SPINAL AND SPINAL AND EPIDURAL EPIDURAL ANESTHESIA ANESTHESIA DEPARTMENT OF ANESTHESIA OSPITAL NG MAYNILA MEDICAL CENTER
SPINAL AND SPINAL AND EPIDURAL EPIDURAL
ANESTHESIAANESTHESIA
DEPARTMENT OF ANESTHESIA
OSPITAL NG MAYNILA MEDICAL CENTER
GOOD GOOD MORNING!!MORNING!!
!!
EPIDURAL AND SPINAL EPIDURAL AND SPINAL ANESTHESIAANESTHESIA
• No absolute indications
• Clinical situations, patient physiology, surgical procedure: makes central neuraxial block the technique of choice
EPIDURAL AND SPINAL EPIDURAL AND SPINAL ANESTHESIAANESTHESIA
• Blunt the “stress response” to surgery – decrease intraoperative blood loss – lower the incidence of postoperative
thromboembolic events – decrease morbidity and mortality in
high-risk surgical patients
• extend analgesia into the postoperative period (provide better analgesia than can be achieved with parenteral opioids)
• provide analgesia to non-surgical patients
ANATOMYANATOMY
VERTEBRAEVERTEBRAE
The spine consists of 33 vertebrae
• 7 cervical • 12 thoracic• 5 lumbar • 5 fused sacral • 4 fused coccygeal
• Cervical (except C1), thoracic, and lumbar vertebrae: body anteriorly, two pedicles that project posteriorly from the body, and two laminae that connect the pedicles ----form the vertebral canal, which contains the spinal cord, spinal nerves, and epidural space
• Lamina: give rise to the transverse processes (laterally); spinous process (posteriorly) --- sites for muscle and ligament attachments
• Pedicles: contain a superior and inferior vertebral notch through which the spinal nerves exit the vertebral canal
5 sacral vertebrae fused to form the wedge-shaped sacrum (connects the spine with the iliac wings of the pelvis)
• 5th sacral vertebra (not fused posteriorly) give rise to a variably shaped opening ---- sacral hiatus opening into the sacral canal (caudal termination of the epidural space)
Sacral cornu• bony prominences on either side of the hiatus• aid in identification of sacral hiatus
Coccyx• fused 4 rudimentary coccygeal vertebrae• a narrow triangular bone that abuts the sacral
hiatus
• Tip of the coccyx can often be palpated in the proximal gluteal cleft and by running one’s finger cephalad along its smooth surface, the sacral cornu can be identified at the 1st bony prominence encountered
C7 : 1st prominent spinous process encountered while running the hand down the back of the neck
T1 : most prominent spinous process
T12 : can be identified by palpating the 12th rib and tracing it back to its attachement to T12
Line drawn between the iliac crests: •body of L5 or the 4-5 interspace
LIGAMENTSLIGAMENTS
• Vertebral bodies are stabilized by 5 ligaments that increase in size between the cervical and lumbar vertebrae
EPIDURAL SPACEEPIDURAL SPACE• Space that lies between the spinal
meninges and the sides of the vertebral canal
• Boundaries:– Cranially: foramen magnum– Caudally: sacrococcygeal ligament covering
the sacral hiatus– Anteriorly: posterior longitudinal ligament– Laterally: vertebral pedicles– Posteriorly: ligamentum flavum and vertebral
lamina
• Not a closed space but communicates with the paravertebral space by way of the intervertebral foramina
• Shallowest anteriorly where the dura may in some places fuse with the posterior longitudinal ligament
• Deepest posteriorly
• Composed of a series of discontinuous compartments that become continuous when the potential space separating the compartments is opened up by injection of air or liquid
MENINGESMENINGES
• Spinal meninges consist of 3 protective membranes :– Dura mater– Arachnoid mater– Pia mater
Dura mater• Outermost and thickest meningeal
tissue• Begins at the foramen magnum; ends
