SAB, Epidural Anesthesia – Flashcards
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Vertebral Column
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-Cervical (7) and thoracic (12) vertebra spinous process angels caudad, tight angles, more difficult to insert needle - Lumbar (5) vertebra, shorter and broader, less overlap, easier access for needle placement, catheter passage, and the instillation of anesthetic into the epidural or subarachnoid space -Sacral horns important landmark for performance of a caudal anesthetic procedure - 33 total vertebrae, 24 movable
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Which three spinal ligaments are of special interest to the anesthetist?
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-Supraspinous ligament - intraspinous ligament (thin) - ligamenta flava ("buttery") Landmarks that help identify and access the epidural and subarachnoid spaces. Pass through all three for epidural placement. Anterior: body Posterior: vertebra foramen
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Facets & pain relief
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Compression of facets cause nerve pain, medication injected here is diagnostic if pain is relieved. Block with LA to relieve pain.
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Transforaminal approach
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For temporary relief of bulging disk pain
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Supraspinous Ligament
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-Strong cordlike ligament connect apices of the spinous processes and is major ligament in the cervical and upper thoracic regions
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Spinal cord ligaments & meniges
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Dura: outermost, tough Arachnoid: thin, spider-like Pia: thin and in direct contact with outer surface of spinal cord Subarachnoid space: continuous with central canal of the spinal cord and ventricles, medium for the interaction with local anesthetics and opioids during regional anesthesia Epidural space: potential space outside of the dural sac inside the vertebral canal, tri-podal dune like space
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Ligamenta Flava
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-Strongest of the posterior ligaments -Paired flat ligaments - 3-5mm at L2-L3 interspace -High content of elastic tissue, yellow
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How much distance is there between the skin and the lumbar epidural space?
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- 2.5-8cm with the average being 5cm *Art says 6-7cm average -Epidural space is largest in the midline of the mid lumbar region, at 5-6mm -Stay midline to avoid veins and access largest space (especially with pregnancy, swollen veins)
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Neuroanatomic Mapping & Evaluation of Neuraxial Anesthesia
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- Use dermatomes to determine functional level of blockade - "Straight leg" or "step on the gas" - Cutaneous sensation, pin, nerve stimulator
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What are the epidural levels for common procedures?
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-L1-L2: perianal -L2 or L3: labor or lower abdominal anesthesia - T8-T10: upper abdominal surgery, total hip - T4-T8: c-section - T4-T5: thoracic surgery - C7-T1: chronic pain treatments or arm, shoulder or upper chest surgery
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T4 block symptoms?
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Can't breathe, bradycardia, hypotension, hands tingling or swollen
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Physiology and Mechanism of Action
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- Primary site of action for local anesthetics is on the nerve roots within the spinal cord - Drug distributes through subarachnoid space and spreads - Neuronal transmission is altered and provides anesthesia - Affects sodium channels and inhibits information from being transferred along the spinal cord
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What is a "differential block"?
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-When a local anesthetic interrupts nerve transmissions of autonomic nerves but not sensory nerves or motor nerves. - Can get sympathetic blockade as high as 6 dermatomal levels above injection site. -Hypotension & bradycardia
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Central Neuraxial Blockade (CNB) Indications
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-Inpatient and ambulatory surgeries, lower extremities, perineum and abdomen - used in combination with other techniques to minimize side effects of any one technique Considerations: 1- Will patient be comfortable? 2- Able to remain in required position? 3- Does regional technique outweigh risks of alternate anesthetic technique?
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CNB Advantages
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-Less N/V and urinary retention - Reduced total opioid requirement & can administer long acting analgesics or clonidine -Greater mental alertness - Quick to eat, void and ambulate - Improved outcomes, especially in high risk patients - Blunt body's stress response
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CNB Contraindications/Disadvantages
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- History of HA or backache increases risk of these complications post-op -Backache, postdural puncture headache (PDPH) hearing loss, transient neurologic symptoms, infection and abscess or hematoma formation - If elevated ICP, increased herniation risk - Avoid with musculoskeletal disorders - May worsen diabetic neuropathy - Shock or severe uncorrected hypovolemia - Fixed-volume cardiac state - Arthritis or elderly who can't be immobile easily
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Do SAB or epidurals often cause respiratory changes?
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Rarely affects pulmonary function because diaphragm isn't paralyzed but intraabdominal or intercostal muscle paralysis is present.
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CNB and Coagulation
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-Existence of significant pre-existing or therapeutic coagulopathy increases risk of hematoma formation - Avoid: platelets <100,000, aPTT and bleeding times twice normal values
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CNB and Medications
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-ASA and NSAIDS are safe -Herbal therapy is safe (DC 7 days if possible) - Heparin: have normal aPTT, indwelling catheters should be removed 2-4 hours after last heparin dose -Warfarin: INR <1.5, do not pull cath until INR <1.5 - Should not perform CNB if fibrinolytic or thrombolytic therapy in past 10 days.
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What is a "total spinal"?
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-Spinal reaches too high and causes unresponsiveness accompanied by cardiac and respiratory compromise.
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Most blocks are performed with what type of needle?
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- 25-27g - 3.5 inch
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What are some advantages of a "non-cutting" needle? (AKA pencil-point needle)
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- Encourages midine insertion - Fewer skin contaminates into subdermal tissue - Clearly perceptible "pop" when the dura is pierced - Improved CSF rates - Reduction in PDPH <1% risk - Failure rate <5%
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Surgical or OB spinal
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- C shaped "like a Halloween cat" - Intercristal or Tuffier's line is line between iliac crests at L4 process - Betadine left on for 1 minute for efficacy - 1% lidocaine around insertion, 3-5 ml - For needle<25g use introducer, 18-20g blunt 3.8cm - Dura anywhere from 2.5-9cm in, average 4-5cm
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Straight Midline Approach
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-Insert needle directly midline between the spinous processes and toward the umbilicus -Slight caudad angle, perpendicular - "Pop" when through dura
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What is a Bromage grip?
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Uses patient body to stabilize needle
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Paramedian Approach
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-Needle inserted 1 cm to the caudad aspect of interspace, 1 cm lower and over - Then direct towards spinal canal and angle slightly cephalad -Angle medially 10-15°
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The paramedian approach passes through which ligaments?
