SummaryWe have investigated the effect of oxygen flow rate on pre-oxygenation in pregnant patients at term using a circle system. Twenty patients presenting for elective Caesarean section maintained tidal volume breathing through a standard circle system for 3 min. Subjects were pre-oxygenated using oxygen flow rates of 5 l. Effective pre-oxygenation is a requirement for safe practice of general anaesthesia in pregnancy [1,2]. Increased maternal oxygen consumption combined with decreased functional residual capacity result in the potential for hypoxaemia to develop during apnoea following induction of anaesthesia [3,4]. This may be further compounded by pregnancy associated airway changes, which can contribute to delay in securing a definitive airway [3]. Ensuring that pre-oxygenation is performed to a high standard minimises the risk of hypoxaemia developing and prolongs the safe duration of apnoea following induction of anaesthesia. The aim of this study was to establish how the circle breathing system and tidal volume breathing technique could be employed to provide optimal pre-oxygenation in term pregnant patients. It is our clinical experience that the circle system has become commonplace in obstetric theatres in the United Kingdom. Previous studies investigating the use of the circle system in parturients have used fixed oxygen flow rates for tidal volume breathing pre-oxygenation [2,5]. We proposed that higher fresh gas oxygen flow rates would increase the efficiency of denitrogenation within the circle system, thereby optimising pre-oxygenation. Our study design incorporated a commonly employed breathing system and routine preoxygenation technique with the intention that the results would be applicable to everyday clinical situations encountered by anaesthetists in obstetric theatres. MethodsFollowing approval by the North Sheffield Research Ethics Committee, 20 women presenting for elective Caesarean section under regional anaesthesia gave informed, written consent to participate in the study. Subject had completed 36 weeks of gestation. Exclusion criteria included pregnancy related complications, suspected fetal compromise and pulmonary disease.The age, antenatal booking weight, height and gestation of the subjects were recorded. Pre-oxygenation was performed in a supine position with left uterine displacement by means of a 15°firm, rubber wedge placed under the right hip. Subjects maintained tidal volume breathing through a facemask for 3 min. For our study, we used the circle system integral to the Aestiva ⁄ 5 anaesthetic machine (Datex-Ohmeda, Stirling, UK) with a 2 l

SummaryWe have investigated the suitability of the HemoCue Ò photometer to measure the concentration of haemoglobin in suction fluid obtained at elective caesarean section in 30 women. Laboratory analysis was used as a gold standard against which values generated by the HemoCue were compared. We used the method of Bland and Altman to analyse the data. The bias and the limits of agreement were )0.013 and )0.39 to 0.36 mg.dl )1 respectively, indicating a good level of agreement. Mean (SD) total blood loss calculated using these data, combined with the weight of the swabs, was consistently greater than clinical estimation: 768 (496) ml versus 506 (249) ml respectively (p < 0.001). We have found that the HemoCue near patient testing device may be used to estimate blood loss accurately in the suction fluid obtained at elective Caesarean section.

A dequate preoxygenation must be performed to a high standard to minimize the risk of hypoxemia and to prolong the safe duration of apnea after general anesthesia is induced in pregnant patients. This study examined how the circle breathing system and tidal volume breathing technique could be used to provide optimal preoxygenation in term pregnant women. This study looked at the efficacy of different fresh gas flow rates to increase the efficiency of denitrogenation within the circle system and to optimize maternal preoxygenation.Twenty women at the authors' institution who were at 36-week gestation or greater and presented for elective cesarean section under regional anesthesia were included. Prior to each period of preoxygenation, oxygen was allowed to flow through the circle system until an FiO 2 of 1.0 was achieved. Patients were preoxygenated 3 consecutive times using flow rates of 5 L/min, 10 L/min, and 15 L/min in random order. Baseline fractional end-tidal oxygen (F E O 2 ) and fractional end-tidal carbon dioxide (F E CO 2 ) were obtained before preoxygenation and then were recorded every 10 seconds during preoxygenation using a gas analyzer. The tidal capnography trace was observed by the investigator during the study to monitor adequacy of mask seal. Between each preoxygenation session, baseline values were recorded with the patient in an upright position breathing room air for 5 minutes at the end of which F E O 2 and F E CO 2 were recorded.The patients had a mean age of 30.3 ± 5.2 years and gestational age of 38.9 ± 1.0 week. The mean fractional endtidal oxygen values at the 5, 10, and 15-L/min flow rates were 0.86, 0.92, and 0.90, respectively. Compared with the flow rate at 5 L/min, the values at flow rates of 10 and 15 L/min values were significantly higher (P<0.001 respectively), although preoxygenation was not improved by increasing the flow from 10 to 15 L/min. Entrainment of air occurred on 4 occasions each at flow rates of 5 and 10 L/min and 5 occasions at 15 L/min. In 4 of these instances, a minimal change in fractional end-tidal carbon dioxide occurred.Oxygen flow rates Z10 L/min within the circle breathing system can provide optimal preoxygenation to parturients who maintain tidal volume breathing for 3 minutes. Entrainment of air occurred in a surprisingly high percentage of cases.

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