Managing hypotension during anaesthesia for caesarean section

Hypotension is the most important common complication of regional anaesthesia for caesarean section. Methods of managing hypotension include lateral uterine displacement, mechanical leg compression, intravenous prehydration, and use of vasopressors. Uterine displacement is accepted as standard, although the optimal degree of tilt is unknown, and most anaesthetists overestimate the amount of tilt they believe they are applying. Leg compression is effective but not popular. In contrast to early reports, recent studies have not shown intravenous crystalloid prehydration to be very effective. Colloids are more effective but are expensive and have potential adverse effects. Rapid infusion of intravenous crystalloid after induction (cohydration) appears more effective than prehydration. Although historical studies supported use of ephedrine because of its low propensity to reduce uteroplacental blood flow, recent studies support use of α-agonists such as phenylephrine. Phenylephrine is more effective and can be titrated more easily than ephedrine, and it has a less depressive effect on fetal pH and base excess. It may be given as boluses (50-100 μg) or by infusion (50-100 μg/min). A phenylephrine infusion combined with cohydration is effective for preventing hypotension in most patients. Current evidence suggests that infusions are best titrated to maintain maternal blood pressure near to baseline values.