Epidurals

Question 1

What are the advantages to using epidurals?

Answer 1

• Sparing effect in other drugs
• Less systemic use of other analgesics i.e. less systemic effects
• Can provide anesthesia and analgesia for long periods of time
• Low morbidity

Question 2

Describe the lengths of analgesia vs. anesthesia propagated by using local anesthetics for epidurals

Answer 2

• Bupivicaine (0.5-1 mg/kg): 1.5-2 hr of anesthesia, 4-6 hr of analgesia (0.75%)
• Ropivicaine (0.4-1 mg/kg): same duration as bupivicaine (0.75%0
  
  • May have intrinsic vasoconstrictive effect
• Lidocaine (1-2 mg/kg): 45 min-1 hr of anesthesia, 2-3 hr analgesia (2%)

Question 3

What two factors affect onset and duration of an epidural?

Answer 3

Concentration and volume

Question 4

How does a higher concentration of an epidural drug affect onset and duration?

Answer 4

• Better blockade
• longer lasting
• exponentially faster onset
  
  • log of concentration

Question 5

How does a higher volume of an epidural drug affect onset and duration?

Answer 5

• Less patchy block (same with [])
• longer lasting
• more cranially it will spread

Question 6

What are the effects of using morphine, methadone and fentanyl for epidurals?

Answer 6

• Morphine (0.1 mg/kg)
  
  • Up to 24 hr of analgesia; greater w/ LA combos
• Methadone (0.1-0.3 mg/kg)
  
  • Over 8-12 hr of analgesia; greater w/ LA combos
• Fentanyl (5-10 mcg/kg)
  
  • Up to 3 hr?

SE: urinary retention (detrusor relaxation, PS blockade), urticaria (H2 release)

Question 7

What are 3 alpha 2’s that can be used as epidural agents and what are their effects?

Answer 7

Dexmed, clonidine, xylazine

• Good analgesia, some LA effect (xylazine), CV effects (bradycardia, 2nd degree AV block)

Question 8

Describe the use of ketamine as an epidural agent

Answer 8

• Short analgesia alone (30 min), but can prolong effects of LA (90 min w/ lidocaine)
• may be useful as an NMDA antagonist (chronic pain)

Dose: 3 mg/kg

Question 9

Why might you use a vasoconstrictor, such as epinephrine, as an epidural agent?

Answer 9

• May prolong duration of action of other drugs (can’t always tell)
• probably more effective in drugs that cause severe vasodilation and are of short duration (lidocaine)

Question 10

What are some common complications seen with epidurals?

Answer 10

• Spread
• Cardiac depression
• Vasodilation
• Resp arrest
• Bleeding
• Root or spinal cord damage
• Intravascuar injection
• Death