Epidural Anesthesia Flashcards
Does epidural or spinal anesthesia offer better control of the extent of motor and sensory blockade?
epidural
Distinct difference between epidural and spinal anesthesia?
epidural allows for continuous administration of anesthesia secondary to placement of a catheter
How do LA or analgesics injected in to the epidural space spread horizontally?
spread to the regions of the dural cuff, where it is able to diffuse in to the CSF and leak in to the intravertebral foramen and paravertebral spaces to achieve analgesia/anesthesia
How does epidural medication spread longitudinally?
cephalaud
Why do you have to use larger volumes of medication with epidurals than with spinals, and how much is the usual volume?
because the medication is diffusion dependent; 20 mL, spinals 1-2 mL
For an epidural where is the LA injected?
epidural space
How is the onset of an epidural in comparison to a spinal?
slower and not as dense
What do the arachnoid villi and granulations on the dural cuffs of the sleeves do?
reduce the thickness of the dura mater, which permits rapid diffusion of anesthetics from the epidural space thru the dura and into the CSF
What property of the anesthetics may account for differences in diffusion rates across the dura?
lipid solubility
Why/how does epidural anesthesia take longer to act?
medication be delivered to the subarachnoid space by the process of diffusion and spread
This type of anesthesia is useful for procedures of unpredictable duration, prolonged post op analgesia, and chronic pain control?
epidural
Only anesthesia available to relieve labor pain and minimally effect baby/maternal physiology?
epidural
What type of block is an epidural (ie sensory or motor)?
sensory w out motor block
What can you dilute the LA with in epidural?
opioid
5 indications for epidural?
longer lower dermatome surgery, postop analgesia, labor analgesia, pain treatment, combo techniques
Where does needle go in spinal versus epidural?
spinal: practitioner seeks CSF by piercing the dura; epidural: tip of epidural needle seeks fat filled space deep to ligamentum flavum and shallow to the dura
Typically, an epidural catheter is what size in comparison to the needle?
2 gauges smaller than the needle
What are the uniport and multiport epidural catheters?
uniport: single holed, open ended; multiport: lateral holed, closed tip
Studies show a significantly lower incidence of inadequate analgesia and higher incidence of inadvertent IV cannulation with what epidural catheters?
multiport
Manufacturers recommend that epidural catheter should be threaded how many cm into the epidural space?
3-5
Not threading catheter far enough in to the epidural space can cause? And threading it too far can cause?
inadequate analgesia; IV cannulation
The standard epidural needle is what size and how long?
16-18 g and 3 inches long
The blunted bevel and gentle curve of the epidural needle allow for what?
allow passage thru the skin and ligamentum flavum and abut against the dura, rather than penetrate thru the dura
Two most common epidural needles?
Tuohy and Hustead
Difference between Tuohy and Hustead needle?
Tuohy is easiest for novel practitioners and its blunt, curved tip is less likely to penetrate the subarachnoid space. Hustead has a less pronounced 15 degree curvature which can more easily pass thru the skin and ligamentum flavum
This is a third epidural needle and it is preferred when catheter placement in to the epidural space is difficult, the angle is steep?
Crawford
This type of epidural catheter has been implicated in a higher ratio of accidental dura punctures?
Crawford
Any procedure below the diaphragm would get what type of epidural?
lumbar
2 approaches to lumbar epidural?
midline or paramedian
This epidural is most commonly used for postop analgesia?
thoracic epidural
This approach with a thoracic epidural is usually easier?
paramedian
Thoracic epidural can be used as a single shot for?
chronic pain management
Big risk with thoracic epidural?
spinal cord injury
How is the ligamentum flavum in the cervical region?
very thin
Position for cervical epidural?
sitting position, neck flexed
What type of approach do you do for cervical epidural?
midline
What type of approach do you do for thoracic epidural?
midline or paramedian
Single shot cervical epidural used for?
chronic pain management
Standard of care for cervical epidural is evolving to be?
placement under fluro
This type of epidural is placed in the sacral epidural space found at the sacral hiatus?
caudal
3 positions to do caudal epidural in?
lateral, prone, jackknife
2 types of surgeries which would use caudal epidural?
perineal and sacral
3 techniques to find epidural space?
fluoro, loss of resistance, hanging drop
How do you do the hanging drop technique?
hub of needle is filled w fluid so drop hangs from it, negative pressure in epidural space sucks fluid into the needle
How do you do the loss of resistance technique?
attach fluid or air filled syringe to needle after entering interspinous ligament, advance needle mm by mm while tapping on plunger, sudden loss of resistance is felt when entering space
Most common method used to enter the epidural space?
loss of resistance
Stylet of epidural needle is removed once entering?
when needle is placed thru intraspinous ligament, or ligamentum flavum
What type of solution do you put in syringe for loss of resistance technique?
NS or air
As the needle passes thru the ligamentum flavum what happens to resistance?
it increases
Profuse return of CSF results when penetration of epidural needle is where?
dura
3 types of tests which can confirm CSF vs NS or LA?
CSF is warm, NS or LA is room temp, glucose test paper detects glucose in CSF, LA mixed with similar amt of thiopental immediately forms a precipitate
What frequency is the US probe used for spinals and epidurals?
low frequency (2-5 Hz)
Ultrasound transverse and midline approach allows for what?
midline: identify midline and assess distance; transverse approach assessment of interspace
2 positions for US epidural placement?
lateral with knees flexed and hips or sitting position with back curved out to present spines
Where do you start with placement of US for epidural?
sacral region, 3 cm lateral to left of midline and slightly angled toward center of spine
First anatomy to identify using US for epidural?
identify sacrum, which is the white hyperechoic bone
When using US, after you identify the sacrum, what do you do?
move US cephalaud until hypchoic sawlike images (articular processes) are seen
Once the articular processes are seen, what do you do when using US?
mark exact level of spinous processes
When using US, what is between the sawlike images?
vertebral interspaces
When using the US, after you identify the exact level of spinous processes and and each interspace, what do you do?
Place the probe horizontal along the midline of the spine at the marked levels of the interspace and spinous processes