Spinal and Epidural Blocks Flashcards
Important thoracic landmark
T7 is at the inferior angle of the scapula
Important cervical landmark
C7 is the big bump you feel at the top of your back
Important lumbar landmark
top of iliac crest is at L4/5 (called Tauffier’s Line)
Why is it easier to do sacral or coccygeal blocks in pediatric patients?
Because the bones have not fused yet.
What is the point of having a patient arch their back for an epidural or spinal block?
It allows the spinous processes to spread apart a little more so that you have more room for your needle
At what angle should you insert your needle?
cephalad
What are the levels you pierce when you insert the needle?
skin – subQ tissue – supraspinous ligament – intraspinous ligament – ligamentum flavum
Where is the thickest part of the ligamentum flavum?
3-5mm thick at L3
Why is there a lower chance of hitting the spinal cord in a typical epidural block around L4/5?
Because the spinal cord has terminated around L1
How do you know that you’re in the subarachnoid space?
Because you should have CSF return through your needle
What is an important factor in dosing an epidural block for a woman in labor?
want to give a dose strong enough to block sensory but not too strong to block motor
What type of spinal nerve roots are more easily blocked?
dorsal roots - a little bit bigger, greater surface area
What happens if you administered a dose of anesthetic meant for T4 but it spread up to C8?
Administer oxygen, provide reassurance to the patient, give some fluid volume, get emergency drugs ready in case you need to intubate, reverse trendelenburg to prevent further spread of the drug
@C6 you begin to lose your sense of breathing
What is the main source of blood for the spinal cord?
anterior spinal artery
Spinal anesthesia is also known as
Sub Arachnoid Blocks (SAB)
Where is spinal analgesia injected?
into the CSF
Which type of block will have a more profound autonomic response?
Spinal - it works almost immediately and can drop HR and BP
What are you primarily blocking during a neural anesthesia?
the nerve roots (preferentially just sensory and not motor)
What are some disadvantages of neural blocks?
hypotension, inexperience of the provider, length of the case
What are some advantages of neural blocks?
decreased metabolic response to the stress of surgery, decreases post-op nausea, decrease post-op pain, allows patient to stay awake and avoid airway manipulation
Anatomy considerations for nerve blocks?
scoliosis, contractures, obesity
Age considerations for neural blocks
extreme high or low ages will require specific doses for the analgesia
Pregnancy considerations in neural blocks
pregnant women have decreased venous return and venous pooling which may contribute to profound hypotension. This hypotension will also affect the fetus. There is also reduced epidural space in pregnant women
What are some important cardiac considerations with neural blocks?
some cardiac patients rely on strong HR or BP, when you decreased this (especially in valve patients) the autonomic effects will be more profound.
In COPD they rely on respiratory muscles innervated by thoracic vertebrae and you may knock these out in certain blocks
Can you give additional doses of spinal anesthesia?
NO - the needle comes out after you give the medication
What are the absolute contraindications to a neural block
patient refusal, anticoagulation issues, infection near area of needle insertion, high ICP, hemorrhage or hypovolemia, meningitis, hysteria, CNS disease (like LE weakness)
What are some CV effects of neural blocks?
decreased CO, decreased SVR, venous dilation, decreased HR, decreased MAP
what are some GI/GU effects of neural blocks?
20% have N/V, urinary retention, no effects on the liver
What are some metabolic effects of neural blocks?
decreased catecholamine release, may cause shivering, delayed cortisol secretion
How do you position a patient for a neural block?
Lateral - lying on the side you want to block (will cause pooling of the drug), thighs to abdomen and head to knees in a C position
Sitting - hunched over in a C position… allows for better midline accuracy.
What volume of fluid should every patient receive before a neural block?
500-1000mL crystalloid
Should you give sedation to an OB patient before a block? Why?
No - the sedation may cause amnesia (forget the birth) and the sedative effects will reach the baby as well
What is the advantage of pencil-point needles? (Sprotte needle)
helps push aside dural fibers and reduces the chance of post-dural headache. You should hear a pop as you go through the dura.
What are some features of cutting needle (Quincke)?
won’t hear the “pop”, bevel must be inserted sideways to prevent cutting of the ligaments, more common in spinal anesthesia, increased risk of post dural headache
must turn the needle 4 times to check for CSF in every direction
when would you use a paramedian approach for a spinal block?
in the elderly population when the patient cannot flex enough to separate the spinous processes (r/t calcifications in the bone)
what are the borders of the epidural space?
ligamentum flavum (superficial) and dura mater (deep)
What are the borders of the subarachnoid space?
arachnoid mater (superficial) and pia mater (deep)
At what angle should you insert the needle in a paramedian approach?
10-15 degrees laterally
If you’re attempting to give an epidural block and you puncture the CSF… what should you do?
withdraw the needle, immediately lay the patient flat, give fluids to prevent PDH
what is the distance from the skin to the ligamentum flavum in a typical adult?
4-6 centimeters
Once you realize that you’re in the epidural space and after the LOR technique, how much farther should you advance the catheter?
2-3 centimeters
What is your first step once you think your catheter is in the right space?
ASPIRATE - if you have blood or an oily liquid in the syringe (CSF) in the syringe, don’t inject
What determines spread in spinal anesthesia?
density, baracity (hyper/hypo/isobaric), specific gravity
How do you create a hyperbaric anesthetic?
mix anesthetic with dextrose and it will settle in dependent areas
specific gravity >1.11
How do you make a hypobaric anesthetic?
mix the local anesthetic with sterile water
specific gravity <1.005
How do you create an isobaric anesthetic?
Mix the local anesthetic with CSF
what are the discharge criteria for spinal and epidural blocks?
spinal - comfortable and stable VS, 4 dermatome regression
epidural - ambulate without orthostatics, able to void
what is a major limitation of caudal anesthesia?
can’t be used in adults, difficult to maintain sterility if a catheter is placed
if you suspect the patient has an epidural hematoma.. what is your first step?
CT scan and then back to the OR with neurosurgery to evacuate the clot
What are some PDPH risk factors?
young, female, caucasian, large needle, multiple puncture attempts, dehydration, pregnancy, cutting needle
What causes PDPH?
when CSF leaks out, the brain compensates for the loss of volume by massive cerebral vasodilation
What are some treatments for PDPH?
lay flat, abdominal binder, blood patch, hydration, oral analgesics, caffeine
what are the hold parameters for LMWH if you are planning to give the patient a neural block?
hold for 10-12 hours both pre and post procedure
what are some S&S of local anesthetic toxicity?
tinnitus, circumoral numbness, restlessness, slurred speech, vision changes, seizures, CNS depression/apnea/hypotension, cauda equina syndrome
