Anesthesia Flashcards
CSE vs epidural
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
Nerve injuries from delivery
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
Nerve injuries from delivery
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
Post-dural puncture headache
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
LMWH and neuraxial
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
General concerns for anesthesia
- General:
o propofol/etomidate decrease cerebral blood volume
o volatile agents increase cerebral blood volume
o ketamine (inhaled agent) increases cerebral blood volume
MS and neuraxial
- 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
Lidocaine toxicity
Chemical structure of local anesthetics
- Weakly basic in nature; lipophilic aromatic ring
- Intermediate group:
o Ester – metabolized in blood
o Amide – metabolized in liver; higher risk of toxicity
Chemical structure of local anesthetics
- Weakly basic in nature; lipophilic aromatic ring
- Intermediate group:
o Ester – metabolized in blood
o Amide – metabolized in liver; higher risk of toxicity
Treatment of anesthesia toxicity (CNS and cardio)
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
Considerations for neuraxial anesthesia
- 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
Anesthesia and cardiac disease
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
Which of the following cardiac lesions improves with epidural analgesia?
o Aortic regurgitation
A patient with aortic stenosis requires CD. Which of the following induction agents will we most likely use?
o Etomidate – No effect on SVR, or HR
o Propofol will cause hypotension, ketamine causes tachycardia, midazolam will decrease SVR
