Vasopressors in obstetrics: what should we be using?
OBJECTIVE
Historically, ephedrine has been recommended as the best vasopressor in obstetrics because animal studies showed it caused less reduction in uterine blood flow compared with alpha-agonists. Recent clinical evidence, however, suggests that this is not as important as initially thought. This review evaluates current data with a focus on spinal anesthesia for cesarean section.


RESULTS
Ephedrine and phenylephrine have been most investigated. Advantages of ephedrine include familiarity, long history and low propensity for uteroplacental vasoconstriction. Ephedrine, however, has limited efficacy, is difficult to titrate, causes maternal tachycardia and depresses fetal pH and base excess. Advantages of phenylephrine include high efficacy, ease of titration and the ability to use liberal doses to maintain maternal blood pressure near normal and then prevent nausea and vomiting without causing fetal acidosis. Phenylephrine, however, may decrease maternal heart rate and cardiac output and few data are available on its use in high-risk cases. Combination of a phenylephrine infusion and rapid crystalloid cohydration is the first method described that reliably prevents hypotension.


CONCLUSIONS
When current evidence is considered, in the authors' opinion, phenylephrine is the vasopressor that most closely meets the criteria for the best vasopressor in obstetrics.
Ngan Kee
Warwick D
WD
Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Prince of Wales Hospital Shatin, Hong Kong, China. warwick@cuhk.edu.hk
Khaw
Kim S
KS
D001794:Blood Pressure / Q000187:drug effects; D004809:Ephedrine / Q000009:adverse effects / Q000627:therapeutic use; D005260:Female; D006801:Humans; D007022:Hypotension / Q000517:prevention & control*; D009774:Obstetrics; D010656:Phenylephrine / Q000009:adverse effects / Q000627:therapeutic use; D011247:Pregnancy; D011248:Pregnancy Complications / Q000517:prevention & control; D014662:Vasoconstrictor Agents / Q000009:adverse effects / Q000627:therapeutic use*
D014662:Vasoconstrictor Agents; D010656:Phenylephrine; D004809:Ephedrine