10-Regional Anesthesia

Question 1

Where is the epidural space located?

Answer 1

Between the dural sac and the ligamentum flavum

Question 2

What are the types of local anesthetics?

Answer 2

Amides

Esters

Question 3

What are some characteristics of local anesthetics?

Answer 3

The onset of an anesthetic is related to its pKa
The closer the pKa is to the physiologic pH the faster its action
The anesthetic used depends on the type of procedure
Bupivacaine or Ropivacaine have a slow onset but longer duration and can be used during labor
While lidocaine with its short action can be used for less time consuming procedures
Cocaine is used in certain procedures but has vasoconstrictive effects

Question 4

What are the MOA of local anesthetic?

Answer 4

Most local anesthetics bind go the alpha subunit from inside the cell and inactivate the channel
Increase concentration of local anesthetic causes a decrease in impulse conductions and action potential magnitude and an increase in the threshold for excitation

Question 5

What is the difference between spinal anesthesia and epidural injection?

Answer 5

Spinal anesthesia is an injection into the subarachnoid space
The lack of covering in the subarachnoid makes the spinal anesthesia faster acting than epidural that has to go through layers surrounding the nerve roots

Question 6

What is a differential blockade?

Answer 6

The effect of anesthetic on nerve fibers varies with size, myelination and duration on contact
Sympathetic blockade is typically 2 segments higher than sensory blockade which is 2 segments higher than motor blockade

Question 7

What are the steps in the preparation for the procedure?

Answer 7

Match the choice of anesthetic with the surgical need and patient
Use sterile technique
Have rescue equipment on board and ready

Question 8

How do you position the patient for the procedure?

Answer 8

Sitting or lateral recumbent
Usually positioning is a poorly managed part but one of the most important
In lateral recumbent, the patient is parallel to the table with thighs and neck flexed
When sitting, the patient has a stool for footrest and pillow in their lap with an arched back and squared hips

Question 9

What are the tools used?

Answer 9

Cutting or non cutting needles can be used
Smaller needles size decrease the risk of headache but also take longer to administer or retrieve fluid(csf)
With spinal anesthesia , the needle should be advanced slowly to sense a change in resistance
For epidural anesthesia, the loss of resistance technique or hanging drop test should be used

Question 10

What are the side effects/ complications of anesthesia?

Answer 10

Post dural puncture headache is the most common
Block of sympathetic fibers results in vasodilation of venous capacitance and decreases venous return to the heart
High sympathetic block(T1-T4) causing bradycardia, and rare cardiac arrest
Respiratory side effects are not common due to the fact that the phrenic nerve innervates the diaphragm
High levels can impair accessory muscles of respiration important in patient with severe chronic lung disease
Urinary retention
Toxicity from intravascular injection

Question 11

What are the characteristics of the post dural puncture headache?

Answer 11

Typically bilateral, frontal or retro orbital to occipital extending into the neck
Exacerbated by sitting or standing
Relieved with lying flat
Onset 12-72 hours following procedures
More common with young age, female gender, pregnancy, cutting and larger gauge needles
Due to leakage of CSF

Question 12

What are the treatments for post dural puncture headache?

Answer 12

Conservative treatment consists of recumbent position, analgesics, fluids and caffeine
Definitive treatment involves an epidural blood patch by injecting patient blood into the epidural space near the puncture which will clot and plug the abnormality

Question 13

How does total or high blockade occur?

Answer 13

Unintentional intrathecal injection of epidural dose

Treated by maintaining airway, ventilation and circulatory support

Question 14

What are the effects of anesthetic toxicity?

Answer 14

Seizures
Unconsciousness
Hypotension
Cardiovascular collapse

Question 15

How to prevent total/high blockade and toxicity?

Answer 15

Careful aspiration and use of a test dose
Test dose is a small amount of anesthetic used
If site is intravascular or too high early signs of toxicity such as ringing in ears and metallic taste will manifest

Question 16

What is the benefit of anesthesia?

Answer 16

Besides pain, it will partially or fully suppress state of hypertension, tachycardia, suppressed immune response caused by the surgical trauma
Decrease perioperative arrhythmias
Reduce the incidence of ischemia

Question 17

What is the indication for neuraxial blockade?

Answer 17

Useful as primary anesthetic for surgery below the umbilicus

Can be alone or in combination with general anesthesia for most surgeries below the neck

Question 18

What are the absolute contraindications of neuraxial blockade?

Answer 18

Infection at the site of injection
Patient refusal
Coagulopathy or other bleeding disorders
Severe hypovolemia
Increased intracranial pressure
Severe aortic or mitral stenosis

Question 19

What are the relative contraindications?

Answer 19

Sepsis
Uncooperative patient
Preexisting neurological deficits (demyelination)
Stenotic valvular heart lesions
Severe spinal deformity

Question 20

When to stop taking certain drugs for anesthesia?

Answer 20

Clopidogrel (plavix)-5 to7 days before
Prasugrel (effient)- 7 to 10 days before
Coumadin-5 days before plus normal INR
Unfractionated heparin- 4-6 hours before
LMWH- 12 hours before, for high dose: 24 hours