Phenylephrine Infusions for the Prevention of Spinal-induced Hypotension: Do We Need Any More Evidence?

( Anesth Analg . 2025;141:732-735. doi: 10.1213/ANE.0000000000007512.) Spinal anesthesia (SA) is the preferred technique for cesarean delivery (CD) because it offers rapid and reliable anesthesia, yet it carries a high risk of hypotension. Uncontrolled drops in maternal blood pressure can cause nausea, vomiting, fetal acidosis, or even cardiovascular collapse. Vasopressors are therefore essential to prevent or treat spinal-induced hypotension. Although ephedrine was historically favored due to early animal studies suggesting alpha-agonists might impair uteroplacental blood flow, later clinical research proved that pure alpha-agonists, especially phenylephrine, are both safe and more effective. Studies by Ngan Kee et al established that phenylephrine reduces fetal acidosis compared with ephedrine and that continuous prophylactic infusion prevents hypotension and related nausea and vomiting better than intermittent rescue boluses. Their work also showed that combining a crystalloid co-load with a phenylephrine infusion further minimizes hypotension and maintains maternal blood pressure at baseline, rather than allowing a 10 to 20 percent decline, significantly decreasing intraoperative nausea and vomiting, without harming neonatal acid-base balance.