Epidural Anesthesia Flashcards
What is an advantage of an epidural over a spinal?
Slower onset of hypotension than spinal
What are some advantages of leaving the catheter in the epidural space?
May use as single injection or continuous
Anatomical distribution may be precisely controlled
Excellent postoperative analgesia
Why is an epidural a popular option for those in labor?
It provides segmental block/band of analgesia
How does an epidural reduce the surgical stress response?
It blocks afferent impulses toward the cord
How does an epidural inhibit hormonal and metabolic consequences?
Blocks afferent impulses from the operative site to the brain and efferent autonomic pathways to the liver and adrenal gland
What makes an epidural more difficult than a spinal?
There is no end point, in a spinal you’ll see CSF
How long can an epidural take to establish surgical level of anesthesia?
10-20minutes
Why might an epidural be beneficial in an amputation?
Decreased incidence of phantom limb pain
How many total vertebrae are there?
33 Cervical 7 Thoracic 12 Lumbar 5 Sacral 5 -fused Coccyx 4-fused
What is the name of the largest opening for needle passage?
Interlaminar foramen “interspace”
What are characteristics of a thoracic vertebrae?
Steep angle and length of spinous process
Body is heart shaped
Where does the supraspinous ligament extend?
C7-sacrum
What is the thickest, broadest ligament in the lumbar region?
Supraspinous ligament
Where does the interspinous ligament extend?
Extends full column length
Where does the Ligamentum flavum extend?
From the base of the skull to the sacral hiatus
What is the average depth of the epidural space?
5.3cm
Range 2-9cm
What are the borders of the epidural space?
Anterior border is the dura
Posterior border is the ligamentum flavum
Where does the epidural space extend?
From the foramen magnum to the sacral hiatus
What is contained in the epidural space?
Nerves, Fat, lymphatics and veins (epidural plexus)
Why is more volume injected when administering an epidural?
You have to give enough to fill the entire space both anteriorly and posteriorly (spotty if not covered completely)
What are the layers to get to the epidural space?
Skin Subcutaneous tissue/fat Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space
What anatomical land mark is associated with C7?
Most prominent vertebrae above the scapula
What anatomical land mark is associated with T7?
Inferior angle of the scapula
What anatomical land mark is associated with L4?
Inferior aspect of the iliac crest
How many nerves innervate the dermatomes?
8 spinal nerves
Where should the epidural needle be inserted for a Mastectomy?
T1
Where should the epidural needle be inserted for a Thoracotomy?
T4
Where should the epidural needle be inserted for an Upper abdominal procedure?
T7-T8
Where should the epidural needle be inserted for a Lower abdominal procedure?
T10
Where should the epidural needle be inserted for a lower extremity above the knee procedure?
L1-L2
Where should the epidural needle be inserted for a lower extremity below the knee?
L3-L4
Where should the epidural needle be inserted for a perineal procedure?
L4-L5
Where are sensory innervation landmarks for the clavicle?
C4
Where are sensory innervation landmarks for the nipples?
T4
Where are sensory innervation landmarks for the Xiphoid?
T6
Where are sensory innervation landmarks for the umbilicus?
T10
Where are sensory innervation landmarks for the inguinal ligament?
L1
Where are sensory innervation landmarks for the iliac crest?
L4
What are the characteristics of an epidural needle?
16-18g, 9cm long, 11cm to the distal hub with markings at 1cm intervals
What is the purpose of the epidural needle having a directional tip?
Facilitates catheter threading in the direction of the needle tip
Why should the provider never remove the catheter through the needle?
Run the risk of shearing the catheter into the patient
When removing an epidural catheter what feature needs to be checked and intact?
The tip of the catheter, it is typically marked blue
What two positions are typically used when positioning a patient for an epidural?
Sitting up and Lying on side
What can occur if pre solution is introduced into the epidural space?
Inflammation or arachnoiditis, wipe the solution after it dries with a sterile gauze
What percentage of lidocaine should be used to make the skin wheal?
1%
What occurs when the loss of resistance technique is used for an epidural when passing thought the ligaments?
The plunger of the syringe is resistant until the ligaments are passed
How does the provider know they are in the epidural space when using the hanging drop technique?
The saline drop is sucked in when the epidural space is entered
How can saline vs CSF be differentiated if fluid were to flow out of the needle in an epidural attempt?
Take a drop of the fluid on the back of your hand and sense the temperature:
If the fluid is warm its probably CSF
If the fluid is cold its more than likely the saline you injected
What is an indicator that the catheter is flush withe the needle tip?
When the first black mark is flush with the hub
How far do you advance the catheter past the needle tip?
2-4cm
Before securing the catheter what should be completed?
A test dose should be given to see if the catheter is still in the correct position. May need to manipulate the catheter
What is a typical test dose given to a patient?
3-5mL of local anesthetic containing epinephrine
What can occur is the catheter is not in the correct place?
Spinal anesthetic may occur if in the subarachnoid space
Increased HR may indicate the catheter is intravenous
What can be done if you are unable to thread the catheter?
Rotate the needle slightly to change the bevel
What should be done if blood is present in the catheter?
More than likely in an epidural vein, take out the needle and catheter and try again
What are indication for a caudal approach?
Hemorrhoidectomy
Pediatric –> inguinal herniorraphy, circumcision, scrotal procedures
What is the best position for the caudal approach?
Prone with the legs spread and externally rotated to optimize landmarks
What are the landmarks for the caudal approach?
Posterior superior iliac spines
Sacral cornua
These three points for a triangle
What does a caudal approach have such a high failure rate?
