Question: Appropriate dose in pediatric patients? Propofol and other lipid emulsions work as well? When is it appropriate to start infusion? Neurotoxic sxx or cardiovasc ssx? Effectiveness in combination with epinephrine or vasopressin?
B High blocks associated with abdominal and intercostal muscle paralysis can impair ventilatory functions requiring active exhalation. Patients with High blocks or epidural blocks may complain of dyspnea
Respiratory Effects of Spinal Anesthesia In patients with normal lung physiology, spinal anesthesia has very little effect on pulmonary function.[Greene] Lung volumes, resting minute ventilation, dead space, arterial blood gas tensions, and shunt fraction show minimal change after spinal anesthesia. The main respiratory effect of spinal anesthesia occurs during high spinal blockade when active exhalation is affected due to paralysis of abdominal and intercostal muscles. During high spinal blockade, expiratory reserve volume, peak expiratory flow, and maximum minute ventilation are reduced. Patients with obstructive pulmonary disease that rely on accessory muscle use for adequate ventilation should be monitored carefully after spinal blockade. Patients with normal pulmonary function and a high spinal block may complain of dyspnea, but if they are able to speak clearly in a normal voice, ventilation is usually normal. The dyspnea is usually due to the inability to feel the chest wall move during respiration, and simple assurance is usually effective in allaying the patient’s distress. Clinical Pearls Arterial blood gas measurements do not change during high spinal anesthesia in patients who are spontaneously breathing room air. Since a high spinal usually does not affect the cervical area, sparing of the phrenic nerve and normal diaphragmatic function occurs, and inspiration is minimally affected. Arterial blood gas measurements do not change during high spinal anesthesia in patients who are spontaneously breathing room air. The main effect of high spinal anesthesia is on expiration, as the muscles of exhalation are impaired. Since a high spinal usually does not affect the cervical area, sparing of the phrenic nerve and normal diaphragmatic function occurs, and inspiration is minimally affected. Although Steinbrook and colleagues found that spinal anesthesia was not associated with significant changes in vital capacity, maximal inspiratory pressure, or resting end-tidal PCO2, an increased ventilatory responsiveness to CO2 with bupivacaine spinal anesthesia was seen.[Steinbrook] Greene NM, Brull SJ: Physiology of Spinal Anesthesia, 4th ed. Williams &Wilkins, 1981. Steinbrook RA, Concepcion M, Topulos GP: Ventilatory responses to hypercapnia during bupivacaine spinal anesthesia. Anesth Analg 1988;67:247–252.
Carpenter RL, Caplan RA, Brown DL, et al: Incidence and risk factors for side effects of spinal anesthesia. Anesthesiology 1992;76:906–916. Ward RJ, Kennedy WF, Bonica JJ, et al: Experimental evaluation of atropine and vasopressors for the treatment of hypotension of high subarachnoid anesthesia. Anesth Analg 1966;45:621–629.
Regional Anesthesia Board Review, June 15, 2012 David Seligsohn, MD
A 35-year-old woman in active labor had an epidural catheter placed and was given a bolus of 10 ml of 0.5% bupivacaine containing 1:200,000 epinephrine. Twenty minutes later maternal blood pressure drops to 75/45 mmHg and heart rate to 69 bpm. The Ob/Gyn nurse informs you that the fetal heart is 90 bpm and there is a loss of beat-to-beat variability. The MOST likely explanation for fetal bradycardia and loss of beat-to-beat variability is: A) Fetal bupivacaine toxicity B) Maternal supine hypotension syndrome C) Maternal bupivacaine toxicity D) Maternal increased sensitivity to local anesthetics E) Umbilical cord compression
E Umbilical cord compression High doses of bupivacaine can produce peripheral vasodilation, which in turn produce peripheral venous pooling. This drops maternal blood pressure producing an acute decrease in umbilical blood flow. Loss of fetal beat-to-beat variability results from umbilical cord compression or severe hypotension leading to fetal hypoxemia. The treatment include administration of supplemental oxygen to the mother, altering maternal position to the left side in order to relieve pressure from gravid uterus on great vessels and correcting maternal hypotension. Longnecker DE, Tinker JH, Morgan GE (eds.) Principles and Practice of Anesthesiology. 2nd edition. Mosby Baltimore MD. 1998:1997.
2. Following successful placement of an epidural, a 25-year-old woman had an uncomplicated labor and delivery. However during catheter removal, the catheter breaks 1 cm from the tip. What would be the MOST appropriate action? A) Inform the patient and take no action B) Start the patient on prophylactic antibiotics C) Call the surgical consult and request surgical exploration D) Request an additional study of the epidural space using contrast dye E) Conceal the whole information and tell the patient everything went smoothly
2. A Inform the patient and take no action The presence of a small piece of epidural catheter in the epidural space is less likely to pose any problem. Currently, the standard of care for retention of a segment of epidural catheter in epidural space is to leave the segment in the space, inform the patient of mishap and follow up the patient with neurological examination. However, if a continuous spinal anesthesia is used and catheter tip gets broken or separated in the subarachnoid space, patient should be followed for neurological symptoms and neurosurgical consult be sought for possible retrieval of the broken segment. Use of antibiotics is not advisable. Tio To, Macmurdo SD, McKenzie R: Mishap with an epidural catheter. Anesthesiology 1979;50:260-262.
3. Epidural test dose contains 5 microgram per ml of epinephrine. Suppose you administer a test dose of lidocaine containing 15 micrograms of epinephrine. This would be sufficient to produce: A) Bradycardia B) Hypertension C) Seizure D) Segmental analgesia E) Cardiovascular collapse
3. B Hypertension The dose required to achieve adequate epidural anesthesia can cause serious side effects if injected into the subarachnoid space or into a blood vessel, therefore a test dose is often administered before injection. The test dose often consists of a local anesthetic and epinephrine. The objective of test dose is to rule out intravascular or subarachnoid injection. During administration of a test dose, 15 micrograms of epinephrine is administered which should increase the heart rate by 20% within 60 seconds if the catheter is intravascular in the epidural vein. This same test dose should produce a sensory block if it is in the subarachnoid space. Of the choices given, only choice B is the most plausible. This response (hypertension) will be much more marked if the patient had been on beta- blocker due to unopposed alpha effects. Longnecker DE, Tinker JH, Morgan GE (eds). Principles and Practice of Anesthesiology. 2nd edition. Mosby Baltimore MD. 1998:1401.
4. Which of the following regional blocks are associated with the HIGHEST serum concentration of local anesthetics? Assume you use an identical dose. A) Thoracic epidural B) Caudal C) Brachial plexus D) Intercostal E) Epidural
4. D Intercostal Serum concentration depends upon the vascularity at the site of injection. The more vascularized the tissue, the greater the systemic absorption of the local anesthetic and the increased potential for toxicity. In descending order, the rate of developing serum concentration of local anesthetics from highest to lowest is as follows: intravenous > tracheal > intercostal > caudal > paracervical > epidural > brachial > local nerves > subcutaneous. Morgan GE, Mikhail MS. Clinical Anesthesiology. 2nd edition Appleton and Lange CT. 2002:235.
