Anesthesia

Question 1

CSE vs epidural

Answer 1

CSE:
- Faster onsent of analgesia (compared to epdirual); more pruritis
- Epidural: more favorable in relation to umbilical venous pH
- Appears to be little basis for offering CSE over epidurals in labor with no difference in patient satisfaction
- Should be injecting L2-L3
- Meningitis almost exclusively occurs following perforation of the dura
- Epidurals should not puncture the dura – this is called a “wet tap” – patient will have headache; if have fever  meningitis

Question 2

Nerve injuries from delivery

Answer 2

Nerve Injuries from Delivery:
- Most common:
o Lateral femoral cutaneous
o Femoral
o Risk factors = prolonged 2nd stage, nullip, epidural
- Foot drop: common peroneal nerve; lumbosacral root or lumbosacral plexus

Question 3

Nerve injuries from delivery

Answer 3

Nerve Injuries from Delivery:
- Most common:
o Lateral femoral cutaneous
o Femoral
o Risk factors = prolonged 2nd stage, nullip, epidural
- Foot drop: common peroneal nerve; lumbosacral root or lumbosacral plexus

Question 4

Post-dural puncture headache

Answer 4

What is PDPHA? (Post dural puncture headache)
- Worsens within 15 minutes of upright position
- Improves within 30 minutes of supine position
- At least one of the following: neck stiffness, tinnitus, hypoacusis, photophobia, nausea
- Should NOT have fever
- Incidence: 1:144
- Treatment: Epidural blood patch

Question 5

LMWH and neuraxial

Answer 5

LMWH: weight: 5000 Daltons; binds to antithrombin III, but far less antithrombin activity; major effect is factor Xa inhibition
- ½ life = 6 hours; no influence on platelets and lipolysis
- Renal clearance
- Clotting times and activated partial thromboplastin time – unaffected
- Not 100% revered by protamine
- Removal of epidural should occur 10-12 hours after last dose

Question 6

General concerns for anesthesia

Answer 6

• General:
  o propofol/etomidate decrease cerebral blood volume
  o volatile agents increase cerebral blood volume
  o ketamine (inhaled agent) increases cerebral blood volume

Question 7

MS and neuraxial

Answer 7

• Epidural: injections increase ICP
  o MS – not contraindicated
• Spinal: don’t’ want to do dural puncture in case of increased ICP
  o Relative contraindication for MS

Question 8

Lidocaine toxicity

Answer 8

Question 9

Chemical structure of local anesthetics

Answer 9

• Weakly basic in nature; lipophilic aromatic ring
• Intermediate group:
  o Ester – metabolized in blood
  o Amide – metabolized in liver; higher risk of toxicity

Question 10

Chemical structure of local anesthetics

Answer 10

• Weakly basic in nature; lipophilic aromatic ring
• Intermediate group:
  o Ester – metabolized in blood
  o Amide – metabolized in liver; higher risk of toxicity

Question 11

Treatment of anesthesia toxicity (CNS and cardio)

Answer 11

Treatment of CNS Toxicity:
- Halt injection
- Hypoventilation with 100% oxygen
- Both metabolic and respiratory acidosis decrease the convulsive dose
- Benzodiazepine or propofol
Cardiovascular Toxicity:
- Negative inotropic effect that is dose-related and correlates with potency
- Interference with calcium signaling mechanism
- Rhythmic and conductivity – ventricular arrhythmias
- Treatment: local anesthetics are lipid soluble
o Lipid emulsions
 Supplement essential fatty acids to reverse toxicity
- If maternal circulation not restored in 4 minutes, CD should be performed

Question 12

Considerations for neuraxial anesthesia

Answer 12

• Associated with hypotension; due to sympathetic blockade
• No benefit to fluid preloading
• Affected by degree of blockade
• Managed with: ephedrine or phenylephrine
• Ephedrine crosses placenta greater extent

Question 13

Anesthesia and cardiac disease

Answer 13

Cardiovascular System:
- Etomidate: will NOT cause hypotension; minimal cardiovascular effects
- Propofol: decrease in SVR and MAP
- Ketamine: increase in MAP and HR: possible myocardial depression
- Any spinal epdirual will cause hypotension (etomidate has the least risk)

Heart Disease in Pregnancy
- 11% of parturients with CHD have complications
- Rheumatic heart disease (mitral stenosis)
- Most common complication/maternal death: arrhythmia
- General principles:
o Regurgitant lesions get better with neuroaxial anesthesia
 Should vasodilate and favor forward flow; tachycardia is ok
o Stenotic lesions do NOT do well with neuraxial anesthesia
 Small drop in BP means drop in perfusion
 If severe AS, should not do neuraxial block
- Effects of Anesthesia:
o Epidural – slow in onset
o Spinal – rapid onset; T1-T4 are the cardiac accelerator fibers
 Treatment of hypotension must also be considered
o General: induction agents chosen on basis of pathophysiology
 Need to consider stress of intubation and reversal of neuromuscular blockade

Question 14

Which of the following cardiac lesions improves with epidural analgesia?

Answer 14

o Aortic regurgitation

Question 15

A patient with aortic stenosis requires CD. Which of the following induction agents will we most likely use?

Answer 15

o Etomidate – No effect on SVR, or HR
o Propofol will cause hypotension, ketamine causes tachycardia, midazolam will decrease SVR

Question 16

According to ACOG, what is the minimal platelet count in which epidural can be placed?

Answer 16

80K