Vasopressor use during neuraxial anaesthesia/analgesia is more prevalent today than ever before. It is my impression that phenylephrine has emerged as the defacto pressor of choice over the past decade. However, in 2001 95% of consultant anaesthetists used ephedrine exclusively (Burns Anaesthesia 2001). What has changed over that decade? A series of studies that have suggested that phenylephrine has certain haemodynamic advantages over ephedrine. In particular the appearance of increased acidosis in babies of mothers that have received ephedrine (this may not be clinically significant) has tilted therapy towards phenylephrine. This month’s Anesthesia and Analgesia features a timely systematic review of vasopressor therapy during spinal anaesthesia (SA) for Caesarian Section (CS). I would recommend that every anaesthetist that is involved with obstetrics read and digest Dr Habib’s review. To whet your appetite, here is a summary of the conclusions.
- Phenylephrine is as effective as ephedrine for treating hypotension associated with SA.
- Phenylephrine is superior to ephedrine for prevention of intraoperative nausea and vomiting (IONV).
- Phenylephrine infusion is superior to phenylephrine boluses for IONV.
- Phenylephrine is superior to ephedrine in terms of fetal acid base status – higher umbilical artery pH and lower base deficit.
- Phenylephrine may reduce cardiac output, but it is unclear if there is any clinical significance to this.
- As one would expect, due to each patient having different blood pressures, different pharmacodynamics and different fluid status – there is no optimal dose of phenylephrine in this setting.