5. Epidural opioids combined with local anesthetics are increasingly used for optimal management of intraoperative and post-operative analgesia. Which of the following statements regarding this combination are TRUE? A) Fentanyl when combined with epidural bupivacaine will decrease the concentration of the later for satisfactory analgesia B) Fentanyl if used alone can be as effective as local anesthetics for the second stage of labor C) Sufentanil is not appropriate for labor analgesia because it produces unsatisfactory analgesia D) The addition of epinephrine to fentanyl will prolong the duration of analgesia E) The main determinant of the onset of epidural opioid analgesia is water solubility
5. A Fentanyl when combined with epidural bupivacaine will decrease the concentration of the later for satisfactory analgesia. Epidural opioids combined with local anesthetics are increasingly used for optimal management of intraoperative and postoperative analgesia. Local anesthetic when combined with opioids reduces the local anesthetic dose while equaling or sometimes improving analgesia. Opioids block the pain transmission by binding at presynaptic and postsynaptic receptor sites in the spinal cord. Inclusion of opioids can produce side effects such as respiratory depression, nausea, pruritus and urinary retention. Of the choices given one can argue that choice D is correct as well because the addition of epinephrine would decrease the rate of vascular absorption therefore decreasing the systematic opioid blood concentration and further improving the depth and duration of analgesia. However, this combination may not significantly prolong the duration of fentanyl or sufentanil analgesia, since it is lipid solubility that determines the onset of action of epidural placed opioids. Both fentanyl and sufentanil are highly lipid soluble opioids. Longnecker DE, Tinker JH, Morgan GE (eds). Principles and Practice of Anesthesiology. 2nd edition. Mosby. Baltimore MD. 1998:1400.
6. Which of the following properties of bupivacaine BEST explains its cardiac toxicity when compared to other local anesthetics? A) Bupivacaine is more soluble in water B) Bupivacaine produces a sustained block of open calcium channels C) Bupivacaine enhances sodium-potassium exchange in the myocardium D) Bupivacaine increases the sensitivity of myocardial myocardium E) Bupivacaine blocks cardiac sodium channels for prolonged period
6. E Bupivacaine blocks cardiac sodium channels for prolonged period Cardiac toxicity varies for each local anesthetic with bupivacaine being more cardiotoxic than lidocaine. Intravenous injection of bupivacaine may results in hypotension, ventricular tachycardia, fibrillation, and AV heart block. Bupivacaine binds to sodium channel tightly and dissociates slowly, leading to its prolonged and exaggerated effects. It depresses the rapid phase of depolarization in Purkinje fibers and ventricular muscles. Bupivacaine does not enhance the Na-K exchange in the myocardium or increase the sensitivity of myocardium adrenergic receptors to catecholamines. It has no effect on myocardial Ca- channels and is highly lipid soluble. After accidental IV injection, the protein binding sites (alpha1-acid glycoprotein and albumin) are quickly saturated, leaving a significant mass of unbound drug available for diffusion into the conducting tissue of the heart. Cardiotoxic plasma concentrations of bupivacaine are 8 to 10 µg/ml. Stoelting RK, Miller RD. Basics of Anesthesia. 4th edition. Churchill Livingstone. New York NY. 2000:85-6.
Intralipid Currently accepted as appropriate treatment along with ACLS in local anesthetic toxicity: based on documented case reports of lipid rescue and animal studies 20% Intralipid (1.5mL/kg bolus can be repeated 1-2X for persistent asystole) Infusion at 0.25mL/kg/min for 30-60min Caution in its use is still prudent
Inratalipid rescue Questions remain: Best rate of infusion and total dose? Appropriate dose in pediatric patients? Propofol and other lipid emulsions work as well? When is it appropriate to start infusion: Neurotoxic sxx or cardiovasc ssx? When is it safe to stop and avoid reoccurrence of local anesthetic toxic ssx? Possible complications or adverse effects? Effectiveness in combination with epinephrine or vasopressin?
7. A 60-year-old male scheduled for second and third digits tendon repair of the left hand, had a brachial plexus block placed using trans-arterial approach. Fifteen minutes later he is still complaining of sensation and pain with pin prick on the dorsum of the second and third digits. What will be the MOST appropriate approach to completely block the unaffected site? A) Inject 3 ml of local anesthetics lateral to biceps tendon at the flexion of the crease B) Inject 2 ml of local anesthetics 2 cm lateral to the radial border of palmaris longus tendon C) Inject 5 ml of local anesthetics between medial epicondyle and olecranon process proximal to arcuate ligament D) Inject 2 ml of local anesthetics between the interval of the radial artery and flexor carpi radialis tendon E) Re-perform the axillary block using another 10 ml of LA
7. A Inject 3 ml of local anesthetics lateral to biceps tendon at the flexion of the crease For an incomplete brachial plexus block that spares radial nerve distribution, radial nerve block is performed as a supplement. The radial nerve is a terminal branch of posterior cord of brachial plexus and gives rise to the lateral cutaneous nerve of the arm and posterior cutaneous nerve of the forearm (both sensory). At the lateral epicondyle the radial nerve branches into a superficial branch (which innervates the radial aspect of wrist and dorsolateral aspect of 3 1/2 digits) and a deep branch (which innervates the extensor group of forearm muscles). The supplemental block is performed by injecting 3 to 5 ml of local anesthetics at the lateral aspect of biceps tendon at the flexion crease. The other nerve, which often fails to be blocked, is the musculocutaneous nerve. This nerve is blocked by injecting 5-8 ml of local anesthetics into the belly of coracobrachialis muscle. Morgan GE, Mikhail MS. Clinical Anesthesiology. 3rd edition. McGraw Hill, New York NY. 2002: 292 – 293.
Q 2009 S/P axillary brachial plexus block, patient feels sensation on dorsum of hand and thumb. What nerve was missed? Radial Ulnar Median
Q 2009 After an axillary plexus block, patient still feels lateral aspect of the forearm. What nerve was missed? Musculocutaneous Median Radial
Q 2009 In performing brachial artery puncture, which nerve could be damaged? Radial Median Ulnar
Commonly tested facts: Interscalene-commonly missed: Ulnar nerve Supraclavicular-if done properly, may provide the most solid block because at this level (divisions) of the brachial plexus the branches are most confined together. Highest risk for pneumothorax. Axillary-commonly miss intercostobrachialis and musculocutaneous and radial nerve. Least risk for pneumothorax
Brachial Plexus Anatomy
Q 2009 What block is used for rotator cuff tear surgery? Interscalene Infraclavicular axillary
8. A 60-year-old man had an interscalene block for a closed reduction of his left humerus. Fifteen (15) minutes later he has difficulty speaking. The MOST likely explanation is: A) Sympathetic nerve block B) Phrenic nerve block C) Subdural or subarachnoid injection D) Pneumothorax E) Recurrent laryngeal nerve block
8. E Recurrent laryngeal nerve block An interscalene block is performed for procedures involving the upper extremity, including the shoulder. The interscalene block is performed by injecting 40 ml of local anesthetics between anterior and middle scalene muscles at the level of cricoid cartilage. Complications of interscalene block include: recurrent laryngeal nerve block which this patient has, injection into the vertebral artery (leading to seizure), epidural and subarachnoid injections, pneumothorax, and stellate ganglion block leading to Horner’s syndrome (miosis, ptosis, anhydrosis, nasal congestion, vasodilation and increased skin temperature). Besides these, infection, hematoma and nerve injury may also occur. Morgan GE, Mikhail MS. Clinical Anesthesia. 3rd edition, McGraw Hill, New York NY. 2002: 288-289.
