-causes less discomfort during placement
-requires less local anesthetic
-produces more intense sensory and motor block
-correct placement of needle confirmed by backflow of CSF
-a lower incidence of systemic hypotension
-the ability to produce a segmental sensory block
-greater control over the intensity of sensory anesthesia and motor block achieved by adjustment of LA concentration
-the routine placement of catheters for epidural anesthesia imparts additional benefit by allowing titration of the block tot he duration of surgery
-Catheter allows long-term administration of LA or opioid-containing solutions (or both
-contains spinal cord and nerve roots
-has little effect on the spread of LA solutions in the epidural space
-the posterior arch is created by fusion of lateral cylindrical pedicles with two flattened posterior laminae
-a transverse process extends out laterally at each junction of the pedicale and laminae
-a single spinous process projects posteriorly from the juntio of the two laminae.
-each pedicle is notched on its superior and inferior surfaces, and when two adjacent vertebrae are articulated, these notches form the intervertebral foramina through which the spinal nerves emerge
thus the sacrum and coccyx are dital extensions of the vertebral column, and the sacral canal is a continuouation of the vertebral canal through the sacrum.
Epidrual fat –> Dura mater/arachnoid (“pop) –> Spinal
1. iliac crest
2. bony knob at the lower end of the neck
3. lower wing of the scapula
4. Posterior superior iliac spine
-b/c of disproportionate growth of neural tissue and the vertebral canal, the spinal cord generally terminates around the third lumbar vertebra at birth and at the lower border of the first lumbar vertebra in adults
where does it begin in newborns? adults?
-nerve roots of the cauda equine move relatively freely within the CSF, a fortunate arrnagment that permits them to be displaced rather than pierced by and advancing needle
newborn – conus at L3 vertebra body
Adult – conus at L1 vertebra body
2. Arachnoid – closely adherent to the inner surface of the dura
3. Pia – innermost layer
1. originates where?
2. terminates where?
2. terminates between S1 and S4.
3. tough fibroelastic membrane that provides structural support and a fairly impenetrable barrier that normally prevents displacement of an epidural catheter into the fluid-filled subarachnoid space
3. Relationship to each other
2. serves as the major pharmacologic barrier preventing movement of drug fromt he epidural to the subarachnoid space
**conceptually, the dura provides support and the arachnoid membrane imparts impermeability
3. b/c te dura and arachnoid are closely adherent, a spinal needle that penetrates the dura will generally pass through the arachnoid membrane
2. what is the denticulate ligament?
2. along the lateral surface between the dorsal and ventral roots, an extension of the pia membrane forms the denticulate ligament
-a dense serrated longitudinal projection that provides lateral suspension through its attachement tot he dura
3. what happens to the pia as the spinal cord tapers to form the conus medullaris
-distally, the filum terminale becomes enveloped by the dura at the caudal termination of the dural sac (generally around S2) and continuous inferiorly to attach to the posterior wall of the coccyx
1. where do spinal nerves originate?
1. originate where?
2. Leave spinal cord where?
3. How do they leave the spinal nerve?
4. How do they rejoin the spinal nerve?
2. leave with ventral nerve roots passin tinto the spinal nerve trunks
3. they then leave the nerve via the white rami communicates and project to the paravertebral sympathetic ganglia or more distant sites (adrenal medulloa, mesenteric and celiac plexus)
4. after a cholinergic synapse (nicotinic) in the autonomic ganglia, the postsynaptic sympathetic nerve fibers join the spinal nerves via the gray rami communicantes and innervate diverse adrenergic effector sites
1. the first cervical nerve passes where?
2. where do the 7th cervical nerve pass
3. 8th cervical nerve
2. passes above the seventh cervical vertebrae
3. the eighth cervical nervepasses between the seventh cervical vertebra and the first thoracic vertebra.
**Below this point, each spinal nerve passes through the inferior notch of the corresponding vertebra
3. what produces CSF?
4. is the spinal and carnial arachnoid spaces continuous?
3. choroid plexus of the lateral, third, and fourth ventricles
4. yes, carnail nerve can be blocked by local anesthetic migrating into the CSF above the foramen magnum
3. bound cranially by what? Caudally? Anteriorly? Posteriorly? Lateral?
2. irregular column of fat, lymphatics, and blood vessels
Cranially – foramen magnum
Caudally – sacrococcygeal ligament
Anteriorly – posterior longitudinal ligamne
Posteriorly – both the ligamentum flavum and the vertebral lamina
Laterally – vertebral pedicles
4. Is the epidural space a closed space?
5. where is the depth of the epidural space the largest (size of epidural space)? Smallest
largest – about 6 mm – midline at L2. is about 4-5 mm in the midthoracic region
Smallest – where the lumbar and cervical enlargements of the spinal cord (T9-T12 and C3-T2, respectively) encroach n the epidural space with roughly 3 mm left between eh ligamentum flavum and the dura
**There is controversy regarding whether the epidural space has compartments or is continuous
1. arterial supply of spinal cord
2. where do the posterior spinal arteries arise from? are areas supplies by posterior arteries relatively protected from ischemic damage?
