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NEURAXIAL ANESTHESIA: SPINAL EPIDURAL CAUDAL Rebecca Johnson, CA 3 November 29, 2012.

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Presentation on theme: "NEURAXIAL ANESTHESIA: SPINAL EPIDURAL CAUDAL Rebecca Johnson, CA 3 November 29, 2012."— Presentation transcript:

1 NEURAXIAL ANESTHESIA: SPINAL EPIDURAL CAUDAL Rebecca Johnson, CA 3 November 29, 2012

2 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

3 All of the following are true EXCEPT:  A. The interspinous ligament attaches to the ligamentum flavum.  B. The ligamentum nuchae continues inferiorly as the supraspinous ligament.  C. The ligamentum flavum is thickest in the midline and elastin is the primary component.  D. The epidural space terminates cranially at C1.  E. The epidural space is bounded inferiorly by the sacrococcygeal ligament.

4 Answer:  Boundaries of Epidural Space:  Posterior: ligamentum flavum/vertebral laminae  Anterior: posterior longitudinal ligament  Lateral: vertebral pedicles/intervertebral foramina  Inferior: sacrococcygeal ligament covering sacral hiatus  Superior: foramen magnum  D.

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6 Vertebral Column  7 cervical vertebrae  12 thoracic vertebrae  5 lumbar vertebrae  5 fused sacral vertebrae  Rudimentary coccygeal vertebrae  Paired spinal nerves exit at each level, C1 to S5  At cervical level  nerves arise above respective vertebrae  Starting at T1  nerves exit below their vertebrae  As a result…  8 cervical nerve roots but only 7 cervical vertebrae

7 Spinal Canal  Contains:  Spinal cord  Meninges (3 layers) Pia Mater Arachnoid Mater Dura Mater  Fatty tissue  Venous plexus  CSF  Subdural space  Poorly demarcated, potential space that exists between the dura and arachnoid membranes

8 Anatomic features pertinent to the performance of neuraxial blockade include all EXCEPT:  A. In adults, the spinal cord ends at L1-L2.  B. The angulation of the spinous process of the thoracic vertebrae makes a paramedian approach preferable.  C. In adults the dural sac ends at S2.  D. The largest interspace in the vertebral column is L4-L5.  E. Midline insertion of an epidural needle is least likely to result in unintended meningeal puncture.

9 Answer  D.  The largest interspace is L5-S1.  The ligamentum flavum is farthest from the spinal meninges in the midline, measuring 4- 6mm at L2-L3 interspace.

10 Anatomy  The spinal cord extends from the foramen magnum to the level of L1 in adults  In infants, the spinal cord ends at L3 and moves up as they grow older  Lower nerve roots course some distance before exiting the intervertebral foramina  Forms the cauda equina  Pushing vs piercing the cord  The dural sac, subarachnoid and subdural spaces usually extend to S2 in adults  Often to S3 in children

11 Blood Supply  Anterior 2/3 of cord  Anterior spinal artery vertebral artery  Posterior 1/3 of cord  Two posterior spinal arteries posterior inferior cerebellar arteries  Radicular arteries  intercostal arteries in the thorax  lumbar arteries in the abdomen  The artery of Adamkiewicz  Aorta  Typically unilateral and on the ___ side? Left  Major blood supply to the anterior, lower 2/3 of the spinal cord  Injury to this artery can result in …? Anterior spinal artery syndrome

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13 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

14 Mechanism of Action  Principal site of action - nerve root  Local anesthetic bathes the nerve root in the subarachnoid space or epidural space  Spinal anesthesia:  Direct injection of LA into CSF  Relatively small dose and volume to achieve dense sensory and motor blockade  Epidural/Caudal anesthesia:  Same LA concentration is achieved at nerve roots only with much higher volumes and quantities  Level for epidural anesthesia  Must be close to the nerve roots that are to be anesthetized