Interscalene n.block common complications Phrenic n. block - difficulty breathing Recurrent laryngeal n. block – difficulty speaking IV inject: Vertebral artery -seizure Intrathecal inject - apnea, high spinal Pneumothorax – least likely Stellate Ganglion block – sympathectomy of upper arm and Horner’s syndrome (Increased warmth and redness of the painful arm. Hoarseness, redness of The eye, drooping of the eyelid and pupillary constriction.)
9. Morphine can be injected intravenously, epidurally and intrathecally. If you were to inject 5 mg of morphine intravenously and epidurally at different times in the same patient, which of the following actions of morphine will be MOST significant? A) Greater urinary retention with intravenous administration B) Most intense analgesia with epidural administration C) Shorter duration of action with epidural administration D) Greater incidence of pruritus follows intravenous rather than neuroaxial administration E) Shorter duration of analgesia following epidural administration
9. B Most intense analgesia with epidural administration Urinary retention after neuroaxial block with opioids is more common than after intravenous administration. This is not dose dependent or related to systematic absorption but rather due to interaction of opioids with receptors located in the sacral spinal cord. Keep in mind that epidural administration of morphine produces more intense analgesia, longer duration of action and a greater incidence of pruritus. Analgesia that follows epidural placement of morphine reflects diffusion across the dura to gain access to mu opioid receptors on the spinal cord as well systematic absorption into the circulation. Since morphine is poorly lipid soluble it has slower onset of analgesia but longer duration of action. In contrast, analgesia by epidural administration of highly lipid soluble opioids (fentanyl, sufentanil) is primarily a reflection of systematic absorption. Stoelting RK. Pharmacology and Physiology of Anesthesia. 3rd edition. Lippincott-Raven. New York NY. 1999: 79 – 83.
10. Morphine and Fentanyl are two of the most commonly used opioids for epidural administration. The two differ from each other in that Fentanyl: A) More intense and earlier onset of pruritus B) Delayed incidence of respiratory depression C) Faster onset of analgesia D) Longer duration of action E) Higher sensitivity of fentanyl analgesia reversal by naloxone
10. C Faster onset of analgesia Fentanyl is a more lipid soluble opioid when compared to morphine. Fentanyl’s greater potency and more rapid onset of action compared with morphine, reflects this higher lipid solubility which facilitated its passage across the blood-brain barrier. The short duration of action of fentanyl reflects its rapid redistribution to inactive tissue sites such as fat and skeletal muscles. In contrast, morphine is poorly lipid soluble, is absorbed slowly to reach its site of action in the CNS. Other reasons for poor penetration of morphine into the CNS (< 0.1%) include: high degree of ionization and rapid conjugation with glucuronic acid in liver and kidney. Once inside CNS it diffuses back into circulation slowly. This increases the duration of action significantly when compared to fentanyl. There is no difference in the sensitivity of various opioids to naloxone. Stoelting, RK. Pharmacology and Physiology of Anesthesia. 3rd edition. Lippincott-Raven. New York NY. 1999: 92-93.
11. A 30-year-old man is scheduled for closed reduction of his left humerus. You perform an interscalene block using thirty (30) ml of 0.25% of bupivacaine. Thirty minutes later the patient becomes apneic. The MOST likely differential is: A) Pneumothorax B) Phrenic nerve block C) Recurrent laryngeal nerve block D) Vertebral artery injection E) Subarachnoid injection
11. E Subarachnoid injection This question emphasizes the complications of interscalene block, which include: subarachnoid (as in this case) or epidural injections, nerve blocks (phrenic and recurrent laryngeal nerves), and stellate ganglion block (ptosis, anhydrosis, miosis, enophthalmos, nasal congestion, vasodilation and increased skin temperature). Absorption into systematic circulation due to proximity of vertebral artery can result in CNS toxicity (convulsions). Besides, because of close proximity of cervical neural foramina, inadvertent injection into epidural and subarachnoid space is not uncommon. This may produce high epidural or high spinal anesthesia leading to apnea. Other common complications of interscalene block are: phrenic and/or laryngeal nerves block with associated hemiparesis of the diaphragm and laryngeal muscles. The risk of pneumothorax is remote. Morgan GE, Mikhail MS, Murray MJ. Clinical Anesthesia. 3rd edition. McGraw-Hill New York NY. 2002:289.
12. Celiac plexus block is indicated in patients with intractable visceral pain unmanaged by traditional medications. A successful block would be expected to: A) Block parasympathetic fibers to pancreas B) Enhance peristalsis with diarrhea and manifestation of hypotension C) Block of sympathetic fibers to transverse colon D) Block erection and ejaculation E) Block somatic fibers to pancreas
12. B Enhance peristalsis with diarrhea and manifestation of hypotension Celiac plexus is formed by the union of the greater (T5-T10), lesser (T10-T11), and least (T12) splanchnic nerves and the celiac branch of right vagus. It contains both sympathetic and parasympathetic fibers. This extensive network of ganglia and nerves is located at the level of first lumbar vertebra in the retroperitoneal space along the aorta. Fibers from this ganglion carry pain sensation from many of the intraperitoneal organs such as the pancreas and liver. Celiac plexus block is a sympathetic block, commonly applied for the relief of pain from malignancy of the pancreas, liver, or other upper abdominal organs. A successful block is indicated by disappearance of pain in cancer patients or postural hypotension and diarrhea in normal patients. The later symptoms are due to the preponderance of parasympathetic response. Choice D is more of a function of sacral plexus. Celiac plexus does not supply somatic fibers to pancreas. Wildsmith JAW, Armitage EN, McClure JH. Principles and Practice of Regional Anesthesia. 3rd edition. Churchill Livingstone. 2003:301.
Q 2009 Celiac plexus block most likely complication? Constipation Hypotension
13. A surgeon requests a Bier’s block for the release of left-hand carpal tunnel syndrome. Following tourniquet inflation to 300 mmHg you administer 50 ml of 0.5% lidocaine. However the surgeon decides to terminate the procedure ten (10) minutes after lidocaine administration. What will be the MOST appropriate action at this time? A) Administer 4 mg morphine and then deflate the tourniquet B) Deflate the tourniquet and administer ephedrine or phenylephrine to prevent any hypotensive episodes C) Start deflating and reinflating the tourniquet several times in a minute D) Wait 20 minutes and then deflate and re-inflate immediately, and finally deflate after 1 minute E) Wait an hour before deflating the tourniquet completely
13. D Wait 20 minutes and then deflate and re-inflate immediately, and finally deflate after 1 minute For short procedures involving extremities Bier block can be performed which is the injection of local anesthetics (50 ml 0.5% lidocaine) into the venous system below an occluding tourniquet. If surgery is completed in less than 20 minutes, the tourniquet is left inflated to avoid sudden absorption of local anesthetics into the systematic circulation which can produce cardiac and CNS toxicity. If the surgery is completed between 20 and 40 minutes, the cuff can be deflated and reinflated immediately, thus releasing small amount of local anesthetics into the systematic circulation each time. Finally after 1 minute it is deflated completely. However, one can deflate the cuff as a single maneuver after 40 minutes because most of the local anesthetics has been metabolized and chances of local anesthetic toxicity is insignificant. Stoelting RK, Miller RD. Basics of Anesthesia. 4th edition. Churchill Livingstone. 2000: 193-195.
