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: D. Boundaries of Epidural Space: Posterior: Anterior: Lateral: ligamentum flavum/vertebral laminaeAnterior:posterior longitudinal ligamentLateral:vertebral pedicles/intervertebral foraminaInferior:sacrococcygeal ligament covering sacral hiatusSuperior:foramen magnum
6 Vertebral Column 7 cervical vertebrae 12 thoracic vertebrae 5 lumbar vertebrae5 fused sacral vertebraeRudimentary coccygeal vertebraePaired spinal nerves exit at each level, C1 to S5At cervical levelnerves arise above respective vertebraeStarting at T1nerves exit below their vertebraeAs a result…8 cervical nerve roots but only 7 cervical vertebrae
7 Spinal Canal Contains: Subdural space Spinal cord Meninges (3 layers) Pia MaterArachnoid MaterDura MaterFatty tissueVenous plexusCSFSubdural spacePoorly demarcated, potential space that exists between the dura and arachnoid membranes-The pia mater is closely adherent to the spinal cord, whereas the arachnoid mater is usually closely adherent to the thicker and denser dura mater.-CSF is contained between the pia and arachnoid maters in the subarachnoid space-The epidural space is a better defined potential space within the spinal canal that is bounded by the dura and the ligamentum flavum
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 AnatomyThe spinal cord extends from the foramen magnum to the level of L1 in adultsIn infants, the spinal cord ends at L3 and moves up as they grow olderLower nerve roots course some distance before exiting the intervertebral foraminaForms the cauda equinaPushing vs piercing the cordThe dural sac, subarachnoid and subdural spaces usually extend to S2 in adultsOften to S3 in children-Because the spinal cord normally ends at L1-Therefore, performing a spinal below L1 in an adult (L3 in a child) avoids potential needle trauma to the cord; damage to the cauda equina is unlikely as these nerve roots float in the dural sac and tend to be pushed away (rather than pierced) by an advancing needle.-Because of this fact and the smaller body size, caudal anesthesia carries a greater risk of subarachnoid injection in children than in adults. An extension of the pia mater, the filum terminale, penetrates the dura and attaches the terminal end of the spinal cord (conus medullaris) to the periostium of the coccyx
11 Blood Supply Anterior 2/3 of cord Anterior spinal artery vertebral arteryPosterior 1/3 of cordTwo posterior spinal arteriesposterior inferior cerebellar arteriesRadicular arteriesintercostal arteries in the thoraxlumbar arteries in the abdomenThe artery of AdamkiewiczAortaTypically unilateral and on the ___ side?LeftMajor blood supply to the anterior, lower 2/3 of the spinal cordInjury to this artery can result in …?Anterior spinal artery syndrome
12 Pain, temp loss (at and below lesion) and motor paralysis (below lesion)Urinary incontinence
14 Mechanism of Action Principal site of action - nerve root Local anesthetic bathes the nerve root in thesubarachnoid space or epidural spaceSpinal anesthesia:Direct injection of LA into CSFRelatively small dose and volume to achievedense sensory and motor blockadeEpidural/Caudal anesthesia:Same LA concentration is achieved at nerve roots only with much higher volumes and quantitiesLevel for epidural anesthesiaMust be close to the nerve roots that are to be anesthetized
15 Somatic BlockadeSensory blockade interrupts both somatic and visceral painful stimuliMotor blockade produces skeletal muscle relaxationProvides excellent OR conditionsLA effect on nerve fibers varies according to many factors:Size of the nerve fiberMyelinationConcentration achievedDuration of contactSmaller and myelinated fibers are more easily blockedThis, and the fact that the concentration of local anesthetic decreases with increasing distance from the level of injection, explains the phenomenon of differential blockade.