15 Somatic Blockade  Sensory blockade interrupts both somatic and visceral painful stimuli  Motor blockade produces skeletal muscle relaxation  Provides excellent OR conditions  LA effect on nerve fibers varies according to many factors:  Size of the nerve fiber  Myelination  Concentration achieved  Duration of contact  Smaller and myelinated fibers are more easily blocked

16 Somatic Blockade  Spinal nerve roots contain varying mixtures of these fiber types and they vary in their sensitivity to the LA blockade  This results in a differential block  Which nerve fibers are blocked by the lowest sensitivity to LA?  A. pain  B. motor  C. sympathetic  D. touch  Order of sensitivity:  Sympathetic > pain > touch > motor

17 Somatic Blockade  Sympathetic block is highest, generally 2 (up to 6) segments higher than the sensory block (pain, light touch)  Which in turn is usually 2-3 segments higher than the motor blockade

18 Autonomic Blockade  Block of efferent autonomic transmission  sympathetic and some parasympathetic blockade  Sympathetic outflow from the spinal cord  Thoracolumbar  Sympathetic preganglionic nerve fibers exit the spinal cord with the spinal nerves from T1 to the L2 level and may course many levels along sympathetic chain before synapsing with a postganglionic cell in a sympathetic ganglia  Parasympathetic outflow  Craniosacral  Parasympathetic preganglionic fibers exit the spinal cord with the cranial and sacral nerves  Neuraxial anesthesia does not block the vagus nerve  decreased sympathetic tone and/or unopposed parasympathetic tone

19 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

20 A pt receives a spinal anesthetic with a sensory level of T5. Which of the following is likely to occur?  A. The small bowel will be dilated and relaxed.  B. Glomerular filtration will be decreased by one third.  C. Tidal volume will be reduced by one third.  D. The cardioaccelerator nerves will be unaffected.  E. Blood pressure will lower predominantly by decreasing venous return.

21 Answer  E  Level of sympathetic block can be 2-6 levels higher than sensory block.

22 Cardiovascular Manifestations  Variable decreases in blood pressure  +/- decrease in heart rate and cardiac contractility  Generally proportional to degree of the sympathectomy  Arterial and venous smooth muscle vasomotor tone:  Innervated by sympathetic fibers from T5 to L1  Blocking these nerves causes: vasodilation of the venous capacitance vessels pooling of blood decreased venous return to the heart  Arterial vasodilation may also decrease SVR May be minimized by compensatory vasoconstriction above the level of the block

23 Cardiovascular Manifestations  A high sympathetic block  prevents compensatory vasoconstriction  blocks the sympathetic cardiac accelerator fibers that arise at …? T1–T4  Profound hypotension may occur  Vasodilation combined with bradycardia and decreased contractility  Exaggerated if venous return is further compromised head-up position or gravid uterus  Sudden cardiac arrest sometimes seen with spinal anesthesia  Unopposed vagal tone

24 Cardiovascular Manifestations  Steps to minimize the degree of hypotension:  Volume loading with 10–20 mL/kg of IVF partially compensates for the venous pooling  LUD in the third trimester of pregnancy minimizes obstruction to venous return  Hypotension may still occur  Increase IVFs  Autotransfusion - head-down position  Vasopressors (phenylephrine/ephedrine)  Excessive or symptomatic bradycardia  Atropine  If profound hypotension and/or bradycardia persist  Epinephrine (5–10 mcg)

25 Pulmonary Manifestations  Usually are minimal  diaphragm innervated by the phrenic nerve with fibers originating from C3–C5  Even with high thoracic levels…  tidal volume is unchanged  only a small decrease in vital capacity from loss of abdominal muscles' contribution to forced expiration  Phrenic nerve block may not occur even with total spinal anesthesia  apnea often resolves with hemodynamic resuscitation  suggests that brain stem hypoperfusion is responsible

26 Pulmonary Manifestations  Severe chronic lung disease patients  Rely upon accessory muscles of respiration  Coughing and clearing of secretions require these muscles  High levels of neural blockade impair these muscles  Use caution in patients with limited respiratory reserve  Must weigh against the advantages of avoiding airway instrumentation and PPV  Surgery above the umbilicus  Pure regional technique may not be the best choice

