Awareness under anaesthesia is a synonym for inadequate anaesthesia

The incidence of awareness with recall under general anaesthesia has previously been reported to range from 0.2 to 0.4%1,2. Patient movement is an indicator of inadequate anaesthesia but this sign is abolished by the use of muscle relaxants unless the isolated forearm technique is used3,4. However, the use of short acting anaesthetic agents at light planes of anaesthesia to promote speedy recovery, higher patient turnover and earlier same-day discharge increases the risk of patient awareness. Approximately 2% of the ASA Closed Claims Project was awareness under general anaesthesia5.

In Dr Rowan's graphic and disturbing report6 we read of what it is like to be awake and paralysed while undergoing abdominal surgery. Dr Rowan asks the question why a method of anaesthesia is used which cannot be monitored. The brain is the site of action of general anaesthesia but direct monitoring of this organ was not practically possible until the advent of the bispectral index monitor (BIS). Had BIS monitoring been used in Dr Rowan's case her plight may have been discovered at a much earlier stage before surgery commenced. Indeed, there is an argument for BIS monitoring whenever muscle relaxants are used as part of the anaesthetic technique.

The cost of the BIS unit ($12,500) and the disposable sensors ($25 each) discourages many hospital managements from purchasing these monitors. I remember the same economic argument used for not purchasing pulse oximetry and capnography units in the 1980s until a series of hypoxic anaesthetic incidents happened, some widely publicized in the media. Both are now required monitoring. The legal consequences of inadequate anaesthesia and a more informed and litigious public may well do the same for BIS monitoring.

References

References

1. Liu WHD, Thorp TAS, Graham SG, Aitkenhead AR. Incidence of awareness with recall during general anaesthesia. Anaesthesia 1991; 46:435-437.

2. Ranta SOV, Laurila R, Saario J, Ali-Melkkila T, Hynynen M. Awareness with recall during general anesthesia: incidence and risk factors. Anesth Analg 1998; 86:1084-1089.

3. Cameron AG. Awareness-an old approach. Anaesth Intensive Care 2000; 28:707.

4. Tunstall ME. The reduction of amnesic wakefulness during caesarian section. Anaesthesia 1979; 34:316.

5. Domino KB, Posner KL, Caplan RA, Cheney FW. Awareness during anesthesia: a closed claims analysis. Anesthesiology 1999; 90:1053-1061.

6. Rowan KJ. Awareness under TIVA: a doctor's personal experience. Anaesth Intensive Care 2002; 30:505-506.