LOCAL & REGIONAL ANESTHESIA

What are 2 indications for a Facial Nerve (CN VII) Block??

1. To relieve spastic contraction of facial muscles 2. To treat herpes zoster involvement of the facial nerve

What is the result of blocking each of the nerve fiber types?? (B, C, A-delta, A-gamma, A-beta, A-alpha)

"B": venodilation with hypotension "C" and "A-delta": Loss of pain & temperature "A-gamma": Loss of muscle tone "A-beta": Loss of motor function & proprioception "A-alpha": Loss of motor function & proprioception

What volume of LA per dermatone is injected and what LA can be used for lumbar epidural block?? Of the LAs used epidurally, which one produces the "most profound sensory block"??

1-2mL for each spinal segment (1mL per segment for shorter patients, 2mL per segment for taller patients) LAs used for epidurals... 2-Chloroprocaine Lidocaine Mepivacaine Bupivacaine (***Provides most profound Sensory Block) Ropivacaine Etidocaine

What volume of LA is injected for a 70kg adult male of average height for caudal block??

1-2mL of anesthetic per spinal segment....at least 12-15mL is required to adequately fill the sacral canal.

What are 4 complications of epidural anesthesia??....what is the most common?? How do these complications differ from those of SAB??

1. Backache (**most common...possibly d/t needle trauma, LA irritation, and ligamentous strain secondary to muscle relaxation are possible theories) 2. PDPH 3. Systemic LA Toxicity d/t intravascular injection 4. Total Spinal d/t accidental dural puncture...causing severe hypotension, respiratory arrest, and neurologic injury (rare) With Epidural Anesthesia, there is increased likelihood of intravascular injection adn systemic toxicity. The rate of "wet tap" for epidurals is as low as 1% (with a 27g pencil point needle in a non-OB patient) to as high as 20-50% (using a large Touhy in an OB patient). The lowest rate (of 1%) climbs to 34% for an OB patient, even with a 27g pencil-point needle....thus, "Wet Tap" rates are higher for OB patients and/or with large, epidural Touhy needles.

What are 3 situations in which Epinephrine should NOT be used in a Local Block??

1. Digital (toes/fingers) injection 2. Penile injection 3. Intra-ocular injection Epinephrine is not used for peripheral nerve blocks b/c of possible end-artery vasoconstriction and subsequent ischemia d/t lack of collateral circulation...other examples of sites that should not have Epi injected include the nose and ears.

What are 3 common complications associated with an Interscalene block of the brachial plexus??

1. HORNER'S SYNDROME, resulting from "Stellate" ganglion block (30-50% incidence) 2. RECURRENT LARYNGEAL NERVE BLOCK...results in hoarseness (30-50% incidence) 3. PHRENIC NERVE BLOCK (30-40% incidence....other sources report 23-100% rate)...leading to a "heaviness" on the ipsilateral chest (decreased ventilatory capacity) and sensation of dyspnea....can increase anxiety and the feeling that one cannot 'catch their breath'....this is the MOST COMMON complication/side effect of ISB. [NOTE: Phrenic Nerve Block can also occur with a Suprclavicular approach, but the rate of incidence is 40-60%]. 4. PNEUMOTHORAX...Besides blockade of the Phrenic nerve, Pulmonary function may also be affected by increased risk for pneumothorax, but even more increased in patients with COPD b/c of the superior displacement of the apex of the lung. If while doing an ISB, the patient experiences sudden cough and chest pain, then pneumothorax has probably occurred...less likely if US is used in addition to PNS. 5. INTRAVASCULAR INJECTION....resulting in systemic LA toxicity 6. TOTAL SPINAL ANESTHESIA....resulting in hypotension and respiratory impairment

What are 7 complications of Cervical Plexus Block??? Which 2 of these is most common???...which is 'least' common??

1. LA toxicity d/t rapid uptake or intravascular injection (e.g. convulsions, unconsciousness, hypotension) b/c the neck is highly vascular. 2. Phrenic Nerve Blockade 3. Recurrent Laryngeal Nerve Block (e.g. hoarseness) 4. Vagal Nerve Blockade (can cause dysphagia...difficulty swallowing) as well as hoareness (RLN) 5. Hematoma 6. Horner's Syndrome (blockade of Stellate ganglion) 7. Epidural or Subarachnoid injection (total/high spinal) The 2 most common complications of cervical plexus block is systemic toxicity (including hypotension) secondary to rapid uptake and/or intravascular injection....and Phrenic Nerve Block. The least common complication is Dysphagia caused by blockade of the Vagus Nerve.

Systemic Toxicity is BEST avoided by paying meticulous attention to detail & recognizing intravascular injection with a test dose....aspirating & monitoring for changes in HR. What are 10 s/sx of LA systemic toxicity in order of appearance?? What are some interventions & prophylactic measures to take if systemic toxicity is suspected (e.g. patient reports numbness of tongue or metallic taste)??

1. Numbness of tongue (circumoral numbness), metallic taste, apprehension 2. Auditory disturbance (ringing in the ears...tinnitus) 3. Skeletal muscle twitching 4. Systemic Hypotension (lightheadedness) 5. Myocardial depression 6. SZ 7. Unconsciousness 8. Respiratory Arrest (apnea) 9. Coma 10. CV depression Give 100% FiO2, hyperventilate the patient to produce hypocapnia and constrict cerebral vessels to reduce delivery of additional LA to the brain....and, respiratory alkalosis & hypokalemia associated with hyperventilation result in hyperpolarization of nerve membranes, which opposes the effects of LA. [NOTE: Hypocapnia increases the SZ threshold of LA]

What are 8 contraindications to IVRA (Bier Block)??

1. Patient Refusal (**Absolute C/I) 2. Moderate or severe hypertensive disease 3. Athletic build (strong muscles) 4. Skeletal muscle disorder 5. Known allergy (hypersensitivity) to Ester or Amide LA (**Absolute C/I) 6. Untreated Heart Block 7. Sickle Cell Disease or Sickle Cell Trait (dz in which prolonged tourniquet times are generally undesireable) 8. Tissue infection (e.g. cellulitis) [***Absolute C/I include patient refusal and allergy to LA] [NOTE: Tourniquet use in sickle cell patients is controversial (it is relatively C/I...NOT Absolutely C/I)...tourniquets may be used if it is critical to the success of the operation, but normothermia of the extremity must be maintained.]

What are 7 absolute contraindications to SAB??

1. Patient Refusal or is uncooperative 2. Infection at the injection site 3. High ICP (b/c SAB predisposes them to herniation) 4. Clotting defect or anticoagulation problem 5. Brain tumor 6. Spinal cord disease 7. Severe hypotension

What are the functions of each of the 5 nerves of the foot/ankle???

1. Saphenous nerve....supplies superficial sensation to the 'anteromedial' foot 2. Deep Peroneal nerve...permits 'Toe Extension' & sensation to the 'medial 1/2 and the dorsum (top) of foot' 3. Superifical Peroneal nerve....permits sensation superficially to the 'dorsum (top) of the foot & all 5 toes' 4. Posterior Tibial nerve....permits sensation to the 'heel, medial & lateral sole' of the foot 5. Sural nerve....provides sensation of the 'lateral' foot.

