Canadian journal of anaesthesia = Journal canadien d'anesthésie
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Randomized Controlled Trial Comparative Study Clinical Trial
Supplemental maternal oxygen therapy during caesarean section under epidural anaesthesia: a comparison of nasal prongs and facemask.
Forty healthy parturients at term, undergoing elective Caesarean section, were divided into two groups to receive supplemental oxygen by either simple facemask (Group FM, 8 L.min-1) or nasal prongs (Group NP, 4 L.min-1) during the procedure. Anaesthesia was provided by epidural block to equivalent dermatomal levels in all patients. Maternal oxygen saturation was measured continuously with pulse oximetry and supplemental oxygen was provided to the mother after administration of the epidural test dose and continued until the end of the procedure. ⋯ There was no difference in the clinical condition of the neonates, as assessed by Apgar scores, or in the acid-base and oxygenation status, as assessed by blood gas analyses between the two groups. Mean umbilical vein oxygen saturation, a measure of fetal oxygen delivery, was 46 +/- 18% (95% confidence interval 39% to 54%) for Group NP and 54 +/- 17% (95% confidence interval 46% to 62%) for Group FM, again not different. We conclude that when the clinical condition, acid-base and oxygenation status of neonates, delivered by elective Caesarean section to healthy, low-risk parturients with normal placental function under epidural anaesthesia, are evaluated, it makes no difference whether the mothers received supplemental oxygen by nasal prongs or simple facemask.
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The alkalinization of certain local anaesthetics with sodium bicarbonate hastens the onset of epidural analgesia. Increases in both the pH and PCO2 of the local anaesthetic are necessary to hasten onset. However, carbon dioxide can diffuse from local anaesthetic solutions following alkalinization with sodium bicarbonate and change both the pH and PCO2 of the mixture. ⋯ The pH and PCO2 of each solution were measured at time 0 and at 5, 10, 15, 20, 30, 40, 50 and 60 min intervals. The solutions were placed in containers as follows: 30 ml in 40 ml containers, 10 ml in 40 ml containers, 10 ml in 13 ml containers, and 10 ml in polypropylene syringes. The pH and PCO2 increased following alkalinization but gradually decreased in all containers except in polypropylene syringes.