Labor Analgesia and Pharmacology

Question 1

What is the pain source for 1st stage labor pain?

Answer 1

Mainly lower uterine segment from contractions

Question 2

What is the pain source for 2nd stage labor pain?

Answer 2

Perineal structures via pudendal nerve

Question 3

What dermatomes are involved in 1st stage labor pain?

2nd stage?

Answer 3

1st stage= T10-L1

2nd stage= S2-S4

Question 4

T/F: Hypnosis works in 100% of the population?

Answer 4

False; 15% are easy to hypnotize, 15% are impossible

Question 5

What is the name of the education and behavioral techniques such as breathing and eye focus exercises?

Answer 5

Lamaze (psychoprophylaxis).

Question 6

What is the biggest reason why morphine is not used in parturients?

Answer 6

Immature blood brain barrier increases risk of resp depression in the neonate.

Question 7

What are the 3 issues with using meperidine (Demerol) in the parturient?

Answer 7

1. Causes frequent N/V
2. Contraindicated in pt with seizures or renal failure.
3. Long half life and active metabolites.

Question 8

Describe the neonatal resp depression associated with meperidine administration?

Answer 8

Unlikely if given less than 1 hour prior to delivery.

Question 9

What is a secondary use of Nalbuphine (Nubain) besides pain control?

Answer 9

Opioid induced pruritus.

Question 10

Which two medications have a ceiling effect on respiratory depression?

Answer 10

Nalbuphine and Butorphanol.

Question 11

Why are volatile anesthetics not used often in parturients?

Answer 11

1. Risk of pulmonary aspiration.

2. Decreased uterine tone

Question 12

What is the mechanism of action for nalbuphine?

Answer 12

Mu Opioid antagonist, Kappa Agonist.

Question 13

Which nerve block is typically used in 1st stage of labor?

Answer 13

Paracervical block

Question 14

Describe the technique of a paracervical block?

Answer 14

5cc of LA injected submucosally at 3 and 9 o’clock position beside cervix

Question 15

What are three risks with paracervical block?

Answer 15

1. Accidental injection into uterine artery
2. Fetal LA toxicity
3. Nerve injury/hematoma

Question 16

Which nerve block is typically used for 2nd stage of labor?

Answer 16

Pudendal block.

Question 17

Why would a pudendal block be performed?

Answer 17

For certain patients with contraindication for neuraxial blockade.

Question 18

Describe the technique of a pudendal block?

Answer 18

Needle is placed bilaterally via transvaginal approach under the ischial spines.

Question 19

What are the 3 risks of pudendal blocks?

Answer 19

1. Fetal injury
2. Infection
3. Hematoma

Question 20

Which LA is associated with PABA as an allergen?

Answer 20

Esters

Question 21

Which LA are metabolized by the liver?

Answer 21

Amides

Question 22

T/F: All LA are strong bases?

Answer 22

False; weak bases

Question 23

What is the pKa?

Answer 23

The pH where 50% of LA is polar and 50% is uncharged.

Question 24

T/F: The closer the pKa is from physiological pH, the slower the onset?

Answer 24

False; faster the onset.

Question 25

How would you artificially raise the pH to be closer to pKa?

Answer 25

Add Bicarbonate.

Question 26

Lipid solubility or protein binding: Which affects duration? Which affects potency?

Answer 26

Potency=Lipid solubility | Duration=Protein binding

Question 27

How would you adjust your dose for a parturient?

Answer 27

Smaller dose of LA, and will have a faster onset of blockade

Question 28

Which three LA are commonly used for labor epidurals?

Answer 28

1. Bupivacaine 2. Ropivacaine 3. Lidocaine

Question 29

Which 2 LA are commonly used for operative epidurals?

Answer 29

1. Lidocaine | 2. 2-Chloroprocaine

Question 30

Which 2 LA are commonly used for spinal anesthesia?

Answer 30

1. Tetracaine | 2. Bupivacaine

Question 31

Which patient can you not use 2 Chloroprocaine and why?

Answer 31

Patients with atypical pseudocholinesterases because is is metabolized by pseudocholinesterases.

Question 32

Which has more motor block 2 Chloroprocaine or Bupivacaine?

Answer 32

2- Chloroprocaine.

Question 33

What is the dose of bupivacaine for labor epidurals?

Answer 33

15-20mg, infusion of 8-12mg/hr

Question 34

Why are there bupivacaine analogs?

Answer 34

Levobupivacaine and Ropivacaine are both less cardiotoxic.

Question 35

What dermatomes are we ultimately trying to cover with neuraxial blocks?

Answer 35

T10- S4

Question 36

At what level should spinals be performed?

Answer 36

Below L3

Question 37

What is the transverse line passing across the lumbar spine between the posterior iliac crests?

Answer 37

Tuffier's Line

Question 38

What are 7 contraindications to neuraxial blockade?

Answer 38

1. Patient refusal 2. Infection at site 3. Coagulopathy 4. Intracranial mass lesion 5. Aortic stenosis 6. Existing spinal or neurological pathology 7. Hemodynamic instability.

Question 39

What is the average depth of epidural space?

Answer 39

4.75cm

Question 40

What are 7 things associated with Central Nervous System LA toxicity?

Answer 40

1. Tinnitus 2. Light-headedness 3. Metallic taste 4. Circumoral numbness 5. Convulsions 6. Loss of consciousness 7. Respiratory arrest.

Question 41

How is the CV system affected with LA Toxicity?

Answer 41

1. Inhibits Na+ channels 2. Decrease depolarization rate in Purkinje and ventricular muscle 3. Decrease duration of action potential 4. Decrease effective refractory period.

Question 42

What is dose of Intralipid for LA toxicity?

Answer 42

1.5ml/kg followed by 0.25ml/kg/min for 1 hr