Aside from the obvious (e.g. placement of injection in epidural vs subarachnoid space), what are the 2 main differences between SAB and epidural anesthesia??

1. The onset of sympathectomy is slower with epidural, so likelihood of abrupt hypotension is less. 2. Sympathetic blockade is at the SAME level as the sensory block for an epidural.....and the motor block is 4 segments lower than a sensory block in an epidural. [Recall that the sympathetic block is 2-6 segments higher than sensory level with a SAB...and ...the motor block is only 2 segment levels lower than sensory block for a SAB.]

What are the 2 'amide' and 1 'ester' LA most commonly used for infiltration blocks??

2 Amide LAs: Lidocaine (0.5% to 1.0%) Bupivacaine (0.125% to 0.25%) 1 Ester LA: Procaine (0.5% to 1.0%)

What sensory nerves are anesthetized when topical anesthesia (such as LIDO) is applied to the nasal mucosa??

2 branches of the Trigeminal Nerve (CN V) 1. Anterior Ethmoidal nerve 2. Sphenopalatine (nasopalatine) nerves

What is the "3-in-1" Block??? ....what is it useful for???....what are potential disadvantages of this block???

A "3-in-1" Block is another name for the "Lumbar Plexus Block".....which anesthetizes the Femoral, Obturator, & Lateral Femoral Cutaneous nerves. The "3-in-1" Block is applicable for minor knee surgeries (e.g. knee scope), and in combinations with SAB, it is appropriate for major knee surgery. Potential Disadvantages of the "3-in-1" block include... 1. Large volumes of LA are required to achieve adequate spread along the fascial plane of the lumbar plexus 2. The "3-in-1" block often misses the obturator nerve 3. Quadriceps weakness may limit ambulation after the procedure

When placing an epidural, what should alert the provider to the fact that an intrathecal (SAB) injection has occurred???

A "Profound Motor Block and Sensory Block" (e.g. numbness in hands) soon after intended epidural injection should alert the provider than an intrathecal/ subarachnoid injection has actually occurred. The next s/sx suggesting SAB are associated with a "high spinal" or "total spinal anesthesia".... 1. Dyspnea caused by absence of proprioceptive input from afferent nerves of the abdominal and intercostal muscles. 2. Respiratory arrest if the block spreads to the cervical segments (C3-C5..."keep the diaprhagm alive") 3. If high level of LA reaches the brain, total neural paralysis leads to loss of consciousness, respiratory arrest, and hypotension.

A Sciatic nerve block can be useful for providing surgical anesthesia as well as post-op analgesia of the lower leg & foot...an alternative approach to the sciatic is via the popliteal fossa...with intent to block the sciatic nerve before it divides into the tibial and common peroneal nerves. What are the indications for a popliteal block???

A popliteal fossa nerve block is ideal for foot or ankle surgery, short saphenous vein stripping, and in the pediatric population....it improves calf tourniquet tolerance and an 'immobile' foot, compared to the ankle block. The sciatic branches into the Common Peroneal (Common Fibular) nerve...which divides further into the Deep & Superficial Peroneal nerves.....AND....into the Tibial nerve....which divides further into the Posterior Tibial and Sural nerves. All of these divisions of the sciatic nerve, along with the terminal branch of the femoral (the saphenous nerve) nerve for a sensory ankle block (infiltration).

Negative pressure during a caudal anesthetic is detectable after going through the Sacrococcygeal ligament (an extension of the ligamentum flavum) of the sacral hiatus. How far should the needle be advanced into the epidural space during a caudal block??...and what needle gauge is used??

After Loss of resistance (LOR), the needle is advanced 1-1.5cm or 1-2cm (depends on source) using a 22g or larger needle. After placement, aspiration should be performed and a test dose injected to determine if the needle is in the caudal canal. A test dose of 5mL of Preservative Free NS is given quickly while the free hand is used to palpate across the dorsal sacral region. If the needle is located subcutaneously, a bulge will be felt over the canal, no midline bulge should be palpable. The test dose for pediatrics should contain 0.5mcg/kg body weight of epinephrine (0.1 mL/kg of a 1:200,000 solution)

The Ulnar nerve passes distally through the axilla, medial to the distal artery and the brachial artery, until the middle of the arm. Before passing to the forearm, the Ulnar nerve pierces the medial intermuscular septum and descends in the groove between what 2 structures??

At the middle of the arm, the Ulnar nerve pierces through the medial intermuscular septum and descends in the groove between the "Medial Epicondyle of the Humerus" and the "Olecranon Process of the Ulna".

The patient is being Positive Pressure Ventilated....what regional nerve block must you avoid in this patient???

Avoid an Interpleural Block in a patient who is being Positive Pressure Ventilated.

When LA is injected into a nerve, there is intense, searing pain, which is a signal to immediately withdraw the needle. The incidence of needle-induced nerve injury is greatest with which of the following regional techniques.....Bier block, epidural, SAB, or axillary block???

Axillary block appears to be associated with the highest incidence of nerve damage...at a rate of 0.8% when the axillary is used as the landmark & 2.8% when paresthesias are actively sought. The incidence of neurologic sequelae for SAB and epidural is 0.01% (1 in 10,000)....and nerve injury is not reported with Bier block.

What is the most frequent complaint after a Celiac plexus block???

Backache or Back pain

Blockade to which spinal segments will take away urinary bladder tone and inhibit the reflex to void??

Blockade of lower lumbar and sacral spinal segments (S2-S4) will take away urinary bladder tone and inhibit the reflex to void.

What muscles of the forearm & and what areas of the hand does the Median Nerve supply.....and how is function of the median nerve assessed???

Branches of the Median Nerve in the Forearm innervate the following muscles... Pronator teres Flexor carpi radialis Palmaris longus Flexor digitorum superficialis The Median Nerve provides sensory innervation to the thumb, index finger, middle finger, and lateral ring finger.

Epidural administration of what combination of LA and opioid is effective for post-op pain control and yet permits the patient to ambulate??

Bupivacaine (0.0625 - 0.125%) in combination with Morphine (0.1mg/mL...100mcg/mL) or Fentanyl (5mcg/mL) provides excellent analgesia without motor blockade.

What 5 nerve roots form the brachial plexus in 'most' people???

C5, C6, C7, C8 & T1.....sometimes there are contributions from C4 and T2.

What is "Cauda Equina Syndrome"??....and what is the major contributing factor to Cauda Equina Syndrome???.....What are 3 s/sx of this syndrome???

CAUDA EQUINA SYNDROME....a serious injury to the cauda equina nerve roots....exposure of the cauda equina nerve roots to a high concentration of LA appears to be the common denominator underlying the onset of this problem. Maldistribution of the injected LA permist exposure of some nerves to high concentrations of LA as a result of a failure of mixture upon injection. Administration of continuous or repeated doses through small-bore catheters also appears to be a common cause. 3 s/sx of Cauda Equina Syndrome includes.... 1. Urinary and Fecal Incontinence 2. Partial paralysis of the LEs (paresis) 3. Diminished sensations of the perineum (perineal hypoesthesias)

What nerve may be blocked by injection of LA at the base of the tonsillar pillars??

