Objectives Flashcards
What is the part of the pia mater that secures the cord to the upper portion of the coccyx.
Filum terminale
Name characteristics and anatomical structures of the ligamentum flavum
It connects the lamina of adjacent vertebrae. Also known as the “yellow ligament”. It is tough and elastic. Small vessels from the vertebral plexuses penetrate it and may cause a bit of blood to enter the syringe.
What is the part of the spinal cord that is made up of the lumbar and sacral roots that extends past L1-L2
Cauda Equina
What is the space between dura and ligaments of the vertebrae that contains adipose tissue and blood vessels, and Extends from skull to the sacral hiatus?
epidural space
Where is the epidural space widest and narrowest?
Widest at L2 (5-6 mm) Narrowest at C5 (1 -1.5 mm)
What structures can be found in the epidural space?
Lymphatic vessels, Small arteries and veins (together these form a plexus), and Fatty tissues
What are the Strong ligaments that interconnect the tips of the spines from the axis down to the sacrum.
Supraspinous ligaments
What are the thin membranes that fill the intervals from spine to spine and from the deep ligamentum flavum to the supraspinal ligaments superficially?
Interspinous Ligaments.
Name the structures a spinal needle passes through external to internal Skin
Skin —►subQ —► supraspinous lig. —► interspinous ligament —► ligamentum flavum—► Epidural space—►Dura mater—►Arachnoid mater—►access to CSF
At what levels in adults and infants are SAB’s not performed above?
SABs are not performed above L2 in an adult. SAB’s are not performed above L4 in infants
What is the specific site of deposition of local anesthetic for a SAB?
The suparachnoid space (between the arachnoid mater and pia mater
Where does the spinal cord ends for both children and adults?
The spinal cord ends at L3 in infants. After age 1, the cord ends at L1 or L2.
How many spinal nerves are there?
31
At each vertebral segment the dorsal root and the ventral root form what structure?
Spinal nerve
What is the space formed when the 5th sacral laminae do not fuse at the midline creating a “V” shape? 5% of adults do not have this space?
Sacral hiatus
What spinal nerve levels correlate with the perineum?
S2-S5
What is the large round mass of a vertebra; it forms the anterior aspect of the vertebra.
Vertebral bodies
What is the bridge of bone extending from the posterior aspect of the body.
pedicle
What are the flat plates of bone extending from the pedicles that fuse with each other in the median plane.
laminae
What are the two processes that project laterally from the junction of a lamina and a pedicle.
Transverse processes
What is the single process that projects posteriorly from each vertebral arch at the junction of the two laminae.
Spinous Process
What are the two processes that project inferiorly posterior to the transverse process, which articulate with the superior articular process of the infrajacent vertebra.
Inferior articular processes
What are the two processes that project posterior to the transverse processes, which articulate with the inferior articular process of the suprajacent vertebra.
Superior articular processes
What is the space between the adjacent spinous processes of the vertebrae that are triangular in shape and nerve roots exit?
Interlaminar Foramen
What helps open the interlaminar foramen?
When the patient is flexed.
Where does the spinal cord begin and end?
begins at foramen magnum and ends as conus medullar is (L3 at birth, L1 adult)
What roots are the afferent and efferent nerves found in?
Afferent in the dorsal Efferent in the ventral
Where is the spinal cord thickest at?
Thickest at the cervical and lumbar regions.
What is the Tough, outer membrane that Extends from foramen magnum to S2 and then continues to cover the filum terminale?
Dura Mater
What is the potential space between the dura mater and arachnoid mater
subdural space
What is the thin, avascular, middle covering closely attached to the dura mater on the inner surface?
Arachnoid mater
What is found right beneath the arachnoid mater?
CSF
What is the delicate highly vascular membrane closely attached to cord and brain?
Pia mater
What are the lateral projections of the pia mater that attach to the dura and support the cord?
denticulate ligaments
What arises form the vertebrals and supply the posterior cord and anterior 1/3 of the cord
posterior spinal arteries (2 of them)
What supplies tbe spinal nerve roots and enters every intervertebral foramen.