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Ligamenta flavum only
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Someone with scoliosis needs which approach?
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Nearly paramedian, angle needle towards processes inside, vertebrae rotate inward
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Taylor Approach
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- L5 interspace - 1cm medial and 1 cm caudad to posterior superior iliac spine - Needle angled medially and cephalic at a 55° angle towards 5th lumbar interspace
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What is the specific gravity of CSF?
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- 1.004-1.009 -500ml produced each day - 30-80ml present in spinal cord
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What is baricity?
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- Resting position of two fluids with differing specific gravities when the fluids are mixed in a single container - CSF & anesthetic agent - Helps determine the spread of the anesthetic mixture into the subarachnoid space
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When baricity is =1 the solution is?
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- Isobaric, not possible to make exact isobaric solution since variance in CSF exists but near isobaric solutions act in approximately the same location they are injected in
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When baricity is <0.999 the solution is?
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- Hypobaric - Less dense than CSF, will rise or float to the highest anatomic position possible - Usually mixed with sterile water
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When baricity is >1.0015
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-Hyperbaric - More dense than CSF, will sink to lowest anatomic position possible - Usually mixed with 5-8% dextrose
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What are the various baricities of drugs?
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...
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Drugs and epidural dosing...
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...
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Agents
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Spinal: isobaric or hypobaric 5% lidocaine with or without epi, hyperbaric 0.75% bupivicaine, isobaric or hyperbaric 1% tetracaine Epidural: 2% lidocaine with or without epi, 0.5-0.75% bupivicaine, 2-3% 2-chloroprocaine, 1% ropivicaine
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Which drugs have the longest duration, why?
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- Tetracaine, bupivicaine and ropivicaine are more protein bound, longer acting - Lidocaine and mepivicaine less protein bound, shorter acting
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SAB/Epidural Additives
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Duramorph: 2.5-5 Fentanyl: 25-100mcg Sufentanil: 2.5-5 mcg Demerol: 25-100mg Dilaudid: Epinephrine: Clonidine: 75mcg epidural 15-30mcg spinal Phenylephrine: 5-10mcg spinal
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What is tachyphylaxis?
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Acute sudden reduction in response to drug, need more drug for same response. Upregulation, replace epidural or move slightly.
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How long would the duration of a spinal be increased if you increased hyperbaric bupivicaine from 10mg to 15mg?
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50% and increases maximum sensory level achieved
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What is one consideration for OB patient and spinal anesthesia?
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-Epidural veins are engorged and they will have slightly higher level of spinal anesthesia
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What is cauda equina syndrome?
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-Persistent paralysis of the nerves with lower extremity weakness and bowel and bladder dysfunction - Caused by deposition of neurotoxic concentrations of hyperbaric anesthetics particularly 5% lidocaine
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What is transient neurologic symptoms, TNS?
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- Pain originating in the gluteal region that radiates to both lower extremities - Few hours- 24 hours after recovery - Last as long as 10 days, resolve spontaneously
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What are some physiological effects of spinals and how are they managed?
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-Somnolence: decreased number of sensory impulses - Bradycardia & hypotension: if block is high enough paralyze nerve fibers that innervate heart, "cardiac accelerators", T1-T4 Treat hypotension: when >20% drop from baseline BP with crystalloids 15ml/kg 15 minutes before procedure Treat bradycardia: α-agonist, 50-100mcg IV phenyleprhine, or atropine 0.4-0.8 mg - GI: Will ↑ peristalsis, GI blood flow, causes N/V Treat: atropine provides indirect antiemetic effect - Urinary retention Treat: catheter
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Post Dural Puncture Headache (PDPH)
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- 0.2-24% - Decreased circulating CSF, leak through dural puncture site - Stretches meninges and tentorium. - Young, female, pregnant at risk - Pain radiates from behind eyes and across head to neck and shoulders - Resolves spontaneously 10 days - Treated with theophylline, caffeine (300mgPO or 500mg IV) and supine position -Postural headache is diagnostic for PDPH
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Blood Patch for PDPH
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- Definitive treatment, <90% cure - Autologous blood 20ml from vein into epidural space - Patient will feel at 12-15ml -Supine at least ½-1 hour post patch *Art says 24 hours... - Do not use with infection/ fever
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PDPH risks
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Lumbar puncture>spinal>epidural
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Epidural dosing for T8 block
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10x volume of spinal 1.5cc/level times
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Nausea with CNB
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- Initial nausea caused by hypotension - Give fluids 15 minutes before spinal - ↑ GI motility - Propofol and midazolam have anti-emetic effects - Epi ↑ PONV - Addition of fentanyl (25mcg) or sufentanil (2.5-5mcg) to spinal ↓ PONV
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What causes nausea and vomiting post epidural?
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Hypotension Ischemia in the vomit centers of the medulla, Ischemia of gut releasing emetogenic substances like serotonin *Treat pressors (ephedrine/neo), propofol, zofran
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Urinary Retention & CNB
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-CNB blocks sympathetic fibers and increases urethral sphincter tone - Cath as last resort
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Neurologic Risk & CNB
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- Patients concerned with risk of paraplegia - Very rare, nerve injury <1:10,000 - Reversibility of complication is time dependent
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Unexpected Cardiac Arrest & CNB
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- Often occurs in young, previously healthy patient - 0.04:10,000-6.25:10,000 - Downward trend in HR followed by abrupt onset of severe bradycardia or systole - Associated with intra-op significant blood loss and orthopedic cement placement - May happen as late at 3 hours post placement Treat: IV fluids, atropine, cardiac resuscitation dose of epi
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Auditory, Ocular and Facial Complications
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- Transient hypoacusis or hearing loss - Retinal hemorrhage - Caused by changes on CSF pressure - Usually self-limiting
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What is the difference between a spinal and an epidural?
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-A spinal is an "all or none" CNB, puncture through dura - An epidural is titratable and allows better control of analgesia, do not puncture through dura, push away from the dura
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What is the standard epidural needle size?