27 Pulmonary Manifestations  Thoracic or upper abdominal surgery  Decreased diaphragmatic function postop  Decreased FRC  Atelectasis and hypoxia via V/P mismatch  Postop thoracic epidural analgesia may improve pulmonary outcome  decrease the incidence of pneumonia and respiratory failure  improve oxygenation  decrease duration of vent support

28 GI Manifestations  Sympathetic outflow originates at T5–L1  Sympathectomy - vagal tone dominance  small, contracted gut with active peristalsis  Excellent operative conditions for lap procedures when used as an adjunct to GENA  Postoperative epidural analgesia has been shown to hasten return of GI function  Hepatic blood flow will decrease with reductions in MAP from any anesthetic technique  Intraabdominal surgery - decrease in hepatic perfusion related more to surgical manipulation than to anesthetic technique.

29 Urinary Tract Manifestations  Renal blood flow – maintained through autoregulation  little clinical effect upon renal function  Neuraxial anesthesia at the lumbar and sacral levels blocks both sympathetic and parasympathetic control of bladder function  Loss of autonomic bladder control results in urinary retention until the block wears off  If no urinary catheter is anticipated perioperatively:  use the shortest acting and smallest amount of LA necessary for the procedure  limit the amount of IVF as much as possible  Monitored pt for urinary retention to avoid bladder distention following neuraxial anesthesia

30 Metabolic & Endocrine Manifestations  Surgical trauma produces a neuroendocrine response  localized inflammatory response  activation of somatic and visceral afferent nerve fibers  increases in ACTH, cortisol, epinephrine, NE, and vasopressin  activation of the renin–angiotensin–aldosterone system  Clinical manifestations:  HTN, tachycardia, hyperglycemia, protein catabolism, suppressed immune responses, and altered renal function  Neuraxial blockade can partially suppress (during major invasive surgery) or totally block (during lower extremity surgery) this stress response  Reduction in catecholamine release  may decrease perioperative arrhythmias and reduce the incidence of ischemia  Neuraxial block should precede incision and extend postop

31 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

32 Indications for Neuraxial  Used alone or in conjunction with GENA for most procedures below the neck  Most useful for:  lower abdominal  inguinal  urogenital  rectal  lower extremity surgery  Lumbar spinal surgery may also be performed under spinal anesthesia  Upper abdominal procedures  difficult to achieve a sensory level adequate for patient comfort yet avoid the complications of a high block  Spinal anesthesia for neonatal surgery

33 Contrandications  Patient refusal  Infection at the site of injection  Coagulopathy or other bleeding diathesis  Severe hypovolemia  Increased intracranial pressure  Severe aortic stenosis  Severe mitral stenosis  Patient refusal  Infection at the site of injection  Coagulopathy or other bleeding diathesis  Severe hypovolemia  Increased intracranial pressure  Severe aortic stenosis  Severe mitral stenosis  Preexisting neurological deficits  Sepsis  Uncooperative patient  Demyelinating lesions  Stenotic valvular heart lesions  Severe spinal deformity  Preexisting neurological deficits  Sepsis  Uncooperative patient  Demyelinating lesions  Stenotic valvular heart lesions  Severe spinal deformity AbsoluteRelativeControversial  Inability to communicate with pt  Prior back surgery at site of injection  Complicated surgery  Prolonged operation  Major blood loss  Maneuvers that compromise respiration  Inability to communicate with pt  Prior back surgery at site of injection  Complicated surgery  Prolonged operation  Major blood loss  Maneuvers that compromise respiration Preexisting neurological deficitsPatient refusalInfection at the site of injectionInability to communicate with ptSepsisCoagulopathy or other bleeding diathesis