-b/c they are paired and have rich collateral anastomotic links from the subclavian and intercostal arteries, this area of the spinal cord is relatively protected from ischemic damage.
3. anterior spinal arteries – origination? at risk for ischemic changes?
-receives branches from the intercostal and iliac arteries, but these branches are variabl in number and location
-More susceptible to ischemia
4. what is the Artery of Adamkiewicz?
aka. the radicularis magna
-arises from the aorta in the lower thoracic or upper lumbar region
-most commonly – is on the left and enters the vertebral canal through the L1 intervertebral foramen.
5. what is the function of the artery of Adamkiewicz?
-damage to this artery during surgy on the aorta (anortic aneurysm resection) or by a strapy epidural needle will produce characteristic bilateral lower extremity motor loss (anterior spinal artery syndrome)
1. what drains the contents of the vertebral canal? where are these veins located?
-prominent in the lateral epidural space and ultimately empty into the azgos venous system
2. what is the azygos venous system?
3. what is the effect of a tumor or increased intra-abdominal pressure that compress the vena cava and epidural placement
-in addition, b/c the vertebral veins are enlarged, the effective volume of the epidural space is reduced, thereby resulting in greater longitudinal spread of injected local anesthetic solutions
1. serious, but rare, complication
2. more common, but less severe?
2. postdural puncture headache. possibility of failed block.
2. infection at the site of planned needle puncture (bacteremia is not an contraindication)
3. elevated ICP
4. bleeding diathesis
-benefit of epidural outweighs the small risk of infection from bactermia
-make sure appropriate antibiotic therapy has been initiated before the block – may decrease the risk of infection
-make sure there is an benefit before performing in pt with multiple sclerosis. Local anesthetic toxicity can be confused for multiple sclerosis exascerbation
“Full, Fast, Forward”
– Standard monitors
-for example, the likelihood of a “failed spinal” increases as interspaces that are more caudal are used, with up to a 7% incidence occurring when the L4-L5 interspace is selected.
-the spinal cord in adults usually lies between the L1 and L2 vertebrae.
-spinal anesthesia is not ordinarily performed above the L2-L3 interspace.
2. what gauges are often used?
closed tapered-tip pencil-point needle with a side port
2. 22-25 gauge
-24 or 25-gauge pencil point needle is often selected.
Pencil-point needle requires more force to insert
-but provides better tactile feel of the various tissues encountered as the needle is advanced
-less incidence of PDPH.
2. layers passed through by the needle
3. how are dura fibers oriented
2. skin, SubQ, supraspinous ligament, interspinous ligament, ligamentum flavum, and the epidural space –> pierce the dura/arachnoid
3. largely oriented along the longitudinal aixs of the dural sac
2. most common error?
3. what is the first resistance encountered in this technique
2. underestimate the distance to the subarachnoid space and direct the needle too medially, with resultant passage across the midline
3. needle bypasses the supraspinous and interspinous ligaments, and the ligamentum flavum will be the first resistance
1. described by who? Why?
– Though generally the widest interspace, it is often inaccessible from the midline b/c of the acute downward orientation of the L5 spinous process
-technically challenging but very useful b/c it is minimally dependent on pt flexion for successful passage of the needle into the subarachnoid space.
-conversely, of blood-tinged CSF continues to flow, the needle should be removed and reinserted.
-the position of cutting edge needle makes no difference.
2. contour of the spinal canal
3. position of the pt in the first few minutes after injection of LA solution into the subarachnoid space.
2. presence or absence of a vasoconstrictor (epinephrine or phenylephrine)
2. 5% lidocaine with 7.5% glucose
–formulated as a 1% plaine solution, most often used as a 0.5% solution with 5% glucose.
-achieved by dilution of anesthetic with an equal volume of 10% glucose.
-for example, in the supine horizontal position, the pt’s thoracic and sacral kyphosis will be dependent relative the the peak created by the lumbar lordosis.
-anesthetic delivered cephalad to this peak will thus move towards the thoracic kyphosis,w hich is normally around T6-T8
Placing the pt in a head-down (Trendelenburg) position will further accentuate this cephalad spread of LA solution and help ensure an adequate level of spinal anesthesia for abdominal surgery.
the effect of lidocaine is more modest
bupivacaine actually decreases both spinal cord and dural blood flow
what is the common dose
2. potential side effects
3. differences in relative intensity of sensory and motor block
1. duration of action
2. More motor or sensory
3. positive characteristics?
2. excellent sensory anesthesia and fairly profound motor block
3. above features, also positive recovery profile
4. what are the 2 major side effects of spinal lidocaine?
2. transient neurologic symptoms
-at first thought to happen with only continuous spinal anesthesia and resulting high amounts of lidocaine. Has since been determined to occur after single shot
***Current suggestion –> reduction in lidocaine dose from 100 mg to 60-75 mg and dilution of the commercial formulation of 5% lidocaine with an equal volume of saline or CSF before subarachnoid injection
6. what is Transient neurologic symptoms? what increases your risk for this?
