Re-evaluation of the role of intramuscular ephedrine as prophylaxis against hypotension associated with spinal anesthesia for Caesarean section

[摘要] Spinal anaesthesia for Caesarean section is associated with an unacceptably highincidence of hypotension despite the administration of an intravenous fluid preload andthe use of uterine displacement. The theoretical benefits of preventing hypotension asopposed to treating it as it occurs are the avoidance of considerable maternaldiscomfort, a reduced risk of serious cardiovascular or respiratory depression and theavoidance of transient foetal asphyxia.The use of prophylactic intramuscular ephedrine prior to spinal anaesthesia has beenrecommended but not well studied. The advantages of the intramuscular route forephedrine administration are its simplicity and its favourable pharmacokinetic profile.Cardiovascular support is sustained throughout the surgery and into the post operativeperiod. Opposition to the use of intramuscular ephedrine in the prevention ofhypotension is based on two studies in which spinal anaesthesia was not used [1,2].These studies showed an unacceptably high incidence of hypertension, a deleteriouseffect on foetal gas exchange and a lack of efficacy when intramuscular ephedrine wasused in epidural and general anaesthesia respectively.This research report describes a randomised, double blind, interventional study designedto assess the safety (prevalence of hypertension, tachycardia or foetal compromise) andefficacy (prevalence of hypotension) of 37,5mg of ephedrine given prior to spinalanaesthesia for Caesarean section. Forty patients who had given informed consent wereentered into the study. Blood pressures and pulse rates were recorded for 90 minutesafter ephedrine administration, samples of umbilical venous blood were collected andApgar scores assessed.This study found that giving 37,5mg of intramuscular ephedrine prior to spinalanaesthesia was safe from a maternal point of view in that it was not associated withreactive hypertension or tachycardia. When the ephedrine was given 10 minutes prior toinduction of the spinal the technique proved to be effective in reducing the incidence andseverity of hypotension. When used in the above manner the technique was notassociated with foetal depression or acidosis.

[发布机构] University of the Witwatersrand