Korean J Anesthesiol.  1981 Jun;14(2):134-142.

Arterial Oxygen Tension Druing 1 Minute of Apnea in Parturient Women

• Yoon SY
• Lim OS
• Yoon DM
• Park KW

Abstract

Recent studies(Rorke et al., 1968: Moir 1970: Baraka, 1970: Fox and Houle, 1971) have demonstrated that the maternal arterial oxygen tension during Cesarean section is an important determinant of fetal oxygenation and consequently of the clinical condition of the infant at birth for oxygen is transferred by simple diffusion across the placenta to the fetus. Fetal blood oxygen tension is affected by the arteiral oxygen tension and concentration of the mother, and also is affected by uterine blood flow(Fox and Houle, 1971). The enlarged uterus pushes the diaphragm upwards. This results in a change in position of the heart which is lifted upwards, shifted to the left and anteriorly, and a change in the thoracic cage, and heart rate is increased about 10~12 beats above normal. There is a significant increase in cardiac output which reaches a peak 30~50% above normal until term, and in respiratory rate, so that it follows that oxygen consumption increases but its direct cause is the metabolic need of the uterus, placenta and fetus(Atkinson et al., 1977). As well as increased oxygen consumption in parturients hypoxia may occur in situations of difficult intubation, laryngoscopy for intubation, extubation and during endotracheal suctioning. Because of the markedly decreased oxygen tension, these procedures are more dangerous than for non-parturients. Therefore sufficient oxygenation is recommanded(Archer and Marx, 1974). We selected at random 78 adult female patients who had received Cesarean section and other surgical procedures under general anesthesia with intubation at Severance Hospital from September to November, 1980. They were divided into 3 groups. Group 1 was ventilated with 100% oxygen for 5 minutes followed by 1 minute of apnea. Group 2 was ventilated with 50% oxygen for 5 minutes followed by 1 minute of apnea. Group 3 was ventilated with 50% oxygen for 5 minutes followed by 1 minute of apnea with endotracheal suction. We analysed the decrease in oxygen tension between parturients and onoparturients. The results were as follows: 1) During apnes, the decreases in arterial blood oxygen tension were significantly greater (p<0.05) in parturients than in non-parturients in the 100% oxygen group. 2) During apnea, the decreases in arterial blood oxygen tension were significantly greater(p<0.05) in parturients than in non-parturients in the 50% oxygen group. 3) During apnea, the decreases in oxygen tension were significantly greater(p<0.05) in paturients than in non-paturients in the 50% oxygen and endotracheal suction group. These results indicate the importance of preoxygenation prior to endotracheal intubation and endotracheal suction and also of prompt reoxygenation following endotracheal intubation, extubation and endotracheal suction.

MeSH Terms

Adult
Anesthesia, General
Anoxia
Apnea*
Cardiac Output
Cesarean Section
Diaphragm
Diffusion
Female
Fetal Blood
Fetus
Heart
Heart Rate
Humans
Infant
Intubation
Intubation, Intratracheal
Laryngoscopy
Mothers
Oxygen Consumption
Oxygen*
Parturition
Placenta
Pregnancy
Respiratory Rate
Suction
Uterus
Oxygen