Original ArticleA prospective study of awareness and recall associated with general anaesthesia for caesarean section☆
Introduction
General anaesthesia for caesarean section (CS) is traditionally considered a high-risk procedure for awareness, although the potency of volatile anaesthetic agents is enhanced by pregnancy. Awareness with recall of intraoperative events is highly likely to cause patient dissatisfaction and can result in prolonged psychological disturbance with anxiety, mood and sleep disturbance and phobic behaviour.[1], [2], [3] It is a prominent cause of litigation.4 A higher risk of awareness in the obstetric population compared to the general surgical population may stem from a number of factors. These include physiological changes, particularly the high cardiac output of pregnancy, which accelerates the redistribution of intravenous anaesthetic agents and slows the establishment of an adequate partial pressure of volatile anaesthetic agent. Added to this is concern about neonatal drug exposure just before delivery, the effect of volatile anaesthetics on uterine tone and the haemodynamic effects of anaesthetic agents in emergency situations.
In recent years there have been several developments in anaesthesia, particularly in anaesthetic pharmacology and technology, which may have changed obstetric anaesthesia practice. The impact and clinical application of these changes on the incidence of awareness and recall in this population is unclear. Examples of developments that may have altered this incidence include the widespread availability of depth of anaesthesia monitors, volatile anaesthetic agents with a more rapid onset of action such as sevoflurane and desflurane, an acceptance of higher levels of volatile anaesthetic agents, a declining use of nitrous oxide and the use of propofol for induction of anaesthesia.
With the declining use of general anaesthesia for CS, little recent research has focused on it. We conducted a prospective observational study during 2005 and 2006 to assess the nature of contemporary practice in relation to general anaesthesia for CS. In this paper we present the information on the complication of awareness, as well as information on anaesthetic techniques and pharmacology relevant to this complication.
Section snippets
Methods
A multicentre prospective observational study of general anaesthesia for CS was conducted with the assistance of the Australian and New Zealand College of Anaesthetists (ANZCA) Trials Group across 13 hospitals in Australia and New Zealand between June 2005 and January 2007. The methods used to set up and conduct the trial are described elsewhere in this issue of the journal.5 Women were considered eligible if they were aged 18 years and over and underwent CS under general anaesthesia.
The case
Results
In total 13 hospitals contributed to the data set, with contributions from centres ranging from 16 to 219 patients.5 A total of 1095 cases were surveyed and of these, 763 had at least one postoperative interview for dreaming and recall. Of the 1095 cases surveyed, 47% were classified as emergency (category 1) and 18% were elective (category 4) (Table 1). A depth of anaesthesia monitor was applied in 32% of cases (30% of category 1, 27% of category 2/3 and 37% of elective cases). Procedure and
Discussion
In this study we found an incidence of awareness with recall of intraoperative events to be approximately 1 in 400 general anaesthetics, although it is possible that the incidence was closer to 1 in 150 and the upper confidence interval, assuming only two cases, is 1 in 100. This is consistent with the incidence reported in 1991 by Lyons and Macdonald (0.4%)7 and is higher than the incidence reported in the general surgical population (0.1-0.2%),8 confirming that pregnant women remain at
Acknowledgements
ANZCA Trials Group participants: P Popham, I Walkley, The Royal Melbourne Hospital (Melbourne); S Walker, P Gajdusek, Middlemore Hospital (Auckland); M Paech, K Scott, King Edward Memorial Hospital for Women (Perth); J Hill, National Women’s Hospital (Auckland); P Thomas, Wellington Hospital (Wellington); A Cyna, Women and Children’s Hospital (Adelaide); C Doyle, M Prentice Royal Prince Alfred Hospital (Sydney); M Nicholson, Rockhampton Hospital (Rockhampton); L Boyd, Nambour Hospital
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This study was supported by a starting grant from the Australian and New Zealand College (ANZCA) Trials Group, followed by a 2006 project grant from ANZCA.