at approx S2 where it fuses with the filum terminale
• Inner surface abuts the arachnoid mater
Arachnoid mater• Delicate, avascular membrane
composed of overlapping layers of flattened cells with connective tissue fibers running between the cellular layers
• Specialized connections (tight junctions and occluding junctions) account for the fact that it is the physiologic barrier for drugs moving between the epidural space and the spinal cord
• Subarachnoid space lies between the arachnoid mater and the pia mater and contains the CSF
• Spinal CSF is in continuity with the cranial CSF and provides an avenue for drugs in the spinal CSF to reach the brain
• Spinal nerve roots and rootlets run in the subarachnoid space
Pia mater• Adherent to the spinal cord and is
composed of a thin layer of connective tissue cells interspersed with collagen
• Extends to the tip of the spinal cord where it becomes the filum terminale, which anchors the spinal cord to the sacrum
• Gives rise to the dentate ligaments
TECHNIQUETECHNIQUE
NEEDLESNEEDLES
NEEDLESNEEDLESSpinal NeedlesWhitacre and Sprotte: • “pencil-point” tip• needle hole on the
side of the shaft
Greene and Quincke: beveled tips with cutting edges
Spinal Needles• * pencil-point needles
require more force to insert than the bevel-tip needles but provide better tactile “feel”; not deflected* Size: 22-29 gauge larger
gauge smaller diameter
Epidural Needles• Touhy: curved tip to
help control the direction that the catheter moves in the epidural space
• Hustead: less curved tip
• Crawford: straight; less suitable for catheter insertion
*sizes: 16-19 gauge
SEDATIONSEDATION• Light sedation before placement of block
– Successful spinal and epidural anesthesia requires patient participation to:•maintain good position•evaluate block height•indicate paresthesias if needle contacts
neural elements•properly evaluate an epidural test
• Once the block is placed and adequate block height assured, patient can be sedated as deemed appropriate
SPINAL ANESTHESIASPINAL ANESTHESIAPOSITIONPatient positioning is critical to
successful spinal puncture• lateral decubitus • sitting position • prone jackknife position
POSITIONLateral decubitus• patient lies with the operative side
down (hyperbaric LA) • or with operative side up (hypobaric
LA) ---most dense block occurs on the operative side
POSITION
– back at the edge of the table– patient’s shoulders and hips positioned
perpendicular to the bed– knees drawn to the chest; neck flexed;
patient instructed to curve the back outward
MIDLINE APPROACH• Skin overlying the desired interspace is
infiltrated with a small amount of LA (1-2 ml) to a depth of 1-2 inches to prevent pain when inserting the spinal needle
• Slight cephalad angulation (10-15 degrees)
MIDLINE APPROACHNeedle is then advanced • subcutaneous tissue • supraspinous ligament • interspinous ligament• ligamentum flavum• epidural space • dura mater• arachnoid mater
MIDLINE APPROACH
MIDLINE APPROACHPenetration of the dura mater produces a
subtle “pop”– detection of dural penetration
• prevent inserting the needle all the way through the subarachnoid space and contacting the vertebral body;
– insert spinal needle quickly without having to stop every few mm and remove the stylet to look for CSF at the needle
MIDLINE APPROACHOnce the needle tip is believed to be in the
subarachnoid space, stylet is removed to see if CSF appears at the needle hub– Small diameter needles (26-29 gauge)
requires 5-10 sec or >/= 1 minute
• Failure to obtain CSF suggests that the needle orifice is not in the subarachnoid space and must be reinserted
MIDLINE APPROACHOnce the needle is correctly inserted into