Complications of IRA are related to the hazards of tourniquet inflation and local anesthetic toxicity. Procedure must ideally be less than 90 minutes. Local anesthetic toxicity can occur at the time of deflation or result from leaking of anesthetic beneath the cuff. Premature accidental cuff deflation is likely to cause acute local anesthetic toxicity if occurring the first 10 to 15 minutes, before the anesthetic has had time to diffuse out of the venous system into the tissues. If surgery is completed in less than 20 minutes, the tourniquet is left inflated for at least that total period of time. If 40 minutes has elapsed, the tourniquet can be deflated as a single maneuver. Between 20 and 40 minutes, the cuff can be deflated, reinflated immediately, and finally deflated after 1 minute to delay the sudden absorption of anesthetic into the systemic circulation. 1. Barash P, Cullen B, Stoelting R. Clinical Anesthesia, 5th Edition, J.B. Lippincott. Philadelphia. 2006:731. 2. Benumof JL, Saidman LJ. Anesthesia and Perioperative Complication. 2nd Edition. Mosby. St. Louis. 1999:83.
14. Following a C-section with a successfully placed spinal block with hyperbaric 0.5% bupivacaine, a 19-year-old female starts complaining of severe headache. Which of the following characteristics associated with post-dural puncture headache (PDPH) will facilitate your diagnosis? A) PDPH is more frequent in man than woman B) PDPH can never be prevented by prophylactic epidural blood patch C) There is a lower incidence of PDPH with Quincke and Pitkin spinal needles D) PDPH is less frequent if the needle bevel is parallel to the direction of dural fibers E) PDPH is made worst in the supine position than in the sitting position
14. D PDPH is less frequent if the needle bevel is parallel to the direction of dural fibers Post-dural puncture headache (PDPH) is most often seen following an epidural block due to wet tap. It is believed due to loss of CSF through the meningeal needle hole resulting in decreased buoyant support for the brain and increased tension on meningeal vessels and nerves. The headache is frontal or occipital and postural in nature which worsens in the sitting or standing position. The headache may be associated with diplopia, tinnitus and decreased hearing acuity. Non-cutting needles (Greene, Whitcare and Sprott) have lower incidence of headache than the cutting needles (Quincke, Pitkin). There is lower incidence of PDPH if the needle bevel is parallel to the meningeal fibers (that is the bevel points in the lateral direction if the patient is in the sitting position). There is higher incidence of PDPH in young, pregnant females and with the use of lower gauge needles. Treatment include: bedrest, analgesics (Tylenol double strength), oral or intravenous hydration, and administration of caffeine sodium benzoate (500 mg iv) and blood patch. Although, controversial, it is likely that a prophylactic epidural blood patch may be effective in preventing postdural puncture headache in patient with accidental dural puncture. Stoelting RK, Miller RD. Basics of Anesthesia. 4th edition. Churchill Livingstone. 2000: 177.
15. A 25-year-old woman is scheduled for tendon reconstruction of her second and third fingers due to a recent dog bite. An axillary block is performed with 30 ml of 0.25% bupivacaine using a transarterial approach. However, 15 minutes later, the patient still complains of pain when the surgeon pricks the thenar eminence. The MOST plausible explanation for continued sensitivity is inadequate block in the distribution of: A) Median nerve B) Ulnar nerve C) Radial D) Musculocutaneous nerve E) Medial cutaneous nerve of the forearm
15. D Musculocutaneous nerve The brachial plexus is formed from the anterior rami of C5 - T1. There are three approaches (interscalene, supraclavicular and axillary blocks) to block brachial plexus based on anatomic locations where local anesthetic solutions are placed. The anesthesia produced with each approach is significantly different in terms of its usefulness. For example in axillary approach of brachial plexus block, musculocutaneous and medial antebrachial cutaneous nerves may be missed, thus this approach may produce inadequate anesthesia of forearm. The Musculocutaneous nerve (C5-C7) leaves the axillary sheath proximal to the point of injection into the axilla. Its principal sensory branch is, lateral cutaneous nerve of the forearm supplying thenar eminence and motor branch to upper arm flexors. The musculocutaneous nerve can be blocked by injecting 10 ml of local anesthetics 5 cm proximal to the elbow crease between biceps and brachialis muscles into the substance of coracobrachialis muscle. Stoelting RK, Miller RD. Basics of Anesthesia. 4th edition. Churchill Livingstone. 2000:189.
16. A 45-year-old man with 10 years history of insulin dependent diabetes (IDDM) and a 3 month prior history of inferior infarct is scheduled for transmetatarsal amputation of the first and second toes for osteomyelitis. For a successful block all the following nerves should be blocked EXCEPT: A) Sural B) Saphenous C) Superficial peroneal D) Deep peroneal E) Tibial
16. A Sural nerve Sciatic nerve is the main nerve of the lower extremity which divides into anterior and posterior tibial nerves near popliteal fossa. Posterior tibial nerve supplies the sole of the foot and is blocked by injecting 5 ml of local anesthetic posterior to medial malleolus, behind posterior tibial artery. Injecting 5 ml of local anesthetics anterior to the medial malleolus can block the saphenous nerve, a branch of femoral nerve which innervates a strip along the medial aspect of foot. Sural nerve innervates the lateral aspect of the foot and little toe. It is blocked by injecting 5 ml of local anesthetic solution between the lateral malleolus and calcaneus. Deep peroneal nerve supplies the dorsum of the foot, lies between the anterior tibial artery and the tendon of the anterior tibial muscle and innervates the skin between the first and second toes and the short extensors of the toes. It is blocked by injecting 5 ml of local anesthetics anterior to medial malleolus lateral to anterior tibial artery. Injecting 5 ml of local anesthetics as a subcutaneous ridge between medial and lateral malleolus blocks superficial peroneal nerve. Stoelting RK, Miller RD. Basics of Anesthesia. 4th edition. Churchill Livingstone. New York, NY. 2000:192.
Sacral Plexus Anatomy
Q 2009 What nerve can you not use nerve stimulation on? Musculocutaneous Radial Saphenous
17. Intrathecal administration of morphine provides prolonged post-operative analgesia. The MOST likely site of morphine action is: A) Medulla B) Fourth ventricle C) Spinal nerve roots D) Cerebral cortex E) Substantia gelatinosa
17. E Substantia gelatinosa Morphine acts at multiple sites (brain, spinal and peripheral tissues) and involves effects on mu1, mu2, sigma and delta receptors. Morphine and related opioids selectively act on neurons and neurotransmitters that transmit and modulate nociception. At the spinal cord level morphine hyperpolarizes the neurons in the substantia gelatinosa via the mu2 receptors of the dorsal spinal cord thus decreasing the afferent transmission of nociceptive impulses to the brain. Morphine also decreases the release of neurotransmitters involved in the transmission of nociception such as substance P in the dorsal horn of spinal cord. Barash PG, Cullen BF, Stoelting RK. Handbook of Clinical Anesthesia. 4th edition. Lippincott Williams & Wilkins. 2001:161.
