prameela peripheral nerve blocks anatomy and physiology considerations in anaesthesia
- 1. Peripheral Nerve Blocks Dr. Prameela Dept of Anesthesia
- 2. Objectives Discuss the advantages and disadvantages of peripheral nerve blocks Discuss the physiology and pharmacology of peripheral nerve blocks Identify the types of upper and lower extremity peripheral nerve blocks, their effects and uses. Discuss common complications of peripheral nerve blocks
- 3. Advantages of PNB • Reduced postoperative pain resulting in greater patient satisfaction with their pain management • Early ambulation and discharge • Decreased side effects of nausea and vomiting, drowsiness secondary to less opioid use for pain control. • Less sedation during surgery allows patients to remain conscious (MAC) thus protecting their airway and avoiding airway manipulation and intubation
- 4. Disadvantages of PNB • Requires technical expertise from a variety of medical clinicians • Time required preoperatively for block placement. This may be offset by decreased anesthesia time in the OR and shorter length of stay in the PACU • Contraindicated in patients with a history of coagulopathies, preexisting neuropathies, anatomical aberrancy/pathology at injection site, or systemic disease or infection
- 5. Neurophysiology Local Anesthesia (LA) blocks transmission in ascending and descending nerve pathways. The order of the nerve fibers affected by LA is sensory, motor, and sympathetic. Of note, resolution or regression of the block occurs first in motor fibers, then sensory and lastly sympathetic. This pattern is important when instructing patients about preemptive pain management and postoperative use of the extremity.
- 7. Local Anesthetics for Peripheral Nerve Blocks Drug Concentration (%) Onset Duration (min) Maximum Single Dose Lidocaine 1-1.5 Fast 60-180 300 mg Mepivacaine 1.5-2.0 Fast 3-5min 120-140 Peak 15-45 min 400mg Bupivicaine 0.25-0.5 Slow 4-10min 240-360+ Peak 30-45min 175mg Ropivacaine 0.5-1 Slow 10-30 min 300-600+ 250mg
- 8. Brachial plexus anatomy The brachial plexus extends from C5 to T1; (C5, C6, C7, C8 and T1). It innervates the shoulder and arm. The brachial plexus begins as spinal nerve roots and continues to the terminal branches that supply the upper extremity. Specifically, the anatomy progresses from roots to trunks, trunks to divisions, divisions to cords (lateral, medial and posterior cords) and finally to terminal nerve branches
- 11. Interscalene Block (ISB) Suitable for shoulder and upper arm procedures involving the lateral 2/3 of the clavicle, proximal humerus, and the shoulder joint i.e. total or hemiarthroplasty, arthroscopy, subacromial decompression, and procedures for the instability of the shoulder joint, rotator cuff repair and frozen shoulder. The block is performed at the level of the distal trunk and the origin of its divisions blocking nerves at C4-C6. It is the most proximal to the brachial plexus so not recommended for hand surgery Not recommended for patients with impaired pulmonary function. ISB obstructs the phrenic nerve, resulting in ipsilateral diaphragmatic paralysis
- 12. Interscalene Block The approach to the brachial plexus lies in the neck between the interscalene muscle and the clavicle. The patient lies supine with the head facing away from the side to be blocked. Landmarks include the sternocleidomastoid muscle, external jugular vein, and the cricoid cartilage. The level of the cricoid cartilage corresponds to the C6 vertebral body where the interscalene block is administered. The needle is inserted into the interscalene groove in a slightly medial, caudal, and posterior direction to avoid the vertebral column and vascular structures. Provides spread to the nonbrachial plexus Supraclavicular nerve which supplies sensory innervation to the cape of the shoulder. May not anesthetize the entire posterior aspect of the shoulder.
- 15. Supraclavicular Block (SCB) The indication for a Supraclavicular block is surgery of the upper arm, elbow, forearm, wrist, and hand excluding the shoulder area. The block is performed at the level of the trunks and divisions of the brachial plexus located lateral to the subclavian artery between the first rib and clavicle. The patient lies supine with the head turned away from the side to be blocked. Landmarks on the body include the first rib, subclavian artery and the apex of the lung. Pneumothorax is a potential complication due to the proximity to the apex of the lung.
- 17. Infraclavicular Block • The indication for the Infraclavicular block is surgery of the upper arm, elbow, forearm, wrist, and hand excluding the shoulder area. • The block is performed at the level of the brachial plexus cords, at the clavicle pectoral triangle lateral to the axillary artery and vein. • The patient lies supine with the head turned away from the side to be blocked. • Landmarks on the body to consider are the subclavian artery, the apex of the lung and the pectoralis minor and major muscles. • Used as a substitute for a Supraclavicular when there is difficult anatomy.
- 18. Axillary Block The indication for an Axillary block is surgery involving the elbow, forearm and hand. The block targets three of the four major terminal nerves of the brachial plexus: ulnar, radial, and median nerves. The axillary nerve itself is not blocked. Multiple injections are used to target these nerves. The patient lies in the supine position with abduction of the arm to be blocked. Excessive abduction is avoided since it stretches the brachial plexus increasing vulnerability to injury. Landmarks are the axillary artery, the biceps, coracobrachialis, and triceps muscle.
