A comparison of speed of action of phenylephrine and ephedrine

INTERVENTION: Phenylephrine vs ephedrine A standardised anaesthetic technique will be used. Maternal arterial pressure will be measured by an automated oscillometric device (Cardiocap II, Datex Instrumentarium) and by a continuous, non‐invasive photoplethysmographic device using a finger probe (Finapres 2300, Ohmeda). Boluses of phenylephrine 100 ug or ephedrine 6 mg will be given whenever systolic arterial pressure falls by 15% from the prespinal value. An analog arterial pressure waveform will be recorded using a PowerLab 8sp recording and analysis device (AD Instruments Inc). This time from administration of vasopressor to time of peak effect on arterial pressure will then be analysed. CONDITION: Pregnancy and Childbirth: Anaesthesia ; Pregnancy and Childbirth ; Anaesthesia PRIMARY OUTCOME: Ttime to peak vasopressor effect on systolic arterial pressure SECONDARY OUTCOME: Not provided at time of registration INCLUSION CRITERIA: Healthy women having elective caesarean section at term will be recruited.