– lithotomy, knee arthroscopy and outpatient status
**the etiology of transient neurologic symptoms is not established, but their occurrence has reinforced dissatisfaction with lidocaine and general interest in alternative local anesthetics for short-duration spinal anesthesia
2. Procaine – has very short duration of action, the incidence of nausea is relatively frequent, and yet the incidence of TNS is probably only marginally better
3. Chloroprocaine – next slides
1. can epinephrine be added?
2. Can opioids and clonidine be added?
2. yes for fentanyl and clonidine – provide the expected enhancement of chloroprocaine spinal anesthesia
**although ropivacaine has been used as a spinal anesthetic, the advantages over bupivacaine are not obvious
2. what are the concentrations of tetracaine?
2. Tetracaineis prepared as 1% plain solution, which can be diluted with glucose, saline, or water to produce hyperbaric, isobaric, or hypobaric solution, respectively.
Tetracaine – slightly more pronounced motor block
1. time for spinal anesthesia to develop?
2. what fibers are affected first
3. how should anesthetic level be tested?
4. level of SNS anesthesia vs level of sensory block? vs level of motor block.
2. nerve fibers that transmit cold sensation (C and A delta) are among the first to be blocked
3. early indication of level of a spinal anesthetic can be obtained by evaluating the pt’s ability to discriminate temperature changes a s produced by “wetting” the skin with an alcohol sponge. in the area blocked by the spinal anesthetic, the alcohol produces a warm or neutral sensation rather than the cold perceived in the unblocked areas.
4. level of SNS > level sensory > level of motor
2. foot surgery
3. lower extremity surgery
4. Hip surgery, TURP, Vaginal delivery
5. lower abdominal surgery, appendectomy
6. upper abdominal surgery, C-section
2. L2-L3 (knee)
3. L1-L3 (inguinal ligament)
4. T10 (umbilicus)
5. T6-T7 ( xiphoid process)
6. T4 (nipple)
1. Fifth digit
2. Inner aspect of the arm and forearm
3. apex of the axilla
5. Tip of the xyphoid
7. inguinal ligament
8. Outer aspect of the foot
2. T1-T2: some degree of cardioaccelerator block
3. T3: easily determined landmark
4. T4-T5: Possibility of cardioaccelerator block
5. T7: Splanchnic fibers (T5-L1) may be blocked
6. T10: SNS block limited to legs
7. T12: no SNS block
8: S1: Confirms block of the most difficult root to anesthetize
Second – larger myelinated (sensory and motor) fibers
this estimate may be conservative, with SNS block somties exceeding somatic sensory block by as many as sic dermatomes, which explains why systemic hypotension may accompany even low sensory levels of spinal anesthesia
alveolar oxygenation is the same
2. TNS – unclear etiology – don’t inject LA when paresthesia are present to avoid nerve injury
Modest hypotension (e.g., <20 mm Hg) is probably due to decreases in systemic vascular resistance More intense hypotension (>20 mm Hg) probably is the result of decreases in venous return and cardiac output.
the degree of hypotension often parallels the sensory level of spinal anesthesia nd the intravascular fluid volume status of the patient.
–internal autotransfusion – tilt table down 5-10 degrees
3. Epinephrine – when first two fail, to avid cardiac arrest from severe hypotension
**Phenylephrine – increases SVR but may decrease CO and does not correct the decreased venous return contributing to the spinal anesthesia
In the past, phenylephrine was contraindicated in parturients b/c of possible detrimental effects on uterine blood flow, which has not been confirmed.
2. decreased venous return (Bezold-Jarisch reflex)
1. ephedrine, 5 to 50 mg IV
2. atropine, 0.4-1.0 mg IV
3. epinephrine 0.05 to 0.25 mg IV
development of profound bradycardia or asystole –> 1.0 mg IV of epinephrine
-loss of CSF causes downward displacement of the brain and resultant stretch on sensitive supporting structures
-Pain results form distension of the blood vessels, which must compensate for the for the loss of CSF b/c of the fixed volume of the skull
this feature is so distinctive that it is difficult to consider the diagnosis in its absence.
-after puberty (age is important risk factor)
-Females, even it not pregnant
-hx of PDPH
-bed rest, IV fluids, analgesics, and possibly caffeine (500 mg IV
-blood patch – 15-20 mL
Long-term – sealing or “patching” of dural tear.
2. support circulation with sympathomimetics and IV fluid administration
3. Pts placed in head-down position to facilitate venous return
**an attempt to limit the cephalad spread of LA solution in CSF by placing pt’s in a head-up position is not recommended b/c this position with encourage venous pooling, was well as potentially jeopardizing cerebral blood flow, which may contribuate to medullary ischemia
4. Tracheal intbuation
-Treat with sympathomimetic drugs
-large amounts of fluid –> bladder distension if no foley
-IVF needed to maintain preload, prevent hypotension and asystole
-inclusion of epinephrine in spinal will increase the time of urinary retention