the subarachnoid space, it is fixed in position and the syringe containing LA is attached
CSF is gently aspirated to confirm that the needle tip remained in the subarachnoid space and LA slowly injected (</=0.5 ml/s-1)
MIDLINE APPROACHAfter completing the injection, a small
volume of CSF is again aspirated to confirm that the needle tip remained in the subarachnoid space while the LA was deposited
This CSF is then reinjected and the needle, syringe, and any introducer removed together as a unit
MIDLINE APPROACHstrict attention to patient’s hemodynamic
status with BP and/or HR supportedblock height should also be assessed early
– pin prick – temperature sensation
–Table may be tilted as appropriate to influence further spread of local anesthetics
PARAMEDIAN APPROACH• useful in situations where the patient’s
anatomy does not favor the midline approach – inability to flex the spine– heavily calcified interspinous ligaments
• Patient in any position; best approach for the patient in the prone jackknife position
PARAMEDIAN APPROACH• Identify the spinous process forming
the lower border of the desired interspace
• Needle inserted – ~1 cm lateral – directed toward middle of the interspace
~45 degrees cephalad – medial angulation (~15 degrees) to
compensate for the lateral insertion point
PARAMEDIAN APPROACH
•Needle inserted ~1 cm lateral, directed toward middle of the interspace ~45 degrees cephalad with just enough medial angulation (~15 degrees) to compensate for the lateral insertion point
PARAMEDIAN APPROACH1st significant resistance encountered:
ligamentum flavumAlternative method:
– insert needle perpendicular to the skin in all planes until the lamina is contacted; needle is then walked off the superior edge of the lamina and into the subarachnoid space
**Lamina provides a valuable landmark that facilitates correct needle placement
EPIDURAL ANESTHESIAEPIDURAL ANESTHESIA• May be performed at
any intervertebral space
• LA skin wheal is raised to the point of needle insertion
• Pierce the skin with a >/=18 G hypodermic needle
• Epidural needle inserted through the subcutaneous tissue and into the interspinous ligament “gritty feel”
• Needle is advanced slowly until an increase in resistance is felt : ligamentum flavum
Techniques to identify epidural space:– Loss of resistance
technique (fluid/air)• Glass syringe: 2-3 ml
saline + 0.1-0.3 ml air bubble
– Hanging drop technique
After entering the epidural space, stop advancing the needle– heightens the risk of meningeal puncture
“wet tap”
• LA test dose should be administered to help rule out undectected subarachoid or IV needle placement
• After a negative test dose, desired volume should be administered in small increments
EPIDURAL TEST DOSE– To identify epidural needles or catheters
that have entered an epidural vein or the subarachnoid space
– Failure to perform: IV injection or total spinal block
– 3 ml of LA + 1:200,000 epinephrine• IV: epinephrine
– HR increases 20-40 sec after– BP increase of >/=20 mmHg
• Subarachnoid: motor block ---LA
PHYSIOLOGYPHYSIOLOGY
• Spinal anesthesia interrupts sensory, motor, and sympathetic nervous system
• Classic concept:– Conduction blockade through small diameter
unmyelinated (sympathetic) fibers before interrupting conduction via large myelinated (sensory & motor) fibers
• Block of afferent impulses from the surgical site leads to absence of adrenocortical response to pain
Cardiovascular system• Vasodilatation of resistance and capacitance
vessels occurs: hypovolaemia, tachycardia, drop in blood pressure – exacerbated by blockade of the
sympathetic nerve supply to the adrenal glands, preventing the release of catecholamines.
