Spinal Anesthesia Flashcards
1
Q
what is a spinal anesthetic?
A
- reversible chemical blockade of neuronal transmission produced by the injection of a local anesthetic into the CSF
- aka = subarachnoid block OR intrathecal block
- result = temporary interruption of autonomic, sensory and motor nerve fiber transmission
- takes place at the ventral and dorsal nerve roots
2
Q
first spinal anesthetic
A
- August Bier
- 1898
- documented first spinal headache and N/V
3
Q
advantages of spinal anesthesia
A
- ideal for procedures from lower abdomen and caudal
- simple and versatile - block distribution without adjunct and distribution can be controlled
- reduces - surgical stress, blood loss, risk of DVT
- can provide post-op analgesia
4
Q
spinal analgesia decreases incidence of
A
- PONV
- sedation
- cognitive impairment
- surgical pain
5
Q
disadvantages of spinal anesthesia
A
- sympathetic blockade occurs 100% of the time
- block may last longer than procedure
- PDPH
- urinary retention
- regional takes “too much time”
6
Q
which procedures is spinal anesthesia beneficial for?
A
- lower extremities
- lower abdomen
- also certain comorbidities like pulmonary disease
7
Q
indications for spinal anesthesia
A
- full stomach - vomiting and aspiration less likely than with general anesthesia
- difficult airway
- minimal metabolic impact - liver disease, kidney disease, diabetes
- reduction ins systemic blood pressure - decreases risk of DVT and blood loss
8
Q
absolute contraindications
A
- patient refusal
- increased ICP
- severe aortic or mitral valve stenosis
- coagulopathy or bleeding diathesis
- severe hypovolemia
- infection at injection site
9
Q
valve area for severe AS
A
<1 cm2
10
Q
valve area for critical AS
A
<0.7 cm2
11
Q
considerations and relative contraindications for spinal
A
same as for epidural
12
Q
dural puncture usual site
A
- occur anywhere from L2 to S1
- most common is L3-4 interspace
13
Q
patient positioning for spinal
A
same as for epidural
angry cat or shrimp
flexed to open up the interspinous spaces
14
Q
specific gravity
A
density of a substance as compared to the density of water
15
Q
SG water
A
1.0
16
Q
SG CSF
A
1.003-1.009
17
Q
baricity
A
- resting position of two fluids with different specific gravity when mixed in a single container
- helps determine the potential spread of LA in the subarachnoid space
18
Q
isobaric
A
- LA same baricity as CSF
- normal saline or CSF (mixed in this)
19
Q
hyperbaric
A
- LA is heavier (more dense or higher baricity) than CSF
- mixed with dextrose
20
Q
hypobaric
A
- LA is lighter (less dense or lower baricity) than CSF
- mixed with sterile water
21
Q
most important factors that determine LA level
A
- baricity
- position of the patient
- drug dosage
- site of injection
22
Q
other factors that determine LA level
A
- patient height (short people need less)
- pregnanacy (epidural veins engorged, so need less because greater spread)
- age
- CSF volume
- curvature of the spine
- drug volume
- intra-abdominal pressure
- needle direction
23
Q
where do hyperbaric solutions settle
A
- the most dependent area of the spine
- in a supine patient this is T4-T8
24
Q
spinal procedure
A
- prepare patient, talk them through it
- position patient
- sterile procedure
- cleanse injection site with CHG
- apply sterile drape
- straddle selected interspace with middle and index fingers of non-dominant hand
- raise small intradermal skin wheal of LA with 25-27G
- small spinal needle (25 G) requires introducer, larger needles (20-22G) do not
- pass spinal needle through introducer
- advance through posterior ligaments
- you may feel two pops (flavum and dura)
- stop advancing the needle and secure the hub with your hand against the patient’s back
- remove stylet and observe flow of clear CSF
- connect syringe containing LA
- aspirate small volume of CSF to confirm placement
- observe swirl
- inject entire predetermined volume of drug in one smooth motion
- immediately remove the syringe, needle and introducer unit in one smooth motion
25
introducer
- placed before the spinal needle through the skin wheal int he midline of the lower third of the interspace
- serves to guide the spinal needle, provides stability and support for smaller gauge needles
26
what do you do if you want a bilateral spinal block?