CN IX (Glossopharyngeal Nerve) may be blocked by injecting LA 5mL intra-orally at the base of each tonsillar pillar....a 22g 9cm needle is used...be sure to aspirate before injecting b/c of the proximity of the carotid artery to the glossopharyngeal nerve.

The patient with chronic low back pain is scheduled for a lumbar facet block. What are possible complications of lumbar facet injection of LA??

Complications of Facet Block (lumbar or thoracic) with LA are rare, but include....Infection, Allergic reaction, & Transient radicular pain. Of greatest concern is the possiblility of entering the Subarachnoid Space during Facet Block & depositing LA, resulting in a Spinal Block.

What are 6 complications of SAB???....which are the 2 most common???

Complications of SAB include.... 1. PDPH (**2nd most common, 0.4-7.8% incidence) 2. Backache (**Most Common 11-13% incidence) 3. High spinal 4. Nausea 5. Urinary retention 6. Neurologic Injury (rare) [NOTE: Diplopia following accidental 'wet tap' results from paralysis of the Abducens Nerve (CN VI)...it is presumed to be d/t traction on the Abducens Nerve, secondary to loss of CSF through the dural hole.] Backache (most common complication of both SAB & Epidural) most commonly occurs after procedures in which there is flattening of the normal lumbar curvature owing to 'relaxation of the paraspinous muscles allowing for stretch of the joint capsules and spinous ligaments'.

Damage to what nerve causes an inability to "ADDUCT" the thumb?? Damage to what nerve causes an inability to "ABDUCT" the thumb??

Damage to the MEDIAN nerve causes an inability to ADDUCT the thumb. Damage to the RADIAL nerve causes an inability to ABDUCT the thumb.

SAB is administered and the patient reports tingling in the little finger of bilateral hands...what is the level of the block??

Dermatone charts show that sensory block is at the C8 level if the little finger and ring finger have abnormal sensation. Sensory block at C6 results in paresthesia of the thumb and index finger. Sensory block of C7 results in paresthesia of the middle fingers.

The anesthetic level reached after SAB is determined by what 4 factors??? Which of these factors most influences the level of block achieved with a hyperbaric spinal??

Distribution of LA solution in CSF is principally influenced by.... 1. Baricity of solution 2. Concentration (increasing concentration will increase spread) 3. Contour of the spinal canal 4. Position of the patient in first few minutes after injection....***This is the most influential factor for spread of a hyperbaric spinal.....since a hyperbaric solution is heavier than CSF, it "settles" to the dependent aspect of the subarachnoid space, which is determined by position.

EMLA (Eutectic Mixture of Local Anesthetics...the melting point of the combined contents is lower than the individual agents themselves) cream is able to diffuse through the keratinized layer of intact skin to block neuronal transmission from dermal sensory receptors and is used for topical anesthesia of skin. EMLA cream is useful for venipuncture & arterial cannulation, skin graft harvesting, arterivenous shunt procedures, and lumbar punctures. What is the recommended dose, the contents of EMLA cream, and considerations that should be taken when using EMLA cream??

EMLA Dose: 1. For minor dermal procedures... 2.5gm over a 20-25 square cm surface for 60 minutes before the procedure. 2. For painful procedures...2gm cream per 10 square cm of skin is applied and left in place for 2 hours. EMLA (5%) is made up of 2.5% Lidocaine and 2.5% Prilocaine....the Prilocaine increases concern for the risk of Methemoglobinemia, which may occur in Children < 3-12 months old (b/c of immature reductase pathways)....the RBCs contain methemoglobin reductase that normally reduces Ferric (Fe+++) iron to Ferrous (Fe++..."normal") iron....thus concurrent administration of EMLA with other oxidizing agents (e.g. Sulfonamides, Acetaminophen, Benzocaine, Phenytoin, NTG, SNP) may overload the immature reductases in the child <3-12 months old.

What are 4 contraindications to the use of EMLA cream??

EMLA is NOT recommended for.... 1. Use on mucous membranes 2. Use on Skin wounds 3. Use in patients being treated with anti-dysrhythmic agent Mexiletine 4. Use in patients with known hx/o allergy to Amide LAs (b/c it contains Lidocaine and Prilocaine)

An Interscalene Block can be used for any procedure in the upper extremity, including the shoulder (distal clavicle vs proximal...may require supplementation with a Superficial Cervical Plexus block), but is used most often for procedures on the arm and forearm & when the arm cannot be positioned for the axillary approach. What nerve is often NOT blocked ("is missed") in an Interscalene approach to a Brachial Plexus block??

Even with Large volumes of LA (30-40mL) the LOWER ("Inferior") TRUNK (C8-T1) of the Brachial Plexus may be inadequately anesthetized.....Since the ULNAR Nerve arises from the Lower (INFERIOR) Trunk, supplemental Ulnar nerve block may be required for adequate surgical asnesthesia in that distribution. An ISB would NOT be appropriate for hand surgery....rather, a Supraclavicular, Infraclavicular, Axillary, or even a Bier Block would be a better option...recall that some of the Ulnar nerve may be missed with an ISB.

What nerve causes 'flexion' of the foot???....and foot 'extension'???

Foot FLEXION....the 'medial & lateral plantar' nerve branches (terminal nerve branches of the Tibial nerve) Foot EXTENSION...the 'Peroneal nerve'

Into what space is LA injected for Caudal anesthesia???....and what single factor most determines the height of a caudal anesthetic?? What are the landmarks for placing Caudal Anesthesia??

For Caudal anesthesia, LA is injected into the epidural space.....the extent of the caudal anesthesia is largely determined by the volume of LA injected. Caudal anesthesia (a form of epidural anesthesia) injection is made at the Sacral Hiatus, which usually lies 5cm above the tip of the coccyx and directly beneath the uppermost limit of the natal cleft. The 2 sacral cornu lie on either side of the sacral hiatus and cephalad to the coccyx. Direct palpation of the depression between the sacral cornu is the best method to locate the sacral hiatus.

What cutaneous sensory level should be reached with a Neuraxial RA block to provide adequate analgesia for cystoscopic procedure??....and for uterine surgery???

For Cystoscopic procedures, a cutaneous sensory block to T10 should provide adequate analgesia. For vaginal & uterine procedures, a cutaneous sensory block to T8-T10 should provide adequate analgesia. Refer to table in Mass. Gen. p232t ....or "Baby Miller" p175

What dermatone level would be required for "Lower" abdominal surgery??....or for "upper" abdominal surgery??

For LOWER abdominal surgery, blockade to T6....and For UPPER abdominal surgery, blockade to T4 is needed.

The "clinical progression" of differential nerve block....from first blocked to last to be blocked....is: Autonomic Fibers (first) Sensory Fibers Motor Fibers (last) What is the order of nerve fiber blockade (based upon nerve type...B, C, etc.) during a SAB?? What sensations are lost first after SAB injection?? What nerves are "least" likely to be blocked during SAB??

For a SAB, the order of nerve blockade is.... 1. B Fibers 2. C & A-delta 3. A-gamma 4. A-beta 5. A-alpha [NOTE:...know that B fibers are blocked first, A-alpha are blocked last.] The first sensations to be lost are Pain & Temperature which are carried by "C" & "A-delta" fibers. [Recall that B fibers are blocked first, but the response is venodilation and hypotension....thus 'sensation' is not lost]. The "A-alpha" fibers are the most difficult (motor) to block....then "A-beta"....and then "A-gamma" fibers. The "B" fibers are the easiest to block.