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- 16-18g - 3 inches long - blunted bevel, gentle 15-30° curve at tip - blunted bevel and curve allow needle to push away form dura instead of penetrate it
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Tuohy needle
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-30° curve - Easiest for beginning practitioners - Directional placement - Less likely to puncture subarachnoid space - may inhibit penetration of skin and ligament flava as compared to other needle tips
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Hustead Needle
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-Intermediate needle - 15° curve - Passes easily through skin and ligamenta flava
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Crawford Needle
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- Straight tip - Used with difficult epidural space (calcified lesions) - Higher ratio of accidental dural puncture - Not used by beginners
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Combination epidural/ SAB Placement
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...
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Combination needle
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...
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What size catheters are used with epidural needles?
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-Typically 2 sizes smaller -EG 20g catheter with 18g Tuohy
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Which distance seems to offer the greatest epidural success without causing migration?
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- Thread catheter 3-5 cm -5 intravenous cannulation *Art threads deep then pulls back. Big line mark indicates catheter is past needle, each mark on catheter is 1 cm. Needle at hub is 9cm (usually 6-7cm in before hit space)
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What is the loss of resistance technique?
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- Most commonly used technique - Needle through dermis into interspinous ligament flava, stylet of epidural removed - Loss of resistance syringe with 2-3ml of normal saline and freely moveable plunger - As needle goes through ligamenta flava resistance increases - Loss of resistance when in epidural space
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What causes the "funny bone" sensation in the legs after epidural?
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- Parathesia felt down one or both legs indicate the catheter brushed by a nerve root as it was passing into epidural space
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What is the purpose of a "test dose"?
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- Determine catheter placement. - 3 ml of rapid acting, low toxicity anesthetic, lidocaine 1.5% with 1:200,000 epi (45mg lido:15mcg epi) - Subarachnoid space: spinal anesthesia within 3 mins - Blood vessel: 20% rise in HR and SBP within 30sec, metallic taste, mouth tingling etc. - 100mcg fentanyl can alternatively be used
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Can you withdraw the catheter through the needle?
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- No, this can shear the catheter and embed foreign material into the patients back
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What are the suggested volumes per segment?
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-Cervical and thoracic: 0.7-1ml/segment EG: initial dose <10ml 10-14 dermatomal spread - Lumbar: 1.25-1.5 ml/segment EG: initial dose 15-20ml 12-16 dermatomal spread
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What factors affect epidural spread and what type of injection techniques can be used?
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- Spread of epidural anesthetics may be 3-4 dermatomes greater in elderly patients because of less compliant, less leaky epidural space -Also happens in pregnant patients - Limit to 0.5-1ml/segment initially
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Spinal is located?
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Subarachnoid space
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Spinal dosing for T8 block
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5 feet= .075-.1 cc
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How should all solutions be injected?
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- 3-5ml every 3 minutes titrated to anesthesia level
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Intermittent injection & continuous infusion
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- Intermittent used when high concentration of local anesthetic is administered (2% lidocaine, 0.5 bupivicaine) - Continuous used with lower concentrations of local anesthetic ( 0.0625%- 0.125% bupivicaine, or 0.1-0.2% ropivicaine -Opioid infusion of 2ml/hr for morphine up to 20ml/hr for dilute local (0.125% bupivicaine or 0.1% ropivicaine)
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Epidural opioids
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- May undergo uptake into the epidural fat, systemic absorption or diffusion across the dura into the CSF -Must cross from epidural space to reach opioid receptors in the substantia gelatinosa - Dose is increased 10x from intrathecal dose - Significant absorption into systemic circulation
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How long until maximal spread occurs?
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10-25 minutes When level regresses 1-2 dermatomes detected by scratch or ice test, 30-50% of initial dose is given.
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What technique is attributed to causing one dermatome to remain unaffected?
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- Using an air bubble with the loss of resistance technique. -Recommended to use NS, no air
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Complications of Epidural Anesthesia
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- Use of plain local creates high level of blockade, this will decrease MAP, CO, SV, HR & PVR Treat: ephedrine 5-10mg, phenylephrine 50-100mcg or low dose dopamine HR: atropine or robinul -Backache 30-45%, especially in OB patient, ketoralac 2mg/kg decreases - Dural perforation "wet tap" will cause PDPH
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Epidural is located?
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Above dura
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What is the most critical element to epidural placement?
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Positioning, legs up, curled up
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Combined Spinal and Epidural Anesthesia CSE
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- OB, post-op pain relief - Advantages of each technique while reducing or eliminating disadvantages - Quicker onset of a spinal combined with flexibility of an epidural
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Two-level technique
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- Epidural placed then spinal anesthesia 1-2 interspaces lower - Able to test epidural catheter first then place spinal - Risk:↑ trauma, hematoma, infection
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Single Level Technique: Needle-through-needle
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- Insertion of an epidural needle at appropriate interspace then using epidural needle as a guide - Pencil point spinal inserted through epidural needle into subarachnoid space, local injected - Spinal needle removed, epidural catheter threaded into place - Risk: nerve root trauma, difficulty obtaining CSF
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Sequential Technique
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- Epidural needle placed at the selected interspace, low dose spinal placed using needle-through-needle technique - Patient supine with left lateral tilt - After 15 mins block extended by titrating epidural local anesthetic until desired level achieved
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CSE technique and OB
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- Rapid onset of intrathecal - Minimal intrathecal opioids in early labor allow ambulation - Epidural needle followed by spinal with needle-through-needle, intrathecal opioids 5-15 sufenta or 25-50mcg fentanyl and/or 2.5 mg bupivicaine -Spinal withdrawn, epidural inserted -Can provide anesthesia for cesarean -Sufenta may cause hypotension - CSE allows faster onset, denser block, lower anxiety, lower pain, greater patient satisfaction
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Complications of CSE
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- Failure to obtain SAB: 3.1-17%, needle misplacement, have longer, 7-15mm, beyond tip of epidural needle, orient bevel upward - Catheter migration: through the dural puncture caused by introduction of the spinal needle -Increased spinal level: more volume more spread, leak from epidural into subarachnoid space -Metallic particles: produced, not proven -Postdural puncture headache: lower incidence, better needle approach, CSF leakage abated, angle seals holes in dura - Infection:slightly increased risk -Neurological injury: 0.02-0.1%
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What lab value should you check every day when an epidural is in place?