34 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

35 Oral Anticoagulants  Long-term warfarin therapy  Must be stopped  Need PT/INR to be normalized  Perioperative thromboembolic prophylaxis  If initial dose given > 24 h prior to the block or if more than one dose was given PT and INR need to be checked  If only one dose given within 24 h Safe  Removing an epidural catheter from patients receiving low- dose warfarin (5 mg/d) Safe

36 Antiplatelets  Aspirin and NSAIDs  Alone don’t appear to increase risk of spinal hematoma  More potent agents  Ticlopidine (Ticlid) 14 days  Clopidogrel (Plavix) 7 days  Abciximab (Rheopro) 48 h  Eptifibatide (Integrilin) 8 h

37 Unfractionated Heparin  Minidose subQ prophylaxis  OK to proceed  Patients to receive heparin intraoperatively  1 h or more before heparin administration  A bloody epidural or spinal does not necessarily require cancellation of surgery discussion of the risks with the surgeon careful postoperative monitoring needed  Removal of an epidural catheter  1 h prior to dosing  or 4 h following dosing  Patients on therapeutic doses of heparin (elevated PTT)  Avoid neuraxial  The risk of spinal hematoma is undetermined in the setting of full anticoagulation for cardiac surgery

38 LMWH (Enoxaparin, Dalteparin, -parin)  Intro of Lovenox in the US in 1993  Reports of spinal hematomas associated with neuraxial anesthesia  Many involved intraop or early postop use, and several also taking antiplatelets  If bloody needle or catheter placement occurs  Delay until 24 hrs postop  Postop LMWH thromboprophylaxis if epidural catheter in place  Remove 2 hrs prior to the first dose  Or 10 hrs after last dose and subsequent dosing should not occur for another 2 hrs

39 Fibrinolytic or Thrombolytic Tx  Best to avoid neuraxial.

40 Please note…  Drugs/regimens not considered to put pts at increased risk of neuraxial bleeding when used alone (minidose subQ heparin, NSAIDS) may in fact increase the risk when combined.

41 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

42 Which of the following statements regarding spinal needle insertion is TRUE?  A. The first significant resistance encountered when advancing a needle using the paramedian approach is the interspinous ligament.  B. If bone is repeatedly encountered at the same depth when the needle is advanced, the needle is likely walking down the inferior spinous process.  C. The midline approach is preferred in patients with heavily calicified interspinous ligaments.  D. Free flow of CSF after resolution of a paresthesia usually indicates that the needle is in a good position.  E. Penetration of the dura mater is more easily detected with a beveled needle.

43 Answer  D.  If a paresthesia occurs you should immediately stop advancing the needle and check for CSF.  Obtaining CSF after resolution of a paresthesia indicates the needle encountered a cauda equina nerve root in the subarachnoid space and the needle tip is in a good position.  DO NOT inject LA in presence of a persistent paresthesia!

44 Anatomic Approaches  Spinous processes  Cervical and lumbar spine – horizontal Needle directed with only a slight cephalad angle  Thoracic spine – slant in a caudal direction and can overlap Needle angled significantly more cephalad  First palpable cervical spinous process is C2  Most prominent is…? C7  Inferior tip of the scapula at level of …?  Spinous process of T7  Highest points of both iliac crests (Tuffier's line) ?  Body of L4 or the L4–L5 interspace  Posterior superior iliac spine  S2 posterior foramina  Sacral hiatus  Depression just above or between the gluteal clefts and above the coccyx

45 Midline Approach  Body positioned with the plane of the back perpendicular to the floor  Palpate for depression between the spinous processes of the vertebra above and below the level to be used  Subcutaneous tissues offer little feeling of resistance  Supraspinous and interspinous ligaments felt as an increase in tissue density  If bone contacted superficially  needle is likely hitting..? the lower spinous process  If bone contacted at a deeper depth  and needle is in the midline it is likely hitting…? the upper spinous process  or if it is lateral to the midline it is likely hitting…? a lamina  Ligamentum flavum - obvious increase in resistance  At this point, spinal and epidural anesthesia differ