The surgical procedure requires a tourniquet on the Lower extremity....what is the minimum sensory level required for 'cutaneous' anesthesia in this case??

For a procedure requiring a tourniquet on the LE, a minimum sensory level blockade of T8 is required for adequate cutaneous anesthesia.....[However, Nagelhout states..."high-quality block of sacral roots is more important than thoracic level"...].

What 2 lab values should you obtain before placing an epidural??....and what other labs may be necessary & why??

HCT and PT are a must.....but the PTT is warranted if there is any suggestion that a coagulation abnormality exists. Bleeding time (BT) should also be assessed if the patient is taking anti-PLT drugs (ASA, NSAIDs, Valproic acid).

What syndrome is associated with Stellate Ganglion Blockade???.....what are the 6 s/sx of this syndrome??? What bracheal plexus block is 'least' likely to cause this syndrome???

HORNER's Syndrome is associated with STELLATE GANGLION Blockade.....on the (same side as the block) Ipsilateral side of the head/face there is.... 1. Ptosis (droopy eyelid) 2. Miosis 3. Facial & Arm Flushing (d/t vasodilation) 4. Increased Skin Temperature 5. Anhydrosis (Lack of Sweating on Face) 6. Nasal Congestion Horner's Syndrome is caused by blockade of the stellate ganglion which is located at the lateral border of the vertebral body of C7....therefore, b/c of this anatomic location, the AXILLARY approach would be 'least' likely to cause stellate ganglion blockade (i.e. Horner's Syndrome).

How does the half-life of a LA given via SAB compare with the half-life when administered epidurally???

Half-life is the time it takes for the amount of drug in the body to fall by 1/2.....the site of injection from which the LA washes out the fastest will be the site which gives the drug the shortest half-life....hence, the half-life of a LA is longer when injected intrathecally compared with epidurally.

What are the 2 most common physiologic changes associated with SAB??

Hypotension & Bradycardia Venodilation leads to a decrease in CO. Sympathetic blockade causes venodilation and venous pooling, with subsequent decrease in VR (preload), decreased CO, and decreased arterial BP. During SAB, the SVR is only slightly decreased. With high spinal blockade (T1-T4), bradycardia can contribute to the hypotension.

As fluid is aspirated after placement of the needle for SAB, blood-tinged CSF appears and is followed by clear CSF...what should you do?? If blood-tinged CSF continues to flow, what should you do??

If blood-tinged CSF is followed by clear CSF, then "proceed" with the SAB....the blood probably was derived from tissue damage during needle insertion. However, if blood-tinged CSF continues to flow, then "Remove the needle & Reinsert it at a different interspace". [**IF blood-tinged CSF is seen in a different interspace and persists, then "Terminate the attempt to place SAB" and further evaluate the patient].

An epidural catheter is placed & LA is administered. Sensory block is achieved on only one side of the body. What should you do??

If the block is markedly asymmetric, 'replacement of the epidural catheter to a more "rostral" (headward) space is required'. The catheter is not in the epidural space. It may be located in the "SUBDURAL" space (a potential space located between the dura and arachnoid mater).

How far is the epidural space (in cm) from the skin in the non-obese patient???....in the obese patient???....the thin patient?? How far should the epidural catheter be safely threaded into the epidural space???

In 50% of the population, the epidural space is ~4cm from the skin....and 80% of the population is 4-6cm from the skin. However, in obese patients, this distance may be greater than 8cm...and in thin patients the distance may be as low as 3cm. The catheter should be advanced 3-5cm into the epidural space (4cm is a good answer).

The Femoral Nerve Block (FNB) provides analgesia/anesthesia for both deep & superficial surgical procedures to the 'anterior thigh & knee'....in fact, the FNB alone is sufficient for ACL repair, & is an excellent adjunct to GA for knee joint surgery. In addition to the Femoral nerve, what 3 other nerves may be blocked for surgery on or above the knee???

In addition to the Femoral nerve, the following nerves may also provide complete coverage above and at the knee when blocked....the Sciatic nerve....the Lateral Femoral Cutaneous nerve...the Obturator nerve.

What are the landmarks & relative needle location in order to perform a Median nerve block at the wrist??

In order to perform a Median Nerve block at the wrist, a 22g needle is directed just medial to the Ulnar artery pulse, or...if the ulnar artery is not palpable, then the needle is placed just medial to the flexor carpi radialis muscle....a total volume of 3-5mL of anesthetic is injected to block the Median nerve.

There are 4 nerve block approaches to the brachial plexus...Interscalene, Supraclavicular, Infraclavicular and Axillary. What are the anatomic relationships of the Median, Ulnar and Radial nerves to the Axillary Artery?? Of these, which nerve is most commonly blocked with a 'transarterial' approach to an axillary block??

In relation to the Axillary Artery.... The MEDIAN nerve lies ANTERIOR (Superior) The ULNAR nerve lies MEDIAL & slightly POSTERIOR (inferior) The RADIAL nerve lies POSTERIOR & slightly LATERAL [NOTE:....a mnemonic is "RUMM --> PISS" The RADIAL Nerve is most commonly blocked via transarterial technique.

What are indications for a Supraclavicular block....& what are the major advantages for this block?? What are the indications for an axillary block??

Indications for a Supraclavicular block.....it is used for procedures on the distal upper arm, as well as an arm block with a high success rate for hand surgery in patients who cannot 'circumduct' the humerus for the axillary approach. It 'may' be possible to use this for a shoulder procedure. The major advantage of the Supraclavicular block is that this block approaches the brachial plexus where it is "most compactly" arranged (at the level of the Trunks), where there is 'minimal possibility of missing peripheral or proximal nerve branches' b/c of failure of LA to spread. The axillary block can be used for any surgery from the 'mid-humerus' to the hand....but NOT for a shoulder procedure

After diagnosis of PDPH is confirmed, what is the treatment??

Initial Therapy:... 1. Analgesics 2. Bed Rest (low stimulus environment) 3. Hydration (IVF) Additional actions include.... 4. Epidural Blood Patch (if PDPH persists for more than 14 hours of the above treatment using injection of 10-20mL of autologous blood with MAX of 20mL) should help resolve the PDPH within 24-48 hours. Leave supine x1-2 hours before ambulating....offers 90-95% success rate on 1st attempt....99% on second attempt. 5. IV Caffeine (500mg Caffeine Sodium Benzoate in 1L D5LR)

A line drawn between the left and right iliac crest crosses the spine of what lumbar vertebra??

L-4 SAB is usually injected between L3/L4 or L4/L5 vertebral interspaces....the spinal cord is not in danger of needle trauma when LA is injected below the conus medullaris, which usually ends at L1/L2 in adults.

Where do LAs work after epidural administration, and after an epidural is given, what is the first sign that it is working...how is epidural blockade assessed??