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INR want <1.5 Over 3 hold dose of blood thinner Also check platelets (less than 100,000 worrisome)
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Caudal Anesthesia
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-Distal approach to epidural space - Perineal surgeries, OB, urologic, peds - Combined with light GA
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Caudal Equipment & Techniques
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- Prone or lateral with knees to chest - Posterior iliac spines & sacral hiatus - 22g-25g short needle with 10ml local inserted midline between cornua at a steep angle into sacral hiatus - Popping sensation as ventral canal of sacrum entered - Needle lowered parallel advanced into epidural space
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Caudal Anesthesia Agents
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- 0.5-1 ml of solution per kg (kids) - Bupivicaine or ropivicaine 0.125-0.5% - Epi max 2.5mg/kg of 1:200,000 - Clonidine 1mcg/kg for opioid - 12-15ml for sacral and up to 20-30 for lower extremity procedures
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Management & Complications of Caudal Anesthesia
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- Similar to epidural - Sacral area has epidural venous plexus (IV injection) - Infection due to proximity to anus
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What contributions did LaFargue and Pravaz & Rynd make to the advancement of regional anesthesia?
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- LaFargue: needle trochar, morphine under skin - Pravaz: hypodermic syringe - Ryng: hollow needle for delivering hypodermic medications
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When is regional anesthesia used?
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- When local anesthesia requires supplementation with heavy sedation - Choice with difficult airway or full stomach - Permits patient to maintain upper airway and pharyngeal reflexes - NOT an alternative to securing the airway - C-section, TURP, cerclage, total hip, ankle fracture, trauma, aortic stenosis
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What are some absolute contraindications to regional anesthesia?
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- Patient refusal - Coagulation deficiencies: Platelets 2x normal values - Hypovolemic shock (as regional may drop BP) - Abruptio placentae- hypotension will further reduce already low blood flow to fetus, uterine blood flow has few autoregulatory capabilities - Infection at the site - Can't get informed consent - Increased ICP
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What are some relative contraindications and precautions to regional anesthesia?
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- Neonates: used cautiously when either surgery of pain management is required - Children: regional used for post-operative pain relief, easy landmarks, Bier block frequently used with arm fracture - HA or backache history - Underlying neurological disorder - Local anesthetic allergy (may use another chemical class EG ester or amide) - Mobitz 1 or 2 or pacemaker, regional may increase degree of heart block - Spinal issues, fusion, HELLP, DIC, vW disease - Fixed volume cardiac states -Hypovolemia/shock - Increased ICP, neuro issues - NSAIDS and ASA not absolute contraindications
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What are NOT contraindications?
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NSAIDS and ASA Herbals alone
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What are some complications of regional anesthesia?
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- Immediate complications: IV injection risk when tissues are around nerves or blood vessels and local is high volume, toxicity can occur LAST: cardiac dysrythmia, respiratory and CV collapse - Continuous peripheral nerve block complications: Catheter infection, neuro deficits, vascular puncture, bleeding, dyspnea, catheter dislodgment Benefits:Improves postoperative pain control, reduces opioid requirements, decreased PONV
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Technical Difficulties and Regional Anesthesia
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- Broken needles, broken catheters, glass in epidural and subarachnoid spaces, wrong drug injected - Needle breaking: weakest at hub, avoid bending and extreme force - Broken or sheared catheters: as it is pulled back may be sheared off, NEVER pull back through the needle, most can be left in place unless in subarachnoid space. Risk of migrating cephalic reaching spinal cord or through foramen of nerve root. - Glass: break ampules away from tray, use filter needle
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Regional Anesthesia Discharge Information
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- Regional is injection that numbs nerves that sense pain. - Site will be numb up to 24 hours, wears off slowly. - When sensation begins to return start pain meds. - Protect numb area from inadvertent injury. Return to hospital if: -Sensation not returning after 24 hours - Area was numb, sensation returned, numb again - Skin becomes blue or cold - Persistent pain in area that was numb several days after surgery
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What is the mechanism of action of local anesthetics?
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- Primary function is to restrict movement of sodium into the cell. 1: Calcium ions are displaced from the receptor site 2: Reduction in cell permeability to sodium ions 3: Rate of depolarization of the membrane action potential is decreased 4: Cell cannot reach threshold 5: Action potential does not occur 6: Conduction blockade results
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Synthetic local anesthetics have what kind of chemical structure?
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- Weakly basic tertiary amines that are not readily soluble in water
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How are local anesthetics made soluble?
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- Dissolving local anesthetics into hydrochloric acid, producing water solubility -When in aqueous solution anesthetic dissociates into positively charged quaternary amine (cation) and an uncharged tertiary amine base (free base)
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What effect does infection or a low tissue pH have on local anesthetics?
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- Local anesthetic has difficulty diffusing across the cellular membrane - Not enough positively charged cations to cause membrane stabilization
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What are the two short acting LA?
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- Procaine and 2-chlorprocaine
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What are the three moderate acting LA?
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- Lidoccaine, prilocaine, mepivicaine
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What are the 4 long acting LA?
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-Tetracaine, bupivicaine, ropivicaine and chirocaine
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What is the chemical composition of LA?
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- Aromatic group (benzene) lipid - Intermediate bond: either ester or amide - Tertiary amine
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How are the LA esters and amides metabolized?
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- Esters: plasma and tissue cholinesterases - Amides: metabolized in liver
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Which are longer acting amides or esters?
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- Amides are longer acting because they are more lipophilic and protein bound and require transport to the liver for metabolism.
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Which drugs have tend to cause allergic reactions, amides or esters?
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-Esters: If a patient is allergic to one ester, cannot receive ANY ester, may receive amide, no cross allergy between esters and amides (Allergy to amides is very rare)
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Most people allergic to local anesthetics are actually allergic to what?
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PABA (paraben) which is a preservative included in locals. Allergic to sunscreen or lotions will alert you to PABA allergy.
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Which LA are esters?
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Cocaine, procaine, chlorprocaine, tetracaine, benzocaine *One "I" = ESTER
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Which LA are amides?