16 Somatic BlockadeSpinal nerve roots contain varying mixtures of these fiber types and they vary in their sensitivity to the LA blockadeThis results in a differential blockWhich nerve fibers are blocked by the lowest sensitivity to LA?A. painB. motorC. sympatheticD. touchOrder of sensitivity:Sympathetic > pain > touch > motor
17 Somatic Blockade Sympathetic block is highest, generally 2 (up to 6) segmentshigher than the sensory block(pain, light touch)Which in turn is usually 2-3segments higher than themotor blockade
18 Autonomic Blockade Block of efferent autonomic transmission sympathetic and some parasympathetic blockadeSympathetic outflow from the spinal cordThoracolumbarSympathetic preganglionic nerve fibersexit the spinal cord with the spinal nerves from T1 to the L2 level andmay course many levels along sympathetic chain before synapsing with a postganglionic cell in a sympathetic gangliaParasympathetic outflowCraniosacralParasympathetic preganglionic fibers exit the spinal cord with the cranial and sacral nervesNeuraxial anesthesia does not block the vagus nervedecreased sympathetic tone and/or unopposed parasympathetic tonephysiological responses of neuraxial blockade therefore result from decreased sympathetic tone and/or unopposed parasympathetic tone.
20 A pt receives a spinal anesthetic with a sensory level of T5 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 AnswerELevel 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 contractilityGenerally proportional to degree of the sympathectomyArterial and venous smooth muscle vasomotor tone:Innervated by sympathetic fibers from T5 to L1Blocking these nerves causes:vasodilation of the venous capacitance vesselspooling of blooddecreased venous return to the heartArterial vasodilation may also decrease SVRMay be minimized by compensatory vasoconstriction above the level of the block
23 Cardiovascular Manifestations A high sympathetic blockprevents compensatory vasoconstrictionblocks the sympathetic cardiac accelerator fibersthat arise at …?T1–T4Profound hypotension may occurVasodilation combined with bradycardia and decreased contractilityExaggerated if venous return is further compromisedhead-up position or gravid uterusSudden cardiac arrest sometimes seen with spinal anesthesiaUnopposed vagal tone
24 Cardiovascular Manifestations Steps to minimize the degree of hypotension:Volume loading with 10–20 mL/kg of IVFpartially compensates for the venous poolingLUD in the third trimester of pregnancyminimizes obstruction to venous returnHypotension may still occurIncrease IVFsAutotransfusion - head-down positionVasopressors (phenylephrine/ephedrine)Excessive or symptomatic bradycardiaAtropineIf profound hypotension and/or bradycardia persistEpinephrine (5–10 mcg)
25 Pulmonary Manifestations Usually are minimaldiaphragm innervated by the phrenic nervewith fibers originating from C3–C5Even with high thoracic levels…tidal volume is unchangedonly a small decrease in vital capacityfrom loss of abdominal muscles' contribution to forced expirationPhrenic nerve block may not occur even with total spinal anesthesiaapnea often resolves with hemodynamic resuscitationsuggests that brain stem hypoperfusion is responsible
26 Pulmonary Manifestations Severe chronic lung disease patientsRely upon accessory muscles of respirationCoughing and clearing of secretions require these musclesHigh levels of neural blockade impair these musclesUse caution in patients with limited respiratory reserveMust weigh against the advantages of avoiding airway instrumentation and PPVSurgery above the umbilicusPure regional technique may not bethe best choiceIntercostal and abdominal(with dilute local anesthetics and opioids) in the postoperative period, particularly following upper abdominal or thoracic surgery.
27 Pulmonary Manifestations Thoracic or upper abdominal surgeryDecreased diaphragmatic function postopDecreased FRCAtelectasis and hypoxia via V/P mismatchPostop thoracic epidural analgesia may improve pulmonary outcomedecrease the incidence ofpneumonia and respiratory failureimprove oxygenationdecrease duration of ventsupport
28 GI Manifestations Sympathetic outflow originates at T5–L1 Sympathectomy - vagal tone dominancesmall, contracted gut with active peristalsisExcellent operative conditions for lap procedures when used as an adjunct to GENAPostoperative epidural analgesia has been shown to hasten return of GI functionHepatic blood flow will decrease with reductionsin MAP from any anesthetic techniqueIntraabdominal surgery - decrease in hepaticperfusion related more to surgical manipulationthan to anesthetic technique.