Radicular arteries
What arises from the the vertebral arteries and supplies the anterior 2/3 of the cord?
Anterior spinal artery (1)
What other arteries join in further down the cord to help supply the anterior spinal artery
Several arteries from the subclavian and aorta, cervical and thoracic radicular arteries, Radicularis Magna and Artery of Adamkiewicz
What is the largest radicular artery that supplies much of the blood flow to the anterior spinal artery?
Artery of Adamkiewicz
What drains blood from the spinal cord?
the anterior and posterior spinal veins
How many nerves are in each region of the vertebrae?
Cervical= 8 Thoracic= 12 Lumbar= 5 Sacral= 5 Coccygeal= 1
What structures are encountered during a paramedian approach in elderly patients with calcified ligaments?
Skin —►subQ —► ligamentum flavum—► Epidural space—►Dura mater—►Arachnoid mater—►access to CSF (does not puncture the supraspinous or interspinous ligaments)
State the characteristics of CSF (spec grav and ph)
Specific gravity is 1.003 to 1.009. pH is 7.32
What is the total CSF volume in adults vs. infants?
Adults= 150 replaced 3x/day producing approx 500ml/day Infants=50ml
Is the sacral hiatus open or closed in children?
Open
Where does the subarachnoid space end in Adults vs. children?
Adults it ends at S2 In Child it ends at S3-S4
What sections of the vertebrae are concave anteriorly and which are convex anteriorly?
Concave anteriorly= Thoracic and sacral Convex anteriorly= Cervical and Lumbar
If a patient is lying supine what are the high and low points of the vertebrae?
High= C3 and L3 (Convex anteriorly) Low= T6 and S2 (Concave anteriorly)
What is the block level need for Perirectal and Perineal (ex. Hemorrhoidectomy, transvaginal slings)
S4-L1,2
What is the block level need forLower extremity surgery with tourniquet use
T10-T8
What is the dermatome level needed for a lower abdominal surgery (TAH, C-section, Inguinal hernia, appendectomy)
T4-T6
What is the dermatome level needed for TURP, Vaginal Delivery, Total Hip replacement, fem-Pop bypass
T6-T8
What is the dermatome level needed for Upper Abdominal (open cholecystectomy, abdominal exploration)
T1 (rare)
What is baricity?
The measure of baricity is specific gravity and defined in relationship to the density of CSF
Explain hyperbaric, isobaric, and hypobaric solutions in relation to CSF
- Hypobaric soln is less dense than CSF. (will rise <0.9990 water is added)
- Isobaric soln is the same density of CSF (spec grav of CSF is 1.003-1.009)
- Hyperbaric is more dense than CSF (will sink, soln >1.0015 will be hyperbaric, dextrose is added)
What causes post dural puncture headaches?
- decrease in CSF pressure from leakage of CSF thru the dura puncture—►brain lies lower (“sags”) in the cranium—►traction on intracranial vessels and nerves 2. Use e pencil point, smaller lauge needles (25-27 g). to prevent 3. More common in young women especially if pregnant, greatest in 20-29YO 4.Greater risk if early ambulation occurs 5. Bevel of needle should separate fibers not cut, keep needle paral/el to fibers
What are symptoms of a post dural puncture headache?
-Hallmark s/s headache when erect or semi erect, resolves quickly when resumes a supine position. May also have tinnitus, photophobia, N/V -Dull, aching, throbbing, and may be mild to severe
When is the onset of a PDPH
Onset within 12-48 hours, rarely more than 5 days after dural puncture
What things can be done to treat PDPH
- intravenous or oral caffeine - 500mg IV or 300mg Orally. 2. theophyline 300mg PO 3. imitrex 6mg SQ 4.Epidural saline infusion- 15-20ml/hr for 24hr (high relapse though) 5. Epidural blood patch (most effective)
What is a epidural blood patch?
10-20ml (15 ml) of autologous blood aseptically injected into the next lower interspace. Avoid lifting, straining, and air travel for 24-48 hours after to allow to to secure. >90% effective
What will Epi do when added to LA and what is the dose?