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Lidocaine, prilocaine, ropivicaine, bupivicaine, articaine, mepivicaine * Two "I's"= AMIDE
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Most anesthetics produce vasodilation since they relax smooth muscle, which two cause vasoconstriction?
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- Cocaine and ropivicaine cause vasoconstriction
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Why is epinephrine added to LA?
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- Prolongs the duration of action by slowing the uptake of the local anesthetic. -Phenylephrine 100mcg may alternately be used
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What is the concern with prilocaine metabolites?
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- Prilocaine is metabolized into o-toluidine which can cause methemoglobinemia, especially if dose is >400mg Treat: methylene blue 1-5 mg/kg
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Electrical Stimulators in Anesthesia
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- Needle advances slowly and amplitude adjusted as the needle approaches the nerve - Negative lead attached to skin, positive to needle - Stimulator adjusted to deliver 2 mA after in subcutaneous tissues - When needle enters sheath amplitude reduced to 0.5mA - Stimulate at lowest possible for response, once response obtained anesthetic can be administered - Stimulus applied at 2.5mA for 15 seconds at intervals of 10-15 minutes
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Ultrasond Guided Regional Anesthesia
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- direct visualization of the distribution of LA improves quality and avoid complications of blocks - best to being learning blocks on peripheral nerves using ultrasound under supervision before going on to more central blocks
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Upper Extremity Blocks
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- 4 approaches: axillary, interscalene, supraclavicular, infraclavicular - Most frequently used is axillary due to ease of performance and high success rate. Used for forearm and hand. - Interscalene: upper arm and shoulder
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Brachial Plexus Block
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- Rami, trunks, divisions, cords, branches - Nerve trunks enveloped by sheath, posterior fascia of the anterior scalene and anterior fascia of middle scalene form interscalene space AKA sheath of brachial plexus - A single injection into this sheath often produces complete block for the upper extremity
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Interscalene Space/ Sheath of Brachial Plexus
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...
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Axillary Approach to Brachial Plexus
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- Best suited for procedures at or below the elbow - Supine, arm abducted 90°, forearm flexed 90° - Well defined pulse in axillary artery more important to successful blockade than the point of needle insertion
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Loss of Resistance Technique
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- "Pop" as needle penetrates fascia and enters the sheath -22g 1½ inche "B" needle inserted medially at 20° angle, parallel to artery - May observe needle for pulsation as confirmation - Advance medially ½-1 inch parralel to axillary artery - Aspirate and observe for blood - 3-5ml test dose of LA - Inject rest of LA in 5 ml increments while aspirating and observing for blood intermittently - Firm pressure above needle to avoid retrograde flow - After 40ml of injection needle is withdrawn - Adduct arm to promote cephalad spread of LA
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Transarterial Technique
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- Uses intentional penetration of brachial artery to confirm needle is within sheath - After artery is ID, wheal of anethstic raised directly above artery - 21g 1½inch needle (or 26g ½inch) inserted perpendicular to skin, and advanced slowly until blood is aspirated - Advanced slowly until blood is no longer aspirated - 3-5ml test dose of LA - Inject rest of LA in 5 ml increments while aspirating and observing for blood intermittently - Firm pressure above needle to avoid retrograde flow - After 40ml of injection needle is withdrawn
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Interscalene Approach
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- Only technique that provides adequate anesthesia to shoulder and the rest of upper extremity - Catheter at level of the trunks - Patients head turned to opposite side - Palpate cricoid cartilage just below thyroid, C6 level (Chassaignac's tubercle) - Straight line drawn posteriorly over SCM - Palpate groove between anterior and middle scalene muscles - 22g, 1½ inch B level inserted into wheal angled caudad - Needle advanced until motor twitch - Lower mA to 0.5 from 1 -Aspirate, test dose - 3-5 ml injection up to 30-35ml
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Subclavian Approach
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-Palpate for pulsations behind and 1-2 cm above clavicle - 22g B needle perpendicular, inward and caudad - Needle advanced until motor twitch - Lower mA to 0.5 from 1 -Aspirate, test dose - 3-5 ml injection up to 30-35ml Watch for Horner syndrome (miosis, partial ptosis, loss of hemifacial sweating) and pneumothorax
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Intersternocleidomastoid Approach
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-Puncture site between heads of SCM muscle, 2 fingerbreadths above sternal notch - At 3-8 cm suprascapular, superior trunk, middle trunk and divisions and cords can be reached - Needle advanced laterally, posteriorly and caudally at 45° angle to table and 15° angle to clavicle -Motor responses at 2-8cm - Lower mA to 0.5 from 1 -Aspirate, test dose - 3-5 ml injection up to 30-35ml
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Continuous Catheter Technique
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-Used for postoperative pain - Continuous administration of LA via brachial plexus catheter at the cervical level reduces opioid requirements and improved analgesia - 22g insulated block needle advanced at C6 level, 45° caudal, dorsal and medial angle - Pop felt upon sheath entrance -NS 5-10ml injected and aspirated for blood - Lower mA to 0.5 from 1 -Aspirate, test dose - 3-5 ml injection up to 30-35ml - Continuous infusion rate 0.125-0.25 at a rate of 4-6ml/hr
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Selective Blocks at the Elbow
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- Primarily sensory blocks, still has motor function - Each nerve blocked at the elbow and wrist - When using tourniquet block intercostobrachial nerve and brachial cutaneous nerve in axilla
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Ulnar Nerve Block at the Elbow
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- Limit volume of solution to reduce amount of pressure and possible ischemia 3-5ml - Elbow flexed 90°, medial condyle of humerus identified - Needle inserted 45° perpendicular to line between medial condyle and olecranon process
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Median Block at the Elbow
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- Anesthesia of forearm and hand - Block median and ulnar nerve - Line drawn from medial to lateral condyles - Brachial artery identified - Short B needle inserted medially to brachial artery at a depth of 0.5-0.75 cm - LA injected 3-5ml, as needle is withdrawn inject 1-2ml to block cutaneous branches of nerve
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Radial Nerve Block at the Elbow
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- Forearm and hand - ID brachioradialis muscle and biceps tendon - Line drawn between medial and lateral condyles - B needle inserted medial border of the brachioradialis muscle -After contact with condyle the needle is withdrawn 2mm - LA 3-5ml injected -Repeat 2-3 times after moving needle - As needle withdrawn inject 3-5ml LA
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Is epinephrine added to LA for blocks beneath the elbow?
