A research report submitted to the Faculty of Medicine, University of
Witwatersrand, Johannesburg, in partial fulfillment of the
requirements for the degree of Master of Medicine in the branch of
Anaesthesia.Spinal anaesthesia for Caesarean section is associated with an unacceptably high
incidence of hypotension despite the administration of an intravenous fluid preload and
the use of uterine displacement. The theoretical benefits of preventing hypotension as
opposed to treating it as it occurs are the avoidance of considerable maternal
discomfort, a reduced risk of serious cardiovascular or respiratory depression and the
avoidance of transient foetal asphyxia.
The use of prophylactic intramuscular ephedrine prior to spinal anaesthesia has been
recommended but not well studied. The advantages of the intramuscular route for
ephedrine administration are its simplicity and its favourable pharmacokinetic profile.
Cardiovascular support is sustained throughout the surgery and into the post operative
period. Opposition to the use of intramuscular ephedrine in the prevention of
hypotension is based on two studies in which spinal anaesthesia was not used [1,2].
These studies showed an unacceptably high incidence of hypertension, a deleterious
effect on foetal gas exchange and a lack of efficacy when intramuscular ephedrine was
used in epidural and general anaesthesia respectively.
This research report describes a randomised, double blind, interventional study designed
to assess the safety (prevalence of hypertension, tachycardia or foetal compromise) and
efficacy (prevalence of hypotension) of 37,5mg of ephedrine given prior to spinal
anaesthesia for Caesarean section. Forty patients who had given informed consent were
entered into the study. Blood pressures and pulse rates were recorded for 90 minutes
after ephedrine administration, samples of umbilical venous blood were collected and
Apgar scores assessed.
This study found that giving 37,5mg of intramuscular ephedrine prior to spinal
anaesthesia was safe from a maternal point of view in that it was not associated with
reactive hypertension or tachycardia. When the ephedrine was given 10 minutes prior to
induction of the spinal the technique proved to be effective in reducing the incidence and
severity of hypotension. When used in the above manner the technique was not
associated with foetal depression or acidosis.WHSLYP201