46 Paramedian Approach  May be useful in certain patients  severe arthritis  kyphoscoliosis  prior lumbar spine surgery  2 cm lateral to the inferior aspect of superior spinous process  Penetrates the paraspinous muscles  lateral to the interspinous ligaments  needle may encounter little resistance initially and may not seem to be in firm tissue  Needle advanced at a 10–25° angle toward the midline  LOR is often more subtle than with the midline approach

47  Bone encountered deep  lateral part of the lower lamina  redirected only slightly upward, more toward the midline  Bone at a shallow depth  medial part of the lower lamina  redirect mostly upward and slightly more lateral

48 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

49 Spinal Needles  Available in an array of sizes (16–30 gauge), lengths, and bevel and tip designs  Tightly fitting removable stylet  avoids tracking epithelial cells into the subarachnoid space  2 broad groups 1. Sharp (cutting)-tipped Quincke needle is a cutting needle with end injection 2. Blunt tip (pencil-point) needles Whitacre – rounded point with side injection Sprotte – rounded point with long side opening markedly decreased the incidence of PDPH

50 Spinal Catheters  Very small subarachnoid catheters are currently no longer approved in the US  Association with cauda equina syndrome.  Larger catheters designed for epidural use are associated with relatively high complication rates when placed subarachnoid.

51 Spinal Anesthesia  Midline, paramedian, or prone approach  Two "pops" are felt:  ligamentum flavum  dura–arachnoid membrane  Successful dural puncture confirmed by free flow of CSF  Persistent paresthesia or pain upon injection  withdraw and redirect  Aspiration of CSF may be necessary in certain cases:  presence of low CSF pressure (dehydrated patient)  prone position

52 Which of the following statements is FASLE?  A. A patient in the sitting position will have a higher block if the solution is hypobaric and the patient remains erect.  B. A patient placed supine and in the Trendelenburg position is at high risk for developing a total spinal block after injection of an isobaric solution.  C. A patient in the prone jackknife position should not have a hyperbaric solution injected.  D. The normal lumbar lordosis limits the spread of hyperbaric solution is a supine patient.

53 Answer  B.  An isobaric solution should not ascend to cause a total spinal regardless of the patient’s position.

54 Factors Affecting the Level of Spinal Anesthesia  Baricity  Position of the patient  During and immediately after injection  Dosage  Site of injection  Baricity  Position of the patient  During and immediately after injection  Dosage  Site of injection  Age  CSF  Curvature of the spine  Drug volume  Intraabdominal pressure  Needle direction  Patient height  Pregnancy  Age  CSF  Curvature of the spine  Drug volume  Intraabdominal pressure  Needle direction  Patient height  Pregnancy Most Important FactorsOther Factors

55 Baricity 101  A hyperbaric solution of local anesthetic is denser (heavier) than CSF  Addition of glucose  Hypobaric solution is less dense (lighter) than CSF  Addition of sterile water  Head-down position  Hyperbaric solution - spreads cephalad  Hypobaric anesthetic solution - moves caudad  A head-up position  Hyperbaric solution - settles caudad  Hypobaric solution - ascends cephalad  Lateral position  Hyperbaric spinal solution - greater effect on dependent (down) side  Hypobaric solution - higher level on nondependent (up) side  Isobaric solution tends to remain at the level of injection

56 Baricity 101  Hyperbaric solutions tend to move to the most dependent area of the spine  T4–T8 in the supine position  Apex of the thoracolumbar curvature is T4  In the supine position, this should limit a hyperbaric solution to produce a level of anesthesia at or below T4  Abnormal curvatures of the spine, such as scoliosis and kyphoscoliosis, have multiple effects on spinal anesthesia  Difficult landmarks  Decreased CSF

57 Baricity 101  CSF has a specific gravity of 1.003–1.008 at 37°C

58 Spinal Anesthesia  CSF volume inversely correlates with level of anesthesia  Increased intraabdominal pressure or conditions that cause engorgement of the epidural veins, thus decreasing CSF volume, are associated with higher blocks  Pregnancy  Ascites  Large abdominal tumors  Conflicting opinion exists as to whether increased CSF pressure caused by coughing or straining, or turbulence on injection has any effect on the spread of LA