LA is found in spinal nerve roots within the epidural space...the spinal nerve rootlets bathed in CSF....and within the spinal cord. Sensory analgesia is usually the first indication of successful epidural blockade. Sensory block is tested by assessing via pinprick sensations at each dermatone level on both sides of the body.....pinprick assesses analgesia.....Alcohol swab assesses sensation of temperature, and is the 'most sensitive' indicator of the "INITIAL" sensory block. [NOTE: With epidural, sympathetic blockade occurs at the "same" level as the sensory block.....and motor block may be 4 dermatones lower than the sensory block].

How is a hypobaric LA solution prepared?? How is an isobaric LA solution and a hyperbaric LA solution prepared???

LA is mixed with.... 1. Sterile Water to make Hypobaric solution 2. CSF or commercially prepared solution to make Isobaric solution 3. Dextrose to make Hyperbaric solution

Which LAs (and % concentration of each) produce minimal motor blockade when given via epidural?? .....and which LAs (& % concentration) produces a dense/intense motor blockade??

LAs that produce 'MINIMAL' Motor Blockade... 1. Lidocaine (1%) 2. Mepivacaine (1%) 3. Bupivacaine (0.25%) LAs that produce 'INTENSE/ DENSE' Motor Blockade... 1. Chloroprocaine (3%) 2. Lidocaine (2%) 3. Mepivacaine (2-3%) 4. Etidocaine (1.5%) 5. Prilocaine (3%)

Drugs that have Alpha-1 agonist properties (phenylephrine or epinephrine) are injected with LAs to prolong their action by producing vasoconstriction, which slows the washout of LA from the injection site. What is the duration of action of Lidocaine used for SAB with and without epinephrine??

LIDO without Epi for SAB lasts 45-60 minutes LIDO With Epi for SAB lasts 60-90 minutes [NOTE: For patients with CAD who have had an epidural, Phenylephrine (alpha-1 agonist) migt be a more appropriate choice. Absorbed phenylephrine will not directly stimulate the heart....in contrast, if epinphrine (an alpha & beta agonist) were given, then beta-1 stimulation of the heart may occur]

If during an IVRA block (Bier Block), the tourniquet becomes incompetent and the patient develops SZs, what is the first thing that should be done??

Leakage of LA into systemic circulation before tourniquet release may occur...and with rapid entry of LA into circulation, a SZ may develop. (may also occur if the tourniquet is released too fast...thus, intermittent/slow release & reinflation of the tourniquet may help decrease risks of SZ). Treatment of CNS toxicity consists initially maintaining a patent airway and assisting ventilation of the lungs with 100% FIO2....LA-induced SZs are usually of short duration.

What is the maximum & minimum time that a tourniquet should be inflated after a Bier Block??

MAX Time of 2 hours....any damage to vessels, nerves, & skeletal muscle is usually reversible for tourniquet inflations of 1-2 hours. MINIMUM Time of 25 minutes (20-40 minutes in Barash)

What nerve is damaged by an IV needle in the antecubital fossa??

Median Nerve

What is the onset time of effect of "plain" LIDO for epidural anesthesia....and what is the duration of action of LIDO plain & LIDO with Epi??

Onset of sensory analgesia of LIDO (plain) is 5-15 minutes Duration of sensory blockade by LIDO (plain) is 80-120 minutes.....and by LIDO with Epi is 120-180 minutes.

Post-dural Puncture Headache (PDPH) is the 2nd most common complication of SAB, and is due to decreased CSF pressure resulting from CSF leakage through the opening in the dural sheath. What 5 factors increase the likelihood of developing PDPH after a "wet tap"??

PDPH occurs more frequently... 1. In younger patients (compared to older) 2. Females > Males 3. Larger needle sizes (compared to smaller ones)...incidence of PDPH is up to 18% with a 16g needle 4. Pregnancy > Non-pregnant 5. Patients with a hx/o multiple punctures [NOTE: In a pregnant patient who is receiving an epidural with a 17g or 18g Touhy needle that results in an unintentional 'wet tap', the incidence of PDPH is as high as 70-80%. In younger patients, PDPH incidence may be as high as 50% when accidental 'wet tap' occurs].

What approach to the brachial plexus is associated with the greatest risk of pneumothorax (although rare)??....and least risk???

Pneumothorax occurs more frequently with the Supraclavicular Block.....(and potentially also with Interscalene). Pneumothorax occurs 'less' frequently with the Axillary block. [NOTE: There is a 'potential' risk for pneumothorax with the Infraclavicular block]

What 2 nerves are derived from the "posterior cord" of the brachial plexus....from the "lateral cord".....and from the "medial cord" of the bracheal plexus???

Posterior Cord gives rise to the Axillary & Radial Nerves Lateral Cord gives rise to the Musculocutaneous & Median Nerves Medial Cord gives rise to the Median & Ulnar Nerves

Plasma concentration achieved after administration of LA transtracheally most closely resembles plasma concentration achieved after injection Sublingually...in both, LA is absorbed via mucous membranes, where drugs are rapidly absorbed (almost as rapid as if given IV). How is proper position of a needle confirmed for transtracheal block??....how is this block done??

Proper position of the needle is confirmed by aspiration of air prior to injection of LA. Transtracheal block produces topical anesthesia below the vocal cords & down the trachea (blocking the RLN) and is done with Plain LIDO (4mL of 4% LIDO) through the cricothyroid membrane using a 22g needle attached to a small syringe....LIDO is sprayed into the trachea at "END-EXPIRATION"...or during "INSPIRATION" (depending upon the source). The needle is quickly withdrawn after injection, since the patient will begin to cough...the coughing spreads the LA over the surface of the trachea and the inferior surface of the vocal cords.

The 5 factors that are considered for choosing a particular LA include... 1. Duration of surgery 2. Regional Technique/approach selected 3. Needs of the particular surgery (e.g. sensory block for OB, motor block for orthopedics) 4. Skills of the anesthetist 5. Potential for systemic toxicity Rank the following LA injection sites from "fastest/greatest" absorption to "slowest/least" absorption ...bracheal plexus, caudal, lumbar epidural, intercostal, paracervical, subcutaneous.

Rate of absorption depends upon blood flow to the tissue at the injection site....Thus, sites of injection having greatest absorption to least absorption are ranked as...(from greatest to least absorption): Intercostal (greatest) > Caudal > Paracervical > Lumbar epidural > Brachial Plexus > Sciatic > Subcutaneous [NOTE: Inactive skeletal muscle injection (IM) absorption is probably relatively slow compared to 'active' skeletal muscle...such as intercostal muscles active in respiration]

Upon aspiration after placement of the needle into the epidural space, blood-tinged fluid is seen first, and then clear fluid is obtained. What action should be taken??

Re-insert the needle at the same interspace, but at a slightly different angle...if this happens again, and blood-tinged fluid is aspirated, then a new interspace should be chosen....but note that aspiration of blood-tinged fluid does NOT necessarily mean venous cannulation.

A "HIGH SPINAL" is a term used to describe an undesired excessive level of sensory and motor block....and is associated with difficulty breathing or apnea, leading to hypoxemia and hypercarbia. A "TOTAL SPINAL" is anesthesia to the Cervical spinal cord, cranial nerves and brainstem. What are s/sx of High or Total Spinal anesthesia??