29 Urinary Tract Manifestations Renal blood flow – maintained through autoregulationlittle clinical effect upon renal functionNeuraxial anesthesia at the lumbar and sacral levels blocks both sympathetic and parasympathetic control of bladder functionLoss of autonomic bladder control results in urinaryretention until the block wears offIf no urinary catheter is anticipated perioperatively:use the shortest acting and smallest amount ofLA necessary for the procedurelimit the amount of IVF as much as possibleMonitored pt for urinary retention to avoidbladder distention following neuraxial anesthesia
30 Metabolic & Endocrine Manifestations Surgical trauma produces a neuroendocrine responselocalized inflammatory responseactivation of somatic and visceral afferent nerve fibersincreases in ACTH, cortisol, epinephrine, NE, and vasopressinactivation of the renin–angiotensin–aldosterone systemClinical manifestations:HTN, tachycardia, hyperglycemia, protein catabolism, suppressed immune responses, and altered renal functionNeuraxial blockade can partially suppress (during major invasive surgery) or totally block (during lower extremity surgery) this stress responseReduction in catecholamine releasemay decrease perioperative arrhythmias and reduce the incidence of ischemiaNeuraxial block should precede incision and extend postop
32 Indications for Neuraxial Used alone or in conjunction with GENA for mostprocedures below the neckMost useful for:lower abdominalinguinalurogenitalrectallower extremity surgeryLumbar spinal surgery may also be performedunder spinal anesthesiaUpper abdominal proceduresdifficult to achieve a sensory level adequate for patient comfort yet avoid the complications of a high blockSpinal anesthesia for neonatal surgery
33 Contrandications Absolute Relative Controversial Coagulopathy or other bleeding diathesisInability to communicate with ptInfection at the site of injectionPreexisting neurological deficitsPatient refusalSepsisAbsoluteRelativeControversialPatient refusalInfection at the site of injectionCoagulopathy or other bleeding diathesisSevere hypovolemiaIncreased intracranial pressureSevere aortic stenosisSevere mitral stenosisPreexisting neurological deficitsSepsisUncooperative patientDemyelinating lesionsStenotic valvular heart lesionsSevere spinal deformityInability to communicate with ptPrior back surgery at site of injectionComplicated surgeryProlonged operationMajor blood lossManeuvers that compromise respirationBarash lists pt refusal as the only ABSOLUTE contra.Sepsis/infxn at site increase risk for meningitis
35 Oral Anticoagulants Long-term warfarin therapy Must be stoppedNeed PT/INR to be normalizedPerioperative thromboembolic prophylaxisIf initial dose given > 24 h prior to the block or if more than one dose was givenPT and INR need to be checkedIf only one dose given within 24 hSafeRemoving an epidural catheter from patients receiving low- dose warfarin (5 mg/d)
36 Antiplatelets Aspirin and NSAIDs More potent agents Alone don’t appear to increase risk of spinal hematomaMore potent agentsTiclopidine (Ticlid)14 daysClopidogrel (Plavix)7 daysAbciximab (Rheopro)48 hEptifibatide (Integrilin)8 h
37 Unfractionated Heparin Minidose subQ prophylaxisOK to proceedPatients to receive heparin intraoperatively1 h or more before heparin administrationA bloody epidural or spinal does not necessarily require cancellation of surgerydiscussion of the risks with the surgeoncareful postoperative monitoring neededRemoval of an epidural catheter1 h prior to dosingor 4 h following dosingPatients on therapeutic doses of heparin (elevated PTT)Avoid neuraxialThe 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 1993Reports of spinal hematomas associatedwith neuraxial anesthesiaMany involved intraop or early postop use,and several also taking antiplateletsIf bloody needle or catheter placement occursDelay until 24 hrs postopPostop LMWH thromboprophylaxis if epidural catheter in placeRemove 2 hrs prior to the first doseOr 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.