The sacral anatomy varies greatly in adults
What population is a caudal approach ideal in?
Pediatrics
What are you puncturing when attempting a caudal approach?
Sacral hiatus and then advancing 1-2cm
Why does the provider typically feel when injecting into the sacral hiatus?
To make sure they are not injecting into the subcutaneous tissues, will feel skin rise
If the patient begins to complain of severe pain when injecting into the sacral hiatus where is the prover more than likely injecting the local anesthetic?
Subperiosteum, the periosteum is very sensitive
What factors are the basis of epidural dosing?
Procedure
Desired segments blocked
Needle insertion
How do you dose epidurals?
Based on the region at which the needle is inserted
What is the dosing if the needle is being inserted in the thoracic region?
0.7mL/segment
What is the dosing if the needle is being inserted in the lumbar region?
1mL/segment
What is the dosing if the needle is being inserted in the caudal region?
2mL/segment
Why does the spread of an epidural block seem to occur faster in the cephalad direction?
The thoracic roots are smaller in diameter than the larger lumbar and sacral
What is the purpose of adding a vasoconstrictor to an epidural?
To decrease systemic absorption
How does age affect the epidural space?
The older the age, the smaller the epidural space
Why isn’t baricity a factor with epidural anesthesia?
Baricity refers to mixing a solution with CSF which should not occur with an epidural
Define two-segment regression.
The time it takes for a sensory love to decrease by two dermatome levels
How can you redose an epidural if two segment regression has occurred?
Inject 1/3 to half of the initial activation dose
How many mug/mL is in 1:200,000 of epinephrine?
5mcg
How is epinephrine dosed with local anesthetics?
5mcg/mL of LA
What is the difference in muscle relaxation of an epidural compared to a spinal?
Epidurals don’t get significant motor blockade like spinals do
What is the percent of motor blockade seen with 2% Lidocaine with and without epi?
Lidocaine: 9+/-18%
Lidocaine with Epi: 37+/-20%
What is the percent of motor blockade seen with 2% Mepivacaine with epi?
30%
What is the percent of motor blockade seen with 0.5% Bupivacaine?
29+/-29
How can the provider tell if a complete motor block has occurred?
The patient is unable to move feet or knees
How can the provider tell if an almost complete motor block has occurred?
The patient is able to move the feet only
How can the provider tell if a partial motor block has occurred?
The patient is able to move their knees
How can the provider tell if no motor blockade is present?
The patient has full flexion of the knees and feet
What are the benefits to using a combined spinal-epidural technique?
Offers effective, rapid onset analgesic with minimal risk of toxicity or impaired motor block
Provides continuous technique with epidural catheter
Which type of nociceptive pain requires a more dense block?
Somatic, burning, sharp pain
What epidural opioid has a slow onset, long duration, high CSF solubility and extensive CSF spread?
Morphine
What type of opioid is never permitted in an epidural?
Opioid with preservatives
What are the advantages of epidural morphine?
Prolonged single dose
Extensive spread
Minimal dose compared to IV administration
What are some disadvantages of epidural morphine?
Delayed onset of analgesia
Unpredictable duration
Higher incidence of side effects
Delayed respiratory distress
What two epidural opioids are known to be lipophilic?
Fentanyl and Sufentanil
What epidural opioid is know to have a rapid onset, short duration, low CSF solubility and spread?
Fentanyl and Sufentanil
What are some advantages of epidural fentanyl and sufentanil?
Rapid analgesia
Decreased side effects
Ideal for continuous infusion
What are some disadvantages to epidural fentanyl and sufentanil?
Systemic absorption
Brief single dose analgesia
Limited spread
How often should a patients BP be evaluated if receiving epidural anesthesia?
3-5minutes
What are signs that the autonomic block has occurred?
Large drop in BP
Nausea from hypotension
At what level would bradycardia be seen with an autonomic block?
T2-T5, cardio-acclerator fibers at T4
When sympathectomy occurs from T5-L1 what happens in the GI tract?
Parasympathetic outflow –> contracted gut and relaxed sphincters
What is the first line treatment for a postdural puncture headache?
Oral analgesics
Bed rest
Hydration
Caffeine infusion
What intervention can be done if conventional treatments aren’t effective against a postdural puncture headache?
Blood patch
What is the process for performing a blood patch?
Draw 10-20mL of patient’s own blood using sterile technique and inject it into the epidural space
What is the success rate of an epidural patch after the initial attempt?
90%
What are the four stages of an epidural abscess?
Back or vertebral pain increase with percussion
Nerve root pain
Motor sensory deficits or sphincter dysfunction
Paraplegia or paralysis
What is the incidence of an epidural abscess?
1:6,500-1:50,0000
What is typically the cause of an epidural hematoma?
Abnormal coagulation
What is the incidence of an epidural hematoma?
1:150,000
Where should the skin wheal be placed in a paramedian approach?
1-2cm lateral to midline directly opposite upper tip of spinous process below selected interspace
What ligaments are bypassed when utilizing a paramedic approach?
Supraspinous ligament
Interspinous ligament
When does the spinal cord end?
L1-L2
What two regions of the spinal column have convex sections anteriorly?
Cervical curve
Lumbar curve
What two regions of the spinal column have concave sections anteriorly?
Thoracic curve
Sacral curve
What are the two lowest parts of the concave sections of the spinal column?
T5 and S2
Where does the supraspinous ligament extend?
C7 to the sacrum
What is the pneumonic used to describe the most vascular injection of LA to the least vascular?
BICEPSS
Blood, intercostals, (Tracheal), caudal, epidural, plexus (brachial), sciatic, subcutaneous