S/sx of High/ total spinal include... 1. Dyspnea (common) 2. Hypotension 3. Nausea/ Vomiting 4. Apnea (reflects ischemia to brainstem medullary respiratory centers secondary to profound hypotension) Hypotension can be the cause of sudden N/V. Moderate Hypotension during SAB can be treated with 300-500mL bolus of IVF or Ephedrine....also Trendelenbug's position may help if hypotension is severe.

What effect does SAB have on the intestines???...why??

SAB above T5 inhibits SNS innervation of the GI tract, which results in contracted intestines and relaxed sphincters and increased peristalsis....b/c the PNS is left unopposed.

Assessment of a SAB should begin ~5 minutes after injection. The adequacy of blockade is assessed by inability to raise the leg...which is a good indicator of motor block in the lumbar dermatones. For sensory block, a dull needle is used, starting at the operative site and advancing cephalad until a 'sharp' sensation is elicited...equal to a higher unanesthetized area to use as a comparison (e.g. C4) The dermatone immediately caudad to the dermatone that elicited a sharp sensation represents the highest level of anesthesia. How long does it take for SAB to reach its highest (most cephalad) level??....what is the significance of this??

SAB usually reaches its highest level 20 minutes after injection, although the level may move cephalad for 30 minutes.....knowing when analgesia reaches its highest (most cephalad) level is significant b/c if the level of analgesia is above T5, then the probability of hypotension and bradycardia increase.

During an epidural placement, the patient's BP drops precipitously to 80/35, the HR falls to 50bpm, and SaO2 falls to 85%....what has probably happened??

Severe hypotension, bradycardia & respiratory insufficiency during an epidural are s/sx of "Subdural" injection....these are same s/sx as when a 'high spinal' occurs, meaning a sympathetic block with unopposed PNS effects. Possible s/sx of subdural injection include... 1. Severe hypotension 2. Bradycardia 3. Respiratory insufficiency 4. "Patchy" & marked asymmetric extensive spread of analgesia.

The epidural needle must traverse through the skin, subcutaneous tissue, supraspinous and interspinous ligament, and ligamentum flavum for the midline approach. What structures are passed through when placing an epidural with the Paramedian approach??? Why is there less resistance with the Paramedian approach to epidural or spinal anesthesia???

Skin, subcutaneous tissue, paraspinous muscle mass and ligamentum flavum. The Paramedian approach is lateral to the supraspinous and interspinous ligaments....thus, there is less resistance.

In preparation to do an Axillary block, why would you do a 'subcutaneous' infiltration???

Subcutaneous infiltration in preparation for an axillary block is performed... 1. To block the Intercostobrachial Nerve (T-2 Branch) in order to provide anesthesia for the tourniquet 2. To block the Medial Brachial Cutaneous Nerve, which leaves the sheath just below the clavicle. BOTH of these nerves innervate the medial aspect of the upper arm down to the elbow....and the Medial Cutaneous nerve continues innervation down the medial aspect of the forearm (from slightly above the elbow down to the wrist)....blockade of the Medial Brachial Cutaneous nerve of the arm after axillary block may lead to a feeling of "fullness" on the medial aspect of the upper arm.

List 4 surgical & 3 non-surgical indications for Intercostal Nerve Block??

Surgical Indications for Intercostal Nerve Block include...superficial procedures of the upper abdomen & thorax...such as 1. Insertion of throacotomy & Gastrostomy tubes 2. Minor breast surgery 3. Extracorporeal Lithotripsy 4. Cardiac pacemaker insertion NON-Surgical indications for Intercostal Nerve Block include to provide relief from.... 1. Fractured rib pain 2. Pleuritic pain 3. Herpes Zoster ("Shingles") pain

Thoracic Outlet Syndrome....results from compression of the brachial plexus and subclavian artery at the thoracic outlet between the 1st rib and the clavicle...or between the anterior & middle scalene muscles. What are possible surgical interventions for Thoracic Outlet Syndrome??....and what are 6 possible complications of this procedure???

Surgical approaches to Thoracic Outlet Syndrome include.... Resection of the 1st rib Resection of a 'cervical rib' Partial resection of the scalene muscles Removal of anomalous fibrous bands Complications of the above surgical interventions to treat Thoracic Outlet Syndrome include.... 1. Pneumothorax 2. Brachial Neuralgia 3. Pleural fusion 4. Temporal Phrenic Nerve Palsy 5. Injury to the Subclavian Artery 6. Injury to the Long Thoracic Nerve & T1 Roots.

The most frequent cause of systemic toxicity of LA is an excess of plasma concentration of LA from "accidental intravascular injection". What are 4 determinants of systemic absorption??

Systemic absorption of LA is determined by... 1. Total Dose of LA administered 2. Vascularity of the injection site 3. Presence of Epi or Phenylephrine (vasoconstrictor) in the LA solution 4. Physiochemical properties of the drug (the greater the protein binding & the greater the lipid solubility, the slower the absorption).

The mechanism(s) of differential block of sensory and motor nerve fibers by LAs is a controversial topic....what is the "clinical progression" of fiber block??? ....and what are 6 mechanisms that contribute to the differential block produced by LAs???

The "clinical progression" of differential nerve block....from first blocked to last to be blocked....is: 1. Autonomic Fibers (first)...sympathetic blockade occurs 2-6 segments higher than sensory block. 2. Sensory Fibers 3. Motor Fibers (last)...motor block occurs 2-3 segments lower than sensory block. 6 different factors contribute to differential nerve block by LAs.... 1. The anatomic & geometric arrangement of the individual fibers in a nerve bundle (core vs mantle) 2. The size (diameter) of the nerve fibers 3. The inherent impulse activity (firing rate/frequency) of the individual nerve fibers 4. The variability in longitudinal spread of agent along the nerve fibers 5. The effects on ion channels "other than the Na+ channel" 6. Choice of LA Sensory nerve fibers fire more often than motor fibers...this may explain to a large extent why sensory fibers are blocked before motor nerve fibers.

What reflex best explains bradycardia during SAB??

The BAINBRIDGE Reflex....relates to the characteristic but paradoxical slowing of the HR seen with SAB.... [Normally, the mechanism for bradycardia with SAB is blockade of sympathetic pre-ganglionic efferents from T1-T4 (cardioaccelerator fibers) with subsequent unopposed parasympathetic stimulation (e.g. bradycardia). However, bradycardia during SAB is more clearly r/t the development of arterial hypotension than to the height of the block.] The primary deficiency in the development of spinal hypotension is a "Decreased VR"....which is sensed by 'low pressure venous baroreceptors', resulting in a reflex bradycardia.

Which segment of the brachial plexus is targeted in the Interscalene block?? (cords, branches, trunks, etc.)

The Interscalene Block (ISB) targets the TRUNKS of the brachial plexus....after roots emerge from the cervical & thoracic vertebrae (C5-T1), the trunks are sandwiched between the anterior and middle scalene muscles. 2 sheathes of fibrous tissue enclose the trunks between the scalene muscles, forming the space into which the LA can be injected to produce the brachial plexus block. [NOTE: Mnemonic to recall the order of brachial plexus segments from the spinal cord to the periphery is.... "Robert Taylor Drinks Cold Beer"....representing the order of ....Roots, Trunks, Divisions, Cords, Branches. Roots = Interscalene block Trunks = Supraclavicular block Cords = Infraclavicular block Branches = Axillary block

Where is the largest interlaminar interspace of the vertebral column found??....the approach using this interspace to the subarachnoid (intrathecal) compartment is a variation of what approach???