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 AnswerD.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 – horizontalNeedle directed with only a slight cephalad angleThoracic spine – slant in a caudal direction and can overlapNeedle angled significantly more cephaladFirst palpable cervical spinous process is C2Most prominent is…?C7Inferior tip of the scapula at level of …?Spinous process of T7Highest points of both iliac crests (Tuffier's line) ?Body of L4 or the L4–L5 interspacePosterior superior iliac spineS2 posterior foraminaSacral hiatusDepression just above or between the gluteal clefts and above the coccyx
45 Midline ApproachBody positioned with the plane of the back perpendicular to the floorPalpate for depression between the spinous processes of the vertebra above and below the level to be usedSubcutaneous tissues offer little feeling of resistanceSupraspinous and interspinous ligaments felt as an increase in tissue densityIf bone contacted superficiallyneedle is likely hitting..?the lower spinous processIf bone contacted at a deeper depthand needle is in the midline it is likely hitting…?the upper spinous processor if it is lateral to the midline it is likely hitting…?a laminaLigamentum flavum - obvious increase in resistanceAt this point, spinal and epidural anesthesia differ
46 Paramedian Approach May be useful in certain patients severe arthritiskyphoscoliosisprior lumbar spine surgery2 cm lateral to the inferior aspect of superior spinous processPenetrates the paraspinous muscleslateral to the interspinous ligamentsneedle may encounter little resistance initially and may not seem to be in firm tissueNeedle advanced at a 10–25° angle toward the midlineLOR is often more subtle than with the midline approach
47 Bone at a shallow depth Bone encountered deep medial part of the lower laminaredirect mostly upward and slightly more lateralBone encountered deeplateral part of the lower laminaredirected only slightly upward, more toward the midlineA needle that encounters bone at a shallow depth (a) is usually hitting the medial lamina, whereas one that encounters bone deeply (b) is further lateral from the midline. Posterior view
49 Spinal NeedlesAvailable in an array of sizes (16–30 gauge), lengths, and bevel and tip designsTightly fitting removable styletavoids tracking epithelial cells into the subarachnoid space2 broad groups1. Sharp (cutting)-tippedQuincke needle is a cutting needle withend injection2. Blunt tip (pencil-point) needlesWhitacre – rounded point with side injectionSprotte – rounded point with long side openingmarkedly decreased the incidence of PDPH-Sprotte - it has the advantage of more vigorous CSF flow compared with similar gauge needles. However, this can lead to a failed block if the distal part of the opening is subarachnoid (with free flow CSF), the proximal part is not past the dura, and the full dose of medication is not delivered.-In general the smaller the gauge needle the lower the incidence of headache.
50 Spinal CathetersVery small subarachnoid catheters are currently no longer approved in the USAssociation 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 flavumdura–arachnoid membraneSuccessful dural puncture confirmed by free flow of CSFPersistent paresthesia or pain upon injectionwithdraw and redirectAspiration 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 AnswerB.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 Most Important FactorsOther FactorsBaricityPosition of the patientDuring and immediately after injectionDosageSite of injectionAgeCSFCurvature of the spineDrug volumeIntraabdominal pressureNeedle directionPatient heightPregnancyLA specific gravity relative to CSF LA (baricity)
55 Baricity 101A hyperbaric solution of local anesthetic is denser (heavier) than CSFAddition of glucoseHypobaric solution is less dense (lighter) than CSFAddition of sterile waterHead-down positionHyperbaric solution - spreads cephaladHypobaric anesthetic solution - moves caudadA head-up positionHyperbaric solution - settles caudadHypobaric solution - ascends cephaladLateral positionHyperbaric spinal solution - greater effect on dependent (down) sideHypobaric solution - higher level on nondependent (up) sideIsobaric solution tends to remain at the level of injection
56 Baricity 101Hyperbaric solutions tend to move to the most dependent area of the spineT4–T8 in the supine positionApex of the thoracolumbar curvature is T4In the supine position, this should limit a hyperbaric solution to produce a level of anesthesia at or below T4Abnormal curvatures of the spine, such as scoliosis and kyphoscoliosis, have multiple effects on spinal anesthesiaDifficult landmarksDecreased CSFPlacing the block becomes more difficult because of the rotation and angulation of the vertebral bodies and spinous processes. Finding the midline and the interlaminar space may be difficult.Severe kyphosis or kyphoscoliosis can also be associated with a decreased volume of CSF and often results in a higher than expected level, particularly with a hypobaric technique or rapid injection.