59 Spinal Agents  Only preservative-free solutions used  Addition of vasoconstrictors (epi or neo) and opioids may enhance the quality and/or prolong the duration of spinal anesthesia

60 Spinal Agents  Hyperbaric bupivacaine and tetracaine are two of the most commonly used agents for spinal  Relatively slow in onset (5–10 min)  Prolonged duration (90–120 min)  Similar sensory levels  Tetracaine more motor blockade  Addition of epi to bupivacaine prolongs its duration only modestly  In contrast, epi to tetracaine prolongs by more than 50%  Phenylephrine also prolongs tetracaine anesthesia but has no effect on bupivacaine  Ropivacaine  Experience with spinals is more limited  A 12-mg intrathecal dose of ropivacaine is roughly equivalent to 8 mg of bupivacaine, but it appears to have no particular advantages for spinal anesthesia

61 Spinal Agents  Lidocaine and procaine  rapid onset (3–5 min) and short duration of action (60–90 min)  modest if any prolonged effect with epi  Lidocaine associated with transient neurological symptoms (TNS) and cauda equina syndrome  TNS: back pain radiating to the legs without sensory or motor deficits after resolution of spinal resolves spontaneously within several days  Some experts suggest that lidocaine can be safely used as a spinal anesthetic if the total dose is limited to 60 mg and diluted to 2.5% or less

62 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

63 Epidural Anesthesia  The epidural space surrounds the dura mater posteriorly, laterally, and anteriorly  Contents of Epidural Space:  Nerve roots  Fatty connective tissue  Lymphatics  Rich venous (Batson's) plexus  Septa or connective tissue bands  Epidural anesthesia is slower in onset (10–20 min) and may not be as dense as a spinal  Can cause a pronounced differential or segmental block that can be useful clinically  Relatively dilute concentrations of a LA combined with an opioid:  Block the smaller sympathetic and sensory fibers and spare the larger motor fibers = analgesia without motor block  Segmental block – LA not readily spread by CSF so confined close to level it was injected  Characterized by a well-defined band of anesthesia at certain nerve roots  Nerve roots above and below are not blocked  Ex. thoracic epidural

64 Epidural Needles  Typically 17–18 gauge  9cm to hub  Tuohy needle most commonly used  Blunt bevel with a gentle curve of 15–30° at the tip  Pushes away the dura after passing through the ligamentum flavum instead of penetrating it  Straight needles without a curved tip (Crawford needles) may have a higher incidence of dural puncture but facilitate passage of an epidural catheter.  Needle modifications include winged tips and introducer devices set into the hub designed for guiding catheter placement.

65 Epidural Catheters  Continuous infusion or intermittent boluses  May allow a lower total dose of anesthetic to be used  Intraop and/or postop analgesia  19- or 20-gauge catheter is introduced through a 17- or 18-gauge epidural needle  Bevel opening directed either cephalad or caudad, and catheter advanced 2–6 cm  The shorter the distance advanced:  more likely it is to become dislodged  The further the catheter is advanced:  greater the chance of a unilateral block exiting the epidural space via an intervertebral foramen coursing into the anterolateral recesses  Single port at the distal end or multiple side ports close to a closed tip  Some have a stylet for easier insertion  Spiral wire-reinforced catheters are very resistant to kinking  The spiral or spring tip is associated with fewer, less intense paresthesias and may be associated with a lower incidence of inadvertent intravascular insertion

66 Epidural Techniques  LOR technique most commonly used  Needle advanced through subQ tissues with the stylet in place  Once interspinous ligament entered (increase in tissue resistance), stylet removed  Glass syringe filled with approximately 2 mL of fluid or air is attached  If tip of needle is within the ligament, gentle attempts at injection are met with resistance  Needle slowly advanced, millimeter by millimeter, with either continuous or rapidly repeating attempts  As tip enters the epidural space there is a sudden LOR and injection is easy  Hanging Drop Technique http://www.youtube.com/watch?v=7kDi47vqBis  Variation of Hanging Drop Technique http://www.youtube.com/watch?v=TvCBDamF4jQ&feature=related

