Spinal Anesthesia (pt 2) Flashcards
Detail some things to look for on Pre-op Assessment for Spinal Anesthesia
-Respiratory issues?
-Ability to lie flat
-Cardiac issues (Fixed cardiomyopathy, Aortic stenosis - anyone who can’t recover if their BP drops)
-Active infection
-Prior back surgery
-Neurological issues
-Coagulopathy
-Expected length of case
-Patient consent, understanding, and cooperation
Which type of needle ends in a pencil point and separates the dura instead of cutting it? (3 names)
Whitacre Needles (also Sprotte or Greene non-cutting needles)
What is the purpose of using a non-cutting needle?
-Less trauma to the dura and less CSF leakage
-Less post-dural puncture headaches
-Pencil point pushes through the fibers and allows them to come back together.
What is the line drawn at the most superior point of the iliac crests?
Tuffier’s Line
What vertebrae is approx. at Tuffier’s Line?
L4
Describe sitting positioning for SAB
-Back should be maximally flexed to maximize opening between interspaces
-“Mad Cat” or “Boiled Shrimp”
Describe lateral position for SAB
-“Fetal Position”
-“Cannonball into pool position”
Describe prone positioning for SAB
-Jack knife
-Hypobaric or isobaric LA used ( will flow to the non-dependent region - away from the head). Ex: Tetracaine with water
-Must aspirate CSF - it will not drip out
-Utilized for rectal procedures
-Can also use Caudal anesthesia in prone position
Describe the preparation prior to performing a NA block.
-Patient consented
-Standard monitoring and baseline VS +/- O2
-Drugs and airway equipment
-Emergency drugs for hypotension (have Neo and Ephedrine drawn up prior to starting)
-+/- Bolus of NS/LR (10-15 mL/kg, reduce dose for elderly)
-Sedation needed?
-Patient & nurse cooperation?
-Position patient appropriately
List the steps to performing a NA Block.
-Know block tray - open it
-Gown/gloves/mask
-Prepare meds and equipment
-Apply sterile drape and prep skin
-Mark interspace
-Do a skin wheal with LA (Superficially raised)
-Insert Introducer
-Insert spinal needle through introducer
-Continue until you feel a POP (Dura Mater)
-Remove stylet and observe flow of CSF
-Grab syringe with local, aspirate CSF (swirl), inject.
-Remove the introducer, needle, and syringe as one unit.
-Position patient how you want and cycle BP (q 2 minutes)
Why are Introducers used in SAB?
-For smaller intrathecal needles
-Provides stability
-Establishes direction
-Can act like a finder needle
What gauge needle does not need an Introducer?
-22g does not need an introducer (good for elderly with thicker ligaments)
-25-27 g is flimsy and needs support
Which way should the bevel of the Introducer be oriented when using a midline vs paramedian approach?
-Bevel to the side (Midline)
-Bevel facing up (Paramedian)
How do you introduce your spinal needle through the introducer?
With the notch facing cephalad at a 10-15 degree angle
What is the order of structures that you pass through when performing a SAB via the Midline approach?
-Skin
-Subcut tissue
-Supraspinous Ligament
-Interspinous Ligament
-Ligamentum Flavum
-Epidural space
-Dura Mater
-Arachnoid Mater
What is the order of structures that you pass through when performing a SAB via the Paramedian approach?
-Skin
-Subcut tissue
-Ligamentum Flavum
-Epidural space
-Dura Mater
-Arachnoid Mater
If you are using a _____ solution, you may not see a swirl.
Isobaric
When is the Paramedian Approach utilized?
-Patients unable to flex/arch back well
-Older patient believed to have calcified ligaments
-After multiple unsuccessful midline attempts
What is the technique for the Paramedian Approach?
-Find the spinous process and walk laterally 1-2 cm, and down 1 cm
-The angle of the needle should be pointed into midline at about a 45 degree angle cephalad, and 15 degree angle medial.
-First resistance felt is Ligamentum Flavum
What is the Taylor Approach to SAB?
-A modified paramedian approach
-Utilized with difficult anatomy (Kyphoscoliosis, Scoliosis)
-Uses the L5-S1 interspace
-Lower most prominent iliac spine to avoid the twisting or malposition of the vertebrae.