18. A 69-year-old man with a 15 years history of IDDM is scheduled for debridement of a thigh abscess under local and a MAC anesthesia. The surgeon infiltrates the area around the abscess with 30 ml of 2% lidocaine containing 1:200,000 epinephrine. However, the patient continues complaining of pain on incision at the site of the abscess. The MOST plausible explanation for the lack of anesthesia includes: A) Increased protein binding of lidocaine at the necrotic site B) Formation of increased ionized fraction of local anesthetics at the site of injection due to local tissue acidosis C) Formation of increased non-ionized fraction of local anesthetics D) Limited diffusion of lidocaine due to vasoconstriction produced by epinephrine E) Increased hydrolysis of lidocaine due to acidosis at the local necrotic site
18. B Formation of increased ionized fraction of local anesthetics at the site of infection due to local tissue acidosis Local anesthetics exist in ionized and non ionized forms at physiologic pH. However, the ratio of the two forms (non ionized to ionized) varies depending on the Pka of local anesthetics and the pH of surrounding media. The non ionized form is the lipid soluble form and is the primary determinant of local anesthetic potency. Since the non ionized form is lipid soluble, it crosses the lipophilic nerve sheath to gain access to sodium channels in the nerve membrane. Once inside the nerve sheath, the non ionized form of local anesthetic is converted to the ionized form because of a lower pH. The ionized form binds to Na channels to block nerve conduction. In this question, tissue necrosis, lactic acid production at the infection site increases the ionized fraction of lidocaine (ionized form is not lipid soluble) which limited the diffusion of local anesthetics through the nerve sheath to gain access into the nerve to block impulse conduction. As a result infiltration of local anesthetic produced a very poor block. Stoelting RK, Miller RD. Basics of Anesthesia. 4th edition. Lippincott Williams & Wilkins. 2000:83.
Factors that affect Onset of Local Anesthetics 1. Dose and volume given 2. Concentration of free base/non-ionized/lipid soluble fraction a. pH of surrounding tissue Injection into infected tissues which are acidic environments- slowed onset b. pH of local anesthetic solution i. Alkalinization with 8.4% sodium bicarbonate theoretically hastens onset (increase conc free base). ii. Commercially prepared LA with epi slower than when epi added at time of use. (because epi is unstable in alkaline environment, commercial LA are made more acidic (pH 4-5) therefore lower conc of free base). 3. pKa of local anesthetic agent
19. An 80-year-old man with a medical history significant for CHF and a history of an MI three months ago, has had a transurethral resection of prostate (TURP) done under a spinal anesthetic with 10 mg bupivacaine (0.5%). Vital signs remained stable during the course of surgery, which lasted 60 minutes. Three minutes after the patient was transferred to a regular bed he developed nausea and vomiting and his blood pressure dropped to 65/40. What is the MOST likely differential diagnosis? A) An acute MI due to volume overload and development of severe CHF B) Bupivacaine induced sympathectomy leading to significant decrease in preload due to peripheral vasodilation and venous pooling C) Dilutional hyponatremia D) Unrecognized excessive bleeding from prostate venous plexus E) Continued progression of sympathetic block
19. B Bupivacaine induced sympathectomy leading to significant decrease in pre load due to peripheral vasodilation and venous pooling During a TURP procedure the patient is usually in the lithotomy position. The resulting sympathectomy produced by bupivacaine after a spinal will not significantly alter the preload since little pooling is occurring in the lower extremities while in the lithotomy position. Transfer of the patient to a regular bed reverses this and results in significant venous pooling in the lower extremities. This lead to profound hypotension with/without nausea and vomiting due to decrease in venous return to the heart, decrease cardiac output and decrease systematic vascular resistance. Administration of phenylephrine would have been an appropriate action. Stoelting RK and Miller RD. Basics of Anesthesia. 4th edition. Lippincott Williams & Wilkins. 2000:177.
20. Prilocaine is not used in obstetrics regional anesthesia. Which of the following side effects explains the MOST likely reason for this exclusion? A) Prilocaine is not as safe and as potent as lidocaine B) Prilocaine can cause fetal methemoglobinemia C) Prilocaine has much shorter duration of action than lidocaine which precludes its use D) Prilocaine is more toxic than bupivacaine and lidocaine E) Prilocaine is not metabolized by placenta
20. B Prilocaine can cause fetal methemoglobinemia Of all the amide drugs prilocaine is one of the safest drugs. It is equipotent with lidocaine and has slightly longer duration of action. It is metabolized to O-toluidine, which can reduce hemoglobin to methemoglobin. It is not used during labor anesthesia because “top up” dose may be higher than the toxic dose, which may cause fetal cyanosis. Methemoglobinemia is treated by administration of methylene blue or ascorbic acid. The later is not used as often. Wildsmith JAW, Armitage EN, McClure JH. Principles and Practice of Regional Anesthesia. 3rd edition. Churchill Livingstone. 2003:70.
Methemoglobinemia Benzocaine is used for topical anesthesia for endoscopy and fiberoptic intubations. Doses greater than 200 to 300 mg can result in methemoglobinemia potentially leading to cyanosis and decrease oxygen carrying capacity. Prilocaine is also most commonly used for topical anesthesia (EMLA Cream) and has also been associated with methemoglobinemia when used in high doses. Treatment: 1% methylene blue. 1. Evers AS, Maze M. Anesthetic Pharmacology: Physiologic Principles and Clinical Practice, Churchill Livingstone. New York. 2004:528-529.
21. A 60-year-old female underwent successful hysterectomy for fibroids ten hours ago under lumbar epidural with lidocaine and fentanyl. For the last 7 hours, the patient had been receiving morphine by epidural infusion. The patient continues to complain of her inability to move her lower extremities. Neurological examination indicates an inability to flex the thighs or extend the knees. What will be the MOST appropriate course of action at this time? A) Reassure the patient not to worry about anything B) Stop the epidural morphine and reassess the patient 12 hours later C) Obtain MRI of the lumbar spine and request a neurology consult D) Take the epidural catheter out and reassess the patient a few hours later E) Reverse the effects of morphine with naloxone and reassess the patient an hour later
21. C Obtain MRI of the lumbar spine and request a neurological consult It is extremely difficult to detect any bleeding into the epidural space, which may go undetected. The earliest neurological symptoms and signs (back pain and pressure) caused by hematoma are easily confused with epidural block. Time is of the essence because, if the spinal cord compression persists for longer than 6-12 hours, catastrophic paralysis may result due to spinal cord compression. If the sensory or motor losses progress or outlast the expected duration of action of local anesthetics, neurological advice should be sought and both CT and MRI be ordered. If a hematoma is diagnosed, then the patient must have an emergent laminectomy and decompression to avoid the risk of paralysis. Coagulopathy therefore represents a relative contraindication. The degree of coagulopathy at which it becomes unsafe to perform regional anesthesia is highly controversial. Wildsmith JAW, Armitage EN, McClure JH. Principles and Practice of Regional Anesthesia. 3rd edition. Churchill Livingstone. 2003: 162.