• Bradycardia: If blockade is as high as T2, sympathetic supply to the heart (T2-T5)
• overall result: inadequate perfusion of vital organsmeasures: restore blood pressure and cardiac output (fluid administration, vasoconstrictors)
• Sympathetic outflow extends from T1 - L2 (blockade of nerve roots below this level, knee surgery, is less likely to cause significant sympathetic blockade, compared with procedures requiring blockade above the umbilicus)
Respiratory system• usually unaffected unless blockade is high
enough to affect intercostal muscle nerve supply (thoracic nerve roots) leading to reliance on diaphragmatic breathing alone
• distress to the patient, as they may feel unable to breathe adequately
• decreased ability to cough and expel secretions
• if patients cannot breathe, ventilate (face mask and bag
Gastrointestinal system• Blockade of sympathetic outflow (T5-L1),
leads to predominance of parasympathetic (vagus and sacral parasympathetic outflow)– leading to active peristalsis and relaxed
sphincters, and a small, contracted gut, which enhances surgical access
– Splenic enlargement (2-3 fold) occurs
• If above T5, inhibits sympathetic innervation to the GIT, resulting in unopposed parasympathetic nervous system activity– Contracted intestines and relaxed sphincter; if not
on NPO, tendency to develop vomiting
Genitourinary tract• urinary retention is a common problem • severe drop in blood pressure may affect
glomerular filtration in the kidney (if sympathetic blockade extends high enough to cause significant vasodilatation)
• ureters are contracted and ureterovesical orifice is relaxed
• Decreased bleeding may be a reflection of decreased BP
• Increased blood flow to lower extremities ---- decreased incidence of thromboembolism
• BLOCK HEIGHTSURGICAL
PROCEDURESUGGESTED
BLOCK HEIGHTTECHNIQUE
PerianalPerirectal
L1-2 Hyperbaric/sitting posHypobaric/jackknife pos
Lower extremity/ HipTURPVaginal/ cervical
T10 Isobaric
HerniorrhaphyPelvic proceduresAppendectomy
T6-8 Hyperbaric/ horizontal
AbdominalCesarean section
T4-6 Hyperbaric/ horizontal
FACTORS THAT AFFECT SPREAD OF LOCAL FACTORS THAT AFFECT SPREAD OF LOCAL ANESTHETIC SOLUTIONSANESTHETIC SOLUTIONS
Characteristics of the local anesthetic solution– Baricity: ratio of density (mass/vol) of LA div
density of CSF– Local anesthetic dose– Local anesthetic concentration– Volume injected
Patient characteristicsAge WeightHeightGenderPregnancyPatient position
FACTORS THAT AFFECT SPREAD OF LOCAL FACTORS THAT AFFECT SPREAD OF LOCAL ANESTHETIC SOLUTIONSANESTHETIC SOLUTIONS
Technique– Site of injection
Diffusion
Speed of injectionBarbotageDirection of needle bevelAddition of vasoconstrictors
LOCAL ANESTHETIC LOCAL ANESTHETIC SOLUTIONSOLUTION
• HYPERBARIC: solution more dense than CSF; >/=1.0015– Add glucose (5-8% dextrose) of increase the
density– LA solution settles to dependent region
• HYPOBARIC: solution less dense than CSF; <0.9990– Add sterile/distilled water; floats up to the nerves
innervating surgical site
• ISOBARIC: same density; 1.0000– Dilute with CSF or normosaline solution
COMPLICATIONSCOMPLICATIONS
• Hypotension• Postdural puncture headache• Hearing loss• Total spinal• Backache• nausea• Urinary retention• Systemic toxicity• Neurologic injury• Spinal hematoma
• Hypotension– Due to sympathetic nervous system
blockadea.Decreased venous return to heart,
decreased cardiac outputb.Decreased systemic vascular resistancec.Bradycardia due to blockade of
cardioaccelerator fibers (T1-3), decreased cardiac output
• HypotensionTreatment: restore venous return to incrase
cardiac output– Position head-down: autotransfusion– Hydration before spinal anesthesia– Sympathomimetics
• Postdural puncture headache– Frontal/occipital– Worsened by sitting, improved by supine position– Due to decreased CSF pressure and resulting
tension on meningeal vessels and nerves as a result of leakage of CSF through the dural hole
– Diplopia due to traction on abducens nerve– Treatment: bed rest, analgesics
• Hydration (>/= 3L/day) to increase CSF production• Epidural patch (10-20 ml) to seal dura• Caffeine-sodium benzoate (by vasoconstriction)
• Hearing loss
• High Spinal– Undesired excessive level of sensory and
motor anesthesia associated with difficulty of breathing or apnea --- arterial hypoxemia or hypercarbia
– Apnea reflects ischemic paralysis of medullary ventilatory centers due to profound hypotension and associated with decreased cerebral blood flow
