Epidural Anesthesia Flashcards
What is an epidural?
A central Neuraxial block much like a spinal anesthetic, however there is variation is the space that the medication is administered.
What are some of the advantages of Epidurals vs general anesthetics and spinals?
Patients are alert much earlier, they can be fully conscious, or sedated. A lower incidence of PONV than GA because not giving gases or heavy narcotics. Slower onset of hypotension than with a spinal (slower sympathectomy). The epidural allows us to place an epidural catheter for a one shot anesthetic or a continuous epidural (better control in the level of blockade and anatomical distribution may be precisely controlled). Sensation below and above the band. Also excellent postoperative analgesia possible.
Why are epidurals popular for child birth?
Popular for pain control during childbirth they because they create a band of anesthesia so the mom can still move her legs, but still gets analgesia. Analgesia possible without motor block (very dilute concentrations of local anesthetics.) This allows for autonomic and sensory blockade without motor blockade.
Why are epidurals advantageous in orthopedic cases?
It reduces MAP/Venous pressure so there is less blood in the surgical field and less blood loss. And lower risk of postoperative thrombosis
How is the afferent impulse toward the cord advantageous?
It reduces surgical stress response of the patient. Prevents transmission of signals from surgical site to brain.
Why is the stress response important during the surgical procedure?
The release of cortisol will cause multiple side effects - increased blood glucose, suppression of immune system, etc. An epidural blocks this response, so wound healing is improved and surgical site infection risk decreased.
In what ways can we reduce the endocrine response?
By using LA, we inhibit hormonal and metabolic consequences. We can block afferent impulses from operative site to brain, or if the block is in the area that controls the efferent autonomic pathways to liver and adrenal gland blocked.
Will opiates alone in the epidural control the endocrine response?
No, must achieve a conduction blockade with LA.
What are some of the disadvantages of an epidural?
The technique is demanding and time consuming. You need to be proficient with the technique and anatomy. There is also no defined endpoint (you do not want to see CSF), meaning you never know if you are really in the space. The onset is slower (advantage or a disadvantage)- have to wait to set up before you can do surgery. Time (10-20 min)/money/mom in labor and ready for pain relief. Sympathetic block can cause profound hypotension (nausea). Surgeons complain, say it takes to much time.
How can we be more efficient with epidurals?
Place it early and be ready ahead of time.
What are some indications for epidural?
Patient has a full stomach, so you can use it to maintain protective airway reflexes. This can be an issue if the epidural wears off, then you have to put patient to sleep.
Upper airway challenge (avoids airway manipulation) - but again you need a functional epidural. Urologic procedures TURP, Prostatectomy, Obstetrics (can give sensory blockade, +/- motor blockade if the surgery progresses to a c-section - simply dose higher for anesthesia. Lower limbs, pelvis, perineum and lower abdomen. Can use for upper abdominal and thoracic procedures as well, but it can be much more difficult. More difficult to avoid patient discomfort. Hip and knee surgery (decrease blood loss and DVT), vascular reconstruction of lower limbs, Amputation (decrease incidence of phantom limb pain), thoracic trauma (improved resp function).
How do we know what patients to place an epidural in?
Two things: 1- Surgeon skill (do they understand the implications of placing an epidural instead of GA. The patient may move a little. 2- The patient themselves (are they a candidate, are they demanding one, do they have fears (do not coerce them) do they want to be in control, fear of not waking up, +/- sedation during prodecure? Age is an issue (younger patients) is 14 year old acting mature or are they immature (judgement call), do they want to go home immediately (some may not want to wait for it to wear off)
What are some absolute contraindications for epidural?
Patient refusal, infection at the site (seeding infection in CNS), Coagulopathy (check coags preop, are they on anticoags), platelet count (are they functional) check history for gum bleeding when brushing teeth, spontaneous nose bleeds, bruise easily. Severely hypovolemic (trauma, dehydration), Unstable CNS disease (Elevated ICP), if you puncture the dura accidentally you can have a brain stem herniation. Severe aortic or mitral stenosis (they have obstructive cardiac outflow downstream so do not drop afterload with sympathectomy from epidural, documented allergy to local anesthetics (some will have amide allergy, esters more often) it may have been a normal epi response at dentist.
What are some relative contraindications?
Uncooperative patient/ psychiatric disease (they can get crazy during case), Septicemia/Bacteremia (risk of seeding infection in CNS), pre-existing CNS disease (MS), they might blame your anesthetic, Stenotic valvular lesions (depends on severity, take away the afterload, chronic headaches or backache (don’t want to be blamed later), morbidly obese (technical placement), spinal column deformation (scoliosis, difficult)
How many vertebrae are there and what is the breakdown?
33 Vertebrae 7 Cervical 12 Thoracic 5 Lumbar 5-fused Sacral 4-fused Coccyx Size and shape vary dramatically
What makes epidurals unique from spinals?
You can perform an epidural at any level from cervical vertebrae to sacrum.
Where will most epidurals be placed?
