Foetal oxygenation during caesarean section

Abstract

Oxygenation of the foetus is probably the most important single environmental factor which has a bearing upon the eventual well-being of the infant. Throughout pregnancy imperfect oxygenation is inimical to continued viability. At delivery, inadequate oxygenation can jeopardize the baby's immediate survival. Hypoxia, not severe enough to cause immediate or neonatal death can result in permanent neurological damage.At caesarean section it is possible to control the conditions of oxygen administration to the mother accurately and at the same time to observe the effect of this upon the maternal and foetal blood. This study was designed to investigate the effects of various inspired maternal oxygen concentrations on babies delivered by elective caesarean section, inspired oxygen concentration being the only variable. MIITHODThirty-four women at term (38 to 42 weeks gestation) were studied. They were undergoing caesarean section under general anaesthesia for either cephalo-pelvic disproportion or previous caesarean section. All the mothers were healthy by clinical, radiological and biochemical assessment as regards cardiovascular, respiratory and urinary systems and the course of their pregnancies was uncomplicated. During the hours preceding operation each was given about one litre (700 to 1350ml) of 10% invert sugar in Ringer Lactate to minimise the effect of overnight starvation on metabolism.Immediately prior to induction of anaesthesia, arterial blood was taken anaerobically into a heparinized glass syringe by discrete puncture of the radial artery. Intravenous atropine 0.65mg was given just before induction with an appropriate hypnotic dose of thiopentone. Following suxamethonium 50mg the trachea was sprayed with 4 % lignocaine and then intubated with a 9.0mm cuffed Magill endotracheal tube. The cuff was optimally inflated to prevent gas leaks. Intermittent positive pressure ventilation was imposed using the non-return circuit of an Engstrom ventilator. A M .

Time: An Important Variable at Caesarean Section

“…Biochemical distress in the neonate was reflected in the Apgar score (Tables JX and X) and not surprisingly, the clinical state was more closely associated with umbilical artery values as this blood is similar to fetal arterial blood. We could not confirm the results of Rorke et al (1968) that Po, was the only significant correlate of the clinical state. In the present study pH, Pcoa and Po, of umbilical artery and pH of umbilical vein all correlated with Apgar score.…”

“…Biochemical analysis of cord or fetal scalp blood has been performed in a number of recent studies in which nitrous oxide-oxygen mixtures have been employed for general anaesthesia (Stenger, Blechner and Prystowsky, 1969;Stenger et al, 1967;Cosmi and Marx, 1968;Rorke, Davey and Du Toit, 1968;Teramo, 1968 ;Coleman, 1967). Stenger and his colleagues found no biochemical changes to account for an increased incidence of low Apgar scores when anaesthesia was prolonged.…”

Randomized, double-blind comparison of different inspired oxygen fractions during general anaesthesia for Caesarean section †

“…Confounding factors that make interpretation of earlier studies difficult include lack of lateral uterine displacernent.P" inclusion of both labouring and nonlabouring patients.f' incomplete or undescribed methods of randornizationP'" and inadequate compensation for changes in anaesthetic depth when varying Flo,? [6][7][8] Furthermore, previous studies used umbilical arterial and venous P0 2 to calculate fetal haemoglobin oxygen saturation, taking into account the characteristics of the fetal oxyhaemoglobin concentration curve.' No previous study has directly measured the effect of maternal Flo, on umbilical cord blood oxygen content.…”

The effects of maternal hypercapnia on foetal oxygenation and uterine blood flow in the pig.

“…In the human, Rorke, Davey & Du Toit (1968) showed that at Caesarean section, the foetal umbilical arterial oxygen tension was lower when the mother was ventilated with 100 % oxygen, than when ventilated with 66-6 % oxygen. Baraka (1970) found that the foetal oxygen tension correlated well with the maternal when the Pco2 was in the range 78-200mmHg, but not when it was in the range 200-500 mmHg.…”