Norepinephrine for Hypotension in Cesarean Section

Overview

Hypotension is a very common consequence of the sympathetic vasomotor block caused by spinal anesthesia for cesarean section. Maternal symptoms such as nausea, vomiting and dyspnea frequently accompany severe hypotension, and adverse effects on the fetus, including depressed APGAR scores and umbilical acidosis, have been correlated with severity and duration of hypotension. Because hypotension is frequent, vasopressors should be used routinely and preferably prophylactically.

Phenylephrine has a potent direct α effect, with virtually no β effects at clinical doses, however when given at higher than required doses, it may induce baroreceptor-mediated bradycardia with a consequent reduction in maternal cardiac output. Although α agonist drugs are the most appropriate agents to treat or prevent hypotension following spinal anaesthesia, those with a small amount of β agonist activity may have the best profile (noradrenaline (norepinephrine) and metaraminol. Phenylephrine is currently recommended due to the amount of supporting data.Noradrenaline is the primary catecholamine released by postganglionic adrenergic nerves. It is a potent α adrenergic agonist, with comparatively modest β agonist activity.

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