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-No, due to small vessel size of wrist, hand, and fingers circulation would be compromised.
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Ulnar Block at the Wrist
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- Ulnar flexor ID with flexed wrist - Line drawn across forearm at level of styloid process to the ulna - Short B needle perpendicular to skin on radial side - 2-4 ml injected - Additional 2 ml as needle withdrawn -Dorsal branch blocked with 3-5 ml in half ring around ulnar aspect of wrist
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Median Block at the Wrist
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- Long palmar muscle & radial flexor muscle ID - Line across wrist that parralels proximal crease - Short B needle perpendicular to skin, 0.5-1cm - LA 2-5 ml in carpal tunnel -2-3 ml as needle is withdrawn
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Radial Block at the Wrist
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- Subcutaneous ring of LA beginning at radial flexor muscles of the wrist and extending to dorsal surface of the ulnar styloid - Avoid if also using ulnar block, circulation
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Intravenous Regional Anesthesia: Bier Block
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- Simple, safe, rapid anesthesia - Lasts <1hr, used for hands and feet - Tourniquet discomfort, use dual tourniquet to extend procedure to 1½ hours - Risk of large amount of local going systemic - Have emergency equipment available, performed in operating area
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Upper Extremity Bier Block
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- Small bore IV in distal vein - Vein in dorsum of hand preferred - Pt supine and padded extremity - Dual tourniquet preferred - After application on tourniquet arm is exsanguinated by wrapping Esmarch bandage tightly around arm - Alternative raise arm for 5 minutes - After exsangiounation cuff inflated 250mmHg - 50ml of 0.5% lidocaine injected in IV (preservative free no epinephrine) - Monitor for LAST - Add 15-30 mg ketoralac for postop analgesia
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IV Regional Anesthesia: Lower Extremity Block
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- Surgery of short duration on foot - LA volume double that of upper extremity - Tourniquet up to 350-400mmHg 1.5 times wrapped around leg - Two separate 9cm wide cuffs ANKLE - LA injected with distal tourniquet inflated - Cuff below calf, LA 35-45ml of 0.5% lidocaine
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Intercostal Nerve Block
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- High success, low pain, significant analgesia - LAST and pneumothorax risk - Supplement when epidural anesthesia can't be used - Analgesia during chest tube placement, easier for patients in pain to breathe - A 22g, B needle inserted perpendicular to rib and advanced then walked off -3ml increments of LA until desired strength - Tachyphylaxis switch to other class, amide to ester
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Lumbar Plexus
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...
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Psoas Compartment Block
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- Blockade of lumbar plexus as a unit by injecting LA into psoas compartment - Patient lateral or sitting - Spinous process L4, line caudally, 5cm line perpendicular and laterally to side - Skin wheal, needle perpendicularly advanced until contact with bone at about 5-10cm - Needle withdrawn directed cephalic advanced until slides over L5 - Loss of resistance technique psoas found at 8-12cm - After aspiration 30-40ml LA injected in 5 ml increments
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Inguinal Perivascular Technique and Femoral Nerve Block
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- Three in one block of lower extremity - Supine, groin prepared and draped - Site of injection is 1cm lateral to femoral artery and 1cm inferior to inguinal ligament - 22g 4cm B needle advanced perpendicularly -2 Hz until quadriceps extend then decreased to <0.5 mA - LA 20-30 ml in 3-5ml increments with intermitted aspiration - Digital pressure for 5-10 minutes - Volume of 30 LA increases block of all 3 nerves - Bupivicaine, ropivicaine and levobupivicaine are commonly used
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Continuous Femoral Nerve Block
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-Landmarks femoral artery and femoral crease -Patient supine, practitioner on side to be blocked - Needle insertion site at lateral border of the femoral artery (1cm lateral to the arterial pulse) - 17g 3½ inch needle with nerve stimulator at 1mA, 2Hz 100-300 µsec inserted and advanced at 45-60° angle - Upon quadriceps muscle twitch current reduced to 0.5 mA - If quadriceps twitch not elicited, needle withdrawn and directed more lateral to femoral artery - Initial bolus of 15-20ml is injected slowly after negative aspiration and catheter threaded slowly 5-10cm beyond needle - Continuous infusion of LA at 8-10ml/hr - 0.2% ropivicaine and 0.25% bupivicaine or levobupivicaine - Remove after 48 hours -Apply 2-3 mins pressure if artery or vein punctured
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Fascia Iliaca Compartment Block
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- Anterior lumbar plexus approach with a puncture point distant from the neuromuscular sheath, no nerve stimulator - Widely used for postop analgesia after lower limb surgery - Supine, projection of inguinal ligament drawn on skin from pubic tubercle to anterior superiod iliac spine - Puncture site marked 1cm caudal to the point at which lateral meets middle third of inguinal ligament line - 10% povidone-iodine, short 24g 50mm needle inserted at less than 90° angle to skin -Loss of resistance as needle tip crosses the fascia lata - Advanced until second loss of resistance is felt as the facia iliac - 30ml of LA injected
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Sciatic Nerve Block
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- In combination with lumbar plexus, femoral or saphenous nerve blocks - Largest nerve trunk in the body, supplies muscles of the back of thigh, skin of the leg and muscles of lower leg and foot - Sims position - Line from posterior superior iliac crest to greater trochanter of femur - Third line perpendicular and bisecting first line - Betadine prep and 2-3ml of lidocaine for wheal - 22g 10cm insulated B needle inserted perpendicularly to skin -Advanced until posterior tibial nerve distribution is elicited - 2Hz and 1 mA until plantar flexion response then <0.5 mA - LA injected 10ml in 5ml increment with intermittent aspiration - Repeated at peroneal nerve - Bupivicaine, ropivicaine, chirocaine and lidocaine
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Popliteal Fossa Block
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- Landmarks: popliteal crease, medial border of femoris biceps, tendon of semitendonosus - Line drawn joining medial border of femurs biceps muscle laterally and semitendonosus - From middle of line second perpendicular line 15cm cephalad, insertion 1cm laterally - 10cm insulated needle through skin wheal at 45-60° angle, 1-2cm sciatic nerve -Aspirate and inject 35-40ml LA
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Ankle Anatomy
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...
