control between the two groups appears to be equivocal and its effects on actual outcome, including reducing complications, has yet to be proven.

Question 56

TAP block and what it blocks

Answer 56

With adequate volume, T9-L1 is reliably blocked. Realize that with this block, one is only blocking the nerves that run through the transversus abdominis plane and ultimately coarse superficially to innervate the anterior abdominal wall and not deeper abdominal (visceral) structures. Both sides of the abdomen need to be blocked to achieve a reliable midline block.