What are the Pros of a SAB?
-Fast acting
-Dense block (motor and sensory)
-Small volume/dose (minimizes toxicity)
-Less time and simpler to perform
-Less N&V, decreased stress response, decreased opioid use
-Affects reticular activating system (due to decreased sensory input from the body), so patient can become somnolent
What are the Cons of a SAB?
-Hypotension (significant)
-Can’t prolong the block
-Lack of control with the level of the block
What is the Subdural Space?
A potential space between the Dura and Arachnoid Mater
-Needle is inserted partially in the dura, with the lumen not in CSF (won’t be able to aspirate CSF)
-Blocks in this space are variable. Can be unilateral, full motor, and/or partial sensory
-Depends on the amount of drug in the space
-Delayed onset
-High block (smaller space) and drug is sent upwards, farther away from the point of injection
When does a Dry Tap occur?
If you go through the Dura and are in the PLL.
T/F: It is ok to inject when a patient complains of pain.
False; Never inject when patient is in pain, can cause nerve damage
What is Coring?
When you take a part of the skin, including the pigments from the tattoo, into the epidural or subarachnoid space.
-Modern day tattoo has inert metal salts.
-Phenolphthalein base (low allergy potential)
How do you prevent problems with tattoos over insertion site?
Can change interspace, work around tattoo.
-Also, an introducer can help this problem (Spinal needle doesn’t touch skin)
What should you do if you are unsure if the fluid coming out of the needle is CSF or LA from skin wheal?
Can always dipstick it and see if there is glucose/protein present
-Always rule this out before assuming that the Subarachnoid space is more superficial than you thought!
What are the common complications of NA anesthesia?
-Backache
-Nerve injuries (bad positioning)
-Irritation from LA or puncture site
-Hematoma
-Inability to cough
-Decreased uterine flow (careful with OB)
-Double Crush Syndrome
-CV effects (blocks SNS)
Backaches are more common with which type of NA anesthesia?
Epidural (30%) compared to SAB (11%)
What should you do if you suspect hematoma?
-Get CT Scan
-Consult neuro
-Can result in permanent injury
What causes the feeling of inability to cough with NA?
Anxiety regarding loss of feeling of intercostal muscles
What is Double Crush Syndrome?
Patients with preexisting neurologic disease are susceptible to further injury if exposed to a secondary insult.
-Occurs with diabetics or those with demyelinating diseases like Guillain-Barre
-In already injured areas or paresthesias, intrathecal anesthesia may worsen them
-Damage to myelin can occur with LA, Epi, or Needle
-Identify and chart any existing neuropathies
What are the cardiovascular effects associated with NA Anesthesia?
Sympathetic blocking effects.
-Remember: SNS runs from T2-L2 (small preganglionic fibers- B fibers)
-Causes both arterial and venous dilation (Venous > Arterial). Leads to venous pooling
-Bainbridge Reflex
-Cardiac accelerator fibers get blocked T1-T5, then the PNS becomes dominant (Marked hypotension and bradycardia***)
-Careful in patients with cardiac diseases the rely on preload
How do you prevent marked hypotension and bradycardia associated with NA anesthesia?
-Manage patient position for first 5-10 minutes of setup
-Don’t move patient after injecting block to avoid it spreading
-Spinal is harder to control than Epidural
What is the Bezold-Jarisch Reflex (BJR)?
-Activated with NA by effects on Chemoreceptors and Mechanoreceptors in the Left Ventricle
-Reflex is triggered by decrease in venous return and decreasing LV filling pressures
-Profound bradycardia, hypotension, and CV collapse
What is the link between Serotonin and the Bezold-Jarisch Reflex?
Some studies are showing that the BJR is activated by Serotonin.
-Serotonin (5HT3) Inhibitors like Ondansetron may be effective in preventing the BJR or lessening the effects***
What are positioning modalities to treat hypotension/bradycardia associated with NA Anesthesia?
-After the SAB has set up (5-10 minutes), you can try a slight head down or lift legs up for auto transfusion (these must be done after block is “fixed”***)
-If you put the head down too early, the block will move higher
When do you treat a patient for hypotension?
If not within 20% of normal BP (within 30% for HTN people)
What is important to know regarding fluid replacement with NA?