67 Activating an Epidural  Quantity LA for epidural anesthesia is very large compared to spinals  Significant toxicity can occur if injected intrathecally or intravascularly  Safeguards against this: epidural test dose and incremental dosing  Test dose detects both subarachnoid and IV injection  Classic test dose: 3mL of 1.5% lidocaine with 1:200,000 epinephrine (5mcg/mL)  45mg of lidocaine injected intrathecally – rapidly apparent spinal anesthesia  15 mcg of epinephrine injected intravascularly – noticeable increase in heart rate (20% or more) with or without hypertension  False positives (uterine contraction causing pain or an increase in heart rate coincident to test dosing)  False negatives (patients taking beta blockers)  25% or more increase in T-wave amplitude on EKG may be more reliable sign of IV injection  Both fentanyl and larger doses of local anesthetic without epinephrine have been advocated as intravenous injection test doses  Simply aspirating prior to injection – insufficient to avoid inadvertent IV injection

68 Activating an Epidural  Incremental dosing is a very effective method of avoiding serious complications  Fraction of the total intended LA dose, typically 5 mL  Should be large enough for mild symptoms of IV injection to occur but small enough to avoid seizure or cardiovascular compromise.  If a clinician uses an initial test dose, is diligent about aspirating prior to each injection, and always uses incremental dosing, significant systemic toxicity or inadvertent intrathecal injections are rare.

69 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

70 When using a caudal approach to the epidural space, which of the following is TRUE?  A. The patient must be prone.  B. An inadvertent subarachnoid block is much less likely than when using the lumbar approach.  C. The technique becomes relatively more contraindicated as the patient’s age decreases.  D. Small volumes of agent are needed since the volume of the canal is only 8-12ml.  E. The needle enters through the sacral hiatus.

71 Answer  E.  Canal is of low volume but there is leakage through the foramina requiring injection of a larger volume compared to the lumbar approach.  Pt can be prone or lateral decubitus.  Inadvertent dural puncture is very possible.  Caudal approach is technically easier than lumbar approach in babies, and is becoming increasingly more popular in pediatric anesthesia.

72 Caudal Anatomy  Caudal space is considered the sacral portion of the epidural space  Sacral vertebrae fuse into one large bone – the sacrum  Each one retains discrete anterior and posterior intervertebral foramina  Laminae of S5 and all or part of S4 normally do not fuse, leaving a caudal opening to the spinal canal, the sacral hiatus  Sacrococcygeal ligament covers the sacral hiatus

73 Caudal Anatomy  Hiatus felt as a as a groove or notch above the coccyx and between two bony prominences – the sacral cornua  More easily appreciated in infants and children  Posterior superior iliac spines and the sacral hiatus define an equilateral triangle

74 Caudal Epidural Anesthesia  One of the most commonly used regional techniques in pediatric patients  Used in anorectal surgery in adults  2 nd stage of labor  In children - typically combined with GENA for intraop supplementation and postop analgesia  Performed after induction  Commonly used for procedures below the diaphragm  urogenital, rectal, inguinal, and lower extremity  Within the sacral canal, the dural sac extends to…what level?  S2 in adults  S3 in infants  Makes inadvertent intrathecal injection much more common in infants

75 Caudal Epidural Technique  Position lateral or prone with one or both hips flexed  Palpate sacral hiatus  Sterile skin prep  Needle advanced at a 45° angle cephalad until a pop is felt (sacrococcygeal ligament)  Angle flattened and advanced  Aspirate for blood and CSF  If negative, proceed with injection  Test dose vs incremental dosing with frequent aspiration

76 Caudal Anesthesia  Complication rate for "kiddie caudals" is very low  Total spinal and IV injection causing seizure or cardiac arrest  Intraosseous injection has also been reported to cause systemic toxicity  Calcification of the sacrococcygeal ligament may make caudal anesthesia difficult or impossible in older adults