- 21. Lumbar plexus The lumbar plexus comprises the bundle of nerves which control movement and sensation in the lower extremities. The nerve roots exit the spine at L1-5 and S1-2. They further branch to form several nerves that descend from the plexus down the thigh and leg into the foot. Only nerves roots and branches, no trunks or cords like the brachial plexus The major branches are the lateral femoral cutaneous, femoral, obturator, and sciatic nerves providing sensation to the medial, lateral and anterior aspects of the thigh.
- 22. Femoral Block The femoral nerve is the largest branch of the lumbar plexus with origins in L2, L3, and L4 Provides motor and sensory innervation to the anterior aspect of the thigh, to the knee and to the medial aspects of the calf, ankle, and foot. Used for hip fracture repair and mid to distal femur fracture repair. Analgesia is only partial (usually paired with a spinal) Indications for single injections are knee arthroscopy, total knee arthroplasty; sometimes paired with a proximal sciatic block, BKA; sometimes paired with a popliteal sciatic block, AKA; paired with a sciatic block, ACL repair; paired with a single shot sciatic block, other hip or knee surgeries.
- 23. Femoral Block Patient is positioned in a supine position with the arm on the procedural side stationed out of the sterile field. The injection point is at the intersection of a line drawn from the anterior superior iliac spine to the pubic symphysis and a vertical line just lateral to the femoral artery. The femoral crease and the femoral artery pulse serve as guides. If groin accessibility is limited, secondary to obesity, special positioning or taping may be necessary for pannus retraction
- 24. Adductor Canal Serves as a passageway for the saphenous nerve, the vastus medialis, medial femoral cutaneous, articular branches from the obturator nerve and the medial retinacular nerve as well as the femoral artery and femoral vein Sensory changes of the Adductor Canal block involve the saphenous nerve including the medial and anterior aspect of the knee from the superior pole of the patella to the proximal tibia. Adductor canal block generally spares the quadriceps muscles so pt. able to flex hip with comparable pain control. Placement is mid-thigh around the femoral nerve before it exits the adductor canal Effective alternative to the FNB for patients undergoing TKA or surgery involving the distal thigh and femur, knee and lower leg on the medial side.
- 26. Sciatic Block The sacral plexus provides motor and sensory innervation to the entire lower extremity including hip, ankle and knee. Important components are the sciatic and posterior cutaneous nerves Landmarks are the greater trochanter, the posterior superior iliac spine, and the sacral hiatus. Twitch monitors may be used with the goal of visible or palpable twitches of the hamstrings, calf muscles, foot or toes. The patient needs adequate sedation; commonly painful. Onset of block usually occurs in 10-25 minutes. It provides for complete anesthesia of the leg except for the medial strip of skin innervated by the saphenous nerve. Combined with a femoral block, complete anesthesia of the leg may be achieved. More discreet posterior blocks are generally used
- 28. Popliteal Sciatic Block Anesthetizes the entire leg below the tibial plateau except the skin of the medial aspect of the calf and foot (saphenous nerve distribution) The popliteal block is performed on the sciatic nerve proximal to this bifurcation; about 10 cm from the popliteal crease. Landmarks include the popliteal crease, tendons of the biceps femoris and the semitendonisimus muscles Used for minor surgeries of the distal lower leg, foot or ankle
- 29. Popliteal fossa
- 30. Popliteal Sciatic Block Pt. is positioned in the prone position or in a modified exaggerated lateral position with the leg to be blocked uppermost and flexed at the knee touching the bed and the underlying leg straight. Advantages are improved calf tourniquet tolerance and an immobile foot. Complications may be persistent foot drop with potential pressure necrosis
- 32. Sensory distribution of block except blue area
- 33. Ankle block The ankle block is performed at the tibial nerve and the deep and superficial aspects of the peroneal nerve. The peripheral nerves at the ankle and metatarsal level are the terminal branches of the sciatic (posterior tibial, superficial peroneal, deep peroneal, sural) and femoral saphenous nerves. Indicated for surgery of the foot. The pertinent landmarks are the posterior tibial and dorsalis pedis arteries, tendon of the hallucis longus and medial malleolus
- 34. Ankle Block Patient is positioned in a supine position. Elevation of the patients calf permits the various insertion sites (ring- like) to be more easily accessed. An uncomfortable block requiring 5 different injections Epinephrine is contraindicated. Potential arterial vasoconstriction may lead to foot and/or toe ischemia secondary to the lack of collateral circulation at that location.
- 36. Ankle Block
- 37. Transversus Abdominis Plane (TAP) Block Provides analgesia to the skin and muscles of the antero-lateral abdominal wall and parietal peritoneum. Does not block visceral pain. Goal of the block is to place LA between the internal oblique and transversus abdominis muscle layers resulting in the interruption to the innervation of the abdominal skin, muscles and parietal peritoneum. Administered by landmark, ultrasound guided by anesthesia or direct visualization by the surgeon Single injection vs. catheter bolus. Bupivicaine, Ropivicaine, and Levobupivicaine commonly used. Used for patients undergoing lower abdominal surgery; appendectomy, c-sect, hernia repair, abdominal hysterectomy and prostatectomy.