57 Baricity 101 CSF has a specific gravity of 1.003–1.008 at 37°C Agent Bupivacaine0.5% in 8.25% dextrose1.0227–1.02780.5% plain0.9990–1.0058Lidocaine2% plain1.0004–1.00665% in 7.5% dextrose1.0262–1.0333Procaine10% plain1.01042.5% in water0.9983Tetracaine0.5% in water0.9977–0.99970.5% in D5W1.0133–1.0203
58 Spinal AnesthesiaCSF volume inversely correlates with level of anesthesiaIncreased intraabdominal pressure or conditions that cause engorgement of the epidural veins, thus decreasing CSF volume, are associated with higher blocksPregnancyAscitesLarge abdominal tumorsConflicting opinion exists as to whetherincreased CSF pressure caused bycoughing or straining, or turbulenceon injection has any effect on the spread of LA
59 Spinal Agents Only preservative-free solutions used DrugPreparationDOA (plain)DOA (w/epi)Procaine10% solution4560Bupivacaine0.75% in 8.25%dextrose90-120Tetracaine1% solution in 10%glucoseLidocaine5% in 7.5%glucose(dilute to 2.5% or less)60-7560-90Ropivacaine0.2-1%solution(Off-label use)back pain radiating to the legs without sensory or motor deficits, occurring after the resolution of spinal block and resolving spontaneously within several daysOnly preservative-free solutions usedAddition of vasoconstrictors (epi or neo) and opioids may enhance the quality and/or prolong the duration of spinal anesthesia
60 Spinal AgentsHyperbaric bupivacaine and tetracaine are two of the most commonly used agents for spinalRelatively slow in onset (5–10 min)Prolonged duration (90–120 min)Similar sensory levelsTetracaine more motor blockadeAddition of epi to bupivacaine prolongs its duration only modestlyIn contrast, epi to tetracaine prolongs by more than 50%Phenylephrine also prolongs tetracaine anesthesia but has no effect on bupivacaineRopivacaineExperience with spinals is more limitedA 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 epiLidocaine associated with transient neurological symptoms (TNS) and cauda equina syndromeTNS: back pain radiating to the legs without sensory or motor deficits after resolution of spinalresolves spontaneously within several daysSome 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
63 Epidural AnesthesiaThe epidural space surrounds the dura mater posteriorly, laterally, and anteriorlyContents of Epidural Space:Nerve rootsFatty connective tissueLymphaticsRich venous (Batson's) plexusSepta or connective tissue bandsEpidural anesthesia is slower in onset (10–20 min) and may not be as dense as a spinalCan cause a pronounced differential or segmental block that can be useful clinicallyRelatively 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 blockSegmental block – LA not readily spread by CSF so confined close to level it was injectedCharacterized by a well-defined band of anesthesia at certain nerve rootsNerve roots above and below are not blockedEx. thoracic epidural
64 Epidural Needles Typically 17–18 gauge 9cm to hub Tuohy needle most commonly usedBlunt bevel with a gentle curve of15–30° at the tipPushes away the dura after passing through the ligamentum flavum instead of penetrating itStraight 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 usedIntraop and/or postop analgesia19- or 20-gauge catheter is introduced through a 17- or 18-gauge epidural needleBevel opening directed either cephalad or caudad, and catheter advanced 2–6 cmThe shorter the distance advanced:more likely it is to become dislodgedThe further the catheter is advanced:greater the chance of a unilateral blockexiting the epidural space via an intervertebral foramencoursing into the anterolateral recessesSingle port at the distal end or multiple side ports close to a closed tipSome have a stylet for easier insertionSpiral wire-reinforced catheters are very resistant to kinkingThe 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 placeOnce interspinous ligament entered (increase in tissue resistance), stylet removedGlass syringe filled with approximately 2 mL of fluid or air is attachedIf tip of needle is within the ligament, gentle attempts at injection are met with resistanceNeedle slowly advanced, millimeter by millimeter, with either continuous or rapidly repeating attemptsAs tip enters the epidural space there is a sudden LOR and injection is easyHanging Drop TechniqueVariation of Hanging Drop Technique
67 Activating an Epidural Quantity LA for epidural anesthesia is very large compared to spinalsSignificant toxicity can occur if injected intrathecally or intravascularlySafeguards against this: epidural test dose and incremental dosingTest dose detects both subarachnoid and IV injectionClassic test dose: 3mL of 1.5% lidocaine with 1:200,000 epinephrine (5mcg/mL)45mg of lidocaine injected intrathecally – rapidly apparent spinal anesthesia15 mcg of epinephrine injected intravascularly – noticeable increase in heart rate (20% or more) with or without hypertensionFalse 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 injectionBoth fentanyl and larger doses of local anesthetic without epinephrine have been advocated as intravenous injection test dosesSimply aspirating prior to injection – insufficient to avoid inadvertent IV injection
68 Activating an Epidural Incremental dosing is a very effective method of avoiding serious complicationsFraction of the total intended LA dose, typically 5 mLShould 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.
