OB Anesthesia

Question 1

When would you use general for OB?

Answer 1

need fast induction, ie maternal hemorrhage or fetal compromise; does increase maternal mortality 16.7x greater

Question 2

Recognize the impact of patient race and ethnicity in the use of epidural analgesia for labor.

Answer 2

back and hispanic patient s are under treated for pain in comparison to white and insured patients (most likely to get epdurals)

Question 3

1. Discuss the physiologic changes of pregnancy as they influence anesthetic care. (CV/Pulm)

Answer 3

increased intravascular volume (dilutional anemia)
decreased SVR due to greater venous capacitance, although CVP can be increased due to IVC compression
increased CO with largest CO increase immediately after delivery of placenta (redistribution of blood)

aortocaval compression syndrome (supine hypotension), usually after 20 weeks; tx with ephedrine or phenyleprine or left decubitus and adequate fluids

pulm: vascualr engorgement and mucosal edema, resting PaCOw decreses due to increased minute ventilation (high tidal volume and progesterone); reduction in FRC (20%) which increases atelectasis

Question 4

Why do pregnant patients become hypoxic quickly?

Answer 4

decreased FRC and increased O2 uptake (higher metabolic rate from fetus)

Question 5

1. Discuss the physiologic changes of pregnancy as they influence anesthetic care. (neuro/GI)

Answer 5

neuro: progesterone has a sedative effect, ***decreased MAC and need for less volatile anesthetic
* ** spinal and epidurals need less anesthesia because increased intra-abdominal pressure resulting in engorgement of epidural veins and decrease in the size of epidural space (decreased CSF volume)

GI: pregnant patients have decreased gastric emptying, greater risk of aspiration; placenta produces gastrin, dropping pH of stomach (metoclopramide)

Question 6

2. Name the factors that influence the placental transfer of drugs from the maternal circulation to the fetal circulation.

Answer 6

**maternal/ fetal concentration gradients, maternal protein binding, molecular wt of drug, lipid solubility and degree of ionization

fetal uptake is facilitated by low fetal pH, basic drugs crossing as unionized forms will become ionized and trap in the fetal environment

Question 7

Diagram the pain pathways and dermatomes that impact labor and delivery.

Answer 7

1st stage (cervical dilation) visceral pain 2/2 uterine contraction and dilation of cervix– T10-L1

2nd stage (pushing) somatic pain due to vaginal and perineal distention – S2-4

Question 8

Describe the available options for labor analgesia.

Answer 8

stage 1: breathing/relaxation

stage 2: opioids, spinal, epidural, acupuncture, hypnosis; sedatives, tranquilizers, dissociative analgesia, inhalation analgesia, paracervical block, lumbar sympathetic block, pudendal block

Question 9

Compare and contrast the risks and benefits of regional anesthesia and general for labor and delivery.

Answer 9

regional: epidurals can be staged as baby descends; epidural catheter makes transition to c-section easier

epidural has slow onset compared to spinal so body can adjust to BP changes; very little medicine to baby

risks: infxn at insertion, spinal headache, injuring nerves*** space occupying lesions (hematoma); most commonly hypotension

general has a 16.7 times the maternal death rate but is fastest and best if fetal compromise or maternal hemorrhage

Question 10

Where does epidural go?

Answer 10

L3-4 space