In the lumbar region. Can do thoracic or caudal when get more expertise.
What are the bumps on the back that we can feel?
The spinous processes.
Why are the lamina important anatomically?
It is an important landmark that is commonly hit with the needle. (I’m bumping into Oss)
When is the Transverse process important to know about?
When we get into lumbar plexus anesthesia and paravertibral anesthesia
Where do the spinal nerves come out?
The intervertebral foramen. Just important to know as an anatomical landmark, it is not anything we will be aiming at.
What is the anatomical name of the space we are aiming for when navigating between the vertebrae?
The interlaminar foramen. (Largest opening, interspace, gap for needle passage)
What are the differences in the Lumbar and Thoracic vertebrae?
The lumbar have a much more horizontal spinous process vs the more vertical spinous process of the thoracic vertebrae. It is much harder to place in the thoracic area because of the angles that have to be utilized. (para median approach)
What is the ligament that runs on the spinous processes in your back? And where does it extend from?
The supraspinous ligament. C7 all the way to the sacrum (Needle through rice crispies, thick and broad in the lumbar region)
What is beneath the supraspinous ligament? And where does it extend?
The Interspinous ligament. The whole vertebral column. Thin and membranous, but thicker in lumbar region.
What is the name of the ligament that is penetrated after the Supra and Interspinous ligament? Where does it extend
The ligament of Flavum (yellow ligament latin). Runs from the base of the skull to the sacral hiatus
Where is the posterior longitudinal ligament?
It is on the other side of the spinal column. You have advanced the needle way to far.
Where is the anterior longitudinal ligament? And what important structure is in close proximity to it?
On the anterior side of the vertebral body. The aorta or vena cava
What is the epidural space?
A potential space. Average depth is 5.3 cm but ranges 2-9 centimeters. (Epidural has markings that tell you how many cm deep you are)
What is contained in the epidural space?
It is highly vascular and contains a lot of epidural fat. Lymphatics, nerves
The epidural space is bound anteriorly by the ____ and posteriorly by the _____? It extends from the ______ to the ____ _____?
Dura, and ligament flavum. It extends from the foramen magnum to sacral hiatus.
What is important to note about the amount of LA placed in the epidural space?
You need enough volume to fill the posterior and anterior epidural space or your block can be spotty. The dose is volume based.
What is a very important landmark to know in the vertebral column?
C7- the most prominent vertebrae above the scapula, the inferior angle of the scapula should be T7. Superior aspect of the illiac crest is L4
Why are landmarks important for epidural placement?
They help denote how we calculate dosages and how we determine where to place our epidural and what volume of LA to give to the patients.
What do we have to know before we place an epidural?
The operative site (skin incision), this allows us to determine a insertion point and what sensory needs to be blocked.
What are the landmarks we should commit to memory for sensory innervation?
C4 - Clavicle T4 - Nipples T6 - Xiphoid T10 - Umbilicus L1 - Inguinal ligament L4 - Illiac crest
In preparation for an epidural, what drugs are important to have?
Vasopressors to treat the induced sypothectomy
Sedatives/Narcotics (maybe) not for OB, but in the OR you may use them for sedation of patient
LA of choice (what is the purpose of the epidural - anesthetic or analgesic) High concentration local anesthetic are for motor blockade and anesthesia purposes. If for analgesia, you will use weaker concentrations of LA.
What are the supplies that are needed?
Epidural kit, tape to secure catheter, resuscitation if patient goes apneic (in case of intravascular injection), functional IV. Supplemental O2 (maybe), Monitors (Pulse Ox, NIBP, ECG
Epidural needles are usually what gauge and how long? What are the marking measurement intervals?
16-18 guage, 9 cm long (needle shaft), 11 cm from the distal hub of the needle to needle tip. Markings at 1 cm intervals
Tip is curved 15-30 degrees. Tip is always in same direction as the hub.
The loss of resistance technique utilizes what?
A glass syringe
What should you never do once you have inserted the catheter through the epidural needle?
Never pull the catheter back through the epidural needle, the catheter can sheet off in the patient. Always pull the two out together. Look at the tip of the catheter when you pull it out. It should be blue. If not, it may be in patient. (Epidural catheter removed intact, sheer tip noted.
The line that connects the illiac crest will intersect which vertebrae?
L4
Common tray set up.
From Right side - LA, Normal Saline, Red lettering on white label vial is test dose, blue lettering 1% lidocaine for skin local (3 cc with 25 gauge needle), 20 cc syringe for LA for epidural, behind that a yeallow square sponge that attaches to patient skin between skin and catheter, 18 gauge needle, epidural needle, filter straw for drawing LA and glass viles, Glass syringe, 3 cc syringe, circular blue filter, epidural catheter inside plastic container, drapes, sponges, labels, prep sponges and betadine.
How do you prep the patient?
Tell patient going to paint bulls eye on back with a scratchy cat tongue. Circular fashion. Tilt sponge downward so it does not run on fingers. Throw away sponge after use.