- 38. Transversus Abdominis Plane (TAP) Block Triangle of Petit: bounded by the latissimus dorsi posteriorly, the external oblique anteriorly and the iliac crest inferiorly. Needle is inserted perpendicular to all planes looking for the tactile sensation of 2 pops. First indicates penetration of the external oblique fascia into the plane between external and oblique muscles. Second pop signifies entry into the plane between internal oblique and transversus abdominis muscles.
- 40. Complications
- 41. Peripheral Nerve Injury • May be associated with needle trauma, inadvertent injection of the nerve, or high injection pressures • Intraneural injection may be identified during block administration by the patient complaining of a sharp pain. The injection is stopped immediately. • Surgical trauma may also cause nerve damage • May not manifest until 7-14 days post-op. • Symptoms: persistent c/o paresthesia, aching or sensory or motor deficits • Treatment is prevention
- 42. Pneumothorax • Associated with Supraclavicular blocks • Causes pts to present with anxiety, tachycardia, tachypnea, chest pain, sub-q emphysema, and diminished breath sounds. • Pts. may not develop symptoms for 6-12 hours • Pneumothorax requires a chest tube. • Ultrasound guidance reduces the incidence since the pleura and first rib is easily visualized.
- 43. Horner’s syndrome Ipsilateral sympathetic blockade which includes nasal congestion, ptosis of one eyelid, miosis, and conjunctive hyperemia. Hoarseness occurs in approximately 10% of patients and is the result of laryngeal nerve block. More prevalent with right sided blocks
- 44. Hemidiaphragmatic paralysis The proximity of the phrenic nerve and its originating cervical roots to the brachial plexus often lends to unintended local anesthetic blockade and diaphragmatic dysfunction. The incidence is 100% after interscalene block Some patients will report mild shortness of breath or altered respiratory sensations and may experience 25-32% reduction in spirometric measures of pulmonary function Supraclavicular blocks have a lower incidence.
- 45. Local Anesthetic Systemic Toxicity or LAST A complication caused by the inadvertent injection of LA into the vascular system or the rapid absorption from the tissue into the vascular system. Studies suggest a more forceful, rapid injection carries a much higher risk than a slow, gentle injection. Prevention must include prudent selection of LA concentration and volume, slow, gentle injection, frequent aspiration, and vigilant monitoring of vital signs Injection into the vein is more serious than into an artery. Arterial allows for dilution and redistribution of the anesthetic into the tissue before it reaches the systemic circulation. Injection into the vein carries the LA directly to the heart and brain.
- 46. LAST Symptoms: ringing in the ears, metallic taste in the mouth, numbness of the lips, twitching of the eyes and lips leading to seizures. Most serious; cardiovascular arrest, respiratory, and central nervous system depression (LOC)
- 47. LAST Immediate treatment: provide adequate ventilation, oxygenation, and circulation (CPR) Infusion of Intralipid Adult Bolus 1-1.5 ml/kg over 1-2 minutes. Pediatric Bolus 1ml/kg. Repeat dosing every 3-5 minutes up to max dose of 3ml/kg. Provide maintenance infusion 0.25-0.5ml/kg/min
Editor's Notes
- #6: Two pathways govern the transmission of nerve impulses. Generation and conduction of afferent sensory (pain, temperature and pressure) take impulses from the periphery to the brain. Efferent motor impulses conduct commands from the brain to the periphery.
- #7: Local Anesthetic combinations: Mixtures of LA are intended to provide faster block onset than single long acting agents and to extend the duration seen with intermediate or short acting agents. LA mixtures can provide a middle ground for block onset and duration compared to short-acting and long-acting agents alone. Mepivacaine and Ropivacaine used most frequently. Some centers may use Lidocaine and Ropivacaine. Clonidine, epinephrine, decadron and Sodium Bicarb
- #12: The supraclavicular nerve arises from C3 and C4, specifically the lateral or posterior SCN supplies the upper and posterior part of the shoulder
- #13: The approach to the brachial plexus lies in the neck between the interscalene muscle and the clavicle. The patient lies supine with the head facing away from the side to be blocked. Landmarks include the sternocleidomastoid muscle, external jugular vein, and the cricoid cartilage. The level of the cricoid cartilage corresponds to the C6 vertebral body where the interscalene block is administered. The needle is inserted into the interscalene groove in a slightly medial, caudal, and posterior direction to avoid the vertebral column and vascular structures.
- #37: Comparison: Epidural analgesia has the advantage of providing visceral and somatic pain relief. Advantages of the TAP is no hypotension, does not affect motor and sensory function of the lower limbs, and is not sedating like the epidural Catheters are placed for use over an extended period of time. The marked catheters need to be monitored for migration
- #38: Contraindications: patient refusal, infection of the abdominal wall and skin or abnormality at the needle insertion site.
- #44: The phrenic nerve originates at C3 but also has contributing fibers from C4 and C5. It begins at the lateral border of the anterior scalene muscle continuing inferiorly deep to the prevertebral layer of cervical fascia then dividing into right and left.