• High Spinal– Treatment: support breathing and
circulationa. Positive pressure ventilation with face maskb. IVF and sympathomimeticsc. Head down to increase venous return(head up will jeopardize cerebral blood flow ---
medullary ischemiad. Intubation of trachea in those at risk for
aspiration
•Total spinal – rare complication– profound hypotension– apnea– unconsciousness– dilated pupils as a result of the action of
local anesthetic on the brainstem
• Management– Airway – secure, administer 100% oxygen – Breathing - ventilate by facemask, intubate – Circulation - treat with iv fluids and vasopressor – Continue to ventilate until the block wears off (2 -
4 hours) – As the block recedes the patient will begin
recovering consciousness followed by breathing and then movement of the arms and finally legs. Consider some sedation (diazepam 5 - 10mg i/v) when the patient begins to recover consciousness but is still intubated and requiring ventilation
• Backache– May be related to position required for
surgery– More likely due to ligamentous strain
when in an uncomfortable position
• Nausea– May be due to hypotension --- cerebral
ischemia; tx sympathomimetics– May be due to predominance of
parasympathetic nervous system activity; tx atropine 0.4 mg IV
• Urinary Retention– Because spinal anesthesia interferes with
innervation of the bladder– Administration of large amounts of fluid ---
bladder distention requiring catheter drainage
• Systemic toxicity
• Neurologic injury– Very rare due to small dose of LA
employed– In the absence of hematoma or abscess,
treatment is symptomatic
• Spinal hematoma– Rare; present with numbness or LE
weakness– Risk factor: coagulation defects
• Inadvertent high epidural block – due to an excessively large dose of local
anesthetic– hypotension, nausea, sensory loss or
paresthesia of high thoracic or even cervical nerve roots (arms), or difficulty breathing
– most severe cases may require induction of GA with securing of the airway, while treating hypotension
– If patient has a clear airway and is breathing adequately: reassurance and any hypotension immediately treated
– Difficulty in talking (small tidal volumes due to phrenic block) and drowsiness are signs that the block is becoming excessively high and should be managed as an emergency
• Local anesthetic toxicity – excessive dose of local anaesthetic– moderate dose of LA, injected directly into
a blood vessel– epidural catheter is inadvertently
advanced into one of the many epidural veins. It is therefore vital to aspirate from the epidural catheter prior to injecting local anaesthetic
– symptoms: light-headedness, tinnitus, circumoral tingling or numbness and a feeling of anxiety or "impending doom", followed by confusion, tremor, convulsions, coma and CPR arrest
– early recognition: discontinue further administration of local anesthetic drugs
– treatment: supportive, sedative/anticonvulsants, cardiopulmonary resuscitation if required
CONTRAINDICATIONSCONTRAINDICATIONS
• Patient refusal: only absolute contraindication
• Conditions that increase the apparent risk of central neuraxial block- Hypovolemia or shock increase the risk of
hypotension- Increased ICP increases the risk of brain
herniation when CSF is lost through the needle, or if a further increase in ICP follows injection of large volumes of solution into the epidural or subarachnoid spaces
- Coagulopathy or thrombocytopenia increase the risk of epidural hematoma
- Sepsis increases the risk of meningitis- Infection at the puncture site increases the risk of
meningitis
• Pre-existing neurologic disease (multiple sclerosis) : considered CI– No evidence to suggest that spinal or
epidural anesthesia alters the course of any preexisting neurologic disease
– Recommendations to avoid RA stem largely from a medicolegal concern that the anesthetic may be incorrectly blamed for any subsequent worsening of the patient’s preexisting condition
SPINAL OR EPIDURAL SPINAL OR EPIDURAL ANESTHESIA?ANESTHESIA?
• Spinal Anesthesia– Less time to
perform– Produces more
rapid onset of better quality sensorimotor block
– Less pain during surgery
SPINAL OR EPIDURAL SPINAL OR EPIDURAL ANESTHESIA?ANESTHESIA?
• Epidural Anesthesia– Lower risk of PDPH– Less hypotension if epinephrine is not
added to the LA– Ability to prolong or extend the block via
an indwelling catheter– Option of using an epidural catheter to
provide postoperative analgesia