0.2 mg added to prolong the duration of action, believed due to vasoconstriction->slower vascular absorption
What LA’s will be prolonged by Epi being added and which one won’t?
-Prolongs Lido and Tetracaine . -Believed not to prolong bupivicaine (already a vasoconstrictor) but this is controversial.
What happens when clonidine is added to an LA?
A alpha 2 agonist enhances pain relief and prolongs the sensory block and motor block
What do narcotics/opioids do when added to a LA?
They increase the “density” of the block. Opioids act synergistically by binding to the gray matter of the substanstia gelatinosa in the dorsal horn of the spinal cord.
What is the dose, onset, and duration of fentanyl when added to a LA
-Typical/ dose: 20 mcg Prolongs the duration of anesthesia without prolonging sensorimotor function or bladder function -Rapid onset (5-10 min) -Intermediate duration (1-2hr)
What is the dose, onset, and duration of preservative free Morphine when added to a LA
-Typical dose: 100-200 mcg = 0.1-0.2mg (typically packaged as 1 mg per 1ml -Slower onset of action (30-60 min) -Longer DOA, so good for post op pain control (up to 24 hours) - Higher risk for respiratory depression especially in higher doses. (300-500mcg)
What is the DOA for Chloroprocaine, Bupivicaine, and Tetracaine?
Chloroprocaine= 45-60 min (< 1hr) Bupivicaine= 90-150 min (1.5-2.5 hr) Tetracaine= 120-180 min (2-3 hrs)
What doses of Chloroprocaine 3% would you use for a T10 block and a T4 block?
T10= 30-40mg T4= 45mg
What doses of Bupivicaine 0.75% would you use for a L4, T10, and T4 block?
L4= 7.5mg T10= 10-12mg T4= 12-15mg
What doses of Tetracaine 1% would you use for a L4, T10, and T4 block?
L4= 5mg T10= 6-10mg T4= 12-15mg
What are absolute contraindications to a SAB.
1.Patient refusal 2.Sepsis at the site of injection 3.Hypovolemia 4.Coagulopathy 5.Indeterminate neurologic disease 6.Increase intracranial pressure
What are relative contraindications to SAB
- infection distinct from the site of injection 2. Unknown duration of surgery 3. Inability to communicate with the pt 4. Prior back surgery
What should the CRNA do if paresthesia is experienced?
When a paresthesia occurs while performing a spinal puncture, the advancement of the needle and the local anesthetic injection should be stopped, and disappearance of paresthesia should be awaited.
What is paresthesia?
Paresthesia is thought to result from mechanical stimulation of the nerve, resulting in a sensor feeling described as “an electric current” or “shock” in the sensory distribution of the nerve that is being touched such, paresthesia can indicate that the needle is in close proximity to the nerve and may be a warning sign of impending mechanical injury, should the needle be further advanced.
State what Whitacre and Quinke needs do to the spinal fibers. How are the needle tips shaped?
1.Whitacre- pencil-point needles = rounded, noncutting bevel with a solid tip thought to “spread” the longitudinal fibers of the dura 2. Quinke- cutting bevels = sharp point cutting edges.
What does blood tinged CSF indicate and what is done if it is encountered?
may be in vascular space, reposition needle
Describe the onset of a SAB and location of motor, sensory, and sympathetic blockade.
Onset = Sympathetic—►Sensory—►Motor (BCA gdba) Sympathetic blockade= 2 above sensory level Motor blockade= 2 below sensory level
If you had a sensory block at T1 where would your sympathetic and motor blocks be?
Sympathetic= C7 Motor= T3
If you had a motor block at L2 where would your sensory and sympathetic block be?
Sensory =T12 Sympathetic= T10
What factors affect the spread of LA in the subarachnoid space?
Properties of local anesthetic solution: Baricity, Dose, Volume, specific gravity and LA concentration
Patient characteristics: Position during and after injection, Height and Weight, Spinal column anatomy,Decreased CSF volume (increased intraabdominal pressure due to increased weight, pregnancy, etc.)