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 AnswerE.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 AnatomyCaudal space is considered the sacral portion of the epidural spaceSacral vertebrae fuse into one large bone – the sacrumEach one retains discrete anterior and posterior intervertebral foraminaLaminae of S5 and all or part of S4 normally do not fuse, leaving a caudal opening to the spinal canal, the sacral hiatusSacrococcygeal ligament covers the sacral hiatus
73 Caudal AnatomyHiatus felt as a as a groove or notch above the coccyx and between two bony prominences – the sacral cornuaMore easily appreciated in infants and childrenPosterior superior iliac spines and the sacral hiatus define an equilateral triangle
74 Caudal Epidural Anesthesia One of the most commonly used regionaltechniques in pediatric patientsUsed in anorectal surgery in adults2nd stage of laborIn children - typically combined with GENAfor intraop supplementation and postop analgesiaPerformed after inductionCommonly used for procedures below the diaphragmurogenital, rectal, inguinal, and lower extremityWithin the sacral canal, the dural sac extends to…what level?S2 in adultsS3 in infantsMakes inadvertent intrathecal injection much more common in infants
75 Caudal Epidural Technique Position lateral or prone with one or both hips flexedPalpate sacral hiatusSterile skin prepNeedle advanced at a 45° angle cephalad until a pop is felt (sacrococcygeal ligament)Angle flattened and advancedAspirate for blood and CSFIf negative, proceed with injectionTest 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 arrestIntraosseous injection has also been reported to cause systemic toxicityCalcification of the sacrococcygeal ligament may make caudalanesthesia difficult or impossiblein older adults
77 Pediatric Caudal Anesthesia Dose: 0.5–1.0 mL/kg of 0.125–0.25% bupivacaine(or ropivacaine) +/- epiOpioids may be added (ex 50–70 mcg/kg of morphine)not recommended for outpatients - delayed respiratory depressionDuration can extend for hours into the postop periodOk to d/c home even with mild residual motor block or without urinatingmost children will urinate within 8 hHigher epidural levels can be accomplished withcatheters threaded cephalad into the lumbar oreven thoracic epidural space
78 Caudal in AdultsDense sacral sensory blockade with limited cephalad spread for anorectal proceduresProne jackknife positionDose 15–20 mL of 1.5–2.0% lidocaine +/- epiFentanyl 50–100 mcg may also be added
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.
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 AnswerACombination may put patients at increased risk.
84 Complications related to needle/catheter placement TraumaBackacheDural puncture/leakPostdural puncture headacheDiplopiaTinnitusNeural injuryNerve root damageSpinal cord damageCauda equina syndromeBleedingIntraspinal/epidural hematomaMisplacementNo effect/inadequate anesthesiaSubdural blockInadvertent subarachnoid block1Inadvertent intravascular injectionCatheter shearing/retentionInflammationArachnoiditisInfectionMeningitisEpidural abscessAdverse or exaggerated physiological responsesUrinary retentionHigh blockTotal spinal anesthesiaCardiac arrestAnterior spinal artery syndromeHorner's syndromebothersome to the crippling and life-threateningBroadly categorizedDrug toxicitySystemic local anesthetic toxicityTransient neurological symptomsCauda equina syndrome