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Ankle Block
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- Blocks tibial, sural, superficial peroneal and deep peroneal nerves and saphenous nerve - 5 ml of LA injected after direction and redirection of needle
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Regional Anesthesia and Trauma
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- Sympathetic stimulation may mask hypotension - Give fluids - Decompensation can occur after deduction in circulating catecholamines - Prone to nausea -May lose consciousness after regional and require airway support
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Spinal, epidural and caudal blocks are also known as?
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-Neuraxial anesthesia - Each of these blocks can be performed as a single injection or with a catheter to allow intermittent boluses or continuous infusions.
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Performing a lumbar (subarachnoid) puncture below which level avoids needle trauma to the cord in an adult? Child?
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Adult: below L1 Child: below L3
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What is the principle site of action for neuraxial blockade?
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Nerve root
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What does differential blockade typically result in?
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Sympathetic blockade (judged by temperature sensitivity). May be 2 segments higher than the sensory block which is 2 segments higher than the motor blockade.
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What can produce sympathetic and some parasympathetic blockade?
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Interruption of efferent autonomic transmission at the spinal nerve roots.
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What effects do neuraxial blocks typically have on the CV system?
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-Variable decrease in BP - ↓ HR - ↓ cardiac contractility
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How can you negate deleterious cardiac effects of neuraxial anesthesia?
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-10-20ml/kg of IV fluids will partially compensate for venous pooling minimizing the degree of hypotension
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How should excessive or symptomatic bradycardia be treated? Hypotension?
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Bradycardia: atropine Hypotension: vasopressors
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What are several major contraindications to neuraxial anesthesia?
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Patient refusal, bleeding diathesis, severe hypovolemia, elevated ICP, infection at site of injection, severe stenotic valvular heart disease or ventricular outflow obstruction.
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What indicates you are in the epidural space? Subarachnoid?
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Epidural: sudden loss of resistance as needle penetrates ligamenta flavum Spinal: advanced further through the epidural space and penetrates the dura-subarachnoid membranes as signaled by free-flowing CSF
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Why is epidural anesthesia used, what types of blocks can be performed?
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Epidural anesthesia is a neuraxial technique offering a range of applications wider than the typical "all or nothing" spinal. An epidural block can be performed at the lumbar, thoracic or cervical level.
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What are epidural techniques widely used for?
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Operative anesthesia, obstetric analgesia, postoperative pain control, chronic pain management
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What is the difference in an epidural vs. a spinal onset?
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-Epidural anesthesia is slower in onset (10-20mins) and may not be as dense as spinal anesthesia.
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Which is quicker spinal or epidural? Volume?
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Spinal works quickly. Epidural needs test dose, not comfortable until they lay back down. Reason is spinal is direct shot into subarachnoid space, spreads rapidly. Usually 1-2cc, while epidural is 10-15cc.
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What is the difference in quantity of local anesthetic required for an epidural vs a spinal?
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The quantity (volume and concentration) of local anesthetic is very large in an epidural vs a spinal. Significant toxicity can occur if this amount is injected intrathecally or intravascularly. Safe guards against this include the epidural test dose and incremental dosing.
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What is one of the most commonly used regional techniques in pediatric patients?
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- Caudal epidural anesthesia
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A needle passes through anatomical structures in what order?
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-Skin - Supraspinous ligament - Intraspinous ligament - Ligamenta flavum - Epidural space -Dura - Arachnoid membrane ( M&M page 292, figure A)
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Why doesn't spinal injury due to needle puncture occur below L1 in adults and L3 in children ?
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Spinal cord ends at these levels and the nerves travel by caudal equina "horses tail". These nerves are easily pushed aside (rather than punctured) by an advancing needle. The nerves also float in a dura sac.
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Why does caudal anesthesia carry a greater risk of subarachnoid injection in children than in adults?
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- Dural sac extends to S3 in children (S2 in adults) and they are smaller so it is easier to inject in subarachnoid space
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What is the blood supply to the spinal cord?
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- Anterior artery: anterior 2/3 of cord - Posterior artery: posterior 1/3
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Why does a differential blockade occur?
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-Spinal nerves are composed of a variety of fiber types, the smaller are easier to anesthetize. - Concentration of local anesthetic decreases with increasing distance from the level of injection.
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Sympathetic outflow is? Parasympathetic outflow is?
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Sympathetic: thoracolumbar (T5-L1) Parasympathetic: craniosacral
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What determines vasomotor tone?
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Sympathetic fibers arising from T5-L1 which innervate arterial and venous smooth muscle. Block leads to: - vasodilation of venous capacitance vessels - pooling of blood - decreased venous return to the heart - decreased SVR
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What is the waiting period for anticoagulant medications and neuraxial anesthesia?
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- Ticlopidine/ticlid 14 days - Clopidrogel/plavix 7 days - Abciximab/rheopro 48 hours - Eptifibatide/integrillin 8 hours *ASA and NSAIDS with normal coagulation profile safe.
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How long should herbals be held?
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No contraindications but 7 days is preferred, won't delay surgery if they're on herbals. Garlic: 7 days Ginko: 36 hour Ginseng: 24 hours
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If a patient is receiving heparin for DVT prophylaxis can they undergo neuraxial block?
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-Yes, perform 1 hour or more post administration -Remove 1 hour prior of 4 hours after administration
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Coumadin
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4-5 days hold before placement INR <1.2 don't do it One dose of coumadin before surgery is ok (hasn't started working yet)
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Various Types of Spinal Needle
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Cutting: Quincke is most likely to damage spinal cord (calcified lesions) Pencil point: Whitacre and Sprotte *22g pencil point <risk PDPH compared to 25g Quincke
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In spinal anesthesia two "pops" are felt. What do these "pops" indicate?
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- First pop: through ligament flavum -Second pop: through dura-arachnoid membrane
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How can you make a solution hypobaric or hyperbaric?
