Accidental awareness during general anaesthesia happens in roughly one in every 19,000 cases, according to a major new study on this highly feared complication.
This incidence of “waking up” during surgery is much lower than previous estimates, which were as high as 1 in 600, the authors say.
In accidental awareness during general anaesthesia (AAGA), the patient has the feeling of being conscious despite having received general anaesthesia.
Its occurrence can have life-long psychological harm, according to the 5th National Audit Project (NAP5) report from the Royal College of Anaesthetists and the Association of Anaesthetists of Great Britain and Ireland.
” he process of general anaesthesia can and does fail and AAGA can and does arise,” the report notes, and “its long term consequences can be most dreadful,” as is “compellingly” demonstrated in the words of one patient’s account included in the report.
The patient, Sandra, described her feelings when, as a 12-year-old, she suffered an episode of AAGA during a routine orthodontic operation: “Suddenly, I knew something had gone wrong,” she said. “I could hear voices around me, and I realized with horror that I had woken up in the middle of the operation, but couldn’t move a muscle… while they fiddled, I frantically tried to decide whether I was about to die.”
For more than 15 years after the operation Sandra said she had nightmares in which a “Dr. Who style monster leapt on me and paralyzed me.”
The NAP5 panel studied outcomes from all anaesthetics in five countries for a full year, including more than 300 reports of AAGA, “making it a uniquely large and broad project,” Professor Tim Cook, Consultant Anaesthetist, Royal United Hospital, Bath, England, and co-author of the report, commented in a statement.
“The project dramatically increases our understanding of anaesthetic awareness and highlights the range and complexity of patient experiences. NAP5, as the biggest ever study of this complication, has been able to define the nature of the problem and those factors that contribute to it more clearly than ever before,” he added.
The majority of episodes of AAGA they reviewed happened during the dynamic phases of anaesthesia (induction and emergence) and were short-lived ( less than 5 minutes).
But they may be far from benign. Roughly 51% of episodes led to distress and 41% to longer-term psychological harm. Sensations experienced included tugging, stitching, pain, paralysis and choking. Patients described feelings of dissociation, panic, extreme fear, suffocation and dying. Longer-term psychological harm often included features of post-traumatic stress disorder (PTSD).
Professor Jaideep Pandit, NAP5 chair and consultant anaesthetist in Oxford noted in a statement that risk factors were “complex and varied, and included those related to drug type, patient characteristics and organizational variables. However, the most compelling risk factor is the use of muscle relaxants, which prevent the patient moving.”
“The cases of ‘AAGA’ reported to NAP5 were overwhelmingly cases of unintended awareness in patients who were unable to move because of the effects of a neuromuscular blocking drug but who had received inadequate anaesthetic agent to produce loss of consciousness. It is worth reconsidering the problem of AAGA as one of ‘unintended awareness during neuromuscular blockade,'” the report notes.
Patients are at higher risk of experiencing AAGA during caesarean section (1 in 670) and cardiothoracic surgery (1 in 8,600), if they are obese, female, or when there is difficulty managing the airway at the start of anaesthesia, the report says.
“Although brain monitors designed to reduce the risk of awareness have a role with certain types of anaesthetic, the study provides little support for their widespread use,” Dr. Pandit said.
In total, the NAP5 report makes 64 recommendations designed to minimize the incidence of AAGA and, when it occurs, to ensure that it is recognized and managed effectively to mitigate longer-term effects on the patient.
One key recommendation is to use a simple anaesthesia checklist at the start of every operation to confirm (among other things) delivery of adequate anaesthesia. Routine use of a checklist “will help prevent a significant proportion of AAGA cases, namely those arising from a natural ‘gap’ in delivery of anaesthesia during transfer or movement of a patient (notably from anaesthetic room to theatre),” the authors say.
They also encourage a structured approach to the management of patients reporting awareness and creation of an ongoing database of AAGA reports. “All reports of AAGA should be carefully assessed, mapping details of the patient report against the conduct of anaesthetic care,” they advise.