-10-15 mL/kg of Crystalloid
-Colloids (controversial)
-Careful in elderly
What pharmacologic therapy can be instituted to treat hypotension and bradycardia?
-Ephedrine (Alpha 1 vasoconstriction + Beta 1 increased in HR and Contractility). Start with 10 mg
-Phenylephrine (Alpha 1 - must dilute in syringe. Give 40 - 80 mcg at a time)
-5HT3 inhibitors (Ondansetron) - 4 mg
-Atropine/Epinephrine
What level is a Total Spinal?
-Classified as above mid cervical
-Paralysis of the Phrenic nerve with subsequent apnea
-Secure airway and hemodynamic support until level recedes
-Usually if you get a good BP back, breathing resumes.
What is the most common cause of apnea with a Total Spinal?
Most commonly, apnea is due to brainstem ischemia, not phrenic nerve paralysis. If you get the BP back up, usually breathing resumes.
What are the causes of a Total Spinal?
-High spinal
-Accidental epidural injection into the Subarachnoid Space with a large volume of LA
What are the Respiratory effects of NA Anesthesia?
-Clinical significant alterations are usually minimal
-Tidal volume largely preserved with a small decrease VC probably due to blockade of the accessory muscles decreasing ERV
-Reassure patient that they are breathing (can’t feel it)
-Main effect is on exhalation
What about NA Anesthesia and COPD patients?
COPD patients may not be the best candidates for this or may need LMA in addition to spinal.
-Depend on accessory muscles (intercostal and abdominal) to actively inspire and exhale
-Impaired coughing and clearing of secretions
-Risk vs benefits
What are other causes (besides anesthesia) of neurological issues in the periop environment?
-Birth
-Trauma
-Retractors
-Positioning
-Exacerbation of a preexisting disease
Get neuro consult immediately
-Can be transient or permanent
Describe Transient Neurological Symptoms (TNS) or Transient Radicular Irritation (TRI)
-Pain in the legs/buttocks
-Paresthesias usually resolve in 72 hours to 6 months
-Causes: Traumatic puncture of cord, intraneural injection
-Avoid by staying away from high concentrations of Lido and/or not using Lido at all.
What is Cauda Equina Syndrome?
-Variable presentation: immediate or gradual
-Prolonged recovery from anesthesia blockade
-Motor & Sensory blockade in sacral region and lower extremities, perineal anesthesia with incontinence
-Associated with microcatheters specifically designed for continuous spinal anesthesia (postulated that this results in less dilution of LA and less spread)
What LA is no longer used for SAB due to risk of Cauda Equina Syndrome?
Hyperbaric Lidocaine - 5%/7.5% dextrose
What can you do to prevent epidural hematoma/Subarachnoid hemorrhage?
-Careful history with labs
-No NA if plt count < 100k or if Pt/PTT are over 2x normal
-Neuro consult, CT scan, may need surgery
Why do you need to remove the US gel before performing NA Anesthesia?
US gel is associated with a distinct neuro-inflammatory reaction
-Epidural Abscess, septic meningitis, and aseptic meningitis (chemical)
What are the GI effects r/t NA Anesthesia?
-Vagal tone dominance, PNS dominance
-Active peristalsis
-N/V (usually r/t hypotension - resolves with Ephedrine)
-N/V could also be due to gut ischemia or cerebral ischemia (Vomiting center)
What are the other organ system effects of NA Anesthesia?
-Cerebral blood flow is maintained via auto-regulation as long as MAP > 55
-Renal blood flow is maintained via auto-regulation as long as MAP > 55
-Urinary retention
-Endo: Partially or completely suppresses the stress response, reduces catecholamines, and blunts hyperglycemia
Management of Failed Spinal Anesthesia
-If after 15 min no typical signs of onset occur, spinal failure is likely
-Can repeat injection (With caution)
-Reposition
-IV analgesia/sedation/GA
Review slide 101
When can patients be discharged home?
When they can void, and get up/walk around without drastic changes in BP
In what order does a NA Block reverse?
-Motor movement comes back first (wiggles toes, lift legs)
-Sensation (may start to feel pain)
-Autonomic effects are the last thing to come back (this is why you have to be able to get up without drastic shifts in BP before going home)