The L5-S1 interspace is the largest "interlaminar" interspace of the vertebral column. The "LUMBROSACRAL" approach to the subarachnoid space is a variation of the Paramedian Approach.

What nerve is least likely to be blocked with an Axillary approach to the Brachial Plexus??

The Musculocutaneous Nerve b/c within the axilla, this nerve has already left the fascial sheath and lies within the coracobrachialis muscle, therefore, requires separate infiltration of LA to block this nerve. The Musculocutaneous Nerve provides sensory innervation to the LATERAL aspect of the Forearm...and the terminal sensory limit (branch) of the musculocutaneous nerve on the Lateral aspect of the forearm is the Lateral Cutaneous Nerve of the forearm.

What areas of the UE does the Radial Nerve supply sensory innervation??

The Radial nerve provides sensory innervation to the Dorsum (back) of the hand, covering the width of the first 2 1/2 digits (thumb, index finger, and lateral 1/2 of the middle finger)....the unique sensory area served by the radial nerve is the "Web-space between the Thumb and the index finger".

What the sensory innervation does the Ulnar Nerve provide in the UE....and how is function of the Ulnar nerve assessed?? What muscles are innervated by the Ulnar Nerve??

The Ulnar nerve provides sensory innervation to the Little finger (5th) and the medial ring finger. The Ulnar nerve function is assessed by checking for normal sensation of the palmar surface of the 5th finger (little finger). The Ulnar Nerve innervates the following muscles.... (In the Forearm): Flexor Carpi Ulnaris & the medial 1/2 of the Flexor Digitorum Profundus. (In the Hand): Palmaris Brevis, the 3 short muscles of the Hypothenar Eminence (Abductor digiti minimi, Flexor digiti minimi, & Opponens digiti minimi), the ADDUCTOR POLLICIS, the 3rd and 4th Lumbricals, & all the Interossei. [NOTE: The ADDUCTOR POLLICIS muscle of the thumb is innervated 'solely' by the Ulnar nerve]

Which nerves are blocked in a Cervical Plexus block?? What are indications for Superficial Cervical Plexus block??

The VENTRAL RAMI of C1-C4 form the Cervical Plexus....however, the first cervical nerve (C1) is "motor" nerve with NO sensory distribution, thus Both Deep & Superficial Cervical Plexus blocks anesthetize C2-C4. (Deep Cervical Plexus block essentially is a paracervical block of C2-C4) The Superficial Cervical Plexus Block is performed for "Unilateral" procedures on the Anterior or Lateral neck such as CEA or Thyroidectomy, and as adjunct to shoulder surgery under ISB.

At what angle is the epidural needle inserted for placement of lumbar vs thoracic epidural??

The epidural needle in the Lumbar region is introduced at a Right (90*) angle....and in the thoracic region, the needle is introduced at a 40* angle to the ligamentum flavum.

What level of spinal block would be appropriate for a patient in kidney pain?? What about for a TURP or for testicular surgery??

The kidneys receive sensory innervation from the spinal levels T10-L1/L2....thus a blockade to T10-L1 is usually sufficient for referred kidney pain. For a TURP, a sensory blockade of T10 is needed, and for Testicular surgery, a T10 sensory block is necessary.

What is the highest curve of the spinal column in the 'supine' position??

The highest curve of the spinal column in the supine position is at the apex of the Lumbar Curve (L3-L4).

What is the hydrostatic pressure in the epidural space....what is the significance??? What is the "hanging drop method??

The hydrostatic pressure in the epidural space is NEGATIVE ("subatmospheric") which means that a drop of fluid placed in the hub of a needle with its tip in the epidural space will be 'sucked in'. The Negative Pressure or "Hanging Drop" Method is accomplished by placement of a drop of saline or LA solution in the hub of an epidural needle once the needle is located into the interspinous ligament....if the needle is carefully advanced through the ligamentum flavum into the epidural space, the drop is 'sucked' into the epidural space by the 'negative/ subatmospheric' pressure in the epidural space.

There are 2 reasons for doing a test dose epidurally....The Test Dose is given to determine that the injection is neither intravascular nor intrathecal. The waiting period for an epidural test dose is 3-5 minutes. How long does it take a test dose of epinephrine to reach the heart after intravascular injection during epidural placement??? ....and is this test dose technique reliable in the parturient??

The intravascular injection of a LA with Epi consistently increases the HR 20-30 bpm (along with circumoral pallor, palpitations, & tremulousness) within 30-60 seconds & may last from 15-40 seconds, if there is an intravascular injection.....However, IN THE PARTURIENT, this test dose technique to assess for unintentional intravascular injection is NOT reliable. The effects of an intrathecal injection may not be apparent for 3-5 minutes....thus you should wait for at least 3-5 minutes after giving a test dose before you determine whether or not it was injected intrathecally.

How is baricity of LA determined?? What is the Specific Gravity of CSF....and of hypobaric & hyperbaric solutions???

The measure of Baricity is "Specific Gravity".....and Specific Gravity is the "Density of the LA solution, divided by the Density of the CSF at 37*C". The Specific Gravity of CSF is 1.003-1.008. Hypobaric solution has a S.G. <1.003 Hyperbaric solution has a S.G. >1.008

The pediatric patient will undergo caudal anesthesia....what are the 2 most commonly used agents, the doses, and volumes appropriate for caudal block???

The most common LA agents used are... Bupivacaine (0.125% or 0.25%) Lidocaine (1%) The volume of LA ranges form 0.5mL/kg for a sacral block to 1.25mL/kg for a midthoracic block. The MAX dose for Bupivacaine for children is 3mg/kg, thus a dosing of 0.5 mL/kg of 0.25% Bupivacaine for sacral block affords a margin of safety. Another source states that the dose should be 1mL/kg since 0.25% is 2.5mg/mL. All texts agree that the dose should be reduced by 30% for infants < 6 months old. [NOTE:...another source states to use 0.125% Bupivacaine at 0.05mL/kg/dermatone level to be blocked.]

Of all of the 5 sensory nerves of the ankle, which 3 are the most superficial??

The most superficial nerves that supply sensory innervation to the foot/ankle are the Superficial Peroneal nerve, the Saphenous nerve, and the Sural nerves.....and these are usually easily blocked by infiltration of LA (subcutaneous block) [NOTE: Mnemonic....All superficial sensory nerves of the foot start with the letter 'S'] FYI: The posterior tibial nerve is "least" likely to be blocked with a superficial infiltration block...it is the hardest to block during an ankle block (infiltration)....for this block, a 3cm needle is advanced via a skin wheal raised along the medial aspect of the Achilles tendon at the level of the superior border of the medial malleolus to the posterior aspect of the tibia, posterior to the tibial artery. The deep peroneal nerve can be difficult to block with infiltration, but not nearly as difficult to block as the posterior tibial nerve.

Where is LA injected for a penile block??

The needle puncture sites are at the "10 o'clock" and "2 o'clock" positions at the base of the penis.

What might be the cause of back pain after placement of an epidural catheter???