- return patient to supine position immediately to get even spread
- slightly elevate the head
27
what do you do if you want a unilateral spinal block?
- leave patient in the lateral position for at least 3 min prior to returning to the supine position
- slightly elevate the patient's head
28
cutting needle
- designed to cut through tissue
- want to insert this with the bevel to the side so you don't puncture anything or cause dural trauma
- quinke needle
29
pencil point needle
- designed to separate tissue not cut it
- less incidence of dural trauma
- whitacre needle
30
absence of CSF with spinal
- reinsert stylet
- slowly advance 1-2 mm
- attempt to aspirate CSF
- repeat steps until CSF seen
- common practice is to advance needle an additional mm after puncture to ensure complete puncture of dura
- especially impt with pencil point needles - more common with these due to where the hole is in relation to the bevel
31
what to do if you suspect you traversed the dura
- remove the stylet and attach syringe
- gently aspirate as you slowly withdraw your needle
- may get CSF as needle tip is withdrawn into the subarachnoid space
- increased risk of PDPH
32
frank blood CSF
- does not clear, the needle tip is likely in an epidural vein
- withdraw and reposition
33
blood-tinged CSF
allow CSF to flow for several seconds it should become clear; when it does inject the medication
34
saddle block
- S2-S5
- surgery limited to perineum, perianal region or genitalia
- little autonomic effect
35
low spinal
- T 10
- low abdominal procedures and lower extremity vascular and orthopedic procedures
- block lower lumbar and sacral roots
36
most common level
- T4
- remember this is where the cardioaccelerator fibers are located
- abdominal and lower extremity procedures
37
high spinal
- C8
- block higher than T2
- bad because patient will not be able to maintain ventilation
- must intubate and take control of their airway
38
paramedian approach
- useful when patient cannot flex spine (hx spine surgery, RA, or hip/upper leg trauma)
- skin wheal 1 cm lateral and 1 cm caudal to spinous process
- advance needle toward midline
- needle passes through paraspinous muscles to ligamentum
- does NOT pass through supraspinous or intraspinous
39
lumbosacral approach
- "taylor" approach
- modified paramedian approach
- uses L5-S1 interspace
- identify posterior superior iliac spine
- make a skin wheal 1 cm medial and 1 cm caudal to the spine
- needle insertion is at a 45-55 degree angle medial and cephalad to the dorsal surface of the sacrum toward the midline of the lumbosacral foramen
40
continuous spinal
provides prolonged surgical anesthesia and post-op pain management
- dura punctured with a 17G epidural needle
- epidural cath passed through the dura into the subarachnoid space
- small incremental doses of local are given until desired level
- small, slow doses slow onset of hypotension
- total dose to achieve desired level is the same
- consider using when a wet tap occurs when placing an epidural
41
epi for spinals
- alpha 1 agonist
- 0.1-0.2 mL of 1:1000 can be added to LA to prolong DOA
- greatest effect with tetracaine
42
phenylephrine for spinals
- pure alpha adrenergric agonist slightly more effective than epi
- 0.05-0.2 mL of 1% solution (0.5-2 mg) added to LA
- greatest effect with tetracaine
43
clonidine for spinals
- NOT a vasoconstrictor
- selective alpha 2 agonist
- used when epi is contraindicated
- when mixed with lido or bupiv has synergistic effects
- central action appears to help with tourniquet pain
44
intrathecal opioids
- combo of preservative free opioids and LAs provides better analgesia than either one alone
- most commonly used = fentanyl and morphine
45
spinal fentanyl
- high lipid solubility
- binds directly to lipid elements of spinal cord
- less drug available to diffuse systemically
- provides PROFOUND analgesia
- dose 12.5-25 mcg mixed with LA
- onset 5-10 min
- DOA 2-4 hrs
46
spinal morphine
- highly polarized, not very lipid soluble
- drifts freely in CSF
- provides profound analgesia
- dose 0.1-0.25 mg mixed with LA
- onset 60-90 min
- DOA 24 hours
47
AE of spinal morphine
- itching
- urinary retention
- delayed resp depression - in approximately 6-8 hours will risk to respiratory center