**Technique: **site of injection, needle bevel direction
What will increasing the dose of a LA do to effects of a spinal?
- increasing dose has more effect on the duration of the block (increased duration) and density of the block
- Increasing dose will increase level of spread but not to the degree of baricity and position
How does a SAB work?
By injecting LA into the CSF, the local contacts the anterior and posterior nerve roots that pass through the CSF. Anesthesia results by the LA interrupting transmission of impulses to the sensory, motor, and autonomic nerve fibers that are in the anterior and poslenor nerve roots
At what level does Loss of perception of intercostal and abdominal wall movement take place?
When sensory block reaches T2-T4 (May cause the pt to feel dyspneic.)
If the block is at C2-C4 what complication will happen?
Phrenic nerve paralysis and loss of accessory muscles of ventilation increases the potential for hypoxia.
How long should NSAIDs and aspirin be held before Regional anesthesia
No need to hold. do not increase hematoma risk, assuming the pt does not have any coagulopathy
How long should NSAIDs and aspirin be held before Regional anesthesia
No need to hold. do not increase hematoma risk, assuming the pt does not have any coagulopathy
How long should Herbals such as ginko, garlic, ginseng, and fish oil be held before Regional anesthesia
recommended to d/c for 1 week, but no research on this
How long should low dose heparin (Lovenox) be held before and after Regional anesthesia
hold for 12 hours prior to a block. (Wait 12 hrs) before inserting a SAB). Do not remove a epidural catheter for 12 hours after dose of lovenox. Do not restart lovenox for 12 hours after removing
How long should low dose heparin (unfractionated/Sub-Q) be held before and after Regional anesthesia
Wait to do a block for 2 hours after the patient was dosed. Get a PTT to confirm. Do not restart heparin for 2 hours after SAB. If a epidural catheter needs to be removed, wait 2 hours after last dose
What are the recomendations for coumadin levels prior SAB insertion?
INR < 1.3 = safe
INR > 1.5 = NO!
INR 1.3 -1.5 = must weigh the risk vs. benefits
What are the recomendations for platlet levels prior SAB insertion?
Platelets > 100,000 = OK
Platelets < 50,000 = NO!
Platelets 50,000 -100,000 = weigh risks vs. benefits, but NOT recommended
How long should Plavix and Ticlid be held before and after Regional anesthesia
Plavix- d/c for 7 days
Ticlid- d/c for 14 days
Why might bradycardia occur from a SAB and what would you do to treat it?
- When the SAB approaches T5 cardiac accelerator fibers (T1-T4) are sympatheticly blocked.
- Treatment= Atropine is indicated. If not treated promptly, asystole and CV collapse can occur. CV collapse is preceded by bradycardia and hypotension, (ephedrine can also be used)
How would you treat hypotension from a sympathetic block?
The best method of treating hypotension is physiologic, not pharmacologic. give IV fluids if not normovolemic; if normovolemic then give ephedrine. If HR is normal or high phenylephrine
What is a total spinal and what are the symptoms and treatment?
- When the block rises above the cervical region, blocking the entire cord and occasionally the brainstem. Profound bradycardia, hypotension, and potential respiratory arrest due to respiratory mushle paralysis and block of brainstem respiratory control centers.
- Progresses rapidly: ascending motor-sensory block-> Decreased HR ,BP, leads to dyspnea with difficulty swallowing and phonating—►respiratory arrest and loss of consciousness
- Treatment= supportive: ABC’s… Treat HR, BP, ventilate, and oxygenate - GA and intubate if cannot mask ventilate
What causes N&V from SAB and what can be done to treat it?
- Due to sympathetic blockade and unopposed parasympathetic activity after spinal blockade, secretions increase, spnincters relax, and The bowel becomes constricted. increased vagal activity after sympathetic block causes increased peristalsis of the gastrointestinal tract, which leads to nausea.
- Treatment= Treat bp (Fluids and vasopressors) and give oxygen