Summary of ASRA consensus… anticoag Antiplatelets: ASA, NSAIDS-no significant risk Ticlopidine-discontinue 14 days prior Clopidogrel-discontinue 7 days prior Platelet glycoprotein IIb/IIIa receptor antagonist SC heparin-no significant risk Unfractionated Heparin-discontinue 2-4hrs prior Neuraxial needles or catheters should be placed 2-4 hours after the last unfractionated heparin dose was administered. Re-heparinization should occur no sooner than one hour after catheter removal LMWH-discontinue 12-24hrs prior Warfarin-discontinue 4-5 days prior
Summary of ASRA consensus…anticoag Streptokinase, urokinase, tPA Herbal therapies Ginko, ginseng and garlic New anticoagulants Thrombin inhibitors fondaparinux
22. A 3-year-old child is scheduled for a repair of hypospadias. The urologist requests a caudal for postoperative pain control. The landmarks for the block include: A) Posterior superior iliac spine B) Coccyx C) Greater trochanter of the femur D) Iliac crest E) Sacral cornu
22. E Sacral cornu Caudal block provides excellent pain control and reduces the stress response to surgery. Accurate location of sacral cornu, which represents unfused laminae of the fifth sacral segment, is essential for performing a caudal block. The posterior superior iliac spine, coccyx, greater trochanter of femur and iliac crest are the landmarks for a sciatic nerve block using the posterior approach. In the posterior approach to sciatic nerve block a straight line is drawn connecting the greater trochanter and posterior superior iliac spine. A perpendicular line is drawn from the mid point inferiorly. A 3.5 inch, 22 gauge needle is inserted 5 cm caudad, and 25 ml of local anesthetics is injected. This point of needle insertion should lie on a line drawn between the coccyx and the top of greater trochanter. Wildsmith JAW, Armitage EN, McClure JH. Principles and Practice of Regional Anesthesia. 4th edition. Churchill Livingstone. 2003:220.
23. Local anesthetics can be administered via a variety of routes. Which of the following characteristics of local anesthetics will be the MOST desirable for a surgery lasting several hours? A) Lipid solubility B) Ratio of non ionized to ionized forms C) High molecular weight D) Increased protein binding E) Presence of ester linkages
23. D Increased protein binding Lipid solubility of local anesthetics correlates with potency, which increases as the total number of carbon atoms in the molecule increase. Onset of action depends upon relative concentration of non-ionized (lipid soluble) to ionized water-soluble form. Only lipid soluble form diffuses across the neural sheath and nerve membranes. Once inside the cell only the charged cation forms actually bind to the receptor. Local anesthetics with ester bond are hydrolyzed by esterases. The duration of action of local anesthetics is associated with protein binding (alpha-1 acid glycoprotein). Morgan GE, Mikhail MS, Murray MJ. Clinical Anesthesia. 3rd edition. McGraw Hill. New- York. 2002: 235.
24. A 20-year-old man is scheduled for closed reduction of a dislocated right humerus. Fifteen minutes later following a successful interscalene block with 40 ml of 0.25% bupivacaine the patient complains of facial flushing and sweating. Neurological examination shows unequal pupils. The MOST plausible explanation for these findings is: A) Horner’s syndrome due to cervical sympathetic block B) Injection into the vertebral artery with toxic manifestations of CNS symptoms C) Diffusion of local anesthetics to brain and block of cranial nerves D) Pneumothorax with symptoms strongly suggestive of hypoxic response E) Recurrent laryngeal nerve paralysis
24. A Horner’s syndrome due to cervical sympathetic block Interscalene block is one of the three approaches for brachial plexus block. The complications associated with this approach are related to the structures located in the vicinity of block. The Horner’s syndrome due to spread of local anesthetic to cervical sympathetic chain on the anterior vertebral body is common. The symptoms of this patient are due to Horner’s syndrome which consists of: miosis, anhydrosis, ptosis, enophthalmos, flushing and sweating. Proximity of other nerves (phrenic and recurrent laryngeal) makes them susceptible to block manifested as dyspnea and hoarseness. Other complications include intra-arterial injection into the vertebral artery, which can produce seizure and inadvertent injection into epidural, subarachnoid and subdural spaces manifested as apnea. Advancing needle too far, especially in the lateral direction, can result in a pneumothorax. Morgan EG, Mikhail MS, Murray MJ. Clinical Anesthesia. 3rd edition. McGraw Hill. New York NY. 2002:289.
25. Which of the following factors, when adjusted, will INCREASE the duration of epidural block? A) Using a local anesthetics with high protein binding B) Using increased volume of local anesthetics C) Using a local anesthetics with low pKa D) Adding sodium bicarbonate to local anesthetics E) Inserting a thoracic epidural
25. A Using a local anesthetic with high protein binding Important factors one should keep in mind while performing the epidural block include onset, duration, quality (density of block) and spread of block. The following factors will increase the duration of epidural block: (i) Increased protein binding (ii) Addition of vasoconstrictors (iii) Increased concentrations The later also increase the quality and onset of block. The spread of block is influenced by volume, age, pregnancy, site (greater spread with thoracic than lumbar epidural), obesity and height. Wildsmith JAW, Armitage EN, McClure JH. Principles and Practice of Regional Anesthesia. 3rd edition. Churchill Livingstone. 2003:151.
26. Following a successful vaginal hysterectomy under epidural anesthesia, a patient complains of numbness and loss of dorsiflexion of the toes. The MOST likely explanation is: A) Epidural hematoma B) Lumbar abscess C) Saphenous nerve injury D) Sacral plexus injury E) Common peroneal nerve injury
26. E Common peroneal nerve injury The most common lower extremity nerves damaged because of compression or stretching from improper positioning or improper padding are: peroneal, sciatic, saphenous and occasionally obturator or posterior tibial nerves. The common peroneal nerve is a branch of the sciatic nerve which branches into posterior tibial and peroneal nerves. Peroneal nerve runs behind the head of fibula and around its neck. Its stimulation evokes dorsiflexion of foot. It is the most frequently damaged nerve in the lithotomy position due to compression between the head of fibula and the metal frame used to support the leg. Proper padding and other precautions to decrease the incidence of this type of injury are essential. The injury to the common peroneal nerve manifests as foot drop, loss of dorsal extension of toes and inability to evert the foot. Stoelting RK, Miller RD. Basics of Anesthesia. Churchill and Livingstone. 4th edition. 2000:206.
