Preventing and Treating Hypotension During Spinal Anaesthesia for Caesarean Section
Highlights
- Preloading with i.v. crystalloid fluids before spinal anaesthesia has been found to be largely ineffective in reducing hypotension (View Highlight)
- There is good evidence that ephedrine, which is predominantly a β-adrenergic agonist, causes fetal acidosis when used to prevent or treat hypotension. It crosses the placenta and has direct sympathomimetic effects in the fetus.6 This leads to a degree of acidaemia, although the incidence of defined fetal acidosis (umbilical artery pH<7.2) is not changed (View Highlight)
- Alpha-adrenergic agonists are therefore preferred. These have a variable amount of accompanying β-activity. Phenylephrine, a pure α-agonist, is the standard choice because of the amount of supporting data available, including studies to assess optimal dosage regimens (View Highlight)
- Phenylephrine has the same advantages over ephedrine in women with pre-eclampsia. The dose requirement is lower, and therefore the starting infusion rate should be reduced. The aim should be to avoid a rapid decrease in arterial pressure that may reduce uteroplacental blood flow to an already-compromised fetus. (View Highlight)