Anesthesia for cesarean section. Tom Archer, MD, MBA UCSD Anesthesia. A unique psychosocial surgery. Outline. C-section – a unique psychosocial surgery How the OB anesthetist should behave. Evolution of techniques Neuraxial block physiology and management GA physiology and management.
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Tom Archer, MD, MBA
LV dilation / hypertrophy
Aortic stenosis at rest
Cardiac output not sufficient to cause critically high LV intracavitary pressure / LV failure.
LV failure / ischemia
Aortic stenosis with SAB: increased cardiac output / arteriolar vasodilation:
Decreased SVR Fall in systemic BP and / or increase in LV intracavitary pressure ischemia or LV failure.
Resistance arterioles– decreased SVR
Decreased SVR desaturation
Increased pulmonary vascular resistance desaturation
Decompensated patient with ASD, VSD or PDA-- Decreased SVR or increased pulmonary vascular resistance increased RL shunt and increased arterial desaturation.
Minimal RL shunt
Low pulmonary vascular resistance
Normal, compensated patient with ASD, VSD or PDA-- high SVR and low pulmonary vascular resistance minimal RL shunt.
Virtually all patients immediately develop warm, dry hands and leave the hospital the same day as surgery.
Normal placental function: fetal and maternal circulations separated by thin membrane (syncytiotrophoblast).
Umbilical vein (UV)
“Lakes” of maternal blood
Fetal capillaries in chorionic villi
Precariously oxygenated environment
Archer TL 2006 unpublished
Aorto-caval compression decreases P1 (“aorto”) and increases P2 (“caval”)
Therefore, aorto-caval compression decreases O2 delivery to fetus.
R = placental resistance (fixed in short term)
P1 = uterine artery pressure
Placenta blood flow (O2 delivery) =
(P1 – P2) / R
P2 = uterine vein pressure
Archer TL 2006
Abdominal compression and hyperventilation
Decrease local anesthetic dose by 30%, compared to non-pregnant dose.
You can be fooled into thinking you have not reached the epidural space, when you have!
Naji M, Anaesthesia, 2009, 64, pages 39–42
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