Lumbar plexus(L2,L3)FemoralSaphenous which is sensory to medial aspect of leg 3-in-one block attempts to include the lateral femoral cutaneous and obturator nerves. Sciatic (L5, S1-3) know the landmarks for labat’s lines. divides into 1. TibialPosterior tibial (plantar surface) and sural(lateral aspect of foot) 2. Common peronealdeep (web of 1st and 2nd toes) and superficial peroneal dorsal aspect of foot Commonly tested facts
27. Most of the actions of morphine are reversed by naloxone. Which of the following effect of morphine is MOST resistant to naloxone administration? A) Nausea and vomiting B) Pruritus C) Analgesia D) Respiratory depression E) Urinary retention
27. E Urinary retention The disadvantage of epidural opioids is in the increase in unwanted effects such as nausea, vomiting, pruritus, respiratory depression and urinary retention. Pruritus, nausea, vomiting and respiratory depression can be reversed by smaller doses of naloxone without reversing opioid analgesia. You may need higher doses 0.5 µg/kg to 2 µg/kg repeated at 10 minutes interval to reverse the urinary retention. Urinary retention, seen after both regional and systematic morphine administration, is caused by complex effects on central and peripheral neurogenic mechanisms which results in dyssynergia between the bladder detrusor muscle and the urethral sphincter relaxation. Also, urinary retention seems to be mediated through several receptors. This may partly explain the resistance to naloxone administration. Alternatively restricting the opioid dose can minimize the impact of side effects. Wildsmith JAW, Armitage EN, McClure JH. Principles and Practice of Regional Anesthesia. Churchill and Livingstone. 3rd edition. 2003:279.
28. The primary determinant of the duration of a Bier block is: A) Ratio of non ionized to ionized fraction of local anesthetics B) Duration of tourniquet inflation C) Protein binding of local anesthetics D) Volume of local anesthetics administered E) Technique of exsanguination
28. B Duration of tourniquet inflation Following exsanguinations of arm or leg with an Esmarch bandage, the tourniquet is inflated 300 mmHg or about 2.5 times the patient’s systolic blood pressure and 50 ml of local anesthetics solution is administered. The duration of anesthesia depends upon the duration of tourniquet inflation and not on other properties of local anesthetics such as pKa, protein binding or the class of local anesthetics (ester or amide). Since the distribution of local anesthetic is localized, a significant amount of local anesthetic continues to diffuse through the blood and the nerve sheath to reach the nerve endings to block the conduction without reaching the systematic circulation. Therefore, so long as the tourniquet remains inflated, local anesthetic will continue to block nerve conduction. Interestingly, analgesia produced with ropivacaine will be longer lasting than with lidocaine though both produce comparable regional anesthesia. Stoelting RK, Miller RD. Basics of Anesthesia. 4th edition. Churchill and Livingstone. 2000:195.
29. A 60-year-old male with 25 years history of IDDM is scheduled for below the knee amputation using peripheral nerve blocks. Which of the following combination of nerves SHOULD be blocked for a successful anesthesia? A) Femoral, Lateral femoral cutaneous and Sciatic nerves B) Obturator, Femoral and Sciatic nerves C) Obturator, Lateral femoral cutaneous and Sciatic nerves D) Three-in-one block E) Sciatic nerve only
29. A Femoral, lateral femoral cutaneous and sciatic nerves Lumbosacral plexus (L2-S3) is the main nerve supply of lower extremity. The hip and knee joints are supplied by femoral, sciatic and obturator nerves. For unilateral operation below the knee, femoral and sciatic nerves block are sufficient to produce surgical anesthesia because both sensory and motor innervations come from sciatic and femoral nerves. However, above the knee block of these two nerves (sciatic and femoral) is not sufficient to produce surgical anesthesia. For surgeries above the knee, one needs to block additional nerves which include: lateral femoral cutaneous nerve block or three-in-one block, which is block of femoral, lateral femoral cutaneous and obturator nerves. This block also provides analgesia for tourniquet application during the surgical procedure. Wildsmith JAW, Armitage EN, McClure JH. Principles and Practice of Regional Anesthesia. Churchill and Livingstone. 3rd edition. 2003:219.
Lumbar Plexus Anatomy
Lateral femoral Cutaneous Nerve block
30. Manifestation of continued painless paralysis 24-hour later following placement of an epidural is MOST consistent with which one of the following differentials? A) Local anesthetics toxicity leading to nerve damages at the spinal nerve roots B) Adhesive arachnoiditis C) Anterior spinal artery stenosis D) Epidural hematoma E) Epidural abscess
30. D Epidural hematoma The neurological symptoms and signs of epidural hematoma can be very confusing as they are very similar to epidural block. Continued progression or prolonged duration of block should alert the anesthesiologist and a neurological consult with further work up be sought. Anterior spinal artery ischemia manifests itself as painless paralysis of the legs and sphincters and generally is due to profound hypotension or surgical interruption of the blood supply to the cord. Important signs of epidural abscess are pyrexia and leukocytosis with associated back pain and tenderness. They generally appear 3 –4 days after the block. MRI of spinal cord and determination of CSF protein levels are very helpful in the diagnosis. Staphylococcus aureus is the most common causative agent. Adhesive arachnoiditis is due to infection or the presence of detergent in local anesthetics preparation. Wildsmith JAW, Armitage EN, McClure JH. Principles and Practice of Regional Anesthesia. Churchill and Livingstone. 3rd edition. McGraw Hill New York NY. 2002:136, 162-164.
31. Intractable pain due to unresectable pancreatic cancer is MOST effectively treated with: A) Bilateral neurolytic intercostals blocks at T10-T12 B) Bilateral sympathetic block with phenol C) Celiac plexus block with alcohol D) Epidural block with alcohol E) Subarachnoid block with alcohol
31. C Celiac plexus block with alcohol Celiac plexus block is a sympathetic block, which provides pain relief from malignancy of upper abdominal organs particularly pancreas. The ganglion is located retroperitoneally at the lower part of the twelfth thoracic and upper part of first lumbar vertebrae. Initially a trial diagnostic block is performed using 20-25 ml of 0.75% lidocaine or 0.25% bupivacaine under fluoroscopic control. If trial is successful (seen as a pain relief), neurolytic block with 50% alcohol in 1% lidocaine or 7% phenol in water is performed 24-hours later. Other blocks mentioned in the question will not completely relieve the intra-abdominal pain. The complications (hypotension and diarrhea) of the block are generally temporary and are due to parasympathetic predominance. Other rare complications include: intramuscular, intrathecal, epidural injections, sexual dysfunction, pneumothorax, bowel perforation, kidney or liver puncture, retro-peritoneal hemorrhage or paraplegia secondary to spinal cord ischemia. Barash PG, Bruce CF, Stoelting,RK. Clinical Anesthesia. Lippincott-Raven Publishers. 3rd edition. 1997:371- 372.