The onset of back pain & tenderness after epidural placement should raise the possibility of a "space-occupying" lesion, such as a hematoma....Back pain is the 'first' s/sx of epidural hematoma.

How did the sacral hiatus and sacral cornu arise developmentally??

The sacral hiatus results from the fusion of the laminae of the 5th sacral segment. The spinous process is also lacking posteriorly. The sacral cornu lie on each side of the sacral hiatus (lateral to either side of the hiatus) and represent articular crests of the residual laminae.

Describe the anatomic approach to blocking the superficial and saphenous nerves at the ankle....and to the deep peroneal nerve.

The superficial peroneal & saphenous nerves are blocked with subcutaneous infiltration on the dorsal foot (top) from the medial malleolus to the extensor digitorum longus tendon with 3-5mL of LA. The deep peroneal nerve is blocked by inserting a needle at the intermalleolar line between the extensor digitorum longus & extensor hallicus longus tendons to the periosteum (bone) or elicitation of paresthesia....and 5mL of LA is injected.

Describe the anatomic approach to blocking the Sural nerve at the ankle??....and to the Posterior Tibial nerve??

The sural nerve is blocked laterally between the lateral malleolus and the Achilles tendon with a deep subcutaneous fan infiltration of 3-5mL of LA. The posterior tibial nerve is blocked posterior to the medial malleolus....the posterior tibial artery is palpated and the needle directed (posterior) adjacent to the pulse until paresthesia or bone contact is encountered...then 5mL of LA is injected.

The sympathetic response to SAB occurs b/c LAs act on what neurons??

The sympathetic outflow is inhibited during SAB b/c LAs are blocking conduction in "Sympathetic Pre-Ganglionic Efferents" Therefore, a patient with a sensory block to T5 has a HR of 50 bpm after SAB...b/c sympathetic blockade can be 2-6 dermatone segments 'higher' than sensory blockade....and since the cardioaccelerators are at T1-T4 can be blocked with a sensory level block is at T5, then a decrease in HR can occur.

What is "Thoracic Outlet Syndrome"??....what are the implications of this syndrome with regard to patient positioning??

Thoracic Outlet Syndrome....results from compression of the brachial plexus and subclavian artery at the thoracic outlet between the 1st rib and the clavicle...or between the anterior & middle scalene muscles. Patients usually complain of weakness, numbness, or paresthesias in the affected upper extremity after working with the arms overhead. All patients scheduled for surgery in a pronated position (prone) should be assessed for these s/sx....if the patient reports any of the s/sx of Thoracic Outlet Syndrome, the arms should be placed alongside the trunk ('tucked') during the surgery. (an alternative is to remove the armboard pads and use a layer of eggcrate instead, which allows the arms to be less pronated).

Blockade of what nerves will provide complete anesthesia of the leg??

To provide complete anesthesia for the leg, a Femoral Nerve Block (FNB) is usually combined with a Sciatic Nerve Block (SNB) as well as a Lateral Femoral Cutaneous & Obturator nerve blocks. The terminal branch of the femoral nerve is the saphenous (sensory only)

While performing an epidural, the patient develops s/sx that lead you to suspect an intrathecal injection....such as dyspnea with levels higher than T2, secondary to absence of proprioceptive input from afferent fibers in the abdomen & intercostals, respiratory arrest (esp if C3-C5 are affected) d/t paralysis of the diaphragm, and profound hypotension as the LA passes through the foramen magnum and blocks the cranial nerves..."total spinal". What actions should be taken to treat a high spinal anesthetic??

Treatment of high spinal centers around support of breathing and circulation (A,B,C's)... 1. PPV with 100% FiO2, hyperventilate 2. Support circulation with IVF, vasopressors (ephedrine) and positive chronotropes (atropine) 3. Place in Trendelenburg's to facilitate VR (do NOT place head up thinking you will prevent rostral spread, b/c you will only worsen hemodynamics!!)

State the maximum dose (mg) of each agent that is typically used for SAB....for Lidocaine, Bupivacaine, Ropivacaine, and Tetracaine. Of the LA administered via SAB, which produces the most profound motor blockade??

Typical MAX Doses for SAB.... Lidocaine 60mg Bupivacaine 9-15mg Ropivacaine 15-22.5mg Tetracaine.... Hypobaric 10mg Isobaric 15mg Hyperbaric 12mg Tetracaine produces the most profound motor blockade when given via SAB.

For a Bier Block (a.k.a. IVRA), 40-50mL of LA is used for the Upper extremitiy, and 60-200mL of LA (60-75mL according to M&M; 100-200mL according to Stoelting & Miller) is used for the Lower Extremity. What LAs are acceptable for use when performing a Bier Block??

Upper Extremity Bier Block: 40-50mL of 0.5% LIDO Plain 40-50mL of 0.5% Procaine Plain 40-50mL of 0.5% Mepivacaine Plain Bupivacaine is not acceptable b/c of its cardiotoxicity. 2-Chloroprocaine is not acceptable b/c of its association with thrombophelbitis. For a 70kg patient needing an UE Bier Block: 3mg/kg of LIDO....0.5% (5mg/mL)... 3 x 70 = 210mg 210/ 5 = 42mL of 0.5% LIDO plain

What 4 functional changes occur after the Radial nerve is blocked by LA???....What movement is checked to assess motor function of the Radial nerve after it is blocked by LA or injured??

When the main trunk of the Radial nerve is blocked or injured, there is.... 1. Inability to "Supinate" (rotate) the extended forearm 2. Inability to "Extend/ Lift" the wrist 3. Inability to ABduct the thumb (**best/simple test to assess radial nerve function) 4. Inability to extend the metacarpophalangeal joints [NOTE: The Radial nerve motor function is also assessed by checking the ability to "Extend the arm at the elbow (straighten the elbow)"]

The 6 structures that are traversed by the needle for midline SAB include the skin & subcutaneous tissue, the supraspinous ligament, the interspinous ligament, ligamentum flavum, the dura (often felt as a "pop" with pencil point needles when penetrated), and the arachnoid. [For epidural, the last layer penetrated before entering the epidural space is the ligamentum flavum] Where do LAs work after administration into the intrathecal space??......and the patient will be "sympathectomized" when LA reaches what level after SAB or epidural???

With SAB, the LAs work on the Spinal Nerve Root, Rootlets and the Spinal Cord. The spinal nerve roots are bathed in CSF, making them readily accessible to injected LA....thus, for SAB, relatively small amounts of LA are required to produce profound blockade. Sympathetic outflow will be completely interrupted when LA spreads up to T1 or higher....(T1-T4 are cardiac accelerators).

Describe the onset & patient's description of Tourniquet Pain....which nerve fiber(s) mediate(s) tourniquet pain???

~45 minutes after pneumatic tourniquet is inflated, the patient may complain of "Dull Aching Pain" or become "restless", even though adequate analgesia exists for the operation itself....and the pain usually becomes more intense with time. The current explanation for tourniquet pain involves pain transmission via BOTH A-DELTA & C Fibers, and its modulation in the Dorsal Horn synapses. The C Fibers recover faster as the block wanes, thus, the C Fibers may be dominate....definitive treatment for tourniquet pain is release of the tourniquet.