77 Pediatric Caudal Anesthesia  Dose: 0.5–1.0 mL/kg of 0.125–0.25% bupivacaine (or ropivacaine) +/- epi  Opioids may be added (ex 50–70 mcg/kg of morphine)  not recommended for outpatients - delayed respiratory depression  Duration can extend for hours into the postop period  Ok to d/c home even with mild residual motor block or without urinating  most children will urinate within 8 h  Higher epidural levels can be accomplished with catheters threaded cephalad into the lumbar or even thoracic epidural space

78 Caudal in Adults  Dense sacral sensory blockade with limited cephalad spread for anorectal procedures  Prone jackknife position  Dose 15–20 mL of 1.5–2.0% lidocaine +/- epi  Fentanyl 50–100 mcg may also be added

79 Outline  Anatomy  Mechanism of Action  Systemic Manifestations  Indications/Contrandications  Anticoagulants/Antiplatelets  Anatomic Approaches  Spinal Anesthesia  Epidural Anesthesia  Caudal Anesthesia  Complications

80 All of the following statements regarding complications associated with epidural and spinal anesthesia are true EXCEPT:  A. Use of fluid instead of air for LOR during epidural anesthesia reduces the risk of headache upon accidental dural puncture.  B. An epidural blood patch immediately relieves PDPH symptoms in 99% of pts.  C. Transient reduction in hearing acuity after spinal anesthesia is more common in female than in male patients.  D. Back pain is more common after epidural anesthesia than after spinal anesthesia.  E. Neurologic injury occurs in about 0.03% to 0.1% of all central neuraxial blocks.

81 Answer  B  90% not 99%

82 All of the following statements regarding spinal or epidural anesthesia and spinal hematoma are true EXCEPT:  A. Pts taking NSAIDS and receiving mini dose heparin are not at increased risk.  B. Pts treated with enoxaparin are at increased risk.  C. Pts most commonly present with numbness or lower extremity weakness.  D. Spinal hematoma occurs at an estimated incidence of less than 1:150,000.  E. The removal of an epidural or an intrathecal catheter presents nearly as great a risk for spinal hematoma as its insertion.

83 Answer  A  Combination may put patients at increased risk.

84 Adverse or exaggerated physiological responses  Urinary retention  High block  Total spinal anesthesia  Cardiac arrest  Anterior spinal artery syndrome  Horner's syndrome Adverse or exaggerated physiological responses  Urinary retention  High block  Total spinal anesthesia  Cardiac arrest  Anterior spinal artery syndrome  Horner's syndrome Complications related to needle/catheter placement  Trauma  Backache  Dural puncture/leak  Postdural puncture headache  Diplopia  Tinnitus  Neural injury  Nerve root damage  Spinal cord damage  Cauda equina syndrome  Bleeding  Intraspinal/epidural hematoma  Misplacement  No effect/inadequate anesthesia  Subdural block  Inadvertent subarachnoid block 1  Inadvertent intravascular injection  Catheter shearing/retention  Inflammation  Arachnoiditis  Infection  Meningitis  Epidural abscess Complications related to needle/catheter placement  Trauma  Backache  Dural puncture/leak  Postdural puncture headache  Diplopia  Tinnitus  Neural injury  Nerve root damage  Spinal cord damage  Cauda equina syndrome  Bleeding  Intraspinal/epidural hematoma  Misplacement  No effect/inadequate anesthesia  Subdural block  Inadvertent subarachnoid block 1  Inadvertent intravascular injection  Catheter shearing/retention  Inflammation  Arachnoiditis  Infection  Meningitis  Epidural abscess Drug toxicity  Systemic local anesthetic toxicity  Transient neurological symptoms  Cauda equina syndrome Drug toxicity  Systemic local anesthetic toxicity  Transient neurological symptoms  Cauda equina syndrome

85 THE END


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