32. A patient had a spinal anesthetic with 5% lidocaine for a transurethral resection of the prostate (TURP) and was place in the lithotomy position. Following the procedure the patient complained of bilateral buttock pain. What is the MOST likely etiology? A) Femoral neuropathy B) Cauda equina syndrome C) Obturator neuropathy D) Epidural hematoma E) Transient neurologic syndrome
32. E Transient neurologic syndrome The term TNS (Transient Neurologic Syndrome) is used to describe symptoms of backache with radiation into the buttocks or lower extremities. (An earlier used term was Transient Radicular Irritation but that has been abandoned for TNS.) This syndrome is rarely seen after general anesthesia and has been associated with central neuraxial anesthesia with all local anesthetics, particularly lidocaine. Risk of TNS is increased with use of lidocaine, ambulatory anesthesia, lithotomy and knee arthroscopy positions, obesity, and is unaffected by baricity, dose, type of needle, addition of epinephrine, paresthesia, or concentration (no lower incidence with concentrations to 0.5%). TNS typically occurs 12-36 hours after resolution of spinal anesthesia and last for 2- 3 days. TNS is self limited and can be effectively treated with potent nonsteroidal anti- inflammatory drugs. Although femoral and obturator neuropathies are complications of lithotomy positioning, the sensory deficit distribution does not involve the buttocks. Epidural hematoma usually present with paralysis without sensory changes. Cauda equina syndrome is associated with sensory and motor deficits but not with TNS. 1. Barash P, Cullen B, Stoelting R. Clinical Anesthesia, 4th edition, J.B. Lippincott. Philadelphia. 2001:709. 2. Spencer SL, et. Al. Current Issues in Spinal Anesthesia, Review Article. Anesthesiology. 2001:94:888-906.
TNS Transient neurological symptoms (TNS) after spinal anesthesia include pain or sensory abnormalities in the lower back, buttocks, or lower extremities. 4 to 40% incidence of TNS after lidocaine spinal anesthesia. Increased risk associated with lidocaine and factors such as lithotomy position and ambulatory anesthesia. No increased risk associated with baricity of solution or dose of local anesthetics. occurs 12-36 hours after spinal anesthesia and last for 2-3 days. self limited and can be treated with NSAIDS. 1. Liu SS, Joseph RS. Local anesthetics in Barash PG, Cullen BF, Stoelting RK (eds): Clinical Anesthesia. 5th edition. Lippincott Williams & Wilkins, Philadelphia, PA. 2006;467.
33. In performing a brachial plexus block by an axillary approach for a distal radial fracture repair, which of the following nerve MAY need supplementation? A) Median nerve B) Radial nerve C) Ulnar nerve D) Musculocutaneous nerve E) Axillary nerve
33. D Musculocutaneous nerve The brachial plexus is derived from the anterior primary rami of the C-5, C-6, C-7, C-8 and T-1 nerves. As the nerve roots leave the intervertebral foramina, they converge, forming trunks, divisions, cords, and then finally terminal nerves. The axillary approach to the brachial plexus is the most popular because of ease of block, reliability of hand and forearm anesthesia, and safety. This block is ideally suited for outpatients. Axillary block is unsuitable for surgical procedures on the upper arm or shoulder. At the level of the axillary, the musculocutaneous nerve has already left the brachial plexus and travels within the coracobrachialis muscle. Supplementation of this nerve is important since it provides sensory to the lateral portion of the forearm. Supplementation of the axillary nerve is not required since anesthesia of that nerve is not required for this procedure. Miller R. Anesthesia. 5th edition. Churchill Livingstone. New York NY. 2000:1524-1527.
34. After performing an axillary block of the brachial plexus, which of the following sensory distribution would be consistent with a spared musculocutaneous nerve? A) Lateral part of the palm and thenar eminence B) Thumb, index and middle finger, with lateral half of ring finger C) Medial aspect of the hand D) Lateral aspect of the forearm E) Medial aspect of the forearm
34. D Lateral aspect of the forearm The musculocutaneous nerve provides sensation to the lateral aspect of the forearm. The ulnar nerve provides sensory to the little finger and medial aspect ring finger with medial aspect of the hand. The median nerve supplies sensory to the lateral part of the palm, the thenar eminence, thumb, index and middle finger and the lateral half of the ring finger. The medial cutaneous nerve provides sensory to the medial aspect of the forearm. The musculocutaneous nerve is often spared after a block of the brachial plexus via an axillary approach. Its supplementation is therefore important to facilitate surgery involving the distal portions of the arm. Supplementation involved identifying the coracobrachialis muscle and injecting local anesthetic into the body of the muscle. Miller R. Anesthesia. 5th edition. Churchill Livingstone. New York NY. 2000:1524-1527
Q 2009 Which structure is most echogenic? a. tendon b. bone c. muscle d. nerve e. lung paranchyma
TISSUE ULTRASOUND IMAGE FOR REGIONAL ANESTHESIA Veins anechoic (compressible) Arteries anechoic (pulsatile) Fat hypoechoic with irregular hyperechoic lines Muscles heterogeneous (mixture of hyperechoic lines within a hypoechoic tissue background) Tendons predominantly hyperechoic technical artifact (hypoechoic) Bone ++ hyperechoic lines with a hypoechoic shadow Nerves hyperechoic / hypoechoic technical artifact (hypoechoic)
Q 2009 Stellate ganglion block: most likely finding? a. Nasal stuffiness
Stellate Ganglion block What is it? Block performed under fluoroscopy to determine if there is damage to the sympathetic nerve chain and if it is the source of the patient’s arm pain. Primarily a diagnostic block but may provide pain relief in excess of the duration of the anesthetic. How is it done? After skin topicalization near the base of the neck on the affected side, a needle is inserted near the transverse process of the cervical spine (usually at C-6 level). A sterile tubing is attached to the needle and local anesthetic medication is slowly injected through the tubing. How long does it last? It takes less than thirty minutes for the procedure followed by evaluation and recovery for several hours. Expected Results Increased warmth and redness of the painful arm during and after injection. Hoarseness of their voice, redness of the eye, drooping of the eyelid and pupillary constriction for four to eight hours. Pain relief may be noted immediately. Duration of relief is variable. The patient must assess their pain relief over the first three to four hours after the injection and report this to the anesthesiologist.
Q: Which of the following is the most likely cause of dyspnea during spinal anesthesia to a T3 sensory level? A. decreased abdominal muscle tone B. decreased afferent input from the thoracic wall C. increased dead space ventilation D. increased intrapulmonary shunting E. partial diaphragmatic paralysis
Respiratory Effects of Spinal Anesthesia Normal Lung Physiology: little effect on pulmonary function (LV, MV, dead space, ABG’s and shunt fractions) Main respiratory effect during High Spinal Blockade: -Active exhalation due to paralysis of abdominal and intercostals. ERV, PEF, MMV are reduced. -Dyspnea due to inability to feel the chest wall move during respiration. Expiratory muscles impaired. -High spinal usually does not affect the cervical area, sparing of the phrenic nerve and normal diaphragmatic function occurs, and inspiration is minimally affected -No significant changes in VC, MIP, resting EtCO2
Gastrointestinal Effects of Spinal Anesthesia The sympathetic innervation to the abdominal organs arises from T6 to L2. Due to sympathetic blockade and unopposed parasympathetic activity after spinal blockade, secretions increase, sphincters relax, and the bowel becomes constricted. Nausea and vomiting occur after spinal anesthesia 20% of the time. Risk factors: blocks higher than T5, hypotension, opioid administration, and history of motion sickness.[Carpenter] Increased vagal activity after sympathetic block causes increased peristalsis of the gastrointestinal tract, which leads to nausea. Atropine is useful for treating nausea after high spinal.[Ward]