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SummaryTwo comparable series of 21 patients who had elective Caesarean section had general anaesthesia induced by thiopentone sodium 4.53 (SD 0.65) mglkg or propofol2.15 (SD 0.26) mglkg. Maintenance was similar for both groups. Blood pressure was lower in the propofol group during the induction-delivery interval. Umbilicallmaternal vein ratios for thiopentone and propofol were 8.5 and 7.2 respectively. Infant wellbeing as judged by Apgar score and cord blood analysis showed little difference between the two induction agents. Factors associated with uterine relaxation and bleeding were similar in the two groups. Key wordsAnaesthesia; obstetric. Anaesthetics intravenous; thiopentone sodium, propofol.Thiopentone sodium has been used in obstetric anaesthesia since 1936l and is regarded as the standard induction agent. Early investigators used larger doses and Hellman et aL2 showed that considerable quantities were transferred to the infant. It was later demonstrated3 that placental transfer occurred within seconds and that repeated injection caused significant infant depres~ion.~ Present-day opinion is that a single dose of 3-5 mg/kg5s6 should be given to induce sleep and that maintenance of anaesthesia before delivery should be by inhalation agents.Propofol, diisopropyl phenol, has properties which suggest that it might be a useful alternative to thiopentone. The suspension has a pH of 7.0 which makes it less likely to cause local tissue or vascular complications. The cardiovascular response to tracheal intubation is less than with thiopentone.' Propofol is more rapidly metabolised and excreted than the barbiturate, and hangover after anaesthetic is reduced.8This investigation reports a comparison of propofol and thiopentone used as induction agents for general anaesthesia for patients who have elective Caesarean section. It had the approval of the Local Medical Research Ethics Committee and verbal consent from all patients. Materials and methodsWomen selected were healthy and had a pregnancy of at least 36 weeks' gestation with a single uncompromised fetus. Elective Caesarean section was for disproportion or abnormal fetal presentation. Oral ranitidine 150 mg was given 90 to 120 minutes before anaesthesia and left lateral tilt, instituted 15 minutes before induction, was maintained until delivery. Two intravenous cannulae were introduced, one in the right arm for the infusion of a compound sodium lactate solution and the other in the left arm for blood sampling. The ECG, blood pressure automatically by Dinamap recorder, and tissue oxygen saturation by pulse oximeter, were monitored before and during anaesthesia. Ventilation of the lungs during anaesthesia was adjusted to maintain an end-tidal carbon dioxide of 4 to 4.25 kPa using a Datex Normocap. All patients were preoxygenated with 100% oxygen for 5 minutes before induction, and cricoid pressure was applied from the start of injection of the induction agent until tracheal anaesthesia was established.Women were randomly allocated to receive either 2.5% thiopenton...

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