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Hypobaric: add sterile water Hyperbaric: add glucose
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Does a parturient patient require more or less anesthetic? Why?
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-Less, reduce anesthetic by 1/3 -CSF is decreased due to engorgement of veins
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What are two commonly used hyperbaric agents?
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Bupivicaine and tetracaine Onset: 5-10 mins Duration: 90-120 mins Addition of epinephrine or phenylephrine prolongs tetracaine action but does not work well with bupivicaine.
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What is the most common type of epidural needle?
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-Standard is 17-18g -3 or 3.5 inches -Gentle 15-30° curve at the tip
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What is a common test dose for epidurals?
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- 3 ml of 1.5% lidocaine (45mg) WITH - 3 ml 1:200,000 epinephrine (15µg)
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Anesthetic Toxicity
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Least toxic: chloroprocaine Intermediate: lidocaine, mepivicaine, levobupivicaine, and ropivicaine Most toxic: bupivicaine
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What are the symptoms of an epidural or spinal hematoma?
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-Sharp back pain and leg pain - Progression to numbness, motor weakness and sphincter dysfunction
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What is the timeframe to decompress hematoma from spinal to restore function?
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8 hours, anything longer recovery is unlikely.
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What is the greatest immediate risk of nerve block?
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Systemic toxicity caused by inadvertent IV injection. Delayed toxicity can follow the initial injection when rapid or excessive amounts of local anesthetic are absorbed systemically.
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How is good anesthesia obtained?
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Only when local anesthetic is injected in close proximity to the nerve or nerves that are to be blocked.
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A perineural injection may produce brief accentuation of the parasthesia, what indicates intraneural injection?
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Intraneural injection produces an intense searing pain and indicates the injection should immediately be terminated and the needle repositioned.
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How can surgical anesthesia of the shoulder and upper extremity be obtained?
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Neural blockade of the brachial plexus (C5-T1) or its terminal branches at several sites.
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Which approach is most optimal for procedures on the shoulder, arm and forearm?
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Interscalene approach, produces a block that is most intense at the C5-C7 dermatomes and least intense in the C8-T1 dermatomes.
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Which approach is optimal for procedures from the elbow to the hand?
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Axillary approach to the brachial plexus, produces the most intense nerve block in the distribution of the C7-T1 (ulnar nerve)
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Which type of block provides good homogenous anesthesia to the brachial plexus, can be used for procedures involving the hand, forearm, elbow and upper arm and are conducive to indwelling catheter placement for postoperative analgesia?
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Infraclavicular blocks
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Which type of block produces intense surgical anesthesia for short surgical procedures (45-60minutes) in the forearm, hand and leg?
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Intravenous regional anesthesia AKA Bier block
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Which type of block is useful in numerous procedures involving the thigh and knee, or as an adjunct to procedures distal to the knee that require anesthesia to the medial aspect of the lower leg (saphenous distribution)?
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Femoral nerve block
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Which block does not require a nerve stimulator, is performed quickly, is not very stimulating and patients do not often require sedation?
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Fascia iliaca blocks
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Blockade of which nerve provides anesthesia for many surgical procedures involving the hip, knee, or distal lower extremity?
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Sciatic which may be blocked at numerous sites along its course.
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Which block is useful for foot and ankle surgery and can result in complete anesthesia of the limb distal to the knee if a separate saphenous nerve block (terminal nerve of the femoral nerve) is also included?
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Popliteal block
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Which block is being increasingly used to provide postoperative analgesia following mastectomy, inguinal hernia repair, and several procedures involving the chest and body wall?
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Paravertebral block
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From superior to inferior what is the order of anatomical structures?
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VAN: vein, artery, nerve
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From lateral to medial what is the order of anatomical structures?
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NAVEL: nerve, artery, vein, empty space, lymphatics
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What causes hydrostatic (ischemic) injury to nerve fibers?
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- Injection that is intraneural, within the nerve substance, generates high pressures and cause hydrostatic (ischemic) injury to nerve fibers.
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When blocking the upper extremity which two nerves muct be blocked separately to prevent pain from tourniquet?
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-medial brachial cutaneous - intercostobrachial
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Brachial Plexus Anatomy
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...
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What are some complications of inter scalene blocks?
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- Incidental blockade of phrenic nerve leading to respiratory failure. - Horner's syndrome: miosis, ptosis, anhidrosis, dyspnea, hoarseness - Even a small amount (1-3ml) of LA injected into the vertebral artery goes straight to the brain and causes seizures. - Advancing the needle too far can lead to puncture of the pleura and pneumothorax.
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In the axilla where is the musculocutaneous nerve?
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The musculocutaneous nerve has already left the sheath and lies within the coracobrachialis muscle. This is why this nerve must be blocked separately.
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What is the "pull-push-pin-pin" technique to assess quality of
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Pull: flex the arm (checks musculocutaneous nerve) Push: arm against resistance (radial nerve) Pin: prominence (median nerve) Pin: fifth digit (ulnar nerve)
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When a procedure involves use of a pneumatic tourniquet which two nerves must be blocked proximal to the axilla?
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Intercostobrachial Medial Brachial
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The lumbar plexus is innervated from which vertebrae?
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Ventral rami of L1-T4 (with some contribution from T12)
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The lumbar plexus (primarily L2-L4) forms which three nerves that innervate the lower extremity?
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- Femoral cutaneous - Femoral -Obturator Lie within the substance of the psoas muscle and emerge within a common fascial sheath that extends proximal to thigh. The common peroneal and tibial nerves arise from the sciatic nerve in the lower leg.
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How is the deep peroneal nerve blocked for an ankle block?
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The deep peroneal nerve is blocked by identifying the groove formed proximally by the extensor halluicus longs tendon and the extensor digitorum longs tendons.
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Intercostal blocks are rarely used as sole anesthesia techniques, when are they used?
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To supplement general anesthesia, for postoperative analgesia following thoracic and upper abdominal surgery, and for relief of pain associated with rib fractures, herpes zoster, and cancer.
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Which block results in the highest blood levels of local anesthetic in the body (per volume)?
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Intercostal blocks
